Silicon steel material, motor iron core, preparation method of motor iron core and motor

Abstract

The invention provides a silicon steel material, a motor iron core, a preparation method of the motor iron core and a motor, and relates to the technical field of silicon steel materials, and the silicon steel material comprises the following chemical components in percentage by mass: 2.4-2.6 wt% of Si, 0.8-1.0 wt% of Al, 0.2-0.3 wt% of Mn and the balance of Fe and inevitable impurities. The mass percent of Si is designed to be 2.4%-2.6%, silicon steel grains can be promoted to grow due to the high Si content, if the grains are large, grain boundaries in unit volume are reduced, obstruction of magnetic domain wall movement is reduced, and then magnetic hysteresis loss can be reduced; however, the Si content is too high, the hardness of the silicon steel sheet is improved, and the material forming difficulty is increased; as a non-magnetic element, silicon can reduce the content of the magnetic element Fe after being added, so that the saturation magnetic induction of the silicon steel is reduced; in addition, due to the fact that the content of Si is too high, brittle intermetallic compounds (such as Fe-Si ordered phases) can be easily formed, machining performance can be deteriorated, cold rolling forming is difficult, cracks are easily generated, and the actual use difficulty is large.

Description

Technical Field

[0001] The present invention belongs to the technical field of silicon steel materials, and in particular relates to a silicon steel material, a motor core and a preparation method thereof, and a motor. Background Art

[0002] At present, the stator and rotor cores of electric motors are directly punched (stamped) and stacked using silicon steel plates. During the lamination process of the cores, the eddy current loss of silicon steel is proportional to the square of its plate thickness. Therefore, thinned silicon steel sheets need to be stacked together when manufacturing the cores. In order to effectively confine the eddy currents to each silicon steel lamination, it is usually necessary to apply a surface coating with insulating properties to the surface of the silicon steel sheets to insulate the silicon steel sheets from each other. This silicon steel insulating coating is generally applied during the silicon steel production process. However, stamping can cause stress concentration at the edge of the stator core and damage to the edge grains, which leads to increased iron loss in the stator core, thereby reducing the efficiency of the motor.

[0003] To address the common problem of increased stator core iron loss caused by stress concentration and grain damage at the edges of the stator core, the stamped core is generally subjected to an overall annealing heat treatment (heat treatment temperature of 760°C ± 20°C) and a bluing treatment. Annealing eliminates surface stress, isotropy, and residual magnetism, reducing the core's input power. Bluing, on the other hand, forms a dense oxide film on the silicon steel surface at high temperatures, thereby increasing its insulation resistance and reducing eddy current losses in the motor. Furthermore, the bluing process also relieves stress, and a good oxide film provides corrosion and rust resistance.

[0004] However, the iron core obtained after annealing heat treatment and bluing treatment has the following problems: (1) The grain size is small and the hysteresis loss is large, so the iron loss of the iron core is large; (2) The high-temperature annealing heat treatment causes local decomposition and damage of the organic insulating coating on the surface of the silicon steel, and small cracks are formed in the coating. In addition, since DX gas contains CO2, the oxygen content on the surface of the silicon steel increases after annealing heat treatment, and the bluing treatment is carried out in an oxidizing atmosphere. The diffusion of oxygen atoms in the cracks intensifies the crack expansion, resulting in large-scale damage to the insulating coating on the surface of the silicon steel, causing insulation failure on the silicon steel surface and reduced insulation resistance. Summary of the Invention

[0005] Therefore, the present invention provides a silicon steel material, a motor iron core and a preparation method thereof, and a motor, which can solve the problem in the prior art that the iron core grain size is small and causes large iron loss.

[0006] In order to solve the above problems, the present invention provides a silicon steel material, wherein the chemical composition of the silicon steel material comprises, by mass percentage, Si 2.4-2.6 wt%, Al 0.8-1.0 wt%, Mn 0.2-0.3 wt%, and the balance is Fe and unavoidable impurities.

