The purpose of the workshop
Analysis of the workshop
As can be seen in Fig. 2, the basis of the production of LPC-2 is made up of a sheet of carbon steel grades, and only a small part is cold and hot-rolled sheets of alloy steel grades.
Consider the dynamics of changes in production volumes over the past 3 years:
2004: Mill 1500 produced 55800 t of sheets of carbon steel grades and 900 t of sheets of stainless steel, Mill 1400 rolled 900 t of sheets of carbon and stainless steel grades;
2005: Mill 1500 produced 54,000 tons of sheets of carbon steel grades and 600 tons of sheets of stainless steel grades, Mill 1400 rolled 800 tons of sheets of carbon and stainless steel grades;
2006: Mill 1500 produced 54,400 tons of sheets of carbon steel grades and 650 tons of sheets of stainless steel grades, Mill 1400 rolled 750 tons of sheets of carbon and stainless steel grades.
The equipment installed in the sheet-rolling shop No. 2 is outdated. The production of hot-rolled and cold-rolled sheets by the workshop began in 1959, on the basis of which we can speak of a high degree of wear of the main and auxiliary equipment.
The main reason for short-term downtime is the breakdown of units in the main auxiliary equipment due to workers' violation of the sheet production technology (breakage of the rollers of the straightening machine, winding of the rolled sheet on the roller of the straightening machine, etc.). Most of these failures, with rare exceptions, lead to mill downtime. Thus, the load factor for the time of mill 1500 is approximately 0.92, for mill 1400 it is 0.54 (according to data for 2006). The low utilization of the 1400 mill is due to low orders for cold rolled alloy steels and alloys.
The number of scrap in the mill 1500 in 2005 amounted to 0.008% of the total production volume, this figure for mill 1400 was 0.002%. In 2006, the number of scrap increased for mill 1500 to 0.012%, for mill 1400 to 0.0024%. These figures indicate a decrease in the quality of products manufactured by sheet-rolling shop No. 2. The main reason for the marriage is the presence of blisters, bubbles, captivity, shells on the finished sheet. The other most common causes of rejects are edge ripple, plate thickness and flatness outside of thickness or flatness tolerances. In addition, there is a high level of scrap when finishing the sheet: rubbing, scratches, improper trimming, removing the sheet or half-roll outside the thickness tolerances, etc.
Speaking about the shortcomings of technology and equipment, it should be noted that it is impossible to obtain hot-rolled sheets with a width of more than 1100 mm at the mill of 1500, while in the rolling industry there is a tendency to increase the width of the obtained sheets. In addition, the working stand of mill 1400 is non-reversible, which creates additional difficulties in the production of cold-rolled sheet (high level of manual labor, during rolling, an electric bridge crane is constantly used to transfer the rolled sheets to the entrance side of the sheet stand).
Based on the analysis of the work of the workshop, the condition of the equipment, it can be concluded that the following measures are necessary:
1. Replacement of the rotary table in front of the working stand of mill 1500 with a section of the roller table with lifting stops, which will allow to pass the workpiece and the slab up to 1250 mm wide;
2. Replacement of RPM11, located on the rolling line of mill 1500, with a straightening machine capable of straightening sheets up to 1250 mm wide;
3. A set of measures for reversing the working stand of mill 1400.
The purpose of the workshop
Sheet-rolling shop No. 2 of JSC AMZ is intended for the production of cold and hot-rolled thin sheets from hard-to-form steel grades. During the existence of the workshop, workers have mastered a large number of steel grades: carbon and structural steels, steels of austenitic-martensitic, ferrite-martensitic, aging and martensitic classes, alloys based on chromium, nickel, titanium, and others. Currently, the main type of products is a sheet of carbon, stainless, heat-resistant and heat-resistant, acid-resistant and special steel grades.
The shop has two rolling mills 1500 and 1400. Mill 1500 is designed for hot rolling of finished sheets with a thickness of 1.6 - 30.0 mm, for the production of rolled stock for a mill 1400 with a thickness of 1.5 - 5.2 mm, for rolling sheets with one-side corrugation thickness 4.0 - 12.0 mm. The maximum width of the obtained sheets is 1020 mm, the maximum length is 2500 mm. In addition, at the request of the customer, sheets and strips of smaller dimensions can be rolled.
Mill 1400 is designed for cold rolling and temper rolling of thin sheets. Thickness of rolled sheets 0.8 - 4.0 mm. Cold rolling is carried out from heat-treated, pickled, graded and cleaned hot-rolled stock or cold-rolled half-roll.
The grades of cold and hot rolled sheets are given in Appendix. one.
Equipment composition and technical characteristics
The layout of the main and auxiliary equipment is shown in the drawing app. 2. In the drawing, the key numbers indicate:
1-ring methodical three-zone furnaces designed for heating billets and slabs before rolling on mill 1500. Furnace diameter on masonry is 10430 mm. The masonry of the vault and hearth of the furnace is made of periclase-chromite bricks. The maximum furnace temperature is 1220 ° C. The furnace rotation speed is 0.4 m / s. The angle of rotation in one period is 30 °. The maximum weight of the bunk is 200 kg. The furnace is served by 2 overhead cranes with a lifting capacity of 10 tons.
2 - machines for planting and dispensing metal from the furnace;
3.5 - feeding roller table, roller table section has a common drive, roller table speed 3 m / s;
4 - rotary table;
6 - reversing mill "Quarto 1500" designed by NKMZ.
The maximum width of rolled sheets is 1050 mm, the maximum length is 2500 mm.
The dimensions of the rolls are given in table. one.
Table 1 - Roll sizes
Two-layer cast iron work rolls with a bleached layer, Shore hardness not less than 70 units. Work rolls made of steel grades 9ХФ, 75ХНМ with a Shore hardness of at least 45 units. Work and backup rolls are mounted in rolling bearings. The maximum pressure on the rolls is 22.5 MN.
The work rolls are driven from the PM 2600-40 engine through a gear stand and universal spindles. Electric motor power 1900 kW, rotor speed 0 - 40 - 80 rpm. The maximum allowable torque is 0.9 MN * m.
The balancing of the upper backup and working rolls is hydraulic with a working oil pressure in the cylinders of 9.8 MPa.
Drive of the pressure screws from two 45 kW DC motors through two globoid gearboxes with a total gear ratio of 44. Working travel of the pressure screws 75 mm, maximum travel 150 mm. To control the set gap between the work rolls, the mill is equipped with a roll gap indicator. Closed cage.
The mill is equipped with an installation for the preparation and use of technological lubrication in the mill during rolling. To align the slab and billet before rolling, the mill is equipped with leveling rulers. The mill is serviced by a crane with a lifting capacity of 75 tons;
7 - eleven roller straightening machine. The diameter of the straightening rollers of the machine is 180 mm, the material of the rollers is steel 9X, the thickness of the sheets being straightened is from 2.0 to 11.0 mm, the straightening speed is 1.5 m / s, the recommended yield strength of the metal of the sheets being straightened is up to 480 N / mm 2. A straightening device is located in front of the straightening machine;
8 - guillotine shears for cutting the front and rear ends of the rolled sheets. Shears drive motor power 40 kW. Engine speed 90 rpm. The maximum pressure of the metal on the knife is 100 tons. The number of cuts per minute is 10. The maximum thickness of cut sheets is 18 mm. Tilt angle of the upper knife 3.5 - 10.0 °;
9 - stacker of rolled sheets equipped with a roll-out cart;
10 - hydraulic shears for cutting the share blank. The maximum oil pressure in the hydraulic cylinder is 20 MPa. Knife length 550 mm. The maximum thickness of the workpiece to be cut is 22 mm. Maximum workpiece width 400 mm;
11 - transport trolleys for metal transfer between spans and between mills with a carrying capacity of 10 tons. Travel speed 15.3 m / min;
12 - chamber electric furnaces SDO - 14.20.10 / 12-8Л1, located in the module of the "1500" mill, rolled stocks, half-rolls, finished cold-rolled and hot-rolled sheets of carbon structural steel grades are subjected to heat treatment.
The main characteristics of the furnace:
Working space length, mm - 2706;
Working space width, mm - 1400;
Height, mm - 1042.
Outside dimensions of the furnace: _,
Length, mm-7 4200. Length with extended hearth, mm - 9700;
Width, mm - 2830;
Height, mm - 3 130;
Vault and wall masonry - fireclay ШБ;
Maximum heating temperature, ° С - 800-1200;
Maximum cage weight, t - 7.5;
The number of electrical zones - 3;
Thermocouples, pcs-3;
Transformers, type - TOT - 100/155 PCs;
Installed capacity of the furnace, kW - 210;
Supply voltage, Volt - 380.
13 - continuous roller oven. Furnace dimensions:
The length of the oven on the masonry is 19000 mm;
The width of the oven on the masonry is 2320 mm;
Working space width 1392 mm;
The height of the arch from the rollers is 1830 mm.
Roller hearth speed 0.01 - 0.8 m / s. Water-cooled rollers made of heat-resistant steel grade 20X25H20S2. Active hearth area 26.5 m 2. The maximum temperature in the furnace is 1200 ° C. The furnace has 34 low pressure gas burners GNP-4AP. Behind the furnace there is a sprinkler with water spray nozzles with dimensions:
Length 5250 mm;
Width 1400 mm;
Height 1520 mm.
A stacker is located in front of the oven. The sheets are gripped by means of two vacuum suction cups mounted on a mechanized traverse that descends at a speed of 0.8 m / s. Loading capacity of the device is 200 kg. The maximum stack height of sheets is 600 mm. Maximum sheet weight 190 kg. Cycle time 10 s. The span equipment is serviced by two electric overhead cranes with a lifting capacity of 10 tons;
14 - seventeen-roll straightening machine. Roller diameter 75 mm, dressing speed 1.5 m / s;
15 is a one-roll car. The diameter of the rollers is 180 mm, the power of the electric motor is 130 kW, the dressing speed is 1.5 m / s;
16 - furnace for molten salt production. Alkaline melt baths 2 pcs. located in the combustion chambers of furnaces heated with fuel oil. Combustion chamber dimensions:
Length 3.1 m;
Width 1.5 m;
Height 3.2 m.
The mass of the finished melt in the baths is 25 tons.
17 - washing baths 3 pcs., Dimensions 3.3 x 1.2 x 2.3 m.
18 - acid metal baths with acid-resistant insulation 8 pcs. dimensions 3.3 x 1.2 x 2.3 m. Working volume 8 m 3. The thickness of the rubber layer is 12 mm. thickness of masonry made of acid-resistant bricks with diabase grease 190 mm. Baths are equipped with a swing mechanism;
19 - drying and washing machine. Engine power 79.1 kW. The diameter of the rollers is 200 mm. The length of the roller barrel is 1300 mm. Sheet movement speed 0.3 m / s. Water consumption 1.0 m 3 / h. Water temperature ~ 95 ° C. The sheet dispenser in front of the dryer and washing machine captures sheets using 3 vacuum suction cups. lowering speed of the mechanized traverse 0.8 m / s. Loading capacity of the device is 200 kg. The maximum stack height of sheets is 600 mm. Maximum sheet weight 180 kg. The cycle time of the device is 10 s. After washing, the sheets are stacked using pneumatic cylinders. Table lifting capacity 10 tons. Pickling department and drying-washing machine serve 2 electric bridge cranes with lifting capacity 10 tons;
20 - non-reversible mill quarto 1400. The dimensions of the rolls are given in table. 2.
