A method for improving the quality of cold-rolled edges of high-grade non-oriented silicon steel rough coils

Abstract

The present invention belongs to the technical field of non-oriented silicon steel production and discloses a method for improving the cold-rolled edge quality of high-grade non-oriented silicon steel burr coils. The method comprises: cold rolling using a multi-stand continuous rolling mill or a single-stand reversible rolling mill for 5 to 7 rolling passes, controlling the flatness of the plate after the first, second, and final rolling passes to meet a specific formula; in addition, the rolling speed of the first pass, the emulsion flow rate of the first and second passes, and the original roughness of the mill work rolls can be further controlled. The present invention achieves the purpose of controlling rolled edge cracks and reducing edge waves by adopting a large edge wave rolling mode and adjusting the rolling speed, emulsion flow rate, and the original roughness of the work rolls, thereby achieving optimal cold-rolled edge quality of the burr coils and improving production efficiency and product yield.

Description

Technical Field

[0001] The invention belongs to the technical field of non-oriented silicon steel production, and in particular relates to a method for improving the quality of cold-rolled edges of high-grade non-oriented silicon steel burr coils. Background Art

[0002] Cold rolling is a key process in the production of high-grade non-oriented silicon steel. The success of cold rolling significantly impacts the quality and production cost of high-grade non-oriented silicon steel. Due to its high silicon content, high-grade non-oriented silicon steel is brittle and prone to edge cracking during cold rolling, reducing yield and wasting resources. In severe cases, this can lead to strip breakage, resulting in inestimable economic losses.

[0003] The edge cracking phenomenon is more likely to occur in the rolling of rough edge coils. The rough edge coil rolling refers to a process technology in which the hot-rolled raw materials are directly cold-rolled without trimming. Due to the inherent disadvantage of the edge quality of the rough edge coil, the edge is very likely to crack during the rolling process, which brings a higher risk of strip breakage to the rolling process. However, since the rough edge coil eliminates the trimming operation in the normal pickling unit, the rough edge coil has a great advantage in cutting loss for the same hot-rolled material. From the actual production data, it can be clearly seen that compared with the trimmed coil, the rough edge coil has reduced cutting loss and improved the yield rate. At the same time, due to the reduction of trimming operations, the loss of the disc shear blade of the previous process unit is greatly reduced, which greatly reduces the production cost. Therefore, the research on rough edge coil rolling is of great practicality.

[0004] Regarding improving the quality of cold-rolled edges of high-grade non-oriented silicon steel rough edges, the relevant research results are as follows:

[0005] Patent CN105396879A discloses a method for controlling edge cracking in cold tandem rolling of high-grade non-oriented silicon steel. To effectively reduce strip edge stress and prevent edge cracking during cold tandem rolling of high-grade non-oriented silicon steel, the method reduces the load distribution of the first stand from 33-36% (automatically distributed by the system) to 25-30%. The UCMW mill work roll shifting value is set to -40-20mm. While this patent improves edge cracking of the exiting steel plate by reducing the load distribution of the first stand, it inevitably increases the rolling load distribution of the subsequent stands. Furthermore, as deformation resistance increases, the rolling load of the subsequent stands increases dramatically, which is extremely detrimental to edge cracking and plate shape control.

[0006] Patent CN111687210A discloses a method for producing 0.35mm non-oriented silicon steel using a cold rolling mill. The method uses a one-shot rolling method to continuously cold-roll the cold-rolled raw material coil on five stands. By controlling the reduction rate, rolling force, and tension between stands and on the inlet and outlet sides of each pass, and using emulsion spraying for process lubrication and cooling, and performing zoned cooling on the working rolls, the thermal crown of the working rolls is controlled to adjust the steel strip shape. An intermediate product of non-oriented silicon steel with a thickness of 0.35mm can be obtained. The main purpose is to obtain a 0.35mm product with a good plate shape, but there is no improvement in the edge cracking problem.

