High-al non-oriented silicon steel wound iron core and preparation method therefor

Abstract

Disclosed in the present invention are a high-Al non-oriented silicon steel wound iron core and a preparation method therefor. In the preparation method, normalization before cold rolling is omitted, and secondary annealing is added after winding formation; 1.0-2.0% of a high-Al component is used as a chemical component, where Al / Si=1.0-1.4, C+S+O+N≤0.007%, and Sn=0.01×Si+0.04×Al or Sb=0.01×Si+0.04×Al; the heating temperature of hot rolling T1=1160-20×[Si]-10×[Al], the finish rolling temperature T2=880-20×[Si]-15×[Al], and the coiling temperature T3=600+5×[Si]-30×[Al]; and during acid pickling, a mixed solution of NH4HF2+HCl is used as an acid pickling solution in both a first and a second stage, and a mixed solution of H2O2+HCl is used as an acid pickling solution in a third stage.

Description

High-Al non-oriented silicon steel wound core and preparation method thereof Technical Field

[0001] The present invention belongs to the technical field of steel smelting, relates to a method for preparing a high-Al non-oriented silicon steel wound core, and also relates to a high-Al non-oriented silicon steel wound core prepared by the preparation method. Background Art

[0002] With economic development and technological advancements, small electric vehicles such as electric bicycles, electric tricycles, electric scooters, and self-balancing scooters are becoming increasingly popular among consumers. They are widely used for daily short-distance travel, as well as in food delivery and express delivery. As the power source of electric vehicles, motors are an essential component.

[0003] The wheel hubs of current small electric vehicles mainly use outer rotor permanent magnet brushless DC motors. This type of wheel hub motor has a small diameter and high speed, but the loss of the motor core is relatively high.

[0004] In order to reduce core loss and improve the material utilization rate of rotor core stamping laminations, hub motors usually use thin-gauge non-oriented silicon steel for winding lamination. However, during the winding process, the non-oriented silicon steel is subjected to tensile stress on the outside and compressive stress on the inside, and the yoke will undergo plastic deformation or even cracking, resulting in increased core loss, deteriorated performance, and reduced product qualification rate.

[0005] Summary of the Invention

[0006] The object of the present invention is to provide a method for preparing a high-Al non-oriented silicon steel wound core, so as to solve the technical problem in the prior art that the electromagnetic properties and plastic toughness of non-oriented silicon steel cannot simultaneously meet the application requirements of the rotor wound core; and the object of the present invention is also to provide a high-Al non-oriented silicon steel wound core prepared by the preparation method.

[0007] To achieve one of the above objectives, an embodiment of the present invention provides a method for preparing a high-Al non-oriented silicon steel wound core, comprising the steps of molten steel smelting, continuous casting, hot rolling, pickling, cold rolling, primary annealing, winding and secondary annealing.

[0008] In the molten steel smelting process, the chemical composition of the molten steel finally obtained by smelting includes, by mass percentage, C≤0.0025%, Si 1.0-1.5%, Al 1.0-2.0%, Mn 0.2-0.4%, Nb≤0.002%, V≤0.002%, Ti≤0.002%, Ni≤0.03%, Cr≤0.03%, Cu≤0.01%, N≤0.002%, P 0.015-0.020%, S≤0.0015%, and Sn or Sb, with the remainder being Fe and unavoidable impurities, wherein Sn=0.01×Si+0.04×Al, Sb=0.01×Si+0.04×Al, and Al / Si=1.0-1.4, and C+S+O+N≤0.007%;

[0009] In the hot rolling process, the continuous casting slab obtained in the continuous casting process is sequentially heated, rough rolled, finish rolled, and coiled to obtain a hot rolled coil. The heating temperature T1 is 1160-20×[Si]-10×[Al], the heating time is 160-180 min, the start rolling temperature of the finish rolling is 910-960° C., the final rolling temperature of the finish rolling is T2=880-20×[Si]-15×[Al], and the coiling temperature is T3=600+5×[Si]-30×[Al].

[0010] In the pickling process, pickling is performed in three stages. The pickling solution in the first stage is a mixed solution of NH4HF2+HCl, the concentration of NH4HF2 is 60-80 g / L, and the concentration of HCl is 150-200 g / L; the pickling solution in the second stage is a mixed solution of NH4HF2+HCl, the concentration of NH4HF2 is 80-100 g / L, and the concentration of HCl is 200-250 g / L; the pickling solution in the third stage is a mixed solution of H2O2+HCl, the concentration of H2O2 is 30-50 g / L, and the concentration of HCl is 100-120 g / L; the pickling time t and the pickling temperature T4 of each of the three stages correspond to each other and meet the following requirements:

[0011] Where, B = -0.01 × [NH4HF2] 2 +2×[HCl]-75, the unit of t is s, and the unit of temperature is ℃.

[0012] As a further improvement of one embodiment of the present invention, in the primary annealing process, the chilled coil obtained in the cold rolling process is subjected to high-temperature annealing under a pure N2 protective atmosphere, the annealing temperature T5 = 900 + 30×[Si] + 20×[Al], in ° C., the annealing time is 80 to 100 seconds, and the steel coil after high-temperature annealing is controlled to complete sufficient recrystallization, and the average grain size is 70 to 90 μm.

[0013] As a further improvement of one embodiment of the present invention, in the primary annealing process, the steel coil after high temperature annealing is cooled, coated and finished to obtain non-oriented silicon steel, and the cooling rate before cooling to 400-550°C is controlled to be ≤10°C / s.

[0014] As a further improvement of one embodiment of the present invention, the iron loss P of the non-oriented silicon steel obtained by the primary annealing process is 1.5 / 50 ≤3.0W / kg, magnetic induction B 5000 ≥1.67T, yield strength YS is 200~260MPa, elongation ≥25%.

[0015] As a further improvement of one embodiment of the present invention, the secondary annealing process is carried out under a pure N2 protective atmosphere, and the annealing temperature T6=800+2000×σ, in units of °C, where σ is the strain of the iron core during the winding process.

[0016] As a further improvement of one embodiment of the present invention, in the winding forming process, the non-oriented silicon steel obtained in the primary annealing process is divided into strips, the tooth groove portion is punched, and then the yoke portion is wound and formed to obtain a high-Al non-oriented silicon steel wound core, and the strain σ of the core during the winding forming process is controlled to be 2 to 8%.

