Method for improving rolling stability of non-oriented silicon steel

Abstract

This invention provides a method for improving the rolling stability of non-oriented silicon steel. By employing a three-stage high-temperature heating method, the temperature of the slab is made uniform in a shorter time. In the roughing stage, the uniformity of the longitudinal temperature of the strip is ensured by controlling the bite speed, rolling speed and ejection speed of each pass consistently. In the finishing stage, the rolling stability is greatly improved by controlling the finishing entry temperature to ≤960℃, thus solving the problem of scrap caused by rolling instability in the hot-rolled finishing stage of non-oriented silicon steel.

Description

Technical Field

[0001] This invention relates to the field of silicon steel production technology, specifically to a method for rolling non-oriented silicon steel, and more particularly to a method for improving the rolling stability of non-oriented silicon steel. Background Technology

[0002] Currently, non-oriented silicon steel is mainly used in the manufacture of motor cores. Its quality directly determines the quality of the motor and has a significant impact on my country's energy consumption and environmental protection. With the introduction of the "dual carbon" target, higher requirements have been placed on the quality of non-oriented silicon steel. For the production of non-oriented silicon steel, in order to ensure the magnetic properties of the product, low homogenization temperatures and high finishing and coiling temperatures are typically required during the hot rolling stage. Therefore, it is inevitable that the steel will enter the two-phase region during the finishing rolling stage. The temperature inhomogeneity along the length and thickness of the same coil will lead to highly unstable rolling, resulting in poor control of thickness, width, and surface quality, which is detrimental to the final product quality control. It also results in a very low rolling success rate, hindering the stable mass production of silicon steel products.

[0003] In summary, the existing technology has the following problems: when non-oriented silicon steel enters the two-phase region during the hot rolling finishing stage, the rolling is unstable due to uneven rolling temperature, resulting in poor finished product quality, more scrap steel, and a very low rolling hit rate, which is not conducive to achieving stable mass production of silicon steel products. Summary of the Invention

[0004] This invention provides a method for rolling non-oriented silicon steel, and more particularly a method for improving the rolling stability of non-oriented silicon steel. This method addresses the problem of unstable rolling due to uneven rolling temperature during the hot rolling and finishing stages of non-oriented silicon steel, which leads to poor finished product quality and excessive scrap. It also greatly improves the success rate of hot rolling of non-oriented silicon steel, thereby achieving stable mass production of silicon steel products.

[0005] Therefore, the present invention proposes a method for improving the rolling stability of non-oriented silicon steel, the method comprising the following steps:

[0006] Step 1, Heating Stage: Control the temperature and heating time of the billet in the heating furnace to ensure uniform temperature distribution of the billet in a short time.

[0007] Step 2, Rough Rolling Stage: Set the number of reciprocating passes for each rolling pass and ensure the consistency of the bite speed, rolling speed, and ejection speed for each rolling pass.

[0008] Step 3, Finishing Rolling Stage: Control the finishing rolling inlet temperature to ≤960℃;

[0009] The chemical composition of non-oriented silicon steel by weight percentage is as follows: C≤0.003%, Si: 0.4-0.6%, Mn: 0.2-0.3%, P: 0.06-0.08%, S≤0.008%, Als: 0.15-0.25%, O≤0.003%, N≤0.0028%, with the remainder being iron and unavoidable impurities.

[0010] Furthermore, in step one, the heating of the billet in the heating furnace is divided into a first heating section, a second heating section, a third heating section, and a soaking section, wherein:

[0011] The temperature of the heating section is controlled at 1100±30℃;

[0012] The temperature of the second heating section is controlled at 1140±30℃;

[0013] The temperature of the three heating sections is controlled at 1140±20℃;

[0014] The temperature of the heat exchange section is controlled at 1130±20℃.

[0015] Furthermore, in step one, the firing time is controlled to be 120–150 min.

[0016] Furthermore, in step two, the number of reciprocating passes in the rolling process is 5.

