High-strength non-oriented electrical steel for new energy automobile drive rotor and manufacturing method of high-strength non-oriented electrical steel

Abstract

The invention relates to the technical field of non-oriented electrical steel, in particular to high-strength non-oriented electrical steel for a new energy automobile drive rotor and a manufacturing method thereof.The high-strength non-oriented electrical steel for the new energy automobile drive rotor comprises, by weight, 0%-0.002% of C, 2.5%-3.5% of Si, 0.25%-0.75% of Mn, 0.50%-1.50% of Al, smaller than or equal to 0.01% of P, smaller than or equal to 0.002% of S, 0.02%-0.20% of Sn and the balance Fe and inevitable impurities. And the balance of iron and inevitable impurities. According to the invention, high structural strength and low medium-high frequency magnetic performance are obtained under the conditions of low cost and low iron loss.

Description

Technical Field

[0001] The present invention relates to the technical field of non-oriented electrical steel, and in particular to a high-strength non-oriented electrical steel for a new energy vehicle drive rotor and a manufacturing method thereof. Background Art

[0002] Due to the complex operating conditions (such as high and low temperature, high frequency, acceleration, frequent vibration, overload, etc.), the performance requirements of electric vehicle drive motors are very different from those of traditional industrial motors. They must have high power density and high torque as well as a certain material strength. Therefore, for the preparation of drive motor core materials, non-oriented silicon steel is required to have good magnetic properties and a certain strength. However, for silicon steel, in the process of improving strength indicators, the electromagnetic properties, especially the iron loss, will inevitably be reduced. How to reconcile the contradiction between the material's magnetic properties and strength indicators has become the key direction and difficulty in the research and development of silicon steel for drive motors in recent years.

[0003] Traditional high-grade silicon steel can reach a maximum strength of 420-450MPa through the design of the proportion of main alloying elements such as Si, Als, and Mn combined with appropriate production processes, while the strength of high-speed drive motor rotors is required to reach more than 600MPa. Microalloying has become an effective way to further improve the strength of silicon steel materials for drive motor rotors. The Chinese invention patent with the authorization announcement number CN111321344B discloses a high-strength cold-rolled non-oriented electrical steel for electric vehicle drive motors and its production method. The method controls the heating rate during annealing by adding strengthening elements such as Cu and Nb and microalloying elements such as Sn and Sb to meet the requirements of high strength and low loss of electrical steel materials for electric vehicle drive motor rotors, and effectively reconciles the contradiction between the material's magnetic properties and strength indicators. Although the non-oriented electrical steel improves the yield strength while ensuring the magnetic induction, its iron loss is high, and it needs to add Cu, Nb, Sn, and Sb elements, which is costly. Summary of the invention

[0004] The purpose of the present invention is to address the defects of the prior art and provide a high-strength non-oriented electrical steel and a manufacturing method for a new energy vehicle drive rotor, which achieves higher structural strength and lower medium and high frequency magnetic properties at a lower cost and low iron loss.

[0005] In order to solve the above technical problems, in the first aspect, the present invention provides a high-strength non-oriented electrical steel for a new energy vehicle drive rotor, comprising the following components in weight percentage: C: 0-0.002%, Si: 2.5-3.5%, Mn: 0.25-0.75%, Al: 0.50-1.50%, P: ≤0.01%, S: ≤0.002%, Sn: 0.02-0.20%, and the balance is iron and unavoidable impurities.

[0006] C: The present invention controls the C content mainly to ensure the strength of the hot-rolled plate, but too high a C content will reduce the toughness of the steel plate, and C will damage the magnetic properties of the steel plate whether it exists in the form of solid solution or cementite. The present invention limits the C content to ≤0.002%.

[0007] Si: As the Si content increases, the strength of the steel plate increases, the resistivity increases, the hysteresis loss decreases, and the iron loss decreases. Therefore, the Si content in the steel should be reduced in the present invention. The Si content in the present invention is 2.5-3.5%.

[0008] Mn: Mn is beneficial to increase the resistivity of the material, reduce hysteresis loss, increase the rollability of the hot-rolled plate, and improve the strength through solid solution strengthening. Therefore, the present invention increases the Mn content to 0.25-0.75%.

