Method for improving width control precision through rough rolling pass change

Abstract

The invention discloses a method for improving width control precision by using rough rolling pass change, which comprises the following steps of: adding a simple width gauge before a heating furnace enters the furnace, measuring the actual width of a plate blank, calculating the corresponding cold-state average width of the plate blank according to the actually measured temperature of the plate blank, and taking the width as a reference value for model calculation; meanwhile, the most important control factor width reduction amount is obtained, wherein the width reduction amount = the actually measured width of the plate blank minus the control width of the finished product; finished product control width = finished product target width + user tolerance / 2; according to the classic width reduction Goracle OKADO law, under the condition that distortion is not generated, the rolling reduction of each pass of the vertical roll is made to be the maximum, according to the theoretical calculation condition, the maximum side pressure capable of being reached by each pass under the condition of different times under different control layers is found out, and therefore a strategy table of the maximum side pressure of the vertical roll is formed.

Description

Technical Field

[0001] The present invention discloses a method for improving width control accuracy by changing rough rolling passes. Background Art

[0002] In a hot strip rolling production line, width control is mainly achieved in the rough rolling area. The conventional method is to obtain the target width of the intermediate slab based on the target width and the width spread in finish rolling, and then set the side pressure of the vertical rolls for each pass accordingly in combination with the width of the incoming slab. Since the width control accuracy of the slabs produced by steelmaking continuous casting is poor and it is not suitable for frequent width changes, sometimes when producing slabs of the same target width, due to different reasons such as casting speed, their actual widths will also have large differences. The width of the incoming slabs from steelmaking is considered normal within the range of -10 to +20 mm of the target value, and its hot state cannot be effectively measured and controlled either; while there are many target widths in hot rolling, this results in the need to use the same slab width to produce strip steels of multiple target widths, increasing the difficulty of width control. Especially in some production lines with a single rough rolling stand, the width accuracy is relatively low.

[0003] Through literature retrieval, it is found that there are many research literatures on width control at home and abroad, forming a classic theory on width control, such as the smaller the width spread with more rolling passes, the larger the width spread with a narrower slab, etc., which has been verified in production practice; for the problems of slabs and target widths, methods such as adding a sizing press, adding on-line width adjustment in steelmaking, and improving the width accuracy of slabs are proposed, but all require large investments and renovations and cannot quickly and effectively solve the problems.

[0004] Through retrieval, the following related patents are found: 1. Zhang Jianmin, Li Weigang, Shen Jihai, Zhang Xiaofeng. A comprehensive adaptive control method for the width of rough rolled strip steel, Chinese Patent: CN201310390071.2; 2. Qin Hongbo, Zhou Zheng, Huang Shuang, Xu Fang, Shi Jinfang, Zheng Wei. A method for controlling the rough rolling reduction load distribution and a rough rolling control system. Chinese Patent: CN201610749590.7. 3. Xing Lijun, Liu Miao, Li Jian; A method for controlling the width of rough rolled strip steel, Chinese Patent: CN201310014834.3. There are currently many domestic patents on width control, but most of them are about optimizing width control through various detection methods and self-learning methods, and those related to rough rolling passes are all related to optimizing the rough rolling flat roll load distribution, etc., and the content of using rough rolling passes for width control is not involved.

[0005] The research team of the present invention has not found an effective solution to the problem of excessive fluctuations in the width of incoming slab, and the original control strategy cannot effectively control the width. The research team of the present invention combines the classical width control theory of hot rolling, analyzes and calculates the incoming slab situation and the finished product target situation in the case of a single-stand roughing mill, sets corresponding control levels in the control model, and uses different pass controls to achieve the purpose of improving the width control accuracy. At the same time, the corresponding speed, cooling water, short stroke, and self-learning are also stratified and optimized to ensure that other aspects are not affected by the pass change, which is also the unique feature of the present invention. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for improving the width control accuracy by using the change of roughing passes. Through the present invention, the problems of large fluctuations in the width of incoming slabs of a hot rolling single-stand roughing mill and poor width control accuracy when there are many finished product target widths are solved, and at the same time, other production efficiency and quality problems are not caused.