[0017] As a further improvement of one embodiment of the present invention, in the hot rolling process, the continuous casting billet is sent to a heating furnace for heating, the furnace entry temperature of the continuous casting billet is 500-600°C, the rough rolling is performed by a double stand for 6 passes, including 1 rough rolling performed on the first stand and 5 rough rolling performed on the second stand, the finishing rolling is performed by a seven-stand finishing mill for 7 passes, the total reduction rate of the finishing rolling is controlled to be 93-94%, and the thickness of the hot rolled coil is 1.8-2.0 mm.

[0018] As a further improvement of one embodiment of the present invention, in the cold rolling process, a five-stand cold rolling mill is used to continuously cold roll the hot-rolled strip after the pickling process to obtain a chilled coil with a thickness of 0.3 to 0.4 mm, and the reduction rate of each pass is controlled to be 25 to 35%, and the total reduction rate is controlled to be 80 to 90%.

[0019] To achieve the above-mentioned object of the invention, one embodiment of the present invention further provides a high-Al non-oriented silicon steel wound core, which is prepared by the above-mentioned method for preparing a high-Al non-oriented silicon steel wound core.

[0020] As a further improvement of one embodiment of the present invention, the iron loss P of the high Al non-oriented silicon steel wound core is 1.5 / 50 ≤2.5W / kg, magnetic induction B 5000 ≥1.72T.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) Based on the chemical composition design scheme, on the one hand, by reasonably controlling the content of Si and Al alloy elements and the content relationship between the two, not only can the magnetic induction intensity of the finished product be improved under the condition of obtaining good iron loss, but the finished product can also have good plasticity and elongation, meeting the production requirements of wound core processing; further, by adding micro-alloying elements Sn or Sb and limiting the relationship between their content and Al and Si content, the principle that Sn or Sb is easy to enrich on the surface of the strip can be used to avoid the formation of dense AlN in the annealing process of the strip, promote the optimization of the structure of the final prepared non-oriented silicon steel matrix, so that it can obtain excellent elongation and electromagnetic properties, meeting the production requirements of wound core; overall, through the above chemical composition design scheme, not only the resistivity of non-oriented silicon steel can be improved, eddy current loss can be reduced, and magnetic properties can be improved, but also the non-oriented silicon steel can have excellent hot workability and cold workability, and stable rolling and winding processing can be achieved.

[0023] (2) Iron loss P of non-oriented silicon steel obtained after the primary annealing process 1.5 / 50 ≤3.0W / kg, magnetic induction B 5000 ≥1.67T, yield strength YS is 200~260MPa, elongation ≥25%, it not only has excellent magnetic properties, but also has good mechanical properties, laying the foundation for the winding forming process of the iron core.

[0024] (3) The above preparation method is based on the chemical composition design scheme of low Si and high Al, and the alloy composition is simple, which reduces the cost. The prepared non-oriented silicon steel has low iron loss, high magnetic induction, low yield strength, and high elongation, which is conducive to the winding of the iron core and no cracking during winding. Further, by performing secondary annealing after the iron core is wound, the plastic deformation generated during the winding process of the iron core can be used to induce the secondary growth of ferrite grains, thereby reducing the iron loss of the iron core, thereby solving the problem of damage to the magnetic properties of the iron core caused by the plastic strain generated during the winding and bending deformation of the wound iron core, and improving the yield rate and working efficiency of the hub motor iron core. The high Al non-oriented silicon steel wound iron core finally prepared has an iron loss P 1.5 / 50 ≤2.5W / kg, magnetic induction B 5000 ≥1.72T, with excellent magnetic induction performance. When used in products such as hub motors, the electromagnetic performance is qualified and can meet the application energy efficiency requirements of products such as hub motors. In addition, the normalization process before cold rolling is eliminated, which simplifies the production process, not only reducing the production cost of the hub motor, but also greatly improving the performance of the hub motor. DETAILED DESCRIPTION

[0025] The present invention will be described in detail below with reference to specific embodiments. However, these embodiments do not limit the present invention, and any structural, methodological, or functional changes made by those skilled in the art based on these embodiments are all within the scope of protection of the present invention.

[0026] An embodiment of the present invention provides a method for preparing a high-Al non-oriented silicon steel wound core, and a high-Al non-oriented silicon steel wound core prepared by the preparation method.

[0027] In this embodiment, the chemical composition design scheme of the high-Al non-oriented silicon steel wound core is as follows, and its chemical composition, in mass percentage, includes: C≤0.0025%, Si 1.0-1.5%, Al 1.0-2.0%, Mn 0.2-0.4%, Nb≤0.002%, V≤0.002%, Ti≤0.002%, Ni≤0.03%, Cr≤0.03%, Cu≤0.01%, N≤0.002%, P 0.015-0.020%, S≤0.0015%, and Sn or Sb, and the rest is Fe and unavoidable impurities, wherein Sn=0.01×Si+0.04×Al, Sb=0.01×Si+0.04×Al, Al / Si=1.0-1.4, and C+S+O+N≤0.007%.

[0028] That is, in the above chemical composition design scheme, one of Sn or Sb is included.

[0029] Specifically, the chemical composition of the high-Al non-oriented silicon steel wound core of the present invention includes, by mass percentage, C≤0.0025%, Si 1.0-1.5%, Al 1.0-2.0%, Mn 0.2-0.4%, Nb≤0.002%, V≤0.002%, Ti≤0.002%, Ni≤0.03%, Cr≤0.03%, Cu≤0.01%, N≤0.002%, P 0.015-0.020%, S≤0.0015%, and Sn=0.01×Si+0.04×Al, the rest is Fe and unavoidable impurities, and Al / Si=1.0-1.4, C+S+O+N≤0.007%.

[0030] Alternatively, the chemical composition of the high-Al non-oriented silicon steel wound core of the present invention includes, by mass percentage, C≤0.0025%, Si 1.0-1.5%, Al 1.0-2.0%, Mn 0.2-0.4%, Nb≤0.002%, V≤0.002%, Ti≤0.002%, Ni≤0.03%, Cr≤0.03%, Cu≤0.01%, N≤0.002%, P 0.015-0.020%, S≤0.0015%, and Sb=0.01×Si+0.04×Al, the rest is Fe and unavoidable impurities, and Al / Si=1.0-1.4, C+S+O+N≤0.007%.