[0009] Al: Al has the same function as Si, and has the functions of increasing the strength of the steel plate, reducing magnetic induction, and reducing iron loss. Therefore, the Al content is controlled to be 0.50-1.50% in the present invention.

[0010] P: P is promoted by Sn to segregate, refine grains, increase strength, and improve texture. However, Fe3P segregation will make the steel plate brittle and reduce toughness. Therefore, the present invention controls P≤0.010%.

[0011] S: S and Mn in steel can form plastic MnS inclusions to reduce hot brittleness, but it will cause the strip steel to form a banded structure, reduce the toughness and formability of the steel plate, and S has a great influence on the magnetic properties. The present invention controls the S content to ≤0.002%.

[0012] Sn: Sn will segregate at the original grain boundary during hot rolling, and promote the segregation of P, hindering the growth of grains, making the grains finer, and improving the strength of the steel plate. However, grain refinement will lead to increased hysteresis loss. Since the segregation of Sn and P will improve the texture and reduce the influence of segregation on magnetic induction, the present invention controls the Sn content to 0.02-0.20%.

[0013] Furthermore, the grain size is 15 μm to 40 μm.

[0014] Furthermore, the following components are included in weight percentage: C: 0.0018%, Si: 3.35%, Mn: 0.49%, Al: 0.62%, P: ≤0.01%, S: 0.0009%, Sn: 0.12%.

[0015] In a second aspect, the present invention provides a method for manufacturing high-strength non-oriented electrical steel for a new energy vehicle drive rotor, comprising:

[0016] S1. Smelting;

[0017] S2, continuous casting;

[0018] S3, hot rolling;

[0019] S4, normalization, pickling;

[0020] S5, cold rolling, two-stage annealing;

[0021] S6. Apply coating.

[0022] Further, step S5 includes:

[0023] S51, cold rolling the rolling target to 60-80% of the target thickness;

[0024] S52, performing a first annealing, wherein the first annealing temperature is 860-1040° C.;

[0025] S53, cold rolling the rolling target to a target thickness, and performing a second annealing, wherein the second annealing temperature is 860-1040°C.

[0026] Furthermore, in step S52, the first annealing adopts a two-stage heating method: heating from 0 to 500°C at a heating rate of 10°C / s, and heating from 500 to 1040°C at a heating rate of 40°C / s. After heating to the first annealing temperature, it is kept warm for 5 to 20 seconds.

[0027] Furthermore, in step S53, the temperature is raised to the second annealing temperature at a heating rate of 40°C / s and kept at that temperature for 10 to 30 seconds.

[0028] Further, in step S5, the rolling target is annealed by a protective gas, and the protective gas includes 60% nitrogen and 40% hydrogen.

[0029] Furthermore, in step S3, the starting temperature of hot rolling is 1100-1200°C, the finishing temperature is 870-890°C, and the curling temperature is 620-680°C.

[0030] Furthermore, in step S4, the normalizing temperature is 920-980°C.

[0031] The beneficial effects of the present invention are:

[0032] 1. The present invention refines the grains by adding Sn elements, reduces the finished strips, and adopts a two-stage annealing method. By controlling the temperature and the heating rate, the grain size is controlled to be 15μm-40μm, and the favorable texture is optimized. Compared with the prior art, the non-oriented electrical steel of the present invention has high strength at a lower cost and lower medium and high frequency iron loss.

[0033] 2. Non-oriented electrical steel B of the present invention 50 =1.50-1.70T,W 1.0 / 400≤30.0W / Kg, yield strength R p0.2 ≥600MPa, tensile strength R m ≥650MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a microstructure diagram of the non-oriented electrical steel of the present invention. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] Example 1

[0037] The chemical composition (by mass percentage) of the present embodiment is as follows:

[0038] Table 1 Chemical composition of continuous casting slab Unit: %

[0039] C Si Sn Mn P S Al N 0.0018 3.35 0.12 0.49 ≤0.01 0.0009 0.62 0.0011

[0040] According to the chemical composition ratios in Table 1, steel is smelted and made: after smelting and continuous casting, the ingot thickness is 230 mm, the hot rolling start temperature is 1100-1200 ° C, the final rolling temperature is 870-890 ° C, the coiling temperature is 620-680 ° C, and the steel plate thickness is 1.9-2.2 mm; normalization and pickling, the normalization temperature is 920-980 ° C.

