Non-oriented silicon steel and method for producing the same

Abstract

The application discloses a non-oriented silicon steel and a production method thereof. The non-oriented silicon steel comprises the following components in percentage by weight: Si: 2.90-3.30%; Mn: 0.65-0.80%; P: 0.0040-0.021%; S: 0.002-0.001%; Al: 0.50-0.80%; Cu: 0.50-0.65%, and the rest is Fe and inevitable impurities. The yield strength of the non-oriented silicon steel is 520-590 MPa, the tensile strength is 640-740 MPa, the elongation A50 is 16-20%, the magnetic polarization strength J 5000 is 1.66-1.71 T, and the iron loss P 1.0 / 400 is 17.6-20.4 W / kg. The non-oriented silicon steel has high strength and high magnetism, and has low cost.

Description

Technical Field

[0001] This invention belongs to the field of non-oriented silicon steel technology, specifically relating to a non-oriented silicon steel and its production method. Background Technology

[0002] In the power, electronics, and military industries, electrical steel is a soft metallic material with relatively excellent magnetic properties and the largest usage volume. It is commonly used to manufacture transformers, motors, generators, and electrical components. In recent years, as the motor industry has continuously developed towards higher efficiency and higher speeds, motor performance and speed indicators have been constantly improving, placing increasingly higher demands on the strength and performance of motor core materials. The properties of electrical steel directly determine the performance indicators of motors, making the development of electrical steel suitable for high-efficiency, high-performance motors particularly important.

[0003] To improve motor efficiency and speed, common methods include adding alloy components and increasing work hardening in electrical steel. For example, Chinese patent CN103060701A discloses a non-oriented high-silicon electrical steel strip and its preparation method, and Chinese patent CN119351891A discloses a non-oriented electrical steel with a strength of not less than 500MPa and its preparation method. Both of these patents disclose electrical steels with added high chromium content.

[0004] Chinese patent CN111057821A discloses a non-oriented electrical steel, its preparation method, and its application. The electrical steel contains high-cost rare metal elements.

[0005] Chinese patent CN120591677A discloses a high-strength non-oriented silicon steel with a yield strength of 930 MPa and its production method. It comprehensively utilizes three strengthening methods—dislocation strengthening, solid solution strengthening, and precipitation strengthening—to increase the yield strength of the non-oriented silicon steel to 930 MPa. However, this strengthening method significantly deteriorates the magnetic properties, resulting in increased iron loss (P0.05). 1.0 / 400 ≥47W / kg, magnetic induction intensity B 5000 ≤1.56T.

[0006] Chinese patent CN111471941A discloses a high-strength non-oriented silicon steel with a yield strength of 600MPa for the rotor of a new energy vehicle drive motor and its manufacturing method. The addition of elements such as Cr, Nb, Ti, and Ni increases the smelting cost, resulting in a relatively poor P10 / 400 of 22.6~30.4 W / kg. This hinders the improvement of motor efficiency.

[0007] With increasing market competition, in order to reduce costs and increase efficiency, it is necessary to develop a low-cost, non-oriented electrical steel silicon steel with a yield strength of ≥500MPa and the ability to meet magnetic performance requirements. Summary of the Invention

[0008] To solve the above-mentioned technical problems, the present invention provides a non-oriented silicon steel and its production method, wherein the yield strength is 520~590MPa, the tensile strength is 640~740MPa, the elongation A50 is 16~20%, and the magnetic polarization J is [not specified]. 5000 The iron loss P is 1.66~1.71T. 1.0 / 400 It has a strength of 17.6~20.4 W / kg, and also possesses high strength and high magnetism, while being low in cost.

[0009] The technical solution adopted in this invention is as follows:

[0010] This invention provides a non-oriented silicon steel with the following chemical composition and weight percentages: C ≤ 0.002%; Si: 2.90~3.30%; Mn: 0.65~0.80%; P: 0.0040~0.021%; S ≤ 0.0025%; Als: 0.50~0.80%; Cu: 0.50~0.65%, with the remainder being Fe and unavoidable impurities, wherein (Mn+Cu) / S = 600~900.