[0007] Furthermore, in the silicon steel material: the mass percentage of Al is a, and the sum of the mass percentages of Al and Si is b; wherein a / b=0.25-0.3; and / or

[0008] The sum of the mass percentages of Al, Si and Mn is 3.6-3.8 wt %; preferably, the sum of the mass percentages of Al and Si is 3.3-3.5 wt %.

[0009] In another aspect, the present invention provides a method for preparing a motor core, comprising the following steps:

[0010] The silicon steel sheets are sequentially subjected to core forming and annealing treatment to obtain a motor core; wherein the silicon steel sheets are made of any of the silicon steel materials described above.

[0011] Furthermore, before the step of forming the iron core, the method further includes: coating the silicon steel sheet to form an insulating coating on the surface of the silicon steel sheet; wherein the thickness of the insulating coating on the surface of the silicon steel sheet is 0.8 to 1.5 μm;

[0012] The insulating coating is a semi-organic magnesium chromate coating; the chemical composition of the semi-organic magnesium chromate coating includes, by mass percentage, Mg 3-3.5wt%, Al 1-1.5wt%.

[0013] Furthermore, the steps of forming and manufacturing the iron core include: stamping, laminating and consolidating the silicon steel sheets in sequence;

[0014] Wherein, a white sheet is obtained after stamping; the grain size of the white sheet is 105-115 μm; and the yield strength of the white sheet is 350-360 MPa.

[0015] Furthermore, the white sheet has two buckle points; preferably, the buckle points are circular; the diameter ΦA of the circular buckle points is 1.9-2.1 mm, and the distance H1 between the center of the circular buckle points and the outer diameter of the white sheet is 1.5-2 mm.

[0016] Furthermore, after the step of forming the iron core, the method further comprises: polishing the formed iron core;

[0017] Preferably, the roughness of the inner diameter of the iron core after polishing is Ra<0.4.

[0018] Furthermore, in the annealing step, the annealing temperature is 800-840° C. and the annealing time is 30-60 min.

[0019] Furthermore, the coverage area of ​​the surface insulation coating of the motor core is ≥50%;

[0020] Preferably, the coverage area of ​​the surface insulating coating of the motor core is obtained by the following method: immersing the motor core in a CuSO4 solution, and then obtaining the area of ​​the surface insulating coating of the motor core by metallographic second phase area calculation method; further preferably, the mass percentage concentration of the CuSO4 solution is 3%.

[0021] On the other hand, the present invention provides a motor core, wherein the grain size of the motor core is 135-145 μm; the yield strength of the motor core is 360-370 MPa; preferably, the motor core is obtained by any of the preparation methods described above.

[0022] In another aspect, the present invention provides a motor comprising the motor core described above.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] 1. In one aspect, the present invention provides a silicon steel material, wherein the chemical composition of the silicon steel material comprises, in mass percentage, 2.4-2.6% Si, 0.8-1.0% Al, 0.2-0.3% Mn, and the balance being Fe and unavoidable impurities. By designing the Si mass percentage to be 2.4-2.6%, the present invention promotes grain growth in the silicon steel. Larger grains result in fewer grain boundaries per unit volume, less obstruction to magnetic domain wall movement, and thus contributes to reduced hysteresis loss. However, if the Si content is too high, the hardness of the silicon steel sheet increases, making the material more difficult to form. Furthermore, as a non-magnetic element, the addition of silicon reduces the Fe content, which is a magnetic element, thereby reducing the saturation magnetic induction of the silicon steel. Furthermore, if the Si content is too high, brittle intermetallic compounds (such as an ordered Fe-Si phase) may form, which may deteriorate processing performance, make cold rolling difficult, and easily generate cracks, making practical use difficult.

