A high-precision same-plate difference control method for an ultra-thick 441 stainless steel cold plate

Abstract

The application is a high-precision same-plate difference control technology for an ultra-thick specification (greater than 3.0 mm) 441 stainless steel cold plate. Through the development of a rolling load distribution system, a plate shape control strategy and a roller matching system for high-precision same-plate difference control, the same-plate difference of the thick specification 441 cold plate can be effectively controlled, the transverse thickness precision and the longitudinal thickness precision deviation are both less than or equal to 1%, the use requirements of users can be met, the market is successfully opened, and the ton steel profit is more than 2000 yuan.

Description

Technical Field

[0001] This invention relates to the field of steel rolling production technology, and in particular to a high-precision method for controlling the same plate difference of ultra-thick 441 stainless steel cold-rolled plates. Background Technology

[0002] Extra-thick (>3.0mm) ultra-pure ferritic 441 stainless steel cold-rolled sheets are mainly used in automotive engine flanges and related products, and are currently entirely dependent on imports as they cannot be produced domestically. Taiyuan Iron & Steel Co., Ltd. (TISCO) faces production difficulties due to limitations in its cold rolling mill production line design, and has not yet developed related products. In the past two years, with the upgrading of product demands from end users, the demand for related products has gradually increased, resulting in numerous inquiries. To break the import restriction and enhance the influence and competitiveness of TISCO products, it is essential to develop supporting process technologies for ultra-pure steel thick-gauge cold-rolled sheets and establish supply capabilities.

[0003] After replacing imports, the efficiency increase per ton of steel can reach more than 2,000 yuan.

[0004] Since ultra-thick 441 cold-rolled steel plates are generally used in high-end parts such as automotive engine flanges, the dimensional accuracy of the material, especially the difference between the same plate and the same strip, is very important. The difference between the same plate and the difference between the same strip must be ≤1%, that is, the thickness deviation of any point on the plate must be within 1%.

[0005] Due to limitations in absolute deformation, the deformation rate of ultra-thick cold-rolled steel sheets is relatively small, ranging from 30% to 50%, with the same-sheet variation typically between 1% and 2%. Therefore, it is necessary to develop relevant same-sheet variation control technologies to meet the needs of high-end users.

[0006] The implementation of this invention lies in the precise control of the same plate difference of ultra-thick 441 cold-rolled steel plates (>3.0mm), which meets the stringent requirements of users for this product and ultimately opens up the market. Summary of the Invention

[0007] The purpose of this invention is to address the above-mentioned problems by providing a high-precision method for controlling the same plate difference in ultra-thick 441 stainless steel cold-rolled plates.

[0008] The purpose of this invention is achieved as follows: a high-precision same-plate difference control method for ultra-thick 441 stainless steel cold-rolled plates, including the following three aspects: (1) rolling load distribution system for high-precision same-plate difference control: 7 to 9 passes of rolling are adopted, the total deformation is 40 to 50%, and the deformation of each pass is controlled between 6 and 13%; (2) plate shape control strategy for high-precision same-plate difference control: when the cold rolling mill rolls, the first three passes adopt the "M" shaped plate shape target curve, the edge I unit is controlled between -30 and -50, the middle I unit is controlled between -10 and -5, and the middle is used to reduce the convexity of the hot plate; the last three passes adopt the "N" shaped plate shape target curve, the edge I unit is controlled between -5 and -15, and the middle passes also adopt the "N" shaped plate shape target curve, the edge I unit is controlled between -15 and -30; (3) roll system matching system for high-precision same-plate difference control: the work rolls must be replaced in the first pass, the fourth pass, and the penultimate pass.

[0009] (3) The crown of the working rolls used in the first, fourth and penultimate passes are 0.22~0.28mm, 0.12~0.18mm and 0.07~0.13mm respectively.

[0010] The beneficial effects of this invention are: the implementation of this invention can effectively control the same plate difference of 441 cold-rolled steel plate with thicker specifications, and measure the same plate difference and same strip difference of finished cold-rolled steel plate, with good thickness accuracy and accuracy deviation ≤1%.

[0011] This project successfully developed ultra-thick, ultra-pure ferritic cold-rolled steel plates, opening up a niche market for the company with a capacity of approximately 5,000 tons per year and promising development prospects. Furthermore, the product has high added value, increasing efficiency by over 2,000 yuan per ton of steel. Attached Figure Description

[0012] The present invention will now be further described with reference to the accompanying drawings.

[0013] Figure 1 "M" shaped plate target curve diagram.

[0014] Figure 2 "N"-shaped plate-type target curve diagram. Detailed Implementation

[0015] This invention develops a high-precision same-plate thickness difference control technology for ultra-thick 441 cold-rolled steel sheets. Applied to a 20-roll mill, it effectively controls the same-plate thickness difference of thick 441 cold-rolled steel sheets, with both transverse and longitudinal thickness accuracy deviations ≤1%. This meets the needs of high-end users, successfully opening up the market and generating profits of over 2000 yuan per ton of steel. The technology includes the following three aspects: 1. A rolling load distribution system for high-precision same-plate thickness difference control. To improve dimensional accuracy and facilitate plate shape control, the 20-roll mill employs a larger total deformation and smaller per-pass deformation, using multi-pass rolling. The total deformation must not be less than 40%, controlled between 40% and 50%. The per-pass deformation must not exceed 13%, controlled between 6% and 13%. The number of rolling passes must not be less than 7, controlled between 7 and 9.

