High magnetic permeability non-oriented silicon steel and preparation method thereof

Abstract

The present application discloses a high magnetic permeability non-oriented silicon steel and a preparation method. The preparation method comprises: steelmaking, continuous casting, the chemical composition of the continuous casting billet comprises by mass percentage: C≤0.0025%, Si: 0.38~0.92%, Mn: 0.2~0.3%, Al: 0.28~0.45%, S≤0.003%, the remainder being Fe and impurities; hot rolling, cold rolling; hood annealing,,, [T1] represents the smallest integer not less than T1; continuous annealing,; cooling, coating and finishing. The low-grade non-oriented silicon steel prepared in the present application has not only low iron loss, but also high magnetic induction and high magnetic permeability without adding Sn, Sb precious metal materials and without undergoing normalization process, and can greatly reduce the loss of small-power motors when applied to core materials.

Description

Technical Field

[0001] The present application belongs to the technical field of steel material preparation, and relates to a high magnetic permeability non-oriented silicon steel and a preparation method thereof. Background Art

[0002] Non-oriented silicon steel has good electromagnetic properties and is a soft magnetic alloy. It is mainly used in the production of iron cores of various motors and transformers and other electrical components.

[0003] The motor loss mainly includes the core loss and the copper loss caused by the wire resistance. Among them, the copper loss Q = I 2 R, I is the excitation current, and R is the wire resistance. Excitation current I and (1 / μ) 2 In other words, I is inversely proportional to the magnetic permeability μ. The smaller the motor power, the greater the proportion of copper loss in the total loss of the motor. Therefore, low-power motors require non-oriented silicon steel to have low copper loss, which requires non-oriented silicon steel to have higher magnetic permeability.

[0004] In addition, according to U A =4.44fNAμB m , at a given working voltage U A and operating frequency f, increase the magnetic induction intensity B m Or magnetic permeability μ is conducive to reducing the cross-sectional area A of the iron core or reducing the number of coil turns N, thereby reducing the amount of steel used to make the iron core and the amount of copper wire used to make the coil. It can also significantly reduce the size of the iron core electrical components and greatly reduce the volume of the motor working in a confined space. Therefore, high magnetic permeability and high magnetic induction intensity are important goals of high-performance electrical steel. Summary of the invention

[0005] The purpose of the present application is to provide a high magnetic permeability non-oriented silicon steel and a preparation method thereof.

[0006] To achieve the above application purpose, an embodiment of the present application provides a method for preparing non-oriented silicon steel. The preparation method comprises the following steps:

[0007] 1) Steelmaking and casting to obtain continuous casting billets; the chemical composition of the continuous casting billets includes, by mass percentage: C≤0.0025%, Si: 0.38~0.92%, Mn: 0.2~0.3%, Al: 0.28~0.45%, S≤0.003%, the remainder being Fe and unavoidable inclusions;

[0008] 2) hot rolling and cold rolling the continuously cast billet to obtain a steel strip;

[0009] 3) Hood annealing; Hood annealing temperature T 罩退 satisfy: ,

[0010] T1 meets: ,

[0011] Wherein, [T1] represents the smallest integer not less than T1, Si, Mn, and Al represent their respective mass percentages;

[0012] 4) Continuous annealing; continuous annealing temperature T 连退 satisfy: ;

[0013] 5) Cooling, coating and finishing to prepare the non-oriented silicon steel product.

[0014] Preferably, in the chemical composition of the continuous casting billet, the sum of the mass percentages of Si, Mn and Al is 0.90-1.65%.

[0015] Preferably, in the steelmaking process, converter smelting and RH furnace refining are carried out in sequence to obtain molten steel; in the casting process, the molten steel is continuously cast into a continuous casting billet with a thickness of 210-330 mm.

[0016] Preferably, in the hot rolling process, the continuous casting billet is heated and then subjected to rough rolling and finish rolling in sequence, and then coiled and cooled to room temperature;

[0017] The uniform heating temperature during heating is 1100~1120℃, and the heating time is 160~200min;

[0018] The inlet temperature of finishing rolling is 940~950℃, and the final rolling temperature is 855~865℃;

[0019] The coiling temperature is 650~680℃.