[0017] Furthermore, the bite speed, rolling speed, and discharge speed of the first pass are all 1.5 m / s; the bite speed, rolling speed, and discharge speed of the second pass are all 2.0 m / s; the bite speed, rolling speed, and discharge speed of the third pass are all 2.5 m / s; the bite speed, rolling speed, and discharge speed of the fourth pass are all 3.0 m / s; and the bite speed, rolling speed, and discharge speed of the fifth pass are all 2.5 m / s.

[0018] Furthermore, the final rolling temperature of the finishing rolling stage is 870±20℃.

[0019] Furthermore, the method for improving the rolling stability of non-oriented silicon steel also includes a layer cooling stage, wherein the coiling temperature is controlled at 710±20℃ during the layer cooling stage.

[0020] Furthermore, the temperature of the first heating section is 1075℃, the temperature of the second heating section is 1130℃, the temperature of the third heating section is 1132℃, and the temperature of the heat spreader section is 1131℃.

[0021] Furthermore, the temperature of the first heating section is 1116℃, the temperature of the second heating section is 1155℃, the temperature of the third heating section is 1156℃, and the temperature of the heat spreader is controlled at 1152℃.

[0022] Furthermore, the temperature of the first heating section is 1094℃, the temperature of the second heating section is 1142℃, the temperature of the third heating section is 1145℃, and the temperature of the heat spreader is controlled at 1143℃.

[0023] Compared with existing technologies, this invention achieves the following beneficial effects: The method for improving the rolling stability of non-oriented silicon steel provided by this invention is carried out according to the following steps: Step 1, Heating stage: Controlling the temperature and heating time of the billet in the heating furnace to ensure uniform temperature distribution of the billet in a short time; Step 2, Rough rolling stage: Setting the number of reciprocating passes for each rolling pass and ensuring consistency in the bite speed, rolling speed, and ejection speed of each rolling pass; Step 3, Finish rolling stage: Controlling the entry temperature of the finish rolling mill to ≤960℃. The process design of this invention solves the problem of scrap caused by rolling instability in the finish rolling stage of non-oriented silicon steel without requiring additional specific temperature uniformity improvement equipment, greatly improving the hit rate of non-oriented silicon steel in the hot rolling stage, effectively reducing production costs, and resulting in significant economic and social benefits. Attached Figure Description

[0024] Figure 1 This is a thickness curve diagram of Embodiment 1 of the present invention;

[0025] Figure 2 This is a thickness curve diagram of Embodiment 2 of the present invention;

[0026] Figure 3 This is a thickness curve diagram of Embodiment 3 of the present invention;

[0027] Figure 4 This is a thickness curve for Comparative Example 1;

[0028] Figure 5 This is a thickness curve for Comparative Example 2.

[0029] Reference numerals: 1. Product thickness; 2. Target thickness; 3. Upper limit of thickness; 4. Lower limit of thickness. Detailed Implementation

[0030] To provide a clearer understanding of the technical features, objectives, and effects of this invention, the invention is now described.

[0031] The purpose of this invention is to provide a method for improving the rolling stability of non-oriented silicon steel. This invention, through the design of heating process, roughing process and finishing process, eliminates the need for additional intermediate billet heat preservation roller table, hot coil box and other temperature uniformity improvement equipment. Using this method can greatly improve the rolling stability of non-oriented silicon steel in the hot rolling stage, and the surface quality, edge quality, thickness and width and precision can all be well controlled.

[0032] I. To achieve the above objectives, the present invention adopts the following technical solution:

[0033] Because silicon steel has poor thermal conductivity, it is prone to uneven heating, and its high-temperature mechanical properties are quite sensitive to temperature. Therefore, during the hot rolling stage, uneven temperature can easily lead to rolling instability.