[0025] 2. In another aspect, the present invention provides a method for preparing a motor core, comprising the following steps: sequentially forming and annealing silicon steel sheets to obtain the motor core; wherein the silicon steel sheets are made of the aforementioned silicon steel material; and the annealing is performed in a vacuum atmosphere. Compared to conventional reducing or nitrogen atmospheres, the annealing process of the present invention utilizes a vacuum atmosphere, which does not cause carburization or nitriding problems, resulting in improved silicon steel surface quality. Furthermore, the vacuum atmosphere prevents the silicon steel surface from oxidizing and rusting, thereby preventing the rust layer from aging the insulating protective layer on the surface of the silicon steel sheet.

[0026] 3. Furthermore, the annealing temperature is set at 800-840°C to promote grain growth, reduce the grain boundary area, reduce the energy required for magnetic domain rotation, reduce hysteresis loss, and thus reduce iron loss. When the annealing temperature is 660-780°C, the silicon steel mainly undergoes grain recovery and recrystallization. At this time, the annealing heat treatment is mainly to remove the stress generated after the silicon steel sheet is punched and repair the silicon steel grains damaged after stamping to their original state, but no significant grain growth will occur; however, when the temperature is too high, some grains grow abnormally, resulting in poor uniformity between grains and no further reduction in hysteresis loss.

[0027] 4. On the other hand, the present invention provides a motor core, which is obtained by the above-mentioned preparation method, and each core punching sheet in the motor core has two buckle points; fewer buckle points can, on the one hand, avoid the influence of the buckle points on the damage to the magnetic circuit of the stator core, and on the other hand, effectively reduce the problem of silicon steel sticking after heat treatment, thereby further reducing eddy current loss and improving motor efficiency. Furthermore, the buckle point shape is changed from square to circular, and the circular shape has relatively smooth edges, small clamping force and small damage to the silicon steel edge, thus further reducing the impact on the stator magnetic circuit. The reduction in the number of buckle points and the shape of the circular buckle points will reduce the clamping force between the silicon steel sheets, thereby affecting the stability of the stator. Therefore, the present invention is designed to reduce the buckle points while requiring laser welding of the core edge to enhance the stability of the stator core. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. The drawings described below are merely exemplary. Those skilled in the art can, without inventive effort, derive other implementation drawings based on the provided drawings.

[0029] Figure 1 It is a structural schematic diagram of the stator core of the present invention;

[0030] Figure 2 This is a microscopic morphology diagram of the insulating coating on the surface of the silicon steel of the present invention after being corroded by copper sulfate;

[0031] Figure 3 This is a microscopic morphology of the insulating coating on the surface of existing silicon steel corroded by copper sulfate. DETAILED DESCRIPTION

[0032] To further illustrate the technical means and effects employed by the present invention to achieve its intended objectives, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention is provided in conjunction with the accompanying drawings and preferred embodiments. In the following description, different references to "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0033] The present invention optimizes the alloying element composition and heat treatment scheme design to effectively control the grain size range of the silicon steel after heat treatment and the area content of the remaining insulating coating. By combining the optimal values ​​of the two material indicators, the heat treatment process can be maximized, significantly reducing the iron loss of the iron core and effectively improving the motor efficiency of the heat-treated iron core. The stator iron core motor efficiency can reach over 93%. At the same time, the bluing process in the heat treatment can be eliminated, saving process costs. The specific scheme is as follows:

[0034] On the one hand, the present invention provides a silicon steel material, wherein the chemical composition of the silicon steel material includes, in terms of mass percentage, 2.4-2.6 wt% Si, 0.8-1.0 wt% Al, 0.2-0.3 wt% Mn, and the balance being Fe and unavoidable impurities; wherein the mass percentage of Al is a, and the sum of the mass percentages of Al and Si is b; wherein a / b=0.25-0.3; the sum of the mass percentages of Al, Si, and Mn is 3.6-3.8 wt%; preferably, the sum of the mass percentages of Al and Si is 3.3-3.5 wt%.

[0035] In another aspect, the present invention provides a method for preparing a motor core, comprising the following steps:

[0036] The silicon steel sheets are sequentially subjected to iron core forming and annealing treatment to obtain the motor iron core; the annealing treatment is carried out in a vacuum atmosphere.