[0020] Preferably, in the hot rolling process, the coiling temperature is 650-660°C.

[0021] Preferably, in the hot rolling process, the thickness of the intermediate billet after rough rolling is 40 mm, and the thickness of the hot rolled plate after finish rolling is 2.65-2.7 mm.

[0022] Preferably, in the cold rolling process, five-stand cold rolling is adopted, the total reduction rate is 81.1-81.5%, the reduction rate of the fifth pass is controlled to be 18-20%, and the exit speed is ≥800m / min.

[0023] Preferably, in the cold rolling process, the concentration of the emulsion used by the rolling mill is 2.5-2.8%, and the temperature of the emulsion is 60±3°C.

[0024] Preferably, in the hood annealing process, the annealing time is 4 hours;

[0025] In the continuous annealing process, the plate passing speed is 150~165m / min, and the protective atmosphere of the annealing furnace adopts 100% H2, or a mixed gas of N2 and H2.

[0026] In order to achieve the above application purpose, an embodiment of the present application provides a non-oriented silicon steel, wherein the non-oriented silicon steel is prepared by the preparation method as described above;

[0027] The thickness of the non-oriented silicon steel is 0.50±0.005mm, and the iron loss P 1.5 / 50 ≤4.8W / kg, magnetic induction intensity B 50 ≥1.72T, magnetic permeability μ 1.0 ≥5500Gs / Oe.

[0028] Compared with the prior art, the beneficial effects of this application are:

[0029] On the basis of the chemical composition design scheme, the annealing temperature of the hood annealing process is controlled based on the contents of chemical components Si, Mn and Al through hood annealing and secondary annealing, and the annealing temperature of the continuous annealing process is further determined based on the annealing temperature of the hood annealing process. By establishing a relationship between the annealing temperatures of the two processes and the chemical components and their contents, as well as a relationship between the annealing temperatures of the two processes, the prepared low-grade non-oriented silicon steel can have not only low iron loss but also high magnetic induction and high magnetic permeability without adding Sn, Sb precious metal materials and undergoing a normalizing process. When applied to core materials, the loss of small-power motors is greatly reduced, the amount of steel used to make the core is reduced, the amount of copper wire used to make the coil is reduced, the size of the core electrical components is significantly reduced, the volume of the motor working in a confined space is greatly reduced, the alloy cost is reduced, the process flow is simplified, and the production cycle is shortened. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in conjunction with the specific implementation methods of the present application. Obviously, the described implementation methods are only part of the implementation methods of the present application, not all of the implementation methods. Based on the implementation methods in the present application, all other implementation methods obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0031] An embodiment of the present application provides a method for preparing non-oriented silicon steel, and non-oriented silicon steel prepared by the preparation method.

[0032] The chemical composition of the non-oriented silicon steel includes, by mass percentage, C≤0.0025%, Si: 0.38-0.92%, Mn: 0.2-0.3%, Al: 0.28-0.45%, S≤0.003%, and the remainder is Fe and unavoidable inclusions.

[0033] The following is an introduction to the role of each chemical element in the above chemical composition.

[0034] C, S: They are harmful elements in non-oriented silicon steel. They generally hinder grain growth and magnetic domain movement by forming fine precipitation or grain boundary segregation, affecting the organizational state of the material. They have a very strong impact on mechanical properties and magnetic properties, so they must be reasonably controlled. In this application, the C content is controlled to be ≤0.0025%, and the S content is ≤0.003%.

[0035] Si: After being dissolved in α-iron, it increases the resistivity and helps to separate the harmful impurity carbon. Si combines with oxygen to transform into stable SiO2, avoiding the lattice distortion of iron. Therefore, the addition of Si can increase the magnetic permeability, reduce the coercive force, and reduce the iron loss. However, too high Si content will make the material hard and brittle, and reduce the thermal conductivity and toughness. In this application, the Si content is controlled to be 0.38~0.92%.

