A production process for cold-rolled SPCC-MC steel sheets used in TDI chemical drums

Abstract

This invention discloses a production process for cold-rolled SPCC-MC steel plates used in TDI chemical drums. Firstly, the steel composition is designed as follows: C content 0.03%-0.08%, Si≤0.3%, Mn 0.26%-0.33%, P≤0.020%, S≤0.015%, Al 0.02%-0.05%; the balance being iron and impurities. Using this method, the thickness accuracy of the finished steel product is currently controlled to ±8μm, and the wedge shape and convexity are within 10μm. The weight of the drums manufactured for customers is 19.2-19.35KG. There are no welding defects in the drum body during the manufacturing process; there are no issues with the vent and injection port of the drum lid being poorly sealed, achieving 100% customer satisfaction.

Description

Technical Field

[0001] This invention relates to a production process for cold-rolled SPCC-MC steel plates used in TDI chemical drums. Background Technology

[0002] Toluene diisocyanate (C9H6N2O2) is a colorless, transparent or pale yellow flammable liquid. It is highly toxic and has a strong, pungent odor. It is a strong irritant to the skin, eyes, and respiratory tract. Long-term exposure to or inhalation of high concentrations of TDI can cause bronchitis, allergic asthma, pneumonia, and pulmonary edema. Currently, TDI transportation in my country involves trucks, trains, and ships, with long and complex routes. Therefore, the quality requirements for steel drum processing are extremely high. The steel coils must be free of pinholes and possess good mechanical properties. Currently, the price of TDI is around 18,000 yuan / ton, with a historical high of 30,000 yuan / ton. Therefore, after the steel drums are processed and formed, the weight must be controlled between 19.2 and 19.5 kg, requiring strict dimensional requirements for the steel plates. The drum body dimensions are 1.0mm*920mm, and after welding, the weight is 12.8 to 13.0 kg. The lid / bottom plate thickness is 1.18mm, and the weight after stamping, opening, and flange pressing is 6.25~6.4kg. Customers must conduct the following tests during the barrel manufacturing process: Drop test: Load the barrel with 200KG of tap water and drop it from a height of 1.4 meters; no breakage or leakage. Stacking test: Load a density of 1000KG of weight and maintain it for 24 hours; no obvious deformation or damage. Hydraulic test: 100Kpa water pressure, maintained for 5 minutes; no breakage or leakage. Airtightness test: 20Kpa air pressure, maintained for 5 minutes; no breakage or leakage. This requires the steel coil to have good yield strength, tensile strength, and impact toughness.

[0003] Literature review: "Research on Expansion Cracking of Cold-Rolled Steel for Drums" by Han Jiuyan, Di Yanjun, and Luo Xiaoyang. This study investigated the problem of weld expansion cracking in cold-rolled steel used in customer processing. Metallographic microscopy and SEM were used to compare and analyze the microstructure and metallographic organization of the heat-affected zone (HAZ) and the base metal at the weld. Results showed that the HAZ had finer grains, less directionality, denser dislocations, and shallower dimples compared to the base metal. The HAZ exhibited a brittle fracture morphology, while the base metal showed a ductile fracture morphology. Adjusting welding parameters—reducing welding current speed, increasing welding time, and decreasing post-weld cooling rate—controlled the expansion cracking at the weld to some extent, but could not completely eliminate it. Further comparison with other steel mills in the industry regarding steel composition control for drum manufacturing, including carbon equivalent and cold cracking sensitivity index, led to further optimization of the steel composition for cold-rolled drums at this mill, reducing Mn content and increasing Si and Cr content. However, this analysis is unrelated to the content of this invention. Summary of the Invention

[0004] The purpose of this invention is to provide a production process for cold-rolled steel plate of grade SPCC-MC for TDI chemical drums. This process not only produces cold-rolled steel plates with high dimensional accuracy, but also solves the problem of inadequate sealing of the vent and injection port of the drum lid when used to produce TDI chemical drums.

[0005] The technical solution adopted in this invention is a production process for cold-rolled SPCC-MC steel plates used for holding TDI chemical drums. Firstly, the steel composition is designed as follows: C content 0.03%-0.08%, Si≤0.3%, Mn0.26%-0.33%, P≤0.020%, S≤0.015%, Al0.02%-0.05%; the balance being iron and impurities.

[0006] The production process parameters are as follows:

[0007] 1) Slab continuous casting control and inspection requirements: Continuous casting adopts full argon protection pouring. The tundish empty ladle, ladle long nozzle, submerged entry nozzle, and stopper rod are all argon-sealed casting; carbon-free protective slag and carbon-free ladle covering agent are used; baffles are installed in the tundish; the superheat of the tundish in the first continuous casting is ≤45℃, the superheat of the molten steel in the tundish of the continuous casting furnace is ≤35℃, the continuous casting speed is ≤1.6m / min, constant casting speed is used, and the liquidus temperature of the tap mark AP1462C1 is 1528℃; the liquid level fluctuation in the crystallizer is no more than ±5mm; if there are any process abnormalities, the slab inspection quality must be blocked in time and downgraded; slab inspection must include surface hot inspection. Slabs with scratches, slag accumulation, scale, etc., that do not meet the release standards must be blocked in quality, cleaned and qualified before release. Slabs that pass the hot inspection are hot-sent and hot-charged for rolling.

[0008] 2) Key points for conventional hot rolling process control: Rolled steel grade: SPCC-MC, finished product specifications: 4×975mm, 4×1305mm, tolerance requirements: width tolerance 0~+15mm, crown ≤40μm, wedge shape < crown. Hot rolling production control requirements are as follows: Planning requirements: The rolling plan is prepared according to the requirements of pickled plates, and the production shall not exceed 10 pieces of SPCC-MC. Specific requirements are as follows: Rolling plan 1: 4×1305mm, each rolling cycle is planned Rolling Plan 1: Arrange 2 hot-rolled stock + 10~20 1500mm wide stock + 2 equal-width cold-rolled stock 1270~1310mm transition stock + 10 4×1305mm SPCC-MC stock; Rolling Plan 2: For each rolling of 4×975mm, arrange 2 hot-rolled stock + 10~20 1500mm wide stock + 10 1200~1300mm cold-rolled stock + 5 4×1020mm cold-rolled stock + 10 4×975mm SPCC-MC stock.

[0009] 3) Production process requirements: Slab quality requirements: Slab width tolerance is controlled at the lower limit of +15mm; wedge-shaped slabs are handled after production. Slab heating process control requirements: Furnace temperature soaking zone 1200~1240℃; Furnace temperature second heating zone 1220~1260℃; Furnace temperature first heating zone 1200~1240℃; Furnace temperature preheating zone 1060~1100℃; Furnace exit temperature 1180±30℃; When this steel enters the soaking zone, the rolling pace should be reduced and the time should be greater than 30 minutes; the furnace exit temperature should be controlled at the upper limit of 1180℃.