The weight of the work roll is 1.82 tons, the support roll is 21.45 tons. The back-up rolls are made of steel grades 9HF or 75HMF with a hardness of 45 - 69 Shore units. Work rolls made of steel 9X2 with a hardness of 95 - 105 Shore. The work rolls are driven by a 630 kW asynchronous motor through a differential gear. The balancing of the backup and work rolls is hydraulic, the pressure device is electric. The mill is equipped with a work roll anti-bending system with the following characteristics:
table 2
Roll sizes
Oil pressure in the system is 9.8 MPa;
Diameter of the working part of the cylinder 130 mm;
Number of cylinders 8 pcs .;
The maximum spreading force is 140 tons.
Setting device with one vacuum suction cup, carrying capacity 100 kg. Thickness of rolled sheets 0.8 - 4.0 mm. Rolling speed 1.0 m / s. The difference in diameters of paired work rolls is allowed up to 3 mm. maximum metal pressure on rolls 2000 t. Maximum torque 22 t * m. The mill is serviced by two electric bridge cranes with a lifting capacity of 50 tons;
21 - twenty-one-roll straightening machine. The diameter of the straightening rollers is 60 mm. The thickness of the sheets to be straightened is 0.8 - 3.0 mm.
22, 23 - guillotine shears. Engine power 40 kW. Engine speed 90 rpm. The maximum thickness of the cut sheets is 11 mm. The angle of inclination of the upper knife is 3.5 - 10.0 °. The number of cuts per minute 10;
24 - straightening and stretching machine. Maximum tensile force 90 t. Stretched sheets thickness up to 2 mm. Possible tensile elongation up to 3%. The length of the stretched sheet is from 1420 to 2000 mm. Head working speed 6 mm / s. Conveyor speed from 0.075 to 1.3 m / s. The spreader travel speed is 9 m / s. Spreader stroke length 3 m. Working plunger diameter 250 mm. Working pressure 200 kg / cm 2. Recommended yield strength of sheet metal to be straightened is up to 480 N / mm 2.
25 - a bell-type electric furnace No. 768360 was installed for heat treatment of sheet bags in a protective gas environment. Furnace characteristics:
The size of metal packages is 1100x2500x250 mm;
The total weight of the cage is 20 t;
Furnace atmosphere H 2 up to 1%, CH 4 up to 1%, CO-0.1-0.3%, N 2 base;
Shielding gas consumption up to 20 m 3 / h;
Heating means - resistance electric heaters made of Kh23Yu5T alloys;
Processing temperature up to 900 ° С;
Installed capacity 100 kW;
The performance of the circulating fan is 20000 m 3 / h;
Fan head 1800 Pa;
Electric motor power 22 kW;
Number of stands 2 pcs.
For the production of protective endogas, two EN-125 M2 endogenerators are installed.
The characteristics of the shielding gas are given in table. 3.
Table 3 - Characteristics of the shielding gas installation
Benefits
By connecting coils of steel strip before they are fed into the mill, the continuous tandem cold rolling mill has the following advantages:
- High performance
- Optimized yield
- Reduced roll consumption
- Manufacturing flexibility
- Close tolerances for strip thickness, profile and surface quality
- Low operating, maintenance and downtime costs
- Small number of operators
- Small amount of material outside tolerances
- Lack of problems associated with refueling the strip
Features:
The tandem mill includes from three to six rolling stands, arranged in series, for gradual reduction of the strip in thickness in one pass. At the end of the inlet section of the continuous tandem mill line, a welding unit and a strip accumulator are installed for sequentially connecting coils of pickled hot-rolled strip. Together with an integrated automation system, this forms a powerful and highly productive mill, which ensures a high level of product quality and a stable production process. The mill provides high production efficiency and is used to produce a wide range of steels, from general structural steels to high quality steels for automotive panels and more.
Increasingly, automotive steels require thin metal with high tensile strength in order not to add weight to the vehicle and therefore improve fuel consumption. For this reason, rolling mills are required to increase productivity and improve product quality. To solve this problem, a standard was developed, according to which a continuous 5-stand tandem cold rolling mill, which uses 6-roll rolling stands with universal profile control, was combined with a pickling line.
Features of the rolling mill with universal profile control:
- Work roll bending
- Intermediate roll bending
- Shifting intermediate rolls
- High reduction ratio
- Precise control of the strip profile
- Stability of operation
- Reduced roll reserve
- Increase in yield (by reducing the thinning of the strip edge)
To cope with the high discharge rate of the rolled strip, a carousel-type coiler is used which coils the strip as it leaves the rolling mill. The winder has two drums. This allows the strip to be trimmed at the end of coiling and also allows the next strip to be wound onto the second reel without stopping the mill.
Productivity and product quality are highly dependent on the quality of automation, process control and available process optimization functions.
To maximize plant productivity, Primetals Technologies offers additional tailor-made optimization solutions to further improve production efficiency and strip quality beyond a standardized high-performance automation system.
Maximizing throughput with:
- OGO - Out-of-Range Optimization for Integrated Rolling Process
- Adaptation and customization based on a neural network, guaranteeing high product flexibility and easy expansion for the production of new materials.
- Optimized weld bead rolling for flexible production and minimal deviation
Pickling of rolled stock for the production of sheet metal is carried out in NTA, similar to those operating in cold rolling shops, described in detail in Chapter 2.
For rolling of tin, five- or six-stand NSHP are used. In rare cases with small production volumes - reversing mills.
Rolling tin
As already noted, the first in the USSR sheet metal workshop with a continuous mill was the sheet metal workshop of OJSC MMK. The workshop is still in operation. Both equipment and technology have improved. To date, the tin shop of OJSC MMK has an NTA, a five-stand NSKhP-1200, units for degreasing and strip cleaning, bell-type furnaces and ANO, two-stand tempering mills and units for electrolytic and hot tinning of the strip, as well as units for transverse cutting and straightening of strips and stacking sheets in bundles ...
There is also a unit for continuous hot-dip galvanizing of strips from cold rolling mills.
A diagram of the 1200 mill is shown in Fig. 128. The mill is designed for rolling sheet metal with a thickness of 0.20-0.36, a width of 730-850 mm, as well as cold-rolled strips of low-carbon steel with a thickness of 0.35-0.63, a width of 730-900 mm from rolled stock with a thickness of 2.1-2, 5 mm.
The mill consists of five four-high stands in series, an decoiler and a coiler. Stands of closed stands. Diameter of work rolls is 500, support rolls are 1340 mm. Roll barrel length 1200 mm. The bearings of the work rolls are roller bearings, the bearings are of fluid friction. The rolls are driven by an engine through a gear stand. The characteristics of the motors are given in table 48.
The technological process of rolling on the 1200 mill is as follows.
The rolling of the front end of the rolled stock until it is securely gripped by the coiler is carried out at a filling speed. In this case, water is supplied to the work and backup rolls. Further, the rolling speed is increased to working speed and the process lubricant supply system is switched on. The reduction mode and the rolling speed on the 1200 mill are given in Table 49.
Figure: 128. Layout of the main equipment of mill 1200 of OJSC MMK:
1-5 - working stands; 6 - decoiler; 7 - winder; 8 - tensometric rollers for measuring strip tension; 9 - nozzles for supplying technological lubricant to the strip: 10 - contactless gauge of strip thickness
Table 48
Characteristics of electric motors of stands of mill 1200 of OJSC MMK
|
Power, MW |
Angular speed, rpm |
Rolling speed, |
||
| 2 | ||||
| 3 | ||||
Table 49
The use of relatively small reductions of the strip in the 1st stand is due to the fear of ruptures due to the longitudinal difference in thickness of the joined ends, as well as insufficient stability of the strip (displacement from the longitudinal rolling line). The decrease in the size of the strip reduction in the last stand is explained by the fact that at higher reductions, the friction in the deformation zone increases due to poor lubricant supply. Because of this, the temperature of the metal in the deformation zone rises, the strip buckles, and the metal particles may peel off.
Palm oil is most often used as a technological lubricant for rolling sheet metal.
For a long time, the following lubrication system was used at the 1200 mill of OJSC MMK: the first stand received a strip oiled with palm oil on a NTA after pickling the rolled stock. Prior to subsequent stands, palm oil with water was fed, respectively, with one, two, four and seven nozzles on each side of the strip.
Later on, the 1200 mill tested the use of castor, hydrogenated sunflower and coriander oil. The best results (reduction of the friction coefficient in the last stands, power consumption and metal resistance to deformation) were obtained when using castor oil. The main disadvantage - after rolling, the surface of the sheet was dark, greasy and poorly cleaned. A similar result was obtained with other natural oils.
In order to reduce costs, work began on the use of palm oil substitutes. Positive results were obtained, but the price of substitutes was higher than the price of palm oil. The work was continued in the direction of the application of additives to palm oil. The goal is to improve the quality of tinplate, reduce costs, expand the range of tinplate thickness. Studies have shown that the use of 10-20% additives to palm oil makes it possible to roll sheet metal with a thickness of 0.15-0.18 × 730; 0.18 × 780 and 0.28 × 920 mm, the contamination of the strip after rolling and the degree of cleaning on the degreasing units are approximately at the same level as when using palm oil.
Other work is underway to improve the tin plate production technology at OJSC MMK.
Six-stand mills should be considered modern mills for rolling sheet metal. Such a mill, in particular, is the 1400 mill of ISPAT-Karmet OJSC.
Mill 1400 is designed for rolling sheet metal and thin strips of steel grades 08kp, Yukp, 08ps. On the mill, endless (main) or roll-to-roll modes of rolling are possible. The layout of the main equipment of herd 1400 is shown in Fig. 129.
Technical characteristics of the mill 1400 of JSC "ISPAT-Karmet"
Trolley dimensions, mm:
thickness…………………………………………. 1.8-3
Roll diameter, mm ……………………… 750 / 1500-2200
Coil weight, t ………………………………… ..<30
Dimensions of finished strips, mm:
thickness………………………………………. 0.16-0.60
width ……………………………………… .. 700-1250
Rolling speed, m / s:
filling station …………………………………… .. 0.75
maximum ………………………………… .. 33
during the passage of the welded seam ……………… ..<16
when cutting the strip and threading the end
strips into the coiler …………………………. 2-8
Rolling speed change rate, m / s:
when accelerating …………………………………. 2.5
at deceleration ……………………… 4 ………. 3
Roll barrel diameters, mm:
workers ………………………………………… .. 600
support ………………………………………… 1400
Roll barrel length, mm ……………………… 1400
Cross-section of bed racks, mm ………………. 705 × 800
Maximum rolling force, MN ………… 20
Pressure device: diameter of the pressure screw, mm 56O
screw stroke, mm …………………………………… .. 170
screw travel speed, mm / min ... 26.4-50
diameter of the GNU piston, mm ……………………. 750
piston stroke, mm ………………………………… 20
Liquid pressure. Pa …………………… .. 314.8-105
Design capacity, thousand tons / year …………… 750
At the head of the mill there is a loading conveyor (not shown in Fig. 129), on which three coils can be placed. The loading conveyor ensures the transfer of the bales to the loading carriage. It is designed as a beam with places for rolls. Behind the loading conveyor, there is a mechanism for removing the strapping tape and a loading device containing a cart for receiving rolls and transferring them to unwinder
Uncoilers ensure that the rolls are strictly centered over and tension is created during the unwinding process. Each unwinder is equipped with a bending mechanism (scraper type) and feeding the front end of the strip into the mill. The front end of the strip is separated from the roll by means of a bending device, which also directs the strip to a flattening machine; in the flattening machine, the front and rear ends of the strip are straightened before butt welding (not shown in Fig. 129).
