Control method for improving wedge precision through rolling load redistribution in hot rolling short process

Abstract

The invention provides a control method for improving wedge precision through rolling load redistribution in a hot rolling short process, which comprises the following steps: carrying out rolling mill load distribution by adopting a constant reduction rate mode: limiting the reduction rates of F1 and F2 racks to be fixed values, and calculating the reduction rates of F3-F7 racks by a secondary control system according to the fixed reduction rates of the F1 and F2 racks; redistribution of rolling load: after plate passing, comparing the actual rolling load of the last rack with a set load difference value, and when the deviation between the actual rolling force and the set rolling force reaches a force difference minimum effective proportion, distributing part of the load to the front-section rack; and performing short-stroke control on the opening degree of the guide plate of the rolling mill, namely setting a head short-stroke opening degree, a middle short-stroke opening degree and a tail short-stroke opening degree aiming at F2-F7 racks. The technical problem that the wedge-shaped precision of short-process hot rolling two-phase region rolling is low is solved, the stability and continuity of short-process hot rolling two-phase region rolling are improved, smooth production is guaranteed, and the wedge-shaped precision of short-process two-phase region rolling is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of hot-rolled plate and strip manufacturing, and specifically relates to a control method for improving wedge-shaped accuracy through rolling load redistribution in a hot-rolled short process. Background Art

[0002] Due to its process characteristics, the CSP production line (thin slab continuous casting and rolling production line) can obtain a more stable temperature difference with the same plate compared with the conventional hot-rolled silicon steel furnace temperature. However, due to its high furnace temperature, the finishing process has a transformation from austenite to ferrite during the rolling process (temperature is about 1020-960℃). In order to further improve the efficiency of the production line, the thickness of the slab at the entrance of the finishing rolling reaches 75mm, and the wedge accuracy is controlled to be 94.31% according to the previous process. In order to ensure the same plate difference accuracy of the secondary material, the wedge accuracy needs to be increased to more than 96%.

[0003] When there are two-phase zone changes in the finishing mill, wedge control during rolling is a difficult point in the production process. The deviation of the wedge on both sides of the strip will affect the rolling stability. At the same time, hot-rolled secondary materials have high requirements for the wedge shape of the strip. Poor wedge accuracy cannot meet the requirements of secondary rolling in the subsequent process, which will cause quality loss and spot generation. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a control method for improving the wedge accuracy of a hot rolling short process by redistributing the rolling load, so as to solve the technical problem of low rolling wedge accuracy in the two-phase zone of hot rolling in the short process, improve the stability and continuity of rolling in the two-phase zone of hot rolling in the short process, ensure smooth production, and achieve improvement of the wedge accuracy of rolling in the two-phase zone of the short process.

[0005] To achieve the above object, the present invention is implemented by the following technical solutions:

[0006] A control method for improving wedge shape accuracy by redistributing rolling load in a hot rolling short process, comprising:

[0007] The constant reduction rate mode is used to distribute the mill load: the reduction rates of F1 and F2 stands are limited to fixed values, and the secondary control system calculates the reduction rates of F3-F7 stands based on the fixed reduction rates of F1 and F2 stands;

[0008] Rolling load redistribution: After the plate is passed, compare the actual rolling load of the last stand with the set load difference. When the deviation between the actual rolling force and the set rolling force reaches the minimum effective force difference ratio, part of the load is distributed to the front stand.

[0009] Short-stroke control of rolling mill guide plate opening: For F2-F7 stands, set the head short-stroke opening, middle short-stroke opening and tail short-stroke opening.

[0010] As a further optimization scheme of the present invention, the F1 rack reduction rate is 50%, the F2 rack reduction rate is 52%, the F3 rack reduction rate ranges from 45% to 52%, the F4 rack reduction rate ranges from 40% to 47%, the F5 rack reduction rate ranges from 26% to 38%, the F6 rack reduction rate ranges from 19% to 33%, and the F7 rack reduction rate ranges from 9% to 18%.

[0011] As a further optimization solution of the present invention, the minimum effective ratio of the force difference is 5%-10%.

[0012] As a further optimization scheme of the present invention, the maximum allocation ratio of the AGC action is 5% to 20%, and the maximum allocation ratio of the AGC action refers to the maximum allocation ratio relative to the thickness of the strip.

[0013] As a further optimization scheme of the present invention, the maximum AGC action amount allocated to the F4 rack is 0.1-1.0 mm, the maximum AGC action amount allocated to the F5 rack is 0.1-0.6 mm, and the maximum AGC action amount allocated to the F6 rack is 0.1-0.6 mm.

