High magnetic property oriented silicon steel and method for improving magnetic property by critical deformation

Abstract

The application provides high-magnetic-property oriented silicon steel and a method for improving the magnetic property of critical deformation, and belongs to the field of electrical steel. The preparation process comprises: solid solution treatment, hot rolling; normalizing; twice cold rolling; intermediate annealing; once recrystallization annealing, twice recrystallization annealing; critical deformation to the thickness of a finished product, and critical deformation annealing. Based on the fact that the oriented silicon steel forms deformation texture after preferred orientation, the critical deformation is used to further regulate the deformation texture, so that the strong Goss texture is finally obtained, and the magnetic property of the oriented silicon steel is improved.

Description

Technical Field

[0001] This invention belongs to the field of electrical steel, specifically relating to high magnetic performance oriented silicon steel and a method for improving magnetic performance through critical deformation. Background Technology

[0002] Grain-oriented silicon steel strip is an important raw material in transformer cores. It possesses advantages such as high magnetic properties and low iron loss. In recent years, with the development of electrical and new energy technologies, higher requirements have been placed on the magnetic properties of grain-oriented silicon steel, such as magnetic flux density and iron loss.

[0003] Currently, Goss grains ({110}) are typically used. <001> Abnormal growth can be used to improve the magnetic properties of grain-oriented silicon steel. However, this method often results in an orientation deviation from the accurate Goss orientation, and islands may appear within the Goss grains. This can negatively impact magnetic flux density and iron loss, making it difficult to obtain grain-oriented silicon steel with good magnetic properties.

[0004] In recent years, the following two methods have been used to prepare grain-oriented silicon steel with good magnetic properties using critical deformation:

[0005] Patent CN104726667 proposes a method for producing low-temperature oriented silicon steel using continuous casting and rolling of medium-thin slabs. The secondary cold rolling employs a single-pass critical deformation rolling with a reduction rate of 4%–6%, rolling to a finished thickness of 0.25–0.30 mm. This final rolling with minimal deformation ensures the finished product's geometric dimensions and shape, improving surface quality, dimensional accuracy, and magnetic properties. However, because the secondary cold rolling is a single-pass process with a relatively small reduction rate, the final product thickness is often unstable, leading to a lower yield.

[0006] Patent CN101748259A discloses a process for low-temperature heating of grain-oriented silicon steel. After decarburization annealing, a critical deformation cold rolling process of 1.5%–3% is added to break down the oxide film remaining after decarburization annealing, which facilitates better nitriding. After nitriding, an Al2O3 release agent is applied to improve the surface quality and magnetic properties of the grain-oriented silicon steel. However, this technology has limited nitriding capacity and the amount of nitriding is difficult to control and measure; fluctuations in nitriding can actually reduce magnetic properties. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides high magnetic performance oriented silicon steel and a method for improving magnetic performance through critical deformation.

[0008] By hot rolling and normalizing the grain orientation of the grain-oriented silicon steel billet, followed by cold rolling, intermediate annealing, cold rolling again, recrystallization, and critical deformation, the grain orientation difference of the secondary recrystallized plate is reduced, the grain orientation degree of the secondary recrystallized plate is adjusted, and a certain amount of grain boundary energy is stored to provide driving energy for the subsequent recrystallization process, accelerate the recrystallization speed, shorten the recrystallization time, and improve the magnetic properties of the final product.

[0009] The present invention provides a high magnetic performance oriented silicon steel, wherein the magnetic performance of the oriented silicon steel is reflected in the orientation difference of the Goss grains being concentrated between 3° and 10°.

[0010] The present invention discloses a method for improving the magnetic properties of high-magnetic-performance grain-oriented silicon steel by critical deformation, comprising the following steps:

[0011] 1. This invention uses oriented silicon steel billets as raw materials, heat-treated at 1000-1220℃ for 0.5-1h, hot-rolled with a reduction rate greater than 85%, and cooled to room temperature to produce hot-rolled plates; the thickness of the hot-rolled plates is 2-5mm.