[0037] The steps of forming and manufacturing the iron core include: stamping, laminating and consolidating the silicon steel sheets in sequence; obtaining white sheets after stamping; the grain size of the white sheets is 105-115 μm; the yield strength of the white sheets is 350-360 MPa. Consolidation is carried out by welding. The white sheet has two buckling points; the buckling points are circular; the diameter ΦA of the circular buckling points is 1.9-2.1 mm, and the distance H1 between the center of the circular buckling point and the outer diameter of the stator (outer diameter of the white sheet) is 1.5-2 mm. The obtained iron core structure has 9 slots and 2 buckling points, such as Figure 1 shown.

[0038] The annealing temperature is 800-840°C, and the annealing time is 30-60 minutes. Within this temperature range and time, significant grain growth occurs, grain boundary area decreases, the energy required for magnetic domain rotation decreases, hysteresis losses are reduced, and iron losses are reduced. At annealing temperatures of 660-780°C, silicon steel primarily undergoes grain recovery and recrystallization. Annealing at this temperature primarily removes stress generated by punching and repairs damaged silicon steel grains to their original state, but does not significantly increase grain growth. However, at temperatures too high, some grains grow abnormally, resulting in poor grain uniformity and no further reduction in hysteresis losses. Existing silicon steel insulating coatings have a temperature resistance of approximately 750°C. As the annealing temperature increases, the damage rate of the insulating coating gradually increases, starting from the initial 100% coverage and gradually decreasing. Higher temperatures and longer annealing times increase the damage rate. There is an optimal balance between the amount of insulating coating remaining after heat treatment and the silicon steel grain size. By controlling the heat treatment time to 30-60 minutes, at least half of the insulating coating remains when the grains grow to the appropriate range. Before annealing, the insulating coating on the surface of the silicon steel sheet covers 100%. Due to the high-temperature heat treatment, a portion of the insulating coating evaporates. By controlling the temperature and time of the annealing heat treatment, the insulating coating after annealing is at least half of the pre-annealing coverage. If the insulating coating is less than half after annealing, the exposed area of ​​the silicon steel sheet increases due to the lack of coating, which can cause conduction between the sheets, thereby reducing the insulation resistance of the core.

[0039] After annealing, the grain size of the motor core is 135-145μm; the yield strength of the motor core is 360-370MPa; compared with the grain size of white silicon steel, it increases by about 30μm. After the grain size increases, the grain boundary per unit area decreases, the energy required for magnetic domain movement is less, and the iron loss is reduced.

[0040] Compared with traditional reducing atmosphere or nitrogen atmosphere, annealing treatment uses vacuum atmosphere, which will not cause carburizing or nitriding problems, and the surface quality of silicon steel is better. In addition, vacuum atmosphere can ensure that the surface of silicon steel is not easily oxidized and rusted, thereby preventing the rust layer from aging the insulating protective layer on the surface of the silicon steel sheet.

[0041] Among them, the silicon steel sheet adopts the above-mentioned silicon steel material. On the one hand, the solid solution effect of silicon and iron in the silicon steel sheet will inhibit the diffusion of carbon in the steel and the formation of carbides, so the pinning effect of carbides on grain boundaries is weakened, and the resistance to grain boundary migration during annealing is reduced, which can promote grain growth. On the other hand, the addition of silicon increases the recrystallization temperature of the material, causing the grains to recrystallize at a higher temperature. At this time, the grain boundary migration ability is enhanced, which is conducive to the formation of larger grains. Therefore, the mass percentage of Si in this application is designed to be 2.4% to 2.6%. A higher Si content can promote the growth of silicon steel grains. Larger grains have fewer grain boundaries per unit volume, which reduces the resistance to magnetic domain wall migration, thereby helping to reduce hysteresis loss. However, if the Si content is too high, the hardness of the silicon steel sheet will increase, and the difficulty of material forming will increase. Moreover, as a non-magnetic element, the addition of silicon will reduce the content of the magnetic element Fe, thereby causing the saturation magnetic induction of the silicon steel to decrease. In addition, if the Si content is too high, it will easily form brittle intermetallic compounds (such as Fe-Si ordered phase), which will deteriorate the processing performance, make cold rolling difficult, and easily generate cracks, making it difficult to use in practice. The addition of aluminum easily combines with silicon atoms to form an Al-Si solid solution, inhibiting silicon segregation and the continuous precipitation of brittle phases, thereby improving the formability of the punching sheet. At the same time, aluminum preferentially reacts with impurity elements such as oxygen and nitrogen to form stable Al2O3 and AlN compounds, reducing impurity segregation at grain boundaries. However, Al is also a non-magnetic element, and adding too much will lead to a decrease in magnetic induction.