[0014] As a further optimization scheme of the present invention, the short stroke opening of the F2 frame head is 60-90mm, the short stroke opening of the middle is 40-60mm, and the short stroke opening of the tail is 50-70mm; the short stroke opening of the F3 frame head is 70-100mm, the short stroke opening of the middle is 50-70mm, and the short stroke opening of the tail is 60-80mm; the short stroke opening of the F4 frame head is 60-90mm, the short stroke opening of the middle is 40-60mm, and the short stroke opening of the tail is The short stroke opening of the F5 frame head is 60-90mm, the short stroke opening of the middle is 40-60mm, and the short stroke opening of the tail is 50-70mm. The short stroke opening of the F6 frame head is 55-85mm, the short stroke opening of the middle is 30-55mm, and the short stroke opening of the tail is 45-65mm. The short stroke opening of the F7 frame head is 55-85mm, the short stroke opening of the middle is 30-55mm, and the short stroke opening of the tail is 45-65mm.

[0015] As a further optimization scheme of the present invention, the method is suitable for manufacturing products with a thickness of 1.2 mm-3.0 mm.

[0016] As a further optimization solution of the present invention, the product includes electrical steel.

[0017] As a further optimization solution of the present invention, the wedge-shaped accuracy of the strip steel is improved to more than 97% during the production process.

[0018] Compared with the prior art, the present invention solves the problem of difficult control of wedge shape accuracy in hot rolling short process, solves the technical problem of easy deviation in two-phase rolling of electrical steel, and realizes the purpose of large-scale production of high wedge shape accuracy and high stability of hot rolling short process strip steel, and has the following effects:

[0019] ① The method does not require equipment modification during implementation, and existing equipment and controls can be used.

[0020] ②This method is suitable for short-process hot rolling finishing mills that have requirements for wedge shape. This method solves the problem of low rolling wedge shape accuracy in the hot rolling two-phase zone.

[0021] ③This method is simple, easy to operate and highly practical.

[0022] ④ Except for the low wedge accuracy caused by the wedge difference of the slab, the problem of low wedge accuracy in the two-phase zone rolling is basically eliminated, which reduces the amount of scrap and improves the thickness difference accuracy of the secondary material. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the temperature-stress-strain curve.

[0024] Figure 2 Schematic diagram of the strip wedge. Figure 2 In the figure, X: strip position from edge, including 25, 40, 50, 75, 100, ... mm; Y: strip position from edge, including 5, 10, 15, ... mm; OS: strip operating side; DS: strip transmission side; H: strip thickness; Hx1: strip thickness at x1; Hx2: strip thickness at x2; Hy1: strip thickness at y1; Hy2: strip thickness at y2. DETAILED DESCRIPTION

[0025] The following describes specific embodiments, and the advantages and various effects of the present invention will be more clearly presented. It should be understood by those skilled in the art that these specific embodiments and examples are used to illustrate the present invention, rather than to limit the present invention.

[0026] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which the present invention belongs, and if there is a conflict, this specification takes precedence.

[0027] like Figure 1 The Z-shaped temperature-stress-strain curve of phase transformation is shown as Figure 2 Shown is a schematic diagram of the strip wedge.

[0028] The technical problem to be solved by the present invention is that CSP rolling of electrical steel is different from conventional hot rolling, and there is two-phase rolling, and there is a transformation from austenite to ferrite during the rolling process (temperature is about 1020-960°C). During the two-phase rolling process, the rolling force will change significantly due to phase change. Under the change of 60Mpa, the strip will have a serious deviation in the finishing mill, resulting in a significant change in the wedge shape in the rolling mill, resulting in loss of wedge shape accuracy or wedge shape mutation.

[0029] In this regard, the present invention designs rolling control process parameters from three aspects: optimizing the rolling mill load distribution strategy under the constant reduction rate mode, rolling load redistribution parameters, and rolling mill guide plate opening short stroke. The specific technical scheme is as follows:

[0030] (1) Load distribution under constant pressure reduction mode

[0031] The constant reduction rate mode is an important function for further development of the second level of the rolling mill to improve quality control. Specifically, it refers to limiting the reduction rate of the F1\F2 frames to a fixed value. The secondary control system calculates the reduction rates of other frames after fixing the F1\F2 reduction rate. Controlling the reduction rate of the F3-F7 frames in the constant reduction rate mode is beneficial to improving the wedge control ability of silicon steel, especially reducing the load of the two-phase rolling frame is beneficial to wedge control. Among them, the mathematical models and algorithms involved in the calculation process of the secondary control system belong to the prior art, and the present invention will not go into details. The specific control parameters are shown in Table 1:

[0032] Table 1 The pressure reduction rate of each rack in the constant pressure reduction mode

[0033]

[0034] (2) Rolling load redistribution:

[0035] Rolling load redistribution (LDC) is to improve the stability of the rolling process, dynamically adjust the rolling load of the last stand during the rolling process to improve the plate shape control ability of the last stand. Its role is to distribute the load of the first step to the front stand by comparing the actual rolling load of the last stand and the set load difference after the plate is passed, so that the actual rolling load of the last stand is controlled, thereby avoiding strip deviation and improving wedge shape accuracy.