[0031] Based on the above chemical composition design scheme, on the one hand, by adding Si, Al, and Mn, the resistivity of non-oriented silicon steel can be improved and the iron loss can be reduced. However, as their content increases, the saturation magnetic induction intensity also decreases, the magnetic permeability decreases, and as the Si content increases, the toughness of the steel decreases sharply, and the problem of strip breakage is very likely to occur during the cold rolling process. The present invention reasonably controls the content of Si and Al alloy elements and the content relationship between the two, not only can the magnetic induction intensity of the finished product be improved while obtaining good iron loss, but the finished product can also have good plasticity and elongation, meeting the production requirements of wound iron core processing; further, by adding microalloying elements Sn or Sb and limiting the relationship between their content and the Al and Si content, the principle that Sn or Sb is easily enriched on the surface of the strip can be utilized to avoid the formation of dense AlN in the strip during annealing, promote the organizational optimization of the finally prepared non-oriented silicon steel matrix, so that it obtains excellent elongation and electromagnetic properties, meeting the production requirements of wound iron core.

[0032] In general, the above-mentioned chemical composition design scheme can not only improve the resistivity of non-oriented silicon steel, reduce eddy current loss, and improve magnetic properties, but also make the non-oriented silicon steel have excellent hot workability and cold workability, and achieve stable rolling and winding processing.

[0033] The preparation method of the high-Al non-oriented silicon steel wound core is described in detail below, including the steps of molten steel smelting, continuous casting, hot rolling, pickling, cold rolling, primary annealing, winding and secondary annealing.

[0034] (1) Molten steel smelting

[0035] The chemical composition of the molten steel finally obtained by smelting includes, by mass percentage, C≤0.0025%, Si 1.0-1.5%, Al 1.0-2.0%, Mn 0.2-0.4%, Nb≤0.002%, V≤0.002%, Ti≤0.002%, Ni≤0.03%, Cr≤0.03%, Cu≤0.01%, N≤0.002%, P 0.015-0.020%, S≤0.0015%, and Sn or Sb, with the remainder being Fe and unavoidable impurities, wherein Sn=0.01×Si+0.04×Al, Sb=0.01×Si+0.04×Al, and Al / Si=1.0-1.4, and C+S+O+N≤0.007%.

[0036] That is to say, the molten steel smelting process is carried out according to the chemical composition design scheme of the above-mentioned high-Al non-oriented silicon steel wound core, so that the chemical composition of the molten steel finally obtained by smelting is exactly the same as the chemical composition of the finally prepared high-Al non-oriented silicon steel wound core.

[0037] Specifically, the molten steel smelting process includes the following steps performed in sequence:

[0038] a.KR desulfurization of molten iron

[0039] The molten iron is desulfurized in the KR desulfurization device, and the slag removal rate is controlled to be greater than 95%. The S content in the molten iron is ≤0.001% when it leaves the station.

[0040] b. Converter smelting

[0041] The desulfurized molten iron is fed into the converter and mixed with scrap steel to form molten steel. Dephosphorization and desiliconization are then carried out until the molten steel contains S ≤ 0.002%, P ≤ 0.02%, and N ≤ 0.0025%. The scrap steel is all recycled non-oriented silicon steel, and the weight of the scrap steel accounts for 12-16% of the total converter charge.

[0042] c.RH vacuum refining

[0043] RH vacuum cycle degassing equipment is used to vacuum decarburize, deoxidize, alloy and remove inclusions from molten steel after converter smelting.

[0044] During the RH vacuum refining process, the O element in the converter steel is used for decarburization, followed by deoxidation with the alloying element Si. During the alloying process, the alloying element Si is added first, followed by the alloying element Al, and then metallic Sn or Sb is added based on the actual Si / Al ratio. Finally, under vacuum conditions, a clean cycle is performed to effectively remove inclusions from the molten steel.

[0045] (2) Continuous casting

[0046] The molten steel obtained in the molten steel smelting process is continuously cast into a continuous casting billet with a thickness of 220 mm using continuous casting equipment. The chemical composition of the obtained continuous casting billet is consistent with the chemical composition of the molten steel finally obtained in the molten steel smelting process, and is also exactly the same as the chemical composition of the high-Al non-oriented silicon steel wound core finally prepared.

[0047] The continuous casting mold uses a special mold slag. Its chemical composition, by mass percentage, includes: SiO2 28-36%, MgO ≤ 5%, CaO 16-24%, Fe2O3 ≤ 5%, Al2O3 ≤ 5%, Na2O 13-15%, CaF 8-14%, Li2O 1.1-1.5%, B2O3 4.5-5.5%, TC ≤ 1.5%, and exothermic agent 1.9-2.1%. The mold slag's composition design, including the addition of Li2O, B2O3, and exothermic agent, not only inhibits the redox reaction between Al in the molten steel and SiO2 in the mold slag during the continuous casting process, but also improves heat transfer and provides lubrication, preventing defects such as cracks on the surface of the continuously cast ingot.

[0048] Preferably, the heat-generating agent is a calcium-silicon alloy, wherein the mass percentage of Ca is 40% and the mass percentage of Si is 60%.

[0049] Preferably, the mold slag has a binary basicity of 0.61 to 0.63, a melting point of 1000±40° C., and a viscosity of 0.2±0.05 Pa·s.

[0050] Preferably, during the continuous casting process, electromagnetic stirring is used in the secondary cooling zone, the stirring current is 400A, the stirring frequency is 8Hz, and the continuous casting speed is 1.2±0.1m / min.

[0051] (3) Hot rolling

[0052] The continuous casting slab obtained from the continuous casting process is sequentially heated, rough rolled, finish rolled, and coiled to obtain hot rolled coils. The heating temperature T1 is 1160°C - 20×[Si] - 10×[Al], the heating time is 160-180 minutes, the start temperature of the finish rolling is 910-960°C, the final rolling temperature T2 is 880°C - 20×[Si] - 15×[Al], and the coiling temperature T3 is 600°C + 5×[Si] - 30×[Al].