[0010] 4) Roughing rolling area: Roughing exit temperature: 1060±20℃; Intermediate billet thickness: 40mm; Hot coil box and finishing rolling area: To ensure strip shape quality, a straight-through rolling mode is adopted. The short stroke settings for the finishing rolling side guide plates are: F1-F2 head short stroke -40mm, F3-F6 head short stroke -20mm, F1-F2 middle and tail correction -80mm, F3 middle and tail correction -70mm, F4-F6 middle and tail correction -50mm; All strip cooling water is turned off, and all descaling water is turned on normally according to the model. It is not allowed to reduce the amount of descaling water. The entire steel grade is rolled in one piece to ensure surface finish; The final rolling temperature is controlled at 880±20℃; The coiling temperature is controlled at 600±20℃.

[0011] 5) In the flattened area, steel coils must be inspected for flatness. Any portion exceeding the target wedge convexity must be cut off and repaired. At the same time, the plate shape and surface quality must be checked to ensure that all raw material coils sent to cold rolling meet the design requirements. For hot rolling process quality inspection, plate shape inspection: wedge ≤ convexity ≤ 40µm; wedge abrupt change value ≤ 40µm; the head and tail 50 meters are not used as the basis for the sealing assessment; for coil shape and appearance quality, overflow, tapered, and misaligned coils ≤ 30mm.

[0012] 6) Key points for routine control of cold rolling pickling and rolling mill: The hydrochloric acid temperature in tanks 1-4 should be controlled at 65-75℃, and the operating speed of the process section should be controlled at 60-130 m / min; before producing special steel grades, the pickling unit should replace 60-80 m³ of acid with fresh acid 4 hours in advance, ensuring that the HCl content in tank 1 is ≥50 g / L and the iron ion content is ≤100 g / L, preventing under-pickling; the outlet temperature of the filter in tank 1 should be 60℃-80℃, the conductivity of the rinsing water in tank 2 should be ≤100 μS / cm, and the opening of the rinsing water replenishment valve should be increased by 25%-40% compared to ordinary steel grades; all extrusion rolls must be in good condition, and the accumulator of the hydraulic station in the rolling mill unit and each stand must be in good working order. The AGC accumulator accuracy must meet process requirements. For cold rolling mill tension rolls, the horizontal tilt of the tension roll should not exceed 0.5 mm / m, the vertical tilt of the bearing housing should not exceed 0.5 mm, the horizontal tilt of the bearing housing should not exceed 1 mm, and the perpendicularity of the tension roll axis to the rolling centerline should be less than 0.2 mm / m. The A2 control coefficient of the strip shaper standard control curve should be set to +4, suitable for widths from 930 to 1250 mm. Before production, ensure the last stand's cleaning device is functioning properly; no emulsion residue is allowed on the strip surface; the mill exit cleaning pressure should be >0.6 MPa; nozzles should not be missing or clogged; and condensate from the mill exit stand should not drip onto the strip surface. The residual oil content on a single side of the cold-rolled strip surface should be ≤300 mg / m. 2 The residual iron content on a single side of the strip surface is ≤120mg / m. 2 Rolling speed requirements: The inlet looper coverage must be >60%; Barrel body plate: 1.0*920mm, 5-stand rolling speed 260-280 m / min, uniform rolling time 4 minutes, ensuring uniform rolling thickness; Barrel lid / bottom plate: 1.18*1250mm, rolling speed 260-280 m / min, uniform rolling time 4 minutes, ensuring uniform rolling thickness. Thickness control refers to a target thickness of 1.018±0.015mm for the barrel body plate at 1 / 2 of the steel plate width, and a target thickness of 1.213±0.02mm for the barrel lid / bottom plate. During production, chrome-plated rolls are used on rolling mill #1.

[0013] 7) Process Control Design of Bell-Type Annealing Furnace: The bell-type furnace annealing process uses full hydrogen annealing. The steel coil exit temperature must not exceed 100℃. Before production, the furnace platform must be cleaned of accumulated ash and carbon black until no ash remains. Before production, the furnace platform sealing ring must be inspected and confirmed; if damaged or aged, it must be replaced. If there is loose coiling in the inner ring of the steel coil before loading, spot welding should be performed on the outer part of the coil core where there is no loose coiling. Three spot welds should be made on each side of the outer ring, with the spot weld width controlled to 5 layers of the inner ring and the weld length 30-50mm. The weld length at the head of the coil core on the operating side should be 50-100mm. The furnace loading capacity must not be less than 75 tons, the temperature control is 690℃, the heating time is 10 hours, the holding time is ≥10 hours, the cooling time of the heating bell is 5 hours, and the exit temperature must be 100℃. The hydrogen blowing rate in the second and third stages should be controlled at 25-30m³.3 / h, ensuring sufficient evaporation of residual emulsion; when loading the furnace, steel coils with a tower shape or overflow edge exceeding 40mm can only be loaded on the top layer; for steel coils with an overflow edge ≤15mm, tower shape ≤20mm, and inter-layer stagger of 5mm for tower shape, and 20mm < tower shape ≤40mm, the steel coil can only be placed on the top layer; for tower shape >40mm, rework is required; when loading steel coils into the furnace, the inter-layer stagger of stacking layers must not exceed 100mm, and the overall stagger must not exceed 200mm; large steel coils should be placed on the second or third layer, and steel coils weighing less than 12 tons can only be placed on the top layer, with a convection plate added to the top of the steel coil; cold leakage test, The pressure inside the inner shroud is 50 mbar. After all inlet and outlet valves are closed, if the pressure drop is less than or equal to 7 mbar after 15 minutes, the heating program must be stopped. When heating steel coils, a heating shroud in good condition should be selected to avoid or reduce the number of furnace alarms. Before closing the heating shroud, all problems with the heating shroud should be thoroughly reviewed and resolved. The flexibility of the gas electric regulating valve should be manually checked to ensure that the regulating valve is operating normally without obstruction. The number of burners in operation should reach more than 6. Annealing should be carried out using a dual-platform system, with an additional 430℃ holding platform for 3-4 hours. When the material chamber temperature reaches 650℃, hydrogen blowing must be maintained for 2 hours, with a hydrogen blowing rate of 8 m³ / s. 3 / h; When the steel coil is cooled on the final cooling platform after exiting the furnace, cooling should be stopped after the cooling temperature reaches 45℃. If it rains, the external air intake of the plant should be closed.

