Method for improving rolling stability of non-oriented silicon steel

Abstract

The invention relates to the technical field of hot rolling processes, in particular to a method for improving rolling stability of non-oriented silicon steel, which comprises casting blank heating, rough rolling and finish rolling, the casting blank heating adopts slow heating, long heat preservation and low-temperature tapping modes to keep slab grains uniform, the rough rolling adopts low-speed rolling to guarantee rough rolling stability, and the finish rolling adopts low-speed rolling to guarantee rolling stability. The method has the beneficial effects that the rolling stability of the non-oriented silicon steel is improved, the phenomena of strip steel running, guide ruler impacting, folding, steel clamping and the like occurring in the rolling process of the non-oriented silicon steel are reduced, and the rolling line defect blocking rate is reduced to 2% from 17%; the rolling line yield is increased from 97.5% to 98.9%; and the convexity hit percent of pass is improved from 54% to 83%.

Description

Technical Field

[0001] The invention relates to the technical field of hot rolling steel technology, and in particular to a method for improving the rolling stability of non-oriented silicon steel. Background Art

[0002] Non-oriented silicon steel is mainly used in various small and medium-sized motors, compressors and other equipment. However, since small and micro motors are mainly produced and processed by automatic high-speed punching and stacking riveting, it is required that not only the magnetic properties of the silicon steel finished plate are uniform, but also the difference between the same silicon steel finished plates is small.

[0003] The silicon content in low-grade non-oriented silicon steel is 0.4%-0.8%. During production, it was found that steel with high Si percentage and low Al percentage has a greater impact on deformation resistance after phase transformation. Silicon steel is a high-silicon, low-aluminum product. During the rolling process, it is easy to undergo phase transformation and enter the α+γ two-phase region for rolling. The two-phase region rolling brings about a sudden change in deformation resistance and a change in metal volume, which will lead to unstable finishing rolling. When the finishing rolling is unstable, the strip will swing in the rolling mill, which may cause edge cracks and foreign matter indentation defects of the strip, or even rolling breakage and strip breakage accidents, seriously affecting the production efficiency and yield rate of the production line. In addition, when the finishing rolling is unstable, the cross-sectional shape of the strip cannot be guaranteed, making it difficult for the downstream cold rolling process to control the difference between the finished products and the same plate. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the present invention provides a method for improving the rolling stability of non-oriented silicon steel. The ingot heating adopts slow heating, long heat preservation and low temperature steel tapping to keep the slab grains uniform. The rough rolling adopts low speed rolling to ensure the rough rolling stability. The finishing rolling parameters are optimized to improve the rolling stability, which greatly reduces the occurrence rate of edge crack defects in non-oriented silicon steel, and also reduces the probability of steel jamming accidents in the rolling line, thereby improving the product yield rate.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for improving the rolling stability of non-oriented silicon steel comprises heating of the ingot, rough rolling and finishing rolling, wherein the heating of the ingot adopts a slow heating, long heat preservation and low temperature steel tapping method to keep the slab grains uniform, the rough rolling adopts a low speed rolling to ensure the rough rolling stability, and the finishing rolling parameters are optimized to improve the rolling stability. The method for improving the rolling stability of non-oriented silicon steel specifically comprises the following steps:

[0007] S1. Billet heating:

[0008] The surface temperature of the furnace should be controlled to be not less than 350℃ by slow cooling of the billet stack or insulation in the insulation pit during charging;

[0009] Control the furnace gas temperature in the preheating section at 950 - 1050 °C; control the furnace gas temperature in the heating section at 1140 - 1180 °C; control the furnace gas temperature in the soaking section at 1200 - 1240 °C;

[0010] Control the actual heating rate of the slab. When the temperature is between 600 °C and 1000 °C, heat up slowly with a heating rate of 20 - 30 °C / min;

[0011] Control the heating time of the slab in the furnace. The total heating time is not less than 115 min, the heating time in the preheating section is not less than 30 min, the heating time in the heating section is not less than 40 min, and the heating time in the soaking section is not less than 45 min;