[0011] The non-oriented silicon steel has a yield strength of 520~590MPa, a tensile strength of 640~740MPa, an elongation A50 of 16~20%, and a magnetic polarization J. 5000 The iron loss P is 1.66~1.71T. 1.0 / 400 The content is 17.6~20.4 W / kg; the grain size of the non-oriented silicon steel is 85~105 μm.

[0012] The present invention also provides a method for producing the non-oriented silicon steel, the method comprising the following steps: smelting → continuous casting → heating → hot rolling → normalizing → pickling → cold rolling → annealing → coating with an insulating coating.

[0013] The smelting steps include: converter smelting, argon blowing at the argon blowing station, and RH vacuum degassing refining; wherein, the refining requires vacuum degassing for 20 minutes under a vacuum degree ≤100Pa to ensure that N in the molten steel is ≤0.002%, so as to avoid the generation of a large number of nitrogen compound inclusions in the finished steel and thus deteriorate the magnetic properties.

[0014] In the continuous casting step, the casting speed is controlled at 1.0~1.2m / min, and the superheat of the molten steel is controlled at 15~30℃. The purpose is to control the appropriate surface temperature of the billet, reduce the enrichment of Cu metal or harmful elements at the grain boundaries, and suppress precipitation during subsequent rolling of the billet; the billet is continuously cast into a thickness of 210~230mm.

[0015] In the heating process, the preheating section temperature is 730~760℃; the first heating section temperature is 1112~1143℃, and the holding time is ≥37min; the second heating section temperature is 1130~1150℃, and the holding time is ≥35min; the soaking section temperature is 1090~1110℃, and the holding time is ≥30min; the total time in the furnace is 140~200min.

[0016] In the hot rolling step, the rough rolling is carried out in 4 passes, with the reduction rate of each pass controlled at 35~38%, the rough rolling thickness is 34~40mm, and the final rolling temperature of the rough rolling is ≥960℃. At this temperature, MnS precipitates can aggregate and grow to form coarse precipitates.

[0017] In the hot rolling process, the initial finishing temperature is 920-940℃, and the finishing rolling is carried out in 7 consecutive passes. The reduction rate of the last pass is controlled at 38-40%, and the finishing rolling temperature is 870-930℃. The strip crown is controlled at 30-40μm, and the wedge shape is controlled at 15-25μm; the strip is finished to a thickness of 2.0-2.15mm. When the temperature is between 960-940℃, the fine precipitates in the steel are the most abundant during rolling. Therefore, the initial finishing temperature is controlled at 920-940℃, at which point there are relatively few MnS precipitates. To increase the activation energy for precipitate growth and form coarse MnS precipitates, the 7th pass uses high temperature and high reduction, and the finishing rolling temperature is controlled at 870-930℃. The aim is to reduce fine MnS precipitation. These fine precipitates pin the grain boundaries, reducing the {100} and {110} crystal plane components that are favorable for magnetization and increasing the {111} components that are unfavorable, which is detrimental to the electromagnetic properties of the finished product.

[0018] In the hot rolling step, after finishing rolling, the temperature is cooled to 580~620℃ by water cooling before coiling.

[0019] In the pickling step, hydrochloric acid with a volume percentage concentration of 8-12% is used for pickling, and the pickling temperature is 75-80℃.

[0020] In the normalization step, the normalization temperature is 880~960℃ and the steel strip running speed is 40~60m / min.

[0021] In the cold rolling step, the total cold rolling reduction rate is controlled at 75-90%; the temperature of the cold rolling emulsion is controlled at 60-65℃; and the thickness is cold rolled to 0.2-0.35mm.

[0022] In the annealing step, a mixture of hydrogen and nitrogen is used as the protective gas. To control the precipitates, the annealing temperature is set to T = 0.13 × (Mn + Cu) / S + 900℃, and the time is 180~260s, based on the composition ratio of Mn, Cu, and S. Then, the temperature is reduced to below 560℃ at a cooling rate not exceeding 18℃ / s. Slow cooling is beneficial for the slow growth of silicon steel grains. If the cooling rate exceeds 18℃ / s, it will cause mixed crystals and affect the magnetic properties of the finished product. Finally, the furnace is cooled to room temperature.

[0023] During the annealing step, the annealing tension is controlled at 3~5MPa.