[0007] The technical solution adopted by the present invention is a method for improving the width control accuracy by using the change of roughing passes. Specific practices: 1. Add a simple width gauge before the slab enters the heating furnace to measure the actual width of the slab, calculate the corresponding cold-state average width of the slab according to the measured temperature of the slab, and use this width as the reference value for model calculation; at the same time, obtain the most important control factor of the present invention, the width reduction amount: width reduction amount = measured width of the slab - controlled width of the finished product; controlled width of the finished product = target width of the finished product + user tolerance / 2; 2. According to the classical width reduction law of Okado: without distortion, the maximum reduction amount per pass of the vertical roll is mainly dependent on the width-thickness ratio of the rolled piece. Curve A gives the maximum width reduction rate that may occur without distortion. The width reduction rate corresponding to partial distortion is in the region between Curve A and Curve B. When the width reduction rate exceeds the data determined by Curve B, complete distortion will occur;

[0008] The parameters of the above calculation model are as follows: w0 is the inlet width before vertical roll rolling; h0 is the inlet thickness before vertical roll rolling; d e,max Maximum reduction amount; f lim Correction coefficient; addTol: [%] change of Okado curve; λ width reduction factor 0 ≤ λ ≤ 1; d e Width reduction amount; According to the above theoretical calculation and combined with the actual production performance, analyze each factor that affects the width, and use the factor with the greatest impact as the input item for model stratification, which is determined as: steel grade, slab thickness, slab width, width reduction, finished product thickness; find out the maximum side pressure that can be achieved in each pass when there are different numbers of passes in different control levels. If the side pressure exceeds this value, width deviation or uniformity problems will occur, thus forming a strategy table for the maximum side pressure of the vertical rolls. ; a. Analyze the previous production data, calculate all the steel grade specifications produced according to the initial 5 passes, sort out the steel grade specifications for which the side pressure of all vertical rolls needs to exceed the maximum side pressure of the vertical rolls to reach the target width, re - formulate the rough rolling pass number, and change the original 5 - pass to 7 - pass.

[0009] b. Optimize other control strategies for the control levels with pass number changes, such as speed strategy, reduction strategy, and temperature control strategy.

[0010] c. Conduct production tracking on the optimized strategies, and promote them to similar control levels after they are normal.

[0011] The technical principle of the present invention: within the range allowed by the equipment capacity, the more passes in rough rolling, the smaller the spread, and the fewer passes, the larger the spread. When the width reduction (the deviation between the measured width of the slab incoming material and the target width) is large, especially when it exceeds the width uniformity capacity range of a single - stand with fewer passes, more passes are used for production to ensure the width; when the slab widths are different, their spreading capabilities are different, and the pass strategies are designed according to different slab widths; after the number of passes increases, the load on the rough rolling flat rolls decreases, and the production efficiency and temperature effects caused by the increase in the number of passes are compensated by increasing the speed. The present invention realizes the purpose of improving width accuracy by reasonably stratifying the measured widths of different slab incoming materials and the width reduction, setting different model strategy control levels, and setting rolling passes, side pressure, reduction ratio, rolling speed, cooling conditions, etc. through different control levels.

[0012] After the implementation of the present invention, through reasonable layering and adopting different control pass strategies according to different slab feeding conditions, the width accuracy is significantly improved, and the width block is reduced from about 0.7% in the early stage to about 0.4%; after the implementation of the present invention, when adopting different rough rolling pass strategies, at the same time, by adjusting and optimizing control strategies such as temperature, descaling, and speed, the physical quality fluctuation of the strip steel is not caused by the pass change brought about by the slab feeding fluctuation; after the implementation of the present invention, the width control requirement for the slab feeding is enlarged, and the steelmaking production capacity release is improved to a certain extent; it can be implemented in a hot rolling production line where the slab feeding width fluctuates greatly and the width reduction ability of the rough rolling mill is relatively insufficient. After the implementation of the present invention, its width control ability can be improved and there will be no other negative impacts on production capacity and quality. Embodiment