[0014] 8) Design of leveling machine process parameters: Before steel coil production, the carbon black on the surface of the leveling saddle and pressure rollers should be wiped off; before steel coil loading, the outer edge defects of the steel coil must be cleaned off; when loading the steel coil, the temperature of the end of the steel coil should be measured, and the temperature of the end on the operating side must be consistent with the ambient temperature; the centering accuracy of the steel coil in the uncoiler should be controlled to ±5mm, and the elongation rate of the leveling unit should be strictly controlled, with the elongation rate deviation controlled to ±0.1%, and the rolling force deviation not exceeding 500KN. The elongation rate setting details are as follows: for incoming material thickness of 1.0mm, the strip elongation rate setting value is 1.1%; for incoming material thickness of 1.2mm, the strip elongation rate setting value is 1.3%; before production, the leveling liquid nozzles should be checked, and there should be no blockage in the emulsion liquid nozzles in the middle of the strip. The number of leveling liquid nozzles should be 5-6 to ensure that the leveling liquid sprays fully cover the plate surface; the concentration of the leveling liquid should be controlled to 3.0%-5.0%. When producing this type of steel, the steel coil should be... Increase the flow rate of the leveling fluid spray in the middle by 20%-30%; the purging air pressure should be >0.47MPa, and the purging angle should be controlled at 45°~60°. Air leakage in the purging device is strictly prohibited. The leveling fluid must be sprayed onto the gap between the upper and lower work rolls. Before producing special steel coils, adjust the leveling fluid nozzles 3-5 coils in advance to ensure uniform spraying. Folding defects are strictly prohibited during coil winding. Normal production speed should be controlled at 500-700m / min to improve the cleanliness of the strip surface. After threading, directly increase the speed to 500m / min. Maintaining a steady speed in the middle is strictly prohibited to reduce the occurrence of leveling fluid stains at the beginning and end of the coil. The leveling unit should be controlled with micro-waves to prevent edge wavy defects and reduce edge drop. When producing this steel grade, the roughness of the work rolls of the leveling unit should be controlled at 2.0±0.1μm, and the roughness of the steel coil should be controlled at 0.8-1.3μm.

[0015] 9) Design and control of process parameters for the recoiling unit: Clean the recoiling leveling machine roller system and the oiling chamber of the oiling machine every Wednesday. Before producing this steel grade, wipe all rotating roller systems, focusing on the leveling machine roller system and the deburring roller surface, paying attention to wiping away any marks on the roller surfaces. Before producing the main steel coil, produce at least 6 ordinary steel coils with a width of 1250mm or more as a transition. Control the centering accuracy of the steel coil feeding to ±5mm. Replace the disc shear blades before production and apply anti-rust oil to the blades. The disc shears should be replaced every 2000 tons, and the disc shear correction accuracy should be controlled to ±2mm. Control the recoiling production speed to 50-200m / min. During recoiling unit production, control the oiling amount according to the contract requirements, keeping the oiling amount at 0.25g / kg. After threading... Immediately increase the speed; prolonged operation at speeds below 50 m / min is strictly prohibited. Before production, check and confirm the oiling effect of the oiling machine. Control the voltage of the upper blade beam of the oiling machine to 60-70 KV and the voltage of the lower blade beam to 65-75 KV. During production, cleanly cut off 30 m from both the beginning and end of the steel coil. When sampling the rewinding unit, take samples along the width direction at 20 mm, 50 mm, and 1 / 4 of the edge. Control the average thickness of the barrel body to 1.0 ± 0.015 mm and the average thickness of the barrel lid to 1.19 ± 0.02 mm. The surface reflectivity of the strip steel in the rewinding unit should be ≥ 70%. Wipe 400 square centimeters with toilet paper; the toilet paper should be smoky gray. Considering the thickness reduction caused by the tensioning and straightening of the rewinding unit, the overall design of this steel grade includes a thickness compensation of 0.01 mm during rewinding.

[0016] Using this method, the thickness accuracy of the finished steel product is now controlled to ±8μm, and the wedge shape and convexity are controlled to within 10μm. The weight of the oil drums manufactured by customers is 19.2-19.35KG. There are no welding defects in the drum body during the drum manufacturing process. There are no problems with the vent and injection port of the drum lid being not tightly sealed. The satisfaction rate is 100%. Detailed Implementation

[0017] A production process for cold-rolled SPCC-MC steel plates used in TDI chemical drums involves first designing the steel composition as follows: C content 0.03%-0.08%, Si≤0.3%, Mn0.26%-0.33%, P≤0.020%, S≤0.015%, Al0.02%-0.05%; the balance being iron and impurities.

[0018] The production process parameters are as follows:

[0019] 1) Slab continuous casting control and inspection requirements: Continuous casting adopts full argon protection pouring. The tundish empty ladle, ladle long nozzle, submerged entry nozzle, and stopper rod are all argon-sealed casting; carbon-free protective slag and carbon-free ladle covering agent are used; baffles are installed in the tundish; the superheat of the tundish in the first continuous casting is ≤45℃, the superheat of the molten steel in the tundish of the continuous casting furnace is ≤35℃, the continuous casting speed is ≤1.6m / min, constant casting speed is used, and the liquidus temperature of the tap mark AP1462C1 is 1528℃; the liquid level fluctuation in the crystallizer is no more than ±5mm; if there are any process abnormalities, the slab inspection quality must be blocked in time and downgraded; slab inspection must include surface hot inspection. Slabs with scratches, slag accumulation, scale, etc., that do not meet the release standards must be blocked in quality, cleaned and qualified before release. Slabs that pass the hot inspection are hot-sent and hot-charged for rolling.

[0020] 2) Key points for conventional hot rolling process control: Rolled steel grade: SPCC-MC, finished product specifications: 4×975mm, 4×1305mm, tolerance requirements: width tolerance 0~+15mm, crown ≤40μm, wedge shape < crown. Hot rolling production control requirements are as follows: Planning requirements: Rolling plans are prepared according to the requirements of pickled plates, and the production shall not exceed 10 pieces of SPCC-MC. Specific requirements are as follows: Rolling plan 1: 4×1305mm, each rolling process is planned Rolling Plan 1: Arrange 2 hot-rolled stock + 10-20 1500mm wide stock + 2 equal-width cold-rolled stock 1270-1310mm transition stock + 10 4×1305mm SPCC-MC stock; Rolling Plan 2: For each rolling of 4×975mm, the plan is to arrange 2 hot-rolled stock + 10-20 1500mm wide stock + 10 1200-1300mm cold-rolled stock + 5 4×1020mm cold-rolled stock + 10 4×975mm SPCC-MC stock.