[0042] In some embodiments, before the step of forming and manufacturing the iron core, the step further includes: coating the silicon steel sheet to form an insulating coating on the surface of the silicon steel sheet; wherein the thickness of the insulating coating on the surface of the silicon steel sheet is 0.8 to 1.5 μm; the insulating coating adopts a semi-organic magnesium chromate coating; in terms of mass percentage, the chemical composition of the semi-organic magnesium chromate coating includes: Mg3 to 3.5wt%, Al1 to 1.5wt%, and the balance is chromate ions and organic polymers.

[0043] Among them, semi-organic magnesium chromate coating refers to a composite coating with magnesium chromate (such as MgCrO4) and aluminum chromate as inorganic core components, which are formed by chemical bonding or physical blending with organic polymers. It has both the corrosion resistance of inorganic coatings and the adhesion of organic coatings.

[0044] The thinner the insulating coating is, the more likely it is that the coating will fail after heat treatment, which will cause the iron core silicon steel sheets to stick together and increase eddy current losses. However, if the insulating coating is too thick, the stacking coefficient of the iron core will be reduced, resulting in low motor efficiency. Furthermore, the insulating coating uses a semi-organic magnesium chromate coating. When the magnesium content is less than <3%, vacancy defects are easily formed in the lattice, causing the coating porosity to increase to >8%, thereby causing the insulation resistance to decrease. Excessive magnesium >3.5 will cause lattice distortion, generate secondary phases (such as MgO), reduce the homogeneity of the coating, and easily form Mg(OH)2 sparse Loose layer, accelerate the expansion of pitting corrosion, and thus reduce the temperature resistance of the coating after heat treatment; Al is added to the insulating coating, aluminum replaces part of the magnesium or chromium sites in the spinel structure of magnesium chromate (MgCr2O4), forming a (Mg,Al)Cr2O4 solid solution, reducing the lattice vacancy defect density, and reducing the porosity of the coating to <5% (usually 6%-8% when no aluminum is added), thereby increasing the insulation resistivity. Aluminum is oxidized on the surface of the coating to form an Al2O3 film, which forms a Cr / Al composite passivation layer with magnesium chromate, which can improve the corrosion resistance and temperature resistance of the insulating coating.

[0045] At present, the means of detecting the insulating coating after heat treatment in compressor and electrical steel manufacturers are mainly experience and visual inspection, which are prone to errors. In the present invention, the coverage area of ​​the surface insulating coating of the motor core is detected and confirmed by the copper sulfate corrosion method combined with the metallographic second phase area. The specific steps are as follows: soak the motor core in CuSO4 solution for 3 minutes, and then obtain the area of ​​the insulating coating on the surface of the motor core by the metallographic second phase area calculation method; further preferably, the mass percentage concentration of the CuSO4 solution is 3%. The raw materials for the above detection are: CuSO4+Fe→FeSO4+Cu substitution reaction. If the insulating coating on the surface of the silicon steel is damaged, the silicon steel sheet is placed in the CuSO4 solution, and the exposed iron position on the surface will react with CuSO4, thereby precipitating copper. As Figure 2 As shown, under the metallographic microscope, the insulating coating is black and the location of copper precipitation is yellow. With the help of the metallographic second phase area calculation method, the area of ​​the insulating coating can be calculated.