[0036] Mn: It is a beneficial element in steel. In a low content range, it has a great strengthening effect on steel, can improve the strength, hardness and wear resistance of steel, and improve the low-temperature toughness of steel. However, Mn easily forms MnS compounds with S during solidification, pinning at the grain boundary is not conducive to the growth of grains. In this application, the content of Mn is controlled to be 0.2~0.3%.

[0037] Al: It has a deoxidizing effect in steel. Al is easily combined with N to form dispersed AlN precipitate particles, which are retained in the solid solution. It can increase the resistivity and coarsen the grains, improve the magnetic properties of silicon steel, and affect the mechanical properties of steel. However, excessive Al content will increase the difficulty of steelmaking. In this application, the Al content is controlled to be 0.28~0.45%.

[0038] The preparation method of the non-oriented silicon steel comprises the following steps:

[0039] 1) Steelmaking and casting are carried out according to the chemical composition of the non-oriented silicon steel described above to obtain a continuous casting billet. It can be understood that the chemical composition of the continuous casting billet is the same as the chemical composition of the non-oriented silicon steel described above.

[0040] 2) The continuously cast ingot is hot rolled and cold rolled to obtain a steel strip.

[0041] 3) Hood annealing; Hood annealing temperature T 罩退 satisfy: ,

[0042] T1 meets: ,

[0043] Among them, T 罩退 The unit is ℃; [T1] represents the smallest integer not less than T1, and Si, Mn, and Al represent their respective mass percentages. For example, if the mass percentage of Si in the chemical composition is 0.50%, then the value of Si in the formula of T1 is 0.50%; if T1 is 70, then [T1] is 70, and if T1 is 70.2, then [T1] is 71.

[0044] 4) Continuous annealing; continuous annealing temperature T 连退 satisfy: , where T 连退 The unit is ℃.

[0045] 5) Cooling, coating and finishing to prepare the non-oriented silicon steel product.

[0046] Thus, in one embodiment of the present invention, on the basis of the chemical composition design scheme, the annealing temperature of the hood annealing process is controlled based on the contents of the chemical components Si, Mn, and Al through hood annealing and secondary annealing, and the annealing temperature of the continuous annealing process is further determined based on the annealing temperature of the hood annealing process, and the relationship between the annealing temperatures of the two processes and the chemical components and their contents, as well as the relationship between the annealing temperatures of the two processes are established, so that the prepared low-grade non-oriented silicon steel can have not only low iron loss but also high magnetic induction and high magnetic permeability without adding Sn, Sb precious metal materials and without undergoing normalizing process, which greatly reduces the loss of small-power motors when applied to core materials, reduces the amount of steel used to make the core, reduces the amount of copper wire used to make the coil, significantly reduces the size of the core electrical components, greatly reduces the volume of the motor working in a confined space, reduces the alloy cost, simplifies the process flow, and shortens the production cycle.

[0047] The electromagnetic properties of the prepared non-oriented silicon steel product were tested, and it was found that when the thickness of the non-oriented silicon steel was 0.50±0.005mm, its iron loss P 1.5 / 50 ≤4.8W / kg, magnetic induction intensity B 50 ≥1.72T, magnetic permeability μ 1.0 ≥5500Gs / Oe.

[0048] It can be seen that the non-oriented silicon steel prepared by the above preparation method not only has low iron loss, but also has high magnetic induction intensity and magnetic permeability, so that when it is used as an iron core material, it has both low iron loss and low copper loss, thereby greatly reducing the loss of small-power motors.

[0049] Preferably, in the chemical composition, the sum of the mass percentages of Si, Mn and Al is 0.90-1.65%, so that the alloy content can be further controlled and the production cost can be reduced.

[0050] Preferably, in the steelmaking process, converter smelting and RH furnace refining are carried out in sequence to obtain molten steel; further through a casting process, the obtained molten steel is continuously cast into a continuous casting billet with a thickness of 210-330 mm.

