A method for controlling the shape of a high-strength steel 630 plate rolled by a 20-roller rolling mill

Abstract

The present application relates to a wide high-strength 630 stainless steel cold rolling process, a twenty-roller mill rolling high-strength steel 630 shape control method according to the existing 630 production process, by optimizing the production process, under the existing process conditions, increase a rolling process again. From the original rolling-cold line-drawing straightening-factory process, optimized as rolling-cold line-drawing straightening-rolling-cold line degreasing-factory. The newly added last rolling process is improved by means of minimum deformation + special control shape, and the process of improving the shape is achieved under the condition of basically no thickness reduction.

Description

Technical Field

[0001] This invention relates to a cold rolling process for wide-width, high-strength 630 stainless steel, primarily using a 20-roll oil mill, specifically a method for controlling the shape of the rolled sheet using a 20-roll oil mill. Background Technology

[0002] Taiyuan Iron & Steel Group's (TISCO) high-strength steel 630 has a tensile strength of 1000 MPa, making it the hardest stainless steel currently available. Due to its high tensile strength, controlling the sheet shape is extremely difficult. Currently, users require a flatness of no more than 3mm for cold-rolled 630 steel, twice the 6mm requirement for hardened steel plates used in passenger vehicles. Following the normal production process of rolling mill-cold line-straightening-shipment, the product qualification rate is around 50%, resulting in high production costs and a low contract fulfillment rate. Furthermore, there is currently only one specification of 630 high-strength steel available. If the finished sheet shape does not meet the requirements, and there are no other contracts, scrap steel will ultimately be delivered, leading to a high scrap rate. See... Figure 1 This invention addresses the plate shape problem through theoretical analysis and improved rolling process design, successfully solving the problem.

[0003] This invention designs and implements a method for controlling the shape of 1500mm wide high-strength 630 stainless steel plates rolled by a 20-roll mill, opening up new avenues for cold rolling, improving the level of plate shape control, and reducing the defect rate. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned problems by providing a method for controlling the shape of high-strength steel 630 plates rolled by a 20-roll mill.

[0005] The purpose of this invention is achieved as follows: a method for controlling the shape of 630 high-strength steel rolled by a 20-roll mill, comprising the following aspects: (1) Deformation per pass: the deformation per pass is distributed according to the principle of gradual reduction, with the deformation of the first pass controlled to 10% to 15%, the deformation of the second pass controlled to 5% to 8%, the deformation of the intermediate passes controlled to 3% to 7%, the deformation of the pass before the finished product controlled to 2% to 4%, and the deformation of the pass after the finished product controlled to 1% to 3%; (2) Tension setting: the rolling tension setting is given according to the principle of equal tension rolling, with the tension value of the first pass before the first pass being 50 to 60 KN, the tension value of the second pass being 20 to 40 KN, the tension values ​​of the intermediate passes before and after the first pass being 50 to 60 KN, and the tension values ​​of the pass before and after the finished product being 55 to 60 KN; (3) Roller system configuration and target shape curve: the shape curve of the first pass adopts a concave curve on both sides, with the shape curve value on both sides being 0 to 5 N / mm. 2 The intermediate plate thickness is 2-8 N / mm. 2 The intermediate pass profile curve adopts a concave curve on both sides, with profile curve values ​​ranging from -10 to 5 N / mm. 2 The intermediate plate shape value is 0-10 N / mm. 2The finished product pass profile curve adopts a concave curve on both sides, with a profile curve value of -20 to -15 N / mm on both sides. 2 The intermediate plate shape value is controlled to 5-10 N / mm. 2 (4) Use of rolling mill rolls.

[0006] (4) The specific use of rolls is as follows: rolls with a roughness of 0.8-1.0μm are used for the first three passes, rolls with a roughness of 0.3-0.5μm are used for the intermediate passes, and rolls with a roughness of 0.2-0.35μm are used for the finished product passes.

[0007] The beneficial effects of this invention are: this invention opens up a new approach to cold rolling, improves the level of sheet shape control, reduces the rate of downgraded high-strength 630 stainless steel caused by poor sheet shape, and this invention is highly operable and is widely applicable to twenty-roll mills.

[0008] 1. Calculated based on a price difference of 10,000 yuan / ton between genuine and scrap steel. 2. Monthly contract volume for high-strength steel 630 is 100 tons, calculated based on a 20% increase in the pass rate (70% - 50%). 3. Monthly economic benefit increase: 100 tons * 20% * 10,000 yuan / ton = 200,000 yuan / month. Annual economic benefit increase: 200,000 yuan / month * 12 months / year = 2,400,000 yuan / year. Attached Figure Description

[0009] The present invention will now be further described with reference to the accompanying drawings.

[0010] Figure 1 This is a schematic diagram of the intermediate cone length parameter and cone height of the present invention.

[0011] Figure 2 This is the target curve diagram of the finished product pass plate shape of the present invention. Detailed Implementation

[0012] After being rolled into finished products, the steel sheet shape changes after cold line annealing. This shape is then further improved using online straightening equipment. However, due to insufficient precision in controlling the shape of thin, high-strength steel sheets, the final shape is unsatisfactory, resulting in a very low pass rate. The roll cooling effect is generally poor. Under normal process conditions, the rolls experience significant thermal expansion, causing convexity in the middle roll section. This results in high stress in the center of the strip and low stress on the sides, leading to rib-like defects and poor sheet shape after rolling.