[0021] 3) Production process requirements: Slab quality requirements: Slab width tolerance is controlled at the lower limit of +15mm; wedge-shaped slabs are handled after production. Slab heating process control requirements: Furnace temperature soaking zone 1200~1240℃; Furnace temperature second heating zone 1220~1260℃; Furnace temperature first heating zone 1200~1240℃; Furnace temperature preheating zone 1060~1100℃; Furnace exit temperature 1180±30℃; When this steel enters the soaking zone, the rolling pace should be reduced and the time should be greater than 30 minutes; the furnace exit temperature should be controlled at the upper limit of 1180℃.

[0022] 4) Roughing rolling area: Roughing exit temperature: 1060±20℃; Intermediate billet thickness: 40mm; Hot coil box and finishing rolling area: To ensure strip shape quality, a straight-through rolling mode is adopted. The short stroke settings for the finishing rolling side guide plates are: F1-F2 head short stroke -40mm, F3-F6 head short stroke -20mm, F1-F2 middle and tail correction -80mm, F3 middle and tail correction -70mm, F4-F6 middle and tail correction -50mm; All strip cooling water is turned off, and all descaling water is turned on normally according to the model. It is not allowed to reduce the amount of descaling water. The entire steel grade is rolled in one piece to ensure surface finish; The final rolling temperature is controlled at 880±20℃; The coiling temperature is controlled at 600±20℃.

[0023] 5) In the flattened area, steel coils must be inspected for flatness. Any portion exceeding the target wedge convexity must be cut off and repaired. At the same time, the plate shape and surface quality must be checked to ensure that all raw material coils sent to cold rolling meet the design requirements. For hot rolling process quality inspection, plate shape inspection: wedge ≤ convexity ≤ 40µm; wedge abrupt change value ≤ 40µm; the head and tail 50 meters are not used as the basis for the sealing assessment; for coil shape and appearance quality, overflow, tapered, and misaligned coils ≤ 30mm.

[0024] 6) Key points for routine control of cold rolling pickling and rolling mills: The hydrochloric acid temperature in tanks 1-4 should be controlled at 65-75℃, and the operating speed of the process section should be controlled at 60-130 m / min; before producing special steel grades, the pickling unit should replace the acid with 60-80 m³ of fresh acid 4 hours in advance. 3 Ensure that the HCl content of the acid solution in the No. 1 acid tank is ≥50g / L and the iron ion content is ≤100g / L, and prevent under-acid pickling; the outlet temperature of the filter in the No. 1 rinsing tank should be 60℃~80℃; the conductivity of the rinsing water in the No. 2 rinsing tank should be ≤100us / cm; the opening of the rinsing water replenishment valve should be increased by 25%~40% compared to ordinary steel grades; all extrusion rolls must be in good condition; the accumulator of the No. 1 hydraulic station of the rolling mill and the AGC accumulators of each stand must meet the process requirements; the installation accuracy of the tension rolls in the cold rolling mill should be such that the horizontal tilt of the tension rolls does not exceed 0.5mm / m. The vertical tilt of the bearing housing should not exceed 0.5mm, the horizontal tilt should not exceed 1mm, and the perpendicularity of the tension roll axis to the rolling center line should be less than 0.2mm / m; the standard control curve A2 of the shape meter should be set to +4, and should be suitable for widths from 930mm to 1250mm; before production, ensure that the last stand's cleaning device is functioning properly, that there is no emulsion residue on the strip surface, that the cleaning pressure at the mill exit is >0.6MPa, that the nozzles are not missing or clogged, and that condensate from the mill exit stand does not drip onto the strip surface; and that the residual oil content on a single side of the cold-rolled strip surface should be ≤300mg / m. 2 The residual iron content on a single side of the strip surface is ≤120mg / m. 2Rolling speed requirements: The inlet looper coverage must be >60%; Barrel body plate: 1.0*920mm, 5-stand rolling speed 260-280 m / min, uniform rolling time 4 minutes, ensuring uniform rolling thickness; Barrel lid / bottom plate: 1.18*1250mm, rolling speed 260-280 m / min, uniform rolling time 4 minutes, ensuring uniform rolling thickness. Thickness control refers to a target thickness of 1.018±0.015mm for the barrel body plate at 1 / 2 of the steel plate width, and a target thickness of 1.213±0.02mm for the barrel lid / bottom plate. During production, chrome-plated rolls are used on rolling mill #1.

[0025] 7) Process Control Design of Bell-Type Annealing Furnace: The bell-type furnace annealing process uses full hydrogen annealing. The steel coil exit temperature must not exceed 100℃. Before production, the furnace platform must be cleaned of accumulated ash and carbon black until no ash remains. Before production, the furnace platform sealing ring must be inspected and confirmed; if damaged or aged, it must be replaced. If there is loose coiling in the inner ring of the steel coil before loading, spot welding should be performed on the outer part of the coil core where there is no loose coiling. Three spot welds should be made on each side of the outer ring, with the spot weld width controlled to 5 layers of the inner ring and the weld length 30-50mm. The weld length at the head of the coil core on the operating side should be 50-100mm. The furnace loading capacity must not be less than 75 tons, the temperature control is 690℃, the heating time is 10 hours, the holding time is ≥10 hours, the cooling time of the heating bell is 5 hours, and the exit temperature must be 100℃. The hydrogen blowing rate in the second and third stages should be controlled at 25-30m³. 3 / h, ensuring sufficient evaporation of residual emulsion; when loading the furnace, steel coils with a tower shape or overflow edge exceeding 40mm can only be loaded on the top layer; for steel coils with an overflow edge ≤15mm, tower shape ≤20mm, and inter-layer stagger of 5mm for tower shape, and 20mm < tower shape ≤40mm, the steel coil can only be placed on the top layer; for tower shape >40mm, rework is required; when loading steel coils into the furnace, the inter-layer stagger of stacking layers must not exceed 100mm, and the overall stagger must not exceed 200mm; large steel coils should be placed on the second or third layer, and steel coils weighing less than 12 tons can only be placed on the top layer, with a convection plate added to the top of the steel coil; cold leakage test, The pressure inside the inner shroud is 50 mbar. After all inlet and outlet valves are closed, if the pressure drop is less than or equal to 7 mbar after 15 minutes, the heating program must be stopped. When heating steel coils, a heating shroud in good condition should be selected to avoid or reduce the number of furnace alarms. Before closing the heating shroud, all problems with the heating shroud should be thoroughly reviewed and resolved. The flexibility of the gas electric regulating valve should be manually checked to ensure that the regulating valve is operating normally without obstruction. The number of burners in operation should reach more than 6. Annealing should be carried out using a dual-platform system, with an additional 430℃ holding platform for 3-4 hours. When the material chamber temperature reaches 650℃, hydrogen blowing must be maintained for 2 hours, with a hydrogen blowing rate of 8 m³ / s. 3 / h; When the steel coil is cooled on the final cooling platform after exiting the furnace, cooling should be stopped after the cooling temperature reaches 45℃. If it rains, the external air intake of the plant should be closed.