[0051] Specifically, during the refining process in the RH furnace, alloy elements are added to the molten steel according to the aforementioned chemical composition design scheme to carry out alloying treatment, so that the molten steel obtained in the steelmaking process meets the aforementioned chemical composition design scheme, laying the foundation for the final non-oriented silicon steel product to have excellent electromagnetic properties.

[0052] Preferably, in the hot rolling process, the continuous casting billet is heated and then subjected to rough rolling and finish rolling in sequence, and then coiled and cooled to room temperature. The soaking temperature during heating is 1100~1120℃, and the heating time is 160~200min; the inlet temperature of finish rolling is 940~950℃, and the final rolling temperature is 855~865℃; the coiling temperature is 650~680℃. By controlling the soaking temperature to be higher than the recrystallization temperature of the continuous casting billet, the continuous casting billet can be fully austenitized during the heating process, and the internal stress is eliminated, thereby improving the uniformity of the structure; the inlet temperature of finish rolling is an important parameter that determines the final structure and properties of non-oriented silicon steel. If the inlet temperature of finish rolling is too high, the steel may overheat during the finish rolling process, affecting the uniformity of the structure and mechanical properties; if the inlet temperature of finish rolling is too low, it will increase the difficulty of rolling and even cause rolling cracks; the appropriate final rolling temperature helps to promote the formation of an ideal fine-grained structure in the subsequent cooling process, thereby improving The final rolling temperature is too high, which may cause the steel to form a coarse structure during the subsequent cooling process, affecting the performance. The coiling temperature directly affects the cooling rate and phase change process of the steel, thereby affecting the microstructure and mechanical properties of the steel. The appropriate coiling temperature helps to obtain an ideal combination of organizational structure and performance. The coiling temperature is too high, which may cause the steel to form a coarse structure during the subsequent cooling process. While the coiling temperature is too low, it may cause the steel to form cracks or uneven structure during the coiling process.

[0053] More preferably, in the hot rolling process, the coiling temperature is 650-660° C. Since the steel strip is subsequently subjected to hood annealing after the cold rolling process, the requirements on the grain size of the hot-rolled structure can be relaxed, and even if a lower coiling temperature is used, the electromagnetic properties of the final non-oriented silicon steel product can meet the requirements.

[0054] Specifically, in the hot rolling process, the hot rolled steel coil is naturally cooled to room temperature after being coiled, so that the cost can be reduced.

[0055] Preferably, in the hot rolling process, the thickness of the intermediate billet after rough rolling is controlled to be 40 mm, and the thickness of the hot-rolled plate after finish rolling is controlled to be 2.65-2.7 mm.

[0056] Preferably, in the cold rolling process, five-stand cold rolling is adopted, and specifically, a UCM five-stand cold rolling mill can be adopted; the total reduction rate is controlled to be 81.1-81.5%, the reduction rate of the fifth pass is controlled to be 18-20%, and the outlet speed is ≥800m / min. By controlling the rolling reduction rate, especially controlling the fifth pass to adopt a small reduction, not only can the rolling be ensured to be smooth and the non-oriented silicon steel strip with a thickness of 0.50±0.005mm can be finally rolled, but also the quality of the finished product can be ensured to have a good plate shape.

[0057] Preferably, in the cold rolling process, the emulsion concentration used by the rolling mill is 2.5-2.8%, and the emulsion temperature is 60±3° C. The high-concentration and high-temperature emulsion ratio mode can effectively improve the process lubricity, reduce rolling deformation heat, and improve rolling stability.

[0058] Preferably, in the hood annealing process, the annealing time is 4 hours to ensure that the grains are fully grown and rearranged, thereby improving the magnetic properties of the non-oriented silicon steel.