[0012] Control the actual discharging temperature of the slab at 1140 - 1180 °C;

[0013] S2. Rough rolling:

[0014] Reversible rolling is adopted for rough rolling. The number of rolling passes is 1 + 5, the total reduction is 78 - 81%, and the thickness of the intermediate billet is 34 - 45 mm;

[0015] The throwing speed of the last pass in rough rolling is 3.5 m / s - 4.15 m / s;

[0016] Control the finishing temperature in rough rolling at 1030 °C - 1060 °C;

[0017] S3. Finish rolling:

[0018] Control the starting temperature of finish rolling at 1020 °C - 1050 °C;

[0019] Continuous rolling is carried out on a 6 - pass continuous rolling mill for finish rolling. The final rolling temperature of the steel strip is controlled within the range of 880 °C - 920 °C;

[0020] Control the reduction rate of the first pass in finish rolling at 52 - 55%, the reduction rate of the second pass at 31 - 44%, and the throwing speed at 9 - 10.5 m / s;

[0021] Control the difference in roll profiles of the first two stands in front of the work rolls in finish rolling at 50 - 60 μm;

[0022] Control the leading scale allowance in front of the finish rolling stands. The leading scale allowance for the first three stands is 24 - 26 mm, the fourth stand is 29 - 31 mm, and the fifth and sixth stands are released to 49 - 51 mm.

[0023] Furthermore, in the finish rolling of step S3, the low - temperature rolling controls the phase transformation of non - oriented silicon steel to occur in the first two stands with stronger rolling capabilities.

[0024] Furthermore, in the finish rolling of step S3, the leading scale liner between the finish rolling stands adopts a "loose - front - tight - rear method" starting from the short stroke behind the fourth stand.

[0025] Furthermore, the front loose and back tight method is that the opening of the front guide liner of the finishing mill is set to 35mm 50m before the strip head and to 20mm after 50m.

[0026] Furthermore, the blocking rate of the non-oriented silicon steel rolling line is reduced from 17% to 2%, the rolling line yield rate is increased from 97.5% to 98.9%, and the strip convexity hit qualified rate is increased from 54% to 83%.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention improves the rolling stability of non-oriented silicon steel fundamentally through reasonable optimization of the heating process, the rough rolling process, the finishing rolling process and the parameter settings of the main devices, and the above processes are connected and coordinated with each other to reduce the occurrence of defect blocking phenomena such as strip running, hitting the guide ruler and folding in the rolling process of non-oriented silicon steel, thereby improving the hot rolling yield rate of the product; the rolling line defect blocking rate is reduced from 17% to 2%; the rolling line yield rate is increased from 97.5% to 98.9%; the convexity hit qualified rate is increased from 54% to 83%. DETAILED DESCRIPTION

[0029] The specific embodiments of the present invention are further described below:

[0030] The following are examples of the present invention. These examples are only for describing the best mode of carrying out the present invention, but do not limit the scope of the present invention in any way.

[0031] Table 1 shows the heating parameters of the casting blank in the embodiment:

[0032]

[0033] Table 2 shows the rough rolling process parameters of the embodiment:

[0034] Example Rough rolling steel throwing speed m / s Rough rolling end temperature °C Rough rolling reduction rate % Intermediate billet thickness mm 1 3.58 1031 79 43 2 3.79 1039 81 35 3 4.01 1033 80 37 4 3.97 1059 78 34 5 3.99 1057 79 45 6 4.14 1046 78 42 7 4.02 1033 80 39 8 3.97 1048 79 41 9 3.68 1059 80 37 10 3.75 1058 81 38 11 3.99 1037 80 40 12 4.11 1046 82 39 13 3.95 1044 82 34

[0035] Table 3 is the finishing process parameters of the embodiment:

[0036]

[0037] Table 4 is the rolling stability results of the embodiment

[0038] Example Crown hitting qualified rate % 1 83.5 2 84.2 3 83 4 85 5 84 6 87.3 7 83.7 8 84.1 9 85.9 10 84.2 11 85 12 86.7 13 88.3