[0026] 8) Design of leveling machine process parameters: Before steel coil production, the carbon black on the surface of the leveling saddle and pressure rollers should be wiped off; before steel coil loading, defects in the outer folding edge of the steel coil must be cleaned off; when loading the steel coil, the temperature at the end of the steel coil should be measured, and the temperature at the end on the operating side must be consistent with the ambient temperature; the centering accuracy of the steel coil in the uncoiler should be controlled to ±5mm, and the elongation rate of the leveling unit should be strictly controlled, with the elongation rate deviation controlled to ±0.1%, and the rolling force deviation not exceeding 500KN. The elongation rate setting details are as follows: for incoming material thickness of 1.0mm, the strip elongation rate setting value is 1.1%; for incoming material thickness of 1.2mm, the strip elongation rate setting value is 1.3%; before production, the leveling liquid nozzles should be checked, and there should be no blockage in the emulsion liquid nozzles in the middle of the strip. The number of leveling liquid nozzles should be 5-6 to ensure that the leveling liquid sprays onto the entire plate surface; the concentration of the leveling liquid should be controlled to 3.0%-5.0%, and the steel coil should be... Increase the leveling fluid spray flow rate by 20%-30%; the purging air pressure should be >0.47MPa, and the purging angle should be controlled at 45°~60°. Air leakage in the purging device is strictly prohibited. The leveling fluid must be sprayed onto the gap between the upper and lower work rolls. Before producing special steel coils, adjust the leveling fluid nozzles 3-5 coils in advance to ensure uniform spraying. Folding defects are strictly prohibited during coil winding. Normal production speed should be controlled at 500-700m / min to improve strip surface cleanliness. After threading, directly increase the speed to 500m / min, avoiding mid-speed stabilization to reduce leveling fluid stains at the coil ends. The leveling unit should be controlled with micro-waves to prevent edge wavy defects and reduce edge drop. When producing this steel grade, the surface roughness of the leveling unit's work rolls should be controlled at 2.0±0.1μm, and the surface roughness of the steel coils should be controlled at 0.8-1.3μm.

[0027] 9) Design and control of process parameters for the recoiling unit: Clean the recoiling leveling machine roller system and the oiling chamber of the oiling machine every Wednesday. Before producing this steel grade, wipe all rotating roller systems, focusing on the leveling machine roller system and the deburring roller surface, paying attention to wiping away any marks on the roller surfaces. Before producing the main steel coil, produce at least 6 ordinary steel coils with a width of 1250mm or more as a transition. Control the coil feeding alignment accuracy to ±5mm. Replace the disc shear blades before production and apply rust-preventive oil to the blades. Replace the disc shears every 2000 tons, and control the disc shear correction accuracy to ±2mm. Control the recoiling production speed to 50-200m / min. During recoiling unit production, control the oiling amount according to the contract requirements, keeping it at 0.25g / ㎡. Apply oil immediately after threading. Increase the speed; prolonged operation at speeds below 50 m / min is strictly prohibited. Before production, check and confirm the oiling effect of the oiling machine. Control the voltage of the upper blade beam of the oiling machine to 60-70 KV and the voltage of the lower blade beam to 65-75 KV. During production, cut off 30 m from both the beginning and end of the steel coil. When sampling the rewinding unit, take samples along the width direction at 20 mm, 50 mm, and 1 / 4 of the edge. Control the average thickness of the barrel body to 1.0 ± 0.015 mm and the average thickness of the barrel lid to 1.19 ± 0.02 mm. The surface reflectivity of the strip steel in the rewinding unit should be ≥ 70%. Wipe 400 square centimeters with toilet paper; the toilet paper should be smoky gray. Considering the thickness reduction caused by the tensioning and straightening of the rewinding unit, the overall design of this steel grade includes a thickness compensation of 0.01 mm during rewinding.

[0028] Example

[0029] The hydrochloric acid temperature in tanks 1-4 of the pickling unit should be controlled at 65-75°C, and the operating speed of the process section should be controlled at 60-130 m / min. If the speed drops below 60 m / min under special circumstances, corrosion inhibitor should be added immediately.

[0030] Before producing special steel grades, the pickling unit replaces 60-80 m³ of acid with fresh acid 4 hours in advance to ensure that the HCl content of the acid solution in the No. 1 acid tank is ≥50 g / L and the iron ion content is ≤100 g / L, thus preventing the occurrence of under-pickling of steel coils.

[0031] The outlet temperature of the filters in rinsing tanks 1-4 of the pickling unit is 60℃~80℃; the conductivity of the rinsing water in rinsing tank 2 is ≤100us / cm; and the opening of the rinsing water supply valve is increased by 25%~40% compared to ordinary steel grades.

[0032] All the surface and operating condition of the squeezing rollers of the pickling unit must be intact. The roller surface is not allowed to have serious wear, adhesion, scratches, peeling, or heat damage defects. There must be no jamming during operation. There must be no "watermark" defects at the outlet of the pickling dryer.

[0033] The accuracy of the accumulators in the No. 1 hydraulic station of the rolling mill and the AGC accumulators in each stand must meet the process requirements. The installation accuracy of the tension rolls in the cold rolling mill is as follows: the maximum horizontal tilt of the tension rolls should not exceed 0.5 mm / m, the maximum vertical tilt of the bearing housing should not exceed 0.5 mm, the maximum horizontal tilt of the bearing housing should not exceed 1 mm, the perpendicularity of the tension roll axis to the rolling center line should be less than 0.2 mm / m, and the thickness gauge measurement accuracy should be controlled to 0.001 mm.

[0034] Before production, the No. 1 mill of the rolling mill unit will use chrome-plated rolls.

[0035] The rolling mill's plate shape is controlled according to a micro-double-sided wave pattern, and medium waves are strictly prohibited. The standard control curve A2 control coefficient of the plate shape meter is set to +4 (suitable for widths from 930 to 1250 mm).

[0036] Before production, the rolling mill unit wipes the exit guide rolls and plate rolls, and checks and confirms the exit archway splash guard to prevent oil stains from dripping onto the surface of the steel coils.

[0037] During rolling mill operation, ensure the last stand's purging device is functioning properly. No emulsion residue is allowed on the strip surface, and the mill exit purging pressure must be greater than 0.6 MPa. Nozzles must not be missing or clogged, and condensate from the mill exit stand must not drip onto the strip surface.

[0038] The residual oil content on the surface (single side) of the cold-rolled strip steel from the rolling mill unit is ≤300mg / m. 2 Residual iron content on the surface of the strip (single side) ≤120mg / m 2 ;

[0039] Rolling speed requirements for rolling mill units:

[0040] The inlet looper coverage should be greater than 60%. For the barrel body plate: 1.0*920mm, the rolling speed should be 260-280 m / min for 5 stands, and the rolling time should be uniform for 4 minutes. For the barrel lid / bottom plate: 1.18*1250mm, the rolling speed should be 260-280 m / min, and the rolling time should be uniform for 4 minutes to ensure uniform rolling thickness.