[0053] Here, [Si] represents the mass percentage of Si in the continuous casting billet, and [Al] represents the mass percentage of Al in the continuous casting billet. For example, if the Si content in the continuous casting billet is 1.2%, then [Si] = 1.2. This applies to the following text.

[0054] In this way, based on the Si and Al element contents in the chemical composition, the temperature of each step in the hot rolling process can be controlled to control the type and thickness of the Al2O3 and SiO2 composite oxides.

[0055] Preferably, the continuous casting billet is fed into a heating furnace for heating, the furnace entry temperature of the continuous casting billet is 500-600°C, the rough rolling is performed by a double stand for 6 passes, including 1 rough rolling performed in the first stand and 5 rough rolling performed in the second stand, the finishing rolling is performed by a seven-stand finishing mill for 7 passes, the total reduction rate of the finishing rolling is controlled to be 93-94%, and the thickness of the hot rolled coil is 1.8-2.0 mm.

[0056] (4) Pickling

[0057] The pickling is carried out in three stages. The pickling solution of the first stage is a mixed solution of NH4HF2+HCl, the concentration of NH4HF2 is 60-80 g / L, and the concentration of HCl is 150-200 g / L; the pickling solution of the second stage is a mixed solution of NH4HF2+HCl, the concentration of NH4HF2 is 80-100 g / L, and the concentration of HCl is 200-250 g / L; the pickling solution of the third stage is a mixed solution of H2O2+HCl, the concentration of H2O2 is 30-50 g / L, and the concentration of HCl is 100-120 g / L; the pickling time t and pickling temperature T4 of each of the three stages correspond to each other and meet the following requirements:

[0058] Where, B = -0.01 × [NH4HF2] 2 +2×[HCl]-75, the unit of t is s, and the unit of temperature is ℃.

[0059] [NH4HF2] represents the concentration of NH4HF2 in the mixed solution, and [HCl] represents the concentration of HCl in the mixed solution. For example, when the concentration of NH4HF2 is 80 g / L, [NH4HF2] = 80. In the third stage, since no NH4HF2 is added, [NH4HF2] = 0.

[0060] By using the above pickling method, a mixed solution of NH4HF2+HCl is used instead of the traditional HCl pickling process. Combined with the control of the NH4HF2 concentration, the HCl concentration, and the relationship between the pickling time and temperature and the NH4HF2 concentration and the HCl concentration, the Al2O3 and SiO2 oxide layers on the surface of the hot-rolled coil can be cleaned, solving the problem of Al2O3 being difficult to pickle on the surface of high-Al steel. Furthermore, the use of a mixed solution of H2O2+HCl in the third stage of pickling can avoid intergranular corrosion on the surface of the hot-rolled coil.

[0061] (5) Cold rolling

[0062] Preferably, five stands are used to continuously cold roll the hot-rolled strip after the pickling process to obtain a chilled coil with a thickness of 0.3 to 0.4 mm, and the reduction rate of each pass is controlled to be 25 to 35%, and the total reduction rate is controlled to be 80 to 90%.

[0063] (6) Primary annealing

[0064] The chilled coil obtained from the cold rolling process is subjected to continuous high-temperature annealing, and an insulating coating is applied to the upper and lower surfaces of the strip to obtain non-oriented silicon steel. The specific coating operation can be achieved using existing feasible coating technologies and will not be described in detail here.

[0065] Preferably, the resulting chilled coil is subjected to high-temperature annealing in a pure N2 protective atmosphere at an annealing temperature of T5 = 900 + 30 × [Si] + 20 × [Al] (in °C) for 80 to 100 seconds. The high-temperature annealing ensures that the coil is fully recrystallized and has an average grain size of 70 to 90 μm. Using a pure N2 protective atmosphere can reduce the formation of nodules caused by the strip reacting with the carbon jacket rollers during the high-temperature annealing process.

[0066] Preferably, during cooling, the cooling rate before cooling to 400-550° C. is controlled to be ≤10° C. / s.

[0067] The iron loss P of the non-oriented silicon steel obtained by the primary annealing process is 1.5 / 50 ≤3.0W / kg, magnetic induction B 5000 ≥1.67T, yield strength YS is 200~260MPa, elongation ≥25%, it not only has excellent magnetic properties, but also has good mechanical properties, laying the foundation for the winding forming process of the iron core.

[0068] (7) Winding

[0069] After the non-oriented silicon steel obtained in the primary annealing process is stripped, the tooth groove portion is punched, and then the yoke portion is wound to obtain a high-Al non-oriented silicon steel wound core. The strain σ of the core is controlled to be 2-8% during the winding process.

[0070] (8) Secondary annealing

[0071] The high Al non-oriented silicon steel wound core obtained by winding is subjected to secondary annealing in a pure N2 protective atmosphere, and the annealing temperature is T6=800+2000×σ, in degrees Celsius.

[0072] Through the secondary annealing process, the plastic deformation generated during the winding and forming process of the iron core can be used to induce the secondary growth of ferrite grains, thereby reducing the iron loss of the iron core, thereby solving the problem of damage to the magnetic properties of the iron core caused by the plastic strain generated during the winding and bending deformation of the wound iron core, thereby improving the yield rate and working efficiency of the hub motor iron core; further, through the quantitative relationship between the annealing temperature and the strain σ of the wound iron core, the electromagnetic properties of the iron core are improved, so as to maximize the physical and electromagnetic properties of the material itself.

[0073] The above preparation method is based on the chemical composition design scheme of low Si and high Al, and the alloy composition is simple, which reduces the cost. The prepared non-oriented silicon steel has low iron loss, high magnetic induction, low yield strength, and high elongation, which is conducive to the winding and forming of the iron core, and there is no cracking during the winding; further, by performing secondary annealing after the iron core is wound and formed, the plastic deformation generated in the winding and forming process of the iron core can be used to induce the secondary growth of ferrite grains, thereby reducing the iron loss of the iron core, thereby solving the problem of damage to the magnetic properties of the iron core caused by the plastic strain generated in the winding and bending deformation process of the wound iron core, improving the yield rate and working efficiency of the hub motor iron core, and eliminating the normalizing process before cold rolling, simplifying the production process, not only reducing the production cost of the hub motor, but also greatly improving the performance of the hub motor.