[0046] In some embodiments, after the core forming step, the formed core is polished; after polishing, the core inner diameter roughness Ra is less than 0.4. Polishing can remove burrs and chamfer corners, effectively improving the uniformity of the stator and rotor air gaps, ensuring smoother motor operation. Furthermore, the stator and rotor design gap is reduced from the traditional 50-wire to 45-wire.

[0047] Compared with the prior art, the present application has fewer buckling points. On the one hand, it can avoid the influence of buckling points on the damage to the magnetic circuit of the stator core. On the other hand, it can effectively reduce the problem of silicon steel sticking after heat treatment, thereby further reducing eddy current loss and improving motor efficiency. Furthermore, the shape of the buckling point is changed from square to circular. The edge of the circular shape is relatively smooth, and the clamping force is small, which causes less damage to the edge of the silicon steel. Therefore, the impact on the stator magnetic circuit can be further reduced. The reduction in the number of buckling points and the shape of the circular buckling points will reduce the clamping force between the silicon steel sheets, thereby affecting the stability of the stator. Therefore, the design of the present invention requires laser welding of the core edge while reducing the buckling points, so as to enhance the stability of the stator core. If the buckle point diameter is too small, the clamping force is too small, and the core is easy to loosen; if the buckle point diameter is too large, the damage area of ​​the silicon steel increases, and the influence on the stator magnetic circuit is aggravated.

[0048] On the other hand, the present invention provides a motor core obtained by any of the above preparation methods, wherein the grain size of the motor core is 135-145 μm; and the yield strength of the motor core is 360-370 MPa.

[0049] In another aspect, the present invention provides a motor comprising the motor core described above.

[0050] The present invention is further described below with reference to specific examples and comparative examples.

[0051] Example 1

[0052] This embodiment provides a method for preparing a motor core, comprising the following steps:

[0053] The silicon steel sheets are sequentially subjected to coating, stamping, lamination, welding and annealing treatment to obtain a motor core; wherein the annealing treatment is carried out under a vacuum atmosphere.

[0054] The chemical composition of the silicon steel sheet, in mass percentage, includes: Si 2.5wt%, Al 0.9wt%, Mn 0.3wt%, with the remainder being Fe and inevitable impurities; a white sheet is obtained after stamping; the grain size of the white sheet is 114μm; the white sheet has 9 grooves and 2 buckle points; the annealing temperature is 820°C; the annealing time is 30 minutes; the thickness of the insulating coating before annealing is 1.2μm; and the height of the motor core is 35mm.

[0055] Example 2

[0056] This embodiment provides a method for preparing a motor core, comprising the following steps:

[0057] The silicon steel sheets are sequentially subjected to coating, stamping, lamination, welding and annealing treatment to obtain a motor core; wherein the annealing treatment is carried out under a vacuum atmosphere.

[0058] The chemical composition of the silicon steel sheet, in mass percentage, includes: Si 2.5wt%, Al 0.9wt%, Mn 0.3wt%, with the remainder being Fe and inevitable impurities; a white sheet is obtained after stamping; the grain size of the white sheet is 114μm; the white sheet has 9 grooves and 2 buckle points; the annealing temperature is 820°C; the annealing time is 30 minutes; the thickness of the insulating coating before annealing is 0.7μm; and the height of the motor core is 35mm.

[0059] The above embodiments are preferred embodiments of the present invention.

[0060] Example 3

[0061] This embodiment provides a method for preparing a motor core, comprising the following steps:

[0062] The silicon steel sheets are sequentially subjected to coating, stamping, lamination, welding and annealing treatment to obtain a motor core; wherein the annealing treatment is carried out under a vacuum atmosphere.