[0034] The present invention provides a method for improving the rolling stability of non-oriented silicon steel. The non-oriented silicon steel has the following chemical composition by weight percentage: C ≤ 0.003%, Si: 0.4-0.6%, Mn: 0.2-0.3%, P: 0.06-0.08%, S ≤ 0.008%, Als: 0.15-0.25%, O ≤ 0.003%, N ≤ 0.0028%, and the thickness of the non-oriented silicon steel is 2.5-3.0 mm. The method includes the following steps:

[0035] (1) Heating stage: The present invention uses a three-stage high-temperature heating method to make the temperature of the billet uniform in a shorter time;

[0036] Billet heating: First heating section temperature 1100±30, second heating section temperature 1140±30, third heating section temperature 1140±20, soaking section temperature 1130±20, heating time 120~150min;

[0037] (2) Rough rolling stage: By controlling the bite speed, rolling speed and blasting speed of each pass to be consistent, the uniformity of longitudinal temperature of the strip is ensured as much as possible.

[0038] After being heated and homogenized in a heating furnace, the billet is sent to the roughing mill. After being rolled back and forth five times in the roughing mill, it is sent to the finishing mill. The roughing rolling process is shown in Table 1.

[0039] Table 1 Rough Rolling Process

[0040] 1 1.5m / s 1.5m / s 1.5m / s 2 2.0m / s 2.0m / s 2.0m / s 3 2.5m / s 2.5m / s 2.5m / s 4 3.0m / s 3.0m / s 3.0m / s 5 2.5m / s 2.5m / s 2.5m / s

[0041] (3) Finishing stage: After continuous rolling on the seven-stand finishing mill, the rolling process is cooled by layer cooling and then coiled by the coiler.

[0042] Finishing rolling: Finishing entry temperature ≤960℃, finishing rolling temperature 870±20℃;

[0043] Laminar cooling: winding temperature 710±20℃;

[0044] By controlling the finishing mill inlet temperature to ≤960℃, the phase transformation point is moved forward to the first two stands of the finishing mill, avoiding the drastic fluctuations caused by phase transformation in the high-speed thin strip steel in the later stands. Ultimately, stable rolling of non-oriented silicon steel in the hot rolling stage is achieved with high production efficiency.

[0045] II. Implementation Examples

[0046] (1) The present invention provides a method for improving the rolling stability of non-oriented silicon steel. The heating processes of each embodiment and comparative example are shown in Table 2.

[0047] Table 2 shows the specific heating processes for each example and comparative case.

[0048]

[0049] (2) The roughing process corresponding to each example product and comparative example in Table 1 is shown in Table 3.

[0050] Table 3 shows the specific roughing processes for each example and comparative case.

[0051]

[0052] (3) Table 4 shows the fine rolling entry temperature and rolling hit rate when producing 100 coils of products using the corresponding hot rolling process in the examples and comparative examples.

[0053] Table 4. Finishing mill inlet temperature and rolling hit rate for each example and comparative case.

[0054] Example 1 955 98.6 Example 2 952 99.3 Example 3 946 98.8 Comparative Example 1 980 91.6 Comparative Example 2 976 92.5

[0055] (4) Plot thickness curves for each embodiment and comparative example with the longitudinal position of the non-oriented silicon steel sheet as the abscissa (unit: meters) and the thickness (unit: mm) as the ordinate. Figures 1-3 The following are thickness curves for each embodiment. Figures 4-5 The thickness curves are for each comparison. Figure 1 The values ​​at the two endpoints of the vertical axis are 2.1mm-3.4mm, and the numerical curve is 2.7mm-2.8mm. The results show that the thickness fluctuation of each embodiment of the present invention is within ±0.05mm, while the thickness fluctuation of the comparative example is larger, within ±0.1mm. Table 5 shows the thickness control of the embodiments and the comparative example, indicating that the non-oriented silicon steel produced by the present invention has small thickness fluctuation and good stability.