In a butt-welding machine, the ends of the strips are welded (with a section of 1.2-5-6 × 600 + 1350 mm) and the burr is removed. Behind the butt-welding machine there is a tensioning device No. 1, consisting of three drive rollers with a diameter of 1 000 mm with an individual drive and two pressure rollers. This device provides strip tension during end welding and in front of the loop storage.
Figure: 129. Layout of the main equipment of the endless rolling mill 1400 of OJSC ISPAT-Karmet:
1 - decoilers # 1 and # 2; 2 - pulling rollers; 3 - butt-welding machine; 4 - tensioner No. 1; 5 - guide rollers; 6- loop device; 7 - drum; 8 - swivel rollers; 9 - tensioner No. 2; 10 - tensioner No. 3; 11 - loop hole; 12 - decoiler No. 3; 13 - guillotine shears; 14 - correct-pulling machine; 15 - continuous group of working stands; 16 - wiring tables; 17-strip tension meter; 18 - strip thickness gauge; 19 - tension rollers; 20 - flying scissors; 21 - winders
The looping device (strip stock 417 m) contains a bogie with two non-driven rollers, a drum connected by a rope to the bogie, as well as swivel rollers supporting the strip branches. The speed of movement of the cart during accumulation and consumption of the strip does not exceed 1.25 m / s, and its working stroke is 105 m. The inlet part of the mill line includes tensioning devices No. 2 and 3, similar in design to loop device No. 1, separated by a loop pit. The loop hole between the tensioning devices No. 2 and 3, in which the strip is transported without tension, allows the tension decoupling of the head and inlet parts of the endless rolling mill. Uncoiler No. 3 and a straightening-pulling machine are installed in front of a six-stand mill 1400. Uncoiler No. 3 of cantilever type has a scraper unfolder of the front end of the strip, a pressure roller for pressing down the fluffed turns of the coils at the moment of bending the front end of the strip. Decoiler no. 3 is used in the case of strip rolling. Between the straightening-pulling machine and the first stand of the mill, there are hydraulically driven guillotine shears for cutting the strip when handling the work rolls and backup rolls and cutting, if necessary, welds.
Six identical four-high stands are installed in the mill line. All stands of the 1400 six-stand mill are equipped with a combined pushing mechanism, which includes an electromechanical pushing device with a drive of pushing screws from electric motors for setting the roll gap and a hydraulic pushing device (HPU) consisting of two hydraulic cylinders located under the chocks of the lower backup rolls and serving to regulate the rolling force. GNU provides high speed and accuracy of rolls movement when adjusting the thickness, and electromechanical devices are used when setting up stands, rebuilding them to a new size of strips and when handling rolls.
The back-up rolls of the 1400 six-stand mill are installed in hydrostatodynamic fluid-friction bearings (PZhT) with a thrust rolling unit, the work rolls are mounted on rolling bearings.
In order to control the flatness of the strip, all stands of the six-stand mill
1400 are equipped with devices for additional bending and anti-bending of the work rolls. Additional bend hydraulic cylinders are installed in the back-up roll pads and are designed to eliminate the warping of the sheet metal. Elimination of waviness of the strips is achieved with the help of anti-bending hydraulic cylinders placed in the bed plate.
Press-guide tables are installed in the inter-stand spaces to release the rear end of the strip with tension and prevent the shackle of the rolls.
The output part of the mill provides winding of rolled coils, their transportation from the mill, and inspection of the strip surface quality. A tensioning station is installed behind the last stand of the mill, which consists of four individually driven rollers with a diameter of 570-600 mm and four pressure rollers equipped with hydraulic cylinders. This take-up station maintains the front tension in the last flare while cutting the strip and threading the front end onto the reel drum. The strip is cut with flying drum shears to divide the strip after winding the roll.
Two coilers of a similar design are installed behind the shears in the course of rolling. The coilers have a drum, a mechanism for changing the diameter of the drum, a bale jumper, a pressure roller and an automatic overflow.
The reel drum is a forged wedge-shaped shaft on which four movable segments are mounted, connected with a mechanism for changing the drum diameter to secure the roll and ensure its removal. A pinch roller is installed to press the rear end of the strip against the roll and prevent the roll from loosening. The automatic overlapping device allows threading the front end of the strip onto the reel drum and winding the first turns.
On the first generation NSHP, the front end of the strip was tucked into the slot of the reel drum. However, when a thin strip (up to 0.3 mm) is wound onto a drum with a high tension, longitudinal dents are formed on the first inner turns of the coil at the location of the slot on the reel drum. In order to avoid the formation of dents on the inner turns of the rolls, it is necessary that the gap on the reel drum is minimal. However, it is very difficult to tuck a thin steel strip into such a gap. In addition, the threading operation at the end of the strip is time-consuming and sometimes involves a worker. In this regard, belt-type automatic overflowers have been developed. They allow the first 2-3 turns of the strip to be tightly wound on the reel drum, after which, in the presence of a certain strip tension, the coil is wound tightly.
On the first generation NSKhP, the front end of the strip was tucked into the slot of the coiler. However, when winding a thin strip (up to 3 mm) onto the drum with high tension on the first inner turns of the coil, longitudinal dents are formed at the location of the slot on the reel drum, to avoid the formation of dents on the inner turns of the coils, the gap on the reel drum must be minimal. However, it is very difficult to tuck a thin steel strip into such a gap. In addition, the threading operation at the end of the strip is time-consuming and sometimes involves a worker. In this regard, belt-type automatic gouchers have been developed. They allow the first 2-3 turns of the strip to be tightly wound on the reel drum, after which, if a certain strip tension is present, the coil is wound tightly.
Before threading the front end of the strip, the carriage moves to the rotating reel drum (the strip capture scheme is shown in the fragment located on the right side of the figure). In this case, the tensioned belt will bend the reel drum and the front end of the strip will enter the throat between the belt moving along the 6n8 idle rollers and the rotating drum. At the same time the roller 7 will lower with the help of the pneumatic cylinder 11 and the lever and press the young man of the strip against the reel drum. Thus, 2-3 turns are formed on the reel drum, after which the cart is retracted and the strip is tightly wound into a roll.
Figure: 130. The design of the automatic belt overlap of the front end of the strip around the reel drum:
K 10, 11 - pneumatic cylinders; 2 - mobile cart; 3 - guides; 4 - S-shaped frame; 5 - endless belt; 6,7,8 - idle rollers; 9 - articulated arm; 12 - reel drum
Mill 1400 is equipped with an ACS TTT connected with local automatic control systems. To control the progress of the technological process and the operation of individual devices and mechanisms, sensors are installed in the mill line, the information from which is sent to the control computer (CFM). The mill is controlled from a central control station (CPUS) and work stations near the stands. In the central control unit, the rolling program is set, the mill mechanisms and technological systems are controlled in automatic and semi-automatic modes, the mill is controlled in all speed modes, the local systems are controlled, the technological parameters of the mill and electrical parameters of the main drive are monitored, the strip stock in the accumulator loop is controlled, and the mill is controlled. with the help of UVM in all provided modes. Control stations on the stands provide for control of mill speed modes, control of pressure screws, roll setting mechanisms, centering rollers, guide table and other service devices.
At the time of the commissioning of the 1400 mill, there was no domestic experience in operating six-stand cold rolling and super-thin sheet rolling mills.
The tackle, which was received at the ShSGP-1700 for the NSKhP-1700, in many respects did not meet the requirements for the roll-up for tin: the transverse profile was unstable, its convexity and wedge shape exceeded the required one, and the mechanical properties were also unstable: yield point 240-340 N / mm2 , hardness 48-75 HRB.
The initial choice of the thickness of the rolled stock (1.8-2.2 mm) did not justify itself either, since there was a wide scatter of mechanical properties and high unevenness of the metal structure with low plastic characteristics and increased hardness of the rolled stock.
The main measures for obtaining rolled stock of optimal shape, mechanical properties, hardness and metal structure were the following:
Development of new roll profiling (see section 3 of this chapter);
Regulation of temperature conditions for rolling and rolling of rolled stock into a roll (860-890 and 660-680 ° C, respectively);
- the use of a slide with a thickness of 2.4 mm
- holding the rolls before etching for at least 72 hours;
- relative deformation of the roll in the bending machine NTA 0.7-1.5%.
On the 1400 mill itself, the main task was to develop rational reduction modes.
In the initial period of mastering the rolling of tin, the regimes were used in which the reduction of the metal was carried out in five stands (according to the experience of mill 1200), and the sixth stand worked in a rolling-tempering mode (Table 50).
The process of rolling strips with small reductions in stand 6 had a number of disadvantages. First, the absence of reduction in the stand did not allow adjusting the strip thickness by changing the speed only in stand B due to the low transfer ratio Ah6 / AV6. Therefore, the thickness control was carried out by synchronously changing the rolling speeds in stands 5 and 6. The tension of the strip between these stands was kept constant by adjusting the speed in stand 6. With such a scheme, it was difficult to control the thickness of the rolled strips due to the large transport lag. Secondly, rolling in stand 5 of a thin, practically finite strip thickness increased the probability of its break in the last inter-stand gap. The likelihood of strip breakage also increased due to the fact that, with the specified distribution of reductions, maintaining a given tension between stands 4 and 5 by moving the screws of stand 5 introduced significant disturbances in the tension between stands 5 and 6.
The difference in the dynamic loading of the drives of stands 5 and 6 also had a negative effect on the stability of the rolling process under the conditions under consideration, which in the modes of acceleration and deceleration of the mill led to a change in the strip tension in the last inter-stand gap. Finally, the lack of sufficient reduction in the stand 6 reduced the efficiency of controlling the shape of the rolled strip. Insufficient heating of the stand rolls and the small value of the temperature difference along the length of the roll barrel made it difficult to thermally regulate its profile. The limited possibility of redistribution of the extracts along the strip width at low reduction made it difficult to control the strip shape by forced bending of the rolls.
Table 50
Compression mode and power parameters for rolling sheet metal with dimensions 0.25 + 0.32 × 850 mm from rolled stock 2.4 mm thick
|
Cage number |
Compression ratio,% |
Rolling force, MN |
Front strip tension, kN |
Main motor current led, kA |
Attempts to increase the reduction in stand b by readjusting the mill during rolling did not give the expected result due to a sharp increase in the rolling force and strip tension. It was possible to optimize the load of the stand when rolling sheet 0.25 mm thick only when it was initially adjusted to a sufficiently large reduction.
The next stage in the development of reduction modes is characterized by the commissioning of the 6th stand of the 1400 mill. Table 51 shows the reduction modes during rolling of sheet and cold-rolled strips of various sizes, recorded by Donniichermet's employees during the development of new roll profiling. The inter-stand tensions of the strips that took place during these rolling are given in Table 52.
The compression modes presented in Table 51 are interesting in that they used a roll of different thickness - from 1.8 to 2.5 mm.