[0074] An embodiment of the present invention further provides a high-Al non-oriented silicon steel wound core, which is prepared using the above-mentioned preparation method.

[0075] After testing, the high Al non-oriented silicon steel wound core prepared by the above preparation method has a low iron loss P 1.5 / 50 ≤2.5W / kg, magnetic induction B 5000 ≥1.72T, excellent magnetic induction performance, qualified electromagnetic performance when used in products such as hub motors, and can meet the application energy efficiency requirements of products such as hub motors.

[0076] The detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

[0077] The beneficial effects of the present invention are further illustrated below through three embodiments. Of course, these three embodiments are only a part of the many variations of the present invention, but not all of them.

[0078] Three embodiments each provide a high-Al non-oriented silicon steel wound core. The chemical compositions of the molten steel obtained by smelting molten steel, the continuously cast ingot, and the ultimately prepared high-Al non-oriented silicon steel wound core in each embodiment are the same. The chemical compositions of the three embodiments are specifically described in Table 1. In addition to the chemical elements shown in Table 1, the chemical compositions of the three embodiments include C ≤ 0.0025%, Nb ≤ 0.002%, V ≤ 0.002%, Ti ≤ 0.002%, Ni ≤ 0.03%, Cr ≤ 0.03%, Cu ≤ 0.01%, N ≤ 0.002%, P 0.015-0.020%, S ≤ 0.0015%, C+S+O+N ≤ 0.007%, and the remainder being Fe and unavoidable impurities.

[0079] Table 1

[0080] Example 1

[0081] The preparation method of high Al non-oriented silicon steel wound core comprises the following steps:

[0082] (1) Molten steel smelting

[0083] The chemical composition of the molten steel obtained by smelting is as described above, please refer to Table 1 for details.

[0084] Specifically, the molten steel smelting process includes the following steps performed in sequence:

[0085] a.KR desulfurization of molten iron

[0086] The molten iron is desulfurized in the KR desulfurization device, the slag removal rate is controlled to 97%, and the S content in the molten iron is 0.0008% when it leaves the station.

[0087] b. Converter smelting

[0088] The desulfurized molten iron is fed into the converter and mixed with scrap steel to form molten steel, where it undergoes dephosphorization and desiliconization. Steel is tapped when the molten steel has a sulfur content of 0.0018%, a phosphorus content of 0.02%, and a nitrogen content of 0.0016%. The scrap steel is entirely recycled non-oriented silicon steel, accounting for 15% of the total converter charge.

[0089] c.RH vacuum refining

[0090] RH vacuum recirculating degassing equipment is used to vacuum decarburize, deoxidize, alloy, and remove inclusions from molten steel after converter refining. During the RH vacuum refining process, oxygen in the converter steel is used for decarburization, followed by deoxidation with the alloying element Si. During the alloying process, Si is first added, followed by Al, and then metallic Sn or Sb is added based on the actual Si / Al ratio. Finally, a clean cycle is performed under vacuum conditions to effectively remove inclusions from the molten steel.

[0091] (2) Continuous casting

[0092] The molten steel obtained in the molten steel smelting process is continuously cast into continuous casting billets with a thickness of 220 mm using a continuous casting device. The chemical composition of the continuous casting billets is as described above. Please refer to Table 1 for details.

[0093] The continuous casting mold uses a special mold slag. Its chemical composition, by mass percentage, includes: SiO2 28-36%, MgO ≤ 5%, CaO 16-24%, Fe2O3 ≤ 5%, Al2O3 ≤ 5%, Na2O 13-15%, CaF 8-14%, Li2O 1.1-1.5%, B2O3 4.5-5.5%, TC ≤ 1.5%, and an exothermic agent 1.9-2.1%. The exothermic agent is a calcium-silicon alloy with 40% Ca and 60% Si by mass. The mold slag has a binary basicity of 0.61-0.63, a melting point of 1000±40°C, and a viscosity of 0.2±0.05 Pa·s.

[0094] During the continuous casting process, electromagnetic stirring was used in the secondary cooling zone with a stirring current of 400 A, a stirring frequency of 8 Hz, and a continuous casting speed of 1.2 ± 0.1 m / min.

[0095] (3) Hot rolling

[0096] The continuous casting slab obtained in the continuous casting process is first sent to a heating furnace for heating. The furnace entry temperature of the continuous casting slab is 580°C, the heating temperature T1 is 1130°C, and the heating time is 160-180 minutes. The continuous casting slab is then sent to a double-stand rough rolling mill for 6 rough rolling passes, specifically, 1 rough rolling pass on the first stand and then 5 rough rolling passes on the second stand. The continuous casting slab is then sent to a seven-stand finishing mill for 7 finishing rolling passes. The starting rolling temperature of the finishing rolling is 940°C, the final rolling temperature of the finishing rolling is T2=845°C, and the total reduction rate of the finishing rolling is 93%. Finally, the hot-rolled coil with a thickness of 2.0 mm is obtained, and the coiling temperature is T3=575°C.

[0097] (4) Pickling

[0098] The pickling is carried out in three stages. The pickling solution in the first stage is a mixed solution of NH4HF2+HCl, with a concentration of NH4HF2 of 80 g / L, a concentration of HCl of 155 g / L, a pickling temperature T4 of 80°C, and a pickling time t of 20s; the pickling solution in the second stage is a mixed solution of NH4HF2+HCl, with a concentration of NH4HF2 of 95 g / L, a concentration of HCl of 200 g / L, a pickling temperature T4 of 90°C, and a pickling time t of 15s; the pickling solution in the third stage is a mixed solution of H2O2+HCl, with a concentration of H2O2 of 30 g / L, a concentration of HCl of 100 g / L, a pickling temperature T4 of 95°C, and a pickling time t of 30s.

[0099] (5) Cold rolling

[0100] The hot-rolled strip after the pickling process is continuously cold-rolled using five stands to obtain a chilled coil with a thickness of 0.35 mm. The reduction rate of each pass is controlled at 25-35%, and the total reduction rate is controlled at 82.5%.

[0101] (6) Primary annealing

[0102] The chilled coils obtained from the cold rolling process are fed into an annealing furnace and subjected to high-temperature annealing in a pure nitrogen atmosphere at a temperature of 950°C for 82 seconds. This high-temperature annealing ensures full recrystallization of the coils, achieving an average grain size of 83 μm. The annealed coils are then cooled, coated, and finished to produce non-oriented silicon steel. The cooling rate is controlled to ≤10°C / s before reaching a temperature of 400-550°C.