[0036] Table 2 Rolling load redistribution parameters

[0037]

[0038]

[0039] The maximum allocation ratio of the automatic gauge control (AGC) action in Table 2 refers to the maximum allocation ratio relative to the strip thickness. For example, if the strip thickness is 2.0 mm, the maximum allocation ratio is 10%, that is, the maximum AGC action amount does not exceed 0.2 mm. The minimum effective force difference ratio refers to the deviation between the actual rolling force and the set rolling force reaching the value of the set parameter, and LDC begins to take effect. The maximum allocation of AGC action to the rack refers to the maximum AGC action amount allocated to each rack.

[0040] (3) Short stroke control of rolling mill guide plate opening:

[0041] The short-stroke control of the rolling mill guide plate opening is to improve the stability during the rolling process, so that the guide plate can improve the centering of the strip entering the rolling mill without damaging the quality of the strip edge, so that the strip will not have uncontrolled deviation due to large changes in rolling force during the two-phase zone rolling process.

[0042] Table 3 Guide plate opening short stroke parameter table

[0043]

[0044] The function and mechanism of the main process in the present invention are:

[0045] The present invention controls the load distribution in the constant reduction mode. When the constant reduction is implemented for two-phase rolling, since there is a strength difference of 60Mpa in the two-phase rolling strip, in order to control the deviation stability of the strip in the strength difference range, the load of the phase change zone frame is reduced to improve the overall rolling stability, and the wedge control accuracy is improved by reducing the deviation of the strip.

[0046] The present invention controls the rolling load redistribution parameters. After the strip is threaded, because the actual thickness of the strip fails to hit the target thickness, the final stand will perform a thickness feedback closed loop, resulting in a deviation between the actual rolling force and the set rolling force. After the deviation occurs, the plate shape control ability of the final stand will be weakened due to excessive or insufficient rolling force, resulting in strip deviation and affecting the wedge shape accuracy. The rolling load redistribution solves the rolling force mismatch problem in the rolling process, improves the plate shape control ability of the final stand and improves the wedge shape accuracy.

[0047] The reason why the present invention controls the guide plate opening to a short stroke is to improve the guiding effect of the guide plates on the strip before and after the strip is threaded, reduce the deviation during the rolling process, and ensure the centering of the strip when entering the roll gap, so as to improve the wedge shape accuracy of the strip. However, the head and tail width and guide plate nodules must be considered comprehensively, and the guide plate opening cannot be simply reduced.

[0048] The present invention is further described in detail below through specific embodiments:

[0049] The weight percentage of the main components of the test steel grades in the following embodiments is: C: 0.02-0.005%, Si≥1.56%, Mn: 0.75-0.82%, P≤0.004%, S≤0.005%, Als: 0.02-0.03%, and the balance is iron and unavoidable impurities. The thickness of the slab at the finishing entrance is 75 mm.

[0050] Embodiment 1:

[0051] ① Load distribution under constant pressure reduction mode, as shown in Table 4.

[0052] Table 4

[0053]

[0054] ② Rolling load redistribution, as shown in Table 5.

[0055] Table 5

[0056] parameter AGC action maximum allocation ratio (%) 10％ Minimum effective force difference ratio (%) 5％ Maximum AGC motion amount allocated to F4 (mm) 0.6 Maximum AGC motion amount allocated to F5 (mm) 0.4 Maximum AGC motion amount allocated to F6 (mm) 0.4

[0057] ③ The short stroke parameters of the guide plate tail are shown in Table 6.

[0058] Table 6

[0059]

[0060] Effect: The wedge accuracy of the strip during production is 98.65%.

[0061] Embodiment 2:

[0062] ① Load distribution under constant pressure reduction mode, as shown in Table 7.

[0063] Table 7

[0064]

[0065] ② Rolling load redistribution, as shown in Table 8.

[0066] Table 8

[0067] parameter AGC action maximum allocation ratio (%) 10％ Minimum effective force difference ratio (%) 5％ Maximum AGC motion amount allocated to F4 (mm) 0.8 Maximum AGC motion amount allocated to F5 (mm) 0.5 Maximum AGC motion amount allocated to F6 (mm) 0.5

[0068] ③ The short stroke parameters of the guide plate tail are shown in Table 9.

[0069] Table 9

[0070]

[0071] Effect: The wedge shape accuracy of the strip steel during production is 98.29%.

[0072] ① Load distribution in constant pressure reduction mode, as shown in Table 10.

[0073] Table 10

[0074]

[0075] ② Rolling load redistribution, as shown in Table 11.