[0039] It can be concluded from the above-mentioned embodiments 1 to 13 that the rolling stability of non-oriented silicon steel is fundamentally improved by the mutual connection and coordination between the above-mentioned processes, and the occurrence of strip running, hitting the guide, folding, steel jamming and other phenomena in the rolling process of non-oriented silicon steel is reduced. The rolling line defect blocking rate is reduced from 17% to 2%; the rolling line yield rate is increased from 97.5% to 98.9%; the convexity hit qualified rate is increased from 54 to 83%.

[0040] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for improving the rolling stability of non-oriented silicon steel, including continuous casting slab heating, rough rolling and finish rolling, characterized in that, The heating of the casting adopts slow heating, long heat preservation and low temperature steel tapping to keep the slab grains uniform, the rough rolling adopts low speed rolling to ensure the rough rolling stability, and the finishing rolling parameters are optimized to improve the rolling stability. The method for improving the rolling stability of non-oriented silicon steel specifically includes the following steps: S1. Billet heating: The surface temperature of the furnace should be controlled to be not less than 350℃ by slow cooling of the billet stack or insulation in the insulation pit during charging; Control the gas temperature of the preheating section heating furnace at 950-1050°C; control the gas temperature of the heating section furnace at 1140-1180°C; control the gas temperature of the soaking section furnace at 1200-1240°C; Control the actual heating rate of the ingot, slowly heat it up between 600℃ and 1000℃, and the heating rate is 20~30℃ / min; Control the heating time in the casting furnace. The total heating time shall not be less than 115 minutes, the heating time in the preheating section shall not be less than 30 minutes, the heating time in the heating section shall not be less than 40 minutes, and the heating time in the soaking section shall not be less than 45 minutes; The actual furnace temperature of the cast billet is controlled at 1140℃~1180℃; S2. Rough rolling: The rough rolling adopts reversible rolling, the rolling pass is 1+5, the total reduction is 78-81%, and the intermediate billet thickness is 34-45mm; The speed of the last rough rolling pass is 3.5m / s~4.15m / s; The rough rolling end temperature is controlled at 1030℃~1060℃; S3. Finishing rolling: The starting temperature of finishing rolling is controlled at 1020℃~1050℃; The finishing rolling adopts 6-pass continuous rolling mill, and the final rolling temperature of the steel strip is controlled within the range of 880℃~920℃; The first pass reduction rate of finishing rolling is controlled at 52-55%, the second pass reduction rate is controlled at 31-44%, and the steel throwing speed is controlled at 9-10.5 m / s; The difference in the roller profiles of the first two work rolls of the finishing rolling mill is controlled within 50-60 μm; The front guide gauge margin of the finishing mill stands is controlled at 24-26mm for the first three stands, 29-31mm for the fourth stand, and 49-51mm for the fifth and sixth stands.

2. A method for improving the rolling stability of non-oriented silicon steel according to claim 1, characterized in that, The low temperature rolling in the finishing rolling of step S3 controls the phase transformation of the non-oriented silicon steel to occur in the first two stands with stronger rolling capacity.

3. A method for improving the rolling stability of non-oriented silicon steel according to claim 1, characterized in that, In the finishing rolling of step S3, the guide liner between the stands of the finishing rolling mill adopts the "front loose and rear tight method" for the short stroke after the fourth stand.

4. A method for improving the rolling stability of non-oriented silicon steel according to claim 3, characterized in that, The front loose and back tight method is that the opening of the front guide liner of the finishing mill is set to 35mm 50m before the strip head and to 20mm after 50m.

5. A method for improving the rolling stability of non-oriented silicon steel according to claim 1, characterized in that, The blocking rate of the non-oriented silicon steel rolling line is reduced from 17% to 2%, the yield rate of the rolling line is increased from 97.5% to 98.9%, and the qualified rate of the strip convexity is increased from 54% to 83%.

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