[0024] When calculating the annealing temperature, the values ​​of Mn, Cu, and S are taken as their content in the steel multiplied by 100.

[0025] In the step of applying the insulating coating, the curing temperature of the insulating coating is 440~560℃ and the time is 30~50s.

[0026] The functions and controls of each component in the non-oriented silicon steel provided by this invention are as follows:

[0027] Mn: Mn has a solid solution strengthening effect in steel, but it readily forms fine, dispersed MnS inclusions with S. These fine particles strongly pin grain boundaries, hinder grain growth, and impede the movement of magnetic domain walls, leading to a significant deterioration in magnetic properties. However, coarse MnS inclusions have little impact on electromagnetic properties. This invention controls the chemical composition ratio to achieve (Mn+Cu) / S of 600~900, using hot rolling to generate coarse sulfides, followed by precipitation strengthening through continuous annealing. Furthermore, manganese promotes recrystallization during hot rolling and annealing, strengthening the {100} and {110} crystal planes that are favorable for magnetization, while weakening the unfavorable {111} composition, thereby improving permeability and magnetic polarization. Manganese also improves yield strength and mechanical properties through solid solution strengthening, with the Mn content controlled at 0.65~0.80%.

[0028] Al: Al plays a role in improving resistivity and strength in non-oriented electrical steel, but if the Al content is too high, it will reduce the magnetic polarization intensity. Therefore, the Al content is required to be controlled between 0.50 and 0.80%.

[0029] C: In electrical steel, C is the main element that causes magnetic aging. When the residual C content in the steel is high, it leads to increased coercivity and hysteresis loss, and also causes magnetic aging. It is necessary to control C ≤ 0.002%.

[0030] Si: The main function of Si is to increase resistivity and reduce eddy current loss. When the Si content is too high, it will reduce the magnetic anisotropy constant and saturation magnetostriction constant of Fe, resulting in a decrease in hysteresis loss and magnetic induction. Similarly, when the Si content is increased to more than 3.5%, the plasticity of the strip steel is greatly reduced, making it difficult to achieve industrial production. Therefore, the Si content is required to be controlled between 2.90 and 3.30%.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The non-oriented silicon steel provided by this invention controls the content of Mn, Cu, and S elements, and maintains a reasonable (Mn+Cu) / S ratio. By utilizing a heating process, it suppresses the formation of fine MnS precipitates. A suitable rolling process is employed to strengthen the {100} and {110} crystal planes that are conducive to magnetization, while weakening the unfavorable {111} composition. Furthermore, by controlling the annealing temperature, a reasonable grain size is achieved, ensuring both strength and magnetic properties.

[0033] The non-oriented silicon steel provided by this invention, when the product thickness is 0.20~0.35mm, has a final product yield strength Rp0.2 of 520~590MPa, tensile strength Rm of 640~740MPa, elongation A50 of 16~20%, and magnetic polarization J. 5000 The iron loss P is 1.66~1.71T. 1.0 / 400 The value is 17.6~20.4W / kg; the generator rotor speed manufactured by the product maintains a stable operation of 10000r / min, and the stable operating speed is increased by more than 20%. Attached Figure Description

[0034] Figure 1 This is a grain size diagram of the non-oriented silicon steel in Example 1. Detailed Implementation

[0035] This invention provides a non-oriented silicon steel with the following chemical composition and weight percentages: Si: 2.90~3.30%; Mn: 0.65~0.80%; P: 0.0040~0.021%; S≤0.0025%; Als: 0.50~0.80%; Cu: 0.50~0.65%, with the remainder being Fe and unavoidable impurities, wherein (Mn+Cu) / S=600~900.

[0036] The production method of the non-oriented silicon steel includes the following steps: converter smelting → argon blowing at the argon blowing station → RH vacuum degassing refining → continuous casting → heating → hot rolling → normalizing → pickling → cold rolling → annealing → coating with insulating coating.

[0037] The refining process requires vacuum degassing for 20 minutes under a vacuum degree ≤100Pa to ensure that N in the molten steel is ≤0.002% and S is ≤0.008% after refining.

[0038] In the continuous casting step, the casting speed is controlled at 1.0~1.2m / min, and the superheat of the molten steel is controlled at 15~30℃; the continuous casting produces a billet with a thickness of 210~230mm.