Comparison of the data in Tables 50 and 51 shows that the value of the relative reduction in stand b was 11-17%, except for the rolling mode of sheet metal with a thickness of 0.18 mm, which was realized due to unloading of stand 5. The remaining four stands are loaded approximately evenly in terms of relative reduction.
The value of inter-stand tensions is accepted, in comparison with Table 50, slightly higher, but the tendency to decrease them from stand 1 to stand 6 is preserved. Moreover, with an increase in the width of the strips, it increases.
It should be noted that these reduction modes also turned out to be irrational, mainly due to insufficient loading of stand b, which did not exclude difficulties in regulating the thermal profile of the rolls and the shape of the strip.
Subsequently, the strip reduction modes were developed and mastered, presented in Table 53.
A characteristic feature of the mastered reduction modes is that in stand I the value of the relative reduction is somewhat lower than in the other stands. In stands 2-5, the relative reductions are the same, and in stand 6, they are higher, especially when rolling thin sheet metal.
When rolling strips with a uniform distribution of relative reductions in the stands and increased relative reductions in stand 6, the efficiency of the systems for regulating the thickness, tension and flatness of the strip significantly increased, which made it possible to return to the traditional scheme of strip tension in the last inter-stand gap by means of pressure devices in stand 6. reduce the number of strip gusts by more than 5 times.
Table 52
Inter-stand tensions when rolling sheet and cold-rolled strips on a mill 1400
|
Stripes, mm |
Inter-stand tension, kN, at intervals |
||||
Note. The inter-stand tensions are given for the rolling conditions of the strips in the regimes given in Table 51,
Subsequently, the compression modes were somewhat adjusted in accordance with the already established ratios. These modes are presented in Table 54.
When developing rolling modes on the 1400 mill, great attention was paid to the selection of the optimal values \u200b\u200bof the inter-stand tension of the strips.
The tension of the strip contributes to the achievement of uniform deformation of the metal in the roll gap, the centering of the strip relative to the rolling axis, and a decrease in the rolling force. It is used as a control action in systems for fine control of strip thickness. Without a sufficient value of the inter-stand tension of the strip, the process of continuous rolling is practically impossible. As you know, the higher the level of inter-stand tensions, the more dynamically stable the electromechanical mill-strip system is. However, an excessively high level of inter-stand tensions can cause breaks in the rolled strips and slip of the rolls of individual stands relative to the strip. Therefore, the choice of a rational level of inter-stand tension is the most important technological task of optimizing the process of continuous rolling of sheet metal.
Table 53
The mastered regimes of reduction when rolling sheet metal on NSKhP 1400 with a rolled stock thickness of 2.4 mm
|
Cage number |
Compression ratio,% |
Rolling force, MN |
Front strip tension, kN |
Main drive motors current, kA |
|
Tinplate 0.18-0.22 mm thick |
||||
|
Tinplate 0.25-0.36 mm thick |
||||
Table 54
Compression modes when rolling sheet on NSKhP-1400
Experiments have shown that a stable rolling process is possible at inter-stand tensions of 80-90 N / mm. At lower tension values, the rolling process becomes unstable.
Until the end of the 70s in domestic practice, it was assumed that the specific tension on continuous cold rolling mills was assumed to be equal to (0.3-0.4) of has a positive effect on the flatness of the finished sheet. However, as the tension increases, the likelihood of strip gusts also increases.
However, studies carried out in recent years have shown that when rolling low-carbon steel strips, the tension level should be reduced. So, a decrease in inter-stand tensions from (0.35-0.4) st to (0.26-0.3) stt \u200b\u200ballows to reduce the number of stripes gusts by 25%,
The tension level is reduced from the first intercellular space to the last. The comparatively high tension behind the first mill stand contributes to intensive smoothing of the initial thickness variation of the rolled stock. In the last inter-stand gap, where the plasticity of the metal is largely exhausted, and the risk of strip breakage is high, the level of inter-stand tension is set to a minimum. Therefore, on a five-stand mill 1200 of OJSC MMK, the tension of the strip behind the first stand is set equal to 0.2ot, and in the last inter-stand gap, 0.16at.
With an increase in the width of the strips, the value of the specific inter-stand tension also decreases... Such a regularity in the mill tuning modes should be considered positive, since with an increase in width, as a rule, the non-flatness and thickness variation of the strips increase, and, consequently, the uneven distribution of specific tensions along their width increases, which increases the risk of their breaking. A decrease in the average level of specific inter-stand tensions under these conditions increases the reliability of the rolling process.
With an increase in the thickness of the rolling stock, the total inter-stand tension on the mill increases. The ratio of the value of the specific inter-stand tensions to the value of the yield stress of the deformed metal in the corresponding inter-stand gaps is kept at approximately the same level.
The stresses arising in cold-rolled sheet coils after removing them from the coiler significantly affect the quality of sheet products, since they can cause a loss of stability of the inner coils and the formation of a defect such as "birdie", "telescopic", "subsidence" and lead to welding of the contacting turns of the strip during the subsequent heat treatment of the metal and the formation of defects "fracture" and "welding". An increase in the mass of coils to 45-60 tons and a decrease in the thickness of the sheet in modern cold rolling mills increase the likelihood of these defects.
Hence it follows that the choice of the winding mode (the magnitude and nature of the change in tension, temperature, etc.) of the strips into coils after rolling determines both the quality of the sheet and the efficiency of the winding equipment. The traditional method of winding coils on coilers with a constant strip tension is acceptable only in cases where, according to production conditions, there is no danger of loss of coil stability and welding of the turns during subsequent annealing.
To prevent the loss of stability of the inner turns of the coil when it is removed from the drum, the winding method is used, in which 5-10 turns are wound with an increased tension (for carbon steels, 2-5 times higher than the technologically necessary one), followed by a gradual decrease in tension to the technological one after 50-100 turns of the winder.
The selected rolling conditions must correspond to the high-speed rolling conditions. The nature of the speed conditions for rolling sheet metal is similar to the speed conditions for rolling cold-rolled strips and sheets (see Chapter 4). The front end is rolled at the filling speed, after it is securely gripped into the coiler, the speed is increased to the working value. When passing through the mill of the strip with a section of the weld, as well as when the rear end of the strip leaves the mill, the speed is reduced (see Fig. 85).
A change in the rolling speed is characterized by the instability of all technological modes: the friction coefficient, strip thickness, tension, elastic deformation of the stand elements, roll temperature, etc. change. Therefore, endless cold rolling mills provide a higher quality of metal due to a stable speed along the length of the strips. The change in speed during rolling in an endless mode is carried out when switching to another profile size of sheet metal, as well as when rolling seams, therefore, the more reliable the welding technology is developed, the less the decrease in speed or its complete absence.
Figure: 131. Distribution of the possible range of strip rolling speeds in the stands of mill 1400
The maximum rolling speed of the 1200 mill of OJSC MMK is 28 m / s (along the last stand), of the 1400 KarMK mill - 33 m / s. Fig. 131 shows the possible range of strip rolling speeds in the stands of the 1400 mill.
The smoothly expanding range of roll speeds from the first to the last stand (see Fig. 131) ensures flexible operation of the mill and allows rolling with increased reductions in the last stand.
On six-stand NSHP abroad the rolling speed reaches 46 m / s.
| Introduction |
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| Characteristics of sheet rolling shops |
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| Brief description of LPC No. 1 |
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| Brief description of LPC No. 2 |
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| Brief description of LPC No. 3 |
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| Brief description of TsGTSA (LPC No. 4) |
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| Strip rolling technology on the 1400 six-stand mill |
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| Brief technical characteristics of the main technological equipment of the six-stand mill "1400" |
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| Requirements for the rolling stock for a six-stand mill "1400" |
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| Requirements for rental of a six-stand mill "1400" |
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| Preparing the mill for work and setting it up |
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| Roll to mill task |
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| Rolling strips on the mill |
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| Mill management |
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| Operation of technological lubrication during rolling |
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| Operation of rolls, their handling and cooling |
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| Process control. Sensors and process control devices |
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| Rolling safety |
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| Labor protection during rolling |
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| Conclusion |
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Introduction
Karaganda Metallurgical Plant, and now "ArcelorMittal Temirtau", is one of the five largest enterprises of the metallurgical complex of the CIS countries, specializing in the production of sheet metal.
July 3, 1960 is considered his date of birth. On this day, blast furnace No. 1 produced the first pig iron. Over the years, the plant has turned into a powerful modern enterprise with a full metallurgical cycle, producing pig iron, steel, rolled products of a wide range and purpose, as well as coke products and raw materials for the construction industry.
The precondition for the further development of the plant was the favorable economic and geographical location, i.e. the presence of coking coals of the Karaganda basin, closely located deposits of iron and manganese ores in Central and Eastern Kazakhstan, as well as promising regions for the sale of metal structures.
Throughout its half-century history, the plant has been constantly growing and developing, putting into operation new production facilities, expanding the range of products.
In 1964, a complex of large-capacity open-hearth furnaces No. 1 and No. 2 was put into operation. The first melt was produced. March 25, 1966 - slabbing "1150" (swaging shop) was put into operation, and on January 9, 1968 - hot rolling mill "1700" (LPC-1) was put into operation. Later, a 250-ton converter was put into operation, and in 1973 and 1983, a cold rolling shop (Rolling Shop - 2) and the first stage of a tin shop (Rolling Shop - 3). In 1998, a hot-dip galvanizing and aluminizing shop was put into operation, by May 2002, the second continuous hot-dip galvanizing line was completed and put into operation as part of the CGCA. January 18, 2005 - the first CCM line was launched, the first continuously cast slab was produced. November 3, 2005 - a line for the production of painted steel was launched.
In 1995, the Karaganda Metallurgical Plant became part of the LNM Group (since December 2004, the Mittal Steel Company) and is registered as the ISPAT KARMET Joint Stock Company. Later, part of the mines of the Karaganda coal basin were also included in ISPAT KARMET JSC, with the formation of the coal department of ISPAT KARMET JSC and CHPP - 2. In December 2004, due to the change in the trade mark, ISPAT KARMET JSC was renamed into JSC "Mittal Steel Temirtau". In connection with the merger of the world's two largest steel producers Arcelor and the Mittal Steel Company, in September 2007, Mittal Steel Temirtau JSC was renamed ArcelorMittal Temirtau JSC. ArcelorMittal Temirtau JSC is the largest metallurgical enterprise in Kazakhstan with a full metallurgical cycle and a design capacity of 4.5 million tons of rolled products per year.
Today JSC "ArcelorMittal Temirtau" is:
By-product coke production consisting of six coke oven batteries with a production capacity of 3.7 million tons of coke per year. The coking coal of the Karaganda coal basin serves as the raw material for the coke-chemical production;
Blast furnace production. The raw material for blast-furnace smelting is agglomerate, pellets, coke. Fuel oil injection is used as additional fuel. The cast iron is intended for processing in a converter shop. The production capacity of the blast furnace shop is 5.7 million tons of pig iron per year;
Steel-making production. It consists of: a mixing department (2 mixers), a steel smelting section (3 converters), a metal finishing section, two furnace-ladle installations, 2 continuous casting machines, two lime-burning shops, a tar-magnesite shop, a hammer shop. Smelting of boiling, semi-calm, calm and low-alloy steel grades;
Rolling production consists of workshops:
Sheet-rolling shop No. 1, produces hot-rolled steel in coils and sheets with a thickness of 2.0 to 12.0 mm, as well as strips for electric-welded pipes. The capacity of the workshop is 4600 thousand tons per year;
Sheet-rolling shop No. 2, produces cold-rolled steel with a thickness of 0.5 to 2.0 mm., Strip for electric-welded pipes, as well as roofing. The workshop capacity is 1300 thousand tons per year;
Sheet-rolling shop No. 3 (tin shop), produces black and white tin plate for canning with a thickness of 0.18 to 0.36 mm., As well as roofing. The workshop capacity is 750 thousand tons per year;
Hot-dip galvanizing and aluminizing shop (sheet-rolling shop No. 4), produces rolled products with zinc and aluzinc coating and painted rolled products;
Rolling shop, produces a wide range of small and medium-sized rolled products. The workshop capacity is 400 thousand tons per year.