[0013] To achieve the rolling of 1500mm wide, high-strength 630 stainless steel using a 20-roll mill, while ensuring a straight product shape and high yield, this invention optimizes the rolling process through roll system configuration, pass reduction distribution, rolling tension adjustment, and roll usage.

[0014] 1. Pass Deformation: The reduction schedule is the core of steel rolling, closely related to shape control and rolling success rate. Significant springback occurs after work hardening. The principle for distributing pass deformation is a gradual decrease. The first pass deformation should be controlled at 10%–15%; the second pass at 5%–8%; intermediate passes at 3%–7%; passes before finished product at 2%–4%; and passes after finished product at 1%–3%.

[0015] 2. Tension Setting: Rolling tension maintains the stability of the rolling process and is also a strong guarantee for good sheet shape. During rolling, the rolls undergo significant thermal expansion. To ensure good sheet flatness, the initial tension is increased sequentially with each pass, without exceeding 50% of the material's yield strength. The total tension before and after each pass reaches a maximum value of 60 N / mm. 2 The rolling tension setting principle is based on the principle of equal tension rolling. The tension value before the first pass is 50-60 kN, the tension value after the first pass is 20-40 kN, the tension value before and after the intermediate passes is 50-60 kN, and the tension value before and after the finished pass is 55-60 kN.

[0016] 3. Roll System Configuration and Target Strip Shape Curve: To balance the rolling pressure between the middle and edge areas of the strip and avoid excessive pressure in the middle that could result in poor strip shape, the two intermediate free rolls of a 20-roll mill must be flat rolls with no convexity. The roll system configuration and target strip shape curve must all adopt straight strip shape curves, and the finished pass strip shape curve should adopt... Figure 2 The target curve shape is shown. The plate shape curve values ​​for the first and intermediate passes are taken as 0-5 N / mm on both sides. 2 The intermediate plate thickness is 2-8 N / mm. 2 The plate profile curve value for intermediate passes is 5 to -10 N / mm on both sides. 2 The intermediate plate shape value is 0-10 N / mm. 2 The finished product's profile curve adopts a downward curve on both sides of the first pass, with a profile curve value of -15 to -20 N / mm on both sides. 2 The intermediate plate shape value should be controlled to 5-10 N / mm. 2 .

[0017] 4. Roll Usage: Two intermediate rolls with upper and lower free rolls for 50 passes, and one intermediate cone roll with a length of 200mm and a cone height for 40 passes. The rolling pressure is high in the first few passes; to prevent slippage and maintain good rolling stability, rolls with a surface roughness of 1.0μm must be used for the first three passes. For the finishing passes, to ensure the surface quality of the steel strip, rolls with a surface roughness of 0.2-0.35μm are used.

[0018]

[0019] Since its implementation six months ago, this program has improved the yield rate of high-strength steel 630 by using minimum deformation rolling on the No. 12 rolling mill, combined with special plate shape control technology. The yield rate of the high-strength steel 630 has increased from 50% to approximately 70%, an improvement of over 20%. Contract fulfillment rate has increased, while scrap rate has also decreased significantly, resulting in substantial economic benefits.

[0020] Results: High-grade non-oriented silicon steel rolled products have good sheet shape, no rib stripes, and a flat surface.

[0021] The above description is only a specific embodiment of the present invention, but the structural features protected by the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A method for controlling the shape of high-strength steel 630 sheet rolled on a 20-roll mill, characterized in that: Including the following aspects: (1) Deformation amount per pass: The principle of distribution of deformation amount per pass is to gradually decrease, with the deformation amount of the first pass controlled to 10% to 15%, the deformation amount of the second pass controlled to 5% to 8%, the deformation amount of the intermediate passes controlled to 3% to 7%, the deformation amount of the passes before the finished product controlled to 2% to 4%, and the deformation amount of the passes before the finished product controlled to 1% to 3%; (2) Tension setting: The principle of setting the rolling tension is given according to the principle of equal tension rolling. The tension value before the first pass is 50-60KN, the tension value after the first pass is 20-40KN, the tension value before and after the intermediate passes is 50-60KN, and the tension value before and after the finished pass is 55-60KN. (3) Roller system configuration and target plate shape curve: The plate shape curve of the first pass adopts a concave curve on both sides, and the plate shape curve value on both sides is 0~5N / mm. 2 The intermediate plate thickness is 2-8 N / mm. 2 The intermediate pass profile curve adopts a concave curve on both sides, with profile curve values ​​ranging from -10 to 5 N / mm. 2 The intermediate plate shape value is 0-10 N / mm. 2 The finished product pass profile curve adopts a concave curve on both sides, with a profile curve value of -20 to -15 N / mm on both sides. 2 The intermediate plate shape value is controlled to 5-10 N / mm. 2 ; (4) Roll usage: Rolls with a roughness of 0.8-1.0μm are used for the first three passes, rolls with a roughness of 0.3-0.5μm are used for the intermediate passes, and rolls with a roughness of 0.2-0.35μm are used for the finished product passes.

Images