[0056] Table 5 Thickness control for each example and comparative example

[0057]

[0058]

[0059] The method for improving the rolling stability of non-oriented silicon steel provided by this invention, through the design of heating, roughing, and finishing processes, employs a three-stage high-temperature heating method to achieve uniform temperature of the cast billet in a short time. In the roughing stage, by controlling the bite speed, rolling speed, and stripping speed of each pass consistently, the longitudinal temperature uniformity of the strip is ensured. In the finishing stage, by controlling the finishing mill inlet temperature to ≤960℃, the phase transformation point is moved forward to the first two stands of the finishing mill, ultimately achieving stable rolling of non-oriented silicon steel in the hot rolling stage with high production efficiency. This invention solves the problem of scrap caused by rolling instability in the finishing stage of hot rolling of non-oriented silicon steel without requiring additional specific temperature uniformity improvement equipment, greatly improving the hit rate of hot rolling of non-oriented silicon steel. Using this invention for the hot rolling production of non-oriented silicon steel significantly improves rolling stability, noticeably reduces surface and edge defects, significantly reduces thickness and width fluctuations, and effectively reduces production costs, resulting in significant economic and social benefits.

[0060] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. The various components of the present invention can be combined with each other without conflict. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for improving the rolling stability of non-oriented silicon steel, characterized in that, The steps include the following: Step 1, Heating Stage: Controlling the temperature and heating time of the billet in the heating furnace; Step 2, Rough Rolling Stage: Set the number of reciprocating passes for each rolling pass and ensure the consistency of the bite speed, rolling speed, and ejection speed for each rolling pass. Step 3, Finishing Rolling Stage: Control the finishing rolling inlet temperature to ≤960℃; The chemical composition of non-oriented silicon steel by weight percentage is as follows: C≤0.003%, Si: 0.4-0.6%, Mn: 0.2-0.3%, P: 0.06-0.08%, S≤0.008%, Als: 0.15-0.25%, O≤0.003%, N≤0.0028%, with the remainder being iron and unavoidable impurities; In step one, the heating of the billet in the heating furnace is divided into a first heating section, a second heating section, a third heating section, and a soaking section, wherein: The temperature of the heating section is controlled at 1100±30℃; The temperature of the second heating section is controlled at 1140±30℃; The temperature of the three heating sections is controlled at 1140±20℃; The temperature of the heat spreader is controlled at 1130±20℃; After being heated and homogenized in a heating furnace, the billet is sent to the roughing mill, and after being rolled back and forth five times in the roughing mill, it is sent to the finishing mill. The bite speed, rolling speed, and discharge speed for the first pass are all 1.5 m / s; the bite speed, rolling speed, and discharge speed for the second pass are all 2.0 m / s; the bite speed, rolling speed, and discharge speed for the third pass are all 2.5 m / s; the bite speed, rolling speed, and discharge speed for the fourth pass are all 3.0 m / s; and the bite speed, rolling speed, and discharge speed for the fifth pass are all 2.5 m / s. During the finishing rolling stage and the layer cooling stage, the coiling temperature is controlled at 710±20℃.

2. The method for improving the rolling stability of non-oriented silicon steel as described in claim 1, characterized in that, In step one, the in-fire time is controlled to be 120-150 minutes.

3. The method for improving the rolling stability of non-oriented silicon steel as described in claim 1, characterized in that, The final rolling temperature of the finishing rolling stage is 870±20℃.

4. The method for improving the rolling stability of non-oriented silicon steel as described in claim 1, characterized in that, The temperature of the first heating section is 1075℃, the temperature of the second heating section is 1130℃, the temperature of the third heating section is 1132℃, and the temperature of the heat spreader section is 1131℃.

5. The method for improving the rolling stability of non-oriented silicon steel as described in claim 1, characterized in that, The temperature of the first heating section is 1094℃, the temperature of the second heating section is 1142℃, the temperature of the third heating section is 1145℃, and the temperature of the heat spreader is controlled at 1143℃.

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