Normalized non-oriented silicon steel plate having low susceptibility to aging embrittlement, and production method therefor

Abstract

The present invention belongs to the technical field of electrical steel, and in particular relates to a normalized non-oriented silicon steel plate having low susceptibility to aging embrittlement, and a production method therefor. The chemical components in the steel are, in percentages by weight: C≤0.005%, Si: 2.5%-3.6%, Mn: 0.2%-0.8%, Al: 0.5%-1.2%, N≤0.003%, Sn: 0.04%-0.06%, Sb: 0.0075%-0.1%, and the balance of Fe and inevitable impurities. In comparison with the prior art, the present invention has the beneficial effects of: compared with a traditional normalized non-oriented silicon steel plate, a normalized coil prepared in the present invention can still maintain a high cold deformability after long-term storage, thereby inhibiting the occurrence of edge cracks and strip breakage during cold rolling of silicon steel.

Description

A normalized plate of low-aging brittle non-oriented silicon steel and its production method Technical Field

[0001] This invention belongs to the field of electrical steel technology, and particularly relates to a low-aging brittle non-oriented silicon steel normalized plate and its production method. Background Technology

[0002] With increasing environmental awareness and the deepening implementation of the national "dual-carbon" strategy, the new energy industry is developing rapidly. The performance requirements for non-oriented silicon steel products, such as high-efficiency motors and drive motors for new energy vehicles, are further increasing. Non-oriented silicon steel is developing towards higher comprehensive performance and thinner profiles. Non-oriented silicon steel often improves its magnetic properties by adding silicon and aluminum, but increasing the silicon and aluminum content increases the material's brittleness, reduces its cold deformation ability, and increases the occurrence of edge cracks and strip breaks during the cold rolling process.

[0003] Production practice shows that the brittleness of cold-rolled raw materials, i.e., normalized plate materials, is related to both cold rolling temperature and aging time.

[0004] High-silicon aluminum non-oriented silicon steel normalized plates generally have a relatively high ductile-brittle transition temperature due to their larger grain size and higher alloy content. Preheating is typically used to reduce the material's brittleness during cold rolling. Patent CN114769336A discloses a method for preheating normalized steel coils in a water bath; patent CN104399749A requires preheating the normalized coil to 60 to 80°C after uncoiling.

[0005] On the other hand, the trimming and coiling processes during the normalizing stage introduce internal stress and dislocations into the steel sheet. As the normalized coil inventory time increases, interstitial atoms such as C and N tend to accumulate at dislocations and other defects, forming Curtill atmospheres, which in turn increases the material's brittleness. In the actual production process of non-oriented silicon steel, when the capacity of the normalizing mill exceeds that of the subsequent rolling mill, a backlog of normalized coil inventory will occur. When the silicon and aluminum content in non-oriented silicon steel is high, the risk of aging brittleness is more significant. High-silicon and high-aluminum normalized coils will naturally age over time, resulting in a substantial increase in material brittleness, which in turn increases the risk of edge cracking and strip breakage during subsequent cold rolling, thereby reducing yield and production efficiency. Summary of the Invention

[0006] This invention provides a low-aging brittleness non-oriented silicon steel normalized plate and its production method. This invention reduces the low-aging brittleness of non-oriented silicon steel normalized plate by adding Sb element, and obtains silicon steel normalized plate that is easy to cold roll through a suitable preparation method. On the one hand, it reduces the risk of edge cracking and strip breakage during cold rolling, and on the other hand, it extends the storage time of silicon steel normalized coils and improves the robustness of silicon steel production system.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] A normalized plate of low-aging brittle non-oriented silicon steel, wherein the chemical composition of the steel by weight percentage is: C≤0.005%, Si: 2.5%~3.6%, Mn: 0.2%~0.8%, Al: 0.5%~1.2%, N≤0.003%, Sn: 0.04%~0.06%, Sb: 0.0075%~0.1%, with the remainder being Fe and unavoidable impurities.

[0009] The non-oriented silicon steel has a maximum interval of 12 days between normalizing and cold rolling. Cold rolling results in no edge cracks or broken strips.

[0010] Sb is considered beneficial in reducing the aging brittleness of normalized non-oriented silicon steel plates. Research results show that Sb has high vacancy bonding energy, which can, to some extent, inhibit the rate of increase in the natural aging brittleness of the material. Figure 1 shows the elongation trend of normalized non-oriented silicon steel plates with different Sb contents (0.003C-3.1Si-0.27Mn-1.0Al-0.05Sn) over aging time: with increasing aging time, the plasticity of the normalized plate decreases; the elongation of the normalized plate with conventional composition decreases from 18% to below 8% after 7 days of aging, while when the Sb content reaches 75 ppm, the elongation only drops below 8% on the 17th day.

[0011] A method for producing normalized plates of low-aging brittle non-oriented silicon steel employs the following basic process path: ironmaking-steelmaking-continuous casting-hot rolling-normalizing to produce normalized coils, followed by cold rolling-annealing-coating; the normalizing temperature is 900~1000℃; the normalizing belt speed is ≥25mpm. This ensures that the average grain size of the normalized plate is ≤160μm.