[0041] The rolling mill thickness control (referring to the steel plate width at 1 / 2 point) is as follows: target thickness of barrel body plate 1.018±0.015mm, target thickness of barrel lid / bottom 1.213±0.02mm.

[0042] Before production, the ash (carbon black) accumulated on the furnace platform of the bell-type furnace unit is cleaned until there is no ash.

[0043] Before production, the furnace platform sealing ring of the bell-type furnace unit should be inspected and confirmed. If damage or aging is found, it must be replaced.

[0044] If there is loose coiling on the inner ring of the steel coil before the furnace assembly of the bell-type furnace, spot welding should be performed on the outer part of the coil core where there is no loose coiling. Three spot welds should be performed on each side of the outer ring, with the spot weld width controlled to be 5 layers on the inner ring and the weld length 30-50mm. The weld length at the head of the coil core on the operating side should be 50-100mm.

[0045] The furnace capacity of the bell-type furnace should not be less than 75 tons, the controlled temperature should be 690℃, the heating time should be 10 hours, the holding time should be ≥10 hours, the cooling time of the bell-type furnace after heating should be 5 hours, and the furnace outlet temperature should be 100℃. The hydrogen blowing rate in the second and third stages should be controlled at 25-30 m³ / h. 3 / h, to ensure that residual emulsion is fully evaporated;

[0046] When assembling a bell-type furnace, steel coils that are tower-shaped and have an overflow edge exceeding 40mm can only be loaded onto the top layer.

[0047] For bell-type furnace units, the overflow edge of the steel coil is ≤15mm, the tower shape is ≤20mm, the interlayer staggered tower shape is 5mm, and when 20mm < tower shape ≤40mm, the steel coil can only be placed on the top layer. If the tower shape >40mm, rework is required.

[0048] When loading steel coils into the bell-type furnace unit, the misalignment between stacked layers shall not exceed 100mm, and the overall misalignment shall not exceed 200mm.

[0049] When placing large steel coils in a bell-type furnace unit, they should be placed on the second or third layer. When the weight of the steel coil is less than 12 tons, it can only be placed on the top layer, and a convection plate should be added to the top of the steel coil.

[0050] For the cold leakage test of the bell-type furnace unit, the pressure in the inner shroud is 50 mbar. After all inlet and outlet valves are closed, if the pressure drop is less than or equal to 7 mbar after 15 minutes, the heating program must be stopped.

[0051] When heating steel coils in a bell-type furnace unit, a heating hood in good condition should be selected to avoid or reduce the number of furnace alarms.

[0052] Before attaching the heating cover to the bell-type furnace unit, a comprehensive review and resolution of any issues with the heating cover should be conducted. The flexibility of the gas electric regulating valve should be manually checked to ensure that the regulating valve operates normally without obstruction. The number of burners in operation should be increased to more than 6.

[0053] The bell-type furnace unit adopts a dual-platform annealing process, with an additional 430℃ heat preservation platform for 3-4 hours;

[0054] When the temperature in the material chamber of the bell-type furnace unit reaches 650℃, hydrogen blowing must be maintained for 2 hours at a rate of 8m³ / h. 3 / h.

[0055] When steel coils from the bell-type furnace are cooled on the final cooling platform after exiting the furnace, cooling is stopped once the cooling temperature reaches 45°C. In case of rain, the external air intake of the plant must be closed.

[0056] Before producing steel coils, the surface of the leveling saddle and pressure roller is wiped with carbon black.

[0057] Before feeding the steel coils into the leveling unit, any defects in the outer edge of the steel coils must be completely removed.

[0058] When feeding steel coils into the leveling unit, the temperature at the end of the steel coil must be measured, and the temperature at the operating end must be consistent with the ambient temperature.

[0059] The centering accuracy of the steel coil is controlled to ±5mm on the uncoiler.

[0060] The leveling unit strictly controls the elongation rate, with the elongation rate deviation controlled to ±0.1%, and the rolling force deviation not exceeding 500KN. The elongation rate setting details are as follows:

[0061] (1) Incoming material thickness 1.0 mm, strip elongation set at 1.1%

[0062] (2) Incoming material thickness 1.2 mm, strip elongation set at 1.3%.

[0063] Before production, the leveling fluid nozzles of the leveling unit should be inspected. There should be no blockage in the emulsion nozzles in the middle of the strip. The number of leveling units should be 5-6 to ensure that the leveling fluid is sprayed to fully cover the strip surface.

[0064] When producing this type of steel, the leveling fluid concentration in the leveling unit should be controlled at 3.0%-5.0%, and the leveling fluid spray flow rate in the middle of the steel coil should be increased by 20%-30%.

[0065] The purging jet pressure of the leveling unit is >0.47MPa, the purging angle is controlled at 45°~60°, and the purging device must not leak air.

[0066] The leveling fluid of the leveling unit must be sprayed onto the gap between the upper and lower working rolls. Before producing special steel coils, the leveling fluid nozzles should be adjusted 3-5 coils in advance to ensure the uniformity of the leveling fluid spray.

[0067] Folding defects are strictly prohibited when coiling steel.

[0068] Normal production speed should be controlled at 500-700m / min to improve the cleanliness of the strip steel surface. After the strip is threaded, the speed should be increased directly to 500m / min. It is strictly forbidden to maintain a steady speed in the middle to reduce the occurrence of surface finishing liquid stains at the beginning and end of the steel coil.

[0069] The leveling unit is controlled according to the micro-medium wave control, and edge wave defects are strictly prohibited in order to reduce edge drop;

[0070] (When producing this steel grade, the roughness of the working rolls of the leveling unit is controlled at 2.0±0.1μm, and the roughness of the steel coil is controlled at 0.8-1.3μm;

[0071] Every Wednesday, the recoiling unit cleans the recoiling leveling machine roller system and the oiling machine oiling chamber. Before producing this type of steel, all rotating roller systems are wiped clean, with a focus on the leveling machine roller system and the deburring roller surface. Pay attention to wiping away the marks on the wide and narrow areas of each roller surface.

[0072] Before the rewinding unit produces steel coils, at least 6 ordinary steel coils with a width of 1250 mm or more should be produced as a transition.

[0073] The centering accuracy of the steel coil feeding in the rewinding unit is controlled to ±5mm.

[0074] If there is residual leveling liquid or oil on the outer ring of the incoming material in the rewinding unit, the outer ring must be cleaned at the inlet to prevent the defects from adhering to the rotating roller system and then adhering to the strip surface again.

