Production method of hot-rolled pickled plate for automobile
By optimizing the rolling cycle, heating process and leveling unit process, the surface quality problem of hot-rolled pickled plates for automobiles is solved, efficient production and reduced defect rate and reduced production costs.
Patent Information
- Application Number
- CN202510750639.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-06
- Publication Date
- 2025-07-18
AI Technical Summary
The prior art cannot effectively solve the surface quality defects of hot-rolled pickled plates for automobiles, especially quality defects such as shavings and scratches, resulting in a high degradation rate and affecting production progress and costs.
Optimize the rolling cycle, heating process, rolling process and leveling unit process, including controlling the furnace temperature, increasing the descaling water passage, replacing new work rollers, and checking the flatness of the roller surface to ensure the continuity of surface quality and high-standard production.
The defect rate of pickled plates is significantly reduced, especially quality defects such as erectile printing, bruising, and cross-folding printing. The downgrade rate reaches less than 5%, achieving continuous production of hot-rolled pickled plates for automobiles, reducing the increase in costs and capital occupation in the production link.
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of pickling plate production, and relates to a production method of hot-rolled pickling plates for automobiles. Background Art
[0002] As the highest level of pickled plates in the hot rolling mill pickling product series, hot rolled pickled plates for automobiles are supplied with "zero" surface defects, and the surface quality control level is equivalent to the requirements for automobile outer panels. A certain steel plant produces 1,000 to 3,000 tons of pickled plates per month. Different from conventional pickled products, the surface of pickled plates for automobiles is not allowed to have quality defects such as rubbing and scratching. From the perspective of the whole process of production, the production is difficult, and there is currently no complete production process in the industry.
[0003] Due to customer requirements and further tightening of standards for cold rolling judgment, the average monthly downgrade rate of various defects in hot-rolled pickled plates for automobiles reached 18% in January-March 2024, seriously affecting production progress. Summary of the invention
[0004] The purpose of the present invention is to provide a production method of hot-rolled pickled plates for automobiles, so as to increase the yield rate of the pickled plates and improve the surface quality of the pickled plates.
[0005] To achieve the above object, the present invention is implemented through the following technical solutions:
[0006] A method for producing hot-rolled pickled plates for automobiles, comprising:
[0007] 1) Rolling cycle:
[0008] The rolling cycle is 10 to 30 km;
[0009] Pickling plates with thickness > 2.03mm are centrally scheduled for production;
[0010] For pickled plates with a thickness of ≤2.03mm, the length of the slab is 7 to 8m;
[0011] Start rolling and transition materials in advance of the cycle to avoid scheduling cold-rolled ultra-low carbon steel;
[0012] 2) Heating:
[0013] Control the furnace temperature according to the lower limit of the target furnace temperature, and reserve space when loading the furnace before the roll change cycle of the working rolls of the hot-rolled pickled plate for automobiles;
[0014] If the time of the second heating section or soaking section in the furnace is ≥75 minutes, or the total time of the first heating section, the second heating section and the soaking section in the furnace is ≥200 minutes, all hot-rolled pickled plates for automobiles shall be returned to the furnace;
[0015] 3) Rolling:
[0016] The wasteland is put into at least 6 times of descaling water;
[0017] When pickled sheets with a thickness > 2.03 mm are rolled, intensive cooling is carried out after they are fed into the F1 mill.
[0018] 4) Skin pass mill:
[0019] New working rolls need to be replaced before production.
[0020] Uncoiling tension: 20 - 200 kN; coiling tension: 31 - 310 kN; head speed: 20 m / min; tail speed: 20 m / min; running speed: 30 - 400 m / min; rolling force does not exceed 5000 kN.
[0021] Check the flatness of the roll surface of the skin pass mill before skin passing; check the surface of the exit lower pinch roll every 6 - 8 pickled sheets produced.
[0022] 1) Among them, medium and low carbon pickled sheets with a thickness ≤ 2.03 mm are scheduled for production in a concentrated manner.
[0023] The transition material is of the same steel grade or Q235B sheet. The thickness difference between the starting material and the transition material and the pickled sheet is within 0.5 mm. Thin - gauge or extreme - gauge high - temperature steel and pipeline steel are not scheduled for production before and after the period of rolling pickled sheets with a thickness > 2.03 mm.
[0024] During the rolling process, rolling oil and roll gap water in each stand of the finishing rolling area are normally fed.
[0025] During the rolling process, when pickled sheets with a thickness ≤ 2.03 mm are rolled, it is not allowed to feed the width - setting press.
[0026] During the rolling process, the rolling rhythm ≥ 150 seconds / sheet, and the number of descaling points throughout the line is no more than 4.
