The billet from the steel mill is only a semi-finished product and must be rolled to the rolling mill before it can become a qualified product.
The continuous casting billet sent from the steel mill first enters the heating furnace and then passes through the rolling mill repeatedly and then enters the finishing mill. Rolling steel belongs to metal pressure processing. To put it simply, rolling steel sheets is like pressing noodles. After multiple extrusions and advancements of the rolling pin, the surface becomes thinner and thinner. In the hot-rolled steel coil production line, the rolling stock is softened, fed into the rolling mill by the roller conveyor, and finally rolled to the size required by the user. Rolling is a continuous uninterrupted operation, the steel belt runs fast on the roller table, the equipment is highly automated and the efficiency is high. The steel ingot coming out of the open hearth can also be a steel plate, but it must be heated and initially rolled to send it to the hot rolling line for rolling. The process is much simpler to use the continuous casting billet. Generally, the thickness of the continuous casting billet is 150. ~250mm, first through dephosphorization to initial rolling, through the roller into the finishing mill, the finishing mill consists of 7 four-roll mills, equipped with speed measuring rollers and flying shears in front of the machine, cutting the head of the board. The finishing mill can reach a speed of 23 m/s. The hot-rolled products are divided into steel coils and ingot plates. The thickness of the hot-rolled rails is usually several millimeters. If the user requires thinner steel sheets, they must be cold-rolled.
Compared with hot rolling, the processing line of cold-rolled steel coil mills is relatively scattered. The cold-rolled products mainly include ordinary cold rolled steel coil, coated sheets, that is, tin plates, galvanized sheets and color coated sheets. After the coil is sent by the hot rolling mill, it must be treated three times in a row. The oxide film is removed with hydrochloric acid before it can be sent to the cold rolling mill. On the cold rolling mill, the uncoiler opens the coil and then introduces the strip into a five-stand mill to roll it into a thin strip. From the five stands, there are also different sizes of ordinary steel coils, which are processed according to the various requirements of users.
The cold rolled steel coil factory supplier produces a variety of different quality products, and the flow is straight down. It seems that the galaxy is nine days long. It is a tin plate. The silver is galvanized. The colors of red, yellow and blue are colored. Coated steel plate. Tinplate is the raw material for making cans and cans. It is also called tinplate. In the past, tinplates required by China were imported. Since the large-scale production of ferrous tinplates, some of them have replaced imported goods. The production of tinplate by WISCO is based on electroplating tin. These tinplates are like mirrors. They are lightly illuminated, just like the poets describe: “The rolling mills make hand-painted gold bills, and the silver mirrors are given to the beloved girl. You know, I don’t know, there is the fragrance of our sweat on the wife’s washing machine.”
There are two production processes for galvanized sheets, one is hot-dip galvanizing and the other is electro-galvanized. The ones that are not surprisingly packaged are silicon steel sheets, which are used in power generation equipment, electromechanical equipment, light industry, food and home appliances. A galvanized sheet is used as a substrate, and various coatings are applied on the reverse side to form a color-coated corrugated roofing sheet. Due to the advanced technology, the coating is very strong and can be directly used in home appliances and as decorative materials. In addition to sheet metal, rolling mills also produce long products such as steel, rails, bars, round bars and wires. The production process and rolling principle are similar to those of sheet metal, but the roll types used are completely different.
Hot rolling process – this is the hot rolling process of our rolled hard roll steel coil factory. Help beginners who don’t understand this line.
1. Brief description of the main rolling line process
The slab is directly sent to the slab warehouse of the hot-rolled steel coil factory by the continuous casting machine blanking roller in the steel-making continuous casting workshop, and the directly hot-sold steel slab is sent to the furnace of the heating furnace for heating, which cannot be directly heated. The installed billet is hoisted into the thermal insulation pit by the crane. After the heat preservation, it is lifted by the crane to the loading rack, and then heated by the heating furnace to fill the furnace, and the possibility of direct rolling is left.
The continuous casting slab is transported into the slab warehouse by the continuous casting workshop through the slab feeding roller or the slab discharging roller. When the slab reaches the entry point, the technical data about the slab has been calculated by the computer of the continuous casting workshop. The system is sent to the computer system of the hot-rolled steel coil factory, and the slab related data is displayed on the monitor so that the staff can check and receive the defect-free slab. In addition, the slab after manual inspection by the cross-trailer also needs to be checked and accepted, and input into the computer. The slab entering the slab library is determined by the slab library computer management system according to the rolling schedule.