[0012] 2. Normalizing: The hot-rolled plate is held at 900-1150℃ for 0-5 minutes, cooled in the furnace to 700-900℃, held for 0-5 minutes, and then quenched to produce a normalized plate. The holding time at 900-1150℃ and the holding time at 700-900℃ cannot both be 0 at the same time.

[0013] 3. First-stage cold rolling: After pickling, the normalized plate is cold rolled to 0.3-1.5mm with a reduction rate of ≥75% to produce a first-stage cold-rolled plate with a thickness of 0.3-1.5mm.

[0014] 4. Intermediate annealing: Hold the cold-rolled sheet at 700-900℃ for 3-5 minutes to make an intermediate annealed sheet.

[0015] 5. Secondary cold rolling: The intermediate annealed plate is rolled to 0.11-0.71 mm with a reduction rate controlled at 50-75% to produce a secondary cold-rolled plate with a thickness of 0.12-0.71 mm.

[0016] 6. Primary recrystallization: The secondary cold-rolled plate is kept at 700-900℃ for 3-9 minutes to produce a primary recrystallized plate.

[0017] 7. Secondary recrystallization: Under a protective atmosphere, the primary recrystallization plate is heated to 700-900℃ at a heating rate of 10-20℃ / min; the heating rate is reduced to 10-80℃ / h, and the temperature is raised to 1100-1200℃ and held for 3-10h to produce a secondary recrystallization plate; the orientation difference of the Goss grains is concentrated in 7°-15°.

[0018] 8. Critical Deformation: The secondary recrystallized plate is rolled to a thickness of 0.1 to 0.3 mm with a reduction rate of 2 to 10% to produce a critical deformation plate.

[0019] 9. Critical Deformation Annealing: The critical deformation plate is held at 800–900℃ for 5 min–3 h to produce high-magnetic oriented silicon steel. The orientation difference of the Goss grains is concentrated between 3° and 10°.

[0020] The raw material for casting in step 1 can also be replaced with ordinary commercially available grain-oriented silicon steel.

[0021] In step 3, the pickling is performed using hydrochloric acid with a mass concentration of 30-50% to remove the oxide layer until the surface of the oxide layer is grayish-white, thus producing an oxide-free normalized plate.

[0022] In steps 1, 3, and 5, the reduction rate should be ensured first during rolling, and then the target thickness of the slab should be ensured.

[0023] The primary recrystallization plate in step 6 should have smaller and more uniform grains than the intermediate annealing plate in step 4.

[0024] In step 7, the protective gas is nitrogen, the recrystallization fraction of the secondary recrystallization plate is 100%, the grain size should reach the cm level, and the texture is adjusted to Goss texture.

[0025] In step 8, the critical deformation cold-rolled sheet should first be kept within the range of reduction rate, and then its thickness should be guaranteed.

[0026] In step 9, the Goss orientation difference of the grain-oriented silicon steel should be less than the Goss orientation difference of the secondary recrystallization plate in step 7.

[0027] This invention proposes a method for improving the magnetic properties of high-magnetic-performance oriented silicon steel through critical deformation. After two rolling processes and high-temperature recrystallization annealing, the orientation of the texture on the surface of the material is further controlled by critical deformation. By improving the surface quality of the oriented silicon steel, the magnetic properties of the final product are improved, resulting in high-magnetic-performance oriented silicon steel.

[0028] Critical deformation induces slight strain on the material's surface, leading to strain hardening and increased microhardness. Higher critical reduction results in higher hardness. The orientation relationship between grains changes after critical deformation. While secondary recrystallization often introduces some error in Goss orientation accuracy, this is reduced after critical deformation and critical deformation annealing, resulting in more precise Goss orientation. The final product exhibits an increase in abnormally grown grain size while effectively reducing the number of small grains, including islands.

[0029] Critical deformation also has the ability to store grain boundary migration energy. This ability can be used to improve the orientation deviation of Goss grains and eliminate some island grains after abnormal growth of Goss grains, forming a strong Goss texture that is beneficial to magnetic properties.