[0103] After testing, the iron loss P of non-oriented silicon steel after the first annealing process is 1.5 / 50 , magnetic induction B 5000 , yield strength YS, and elongation are shown in Table 2.

[0104] (7) Winding

[0105] The non-oriented silicon steel obtained by the primary annealing process is stripped, the tooth groove portion is punched, and then the yoke portion is wound to obtain a high-Al non-oriented silicon steel wound core. The strain σ of the core is controlled to be 2% during the winding process.

[0106] (8) Secondary annealing

[0107] The high-Al non-oriented silicon steel wound core obtained by winding is subjected to secondary annealing in a pure N2 protective atmosphere, with the annealing temperature T6=840°C.

[0108] After testing, the iron loss P of the high Al non-oriented silicon steel wound core after the secondary annealing process is 1.5 / 50 , magnetic induction B 5000 See Table 2.

[0109] Example 2

[0110] The preparation method of high Al non-oriented silicon steel wound core comprises the following steps:

[0111] (1) Molten steel smelting

[0112] The chemical composition of the molten steel obtained by smelting is as described above, please refer to Table 1 for details.

[0113] Specifically, the molten steel smelting process includes the following steps performed in sequence:

[0114] a.KR desulfurization of molten iron

[0115] The molten iron is desulfurized in the KR desulfurization device, the slag removal rate is controlled to 98%, and the S content in the molten iron is 0.0009% when it leaves the station.

[0116] b. Converter smelting

[0117] The desulfurized molten iron is fed into the converter and mixed with scrap steel to form molten steel, where it undergoes dephosphorization and desiliconization. Steel is tapped when the molten steel has a sulfur content of 0.0016%, a phosphorus content of 0.017%, and a nitrogen content of 0.0014%. The scrap steel is entirely recycled non-oriented silicon steel, accounting for 16% of the total converter charge.

[0118] c.RH vacuum refining

[0119] RH vacuum recirculating degassing equipment is used to vacuum decarburize, deoxidize, alloy, and remove inclusions from molten steel after converter refining. During the RH vacuum refining process, oxygen in the converter steel is used for decarburization, followed by deoxidation with the alloying element Si. During the alloying process, Si is first added, followed by Al, and then metallic Sn or Sb is added based on the actual Si / Al ratio. Finally, a clean cycle is performed under vacuum conditions to effectively remove inclusions from the molten steel.

[0120] (2) Continuous casting

[0121] The molten steel obtained in the molten steel smelting process is continuously cast into continuous casting billets with a thickness of 220 mm using a continuous casting device. The chemical composition of the continuous casting billets is as described above. Please refer to Table 1 for details.

[0122] The continuous casting mold uses a special mold slag. Its chemical composition, by mass percentage, includes: SiO2 28-36%, MgO ≤ 5%, CaO 16-24%, Fe2O3 ≤ 5%, Al2O3 ≤ 5%, Na2O 13-15%, CaF 8-14%, Li2O 1.1-1.5%, B2O3 4.5-5.5%, TC ≤ 1.5%, and an exothermic agent 1.9-2.1%. The exothermic agent is a calcium-silicon alloy with 40% Ca and 60% Si by mass. The mold slag has a binary basicity of 0.61-0.63, a melting point of 1000±40°C, and a viscosity of 0.2±0.05 Pa·s.

[0123] During the continuous casting process, electromagnetic stirring was used in the secondary cooling zone with a stirring current of 400 A, a stirring frequency of 8 Hz, and a continuous casting speed of 1.2 ± 0.1 m / min.

[0124] (3) Hot rolling

[0125] The continuous casting slab obtained in the continuous casting process is first sent to a heating furnace for heating. The furnace entry temperature of the continuous casting slab is 600°C, the heating temperature T1 is 1121°C, and the heating time is 160-180 minutes. The continuous casting slab is then sent to a double-stand roughing mill for 6 roughing passes, specifically, 1 roughing pass in the first stand and then 5 roughing passes in the second stand. The continuous casting slab is then sent to a seven-stand finishing mill for 7 finishing passes. The starting rolling temperature of the finishing rolling is 950°C, the final rolling temperature of the finishing rolling is T2=834°C, and the total reduction rate of the finishing rolling is 93%. Finally, the hot-rolled coil with a thickness of 2.0 mm is obtained, and the coiling temperature is T3=561°C.

[0126] (4) Pickling

[0127] The pickling is carried out in three stages. The pickling solution in the first stage is a mixed solution of NH4HF2+HCl, with a concentration of NH4HF2 of 70 g / L, a concentration of HCl of 170 g / L, a pickling temperature T4 of 88°C, and a pickling time t of 20s; the pickling solution in the second stage is a mixed solution of NH4HF2+HCl, with a concentration of NH4HF2 of 90 g / L, a concentration of HCl of 220 g / L, a pickling temperature T4 of 92°C, and a pickling time t of 15s; the pickling solution in the third stage is a mixed solution of H2O2+HCl, with a concentration of H2O2 of 40 g / L, a concentration of HCl of 110 g / L, a pickling temperature T4 of 95°C, and a pickling time t of 35s.

[0128] (5) Cold rolling

[0129] The hot-rolled strip after the pickling process is continuously cold-rolled using five stands to obtain a chilled coil with a thickness of 0.30 mm. The reduction rate of each pass is controlled at 25-35%, and the total reduction rate is controlled at 85%.

[0130] (6) Primary annealing

[0131] The chilled coils obtained from the cold rolling process are fed into an annealing furnace and subjected to high-temperature annealing in a pure nitrogen atmosphere at a temperature of 966°C (T5) for 90 seconds. This high-temperature annealing ensures full recrystallization of the coils, with an average grain size of 90 μm. The annealed coils are then cooled, coated, and finished to produce non-oriented silicon steel. The cooling rate is controlled to ≤10°C / s before reaching a temperature of 400-550°C.

[0132] After testing, the iron loss P of non-oriented silicon steel after the first annealing process is 1.5 / 50 , magnetic induction B 5000 , yield strength YS, and elongation are shown in Table 2.