[0007] The above patent documents all aim to optimize the edge quality of cold-rolled silicon steel, but all have certain problems or limitations. Currently, there is no perfect means to simultaneously control edge cracking and edge waves to obtain good edge quality for cold-rolling of rough-edged coils of high-grade non-oriented silicon steel. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to address the shortcomings of the existing technology and provide a method for improving the quality of the cold-rolled edge of high-grade non-oriented silicon steel rough edge coils. By adopting a large edge wave rolling mode and adjusting the rolling speed, emulsion flow rate, original roughness of the working rolls, etc., the purpose of controlling the rolling edge cracks and reducing the edge waves is achieved, thereby obtaining the best quality of the cold-rolled edge of the rough edge coils and improving production efficiency and product yield.

[0009] In order to solve the technical problem raised by the present invention, the present invention provides a method for improving the quality of the cold-rolled edge of a high-grade non-oriented silicon steel burr coil, comprising: cold rolling using a multi-stand continuous rolling mill or a single-stand reversing rolling mill for 5 to 7 passes, and controlling the flatness of the plate after the first, second and last passes to meet the following formula:

[0010] 0.8×H 40 ≤F1≤0.8×H 40 +20

[0011] 0.6×H 40 ≤F2≤0.6×H 40 +20

[0012] 0.3×H 40 ≤F m ≤0.3×H 40 +20

[0013] Where, F1, F2, F m They are the flatness after the first, second and final rolling passes, in I; H 40 It is the thickness difference between the point 40mm away from the edge and the outermost point of the hot-rolled rough edge coil raw material, and the average value of the whole coil is taken in μm.

[0014] Furthermore, the H40 ≤120μm.

[0015] In the above solution, the rolling speed of the first pass of the cold rolling process satisfies the following formula:

[0016] 1200-2.4×10 4 ×(Si+Al)≤V≤1200-1.8×10 4 ×(Si+Al)

[0017] Where V is the rolling speed, unit is m / min; (Si+Al) is the sum of the mass percentages of Si and Al in the steel.

[0018] In the above scheme, the emulsion flow rate of the first and second cold rolling passes is controlled to meet the following formula:

[0019] 10000-1.4×10 5 ×(Si+Al)≤L≤10000-10 5 ×(Si+Al)

[0020] Where L is the emulsion flow rate of the first and second passes, unit is L / min; (Si+Al) is the sum of the mass percentages of Si and Al in steel.

[0021] In the above solution, the original roughness of the working roll of the cold rolling control mill satisfies the following formula:

[0022] 50×(Si+Al)≤R≤100×(Si+Al)

[0023] Where R is the original roughness of the working roll, in μm; (Si+Al) is the sum of the mass percentages of Si and Al in the steel.

[0024] In the above solution, the sum of the mass percentages of Si and Al in the high-grade non-oriented silicon steel is 2-4.5%, that is, (Si+Al) in the above formula is 2-4.5%.

[0025] Furthermore, the chemical composition of the high-grade non-oriented silicon steel includes, by mass percentage, C≤0.004%, S≤0.003%, N≤0.003%, Ti≤0.003%, P≤0.05%, Nb≤0.003%, Si≤4.0%, Al≤2.0%, (Si+Al)2~4.5%, Mn≤2.0%, and the balance is Fe and unavoidable impurities.

[0026] In the above solution, the thickness of the high-grade non-oriented silicon steel burr roll is 1.6 to 2.4 mm.

[0027] In the above solution, the thickness of the finished product of the high-grade non-oriented silicon steel burr coil after cold rolling is 0.20-0.50 mm.

[0028] In the above solution, the edge crack depth of the finished product of the high-grade non-oriented silicon steel rough edge coil after cold rolling is ≤2mm, and the edge wave height is ≤4mm.

[0029] The technical concept of the present invention is as follows:

[0030] 1) For high-grade non-oriented silicon steel, especially silicon steel with high alloy content, its plasticity is slightly poor. At this time, adopting the edge wave control mode (flatness control is released) for rolling can effectively reduce the occurrence of strip edge cracks during the rolling process. By rationally controlling the edge wave shape and speed during the rolling process, the strip breakage caused by strip deviation can be greatly reduced, and the occurrence of strip edge cracks can be reduced at the same time. Since the first pass has the largest reduction rate, its edge crack risk is the highest, and the corresponding plate flatness is greater. Since the hot-rolled coil edge is not trimmed, there is an obvious edge drop phenomenon, and the greater the edge drop, the more serious the uneven deformation of the edge, so the flatness control is looser, but if the upper limit of the plate flatness control is too high, the subsequent finished product edge wave will be too high, the cutting loss will increase, and the yield rate will decrease. Therefore, the flatness control of the last pass is tightened to try to eliminate or reduce the edge wave generated by the previous pass. In summary, the first pass flatness control: 0.8×H 40 ≤F1≤0.8×H 40 +20, second pass flatness control: 0.6×H 40 ≤F2≤0.6×H 40 +20, final straightness control: 0.3×H 40 ≤F m ≤0.3×H 40 +20.

[0031] 2) Due to the large reduction rate in the first pass, the rollers heat up rapidly, increasing the risk of deformation and loss of rolls. On the other hand, fluctuations in the thickness of the raw material will cause uneven deformation. At the same time, the rolling speed directly affects the stability and deformation temperature of the rolling process. The appropriate rolling speed range can effectively control the deformation behavior of the material during the rolling process, avoiding excessive strain rate and rolling force fluctuations. In the present invention, if the first rolling speed is too high and the strain rate is too large, the plate shape will not be adjusted in time and the strip will break. If the first rolling speed is too low, it will lead to too low deformation temperature and excessive cold deformation stress, which will affect the dimensional accuracy and surface quality of the product and reduce production efficiency. In addition, the higher the (Si+Al), the lower the first rolling speed range V is, to prevent the risk of edge cracking caused by high strain rate. Therefore, the present invention controls the first rolling speed V to: 1200-2.4×10 4 ×(Si+Al)≤V≤1200-1.8×10 4×(Si+Al).

[0032] 3) High-grade non-oriented silicon steel has high alloy content, high brittleness and poor toughness. Increasing the plate temperature can effectively reduce deformation resistance and improve rollability. By increasing the strip temperature at a low flow rate, the strip temperature can be further increased, so that the resistance of the strip along the rolling direction is reduced and the cracks are reduced. On the other hand, due to the large rolling deformation during the first and second cold rolling processes, the rollers will experience thermal expansion. By maintaining an appropriate emulsion flow rate, the thermal expansion of the rollers can be eliminated, thereby effectively controlling the strip shape. During the rolling process, the emulsion can lubricate the friction interface between the roller and the strip and the roller support interface, thereby increasing the reduction, reducing the rolling pressure, and reducing the risk of edge cracking. Considering that the higher the (Si+Al), the higher the plate temperature requirement, the lower the emulsion flow rate, so the first and second emulsion flow rate L is controlled to be: 10000-1.4×10 5 ×(Si+Al)≤L≤10000-10 5 ×(Si+Al).

[0033] 4) The friction coefficient has a certain influence on the occurrence of edge cracks. The greater the friction coefficient, the milder the edge cracks of cold-rolled silicon steel. Therefore, increasing the friction coefficient can improve the edge crack situation. The original roughness of the working roll will affect the rolling force and the thickness of the lubricating oil film, especially the first and second passes where the reduction is the largest. For high-grade non-oriented silicon steel, the higher the (Si+Al), the higher the required rolling force. Increasing the original roughness of the working roll can reduce the thickness of the lubricating oil film, increase the friction coefficient, and thus increase the rolling force, thereby reducing the incidence of edge cracks. However, the original roughness of the working roll will affect the working life of the roll. Excessive original roughness of the working roll will accelerate the wear of the working roll, produce meat defects, and affect the plate surface quality and roll life. Therefore, the original roughness R of the working roll is controlled to be: 50×(Si+Al)≤R≤100×(Si+Al).

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention adopts a large edge wave rolling mode and adjusts the rolling speed, emulsion flow rate, original roughness of the working roll, etc., thereby reducing the occurrence of cold-rolled edge cracks and edge waves of high-grade non-oriented silicon steel under the condition that the hot-rolled raw materials are not trimmed. After rolling, no long continuous cracks occur, the edge crack depth is ≤2mm, and the edge wave height is ≤4mm, thereby achieving continuous and efficient production, reducing the edge cutting loss after cold rolling, and improving the yield rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a comparison chart of the edge quality of the cold-rolled products 1-3 (left) in Example 1 and 1-5 (right) in Comparative Example 1. DETAILED DESCRIPTION

[0037] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0038] In the following examples, the chemical composition and weight percentage of high-grade non-oriented silicon steel are shown in Table 1, with the remainder being Fe and unavoidable impurities.

