Low-aging brittleness non-oriented silicon steel normalized plate and production method thereof

Abstract

The invention belongs to the technical field of electrical steel, and particularly relates to a low-aging brittleness non-oriented silicon steel normalized plate and a production method thereof, and the steel comprises the following chemical components in percentage by weight: less than or equal to 0.005% of C, 2.5%-3.6% of Si, 0.2%-0.8% of Mn, 0.5%-1.2% of Al, less than or equal to 0.003% of N, 0.04%-0.06% of Sn, 0.0075%-0.1% of Sb, and the balance of Fe and inevitable impurities. Compared with the prior art, the method has the beneficial effects that compared with a traditional non-oriented silicon steel normalized plate, the normalized coil prepared through the method can still keep high cold deformation capacity after being stored for a long time, and edge cracking and strip breakage of silicon steel cold rolling are restrained.

Description

Technical Field

[0001] The invention belongs to the technical field of electrical steel, and in particular relates to a low-aging brittle non-oriented silicon steel normalized plate and a production method thereof. Background Art

[0002] With the rapid development of the new energy industry, high-efficiency motors and new energy vehicle drive motors have further improved the product performance requirements of non-oriented silicon steel. Non-oriented silicon steel is developing in the direction of high comprehensive performance and thinning. Non-oriented silicon steel often improves its magnetic properties by adding silicon and aluminum elements, but the increase in silicon and aluminum content will increase the brittleness of the material, reduce its cold deformation ability, and increase the occurrence of edge cracks and broken strips in the cold rolling process.

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

[0004] High silicon aluminum non-oriented silicon steel normalized plate generally has a relatively high ductile-brittle transition temperature due to its large grain size and high alloy composition. Preheating is generally used to reduce the brittleness of the material 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 in the normalizing stage introduce internal stress and dislocations into the steel plates. As the inventory time of normalized coils increases, interstitial atoms such as C and N tend to gather at defects such as dislocations to form Cottrell gas masses, thereby increasing the brittleness of the material. In the actual production process of non-oriented silicon steel, when the production capacity of the normalizing unit is greater than the production capacity of the subsequent rolling mill, an inventory backlog of normalized coils will occur. When the silicon and aluminum elements in non-oriented silicon steel are high, the risk of aging brittleness is more significant. The high silicon and aluminum normalized coils will naturally age over time, and their material brittleness will increase significantly, thereby increasing the risk of edge cracking and strip breakage in subsequent cold rolling, thereby reducing the yield rate and production efficiency. Summary of the invention

[0006] The present invention provides a low-aging brittle non-oriented silicon steel normalized plate and a production method thereof. The present invention reduces the low-aging brittleness of the non-oriented silicon steel normalized plate by adding Sb element, and obtains the silicon steel normalized plate that is easy to cold roll through a suitable preparation method. On the one hand, the risks of cold-rolled edge cracking and strip breakage are reduced, and on the other hand, the inventory time of the silicon steel normalized coil is extended, thereby improving the robustness of the silicon steel production system.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A low-aging brittle non-oriented silicon steel normalized plate, the chemical composition of the steel is as follows by weight percentage: 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 rest is Fe and unavoidable impurities.

[0009] The non-oriented silicon steel has a maximum interval of 12 days from normalization to cold rolling without edge cracks or strip breaks during cold rolling.

[0010] Sb is considered to be beneficial to reduce the aging brittleness of normalized non-oriented silicon steel plates. Research results show that Sb has high vacancy binding energy and can inhibit the rising rate of the natural aging brittleness of the material to a certain extent. Figure 1 , showing the changing trend of elongation of normalized plates of 0.003C-3.1Si-0.27Mn-1.0Al-0.05Sn non-oriented silicon steel with different Sb contents with aging time: with the increase of aging time, the plasticity of the normalized plates shows a downward trend; after 7 days of aging, the elongation of the normalized plates with conventional composition decreases from 18% to below 8%. When the Sb content reaches 75ppm, the normalized plates only drop to below 8% on the 17th day.

[0011] A method for producing a low-aging brittle non-oriented silicon steel normalized plate adopts the following basic process path: ironmaking-steelmaking-continuous casting-hot rolling-normalizing to prepare a normalized coil, followed by cold rolling-annealing-coating; the normalizing temperature is: 900-1000°C; the normalizing belt speed is ≥25mpm. The average grain size of the normalized plate is guaranteed to be ≤160μm.