[0030] Following secondary recrystallization, the Goss grains grew abnormally, leading to an increase in the magnetic properties of the grain-oriented silicon steel. Other oriented grains, due to their orientation relationships and smaller degree of critical deformation, experienced grain boundary migration during subsequent heating, driven by the difference in distortion energy. During subsequent annealing, the Goss grain size further increased, resulting in further improvements in magnetic properties.

[0031] This invention achieves a strong Goss texture by performing critical deformation after secondary recrystallization, reducing the orientation difference of Goss grains, improving the grain orientation degree of grain-oriented silicon steel products, and simultaneously enhancing magnetic properties. A novel, simple, and high-yield production process for grain-oriented silicon steel is proposed. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the process for preparing the high magnetic property oriented silicon steel of the present invention;

[0033] Figure 2 This is a diagram showing the abnormal grain growth of the high magnetic property oriented silicon steel after secondary recrystallization according to the present invention.

[0034] Figure 3 This is the ODF diagram of the abnormally large grains of high magnetic property oriented silicon steel after secondary recrystallization in this invention;

[0035] Figure 4 This is the ODF diagram of the abnormally large grains of high magnetic property oriented silicon steel after critical deformation annealing in this invention. Detailed Implementation

[0036] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described in detail below with reference to specific embodiments. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of this invention, and these all fall within the protection scope of this invention.

[0037] Example 1

[0038] 1. The grain-oriented silicon steel billet is held at 1150℃ for 30 minutes and then hot-rolled in multiple passes with a reduction rate of more than 85%. It is then cooled to room temperature to produce a hot-rolled plate with a thickness of 3 mm.

[0039] 2. Hold the hot-rolled plate at 1000℃ for 3 minutes, cool it in the furnace to 900℃ and hold it for 3 minutes, then quench it to produce a normalized plate.

[0040] 3. After pickling the normalized plate, cold roll it with a reduction rate of not less than 75% to produce a primary cold-rolled plate with a thickness of 0.75 mm; hold the primary cold-rolled plate at 830℃ for 5 minutes for intermediate annealing to produce an intermediate annealed plate; perform secondary cold rolling with a reduction rate controlled between 50% and 75% to produce a secondary cold-rolled plate with a thickness of 0.3 mm.

[0041] 4. The secondary cold-rolled sheet obtained in step 3 is subjected to a first recrystallization treatment at 700℃ for 5 minutes to obtain a primary recrystallized sheet. The primary recrystallized sheet is then heated to 900℃ at a rate of 10℃ / min under a nitrogen protective atmosphere. The heating rate is then reduced, and the temperature is further increased to 1200℃ at a rate of 20℃ / h, and held for 10 hours to obtain a secondary recrystallized sheet with Goss grain orientation differences concentrated between 7° and 15°. The abnormal grain growth of the obtained secondary recrystallized sheet is as follows: Figure 2 As shown, the ODF diagram of abnormally large grains in the secondary recrystallization plate is as follows. Figure 3 As shown.

[0042] 5. The secondary recrystallized plate obtained in step 4 is subjected to critical deformation treatment, rolled to a critical deformation plate of 0.27 mm with a reduction rate of 10%; critical deformation annealing treatment is then performed at 900℃ for 3 hours to obtain high magnetic property oriented silicon steel with Goss grain orientation difference concentrated between 3° and 10°; the process is as follows. Figure 1 As shown, the ODF diagram of the grains after critical deformation annealing is as follows. Figure 4 As shown, the abnormally grown grains are closer to the Goss orientation.

[0043] Example 2

[0044] 1. The grain-oriented silicon steel billet is held at 1200℃ for 1 hour and then hot-rolled in multiple passes with a reduction rate of more than 85%. It is then cooled to room temperature to produce a hot-rolled plate with a thickness of 2.5 mm.

[0045] 2. Hold the hot-rolled plate at 1000℃ for 3 minutes, cool it in the furnace to 900℃ and hold it for 3 minutes, then quench it to produce a normalized plate.

[0046] 3. After pickling the normalized plate, cold roll it with a reduction rate of not less than 75% to produce a primary cold-rolled plate with a thickness of 0.52 mm; hold the primary cold-rolled plate at 900℃ for 5 min for intermediate annealing to produce an intermediate annealed plate; perform secondary cold rolling with a reduction rate controlled between 50% and 75% to produce a secondary cold-rolled plate with a thickness of 0.11 mm.

