A low iron loss non-oriented electrical steel and preparation method thereof

Abstract

The invention discloses a low iron loss non-oriented electrical steel and a preparation method thereof. The preparation method comprises the following steps: casting the raw material into an ingot, forging into a forging billet, hot rolling at a temperature of 900-1050°C, the deformation amount per pass is 22-24%, the total rolling pass is 4 times, and a hot-rolled plate with a thickness of 1.5-2.0 mm is obtained, normalizing at 900-1000°C for 10-30 min, cold rolling after pickling, annealing at 900-1000°C for 3-10 min, and electrical steel is obtained. The present invention is directed to a high-grade non-oriented electrical steel with high Si content and Mn and Cr alloying. Under the premise of avoiding complex processes, the process parameters are optimized, the organization after the plate is rolled is regulated, and the average grain size of the obtained electrical steel is 100-250 μm, achieving a balance between magnetic properties and mechanical properties, and obtaining a non-oriented electrical steel with both low iron loss and high strength.

Description

Technical Field

[0001] The invention relates to the technical field of electrical steel manufacturing, and in particular to a low iron loss non-oriented electrical steel and a preparation method thereof. Background Art

[0002] In recent years, with the depletion of oil resources and the increasing severity of environmental pollution, new energy vehicles have been vigorously developed due to their advantages of low energy consumption and less pollution. Non-oriented electrical steel is an important core material in drive motors. The rapid development of new energy vehicles has put forward higher and higher requirements on the performance of non-oriented electrical steel. The rotor core of the drive motor generates increased centrifugal force during its high-speed operation. As an important component, non-oriented electrical steel must not only have excellent soft magnetic properties, but also high strength. Excellent soft magnetic properties, such as low iron loss and high magnetic induction, are of great significance for avoiding ineffective energy loss during the operation of the motor. High strength can greatly improve its service life and safety. In this case, how to prepare non-oriented electrical steel that takes into account both its magnetic properties and high strength has become a hot topic in the research field of electrical steel for new energy vehicle motors.

[0003] Patent CN112375965A discloses a method for preparing Cu-containing high-strength, low-iron-loss non-oriented high-silicon steel. The method mainly increases the Si content and adds Cu elements therein, so that the Cu elements disperse and precipitate after recrystallization annealing to improve the strength of the non-oriented electrical steel. The prepared high-strength non-oriented electrical steel has a yield strength of 550-1050MPa and an iron loss of 0.01% when the plate thickness is 0.3mm. 10 / 400 =20.3W / kg. This method requires a final aging treatment in order to control the size of the nano-copper precipitate. The process is complex and time-consuming, resulting in increased costs. Patent CN113981329A discloses a low iron loss, high-strength non-oriented electrical steel for new energy vehicle drive motors and a method for manufacturing the same. This method purifies molten steel by adding Ce and Sn, and improves the strength and magnetic properties of the non-oriented electrical steel by microalloying, and finally prepares a finished plate with a thickness of 0.35mm. 50 =1.67-1.74T,W 10 / 400 =16.5-21.5W / kg, yield strength is 660-745MPa. Although the strength of this electrical steel is high, the iron loss is still high. Patent CN107746941A discloses a high-strength cold-rolled non-oriented silicon steel for drive motors and a manufacturing method. This method successfully prepares B by adding an appropriate amount of niobium and chromium to the non-oriented silicon steel, and introducing a secondary cold rolling process while adopting hot rolling and curling processes. 50 1.67-1.70T, iron loss P 10 / 400The non-oriented electrical steel has a yield strength of 18.8-32.12W / kg and a yield strength of 460-510MPa. Although this method improves the strength, it causes an increase in iron loss, and the introduction of secondary cold rolling adds an intermediate annealing, which increases the number of processes and the economic cost.

[0004] Therefore, it is of great significance to provide a non-oriented electrical steel with low iron loss and high strength and a preparation process thereof. Summary of the invention

[0005] The primary purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a method for preparing low iron loss non-oriented electrical steel.

[0006] Another object of the present invention is to provide low iron loss non-oriented electrical steel prepared by the above preparation method.