[0027] During the rolling process, for pickled sheets with a thickness > 2.03 mm, double - row descaling water is fed for rough rolling descaling, double - row high - pressure descaling water is fed for finishing rolling descaling, and the rough rolling pass adopts 3 + 5, with 8 passes of descaling water fed.
[0028] During the rolling process, for pickled sheets with a thickness ≥ 3.0 mm and a width < 1400 mm, double - row descaling water is fed for rough rolling descaling, double - row high - pressure descaling water is fed for finishing rolling descaling, and the rough rolling pass adopts 3 + 5, with 8 passes of descaling water fed.
[0029] Replace new working rolls before skin passing.
[0030] As described in 4), when checking the surface of the exit lower pinch roll, if there are indentations on the roll surface, replace the exit lower pinch roll.
[0031] Compared with the prior art, the beneficial effects of the present invention are:
[0032] The method of the present invention optimizes the heating process. On the premise of reducing the furnace outlet temperature to ensure the surface quality, it meets the design requirements of the finishing rolling temperature. The skin pass process is optimized to improve the surface quality of the pickled sheet, especially the surface quality of electro-galvanized products. The total downgrading rate of various quality defects such as dents, bruises, and transverse creases on the pickled sheet is less than 5%.
[0033] Using the method of the present invention, the hot-rolled pickled sheet for automobiles can be continuously produced, reducing the cost increase caused by the idle consumption of the rolling mill such as shutdown and slow rolling rhythm. Due to the reduction of the defect rate, the delivery cycle of the whole product is shortened, the capital and resource occupation in the production process are reduced, and waste is avoided. Specific embodiments
[0034] The present invention will be described in detail below, but it should be noted that the implementation of the present invention is not limited to the following embodiments.
[0035] A production method of hot-rolled pickled sheet for automobiles:
[0036] 1. Requirements for rolling cycle:
[0037] The rolling cycle is arranged at 10 - 30 km;
[0038] For pickled sheets with a thickness ≤ 2.03 mm, the slab length is controlled at 7 - 8 m.
[0039] For pickled sheets with a thickness > 2.03 mm, centralized production scheduling is carried out, and it is strictly prohibited to mix and roll with thin-gauge pickled sheets with a thickness ≤ 2.03 mm;
[0040] Among pickled sheets with a thickness > 2.03 mm, low-carbon pickled sheets are centrally scheduled for production and not mixed and rolled with high-strength steel pickled sheets.
[0041] The production plan is smoothly transitioned, and the thickness difference is within 0.5 mm. Transition materials are transitioned with the same steel grade or Q235B. Thin-gauge or extreme-specification high-temperature steel and pipeline steel are not scheduled before and after the rolling cycle of pickled sheets with a thickness > 2.03 mm.
[0042] 2. Heating process
[0043] Furnace outlet temperature: Controlled according to the lower limit of the target furnace outlet temperature of the same steel grade and specification.
[0044] Time in the furnace:
[0045] To further shorten the time in the furnace, when loading the furnace for the hot-rolled pickled sheet for automobiles in a cycle, reserved spaces are provided. For example, when changing the finishing mill rolls for 15 minutes, 10 minutes of reserved space can be provided, and when conducting spot checks for 30 minutes, 20 minutes of reserved space can be provided.
[0046] If the residence time in the second heating section or soaking section is ≥ 75 minutes, or the total residence time in the first heating section, second heating section, and soaking section is ≥ 200 minutes, all the hot-rolled pickled sheets for automobiles are sent back to the furnace.
[0047] 3. Rolling Process
[0048] At least 6 passes of descaling water are input during rough rolling.
[0049] The rolling oil and roll gap water of each stand in the finishing rolling area are input normally.
[0050] For pickled sheets with a thickness > 2.03 mm, intensive cooling is carried out after they enter the F1 mill.
[0051] Pickled sheets with a thickness ≤ 2.03 mm are not allowed to enter the sizing press.
[0052] 4. Other Process Requirements
[0053] a) The rolling rhythm is controlled above 150 seconds / coil, and it is ensured that the number of descaling points throughout the line does not exceed 4 simultaneously.
[0054] b) Input of descaling water: When producing pickled sheets with a thickness > 2.03 mm, double-row descaling water is input during rough rolling descaling, double-row descaling water is input during finishing rolling descaling, the rough rolling passes adopt 3 + 5 (input 8 passes of descaling water), and intensive cooling after the F1 mill is input normally. When producing pickled sheets with a thickness ≤ 2.03 mm, on the premise of ensuring stable rolling, as much descaling water as possible is input.
[0055] c) The rolls for the F1 - F4 mills must use the high-speed steel rolls for the first time on the mill.