Conventional slab furnace rolling: After the slab enters the slab warehouse, the slab is stacked by the slab clamp crane to the specified slab in the slab storage according to the unified instruction of the slab storage control system. During rolling, according to the rolling plan, the slab is lifted from the slab by the slab clamp crane one by one, and hoisted onto the slab loading gantry, and the slab is weighed and checked by the weighing roller. Then, it is sent to the heating furnace charging roller. After the slab is measured and positioned, it is loaded into the heating furnace by the steel loading machine for heating.
Carbon steel thermal insulation pit hot-rolling: After the slab enters the slab warehouse, according to the unified instruction of the slab storage control system, the slab is stacked by the slab clamp crane to the specified position in the thermal insulation pit. During rolling, according to the rolling plan, the slab is taken out from the thermal insulation pit by the slab clamp crane, and hoisted onto the slab loading gantry. The slab is weighed and checked by the weighing roller, and then It is sent to the heating furnace charging roller, and after the slab is measured and positioned, it is loaded into the heating furnace by the steel loading machine for heating.
Direct hot-rolling rolling: When the production plan of continuous casting and hot rolling is matched, the qualified high-temperature continuous casting slab is transported to the weighing roller by the feeding roller of the heating furnace, weighed and checked, and enters the heating furnace. The furnace roller is installed, and the slab is measured and lengthed in front of the designated heating furnace, and then loaded into the heating furnace by the steel loading machine for heating. A part of the direct hot-loaded slab transported by the unloading roller is transported by the crane once and placed on the feeding roller and sent directly to the heating furnace zone. If the steel mill can realize direct hot-loading slabs to be transported by the loading roller, it can reduce the lifting work of some cranes.
The slab is sent to the heating furnace through the feeding roller of the heating furnace, and then loaded into the heating furnace by the loading machine. After heating to the set temperature, it is taken out by the tapping machine according to the rolling rhythm and placed on the heating furnace. On the road.
After the heated slab is discharged from the furnace, it is transported through the conveying roller, and after being descaled by the high-pressure water descaling device, the slab is sent to the fixed-width press to perform side-pressure fixing according to requirements. The maximum width of the fixed width press is 350 mm at a time. Then, it is transported by roller conveyor into the first two-roller reversible roughing mill and the second four-roller reversible roughing mill is rolled, and the slab is rolled into an intermediate billet having a thickness of about 30-60 mm according to the process requirements. The width of the intermediate blank can be controlled by a vertical roll mill in front of each roughing mill.
An intermediate waste blanking device is arranged between the R2 and the flying shear for pushing the intermediate waste blank onto the operating side gantry of the intermediate roller table.
The intermediate blank is conveyed by the intermediate roller belt with the heat preservation cover to the cutting head and the tail cutting at the cutting head of the cutting head, and the heat insulating cover is beneficial for reducing the heat loss of the intermediate blank and the temperature difference between the head and the tail.
There is a side heater before the flying shear, and the edge heater can reduce the temperature difference between the edge and the middle portion of the intermediate blank, improve the uniformity of the galvanized steel coil performance, and improve the quality of the rolled plate.
The cutting head flying shear is equipped with an intermediate blank head and tail shape detector and a shear optimization control system to achieve optimized shearing and reduce the cutting loss of the cutting head.
After the cutting of the strip, the high-pressure water descaling device removes the secondary iron oxide scale before the finish rolling, and is guided by the vertical roll before the finishing rolling into the finishing mill. The intermediate blank passes through the F1~F7 four-roll finishing mill and is rolled into a finished strip of 1.2~25.4 mm.
The belt speed, acceleration, maximum rolling speed, reduction of each frame, work roll roll stroke, and bending force of each frame of the finishing train are all controlled by the computer control system according to the variety and specifications of the rolled hard roll steel coil. Calculate and set the closed loop control that implements the shape of the plate. In order to effectively control the quality of the strip, a rolling line inspection instrument for convexity, straightness, thickness, width and temperature is provided at the exit of the F7 finishing mill, and the surface quality, width, temperature, etc. of the strip are provided at the inlet of the coiler. Rolling line inspection instrument.
The strip rolled by the finishing mill is cooled by the strip cooling system on the output roller by a corresponding cooling system, and the hot rolled steel coil is cooled from the finishing temperature to the specified coiling temperature. The cooling method of strip steel and the amount of cooling water are calculated and controlled by the computer according to different steel grades, specifications, finish rolling temperature and coiling temperature.
When the coiler is worn before the stripper bites into the coil, the speed of the output roller, pinch roll, roll and reel are both ahead of the final frame rolling speed; when the coil is bitten by the coiler The output roller, the pinch roller and the coiler are synchronously rolled up with the finishing mill; when the tail of the strip leaves the final frame, the output roller and the pinch roller are decelerated and lag behind the coiler winding speed. Until the end of the hot rolled steel coil.