[0007] The object of the present invention is achieved by the following technical solution: A method for preparing low iron loss non-oriented electrical steel comprises the following steps:

[0008] 1. Smelting: fully mix the raw materials and cast them into ingots; the chemical composition of the ingots is as follows: Si: 3.0-4.0%, Mn: 0.5-1.0%, Cr: 0.5-1.0%, S≤0.0030%, P≤0.0090%, C≤0.0090%, and the rest is iron and unavoidable impurities;

[0009] 2. Forging: forging the ingot in step 1 into a forging blank with a thickness of 20-30 mm at 900-1200° C.;

[0010] 3. Hot rolling: hot rolling the forged billet in step 2 at a temperature of 900-1050° C., with a deformation amount of 22-24% per pass and a total rolling pass of 4 times, to obtain a hot-rolled plate with a thickness of 1.5-2.0 mm;

[0011] 4. Normalization treatment: keep the hot-rolled plate in step 3 at 900-1000°C for 10-30 minutes;

[0012] 5. Cold rolling: After the hot-rolled plate normalized in step 4 is pickled, it is repeatedly cold-rolled for multiple passes, and the total deformation is controlled between 66-86%, so as to obtain a cold-rolled plate with a thickness of 0.27-0.5 mm;

[0013] 6. Annealing: anneal the cold-rolled sheet in step 5 at 900-1000° C. for 3-10 min to obtain low iron loss non-oriented electrical steel.

[0014] Preferably, the temperature of casting into ingots in step 1 is 1450-1550°C.

[0015] Preferably, the forging in step 2 is performed by free forging.

[0016] Preferably, the thickness of the forging blank in step 2 is 20 mm.

[0017] Preferably, during the hot rolling process in step 3, the forging billet is kept in a heating furnace at 900-1050° C. for 10-30 min, then hot rolled twice, returned to the furnace for keeping warm for 5-10 min, and then hot rolled twice more.

[0018] Preferably, the pickling in step 5 is performed using a hydrochloric acid solution.

[0019] Preferably, the cold rolling temperature in step 5 is room temperature.

[0020] Preferably, the annealing treatment in step 6 is carried out under Ar 2 Carry out under protective atmosphere.

[0021] A low iron loss non-oriented electrical steel is prepared by the above preparation method.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention aims at high-grade non-oriented electrical steel with high Si content and Mn and Cr alloying. Under the premise of avoiding complicated processes, the process parameters such as hot rolling, normalizing, cold rolling, annealing and the like are optimized to control the microstructure of the plate after rolling. The average grain size of the electrical steel after the final annealing treatment is 100-250 μm, and the balance of magnetic properties and mechanical properties is achieved, thereby obtaining non-oriented electrical steel with low iron loss and high strength. The iron loss P of the finished non-oriented electrical steel of the present invention is 15 / 50 ≤2.3W / kg, P 10 / 400 ≤15.8W / kg, magnetic induction intensity B 50 ≥1.64T, yield strength σ s ≥450MPa, elongation δ≥10%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a grain morphology diagram of the hot-rolled plate after normalizing treatment in Example 1. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Example 1

[0027] (1) Smelting: the raw materials are fully mixed according to a certain composition ratio, heated to 1500°C in a vacuum induction furnace for refining, and cast into an ingot; the chemical composition of the ingot is Si: 4.0%, Mn: 0.5%, Cr: 1.0%, S: 0.0030%, P: 0.009%, C: 0.009%, and the rest is iron and unavoidable impurities;

[0028] (2) Forging: Forging is performed by air free forging in the processing range of 1000-1100°C, and the ingot is forged into a forging blank with a thickness of 20 mm by repeated upsetting and drawing.

[0029] (3) Hot rolling: The forged billet is kept in a heating furnace at 1050°C for two passes of hot rolling, then returned to the furnace for 10 min of keeping, and then hot rolled again for two passes. The deformation amount of each pass is 23%, and the thickness of the hot rolled plate finally obtained is 1.5 mm.