[0016] 2. Plate shape control strategy for high-precision plate shape difference control. During cold rolling, the first three passes use an "M"-shaped plate shape target curve, with the edge I unit controlled between -30 and -50, and the middle I unit controlled between -10 and -5, to reduce the hot plate crown. The last three passes use an "N"-shaped plate shape target curve, with the edge I unit controlled between -5 and -15 to control plate straightness. The middle passes also use an "N"-shaped plate shape target curve, with the edge I unit controlled between -15 and -30 for a smooth transition. Ideally, automatic control should be used for plate shape control to minimize fluctuations.

[0017] 3. Roller system matching system for high-precision same-plate difference control. In order to match the plate shape control strategy, the work rolls must be changed in the first, fourth, and penultimate passes, with corresponding work roll crowns of 0.25mm, 0.15mm, and 0.10mm, respectively. Example 1

[0018] It has already been implemented at the stainless steel cold rolling mill of Taiyuan Iron & Steel Co., Ltd.

[0019] This invention, implemented since 2022, has successfully developed and applied a complete cold-rolling production process for ultra-thick 441 cold-rolled steel sheets, resulting in an efficiency increase of over 2,000 yuan per ton of steel, totaling 320,000 yuan. The product exhibits excellent same-plate variation, measured at less than 1%, successfully opening up the high-end automotive flange market segment with promising development prospects. Combined with Taiyuan Iron & Steel's equipment advantages, it holds a unique position in China, enabling rapid import substitution and market share capture.

[0020] The developed specification is 5.0*1550mm, and its rolling parameters are as follows: 1. Rolling load distribution: raw material thickness 9.0mm, finished product thickness 5.0mm, rolling 7 passes, with a maximum deformation of 12.1% and a minimum of 6.5% per pass.

[0021] 2. Plate Shape Control Strategy: The first three passes use an "M" shaped plate shape target curve, with an edge I unit of -40 and a middle I unit of -10. The last three passes use an "N" shaped plate shape target curve, with an edge I unit of -10. The middle pass also uses an "N" shaped plate shape target curve, with an edge I unit of -20.

[0022] 3. Roller system configuration: For the first roll change, the working roll crown is 0.25mm; for the fourth roll change, the working roll crown is 0.15mm; for the penultimate roll change (sixth roll), the working roll crown is 0.1mm.

[0023] The finished product's thickness accuracy is good, with all accuracy deviations ≤1%. Example 2

[0024] The developed specification is 4.0*2050mm, and its rolling parameters are as follows: 1. Rolling load distribution: raw material thickness 8.0mm, finished product thickness 4.0mm, 9 rolling passes, maximum deformation per pass is 11.3%, minimum is 6.3%.

[0025] 2. Plate Shape Control Strategy: The first three passes use an "M" shaped plate shape target curve, with an edge I unit of -30 and a middle I unit of -10. The last three passes use an "N" shaped plate shape target curve, with an edge I unit of -5. The middle pass also uses an "N" shaped plate shape target curve, with an edge I unit of -15.

[0026] 3. Roller system configuration: For the first roll change, the working roll crown is 0.25mm; for the fourth roll change, the working roll crown is 0.15mm; for the penultimate roll change (eighth roll), the working roll crown is 0.1mm.

[0027] The finished product's thickness accuracy is good, with all accuracy deviations ≤1%.

[0028] 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 high-precision control of the same-plate difference in ultra-thick 441 stainless steel cold-rolled plates, characterized in that: This includes the following three aspects: (1) Rolling load distribution system for high-precision same plate difference control: 7 to 9 passes of rolling are used, the total deformation is 40 to 50%, and the deformation of each pass is controlled between 6 and 13%. (2) Plate shape control strategy for high-precision plate difference control: When rolling in a cold rolling mill, the first three passes adopt an "M" shaped plate shape target curve, with the edge I unit controlled between -30 and -50, and the middle I unit controlled between -10 and -5. The last three passes adopt an "N" shaped plate shape target curve, with the edge I unit controlled between -5 and -15. The middle passes also adopt an "N" shaped plate shape target curve, with the edge I unit controlled between -15 and -30. (3) Roller system matching system for high-precision same plate difference control: the working rolls must be replaced in the first, fourth and penultimate passes.

2. The method for high-precision same-plate difference control of ultra-thick 441 stainless steel cold-rolled plate according to claim 1, characterized in that: (3) The crown of the working rolls used in the first, fourth and penultimate passes are 0.22~0.28mm, 0.12~0.18mm and 0.07~0.13mm respectively.

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