1 Characteristics of sheet rolling shops
1.1 Brief description of LPC No. 1
The date of birth of sheet rolling shop No. 1 can be considered January 6, 1968, when the acceptance certificate of the 1700 rolling mill was signed into operation.
Sheet-rolling shop No. 1 was built by the State Union Institute "Stalproekt".
Rolling Shop No. 1 produces hot-rolled coiled and sheet steel, tackle for cold rolling shops and sheet metal shops with a thickness of 2.0-12 mm, a width of 900-1500 mm.
The shop includes: a highly automated broadband mill "1700" with a capacity of 4600 thousand tons per year; four heating methodical furnaces; finishing department with two cut-to-length units, slitting units and a spar strip production unit.
In the sheet-rolling shop No. 1 there are three departments: thermal, mill "1700" and adjustment.
In the thermal department in four continuous furnaces, the slabs are heated to the rolling temperature. On the mill, in the roughing stands, the slabs are crimped to the thickness of the rolled stock required to obtain the finished sheet in the finishing stands. Reduction of the rolled edges to the required dimensions of the strip width is carried out in a vertical mill and vertical rolls of universal stands No. 2-5.
The strips rolled on the finishing group are cooled with water before coiling into coils to ensure the required mechanical properties using a special spray unit located between the coilers and the finishing group of the mill.
All strips rolled on the mill are coiled on three coilers. The coiled rolls in the stream are weighed on the scales.
At the adjuster, rolls of metal rolled at the mill are stored, shipped to the consumer, and further processed at cut-to-length units No. 1 and No. 2 for cutting them into sheets.
From the cut-to-length units, bundles of sheets go to the finished product warehouse for wrapping, as well as to the normalization unit for heat treatment of sheets.
Finished products in bundles of sheets and rolls are loaded onto rail transport for shipment to customers.
Another part of the hot-rolled coils is delivered to the warehouse in the cold rolling shops (Rolling Shop No. 2 and Rolling Shop No. 3) for further processing.
In addition to hot-rolled sheet products, sheet-rolling shop No. 1 is also engaged in the shipment of commercial slabs.
1.2 Brief description of LPC No. 2
Rolling center # 2 was commissioned in 1973. Workshop design capacity
1.3 million tons per year, products - cold-rolled sheets and coils from 0.5 to 2.0 mm thick, 850 to 1400 mm wide.
The shop has four departments: pickling, rolling, thermal and sheet-cutting.
Hot-rolled coils are processed in pickling lines to remove scale from the strip surface in hydrochloric acid solution. After pickling, rinsing and drying, the edges are trimmed, then the strips are wound into enlarged rolls. One part of pickled coils is transferred to the six-stand rolling mill of the tin shop (Rolling Shop No. 3), the other - to the five-stand cold rolling mill of its shop. The mill carries out rolling with the use of technological lubrication. The rolled coils are fed to the thermal compartment for "bright" annealing in a protective gas atmosphere in bell-type furnaces.
A part of the rolled coils is transferred to the TsGTSA (Rolling Shop No. 4) in the rolling state.
Annealed coils are conditioned to obtain the required surface quality, flatness of strips, as well as the specified physical and mechanical properties of the finished product.
In the sheet-cutting department, after roll training, the edges are cut off and the strip is cut to length, and on slitting machines, the strip is cut into steel sheets.
The resulting rolls and bundles of sheets are transferred to the packaging area, where they are packed and marked, followed by shipment. It is possible to oil the rolled products.
1.3 Brief description of LPC No. 3
On December 31, 1983, the first stage of the sheet metal workshop with a capacity of 445.0 thousand tons per year was put into operation, including 375 thousand tons of tinned electrolytic tin. On December 31, 1986, by an act of the working commission, the second stage of the sheet metal workshop with a capacity of 155.0 thousand tons was put into operation. In 1989, the third stage of the sheet metal workshop with a capacity of 155.0 thousand tons per year was put into operation.
The tin shop is intended for the production of tin-coated tin, black tin, strips, strips of pickled, roofing and structural steel in sheets and coils.
LPC No. 3 consists of four departments:
Rental department;
Thermal department;
Tinning department;
Adjustage;
Figure 1. shows the layout of the units in the workshop.
1 - continuous six-stand mill "1400"; 2- electrolytic cleaning unit No. 1; 3- electrolytic cleaning unit No. 2; 4- separation of bell-type furnaces and furnace stands; 5- unit for continuous annealing of sheet metal No. 1; 6- unit for continuous annealing of sheet metal No. 2; 7- two-stand rolling-temper rolling mill; 8 - two-stand training mill; 9- slitting and strip preparation unit # 1; 10- slitting and strip preparation unit No. 2; 11- slitting and strip preparation unit No. 3; 12- electrolytic tinning unit No. 1; 13- electrolytic tinning unit No. 2; 14- electrolytic tinning unit No. 3; 15- sheet metal cut-to-length unit No. 1; 16- sheet metal cut-to-length unit No. 2; 17- sheet and sheet cut-to-length unit; 18 - unit for packing bundles of sheets; 19-pipe electric welding unit; 20 gear carts.
Figure 1. Layout of the units in the rolling shop No. 3
The rolling department includes: a continuous six-stand mill "1400" (1 pc.), A double-stand rolling-temper mill (1 pc.) And a double-stand temper rolling mill (1 pc.).
The thermal department includes: an electrolytic cleaning unit (2 pcs.), A unit for continuous annealing of sheet metal (2 pcs.), A compartment for bell-type furnaces (68 furnaces and 168 furnace stands)
The tinning department consists of: a slitting and strip preparation unit (3 units), an electrolytic tinning unit (3 units) with an integrated cut-to-length unit (3 units).
The adjuster includes: a sheet and sheet cut-to-length unit (1 pc.), A sheet metal cut-to-length unit (2 pcs.), A sheet pack packing unit (1 pc.)
Hot-rolled metal in coils weighing up to 30 tons serves as a rolling stock for the tin shop. Pickled rolls from Rolling Shop # 2 are fed to a six-stand mill. At the head of the mill, the strips are welded into a continuous strip, which enters the rolling mill. The mill rolls sheet metal and cold-rolled strips using technological lubricant. The rolled strips are coiled into rolls.
After rolling, coils weighing up to 30 tons are cleaned from process lubricant at electrolytic cleaning units and transferred to recrystallization annealing in bell-type furnaces or tower furnaces of continuous annealing units. In order to improve the plasticity and physicochemical characteristics of the metal, the annealed coils are subjected to tempering on a double-stand tempering mill "1400" or rolling to the thinnest sheet on a rolling-tempering mill.
Rolls of the so-called black sheet not intended for tinning are transferred to the adjuster for cutting into sheets, sorting, packing and shipment to consumers.
Rolls intended for the production of tinplate are transferred to slitting and strip preparation units, where after trimming the edges, cutting out defects, trimming the front and rear ends of the rolls, and welding them on a butt-welding machine, rolls are formed for electrolytic tinning units.
When tinning tin at a speed higher than 3-4 m / s, strips on tinning units are wound into rolls, followed by cutting into sheets, sorting, stacking, weighing, packing and marking on a free-standing cut-to-length unit or cutting areas of tinning units.
Tinning machines provide for the production of tinplate with different thickness of tin coating on different sides of the strip. After sorting and packing of packs of tin, finished products are shipped to consumers.
1.4 Brief description of TsGTSA (LPTs No. 4)
The shop operates two units for hot aluminizing (ANGA), galvanizing (LNGC), and a line for applying polymer coatings (LNPP).
The design capacity of the aluzinc plating unit is 320 thousand tons per year, the range of aluzinc products in flat and profiled sheets, and in rolls, with a thickness of 0.4 to 2.0 mm and a width of 750 to 1450 mm. Commissioned in 1998.
The design capacity of the galvanizing unit is 300 thousand tons per year, assortment: galvanized products in sheets and rolls, thickness 0.2-1.6 mm, width 700-1450 mm. Commissioned in 2002.
The technology for the production of rolled products with aluzinc and zinc coatings includes operations for strip preparation, coating in a bath with a molten metal, and surface passivation operations. It is possible to train coated strips.
The production capacity of the line of polymer coatings is 85 thousand tons per year. Products - metal with paint and varnish and polymer coatings, thickness from 0.25 to 1.6 mm, width 650-1370 mm. Commissioned in 2006.
The technology for the production of polymer-coated rolled products includes strip preparation operations, paint application (the application of a primer layer and a base paint layer is performed with rollers in painting booths) and drying the coating in an oven.
Products are delivered in packs and rolls after packaging and labeling. Steel sheet profiles with trapezoidal corrugations with a base thickness of 0.7-0.9 mm and a width of 750-845 mm can be produced.
2 Technology of rolling strips on a six-stand mill "1400"
2.1 Brief technical characteristics of the main technological equipment of the six-stand mill "1400"
According to its purpose, the equipment of the mill is conditionally divided into the following main parts:
Head part, which includes a mechanism for feeding and unwinding rolls, straightening, welding and transporting the strip with tension;
A looping device including a mechanism for creating tension, maintaining and centering the strip to ensure continuous operation of the mill during stops of the head for strip welding;
The inlet part, which provides strip feed from the loop device to stand No. 1 and contains tensioning devices, a loop pit for tension decoupling, guillotine shears for cutting the strip when it is released from the stand;
The mill itself, consisting of six stands with auxiliary mechanisms;
Output part, including flying shears, strip winding mechanism, shooting, weighing and transporting finished rolls.
The mill layout is shown in Figure 2.
1-unwinder # 1; 2-decoiler # 2; 3-roller plate straightening machine; 4-guillotine shears; 5-joint welding machine with a deburring machine; 6-tensioner # 1; 7-guide rollers; 8-loop device; 9-tensioner # 2; 10-tensioner # 3; 11-loop pit; 12-working quarto stands; 13-bypass rollers; 14 flying scissors; 15-winder No. 1; 16-winder # 2; 17-strip tension meter; 18-gauge of strip thickness; 19-wire table.
Picture 2. Scheme of a continuous six-stand mill "1400"
The main operating mode of the mill is endless rolling. With endless rolling, the mill is freed from the strip only when changing to a new strip profile and during reloading.
Main equipment composition:
Head part:
The main mechanisms of the head part are decoilers # 1 and # 2, sheet straightening machine, butt-welding machine and tensioner # 1.
Uncoilers No. 1 and No. 2 of console type with a reduction gear. The gear ratio of the gearbox is i \u003d 3.92, the maximum strip tension is 34.3x103 N (3.5 tf).
The roller plate straightening machine consists of two rows of work rollers (9 pcs.), Between which the end sections of the strips to be straightened and the feed rollers pass.