[0030] (4) Normalizing treatment: The hot-rolled sheet obtained in (3) is normalized in a heating furnace at 1000°C for 20 min to form a completely recrystallized structure ( Figure 1 );

[0031] (5) Pickling: pickling with 10% hydrochloric acid solution;

[0032] (6) Cold rolling: After multiple cold rolling passes at room temperature, the total deformation is controlled to be 76.6%, and a cold-rolled sheet with a thickness of 0.35 mm is obtained;

[0033] (7) Annealing treatment: cold rolled sheet is annealed in Ar 2 Annealing at 900℃ for 10min under atmosphere protection conditions eliminates residual stress and completes the recrystallization process to obtain an electrical steel finished plate with an average grain size of 103μm. 15 / 50 =2.2.280W / kg, P 10 / 400 =15.650W / kg, B 50 =1.643T, yield strength σ s =455MPa, elongation δ=12.0%.

[0034] Example 2

[0035] (1) Smelting: The raw materials are fully mixed according to a certain composition ratio, heated to 1450°C in a vacuum induction furnace for refining, and cast into an ingot; the chemical composition and mass percentage of the ingot are Si: 4.0%, Mn: 0.5%, Cr: 0.5%, S: 0.0030%, P: 0.009%, C: 0.009%, and the rest are iron and unavoidable impurities;

[0036] (2) Forging: Forging is performed by air free forging in the processing range of 900-1000°C, and the ingot is forged into a forging blank with a thickness of 20 mm by repeated upsetting and stretching;

[0037] (3) Hot rolling: the forged billet is kept in a heating furnace at 1050°C for 20 minutes, then hot rolled twice, then returned to the furnace for 10 minutes, and then hot rolled twice again. The deformation amount of each pass is 23%, and the thickness of the hot rolled sheet is 1.5 mm.

[0038] (4) Normalizing treatment: The hot-rolled sheet obtained in (3) is normalized in a heating furnace at 900° C. for 30 min to form a completely recrystallized structure;

[0039] (5) Pickling: Use 10% dilute hydrochloric acid solution for pickling;

[0040] (6) Cold rolling: At room temperature, the cold rolled sheet is subjected to multiple cold rolling passes with a total deformation of 76.6% to obtain a cold rolled sheet with a thickness of 0.35 mm.

[0041] (7) Annealing treatment: cold rolled sheet is annealed in Ar 2 Annealing at 900℃ for 10min under atmosphere protection conditions eliminates residual stress and completes the recrystallization process to obtain an electrical steel finished plate with an average grain size of 112μm. 15 / 50 =2.194W / kg, P 10 / 400 =13.399W / kg, B 50 =1.657T, yield strength σ s =475MPa, elongation δ=12.5%.

[0042] Example 3

[0043] (1) Smelting: The raw materials are fully mixed according to a certain composition ratio, heated to 1450°C in a vacuum induction furnace for refining, and cast into an ingot; the chemical composition and mass percentage of the ingot are Si: 4.0%, Mn: 1.0%, Cr: 0.5%, S: 0.0030%, P: 0.009%, C: 0.009%, and the rest are iron and unavoidable impurities;

[0044] (2) Forging: Forging is performed by air free forging in the processing range of 1100-1200°C, and the ingot is forged into a forging blank with a thickness of 20 mm by repeated upsetting and drawing.

[0045] (3) Hot rolling: the forged billet is kept at 1000°C for 30 min in a heating furnace, and then hot rolled twice. Then, it is returned to the furnace and kept for 5 min, and then hot rolled twice again. The deformation amount of each pass is 23%. The thickness of the hot rolled plate finally obtained is 1.5 mm.

[0046] (4) Normalizing treatment: The hot-rolled sheet obtained in (3) is normalized in a heating furnace at 1000° C. for 20 min to form a completely recrystallized structure;

[0047] (5) Pickling: Use 10% dilute hydrochloric acid solution for pickling, temperature;

[0048] (6) Cold rolling: At room temperature, the cold rolling is repeated for multiple passes, and the total deformation is controlled to be 80%, and a cold-rolled sheet with a thickness of 0.3 mm is obtained;

[0049] (7) Annealing treatment: cold rolled sheet is annealed in Ar 2 Annealing at 900℃ for 10min under atmosphere protection conditions eliminates residual stress and completes the recrystallization process to obtain an electrical steel finished plate with an average grain size of 120μm. 15 / 50 =2.224W / kg, P 10 / 400 =14.898W / kg, B 50 =1.658T, yield strength σ s =490MPa, elongation δ=15.0%.