[0059] Preferably, in the continuous annealing process, the plate passing speed is 150-165 m / min, and the protective atmosphere of the annealing furnace is 100% H2, or a mixture of N2 and H2. The so-called plate passing speed refers to the running speed of silicon steel in the annealing furnace. The plate passing speed within this range can improve production efficiency; using 100% H2 or a mixture of N2 and H2 as the protective atmosphere can accurately control the atmosphere composition in the annealing furnace, wherein the pure H2 atmosphere has excellent reducing properties, which can completely remove the oxides on the surface of the plate and prevent the formation of new oxides during the annealing process; while the mixture of N2 and H2 can reduce the safety risks that may be caused by pure H2 while ensuring reducing properties.

[0060] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of the present application. They are not intended to limit the scope of protection of the present application. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present application should be included in the scope of protection of the present application.

[0061] The specific implementation methods of the present application are introduced below through three embodiments. Of course, these three embodiments are only a part of the many variations of the present application, but not all. The specific implementation process of these embodiments is as follows:

[0062] (1) First, steelmaking is performed, followed by converter smelting and RH furnace refining to obtain molten steel. During the refining process in the RH furnace, alloying elements are added to the molten steel according to the aforementioned chemical composition design scheme to perform alloying treatment. During the steelmaking process, except for Si, Mn, and Al, no other alloying elements are added. Then, the refined molten steel is cast to obtain a continuous casting billet; the chemical composition of the continuous casting billet is shown in Table 1.

[0063] Table 1

[0064]

[0065] (2) The continuously cast ingot is hot rolled and cold rolled to obtain a steel strip.

[0066] First, hot rolling: the continuous casting billet is heated, and then it is made into an intermediate billet through rough rolling, and then it is made into a hot-rolled steel coil through finish rolling and coiling, and then it is naturally cooled to room temperature; among them, the thickness of the continuous casting billet, the soaking temperature and heating time during heating, the thickness of the intermediate billet, the entrance temperature and final rolling temperature of the finish rolling, the coiling temperature and the thickness of the hot-rolled plate are shown in Table 2 respectively.

[0067] Table 2

[0068]

[0069] Then cold rolling: UCM five-stand cold rolling mill is used to roll the non-oriented silicon steel strip with a thickness of 0.50±0.005mm, and the outlet speed is controlled to be ≥800m / min; the total reduction rate, the reduction rate of the fifth pass, the emulsion concentration and the emulsion temperature used by the rolling mill are shown in Table 3.

[0070] Table 3

[0071]

[0072] (3) Hood annealing.

[0073] Hood annealing temperature T 罩退 As shown in Table 4, the annealing time is 4 h.

[0074] (4) Continuous annealing

[0075] Continuous annealing temperature T 连退 , plate passing speed, and protective atmosphere of the annealing furnace are shown in Table 4.

[0076] Table 4

[0077]

[0078] (5) Cooling, coating and finishing to obtain the non-oriented silicon steel product.

[0079] The magnetic properties of the obtained non-oriented silicon steel were tested according to GB / T 3655-2022 standard, and the iron loss P was obtained. 1.5 / 50 , magnetic induction intensity B 50 and magnetic permeability μ 1.0 The results are shown in Table 5.

[0080] Table 5

[0081]

[0082] It can be seen from the above embodiments that the non-oriented silicon steel not only has low iron loss, but also has high magnetic induction intensity and magnetic permeability, so that when it is used as an iron core material, it has both low iron loss and low copper loss, thereby greatly reducing the loss of small power motors.

[0083] In summary, the beneficial effects of this application are:

[0084] (1) On the basis of the chemical composition design scheme, the annealing temperature of the hood annealing process is controlled based on the contents of chemical components Si, Mn and Al through hood annealing and secondary annealing, and the annealing temperature of the continuous annealing process is further determined based on the annealing temperature of the hood annealing process. By establishing the relationship between the annealing temperature of the two processes and the chemical composition and its content, as well as the relationship between the annealing temperature of the two processes, the prepared low-grade non-oriented silicon steel can have not only low iron loss but also high magnetic induction and high magnetic permeability without adding Sn and Sb precious metal materials and without normalizing process. When used as core material, it greatly reduces the loss of small-power motors, reduces the amount of steel used in making the core, reduces the amount of copper wire used in making the coil, significantly reduces the size of the core electrical components, greatly reduces the volume of the motor working in a confined space, reduces the alloy cost, simplifies the process flow, and shortens the production cycle.