[0133] (7) Winding

[0134] The non-oriented silicon steel obtained by the primary annealing process is stripped, the tooth groove portion is punched, and then the yoke portion is wound to obtain a high-Al non-oriented silicon steel wound core. The strain σ of the core is controlled to be 5% during the winding process.

[0135] (8) Secondary annealing

[0136] The high Al non-oriented silicon steel wound core obtained by winding is subjected to secondary annealing in a pure N2 protective atmosphere, with the annealing temperature T6=900°C.

[0137] After testing, the iron loss P of the high Al non-oriented silicon steel wound core after the secondary annealing process is 1.5 / 50 , magnetic induction B 5000 See Table 2.

[0138] Example 3

[0139] The preparation method of high Al non-oriented silicon steel wound core comprises the following steps:

[0140] (1) Molten steel smelting

[0141] The chemical composition of the molten steel obtained by smelting is as described above, please refer to Table 1 for details.

[0142] Specifically, the molten steel smelting process includes the following steps performed in sequence:

[0143] a.KR desulfurization of molten iron

[0144] The molten iron is desulfurized in the KR desulfurization device, the slag removal rate is controlled to 98%, and the S content in the molten iron is 0.0008% when it leaves the station.

[0145] b. Converter smelting

[0146] The desulfurized molten iron is fed into the converter and mixed with scrap steel to form molten steel, where it undergoes dephosphorization and desiliconization. Steel is tapped when the molten steel has a sulfur content of 0.0018%, a phosphorus content of 0.02%, and a nitrogen content of 0.0016%. The scrap steel is entirely recycled non-oriented silicon steel, accounting for 12% of the total converter charge.

[0147] c.RH vacuum refining

[0148] RH vacuum recirculating degassing equipment is used to vacuum decarburize, deoxidize, alloy, and remove inclusions from molten steel after converter refining. During the RH vacuum refining process, oxygen in the converter steel is used for decarburization, followed by deoxidation with the alloying element Si. During the alloying process, Si is first added, followed by Al, and then metallic Sn or Sb is added based on the actual Si / Al ratio. Finally, a clean cycle is performed under vacuum conditions to effectively remove inclusions from the molten steel.

[0149] (2) Continuous casting

[0150] The molten steel obtained in the molten steel smelting process is continuously cast into continuous casting billets with a thickness of 220 mm using a continuous casting device. The chemical composition of the continuous casting billets is as described above. Please refer to Table 1 for details.

[0151] The continuous casting mold uses a special mold slag. Its chemical composition, by mass percentage, includes: SiO2 28-36%, MgO ≤ 5%, CaO 16-24%, Fe2O3 ≤ 5%, Al2O3 ≤ 5%, Na2O 13-15%, CaF 8-14%, Li2O 1.1-1.5%, B2O3 4.5-5.5%, TC ≤ 1.5%, and an exothermic agent 1.9-2.1%. The exothermic agent is a calcium-silicon alloy with 40% Ca and 60% Si by mass. The mold slag has a binary basicity of 0.61-0.63, a melting point of 1000±40°C, and a viscosity of 0.2±0.05 Pa·s.

[0152] During the continuous casting process, electromagnetic stirring was used in the secondary cooling zone with a stirring current of 400 A, a stirring frequency of 8 Hz, and a continuous casting speed of 1.2 ± 0.1 m / min.

[0153] (3) Hot rolling

[0154] The continuous casting slab obtained in the continuous casting process is first sent to a heating furnace for heating. The furnace entry temperature of the continuous casting slab is 500°C, the heating temperature T1 is 1110°C, and the heating time is 160-180 minutes. The continuous casting slab is then sent to a double-stand roughing mill for 6 roughing passes, specifically, 1 roughing pass in the first stand and then 5 roughing passes in the second stand. The continuous casting slab is then sent to a seven-stand finishing mill for 7 finishing passes. The starting rolling temperature of the finishing rolling is 930°C, the final rolling temperature of the finishing rolling is T2=820°C, and the total reduction rate of the finishing rolling is 94%. Finally, the hot-rolled coil with a thickness of 1.8 mm is obtained, and the coiling temperature is T3=547°C.

[0155] (4) Pickling

[0156] The pickling is carried out in three stages. The pickling solution in the first stage is a mixed solution of NH4HF2+HCl, with a concentration of NH4HF2 of 60 g / L, a concentration of HCl of 190 g / L, a pickling temperature T4 of 95°C, and a pickling time t of 18s; the pickling solution in the second stage is a mixed solution of NH4HF2+HCl, with a concentration of NH4HF2 of 80 g / L, a concentration of HCl of 240 g / L, a pickling temperature T4 of 90°C, and a pickling time t of 15s; the pickling solution in the third stage is a mixed solution of H2O2+HCl, with a concentration of H2O2 of 50 g / L, a concentration of HCl of 120 g / L, a pickling temperature T4 of 95°C, and a pickling time t of 38s.

[0157] (5) Cold rolling

[0158] The hot-rolled strip after the pickling process is continuously cold-rolled using five stands to obtain a chilled coil with a thickness of 0.30 mm. The reduction rate of each pass is controlled at 25-35%, and the total reduction rate is controlled at 83.3%.

[0159] (6) Primary annealing

[0160] The chilled coils obtained from the cold rolling process are fed into an annealing furnace and subjected to high-temperature annealing in a pure nitrogen atmosphere at a temperature of 985°C for 100 seconds. This high-temperature annealing ensures full recrystallization of the coils, with an average grain size of 70 μm. The annealed coils are then cooled, coated, and finished to produce non-oriented silicon steel. The cooling rate is controlled to ≤10°C / s before reaching a temperature of 400-550°C.

[0161] After testing, the iron loss P of non-oriented silicon steel after the first annealing process is 1.5 / 50 , magnetic induction B 5000 , yield strength YS, and elongation are shown in Table 2.

[0162] (7) Winding

[0163] The non-oriented silicon steel obtained by the primary annealing process is stripped, the tooth groove portion is punched, and then the yoke portion is wound to obtain a high-Al non-oriented silicon steel wound core. The strain σ of the core is controlled to be 8% during the winding process.

[0164] (8) Secondary annealing

[0165] The high Al non-oriented silicon steel wound core obtained by winding is subjected to secondary annealing in a pure N2 protective atmosphere, with the annealing temperature T6=960°C.