[0047] 4. The secondary cold-rolled sheet obtained in step 3 is subjected to a recrystallization treatment at 700℃ for 5 minutes to obtain a primary recrystallized sheet. The primary recrystallized sheet is then heated to 700℃ at a heating rate of 10℃ / min under a nitrogen protective atmosphere; the heating rate is then reduced to 1100℃ at a heating rate of 10℃ / h, and held for 3 hours to produce a secondary recrystallized sheet with the orientation difference of Goss grains concentrated between 7° and 15°.

[0048] 5. The secondary recrystallization plate obtained in step 4 is subjected to critical deformation treatment and rolled into a critical deformation plate of 0.1 mm with a reduction rate of 10%. The plate is then subjected to critical deformation annealing treatment at 850℃ for 5 min to obtain high magnetic oriented silicon steel with Goss grain orientation difference concentrated in 3° to 10°.

[0049] Example 3

[0050] 1. The grain-oriented silicon steel billet is held at 1100℃ for 30 minutes and then hot-rolled in multiple passes with a reduction rate of more than 85%. It is then cooled to room temperature to produce a hot-rolled plate with a thickness of 4 mm.

[0051] 2. Hold the hot-rolled plate at 900℃ for 2 minutes, cool it in the furnace to 800℃ and hold it for 3 minutes, then quench it to produce a normalized plate.

[0052] 3. After pickling the normalized plate, cold roll it with a reduction rate of not less than 75% to produce a primary cold-rolled plate with a thickness of 1mm; hold the primary cold-rolled plate at 700℃ for 5 minutes for intermediate annealing to produce an intermediate annealed plate; perform secondary cold rolling with a reduction rate controlled between 50% and 75% to produce a secondary cold-rolled plate with a thickness of 0.32mm.

[0053] 4. The secondary cold-rolled sheet obtained in step 3 is subjected to a recrystallization treatment at 700℃ for 5 minutes to obtain a primary recrystallized sheet. The primary recrystallized sheet is then heated to 900℃ at a heating rate of 10℃ / min under a nitrogen protective atmosphere; the heating rate is then reduced to 20℃ / h, and the temperature is increased to 1200℃, and held for 10 hours to obtain a secondary recrystallized sheet with the orientation difference of Goss grains concentrated between 7° and 15°.

[0054] 5. The secondary recrystallization plate obtained in step 4 is subjected to critical deformation treatment and rolled into a critical deformation plate of 0.3 mm with a reduction rate of 6%. The plate is then subjected to critical deformation annealing treatment at 800℃ for 2 hours to obtain high magnetic oriented silicon steel with an orientation difference of 3° to 10° of Goss grains.

[0055] Example 4

[0056] 1. Hold the grain-oriented silicon steel billet at 1000℃ for 30 minutes, then hot roll it through multiple passes with a reduction rate of more than 85%; cool it to room temperature to produce a hot-rolled plate with a thickness of 5mm.

[0057] 2. Hold the hot-rolled plate at 900℃ for 2 minutes, cool it in the furnace to 800℃ and hold it for 3 minutes, then quench it to produce a normalized plate.

[0058] 3. After pickling the normalized plate, cold roll it with a reduction rate of not less than 75% to produce a primary cold-rolled plate with a thickness of 1.25 mm; hold the primary cold-rolled plate at 830℃ for 5 minutes for intermediate annealing to produce an intermediate annealed plate; perform secondary cold rolling with a reduction rate controlled between 50% and 75% to produce a secondary cold-rolled plate with a thickness of 0.32 mm.

[0059] 4. The secondary cold-rolled sheet obtained in step 3 is subjected to a recrystallization treatment at 700℃ for 5 minutes to obtain a primary recrystallized sheet. The primary recrystallized sheet is then heated to 900℃ at a heating rate of 10℃ / min under a nitrogen protective atmosphere; the heating rate is then reduced to 20℃ / h, and the temperature is increased to 1200℃, and held for 10 hours to obtain a secondary recrystallized sheet with the orientation difference of Goss grains concentrated between 7° and 15°.