[0085] (2) When the thickness of the non-oriented silicon steel is 0.50±0.005 mm, its iron loss P 1.5 / 50 ≤4.8W / kg, magnetic induction intensity B 50 ≥1.72T, magnetic permeability μ 1.0 ≥5500Gs / Oe.

[0086] It should be understood that although this specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation mode may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0087] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of the present application. They are not intended to limit the scope of protection of the present application. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present application should be included in the scope of protection of the present application.

Claims

1. A method for preparing non-oriented silicon steel, characterized in that: The preparation method comprises the following steps: 1) Steelmaking and casting to obtain continuous casting billets; the chemical composition of the continuous casting billets includes, by mass percentage: C≤0.0025%, Si: 0.38~0.92%, Mn: 0.2~0.3%, Al: 0.28~0.45%, S≤0.003%, the remainder is Fe and unavoidable inclusions, wherein the sum of the mass percentages of Si, Mn and Al is 0.90~1.65%; 2) hot rolling and cold rolling the continuously cast billet to obtain a steel strip; 3) Hood annealing; annealing time is 4h, hood annealing temperature is T 罩退 satisfy: , T1 meets: , Wherein, [T1] represents the smallest integer not less than T1, Si, Mn, and Al represent their respective mass percentages; 4) Continuous annealing; the plate passing speed is 150~165m / min, and the continuous annealing temperature is T 连退 satisfy: ; 5) Cooling, coating and finishing to prepare the non-oriented silicon steel product.

2. The method for preparing non-oriented silicon steel according to claim 1, characterized in that: In the steelmaking process, converter smelting and RH furnace refining are carried out in sequence to obtain molten steel; in the casting process, the molten steel is continuously cast into continuous casting billets with a thickness of 210~330mm.

3. The method for preparing non-oriented silicon steel according to claim 1, characterized in that: In the hot rolling process, the continuous casting slab is heated and then subjected to rough rolling and finish rolling in sequence, and then coiled and cooled to room temperature; The uniform heating temperature during heating is 1100~1120℃, and the heating time is 160~200min; The inlet temperature of finishing rolling is 940~950℃, and the final rolling temperature is 855~865℃; The coiling temperature is 650~680℃.

4. The method for preparing non-oriented silicon steel according to claim 3, characterized in that: In the hot rolling process, the coiling temperature is 650~660℃.

5. The method for preparing non-oriented silicon steel according to claim 1, characterized in that: In the hot rolling process, the thickness of the intermediate billet after rough rolling is 40 mm, and the thickness of the hot rolled plate after finish rolling is 2.65~2.7 mm.

6. The method for preparing non-oriented silicon steel according to claim 1, characterized in that: In the cold rolling process, five-stand cold rolling is adopted, the total reduction rate is 81.1~81.5%, the reduction rate of the fifth pass is controlled at 18~20%, and the exit speed is ≥800m / min.

7. The method for preparing non-oriented silicon steel according to claim 1, characterized in that: In the cold rolling process, the emulsion concentration used by the rolling mill is 2.5~2.8%, and the emulsion temperature is 60±3℃.

8. The method for preparing non-oriented silicon steel according to claim 1, characterized in that: In the continuous annealing process, the protective atmosphere of the annealing furnace is 100% H2, or a mixed gas of N2 and H2.

9. A non-oriented silicon steel, characterized in that: The non-oriented silicon steel is prepared by the preparation method according to any one of claims 1 to 8; The thickness of the non-oriented silicon steel is 0.50±0.005mm, and the iron loss P 1.5 / 50 ≤4.8W / kg, magnetic induction intensity B 50 ≥1.72T, magnetic permeability μ 1.0 ≥5500Gs / Oe.

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