[0056] d) For the hot-rolled pickled sheets for automobiles SP540F:
[0057] e) Input of descaling water. When the thickness ≥ 3.0 mm and the width < 1400 mm, double-row descaling water is input during rough rolling descaling, double-row descaling water is input during finishing rolling descaling, the rough rolling passes adopt 3 + 5 (input 8 passes of descaling water), and intensive cooling after the F1 mill is input normally.
[0058] 5. Temper Mill Process
[0059] 1. Parameter Setting
[0060] Parameter item Setting Uncoiling tension 40 kN Coiling tension 200 kN Head speed 20 m / min Tail speed 20 m / min Running speed 150 m / min Rolling force Adjust according to the actual situation, with a maximum not exceeding 5000 kN
[0061] a) Before production, thoroughly clean the equipment in contact with the surface of the pickled sheet and the equipment above the pickled sheet where foreign matters such as iron filings and sludge may fall, and the final effect should meet the requirement that no falling objects affect the surface quality during the production process.
[0062] b) Before production, check the roller system of the leveling machine. There should be no raised parts on the roller surface, especially the outlet pinch roller, which is prone to rubbing. To avoid batch rubbing of the outlet pinch roller, this part needs to be checked once every 6 pickling plates are produced.
[0063] c) Before production, the working roller must be replaced with a new one. The surface of the working roller must be smooth and free of dirt and knife marks.
[0064] d) The temperature of the steel coil on the machine must be strictly implemented in accordance with the process requirements, and the temperature records must be kept.
[0065] e) Before threading, the head of the hot-rolled pickled strip needs to be pressed down by a straightening roller to make it tilt up, so as to avoid hitting the upper flat working roller and the lower pinch roller at the exit during threading, thereby avoiding marks caused by scratches on the roller surface.
[0066] f) After the exit reel bites the steel, the leveling roller should be lowered after sufficient tension is established to avoid relative displacement of the steel plate and the leveling roller, which may cause damage to the roller when starting the vehicle.
[0067] g) The machine stops automatically when there are 2 meters left at the tail of the steel plate to be thrown. When restarting, the operator manually rotates the lower working roll to make it run synchronously with the pickling plate to avoid roller scratches caused by the pickling plate moving while the working roll does not.
[0068] In addition, the surface quality requirements of hot-rolled pickled plates for automobiles are extremely high. The production line is controlled in accordance with the highest requirements in terms of production planning, working roll material, working roll cycle, billet burning temperature, process water input, etc., and the thin specifications of SP221 and SP440 steel grades account for a large proportion, which brings great difficulties to the production of the production line. This process enables the leveling unit to minimize downgraded products, which is also a great cost saving for the production line.
[0069] Example
[0070] 1. Rolling cycle requirements:
[0071] 10 pieces of Q235B as transition material for rolling, 15 pieces of pickled plates for automobiles, the cycle mileage is within 30km. The rolling thickness is 2.55*1250mm.
[0072] 2. Heating process
[0073] Oven temperature: 1180℃.
[0074] Time in the furnace:
[0075] Leave 10 minutes of space, the second heating section is in the furnace for 70 minutes, the soaking section is in the furnace for 71 minutes, and the total time the first heating section, the second heating section and the soaking section are in the furnace is 190 minutes.
[0076] 3. Rolling process
[0077] The wasteland was put into 8 passes to remove scale water.
[0078] The rolling oil and roll gap water of each stand in the finishing rolling area are normally added. After the F1 mill is put into use, a small amount of descaling water is added.
[0079] 4. Other processes
[0080] a) The rolling rhythm is controlled at above 155 seconds / block.
[0081] c) Descaling water input: double-row descaling water is input for rough rolling, double-row descaling is input for finishing rolling, 3+5 passes of rough rolling are adopted (8 passes of descaling water is input), and small descaling water is normally input after F1 machine.
[0082] d) F1~F4 rolling mill rolls are high-speed steel rolling mill rolls for the first time.
[0083] 5. Leveling unit process
[0084] 1. Parameter setting
[0085] Parameter item Setting Uncoiling tension 40 kN Coiling tension 200 kN Head speed 20 m / min Tail speed 20 m / min Running speed 150 m / min Rolling force Adjust according to the actual situation, with a maximum not exceeding 5000 kN
[0086] a) Before production, the equipment in contact with the surface of the pickling plate and the equipment on which foreign matter such as iron filings and oil sludge may fall from the pickling plate shall be thoroughly cleaned. The final effect shall meet the requirements of the "2250 Leveling Unit Clean Production Visualization Standard".
[0087] b) Before production, check the roller system of the leveling machine. There should be no raised parts on the roller surface, especially the outlet pinch roller, which is prone to rubbing. To avoid batch rubbing of the outlet pinch roller, this part needs to be checked once every 6 pickling plates are produced.
[0088] c) Before production, the working roller must be replaced with a new one. The surface of the working roller must be smooth and free of dirt and knife marks.