[0060] 5. The secondary recrystallization plate obtained in step 4 is subjected to critical deformation treatment and rolled to a critical deformation plate of 0.3 mm with a reduction rate of 6%. The plate is then subjected to critical deformation annealing treatment at 900℃ for 2 hours to obtain high magnetic oriented silicon steel with an orientation difference of 3° to 10° of Goss grains.

[0061] Example 5

[0062] 1. The grain-oriented silicon steel billet is held at 1050℃ for 1 hour and then hot-rolled in multiple passes with a reduction rate of more than 85%. It is then cooled to room temperature to produce a hot-rolled plate with a thickness of 3.5 mm.

[0063] 2. Hold the hot-rolled plate at 1000℃ for 2 minutes, cool it in the furnace to 900℃, hold it for 3 minutes, and then quench it to produce a normalized plate.

[0064] 3. After pickling the normalized plate, cold roll it with a reduction rate of not less than 75% to produce a primary cold-rolled plate with a thickness of 0.8 mm; hold the primary cold-rolled plate at 830℃ for 5 min for intermediate annealing to produce an intermediate annealed plate; perform secondary cold rolling with a reduction rate controlled between 50% and 75% to produce a secondary cold-rolled plate with a thickness of 0.21 mm.

[0065] 4. The secondary cold-rolled sheet obtained in step 3 is subjected to a recrystallization treatment at 700℃ for 5 minutes to obtain a primary recrystallized sheet. The primary recrystallized sheet is then heated to 900℃ at a heating rate of 10℃ / min under a nitrogen protective atmosphere; the heating rate is then reduced to 15℃ / h, and the temperature is increased to 1200℃, and held for 10 hours to obtain a secondary recrystallized sheet with the orientation difference of Goss grains concentrated between 7° and 15°.

[0066] 5. The secondary recrystallization plate obtained in step 4 is subjected to critical deformation treatment and rolled into a critical deformation plate of 0.2 mm with a reduction rate of 5%. The plate is then subjected to critical deformation annealing treatment at 900℃ for 2 hours to obtain high magnetic performance oriented silicon steel with Goss grain orientation difference concentrated in 3° to 10°.

[0067] Example 6

[0068] 1. The grain-oriented silicon steel billet is held at 1000℃ for 30 minutes and then hot-rolled in multiple passes with a reduction rate of more than 85%. It is then cooled to room temperature to produce a hot-rolled plate with a thickness of 2mm.

[0069] 2. Hold the hot-rolled plate at 1100℃ for 2 minutes, cool it in the furnace to 900℃, hold it for 3 minutes, and then quench it to produce a normalized plate.

[0070] 3. After pickling the normalized plate, cold roll it with a reduction rate of not less than 75% to produce a primary cold-rolled plate with a thickness of 0.4 mm; hold the primary cold-rolled plate at 830℃ for 5 min for intermediate annealing to produce an intermediate annealed plate; perform secondary cold rolling with a reduction rate controlled between 50% and 75% to produce a secondary cold-rolled plate with a thickness of 0.11 mm.

[0071] 4. The secondary cold-rolled sheet obtained in step 3 is subjected to recrystallization at 700℃ for 5 minutes to obtain a primary recrystallized sheet. The primary recrystallized sheet is then heated to 900℃ at a heating rate of 10℃ / min under a nitrogen protective atmosphere; the heating rate is then reduced to 20℃ / h, and the temperature is increased to 1200℃, and held for 10 hours to obtain a secondary recrystallized sheet with the orientation difference of Goss grains concentrated between 7° and 15°.

[0072] 5. The secondary recrystallization plate obtained in step 4 is subjected to critical deformation treatment and rolled to a critical deformation plate of 0.1 mm with a reduction rate of 9%. The plate is then subjected to critical deformation annealing treatment at 800℃ for 2 hours to obtain high magnetic oriented silicon steel with an orientation difference of Goss grains concentrated between 3° and 10°.