[0013] A method for improving width control accuracy by using rough rolling pass changes Specific practices: 1. Add a simple width gauge before the reheating furnace to measure the actual width of the slab, calculate the corresponding cold-state average width of the slab according to the measured slab temperature, and use this width as the reference value for model calculation; at the same time, obtain the most important control factor of the present invention, the width reduction amount: width reduction amount = measured slab width - finished product control width; finished product control width = finished product target width + user tolerance / 2; 2. According to the classical width reduction Okado's law: without distortion, the maximum reduction amount of each pass of the vertical roll can be achieved, which mainly depends on the width-thickness ratio of the rolled piece. Curve A gives the maximum width reduction rate that may occur without distortion. The width reduction rate corresponding to partial distortion is in the area between Curve A and Curve B. When the width reduction rate exceeds the data determined by Curve B, complete distortion will occur;

[0014] The parameters of the above calculation model are as follows: w0 is the inlet width before vertical roll rolling; h0 is the inlet thickness before vertical roll rolling; d e,max Maximum reduction amount; f lim Correction coefficient; addTol: Okado curve change [%]; λ width reduction factor 0 ≤ λ ≤ 1; d e Width reduction amount; According to the above theoretical calculation situation and combined with the production actual situation, analyze each factor that affects the width, and use the factor with the greatest influence as the input item for model layering, which is determined as: steel type, slab thickness, slab width, width reduction amount, finished product thickness; find out the maximum side pressure that can be achieved in each pass when there are different pass numbers under different control levels. If the side pressure exceeds this value, width out-of-tolerance or uniformity problems will occur, thus forming a vertical roll maximum side pressure strategy table. ; a. Analyze the previous production data, calculate all the steel grades produced according to the initial 5 passes, sort out the steel grade specifications for which the side pressure of all vertical rolls needs to exceed the maximum side pressure of the vertical rolls to reach the target width, re - formulate the rough rolling pass number, and change the original 5 - pass to 7 - pass;

[0015] b. Optimize other control strategies at the control level with pass number changes, including speed strategy, reduction strategy, and temperature control strategy;

[0016] c. Conduct production tracking on the optimized strategies, and promote them to similar control levels after they are normal.

Claims

1. A method for improving the width control accuracy by using the rough rolling pass change, characterized in that: Specific practice: 1). Add a simple width gauge before the reheating furnace to measure the actual width of the slab, calculate the corresponding average cold width of the slab according to the measured temperature of the slab, and use this width as the reference value for model calculation; at the same time, obtain the most important control factor of the present invention, the width reduction amount: width reduction amount = measured width of the slab - finished product control width; finished product control width = finished product target width + user tolerance / 2; 2). According to the classical width reduction Okado's law: without causing distortion, to maximize the reduction amount of each pass of the vertical roll, which mainly depends on the width-thickness ratio of the rolled piece. When the width reduction rate exceeds the data determined by curve B, complete distortion will occur; ； The parameters of the above calculation model are as follows: w0 vertical roll rolling entrance width; h0 vertical roll rolling entrance thickness; d e,max Maximum compression; f lim Correction coefficient; addTol: OKADO curve change [%]; λ width reduction factor 0 ≤ λ ≤ 1; d e Width reduction amount; According to the above theoretical calculation situation and combined with the production actual situation, analyze each factor that affects the width, and use the factor with the greatest influence as the model hierarchical input item, which is determined as: steel grade, slab thickness, slab width, width reduction amount, finished product thickness; find out the maximum side pressure that can be achieved for each pass under different pass numbers in different control levels. If the side pressure exceeds this value, width out-of-tolerance or uniformity problems will occur, thus forming a vertical roll maximum side pressure strategy table. ； a. Analyze the previous production data, calculate all the steel grade specifications produced according to the initial 5 passes, sort out the steel grade specifications for which the side pressure of all vertical rolls needs to exceed the maximum side pressure of the vertical roll to reach the target width, re-determine the rough rolling pass number, and change the original 5 passes to 7 passes; ； b. Optimize other control strategies for the control levels with pass changes, optimize the speed strategy, reduction strategy, and temperature control strategy; ； c. Conduct production tracking on the optimized strategy, and promote it to similar control levels after it is normal.

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