[0039] Table 1 Chemical composition of steel and its weight percentage

[0040] serial number C(％) S(％) N(％) Ti(%) P(％) Nb(%) Si (%) Al(％) Mn (%) Example 1 0.0025 0.0022 0.0024 0.0017 0.02 0.0021 2.2 0.8 0.52 Example 2 0.0031 0.0017 0.0018 0.0023 0.03 0.0013 3.5 0.5 0.24 Example 3 0.0018 0.0009 0.0012 0.0015 0.04 0.0018 2.7 1.1 0.65

[0041] In the following embodiments, a method for improving the quality of the cold-rolled edge of a high-grade non-oriented silicon steel rough edge coil comprises:

[0042] 1) Cold rolling adopts multi-stand continuous rolling mill or single-stand reversible rolling mill for 5 to 7 passes, and the flatness of the plate after the first, second and last passes is controlled to meet the following formula:

[0043] 0.8×H 40 ≤F1≤0.8×H 40 +20

[0044] 0.6×H 40 ≤F2≤0.6×H 40 +20

[0045] 0.3×H 40 ≤F m ≤0.3×H 40 +20

[0046] Where, F1, F2, F m They are the flatness after the first, second and final rolling passes, in I; H 40 The thickness difference between the point 40mm away from the edge and the outermost point of the hot-rolled rough edge coil is the average value of the whole coil, in μm.

[0047] 2) The rolling speed of the first cold rolling pass satisfies the following formula:

[0048] 1200-2.4×10 4 ×(Si+Al)≤V≤1200-1.8×10 4 ×(Si+Al)

[0049] Where V is the rolling speed, unit is m / min; (Si+Al) is the sum of the mass percentages of Si and Al in the steel;

[0050] 3) The emulsion flow rate of the first and second cold rolling passes satisfies the following formula:

[0051] 10000-1.4×10 5×(Si+Al)≤L≤10000-10 5 ×(Si+Al)

[0052] Where, L is the emulsion flow rate of the first and second passes, unit is L / min; (Si+Al) is the sum of the mass percentages of Si and Al in the steel;

[0053] 4) The original roughness of the cold rolling mill work roll satisfies the following formula:

[0054] 50×(Si+Al)≤R≤100×(Si+Al)

[0055] Where R is the original roughness of the working roll, in μm; (Si+Al) is the sum of the mass percentages of Si and Al in the steel.

[0056] Example 1 and Comparative Example 1

[0057] The high grade non-oriented silicon steel burrs used have (Si+Al)=3%, H 40 =50μm, thickness is 2.3mm, cold rolling adopts multi-stand continuous rolling mill for 5 passes, and the finished product thickness is 0.50mm. After calculation:

[0058] 1) The flatness of the plate after the first, second and final rolling passes must meet the requirements of 40≤F1≤60, 30≤F2≤50, 15≤F m ≤35, unit I;

[0059] 2) The rolling speed of the first pass must meet 480≤V≤660, unit: m / min;

[0060] 3) The emulsion flow rate of the first and second passes must meet 5800≤L≤7000, unit L / min;

[0061] 4) The original roughness of the working roll must meet 1.5≤R≤3, unit: μm.

[0062] The actual process parameter control conditions and the edge quality of the finished products after rolling in the examples and comparative examples are shown in Table 2.