[0050] Comparative Example 1

[0051] (1) Smelting: the raw materials are fully mixed according to a certain composition ratio, heated to 1500°C in a vacuum induction furnace for refining, and cast into an ingot; the chemical composition of the ingot is Si: 4.0%, Mn: 0.5%, Cr: 1.0%, S: 0.0030%, P: 0.009%, C: 0.009%, and the rest is iron and unavoidable impurities;

[0052] (2) Forging: Forging is performed by air free forging in the processing range of 1000-1100°C, and the ingot is forged into a forging blank with a thickness of 20 mm by repeated upsetting and drawing.

[0053] (3) Hot rolling: The forged billet is kept at 1100°C in a heating furnace and then hot rolled twice. Then, it is returned to the furnace and kept at this temperature for 10 min, and then hot rolled twice again. The deformation amount of each pass is 23%. The thickness of the hot rolled plate is 1.5 mm.

[0054] (4) Normalizing treatment: The hot-rolled sheet obtained in (3) is normalized in a heating furnace at 1000° C. for 20 min to form a completely recrystallized structure;

[0055] (5) Pickling: Use 10% dilute hydrochloric acid solution for pickling;

[0056] (6) Cold rolling: After multiple cold rolling passes at room temperature, the total deformation is controlled to be 76.6%, and a cold-rolled sheet with a thickness of 0.35 mm is obtained;

[0057] (7) Annealing treatment: cold rolled sheet is annealed in Ar 2 Annealing at 800℃ for 10min under atmosphere protection conditions eliminates residual stress and completes the recrystallization process to obtain an electrical steel finished plate with an average grain size of 89μm. 15 / 50 =3.890W / kg, P 10 / 400 =19.841W / kg, B 50 =1.621T, yield strength σ s =510MPa, elongation δ=11%.

[0058] Comparative Example 2

[0059] (1) Smelting: the raw materials are fully mixed according to a certain composition ratio, heated to 1500°C in a vacuum induction furnace for refining, and cast into an ingot; the chemical composition of the ingot is Si: 4.0%, Mn: 0.5%, Cr: 1.0%, S: 0.0030%, P: 0.009%, C: 0.009%, and the rest is iron and unavoidable impurities;

[0060] (2) Forging: Forging is performed by air free forging in the processing range of 1000-1100°C, and the ingot is forged into a forging blank with a thickness of 20 mm by repeated upsetting and drawing.

[0061] (3) Hot rolling: The forged billet is kept in a heating furnace at 1050°C for two passes of hot rolling, then returned to the furnace for 10 min of keeping, and then hot rolled again for two passes. The deformation amount of each pass is 23%, and the thickness of the hot rolled plate finally obtained is 1.5 mm.

[0062] (4) Normalizing treatment: The hot-rolled sheet obtained in (3) is normalized in a heating furnace at 800° C. for 20 min to form a completely recrystallized structure;

[0063] (5) Pickling: Use 10% dilute hydrochloric acid solution for pickling;

[0064] (6) Cold rolling: After multiple cold rolling passes at room temperature, the total deformation is controlled to be 76.6%, and a cold-rolled sheet with a thickness of 0.35 mm is obtained;

[0065] (7) Annealing treatment: cold rolled sheet is annealed in Ar 2 Annealing at 900℃ for 10min under atmosphere protection conditions eliminates residual stress and completes the recrystallization process to obtain an electrical steel finished plate with an average grain size of 95μm. 15 / 50 =3.532W / kg, P 10 / 400 =18.932W / kg, B 50 =1.586T, yield strength σ s=492MPa, elongation δ=10.5%. Comparative Example 3

[0066] (1) Smelting: The raw materials are fully mixed according to a certain composition ratio, heated to 1500°C in a vacuum induction furnace for refining, and cast into an ingot; the chemical composition of the ingot is Si: 4.0%, Cr: 1.5%, S: 0.0030%, P: 0.009%, C: 0.009%, and the rest is iron and unavoidable impurities;

[0067] (2) Forging: Forging is performed by air free forging in the processing range of 1000-1100°C, and the ingot is forged into a forging blank with a thickness of 20 mm by repeated upsetting and drawing.