The butt-welding machine consists of the following main units: the actual butt-welding machine, the deburring device, the device for setting the rear end of the strip, the device for setting the front end of the strip, shears for preparing the ends of the strips for welding.
Tensioner No. 1 consists of three rollers, each roller diameter 1000 mm.
Loop device:
The strip tension is created by a drum rotation drive connected by a rope to a trolley on which two rollers are installed. The rollers are bent around by a strip, creating two horizontal loops (4 branches). The rope drum is connected by a rope with a trolley, on which two rollers are installed. The rollers are bent around in a strip, creating two horizontal loops (4 branches). Rope drum diameter - 1.4 m; trolley travel speed - up to 1.25 m / s, maximum rope tension - 11.2x104 N (11.4 tf).
Input part:
The main mechanisms of the mill inlet are tensioner No. 2, tensioner No. 3. Tensioner No. 2 consists of three rollers with a diameter of 1000 mm. everyone. Tensioner No. 3 consists of two rollers with a diameter of 1000 mm. everyone.
Between the tensioning devices No. 2 and No. 3 there is a loop pit, in which the strip is transported without tension. This allows for the tension decoupling of the head and inlet parts of the mill.
Six-stand mill 1400:
The mill itself consists of six quarto stands. The gear ratios of the stand gearboxes, respectively: i1 \u003d 2.28, i2 \u003d l, 58, i3 \u003d 1.17, i4 \u003d 0.885, i5 \u003d 0.685, i6 \u003d 0.57.
The mill stands are equipped with electromechanical pressure devices, roll cooling and process lubricant supply systems (stands # 5, # 6), anti-bending and additional bending system of work rolls, and a process automation system.
The characteristics of the rolls of the "1400" six-stand mill are given in Table 1.
Table 1
Roll characteristics of a six-stand mill "1400"
Output part:
The main mechanisms of the mill outlet: bypass rollers, flying shears, coilers No. 1 and No. 2, belt conveyor No. 2, a hot air supply manifold to remove the remaining coolant from the strip (T ° C of the supplied air 50-100 °).
The bypass device consists of two rollers - bypass and pressure, with a diameter of 400 and 300 mm, respectively.
Drum-type flying shears, consisting of two knife drums: upper diameter - 353.57 mm, lower - 404.08 mm. Between the drums, a gearing with a tooth ratio of 1.143. The overlap of the knives occurs every 8 revolutions of the upper drum. The number of knives on each drum is 1.
Winders No. 1, No. 2 of console type, gearless. The maximum tension created by the coiler is up to 49x103 N (5 tf).
The conveyor system consists of four conveyors, between the belts of which there are holding electromagnets, two reclining wires. Conveyor No. 3 is stationary, conveyors No. 1, No. 2, No. 4 are mobile.
The mill is equipped with loading and discharge conveyors in the head and tail sections, respectively, and mechanisms for setting rolls, mechanisms for handling work and back-up rolls, scales for weighing coils on the discharge conveyor No. 1. For repair, maintenance of the mill, supply of coils for rolling and transporting them after rolling. electric bridge cranes, the crane brackets of which are equipped with overlays to prevent injury to the rolls.
2.2 Requirements for the rolling stock for the "1400" six-stand mill
Rolls of hot-rolled strips with cut edges, descaled in a continuous pickling unit, serve as a roll for the 1400 six-stand mill. The surface quality and geometric dimensions of the rolled stock must comply with the requirements of ZTU 309-211-2003.
Rolls of hot-rolled strips used as rolled stock must have the following parameters:
2.3 Requirements for renting a six-stand mill "1400"
The products of the 1400 six-stand mill are coils of cold-rolled strips intended for production at the subsequent stages of production: tin according to GOST 13345-85, ASTM A 623 M - 86, ASTM A 623 M - 02, JIS G 3303 - 87, JISG 3303: 2002, EN 10203 - 1991, EN 10202: 2001, and thin sheet products according to GOST 16523-89, GOST 9045-93, EN 10130 - 91, EN 10130 - 98, DIN 1623 - 83, DIN 1623 - 86, ASTM A 611 M - 89 , ASTM A 366 M - 91, ASTM A 568 M - 96, JIS G 3141 - 96, TU 14-11-262-89.
The limit values \u200b\u200bfor the dimensions of finished cold-rolled strips should be:
Coils of finished cold-rolled strips obtained after rolling on the 1400 mill must have the following parameters:
2.4 Preparing the mill for work and setting it up
Preparation of the mill for operation and its adjustment is carried out after repairs, reloading of rolling rolls and other preventive shutdowns of the mill. Adjustment (readjustment) of the mill is also performed when the thickness and width of the rolled metal is changed.
Preparation of the mill for rolling the main assortment includes the following activities:
The state of the double-bar joints of the spindle joints of stands No. 5 and No. 6 is checked by the mechanical service. Wear should not exceed 30% of the operational landing tolerance.
This check is due to the need to eliminate perturbations that cause the formation of periodic variations in thickness, an increase in impulsiveness and other negative factors.
Checking the strapping of the tensor rollers of the tension meters in the inter-stand spaces in order to ensure the stability of the tension is carried out weekly.
The verification of the correctness of the calibration of the tension indicating devices of technological modes is carried out as necessary.
Inspection of the condition of the cooling collectors is carried out under the supervision of a senior roller by fitters of the coolant when handling the work rolls in order to ensure the stability of the thermal profile of the rolls. If there are clogged holes, they are cleaned with a special hook or the manifold is rinsed under pressure.
Preparation of rolls is carried out in accordance with the requirements of TI PZh-19-2006.
The installation of the working and backup rolls after their filling into the stand is carried out by turning on the pressure device, and the upper backup roll is lowered until an additional load on the motors of the pressure screws appears (electromechanical pressure device).
Alignment of the work rolls for parallelism after their filling into the stand is carried out to ensure uniform reductions along the width of the strip by means of an imprint on a metal sample 1.5-2.0 m long.
To form the required thermal profile of the work rolls, they are heated, which is performed in the following order:
After reloading the backup rolls of all stands, heating is carried out by rolling the strips:
After handling the work rolls of all stands, heating is carried out by rolling the strips:
After reloading the work rolls of stands No. 5, No. 6 and No. 1, No. 4, heating is carried out by rolling the strips:
After reloading the work rolls of stand No. 6, heating is carried out by rolling the strips:
After reloading the work rolls of stand No. 5, No. 6 or stopping the mill for no more than 2 hours, the mill is heated up by rolling the strips:
In other cases, the mill is heated by rolling 20 tons of sheet with a thickness of 0.25 - 0.36 mm.
When heating the mill, the rolling speed should be no more than 10-12 m / s, and the width of the strips used for heating the rolls should not be less than the width of the metal rolled in the future.
The remarks revealed during the preparation of the mill for operation are eliminated, after which it is concluded that the mill is ready for rolling the main assortment.
When setting up the mill, the following work is performed:
The appropriate modes of reduction, speed and tension on the stands are selected;
The required thickness settings are selected in front of stand No. 1, behind stands No. 2 and No. 6;
Adjustment of SARTiN (system for automatic regulation of thickness and tension) and SARPF (system for automatic regulation of profile and shape), which is carried out in accordance with the requirements of the "Instructions on the procedure for switching on, switching off and checking the system for automatic regulation of strip thickness and tension on a six-stand mill" 1400 " ;
The final adjustment of the rolls, carried out in the direction of the bending of the front crimped end of the strip when it leaves the stands, when the strip is shifted from the rolling axis to the right, it is necessary to lower the right pressure screw or raise the left one; when the strip is shifted to the left, lower the left pressure screw or raise the right one.
Rolling of sheet metal is carried out in nominal thickness with a tolerance of ± 0.01 mm.
2.5 Coil to mill task
The rolls of rolled stock are floatly installed by a crane on the receiving rack in front of the mill in such a way that the end of the roll coincides with the marks applied on the rack. The strap is removed manually. At the same time, the end sections of the roll are inspected. If they have edge defects such as "flaw", "curl", defective areas are marked with chalk.
The rolls are removed from the rack by the loading beam and transferred to the loading trolley. The roll is centered by the lifting table of the loading cart on the axis of the unwinder, then it is put on the unwinder drum and fixed on it.
With the help of a scraper breaker, the front end of the strip is separated from the bale and fed into the correct-pulling or feed rollers, depending on which decoiler (No. 1 or No. 2) is being prepared for work.
The end of the strip is stopped by the correct-pull or feed rollers and remains in this position until the end of the unwinding of the previous roll. After the mill head speed is reduced to the filling speed, the trailing end of the previous coil leaves the unwinder, passes through the straightening machine and stops under the guillotine shears integrated in the combi butt welder to straighten the strip ends before welding.
After installing the rear end of the previous strip for welding, the front end of the next coil is fed into the sheet straightening machine to the guillotine shears, which is also installed for welding.
In the case of strips in the mill after setting the front end for welding, the profile is measured on each roll using a TPJI-6-1C continuous radioisotope thickness gauge.
If the values \u200b\u200bof the bulge, wedge-shaped, thickening and thinning of the roll profile and surface quality do not meet the requirements of ZTUZ 09-211-2003, an act is drawn up for a roll with deviations signed by the masters of the rolling and pickling departments, as well as control masters of the OTK LPC-2,3- metal is rolled in accordance with the requirements of ZTU 309-211-2003.
A roll with profile deviations is rolled in accordance with the decision of the commission.
The ends of the strips prepared for welding are welded, the beads are removed by a deburring machine built into the butt-welding machine, and the metal chips are blown off the strip.
To fill the loop device with a strip, the head drive is switched on at an increased speed. The strip is transported in the head section by the tensioner No. 1, the strip tension is created by the unwinder No. 1 and No. 2.
In the process of filling the loop device, the condition of the surface and edge of the rolled stock is monitored. In the presence of surface defects such as "through breaks", "rough films", "punctures" not cut out on the NTA, as well as defects on the edge, noted when installing the roll on the unwinder, the defective areas are removed on the scissors of the butt-welding machine (SSM), and the strip welded.
Defective sections of the strip are marked with the melt and roll number, placed in a special cassette, where they are stored for at least 24 hours.
The strip is transported through the loop device by the tensioner No. 2.
In the looping device, the strip tension is created by the drive of a carriage with two drums, with the help of which two strip loops are created.
To center the strip in the looping device there are rotary drums equipped with automatic centering systems.
Tensioner No. 2 feeds the strip into a loop hole with a free loop, which facilitates centering of the strip before entering the mill with the help of centering rollers No. 3.
The strip is pulled from the loop hole by the first mill stand. To create tension on the strip at the entrance to the first stand, a tensioner No. 3 and a roller press table are installed.
Threading the front end of the strip into the mill is carried out at the speed set for each stand.
After threading the strip into the mill, its front end is set on one of the coilers.
2.6 Rolling strips on the mill
The process of rolling strips on the mill includes the following modes:
Acceleration of the mill to working speed;
Rolling at working speed;
Slowing down the mill.
The nominal values \u200b\u200bof the rolling parameters are given in Table 2.