[0075] Before production, the blades of the disc shears are replaced and rust-preventive oil is applied to the blades. The disc shears are replaced every 2,000 tons, and the disc shears' correction accuracy is controlled to ±2 mm.

[0076] The rewinding production speed is controlled at 50-200m / min. Since the single-sided cutting edge is about 30mm, close attention should be paid to the cutting edge quality and the waste edge winding situation to prevent the edge wires from "flying out" during cutting.

[0077] During production, the oiling amount of the rewinding unit should be controlled according to the contract requirements, and the oiling amount should be controlled at 0.25g / ㎡. After the tape is threaded, the speed should be increased immediately. It is strictly forbidden to run at a speed below 50m / min for a long time. Before production, check and confirm the oiling effect of the oiling machine. If uneven oiling is found, stop the machine in time and rinse the blade beam. If necessary, pull out the blade beam and clean it with a plug. The voltage of the upper blade beam of the oiling machine should be controlled at 60-70KV, and the voltage of the lower blade beam should be controlled at 65-75KV.

[0078] During production on the rewinding unit, the first and last 30 meters of the steel coil are completely removed. This is mainly to remove the steel coil that was damaged during the leveling process.

[0079] Defects caused by speed reduction, such as head and tail leveling fluid stains and thickness deviations when the mill passes through weld seams;

[0080] When sampling with the rewinding unit, the thickness is measured at 20mm, 50mm, 1 / 4, and the middle along the width of the plate (7-point value recording). Considering the matching between the barrel body and the barrel lid and the influence of the length on the weight of the steel barrel body, the average thickness of the barrel body is controlled to 1.0±0.015mm, and the average thickness of the barrel lid is controlled to 1.19±0.02mm. The average thickness is not the average of the 7-point value recording, and the thickness is calculated by weighing the sample, with the density calculated according to 7.85 tons / square meter.

[0081] The surface reflectivity of the strip steel in the rewinding unit is ≥70%. When wiping 400 square centimeters with toilet paper, the toilet paper turns smoky gray.

[0082] Taking into account the thickness reduction caused by the tensioning and straightening of the rewinding unit, the overall design of this steel grade compensates for a thickness of 0.01 mm by rewinding.