[0068] (3) Hot rolling: The forged billet is kept in a heating furnace at 1050°C for two passes of hot rolling, then returned to the furnace for 10 min of keeping, and then hot rolled again for two passes. The deformation amount of each pass is 23%, and the thickness of the hot rolled plate finally obtained is 1.5 mm.

[0069] (4) Normalizing treatment: The hot-rolled sheet obtained in (3) is normalized in a heating furnace at 1000° C. for 20 min to form a completely recrystallized structure;

[0070] (5) Pickling: Use 10% dilute hydrochloric acid solution for pickling;

[0071] (6) Cold rolling: After multiple cold rolling passes at room temperature, the total deformation is controlled to be 76.6%, and a cold-rolled sheet with a thickness of 0.35 mm is obtained;

[0072] (7) Annealing treatment: cold rolled sheet is annealed in Ar 2 Annealing at 900℃ for 10min under atmosphere protection conditions eliminates residual stress and completes the recrystallization process to obtain an electrical steel finished plate with an average grain size of 82μm. 15 / 50 =3.644W / kg, P 10 / 400 =9.095W / kg, B 50 =1.618T, yield strength σ s =502MPa, elongation δ=12.3%.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing low iron loss non-oriented electrical steel, characterized in that: The following steps are involved: 1) Smelting: the raw materials are fully mixed and cast into ingots; the chemical composition of the ingot is as follows: Si: 3.0-4.0%, Mn: 0.5-1.0%, Cr: 0.5-1.0%, S≤0.0030%, P≤0.0090%, C≤0.0090%, and the rest is iron and unavoidable impurities; 2) Forging: forging the ingot in step 1 into a forging blank with a thickness of 20-30 mm at 900-1200° C.; 3) Hot rolling: hot rolling the forged billet in step 2 at a temperature of 900-1050° C., with a deformation amount of 22-24% per pass and a total rolling pass of 4 times, to obtain a hot-rolled plate with a thickness of 1.5-2.0 mm; 4) Normalization treatment: keeping the hot-rolled plate in step 3 at 900-1000° C. for 10-30 min; 5) Cold rolling: After the hot-rolled plate normalized in step 4 is pickled, it is repeatedly cold-rolled for multiple passes, and the total deformation is controlled between 66-86%, so as to obtain a cold-rolled plate with a thickness of 0.27-0.5 mm; 6) Annealing: annealing the cold-rolled sheet in step 5 at 900-1000° C. for 3-10 min to obtain low iron loss non-oriented electrical steel; The low iron loss non-oriented electrical steel has an average grain size of 100-250 μm.

2. The method for preparing low iron loss non-oriented electrical steel according to claim 1, characterized in that: The temperature of casting into ingots in step 1 is 1450-1550°C.

3. The method for preparing low iron loss non-oriented electrical steel according to claim 1, characterized in that: The forging in step 2 is performed by free forging.

4. The method for preparing low iron loss non-oriented electrical steel according to claim 1, characterized in that: The thickness of the forging blank in step 2 is 20 mm.

5. The method for preparing low iron loss non-oriented electrical steel according to claim 1, characterized in that: During the hot rolling process in step 3, the forging billet is kept in a heating furnace at 900-1050° C. for 10-30 minutes, then hot rolled twice, returned to the furnace for keeping warm for 5-10 minutes, and then hot rolled twice more.

6. The method for preparing low iron loss non-oriented electrical steel according to claim 1, characterized in that: The pickling in step 5 adopts hydrochloric acid solution.

7. The method for preparing low iron loss non-oriented electrical steel according to claim 1, characterized in that: The cold rolling temperature in step 5 is room temperature.

8. The method for preparing low iron loss non-oriented electrical steel according to claim 1, characterized in that: The annealing treatment in step 6 is carried out under Ar2 atmosphere protection conditions.

9. A low iron loss non-oriented electrical steel, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8.

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