The mill accelerates to the operating speed after threading the front end of the strip onto one of the coilers, after passing the weld or defective section. The acceleration rate must correspond to the value indicated in table 2.
table 2
Nominal rolling parameters
Continuation of table 2
| Strip speed behind stand No. 6, m / s |
33, no more |
| The speed of the strip when cutting it into rolls and refueling on the coiler, m / s |
not less than 2.0 |
| Weld pass speed, m / s |
|
| Strip filling speed: at the head, m / s in the inlet, m / s in the stand, m / s |
from 0.75 to 2.0 incl. |
| Speed \u200b\u200bof release of the rear end of the strip from the stands, m / s |
from 0.75 to 2.0 incl. |
| Shock speed, m / s |
|
| Normal acceleration rate of the mill, m / s |
|
| Normal deceleration rate of the mill, m / s |
|
| Forced rate of deceleration of the mill, m / s |
|
| Normal rate of acceleration, deceleration of the warhead, m / s |
|
| Strip reserve in loop device, m |
|
| Metal pressure on rolls during rolling Н (Тс) |
The deceleration of the mill is performed at the rate specified in Table 2, in the following cases:
When skipping a weld or a defective area up to the speed of skipping a weld;
After winding a roll of a given diameter onto the drum of one of the coilers up to the speed of the strip when cutting it into rolls;
When releasing the tail end of the strip from the mill up to the speed specified in Table 2.
Removal of finished strips from the mill, their acceptance and assignment for further processing.
After winding a coil of a given diameter, the speed of the mill is reduced to a speed that ensures the operation of SARTiN, the strip is cut manually or with flying shears. The rear end of the strip is rewound onto the coiler.
With the help of the auxiliary mechanisms of the winder and the stripper, the roll is removed and moved to the conveyor No. 1 of the harvesting device, where it is strapped.
The coils are transferred by the cleaning device to the chemical cleaning department (removing the roll from the conveyor No. 1) or to the continuous annealing units (removing the roll from the conveyor No. 3) and bell-type furnaces (removing the roll from the conveyor No. 4).
For weighing bales, a scale is installed in the harvesting device.
Simultaneously with the winding of the rear end of the strip, the front end of the next strip is fed to the other coiler by means of conveyor belts. The strip is fixed on the reel drum by a whip, which, after winding several turns, is retracted to the side.
After removing the coils of finished strips from the mill by the senior roller, on every third rolled coil, starting from the first one from the transfer of work rolls or after a break, the surface quality of the strip is assessed. For this purpose, samples are cut from the evaluated rolls. The sample length must be at least 3.0 mm.
The purpose of the metal after the six-stand mill for subsequent annealing is determined by the task of the PWB.
Each rolled roll must be marked with indelible paint on a surface wiped with a rag, indicating:
Heats number;
Steel grade;
Strip dimensions;
Roll size and weight;
Brigade number.
2.7 Management of the mill
The mill is controlled from ten control posts (CP), seven workplaces and twenty local workplaces.
From the central control station (CPUS), the selection of operating modes of the mill mechanisms and technological systems, the selection of the rolling mode, the control of the mill mechanisms and technological systems in automatic and semi-automatic modes, setting the mill to a given rolling program, control of local systems, control of technological parameters of the mill and electrical parameters of the main drives, control of the strip reserve in the loop device using the UVM in all provided modes.
The control unit No. 1-6 controls the speed modes of the mill, pressure screws, roll setting mechanisms, centering rollers and a guide table in front of the stand (stand crankcase covers), control of the position of pressure screws, metal pressure on the rolls, stand speed, inter-stand tension. From the control station No. 1, the control of the mill is also carried out during the passage of the weld and the release of the rear end of the strip, the joint push of the tensioning devices No. 2 and No. 3, the control of the guillotine shears.
2.8 Operation of process lubricant during rolling
Palm oil and its modifications are used as a technological lubricant for rolling sheet metal. Lubrication of the strip during rolling is realized by means of a water-oil mixture (WMC) and a lubricating-cooling liquid (coolant).
IUD is obtained by mixing process lubricant with demineralized water. As a coolant, a liquid is used that is formed as a result of emulsification of a process lubricant from an IUD with chemically purified water.
The supply of BMC and coolant to the strip during rolling should ensure:
Reduction of friction forces;
Heat removal from rolls;
Formation of a minimum of roll and strip wear products;
Minimal degradation of lubricant during rolling;
Ease of removal from the strip wear products of rolls and strip, decomposition products of technological lubricant.
For the preparation of the IUD and its supply through the nozzles to the rolled strip in front of the fifth and sixth stands, there are technological lubrication stations (T-1 and T-2), including a tank - agitators, pipelines for supplying and discharging the IUD and the corresponding pumps.
BMC from the tank - mixer is continuously fed into the corresponding stands of the mill. The IUD is fed into the stand by opening the shut-off valves on the stands after the front end of the strip is set. When the mill stops, the supply of the IUD to the strip is stopped by closing the shut-off valves. When rolling the strip, interruptions in the supply of lubricant are not allowed.
Cooling of work rolls is carried out during rolling of all types of products by supplying coolant to all stands, starts simultaneously with rolling and stops when the mill stops. Coolant supply to the mill is carried out according to three systems with standardized consumption. Adjustment of coolant supply is carried out by selection of the diameter and number of nozzles installed in the collectors along the stands.
The inspection and cleaning of the coolant nozzles is carried out during the scheduled transshipment of the back-up rolls by the technical staff of the coolant under the supervision of the technological personnel of the rolling department. Flushing of the outer side of the coolant collectors in the stands with hot chemically treated water is carried out by the technological personnel of the mill during the PPR.
The coolant circulation system includes sedimentation tanks for its cleaning, refrigerators for cooling to a controlled temperature and pumps for supplying the mill, located in the technological basement.
2.9 Operation of rolls, their handling and cooling
Operation, accounting of durability and transshipment of rolling rolls is carried out in accordance with the requirements of TI PZh-19-2006.
The frequency of transshipment of the back-up and work rolls is controlled according to the documents of the ASUHPS, the transshipment books of the rolling department.
The difference in the diameters of one pair of mill work rolls should be no more than 1.5 mm. The difference in the diameters of the backup rolls for any mill stand is no more than 50 mm.
In stands No. 3, No. 4, No. 6, work rolls with a ground surface of the barrel should be used, in stands No. 1, No. 2, No. 5 - with a surface with notched shot. It is allowed to use ground rolls in all stands of the mill and non-cut rolls in stands # 3, # 4, # 6.
The roughness of the surface of the work rolls in stand No. 5 with a notched surface should be Ra \u003d 2.5-3.0 microns.
The rolls are notched on a shot blasting machine in accordance with the requirements of TI PZh-19-2006.
The frequency of reloading of work rolls is carried out in accordance with the requirements of Table 3.
Table 3
Frequency of handling of the work rolls of the stands
It is allowed to roll strips for roofs in the amount of up to 300 tons after rolling the planned norms of tin.
The frequency of reloading of backup rolls must comply with the requirements of Table 4.
Table 4
Frequency of transfer of backup rolls
Cooling of the rolls is carried out by a cooling lubricant (coolant), which must ensure an effective reduction in friction forces and maximum heat removal from the rolls on all working stands.
2.10 Process control. Sensors and process control devices
When the roll arrives at the mill, compliance control is performed
bale marking data and invoice data. The control of the cross-sectional profile of the rolled stock is carried out by the senior roller or the senior operator of the head of the mill on each roll specified in the mill. Metal with defects found in front of stand No. 1: through breaks, captivity, etc. is rolled at a reduced speed.
The control of the shape of the strip after rolling is carried out according to the readings of the stress meter behind stand No. 6 or visually. The senior roller controls the quality of each rolled coil. The surface quality of the strip is assessed by the senior roller on every third rolled coil, starting from the first roll, after handling the work rolls or after a break using samples cut from these rolls. The length of the samples is not less than 3 m. If a local thickening (roll-up) is found on the strip, the metal is assigned for annealing in ANO No. 1, No. 2 with the mark "roll-up" in the pass-through passport and when marking rolls.
If necessary, the QCD inspector carries out selective control of the surface quality and shape of the rolled strips as in a 6-stand country. The same applies to chemical cleaning units, on a cut metal sample on a surface plate.
Radioisotope thickness gauge of continuous control TRL-6-1S is designed to determine the actual profile of the roll and is installed in the head of the mill in front of the CCM, the thickness gauge is checked by a commission at least 2 times a year. The commission should include a senior mill foreman, the head of the isotope equipment section of LPC-3, and the head of the tin laboratory. Based on the results of the checks, an act is drawn up.
A radioisotope thickness gauge, type FMM-24024, in the amount of three sets, is installed in the second inter-stand gap, in front of stand No. 1 and behind stand No. 6.
The strip tension meter consists of five measuring rollers INR-1400D, installed in the inter-stand gaps No. 1-5 and the information processing unit IPN-7268.
The ASEA stress gauge is installed behind stand No. 6 and is used in the SARPF set.
The meter for the sum and difference of metal pressure on the rolls UIU-2000 is installed one set per stand and is designed to control the metal pressure on the rolls.
The rolling speed is measured by analogue PT-32 tachogenerators and digital speed sensors PDF-1M, connected to the shaft of the mill electric motors.
The sensor of the mechanism for setting the rolls to the rolling level D-41 is installed on the lower electromechanical screws of each stand.
Pressure screw position sensor PKF-12-1.
The load on the electric motors is measured with M32 ammeters installed on the control panels.
Control over the technology of preparation of technological grease, the temperature of the coolant, palm oil and technological grease is carried out by the lubricator, and in the shift - by the shift foreman of the rolling department. The measurement results are recorded in the production book.
Temperature control of the work rolls is carried out if necessary. The temperature of the rolls should not exceed 70 ° C. Every shift, the senior rolling operator monitors the surface quality of the back-up rolls of stand No. 6. When ring rolls are formed on the back-up rolls in the form of fluted convex strips around the circumference of the roll, to eliminate the defect, 50-100 tons of metal with a thickness of 0, 5-0.6 mm with filling into stand No. 6 of work rolls, cut with shot, with a roughness Ra \u003d 1.6-2.5 microns.
To analyze the unstable operation of the mill equipment under the guidance of the senior foreman of the rolling department, the energy and speed parameters of rolling are recorded (speed of the 6th stand, tension in 4.5.6 gaps, rolling force in 4.5.6 stands, thickness deviation from the task behind the 6th stand) on a multichannel recorder. Date, time and thickness of the rolled metal are stamped on the diagram.
Based on the results of the analysis of the diagrams, the technical condition of the technological equipment is assessed. If necessary, measures are determined to stabilize the modes of its operation.
3 Rolling safety
The rolling mill and all auxiliary units should be mechanized as much as possible. Six-stand and temper rolling mills have a high rolling speed. All rotating parts and mechanisms must have guards, protective devices and devices, excluding:
a) touching moving and rotating parts;
b) departure from the mill of equipment debris or strip scraps;
c) exceeding the maximum permissible vibration and noise;
d) injury during roll handling.
All knobs, buttons and other control parts are labeled with their purpose. The handles are securely fixed in the installed position.
When the mill is stopped for repairs, transshipment, lubrication, cleaning and other work, as well as when the mill is started after maintenance work, the provision on the tag system is strictly observed. During the production of work to remove strip scraps, the line contactors of this and the previous stand are turned off. Before removing the serrated strip on the coilers and tensioning devices, the contactor of the sixth stand and the coiler of the mill or tension station is turned off, the automation devices are turned off, the jammed strip is removed by a crane, cut into measured lengths.