[0063] Table 2

[0064]

[0065] As shown in Table 2, the edge quality of the finished product obtained in the embodiment is good. In Comparative Example 1-1, the rolling speed of the first pass is too high, and the flatness control of the first and second passes is too strict, resulting in strip breakage in the second pass of cold rolling. In Comparative Example 1-2, the emulsion flow rate of the first and second passes is too large, the original roughness of the working roll is too small, and the edge cracks of the rolled product are too large. In Comparative Example 1-3, the flatness control of the first, second and last passes is too loose, and the edge waves of the finished product are too large. In Comparative Example 1-4, the emulsion flow rate is too large, the original roughness of the working roll is too small, and the edge cracks of the finished product are too large. In Comparative Example 1-5, the emulsion flow rate is too small, the thermal expansion of the roll is not sufficiently eliminated, the lubrication of the roll and the steel plate surface is insufficient, and the flatness control of the first pass is too strict, resulting in excessive edge cracks in the finished product. Figure 1 The following figure compares the edge quality of the cold-rolled products 1-3 (left) in Example 1 and 1-5 (right) in Comparative Example 1. The difference in performance is intuitively apparent. In Comparative Example 1-6, the second pass flatness control was too strict, resulting in excessive roughness on the work rolls, which led to large edge cracks in the finished product and pitting defects on the plate surface. In Comparative Example 1-7, the first pass rolling speed was too low, resulting in low deformation temperature, high cold deformation stress, and large edge waves in the finished product.

[0066] Example 2 and Comparative Example 2

[0067] The high grade non-oriented silicon steel burrs used have (Si+Al)=4%, H 40 =80μm, thickness is 2.1mm, cold rolling adopts 20-roll single-stand reversible rolling mill for 5 passes, and the finished product thickness is 0.25mm. After calculation:

[0068] 1) The flatness of the plate after the first, second and final rolling passes must meet the requirements of 64≤F1≤84, 48≤F2≤68, 24≤F m ≤44, unit I;

[0069] 2) The rolling speed of the first pass must meet 240≤V≤480, unit: m / min;

[0070] 3) The emulsion flow rate of the first and second passes must meet 4400≤L≤6000, unit L / min;

[0071] 4) The original roughness of the working roll must meet 2≤R≤4, unit: μm.

[0072] The actual process parameter control conditions and the edge quality of the finished products after rolling in the examples and comparative examples are shown in Table 3.

[0073] Table 3

[0074]

[0075]

[0076] As shown in Table 3, the edge quality of the finished product obtained in the embodiment is good. In Comparative Example 2-1, the rolling speed of the first pass is too high, and the flatness control of the first pass is too strict, resulting in strip breakage in the first pass of cold rolling. In Comparative Example 2-2, the flatness control of the first pass is too strict, the emulsion flow rate of the first and second passes is too large, and the edge cracks of the rolled product are too large. In Comparative Example 2-3, the flatness control of the first, second and last passes is too loose, and the edge waves of the finished product are too large. In Comparative Example 2-4, the emulsion flow rate is too large, the original roughness of the working roll is too small, and the edge cracks of the finished product are too large. In Comparative Example 2-5, the emulsion flow rate is too small, and the flatness control of the first pass is too strict, resulting in excessive edge cracks in the finished product. In Comparative Example 2-6, the flatness control of the second pass is too strict, and the original roughness of the working roll is too large, resulting in large edge cracks in the finished product and pitting defects on the plate surface. In Comparative Example 2-7, the first rolling speed is too low, resulting in too low deformation temperature, large cold deformation stress, and large edge waves of the finished product.

[0077] Example 3 and Comparative Example 3

[0078] The high grade non-oriented silicon steel burrs used have (Si+Al)=3.8%, H 40 =60μm, thickness is 1.6mm, cold rolling adopts 20-roll single-stand reversible rolling mill for 6 passes, and the finished product thickness is 0.20mm. After calculation:

[0079] 1) The flatness of the plate after the first, second and final rolling passes must meet the requirements of 48≤F1≤68, 36≤F2≤56, 18≤F m ≤38, unit I;

[0080] 2) The rolling speed of the first pass must meet 288≤V≤516, unit: m / min;

[0081] 3) The emulsion flow rate of the first and second passes must meet 4680≤L≤6200, unit L / min;

[0082] 4) The original roughness of the working roll must meet 1.9≤R≤3.8, unit: μm.

[0083] The actual process parameter control conditions and the edge quality of the finished products after rolling in the examples and comparative examples are shown in Table 4.