Claims

1. A production process of a barrel cold-rolled steel SPCC-MC for containing TDI chemical industry, first, the composition of the steel material is designed: C content 0.03%-0.08%, Si≤0.3%, Mn 0.26%-0.33%, P≤0.020%, S≤0.015%, Al 0.02%-0.05%; the balance is iron and impurities; characterized in that The production process step parameters are as follows: 1) Slab continuous casting control and inspection requirements: The continuous casting adopts full-range argon protection pouring, the tundish is empty, the long nozzle of the ladle, the submerged nozzle and the stopper all adopt argon sealing pouring; carbon-free protective slag and carbon-free ladle covering agent are used; the tundish is installed with a retaining wall; the tundish overheat of the first furnace is ≤45℃, the tundish steel overheat of the continuous casting furnace is ≤35℃, the continuous casting speed is ≤1.6m / min, the constant speed continuous casting, the liquidus temperature of the steel mark AP1462C1 is 1528℃; the crystallizer liquid level fluctuation is not more than ±5mm; the process abnormal slab is timely informed to the slab inspection quality block, and the degradation treatment; the slab inspection must be carried out the slab surface heat inspection, the slab with scratch, slag accumulation and scarring not meeting the release standard must be quality blocked, and released after cleaning; the slab heat inspection is qualified for hot sending and hot rolling; 2) The conventional process control points of hot rolling: Steel grade: SPCC-MC, finished product specification: 4×975mm, 4×1305mm, tolerance requirement: width tolerance 0~+15mm, convexity ≤40μm, wedge < convexity, the hot rolling production control requirements are as follows: plan arrangement requirement: the rolling plan is prepared according to the pickling plate requirement, the production is not more than 10 pieces of SPCC-MC, the specific requirements are as follows: rolling plan 1: 4×1305mm, 2 pieces of hot roll material are arranged for each rolling plan +10-20 pieces of 1500mm width +2 pieces of equal width cold rolling material 1270-1310mm transition +10 pieces of 4×1305mm SPCC-MC; rolling plan 2: 4×975mm, 2 pieces of hot roll material are arranged for each rolling plan +10-20 pieces of 1500mm width +10 pieces of 1200-1300mm cold rolling material +5 pieces of 4×1020mm cold rolling material +10 pieces of 4×975mm SPCC-MC; 3) Production process requirements: slab quality requirements, the slab width size tolerance is controlled according to the +15mm lower limit, and the wedge-shaped blank is disposed at the lower line; slab heating process control requirements: furnace temperature soaking section 1200-1240℃; furnace temperature two adding section 1220-1260℃; furnace temperature one adding section 1200-1240℃; furnace temperature preheating section 1060-1100℃; discharge temperature 1180±30℃; the steel enters the soaking section to reduce the rolling rhythm, the time is greater than 30min, and the discharge temperature is controlled according to the upper limit of 1180℃; 4) In the rough rolling area, the rough rolling outlet temperature is 1060±20℃; the intermediate blank thickness is 40mm; in order to ensure the plate shape quality, the straight-through mode is adopted for rolling, the precision rolling side guide plate short stroke is set as F1-F2 head short stroke-40mm, F3-F6 head short stroke-20mm, F1-F2 middle tail correction-80mm, F3 middle tail correction-70mm, F4-F6 middle tail correction-50mm; all the strip cooling water is closed, all the phosphorus removal water is normally opened according to the model, the phosphorus removal water is not allowed to be reduced, one piece of steel is rolled in the whole line for rolling the steel grade to ensure the surface; the finish rolling temperature is controlled according to 880±20℃; the coiling temperature is controlled according to 600±20℃; 5) Flat area, steel roll in the flat inspection, more than the target wedge-shaped convex part cut repair, while checking the shape, surface quality, to ensure that the original material coil sent to the cold rolling all meet the design requirements; hot rolling process quality inspection, shape inspection: wedge-shaped convexity ≤ 40 μm; wedge-shaped mutation value ≤ 40 μm; head and tail 50 meters not as a basis for blocking assessment; coil shape and appearance quality, overflow, tower-shaped, wrong edge coil ≤ 30 mm; 6) Cold rolling pickling, the conventional control points of rolling mill, 1-4# tank hydrochloric acid temperature control to 65~75℃, process section running speed control to 60-130m / min; pickling mill set in advance 4 hours before the production of special steel, replacement of new acid 60-80m³, ensure that 1# acid tank HCL content of acid liquid test value ≥50g / L, iron ion content ≤100g / L, to prevent the phenomenon of pickling; 1# rinsing tank filter outlet temperature 60℃~80℃, 2# rinsing tank rinsing water conductivity test value ≤100us / cm, rinsing water valve opening degree of water supply valve table increased by 25%~40% than ordinary steel, all the wrung roll surface, the running state must be perfect, rolling mill set 1# hydraulic station accumulator, AGC accumulator precision must meet the process requirements, cold rolling mill tension roll installation precision tension roll horizontal inclination not more than 0.5mm / m, bearing seat vertical inclination not more than 0.5mm, bearing seat horizontal inclination not more than 1mm, tension roll axis and rolling center line perpendicularity less than 0.2mm / m; shape instrument standard control curve A2 control coefficient set for +4, width 930 to 1250㎜ all adapt; before production to ensure that the last mill blowing device is normal, the surface of the strip steel is not allowed to exist emulsion residue, rolling mill outlet blowing pressure >0.6MPA, nozzle is not allowed to be missing and blocked, rolling mill outlet gantry condensate water can not drop on the surface of the strip steel; rolling mill cold hard coil surface single residual oil content ≤300mg / m 2 , the surface of the strip steel single residual iron content ≤120mg / m 2 ; rolling speed requirements: entrance loop set volume to ensure >60% above, barrel body plate: 1.0*920mm, 5 machine frame rolling speed according to 260-280m / min, uniform speed rolling time 4 minutes, to ensure the uniformity of rolling thickness; barrel cover / bottom plate: 1.18*1250mm rolling speed according to 260-280m / min, uniform speed rolling 4 minutes, to ensure the uniformity of rolling thickness, thickness control pointer steel plate width 1 / 2 barrel body plate target thickness 1.018±0.015mm, barrel cover / bottom target thickness 1.213±0.02mm, rolling mill set production 1# rolling mill using plating roll; 7) Process control design of batch annealing furnace: The process of batch annealing is full hydrogen complete annealing, the temperature of coil out of furnace should not be higher than 100℃, the dust and carbon black on the furnace platform should be cleaned before production; the sealing ring of furnace platform should be checked and confirmed before production, if it is damaged or aged, it must be replaced; if there is loose coil in the inner circle of coil before loading, spot welding should be carried out on the outer side of the coil core without loose coil, 3 spots are welded on each side of the outer circle, the spot welding width is controlled within 5 layers of the inner circle, the welding length is 30-50mm, and the welding length of the coil core head on the operation side is 50-100mm; the loading amount should not be less than 75 tons, the temperature is controlled at 690℃, the heating time is 10h, the holding time is ≥10h, the cooling time of heating cover is 5h, the out-of-furnace temperature is 100℃, the hydrogen blowing amount of the second and third sections is controlled at 25-30m 3 / h, to ensure that the residual emulsion is fully volatilized; when loading, the coil with tower shape and overflow edge exceeding 40mm can only be loaded on the uppermost layer; the overflow edge of the coil is ≤15mm, the tower shape is ≤20mm, the tower shape of the interlayer stagger is 5mm, 20mm 3 / h; when the coil is out of the furnace, the cooling temperature reaches 45℃, the cooling is stopped, and the outside suction port of the plant needs to be closed in case of rainy weather; 8) Design of flat rolling process parameters: steel coil before production, the flat roller, carbon black on the surface of the saddle, wipe; steel coil before loading, the outer edge of the steel coil defect cut clean; steel coil loading, the end of the steel coil temperature measurement, the operating side end temperature must be consistent with the site temperature; steel coil in the centering accuracy control to ± 5mm, flat rolling unit strictly control the elongation, elongation deviation control to ± 0.1%, rolling force deviation shall not be greater than 500KN, elongation setting details as follows: incoming thickness 1.0mm, steel elongation set value 1.1%; incoming thickness 1.2mm, steel elongation set value 1.3%; before production, the flat liquid nozzle inspection, the middle of the steel emulsion nozzle shall not exist the phenomenon of blockage, flat number 5-6, to ensure that the flat liquid injection to the full coverage of the plate; flat liquid concentration control to 3.0%-5.0%, the steel grade when the steel coil in the middle of the flat liquid injection flow increased by 20%-30%; blow-sweeping jet pressure > 0.47MPA, blow-sweeping angle control value 45°~60°, blow-sweeping device strictly prohibited from the phenomenon of air leakage; flat liquid must be injected to the upper and lower work roll gap, before production of special steel coil, 3-5 rolls in advance to adjust the flat liquid nozzle, to ensure the uniformity of flat liquid injection; steel coil winding strictly prohibited from the edge defect; normal production speed control to 500-700m / min, to improve the cleanliness of the steel plate surface, after the end of the strip, directly to the speed of 500m / min, strictly prohibited in the middle of the speed, to reduce the amount of steel coil head and tail flat liquid spot defects; flat rolling unit according to the micro wave control, strictly prohibited from the edge wave defect, to reduce the edge drop; when producing this steel grade, the flat rolling unit work roll roughness control in 2.0±0.1μm, steel coil roughness control to 0.8-1.3μm; 9) Design and control of the process parameters of the recoiling unit: The recoiling and straightening roll system and the oiling chamber of the oiling machine are cleaned three times a week. The rotating roll system, especially the roll surface of the straightening machine and the deburring roll, is scrubbed before the production of this steel grade. Pay attention to the scrubbing of the marks on the wide and narrow parts of the roll surface. At least 6 ordinary steel coils with a width of 1250mm or more are produced before the production of this steel grade. The centering accuracy of the coil loading is controlled to ±5mm. The cutting edge of the new disc shear is replaced before production, and rust-proof oil is applied to the cutting edge. The replacement frequency of the disc shear is 2000 tons, and the correction accuracy of the disc shear is controlled to ±2mm. The production speed of the recoiling unit is controlled to 50-200m / min. The oiling amount is controlled to 0.25g / m 2 during production according to the requirements of the contract. The speed is immediately increased after the threading is completed. It is strictly prohibited to run at a speed below 50m / min for a long time. The oiling effect of the oiling machine is checked and confirmed before production. The voltage of the upper knife beam of the oiling machine is controlled to 60-70KV, and the voltage of the lower knife beam is controlled to 65-75KV. The head and tail of the steel coil are cut off cleanly for 30m each during production. The sampling of the recoiling unit is along the plate width direction, 20mm, 50mm, and 1 / 4 of the edge, and the average thickness of the barrel is controlled to 1.0±0.015mm. The average thickness of the barrel cover is controlled to 1.19±0.02mm. The surface reflectivity of the strip of the recoiling unit is greater than or equal to 70%. The toilet paper is 400 square centimeters, and the toilet paper is ash-colored. Considering the thickness reduction caused by the straightening shrinkage of the recoiling unit, the overall design of this steel grade is to compensate 0.01mm of thickness for the recoiling.