[0012] By controlling the normalizing temperature and belt speed to control the degree of recovery and recrystallization, on the one hand, recrystallization is used to improve the hot rolling organization and hot rolling deformation texture, and improve 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. In general, the tough-brittle transition temperature of the material is related to the composition and grain size. The larger the grain size, the higher the tough-brittle transition temperature. Under the same aging conditions, the worse the deformation ability of the material during cold rolling, the more likely it is to have cold rolling edge cracks and belt breakage.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] Compared with traditional non-oriented silicon steel normalized plates, the normalized coils prepared by the present invention can still maintain a high cold deformation capacity after long-term storage, inhibiting the occurrence of cold-rolled edge cracks and strip breaks of silicon steel, reducing costs and increasing efficiency by reducing rolling defects and accidents; on the other hand, it extends the inventory time of silicon steel normalized coils, improves the robustness of the silicon steel production system, and improves the flexibility of production scheduling.

[0015] The preliminary experimental and trial production results of the present invention show that the addition of Sb can significantly delay aging brittleness, and the trial production results show that the addition of Sb will not deteriorate product performance. A certain steel plant had serious problems with cold-rolled strip breakage of high-silicon aluminum non-oriented silicon steel, low production efficiency and low yield. Through the implementation of this invention, the yield of the original variety of high-silicon aluminum non-oriented silicon steel 30ADG1500 of the steel plant has increased from less than 50% to 75%, of which the cold-rolled yield has increased to about 95%, and the production efficiency has increased by 300%, achieving a monthly production of 1,000 tons for the first time. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0017] Figure 2 The present invention discloses a production process path for a low-aging brittle non-oriented silicon steel normalized plate. DETAILED DESCRIPTION

[0018] The specific implementation modes of the present invention are further described below in conjunction with examples. The following examples are used to specifically illustrate the contents of the present invention. These examples are only general descriptions of the contents of the present invention and do not limit the contents of the present invention.

[0019] The present invention is used for the production of high-grade non-oriented silicon steel. Through the solidification cold rolling process, the brittleness of the normalized plate is measured according to the number of cold rolling edge cracks. In the embodiment, there are 4 furnaces of test steel, wherein the composition of test steel #1 is 0.002% C-3.12% Si-0.27% Mn-1.0% Al-0.002% N-0.05% Sn; the composition of test steel #2 is 0.002% C-3.10% Si-0.25% Mn-1.0% Al-0.002% N-0.05% Sn-(0.0075-0.1)% Sb; the composition of test steel #3 is 0.002% C-2.9 2%Si-0.22%Mn-0.85%Al-0.002%N-0.04%Sn; 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-(0.0075~0.1)Sb; among them, test steel #1 and test steel #3 are comparative examples, test steel #2 and test steel #4 are embodiments of the present invention, and the production situation of each furnace of test steel is shown in Table 1.

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

[0021]

[0022]

[0023]

[0024] In the embodiments of the present invention, Sb element is added to two kinds of non-oriented silicon steel respectively, and the aging brittleness thereof is significantly reduced. The number of strip breaks of comparative test steel #1 and test steel #3 increased slightly during cold rolling after 5 days of normalization, and the strip breaks were significant after 10 days of normalization. The comparative test steel #1 had an average of 3.25 strip breaks per roll, and the test steel #3 had an average of 1.33 strip breaks per roll, showing significant brittleness. In the embodiments of the present invention, test steel #2 and test steel #4 were added with (0.0075-0.1) ppm Sb to suppress the aging brittleness, and the average number of strip breaks per roll after cold rolling was 0 after 12 days of normalization. By adding Sb to extend the interval time from normalization to cold rolling, the aging brittleness of normalized non-oriented silicon steel plates is reduced, providing a new idea for domestic peers to solve the problem of cold rolling brittleness 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: 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 rest is 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 from normalization to cold rolling without edge cracks or strip breaks during cold rolling.

3. A method for producing a low-aging brittle non-oriented silicon steel normalized plate as claimed in claim 1 or 2, wherein the basic process path adopted is as follows: ironmaking-steelmaking-continuous casting-hot rolling-normalizing to prepare a normalized coil, and then cold rolling-annealing-coating; characterized in that: The normalizing temperature is 900-1000°C.

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 ≤160 μm.

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