[0166] After testing, the iron loss P of the high Al non-oriented silicon steel wound core after the secondary annealing process is 1.5 / 50 , magnetic induction B 5000 See Table 2.

[0167] Table 2

[0168] In addition, the surface quality of the non-oriented silicon steels of Examples 1 to 3 are all qualified, without defects such as surface blackening, and no cracking occurs during the preparation of the wound core. When used in hub motors, the electromagnetic properties of the motors are all qualified.

[0169] It should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method 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 method can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0170] The detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a high-Al non-oriented silicon steel wound core, characterized in that: It includes the following processes: molten steel smelting, continuous casting, hot rolling, pickling, cold rolling, primary annealing, coiling and secondary annealing; In the molten steel smelting process, the chemical composition of the molten steel finally obtained by smelting includes, by mass percentage, C≤0.0025%, Si1.0-1.5%, Al1.0-2.0%, Mn 0.2-0.4%, Nb≤0.002%, V≤0.002%, Ti≤0.002%, Ni≤0.03%, Cr≤0.03%, Cu≤0.01%, N≤0.002%, P 0.015-0.020%, S≤0.0015%, and Sn or Sb, and the rest is Fe and unavoidable impurities, wherein Sn=0.01×Si+0.04×Al, Sb=0.01×Si+0.04×Al, and Al / Si=1.0-1.4, C+S+O+N≤0.007%; In the hot rolling process, the continuous casting billet obtained in the continuous casting process is sequentially heated, rough rolled, finished rolled and coiled to obtain a hot rolled coil, the heating temperature T1=1160-20×[Si]-10×[Al], the heating time is 160-180min, the start rolling temperature of the finishing rolling is 910-960°C, the final rolling temperature of the finishing rolling is T2=880-20×[Si]-15×[Al], and the coiling temperature is T3=600+5×[Si]-30×[Al]; In the pickling process, pickling is performed in three stages. The pickling solution of the first stage is a mixed solution of NH4HF2+HCl, the concentration of NH4HF2 is 60-80 g / L, and the concentration of HCl is 150-200 g / L; the pickling solution of the second stage is a mixed solution of NH4HF2+HCl, the concentration of NH4HF2 is 80-100 g / L, and the concentration of HCl is 200-250 g / L; the pickling solution of the third stage is a mixed solution of H2O2+HCl, the concentration of H2O2 is 30-50 g / L, and the concentration of HCl is 100-120 g / L; the pickling time t and the pickling temperature T4 of each of the three stages correspond to each other and satisfy: Where, B = -0.01 × [NH4HF2] 2 +2×[HCl]-75, the unit of t is s, the unit of temperature is ℃; [Si] represents the mass percentage of Si element in the continuous casting billet, [Al] represents the mass percentage of Al element in the continuous casting billet; [NH4HF2] represents the concentration value of NH4HF2 in the mixed solution, and [HCl] represents the concentration value of HCl in the mixed solution.

2. The method for preparing a high Al non-oriented silicon steel wound core according to claim 1, characterized in that: In the primary annealing process, the cold hard coil obtained in the cold rolling process is subjected to high-temperature annealing under a pure N2 protective atmosphere, the annealing temperature T5=900+30×[Si]+20×[Al], the unit is ° C, the annealing time is 80-100s, and the steel coil after high-temperature annealing is controlled to complete sufficient recrystallization, and the average grain size is 70-90μm; wherein [Si] represents the mass percentage of Si element in the continuous casting billet, and [Al] represents the mass percentage of Al element in the continuous casting billet.

3. The method for preparing a high Al non-oriented silicon steel wound core according to claim 2, characterized in that: In the primary annealing process, the steel coil after high temperature annealing is cooled, coated and finished to obtain non-oriented silicon steel, and the cooling rate before cooling to 400-550°C is controlled to be ≤10°C / s.

4. The method for preparing a high Al non-oriented silicon steel wound core according to claim 3, characterized in that: The iron loss P of the non-oriented silicon steel obtained by the primary annealing process is 1.5 / 50 ≤3.0W / kg, magnetic induction B 5000 ≥1.67T, yield strength YS is 200~260MPa, elongation ≥25%.

5. The method for preparing a high Al non-oriented silicon steel wound core according to claim 1, characterized in that: The secondary annealing process is carried out under a pure N2 protective atmosphere, and the annealing temperature T6=800+2000×σ, in units of °C, where σ is the strain of the iron core during the winding process.

6. The method for preparing a high Al non-oriented silicon steel wound core according to claim 1, characterized in that: In the winding process, the non-oriented silicon steel obtained in the primary annealing process is divided into strips, the tooth groove part is punched, and then the yoke part is wound to obtain a high-Al non-oriented silicon steel wound core. The strain σ of the core is controlled to be 2-8% during the winding process.

7. The method for preparing a high Al non-oriented silicon steel wound core according to claim 1, characterized in that: In the hot rolling process, the continuous casting billet is sent to a heating furnace for heating, the furnace entry temperature of the continuous casting billet is 500-600°C, the rough rolling is performed by a double stand for 6 passes, including 1 rough rolling performed on the first stand and 5 rough rolling performed on the second stand, the finishing rolling is performed by a seven-stand finishing mill for 7 passes, the total reduction rate of the finishing rolling is controlled to be 93-94%, and the thickness of the hot rolled coil is 1.8-2.0 mm.

8. The method for preparing a high Al non-oriented silicon steel wound core according to claim 1, characterized in that: In the cold rolling process, a five-stand cold rolling mill is used to continuously cold roll the hot-rolled strip after the pickling process to obtain a cold hardened coil with a thickness of 0.3 to 0.4 mm, and the reduction rate of each pass is controlled to be 25 to 35%, and the total reduction rate is controlled to be 80 to 90%.

9. A high Al non-oriented silicon steel wound core, characterized in that: The high-Al non-oriented silicon steel wound core is prepared by the method for preparing the high-Al non-oriented silicon steel wound core as described in any one of claims 1 to 8.

10. The high Al non-oriented silicon steel wound core according to claim 9, characterized in that: Its iron loss P 1.5 / 50 ≤2.5W / kg, magnetic induction B 5000 ≥1.72T.

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