[0012] By controlling the normalizing temperature and belt speed, the degree of recovery and recrystallization can be controlled. On the one hand, recrystallization can be used to improve the hot-rolled microstructure and hot-rolled deformation texture, thereby enhancing the magnetic properties of the product. On the other hand, the degree of grain growth should be controlled to ensure that the average grain size of the normalized plate is ≤160μm. Generally, the ductile-brittle transition temperature of a material is related to its composition and grain size. The larger the grain size, the higher the ductile-brittle transition temperature. Under the same aging conditions, the material's deformation capacity during cold rolling is poorer, and it is more prone to edge cracking and strip breakage during cold rolling.

[0013] Compared with the prior art, the beneficial effects of the present invention are:

[0014] Compared with traditional non-oriented silicon steel normalized plates, the normalized coils prepared by this invention can still maintain a high cold deformation capacity after long-term storage, suppressing the occurrence of edge cracks and strip breaks in silicon steel during cold rolling. This reduces costs and increases efficiency by reducing rolling defects and accidents. On the other hand, it extends the storage time of silicon steel normalized coils, improves the robustness of the silicon steel production system, and increases the flexibility of production scheduling.

[0015] Preliminary experimental and trial production results of this invention show that the addition of Sb can significantly delay aging embrittlement, and the trial production results show that the addition of Sb does not deteriorate product performance. A steel plant suffered from severe strip breakage during cold rolling of high-silicon-aluminum non-oriented silicon steel, resulting in low production efficiency and low yield. Through the implementation of this invention, the yield of the plant's high-silicon-aluminum non-oriented silicon steel 30ADG1500 has increased from less than 50% to 75%, with the cold-rolled yield increasing to approximately 95%, resulting in a 300% increase in production efficiency and achieving monthly production of thousands of tons for the first time. Attached Figure Description

[0016] Figure 1 shows the trend of elongation of normalized plates of non-oriented silicon steel with different Sb contents over aging time.

[0017] Figure 2 shows the production process path of a low-aging brittle non-oriented silicon steel normalized plate according to the present invention. Detailed Implementation

[0018] The specific embodiments of the present invention will be further described below with reference to the examples. The following examples are used to specifically illustrate the content of the present invention. These examples are only general descriptions of the content of the present invention and do not limit the content of the present invention.

[0019] This invention is used in the production of high-grade non-oriented silicon steel. Through a curing cold rolling process, the brittleness of the normalized plate is measured by the number of edge cracks and breakages during cold rolling. The example involves four heats of test steel. Test steel #1 has a composition of 0.002% C, 3.12% Si, 0.27% Mn, 1.0% Al, 0.002% N, and 0.05% Sn; test steel #2 has a composition of 0.002% C, 3.10% Si, 0.25% Mn, 1.0% Al, 0.002% N, 0.05% Sn, and (0.0075~0.1)% Sb; and test steel #3 has a composition of 0.002% C, 2.9% Si, and 0.9% Sb. The composition of test steel #4 is 0.002% C, 2.95% Si, 0.24% Mn, 0.85% Al, 0.002% N, 0.04% Sn, and (0.0075~0.1)Sb. Test steel #1 and test steel #3 are comparative examples, while test steel #2 and test steel #4 are embodiments of the present invention. The production details of each heat of test steel are shown in Table 1.

[0020] Table 1. Data from embodiments of the present invention and comparative examples.

[0021] In this invention, Sb was added to two types of non-oriented silicon steel, significantly reducing their aging brittleness. Comparative test steel #1 and test steel #3 showed a slight increase in the number of strip breaks during cold rolling after 5 days of normalizing, but significant strip breaks occurred after 10 days of normalizing. Comparative test steel #1 averaged 3.25 strip breaks per coil, while test steel #3 averaged 1.33 strip breaks per coil, exhibiting significant brittleness. In this invention, the addition of (0.0075–0.1) ppm Sb to test steels #2 and #4 suppressed aging brittleness, resulting in 0 strip breaks per coil after 12 days of normalizing. By adding Sb to extend the interval between normalizing and cold rolling, the aging brittleness of normalized non-oriented silicon steel plates is reduced, providing a new approach for domestic researchers to address the cold-rolling brittleness problem of silicon steel.

Claims

1. A low-aging brittle non-oriented silicon steel normalized plate, characterized in that, The chemical composition of the steel, by weight percentage, is as follows: C ≤ 0.005%, Si: 2.5%–3.6%, Mn: 0.2%–0.8%, Al: 0.5%–1.2%, N ≤ 0.003%, Sn: 0.04%–0.06%, Sb: 0.0075%–0.1%, with the remainder being Fe and unavoidable impurities.

2. The low-aging brittle non-oriented silicon steel normalized plate according to claim 1, characterized in that, The non-oriented silicon steel has a maximum interval of 12 days between normalizing and cold rolling. Cold rolling results in no edge cracks or broken strips.

3. A method for producing low-aging brittle non-oriented silicon steel normalized plates as described in claim 1 or 2, comprising the following basic process path: ironmaking - steelmaking - continuous casting - hot rolling - normalizing to produce normalized coils, followed by cold rolling - annealing - coating; characterized in that, The normalization temperature is 900–1000℃.

4. The method for producing low-aging brittle non-oriented silicon steel normalized plate according to claim 3, characterized in that, Normalized belt speed ≥25mpm.

5. The method for producing low-aging brittle non-oriented silicon steel normalized plate according to claim 3, characterized in that, The average grain size of the normalized plate is ≤160μm.

Images