[0089] d) The temperature of the steel coil on the machine must be strictly implemented in accordance with the process requirements, and the temperature records must be kept.
[0090] e) Before threading, the head of the pickled strip needs to be pressed down by a straightening roller to make it tilt up, so as to avoid hitting the upper flat working roller and the lower pinch roller at the exit during threading, thereby avoiding marks caused by scratches on the roller surface.
[0091] f) After the exit reel bites the steel, the leveling roller should be lowered after sufficient tension is established to avoid relative displacement of the steel plate and the leveling roller, which may cause damage to the roller when starting the vehicle.
[0092] g) The machine stops automatically when there are 2 meters left at the tail of the steel plate to be thrown. When restarting, the operator manually rotates the lower working roll to make it run synchronously with the pickling plate to avoid roller scratches caused by the pickling plate moving while the working roll does not.
[0093] 6. Effect: There are no defects on the hot-rolled plate surface, and the qualified rate is 100%.
Claims
1. A production method of hot-rolled pickled sheet for automobiles, characterized in that, Including: 1) Rolling cycle: The rolling cycle is 10 - 30 km; Pickled sheets with a thickness > 2.03 mm are scheduled for centralized production; For pickled sheets with a thickness ≤ 2.03 mm, the slab length is 7 - 8 m; Avoid scheduling ultra-low carbon cold-rolled steel for the first-pass material and transition material before the cycle; 2) Heating: Control the tapping temperature according to the lower limit of the target tapping temperature, and reserve empty spaces when charging the furnace before the work roll changing cycle of hot-rolled pickled sheets for automotive use; If the residence time in the second heating section or soaking section is ≥ 75 minutes, or the total residence time in the first heating section, second heating section, and soaking section is ≥ 200 minutes, all hot-rolled pickled sheets for automotive use are sent back to the furnace; 3) Rolling: At least 6 passes of descaling water are input during rough rolling; When rolling pickled sheets with a thickness > 2.03 mm, intensive cooling is applied after the F1 mill; 4) Skin pass mill: New work rolls need to be replaced before production; Uncoiling tension: 20 - 200 kN; coiling tension: 31 - 310 kN; head speed: 20 m / min; tail speed: 20 m / min; running speed: 30 - 400 m / min; rolling force does not exceed 5000 kN; Check the flatness of the roll surface of the skin pass mill before skin passing; check the surface of the lower pinch roll at the exit every 6 - 8 pickled sheets produced.
2. The production method of a hot-rolled pickled sheet for automobiles according to claim 1, characterized in that In 1), medium and low carbon pickled sheets with a thickness ≤ 2.03 mm are scheduled for centralized production.
3. The production method of a hot-rolled pickled sheet for automobiles according to claim 1, characterized in that, The transition material is of the same steel grade or Q235B sheet. The thickness difference between the first-pass material and transition material and the pickled sheet is within 0.5 mm. Thin-gauge or extreme-specification high-temperature steel and pipeline steel are not scheduled for production before and after the cycle of rolling pickled sheets with a thickness > 2.03 mm.
4. The production method of a hot-rolled pickled sheet for automobiles according to claim 1, characterized in that, During the rolling process, rolling oil and roll gap water are normally input for each stand in the finish rolling area.
5. The production method of a hot-rolled pickled sheet for automobiles according to claim 1, characterized in that, During the rolling process, when rolling pickled sheets with a thickness ≤ 2.03 mm, it is not allowed to input the width sizing press.
6. The production method of a hot-rolled pickled sheet for automobiles according to claim 1, characterized in that, During the rolling process, the rolling rhythm ≥ 150 seconds / sheet, and the number of descaling points throughout the line is no more than 4.
7. The production method of a hot-rolled pickled sheet for automobiles according to claim 1, characterized in that, During the rolling process, for pickled sheets with a thickness > 2.03 mm, double-row descaling water is input for rough rolling descaling, double-row high-pressure descaling water is input for finish rolling descaling, and the rough rolling passes adopt 3 + 5, with 8 passes of descaling water input.
8. The production method of a hot-rolled pickled sheet for automobiles according to claim 1, characterized in that, During the rolling process, for pickled sheets with a thickness ≥ 3.0 mm and a width < 1400 mm, double-row descaling water is input for rough rolling descaling, double-row high-pressure descaling water is input for finish rolling descaling, and the rough rolling passes adopt 3 + 5, with 8 passes of descaling water input.
9. The production method of a hot-rolled pickled sheet for automobiles according to claim 1, characterized in that, Replace new work rolls before skin passing.
10. The production method of a hot-rolled pickled sheet for automobiles according to claim 1, characterized in that, Regarding the inspection of the surface of the lower pinch roll at the exit described in 4), if there are indentations on the roll surface, replace the lower pinch roll at the exit.