[0041] Then cold-roll to 0.15-0.2mm (60-80% of the target thickness, the target thickness is 0.25mm), the cold-rolled steel coil is subjected to the first annealing in a high-temperature tubular annealing furnace with a protective gas of 60% nitrogen and 40% hydrogen, the annealing temperature is 860-950℃, and a two-stage heating method is adopted: 0-500℃ is heated at a heating rate of 10℃ / s, 500-1040℃ is heated at a heating rate of 40℃ / s, and after heating to the first annealing temperature of 860-950℃, it is kept warm for 5-20s. Cold-roll to the target thickness of 0.25mm, and the second annealing is carried out, and the heating rate is increased to 860-950℃ at a heating rate of 40℃ / s.

[0042] After annealing, the steel coil is coated with a semi-organic coating to ensure insulation and interlayer resistance.

[0043] The magnetic induction intensity B of the non-oriented silicon electrical steel obtained by the above process is 50 1.547T, W 1.0 / 400 =29.87W / Kg, yield strength R 0.2 The tensile strength is 686.80MPa, and the tensile strength Rm It is 722.95MPa.

[0044] Example 2

[0045] The chemical composition (by mass percentage) of the present embodiment is as follows:

[0046] Table 2 Chemical composition of continuous casting slab Unit: %

[0047] C Si Sn Mn P S Al N 0.0018 3.35 0.12 0.49 ≤0.01 0.0009 0.62 0.0011

[0048] According to the chemical composition ratios in Table 2, steel is smelted and made: after smelting and continuous casting, the ingot thickness is 230 mm, the hot rolling start temperature is 1100-1200 ° C, the final rolling temperature is 870-890 ° C, the coiling temperature is 620-680 ° C, and the steel plate thickness is 1.9-2.2 mm; normalization and pickling, the normalization temperature is 920-980 ° C.

[0049] Then cold-roll to 0.15-0.2mm, the cold-rolled steel coil is annealed for the first time in a high-temperature tubular annealing furnace with a protective gas of 60% nitrogen and 40% hydrogen, the annealing temperature is 950-1040℃, and a two-stage heating method is adopted: 0-500℃ is heated at a heating rate of 10℃ / s, 500-1040℃ is heated at a heating rate of 40℃ / s, and after heating to the first annealing temperature of 950-1040℃, it is kept warm for 5-20s. Cold-roll to the target thickness of 0.25mm, and the second annealing is carried out, and the heating rate is increased to 950-1040℃ at a heating rate of 40℃ / s.

[0050] After annealing, the steel coil is coated with a semi-organic coating to ensure insulation and interlayer resistance.

[0051] The magnetic induction intensity B of the non-oriented silicon electrical steel obtained by the above process is 50 1.655T, W 1.0 / 400 =27.57W / Kg, yield strength R 0.2 The tensile strength is 622.32MPa, and the tensile strength R m It is 702.25MPa.

[0052] Comparative Example 1

[0053] The chemical composition (by mass percentage) of this comparative example is as follows:

[0054] Table 3 Chemical composition of continuous casting slab Unit: %

[0055]

[0056]

[0057] According to the chemical composition ratios in Table 3, steel is smelted and made: after smelting and continuous casting, the ingot thickness is 230 mm, the hot rolling start temperature is 1100-1200 ° C, the final rolling temperature is 870-890 ° C, the coiling temperature is 620-680 ° C, and the steel plate thickness is 1.9-2.2 mm; normalization and pickling, the normalization temperature is 920-980 ° C.

[0058] Then it is cold rolled to 0.25mm, and the cold rolled steel coil is annealed in a high temperature tubular annealing furnace with a protective gas of 60% nitrogen and 40% hydrogen at a temperature of 860-950°C. The annealed steel coil is coated with a semi-organic coating to ensure insulation and interlayer resistance.

[0059] The magnetic induction intensity B of the non-oriented silicon electrical steel obtained by the above process is 50 1.653T, W 1.0 / 400 =20.15W / Kg, yield strength R 0.2 The tensile strength R is 589.32MPa. m It is 671.23MPa.