[0076] Table 11

[0077]

[0078]

[0079] ③ The short stroke parameters of the guide plate tail are shown in Table 12.

[0080] Table 12

[0081]

[0082] Effect: The wedge shape accuracy of the strip steel during production is 97.97%.

[0083] ① Load distribution in constant pressure reduction mode, as shown in Table 13.

[0084] Table 13

[0085]

[0086] ② Rolling load redistribution, as shown in Table 14.

[0087] Table 14

[0088] parameter AGC action maximum allocation ratio (%) 10％ Minimum effective force difference ratio (%) 5％ Maximum AGC motion amount allocated to F4 (mm) 0.6 Maximum AGC motion amount allocated to F5 (mm) 0.4 Maximum AGC motion amount allocated to F6 (mm) 0.4

[0089] ③ The short stroke parameters of the guide plate tail are shown in Table 15.

[0090] Table 15

[0091]

[0092]

[0093] Effect: The wedge shape accuracy of the strip during production is 100%.

[0094] The above is a detailed description of the embodiments of the present invention. The contents described are only certain embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of application of the present invention should still fall within the scope of the patent coverage of the present invention. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A control method for improving wedge shape accuracy by redistributing rolling load in a hot rolling short process, characterized in that: include: The constant reduction rate mode is used to distribute the mill load: the reduction rates of F1 and F2 stands are limited to fixed values, and the secondary control system calculates the reduction rates of F3-F7 stands based on the fixed reduction rates of F1 and F2 stands; Rolling load redistribution: After the plate is passed, compare the actual rolling load of the last stand with the set load difference. When the deviation between the actual rolling force and the set rolling force reaches the minimum effective force difference ratio, part of the load is distributed to the front stand. Short-stroke control of rolling mill guide plate opening: For F2-F7 stands, set the head short-stroke opening, middle short-stroke opening and tail short-stroke opening.

2. The control method for improving wedge shape accuracy by redistributing rolling load in a hot rolling short process according to claim 1, characterized in that: The F1 rack reduction rate is 50%, the F2 rack reduction rate is 52%, the F3 rack reduction rate ranges from 45% to 52%, the F4 rack reduction rate ranges from 40% to 47%, the F5 rack reduction rate ranges from 26% to 38%, the F6 rack reduction rate ranges from 19% to 33%, and the F7 rack reduction rate ranges from 9% to 18%.

3. The control method for improving wedge shape accuracy by redistributing rolling load in a hot rolling short process according to claim 1, characterized in that: The minimum effective force difference ratio is 5%-10%.

4. The control method for improving wedge shape accuracy by redistributing rolling load in a hot rolling short process according to claim 1, characterized in that: The maximum allocation ratio of AGC action is 5% to 20%. The maximum allocation ratio of AGC action refers to the maximum allocation ratio relative to the thickness of the strip.

5. The control method for improving wedge shape accuracy by redistributing rolling load in a hot rolling short process according to claim 4, characterized in that: The maximum amount of AGC movement allocated to the F4 rack is 0.1-1.0mm, the maximum amount of AGC movement allocated to the F5 rack is 0.1-0.6mm, and the maximum amount of AGC movement allocated to the F6 rack is 0.1-0.6mm.

6. The control method for improving wedge shape accuracy by redistributing rolling load in a hot rolling short process according to claim 1, characterized in that: The short stroke opening of the F2 frame head is 60-90mm, the short stroke opening of the middle is 40-60mm, and the short stroke opening of the tail is 50-70mm. The short stroke opening of the F3 frame head is 70-100mm, the short stroke opening of the middle is 50-70mm, and the short stroke opening of the tail is 60-80mm. The short stroke opening of the F4 frame head is 60-90mm, the short stroke opening of the middle is 40-60mm, and the short stroke opening of the tail is 50-70mm. The short stroke opening of the F5 frame head is 60-90mm, the short stroke opening of the middle is 40-60mm, and the short stroke opening of the tail is 50-70mm. The short stroke opening of the F6 frame head is 55-85mm, the short stroke opening of the middle is 30-55mm, and the short stroke opening of the tail is 45-65mm. The short stroke opening of the F7 frame head is 55-85mm, the short stroke opening of the middle is 30-55mm, and the short stroke opening of the tail is 45-65mm.

7. The control method for improving wedge shape accuracy by redistributing rolling load in a hot rolling short process according to claim 1, characterized in that: This method is suitable for manufacturing products with a thickness of 1.2mm-3.0mm.

8. The control method for improving wedge shape accuracy by redistributing rolling load in a hot rolling short process according to claim 7, characterized in that: Products include electrical steel.

9. The control method for improving wedge shape accuracy by redistributing rolling load in a hot rolling short process according to claim 1, characterized in that: During the production process, the wedge accuracy of the strip is improved to over 97%.

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