Before starting the transshipment, the serviceability and completeness of the lifting devices is checked, the correct installation of the work rolls on the transfer platform of the cart is checked, the pressure device sets a gap between the upper support and work rolls of 150-200 mm. The oil supply pipelines to the balancing and lubrication mechanism of the bearings are disconnected, the clamps for fastening the chocks of the work rolls in the stand are removed; the spindle balancing mechanism is activated, etc.
Transfer of backup rolls is carried out only after disassembling the scheme of the main drives, auxiliary equipment and taking the tag onto the main drive of the rolling stand.
When operating a butt-welding complex, it is necessary to comply with the requirements of GOST 123003-75 "Safety rules for the operation of electrical installations of consumers", "Safety rules and industrial sanitation for electric welding".
The technological process for the preparation, operation and regeneration of the lubricating and cooling liquid meets the requirements of the state standards of the SSBT RK. All operations for the preparation, operation and regeneration of the cutting fluid shall be carried out in accordance with the "General safety rules for enterprises and organizations of the metallurgical industry, labor safety instructions for the maintenance personnel of the cutting fluid department".
All technological operations in the mill during strip rolling by the operating personnel must be carried out in compliance with the rules set out in the safety instructions for the workers of the rolling department.
4 Labor protection during rolling
A potential source of environmental pollution is the cutting fluid (cutting fluid) used in rolling on a six-stand mill.
Coolant and process lubricant are in a closed loop and pass through a system of sedimentation tanks in treatment facilities. Liquid leaks into the storm sewer from a closed treatment system are not allowed. Mechanical impurities from sedimentation tanks, sludge and oil waste are to be burned in the oil waste incineration building. The purified water is returned to the system to cool the rolls.
The mill is flushed with open crankcases included in the sludge collection system. Flushing of impurities into the coolant cleaning system is not allowed.
Conclusion
In the process of passing the industrial practice, an acquaintance was made with the general process of production of cast iron, steel and rolled products at JSC "ArcelorMittal Temirtau" and sheet rolling shops in its composition.
In particular, the process of production of hot rolled steel coils and sheets from slabs at the hot rolling mill "1700" in the sheet rolling shop No. 1 was considered. Also considered:
Cold rolling of steel in rolling mill # 2
Production of rolled products in flat sheets and coils with aluzinc, zinc and polymer coatings, as well as the production of profiled sheets with and without the aforementioned coatings.
The practice took place in the sheet-rolling shop No. 3. During the internship, the process of production of black and white tin, tape, strips from pickled, roofing and structural steel in sheets and coils was considered. The structure of the workshop and its departments was also considered: rolling, thermal, tinning and adjustment. In general terms, the main technological equipment of the workshop departments was considered: rolling mill "1400", electrolytic cleaning units, bell-type furnaces, continuous annealing units, two-stand temper rolling mills, strip preparation units, electrolytic tinning units, cutting units, packing unit and electric pipe welding unit.
The main issue of production practice was the technology of strip rolling on the "1400" six-stand mill. In the process of studying this issue, the following aspects of the technology of strip rolling on the "1400" six-stand mill were considered:
Scheme of a six-stand mill "1400"
Technical characteristics of the main technological equipment of the 1400 six-stand mill
Requirements for the rolling stock for a six-stand mill "1400"
Requirements for rental of a six-stand mill "1400"
Preparing the mill for work and setting it up
Roll to mill task
Rolling strips on the mill
Mill management
Operation of technological lubrication during rolling
Operation of rolls, their handling and cooling
Process control. Sensors and process control devices
Safety and labor protection during rolling
The practice made it possible to get acquainted with the main processes of rolling steel in sheet-rolling shops, and its further processing, which will be necessary in the process of further education at the university.
List of sources used
1. Passport of sheet rolling shop No. 3
2. Technological instruction for cold rolling of strips and sheet metal on a six-stand mill "1400" of sheet-rolling shop No. 3
3. Passport of the six-stand mill "1400"
4. A.I. Tselikov. "Machines and units of metallurgical plants". T 3 "Machines and units for the production and finishing of rolled products" -M: Metallurgy, 1988- 680s.
5. N.I. Sheftel. Rolled metal production technology: Textbook for universities. - M .: Metallurgy, 1976 .-- 576 p.
6. Diomidov BB, Litovchenko NV. Rolling production technology. - M .: Metallurgy, 1979 .-- 488 p.
7. Site: http://arcelormittal.kz/
Between the tensioning devices No. 2 and No. 3 there is a loop pit, in which the strip is transported without tension. This allows for the tension decoupling of the head and inlet parts of the mill.
Six-stand mill 1400:
The mill itself consists of six quarto stands. The gear ratios of the stand gearboxes, respectively: i1 \u003d 2.28, i2 \u003d l, 58, i3 \u003d 1.17, i4 \u003d 0.885, i5 \u003d 0.685, i6 \u003d 0.57.
The mill stands are equipped with electromechanical pressure devices, roll cooling and process lubricant supply systems (stands # 5, # 6), anti-bending and additional bending system of work rolls, and a process automation system.
The characteristics of the rolls of the "1400" six-stand mill are given in Table 1.
Table 1
Roll characteristics of a six-stand mill "1400"
Output part:
The main mechanisms of the mill outlet: bypass rollers, flying shears, coilers No. 1 and No. 2, belt conveyor No. 2, a hot air supply manifold to remove the remaining coolant from the strip (T ° C of the supplied air 50-100 °).
The bypass device consists of two rollers - bypass and pressure, with a diameter of 400 and 300 mm, respectively.
Drum-type flying shears, consisting of two knife drums: upper diameter - 353.57 mm, lower - 404.08 mm. Between the drums, a gearing with a tooth ratio of 1.143. The overlap of the knives occurs every 8 revolutions of the upper drum. The number of knives on each drum is 1.
Winders No. 1, No. 2 of console type, gearless. The maximum tension created by the coiler is up to 49x103 N (5 tf).
The conveyor system consists of four conveyors, between the belts of which there are holding electromagnets, two reclining wires. Conveyor No. 3 is stationary, conveyors No. 1, No. 2, No. 4 are mobile.
The mill is equipped with loading and discharge conveyors in the head and tail sections, respectively, and mechanisms for setting rolls, mechanisms for handling work and back-up rolls, scales for weighing coils on the discharge conveyor No. 1. For repair, maintenance of the mill, supply of coils for rolling and transporting them after rolling. electric bridge cranes, the crane brackets of which are equipped with overlays to prevent injury to the rolls.
2.2 Requirements for the rolling stock for the "1400" six-stand mill
Rolls of hot-rolled strips with cut edges, descaled in a continuous pickling unit, serve as a roll for the 1400 six-stand mill. The surface quality and geometric dimensions of the rolled stock must comply with the requirements of ZTU 309-211-2003.
Rolls of hot-rolled strips used as rolled stock must have the following parameters:
2.3 Requirements for renting a six-stand mill "1400"
The products of the 1400 six-stand mill are coils of cold-rolled strips intended for production at the subsequent stages of production: tin according to GOST 13345-85, ASTM A 623 M - 86, ASTM A 623 M - 02, JIS G 3303 - 87, JISG 3303: 2002, EN 10203 - 1991, EN 10202: 2001, and thin sheet products according to GOST 16523-89, GOST 9045-93, EN 10130 - 91, EN 10130 - 98, DIN 1623 - 83, DIN 1623 - 86, ASTM A 611 M - 89 , ASTM A 366 M - 91, ASTM A 568 M - 96, JIS G 3141 - 96, TU 14-11-262-89.
The limit values \u200b\u200bfor the dimensions of finished cold-rolled strips should be:
Coils of finished cold-rolled strips obtained after rolling on the 1400 mill must have the following parameters:
2.4 Preparing the mill for work and setting it up
Preparation of the mill for operation and its adjustment is carried out after repairs, reloading of rolling rolls and other preventive shutdowns of the mill. Adjustment (readjustment) of the mill is also performed when the thickness and width of the rolled metal is changed.
Preparation of the mill for rolling the main assortment includes the following activities:
The state of the double-bar joints of the spindle joints of stands No. 5 and No. 6 is checked by the mechanical service. Wear should not exceed 30% of the operational landing tolerance.
This check is due to the need to eliminate perturbations that cause the formation of periodic variations in thickness, an increase in impulsiveness and other negative factors.
Checking the strapping of the tensor rollers of the tension meters in the inter-stand spaces in order to ensure the stability of the tension is carried out weekly.
The verification of the correctness of the calibration of the tension indicating devices of technological modes is carried out as necessary.
Inspection of the condition of the cooling collectors is carried out under the supervision of a senior roller by fitters of the coolant when handling the work rolls in order to ensure the stability of the thermal profile of the rolls. If there are clogged holes, they are cleaned with a special hook or the manifold is rinsed under pressure.
Preparation of rolls is carried out in accordance with the requirements of TI PZh-19-2006.
The installation of the working and backup rolls after their filling into the stand is carried out by turning on the pressure device, and the upper backup roll is lowered until an additional load on the motors of the pressure screws appears (electromechanical pressure device).
Alignment of the work rolls for parallelism after their filling into the stand is carried out to ensure uniform reductions along the width of the strip by means of an imprint on a metal sample 1.5-2.0 m long.
To form the required thermal profile of the work rolls, they are heated, which is performed in the following order:
After reloading the backup rolls of all stands, heating is carried out by rolling the strips:
After handling the work rolls of all stands, heating is carried out by rolling the strips:
After reloading the work rolls of stands No. 5, No. 6 and No. 1, No. 4, heating is carried out by rolling the strips:
After reloading the work rolls of stand No. 6, heating is carried out by rolling the strips:
After reloading the work rolls of stand No. 5, No. 6 or stopping the mill for no more than 2 hours, the mill is heated up by rolling the strips:
In other cases, the mill is heated by rolling 20 tons of sheet with a thickness of 0.25 - 0.36 mm.
When heating the mill, the rolling speed should be no more than 10-12 m / s, and the width of the strips used for heating the rolls should not be less than the width of the metal rolled in the future.
The remarks revealed during the preparation of the mill for operation are eliminated, after which it is concluded that the mill is ready for rolling the main assortment.
When setting up the mill, the following work is performed:
The appropriate modes of reduction, speed and tension on the stands are selected;
The required thickness settings are selected in front of stand No. 1, behind stands No. 2 and No. 6;
Adjustment of SARTiN (system for automatic regulation of thickness and tension) and SARPF (system for automatic regulation of profile and shape), which is carried out in accordance with the requirements of the "Instructions on the procedure for switching on, switching off and checking the system for automatic regulation of strip thickness and tension on a six-stand mill" 1400 " ;
The final adjustment of the rolls, carried out in the direction of the bending of the front crimped end of the strip when it leaves the stands, when the strip is shifted from the rolling axis to the right, it is necessary to lower the right pressure screw or raise the left one; when the strip is shifted to the left, lower the left pressure screw or raise the right one.
Rolling of sheet metal is carried out in nominal thickness with a tolerance of ± 0.01 mm.
2.5 Coil to mill task
The rolls of rolled stock are floatly installed by a crane on the receiving rack in front of the mill in such a way that the end of the roll coincides with the marks applied on the rack. The strap is removed manually. At the same time, the end sections of the roll are inspected. If they have edge defects such as "flaw", "curl", defective areas are marked with chalk.