Claims

1. A method for improving the magnetic properties of high-magnetic-performance grain-oriented silicon steel through critical deformation, characterized in that, Includes the following steps: (1) Using oriented silicon steel billets as raw materials, heat treatment is carried out at 1000~1220℃ for 0.5~1h, hot rolling is carried out with a reduction rate of more than 85%; cooled to room temperature, hot-rolled plates are made; the thickness of hot-rolled plates is 2~5mm; (2) Normalizing: The hot-rolled plate is held at 900-1150℃ for 0-5 minutes, cooled in the furnace to 700-900℃, held for 0-5 minutes and then quenched to make a normalized plate. The holding time at 900-1150℃ and the holding time at 700-900℃ cannot be 0 at the same time. (3) Cold rolling: After pickling, the normalized plate is cold rolled to 0.3-1.5mm with a reduction rate of ≥75% to produce a cold-rolled plate with a thickness of 0.3-1.5mm. (4) Intermediate annealing: The cold-rolled plate is kept at 700-900℃ for 3-5 minutes to make an intermediate annealed plate; (5) Secondary cold rolling: The intermediate annealed plate is rolled to 0.11-0.71 mm with a reduction rate of 50-75% to produce a secondary cold-rolled plate with a thickness of 0.12-0.71 mm; (6) Primary recrystallization: The secondary cold-rolled plate is kept at 700-900℃ for 3-9 minutes to produce a primary recrystallized plate; (7) Secondary recrystallization: Under a protective atmosphere, the primary recrystallization plate is heated to 700-900℃ at a heating rate of 10-20℃ / min; the heating rate is reduced to 10-80℃ / h, and the temperature is raised to 1100-1200℃ and held for 3-10h to produce a secondary recrystallization plate; the orientation difference of the Goss grains is concentrated in 7°-15°. (8) Critical deformation: The secondary recrystallized plate is rolled to 0.1-0.3 mm with a reduction rate in the range of 2-10% to produce a critical deformation plate; (9) Critical deformation annealing: Hold the critical deformation plate at 800-900℃ for 5 min to 3 h to produce oriented silicon steel with good magnetic properties; the orientation difference of Goss grains is concentrated in 3° to 10°.

2. The method for improving the magnetic properties of high-magnetic-performance grain-oriented silicon steel by critical deformation according to claim 1, characterized in that, In step (3), the pickling is carried out by using hydrochloric acid with a mass concentration of 30-50% to remove the oxide layer until the surface of the oxide layer is grayish-white, thus producing an oxide-free normalized plate.

3. The method for improving the magnetic properties of high-magnetic-performance grain-oriented silicon steel by critical deformation according to claim 1, characterized in that, In steps (1), (3) and (5), the reduction rate should be ensured first during rolling, and then the target thickness of the slab should be ensured.

4. The method for improving the magnetic properties of high-magnetic-performance grain-oriented silicon steel by critical deformation according to claim 1, characterized in that, In step (6), the grains of the primary recrystallization plate are guaranteed to be finer and more uniform than those of the intermediate annealing plate in step 4.

5. The method for improving the magnetic properties of high-magnetic-performance grain-oriented silicon steel by critical deformation according to claim 1, characterized in that, In step (7), the protective gas is nitrogen, the recrystallization fraction of the secondary recrystallization plate is 100%, the grain size should reach the cm level, and the texture is adjusted to Goss texture.

6. The method for improving the magnetic properties of high-magnetic-performance oriented silicon steel by critical deformation according to claim 1, characterized in that, In step (8), the critical deformation cold-rolled plate is first ensured to be within the range of reduction rate, and then its thickness is ensured.

7. The method for improving the magnetic properties of high-magnetic-performance grain-oriented silicon steel by critical deformation according to claim 1, characterized in that, In step (9), the Goss orientation difference of the oriented silicon steel is less than the Goss orientation difference of the secondary recrystallization plate in step (7).

8. A high-magnetic-performance grain-oriented silicon steel, characterized in that, The high-magnetic-performance oriented silicon steel is prepared by the critical deformation enhancement method according to any one of claims 1-7, wherein the orientation difference of the Goss grains in the high-magnetic-performance oriented silicon steel is concentrated in the range of 3° to 10°.

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