[0039] In the heating process, the preheating section temperature is 730~760℃; the first heating section temperature is 1112~1143℃, and the holding time is ≥37min; the second heating section temperature is 1130~1150℃, and the holding time is ≥35min; the soaking section temperature is 1090~1110℃, and the holding time is ≥30min; the total time in the furnace is 140min~200min.

[0040] In the hot rolling step, the rough rolling is carried out in 4 passes, with the reduction rate of each pass controlled at 35~38%, the rough rolling thickness is 34-40mm, and the temperature after rough rolling is ≥960℃.

[0041] In the hot rolling process, the initial rolling temperature for finishing is 940~920℃, and the finishing rolling is carried out in 7 consecutive passes, with the reduction rate of the last pass controlled at 38~40%. The strip crown is controlled at 30~40μm, and the wedge shape is controlled at 15~25μm; the strip is finished to a thickness of 2.00~2.15mm.

[0042] In the hot rolling step, after finishing rolling, the temperature is cooled to 580~620℃ by water cooling before coiling.

[0043] In the pickling step, hydrochloric acid with a volume percentage concentration of 8-12% is used for pickling, and the pickling temperature is 75-80℃.

[0044] In the normalization step, the normalization temperature is 910~950℃ and the steel strip running speed is 30~50m / min.

[0045] In the cold rolling step, the total cold rolling reduction rate is controlled at 75-90%; and the thickness is cold rolled to 0.2-0.35 mm.

[0046] In the annealing step, a mixture of hydrogen and nitrogen is used as the protective gas, the annealing temperature is T=0.13×(Mn+Cu) / S+900℃, the time is 180~260s, and then the temperature is reduced to below 560℃ at a cooling rate not exceeding 18℃ / s, and finally cooled to room temperature in the furnace.

[0047] In the step of applying the insulating coating, the curing temperature of the insulating coating is 440~560℃ and the time is 30~50s.

[0048] The present invention will now be described in detail with reference to the embodiments.

[0049] The chemical composition and weight percentage of the non-oriented silicon steel in each embodiment and comparative example are shown in Table 1, with the balance being iron and unavoidable impurities.

[0050] Table 1 Chemical Composition

[0051]

[0052] The production methods of non-oriented silicon steel in each embodiment and comparative example include the following steps: converter smelting → argon blowing at the argon blowing station → RH vacuum degassing refining → continuous casting → heating → hot rolling → normalizing → pickling → cold rolling → annealing → coating with insulating coating. In the embodiments, the hot rolling roughing is performed in 4 passes, and in the comparative example, the hot rolling roughing is performed in 6 passes. The main production processes are shown in Table 2-5.

[0053] Table 2 Continuous casting and heating process parameters

[0054]

[0055] Table 3 Roughing process parameters

[0056]

[0057] Table 4 Finishing rolling process parameters

[0058]

[0059] Table 5 Normalizing and Annealing Process Parameters

[0060]

[0061] The properties of the non-oriented silicon steel produced in each embodiment and comparative example are shown in Table 6.

[0062] Table 6 Performance

[0063]

[0064] As can be seen from the table, the yield strength of the non-oriented silicon steel produced in each embodiment is 536~568MPa, the tensile strength is 649~689MPa, the elongation A50 is 16~18%, and the magnetic polarization J is... 5000 The iron loss is 1.66~1.69T, and the iron loss P is... 1.0 / 400 It is 17.9~19.1 W / kg.

[0065] In Comparative Example 1, the silicon-manganese-copper content was lower than that of the present invention. A 3+3 pass roughing process was used, the reduction rate of the last pass of finishing rolling was low, and the annealing temperature was not controlled according to the annealing temperature T=0.13×(Mn+Cu) / S+900℃ required by the present application. The final result showed that the yield strength of the obtained non-oriented silicon steel was lower than 500 MPa, the iron loss was higher than 20.4 W / kg, and the mechanical and electromagnetic properties did not meet the requirements.