[0084] Table 4

[0085]

[0086] As shown in Table 4, the edge quality of the finished product obtained in the embodiment is good. In Comparative Example 3-1, the rolling speed of the first pass is too high, and the flatness control of the first pass is too strict, resulting in strip breakage in the first pass of cold rolling. In Comparative Example 3-2, the flatness control of the first pass is too strict, the emulsion flow rate of the first and second passes is too large, and the edge cracks of the rolled product are too large. In Comparative Example 3-3, the flatness control of the first, second and last passes is too loose, and the edge waves of the finished product are too large. In Comparative Example 3-4, the emulsion flow rate is too large, the original roughness of the working roll is too small, and the edge cracks of the finished product are too large. In Comparative Example 3-5, the emulsion flow rate is too small, and the flatness control of the first pass is too strict, resulting in excessive edge cracks in the finished product. In Comparative Example 3-6, the flatness control of the second pass is too strict, and the original roughness of the working roll is too large, resulting in large edge cracks in the finished product and pitting defects on the plate surface. In Comparative Examples 3-7, the first-pass rolling speed is too low, resulting in too low deformation temperature, large cold deformation stress, and large edge waves in the finished product.

[0087] The above embodiments are merely examples for clarification and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications may be made based on the above descriptions. It is not necessary and impossible to enumerate all implementation methods here, and any obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for improving the quality of cold-rolled edges of high-grade non-oriented silicon steel burrs, characterized in that: Cold rolling adopts multi-stand continuous rolling mill or single-stand reversing rolling mill for 5 to 7 passes. The flatness of the plate after the first, second and last passes is controlled to meet the following formula: 0.8×H 40 ≤F1≤0.8×H 40 +20 0.6×H 40 ≤F2≤0.6×H 40 +20 0.3×H 40 ≤F m ≤0.3×H 40 +20 Where, F1, F2, F m They are the flatness after the first, second and final rolling passes, in I. H 40 The thickness difference between the point 40mm away from the edge and the outermost point of the hot-rolled rough edge coil is the average value of the whole coil, in μm. The original roughness of the mill work roll, the rolling speed of the first pass, and the emulsion flow rates of the first and second passes are controlled to meet the following formula: 50×(Si+Al)≤R≤100×(Si+Al) 1200-2.4×10 4 ×(Si+Al)≤V≤1200-1.8×10 4 ×(If+Al) 10000-1.4×10 5 ×(Si+Al)≤L≤10000-10 5 ×(If+Al) Where R is the original roughness of the work roll, in μm; V is the rolling speed, in m / min; L is the emulsion flow rate of the first and second passes, in L / min; (Si+Al) is the sum of the mass percentages of Si and Al in the steel.

2. The method for improving the quality of cold-rolled edges of high-grade non-oriented silicon steel burr coils according to claim 1, characterized in that: The H 40 ≤120μm.

3. The method for improving the quality of cold-rolled edges of high-grade non-oriented silicon steel burr coils according to claim 1, characterized in that: The sum of the mass percentages of Si and Al (Si+Al) in the high-grade non-oriented silicon steel is 2-4.5%.

4. The method for improving the quality of cold-rolled edges of high-grade non-oriented silicon steel burr coils according to claim 1, characterized in that: The chemical composition of the high-grade non-oriented silicon steel includes, by mass percentage, C≤0.004%, S≤0.003%, N≤0.003%, Ti≤0.003%, P≤0.05%, Nb≤0.003%, Si≤4.0%, Al≤2.0%, (Si+Al) 2~4.5%, Mn≤2.0%, and the balance is Fe and unavoidable impurities.

5. The method for improving the quality of cold-rolled edge of high-grade non-oriented silicon steel burr coil according to claim 1, characterized in that: The thickness of the high-grade non-oriented silicon steel burr roll is 1.6-2.4 mm.

6. The method for improving the quality of cold-rolled edges of high-grade non-oriented silicon steel burr coils according to claim 1, characterized in that: The thickness of the finished product of the high-grade non-oriented silicon steel burr coil after cold rolling is 0.20-0.50 mm.

7. The method for improving the quality of cold-rolled edge of high-grade non-oriented silicon steel burr coil according to claim 1, characterized in that: The edge crack depth of the finished product of the high-grade non-oriented silicon steel rough edge coil after cold rolling is ≤2mm, and the edge wave height is ≤4mm.

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