After the coiling is completed, the steel coil is taken out by the unloading trolley to the baler for bundling. The coils are then transported backwards by the coil transport system. After being bundled, weighed and marked, they are transported to the hot rolled steel coil finished product warehouse, the cold rolled raw material storage and the finished raw material storage. The steel coil to be inspected is sent to the inspection line, the steel coil is opened for inspection and sampling, and then sent back to the steel coil transportation system. After being bundled, weighed and marked, it is sent to the hot rolled steel coil finished product warehouse and cold rolled raw materials. Library and finishing material library.
The coils cooled in the coil store are sent to the leveling unit, the steel plate cross-cutting unit, the cold rolling shop or the sales plan according to the next processing requirements.
The coils are used in the process of transportation and stacking. The transportation system of steel coils to the coil store or cold-rolled material warehouse adopts the pallet transport system and forms a transport network together with the transport system of the 1780 hot rolling mill. Computer unified control.
From the slab entering the slab library to the delivery of the finished product, the whole process is tracked through the rolling line material tracking system and the two-bank management system to slab, rolling and coiling, thus realizing the automatic production control of the computer.
2. The process of the leveling machine
The hot rolled steel coil is placed on the inlet saddle of the inlet walking beam, and the walking beam transports the steel coil step onto the winding trolley.
The roll-up trolley transports the coil to the coil preparation station to facilitate the removal of the strap, cuts the rolled hard roll steel coil head, simultaneously performs width and radial positioning, and then transports the coil to the unwinder for unwinding.
After the coil is unrolled, it enters the six-roll straightening machine, the leveling machine, the coiler, etc. in order to complete the set flat rolling system.
The leveling machine adopts the balance pressure control technology, and the computer system sets the leveling pressure according to the variety and specification, and is controlled by the hydraulic cylinder. The flattening machine is designed to have a flat thickness of up to 6.5 mm, and the product with a thickness of more than 6.5 mm is only uneven. The split coil is hydraulically fixed and placed at the exit of the leveler.
The finished product roll after the flat roll is unloaded by the unloading trolley and sent to the fixed saddle. The steel coil is transported backwards to the finished product warehouse by the 1# and 2# walking beams, and the weighing and hitting are completed during the conveying process. Bundle work. Finally, the coils are transported by crane to the designated location for stacking.
3. Brief description of the process flow of the steel plate cross-cutting unit
The cranes in the workshop hoist the coils onto the unit’s loading beam conveyor and then transport them to the ground roll station where the coils are horizontally, vertically centered and sheared.
After the steel coil carrying trolley loads the Galvanized Steel Roofing Sheet into the unwinder reel, the coil head enters the pinch roller in turn,
a. Straightening machine unit, looper, disc shearing edge, flying shear finished product cutting, b. Straightening machine straightening, printer or marking machine for drawing, artificial surface inspection station, inspection of qualified steel plate Will be sent to the slab table for stacking.
The defective plate is sent to the defective area through the pinch roller behind the slab table. The flying shear is set by the computer system according to the process system to set the speed and shear length to ensure the shear quality of the steel plate.
The slabs are divided into two groups so that the stacking operation can be continuously operated according to the length and number of steel plates. Stacking is done by wheels that can be moved laterally, depending on the width of the plate. After the stacking is completed, the lifting platform is lowered to place the Galvanized Steel Roofing Sheet on the chain plate conveyor.
The slab is moved laterally by the conveyor chain and sent to the weighing machine of the conveyor. After weighing, the weighed board is transported by conveyor to the unloading roller path behind the conveyor. There are two fixed balers on the discharge roller, which are responsible for the bundling of the steel shovel.
After the baling is completed, the pallet is loaded into the warehouse by the crane.
Simply put, the process of controlling the rolling of the steel and controlling it above the recrystallization temperature is called hot rolling. The process of performing the processing at a normal temperature below the recrystallization temperature is called cold rolling.
The hot rolling of steel has good plasticity and is easy to form. After forming, the steel has no internal stress, which is convenient for the following processes. For steel bars used for construction, Galvanized Steel Roofing Sheets used for stamping, steels to be machined and heat treated are hot rolled steel.
Cold rolling of steel has the characteristics of cold work hardening. Due to the good mechanical properties of cold rolling, many steels used directly use cold rolled steel. Such as cold twisted steel bars, cold rolled steel wire, cold rolled steel coils, etc.