[0060] Comparative Example 2

[0061] The chemical composition (by mass percentage) of this comparative example is as follows:

[0062] Table 4 Chemical composition of continuous casting slab Unit: %

[0063] C Si Sn Mn P S Al N 0.0018 3.35 0.12 0.49 ≤0.01 0.0009 0.62 0.0011

[0064] According to the chemical composition ratios in Table 4, steel is smelted and made: after smelting and continuous casting, the ingot thickness is 230 mm, the hot rolling start temperature is 1100-1200 ° C, the final rolling temperature is 870-890 ° C, the coiling temperature is 620-680 ° C, and the steel plate thickness is 1.9-2.2 mm; normalization and pickling, the normalization temperature is 920-980 ° C.

[0065] Then the cold rolled steel coil is annealed in a high temperature tubular annealing furnace with 60% nitrogen and 40% hydrogen as protective gas at a temperature of 950-1040°C. The annealed steel coil is coated with a semi-organic coating to ensure insulation and interlayer resistance.

[0066] The magnetic induction intensity B of the non-oriented silicon electrical steel obtained by the above process is 50 1.643T, W 1.0 / 400 =35.42W / Kg, yield strength R 0.2 The tensile strength is 687.13MPa, and the tensile strength R m It is 823.52MPa.

[0067] By comparing Example 1 and Example 2 with Comparative Example 1 and Comparative Example 2, it can be seen that the two-stage annealing treatment can ensure that the iron loss W is reduced while the magnetic induction intensity remains almost unchanged. 1.0 / 400 ≤30.0W / Kg, and yield strength R p0.2 ≥600MPa, tensile strength R m ≥650MPa.

[0068] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A high-strength non-oriented electrical steel for a new energy vehicle drive rotor, characterized in that: The invention comprises the following components in weight percentage: C: 0-0.002%, Si: 2.5-3.5%, Mn: 0.25-0.75%, Al: 0.50-1.50%, P: ≤0.01%, S: ≤0.002%, Sn: 0.02-0.20%, and the balance is iron and inevitable impurities.

2. The high-strength non-oriented electrical steel for drive rotor of new energy vehicles according to claim 1, characterized in that: The grain size is 15μm~40μm.

3. The high-strength non-oriented electrical steel for drive rotor of new energy vehicles according to claim 1, characterized in that: The invention comprises the following components in weight percentage: C: 0.0018%, Si: 3.35%, Mn: 0.49%, Al: 0.62%, P: ≤0.01%, S: 0.0009%, Sn: 0.12%.

4. A method for manufacturing high-strength non-oriented electrical steel for a new energy vehicle drive rotor according to any one of claims 1 to 3, characterized in that: include: S1. Smelting; S2, continuous casting; S3, hot rolling; S4, normalization, pickling; S5, cold rolling, two-stage annealing; S6. Apply coating.

5. The manufacturing method according to claim 4, characterized in that: Step S5 includes: S51, cold rolling the rolling target to 60-80% of the target thickness; S52, performing a first annealing, wherein the first annealing temperature is 860-1040° C.; S53, cold rolling the rolling target to a target thickness, and performing a second annealing, wherein the second annealing temperature is 860-1040°C.

6. The manufacturing method according to claim 5, characterized in that: In step S52, the first annealing adopts a two-stage heating method: heating from 0 to 500°C at a heating rate of 10°C / s, and heating from 500 to 1040°C at a heating rate of 40°C / s. After heating to the first annealing temperature, it is kept warm for 5 to 20 seconds.

7. The manufacturing method according to claim 5, characterized in that: In step S53, the temperature is raised to the second annealing temperature at a heating rate of 40°C / s.

8. The manufacturing method according to claim 4, characterized in that: In step S5, the rolling object is annealed by a protective gas, and the protective gas includes 60% nitrogen and 40% hydrogen.

9. The manufacturing method according to claim 4, characterized in that: In step S3, the hot rolling start temperature is 1100-1200°C, the final rolling temperature is 870-890°C, and the coiling temperature is 620-680°C.

10. The manufacturing method according to claim 4, characterized in that: In step S4, the normalizing temperature is 920-980°C.

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