[0066] In Comparative Example 2, the manganese-copper content was higher than that of this invention. After using a 3+3 pass roughing process, low finishing rolling and final rolling temperatures, and a low reduction rate in the last pass, and after the annealing temperature was not controlled according to the annealing temperature T=0.13×(Mn+Cu) / S+900℃ required by this application, the final results showed that although its strength met the requirements, the magnetic polarization intensity J5000 was 1.61T and the iron loss reached 32.6W / kg, which completely failed to meet the electromagnetic performance requirements.

[0067] In Comparative Example 3, although the composition of the non-oriented silicon steel conforms to the present invention, the 3+3 pass roughing process, the initial and final rolling temperatures of the finishing rolling, and the reduction rate of the last pass were low, and the annealing temperature was not controlled according to the annealing temperature T=0.13×(Mn+Cu) / S+900℃ required by this application. Its yield strength was 475MPa, tensile strength was 612MPa, magnetic polarization J5000 was 1.58T, and iron loss reached 30.9W / kg. The mechanical and electromagnetic properties did not meet the requirements.

[0068] The above detailed description of a non-oriented silicon steel and its production method with reference to the embodiments is illustrative rather than limiting. Several embodiments can be listed according to the defined scope. Therefore, changes and modifications without departing from the overall concept of the present invention should be within the protection scope of the present invention.

Claims

1. A non-oriented silicon steel, characterized in that, The chemical composition and weight percentage of the non-oriented silicon steel are as follows: C≤0.002%; Si: 2.90~3.30%; Mn: 0.65~0.80%; P: 0.0040~0.021%; S≤0.0025%; Als: 0.50~0.80%; Cu: 0.50~0.65%, with the remainder being Fe and unavoidable impurities, wherein (Mn+Cu) / S=600~900.

2. The non-oriented silicon steel according to claim 1, characterized in that, The non-oriented silicon steel has a yield strength of 520~590MPa, a tensile strength of 640~740MPa, an elongation A50 of 16~20%, a magnetic polarization J5000 of 1.66~1.71T, and an iron loss P1.0 / 400 of 17.6~20.4W / kg.

3. The method for producing non-oriented silicon steel as described in claim 1 or 2, characterized in that, The production method includes the following steps: smelting → continuous casting → heating → hot rolling → normalizing → pickling → cold rolling → annealing → coating with insulating coating.

4. The production method according to claim 3, characterized in that, In the continuous casting step, the casting speed is controlled at 1.0~1.2m / min, and the superheat of the molten steel is controlled at 15~30℃; the continuous casting produces a billet with a thickness of 210~230mm.

5. The production method according to claim 3, characterized in that, In the heating process, the preheating section temperature is 730~760℃; the first heating section temperature is 1112~1143℃, and the holding time is ≥37min; the second heating section temperature is 1130~1150℃, and the holding time is ≥35min; the soaking section temperature is 1090~1110℃, and the holding time is ≥30min; the total time in the furnace is 140~200min.

6. The production method according to claim 3, characterized in that, In the hot rolling process, the roughing process involves four passes, with each pass having a reduction rate controlled at 35-38%, resulting in a roughing thickness of 34-40 mm. The final rolling temperature is ≥960℃. The finishing process begins at 920-940℃ and involves seven consecutive passes, with the final pass having a reduction rate controlled at 38-40%. The final rolling temperature is 870-930℃. The strip crown is controlled at 30-40 μm, and the wedge shape is controlled at 15-25 μm. The strip is finished to a thickness of 2.0-2.15 mm.

7. The production method according to claim 3, characterized in that, In the hot rolling step, after finishing rolling, the temperature is cooled to 580~620℃ by water cooling before coiling.

8. The production method according to claim 3, characterized in that, In the normalization step, the normalization temperature is 880~960℃ and the steel strip running speed is 40~60m / min.

9. The production method according to claim 3, characterized in that, In the cold rolling step, the total cold rolling reduction rate is controlled at 75-90%; and the thickness is cold rolled to 0.2-0.35 mm.

10. The production method according to claim 3, characterized in that, In the annealing step, a mixture of hydrogen and nitrogen is used as the protective gas, the annealing temperature is T=0.13×(Mn+Cu) / S+900℃, the time is 180~260s, and then the temperature is cooled to below 560℃ at a cooling rate not exceeding 18℃ / s. Finally, the temperature is cooled to room temperature with the furnace. The units of Mn, Cu and S are all .

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