[0063] The chemical composition of the silicon steel sheet, in percentage by mass, includes: Si 2.5wt%, Al 0.9wt%, Mn 0.3wt%, with the remainder being Fe and inevitable impurities; a white sheet is obtained after stamping; the grain size of the white sheet is 114 μm; the white sheet has 9 grooves and 2 buckle points; the annealing temperature is 820° C.; the annealing time is 30 minutes; the thickness of the insulating coating before annealing is 1.6 μm; and the height of the motor core is 35 mm.

[0064] Comparative Example 1

[0065] This comparative example provides a method for preparing a motor core, comprising the following steps:

[0066] 35W300 grade silicon steel is subjected to core forming, annealing and bluing treatment in sequence to obtain a motor core; wherein, annealing adopts DX reducing protective atmosphere.

[0067] Among them, the chemical composition of the silicon steel sheet, calculated in mass percentage, includes: Si 2.0~2.3wt%, Al 0.3~0.9wt%, Mn 0.2~0.3wt%, and the balance is Fe and inevitable impurities; the iron core is formed and manufactured using stamping + buckle point integrated molding to obtain a white sheet; the grain size of the white sheet is 108μm; the white sheet has 9 grooves and 9 buckle points; the annealing temperature is 780℃; the annealing time is 30min; the thickness of the insulating coating before annealing is 0.5μm; and the height of the motor core is 35mm.

[0068] Comparative Example 2

[0069] This comparative example provides a method for preparing a motor core, comprising the following steps:

[0070] 35W300 grade silicon steel is subjected to core forming, annealing and bluing treatment in sequence to obtain a motor core; wherein, annealing adopts DX reducing protective atmosphere.

[0071] The chemical composition of the silicon steel sheet, in terms of mass percentage, includes: Si2.0-2.3wt%, Al0.3-0.9wt%, and Mn0.2-0.3wt%. The core is formed by stamping and buckling to obtain a white sheet. The grain size of the white sheet is 115μm. The white sheet has 9 grooves and 9 buckles. The annealing temperature is 820℃. The annealing time is 30min. The thickness of the insulating coating before annealing is 0.5μm. The height of the motor core is 35mm. This comparative example uses the micromorphology of the insulating coating on the surface of the silicon steel after copper sulfate corrosion. Figure 3 As shown in the figure, the residual insulating coating is significantly less. This is due to the localized decomposition and damage of the organic insulating coating on the silicon steel surface during the high-temperature annealing process, resulting in small cracks in the coating. Furthermore, due to the presence of CO₂ in DX atmosphere, the oxygen content on the silicon steel surface increases after stress relief annealing and bluing in the DX atmosphere. During the bluing process, the diffusion of oxygen atoms in the cracks in the oxidizing atmosphere exacerbates crack expansion, leading to extensive damage to the coating.

[0072] Comparative Example 3

[0073] This comparative example provides a method for preparing a motor core, comprising the following steps:

[0074] 35W300 grade silicon steel is subjected to core forming, annealing and bluing treatment in sequence to obtain a motor core; wherein, annealing adopts DX reducing protective atmosphere.

[0075] Among them, the chemical composition of the silicon steel sheet, calculated in mass percentage, includes: Si 2.0~2.3wt%, Al 0.3~0.9wt%, Mn 0.2~0.3wt%; the iron core is formed and manufactured by stamping + buckling point integrated molding to obtain a white sheet; the grain size of the white sheet is 110μm; the white sheet has 9 grooves and 9 buckling points; the annealing temperature is 850℃; the annealing time is 30 minutes; the thickness of the insulating coating before annealing is 0.5μm; the height of the motor core is 35mm.

[0076] Comparative Example 4

[0077] This comparative example provides a method for preparing a motor core, comprising the following steps:

[0078] The silicon steel sheets are sequentially subjected to stamping, lamination, welding and annealing treatment to obtain a motor core; wherein the annealing treatment is carried out under a vacuum atmosphere.

[0079] Among them, the chemical composition of the silicon steel sheet, calculated in mass percentage, includes: Si 2.5wt%, Al 0.9wt%, Mn 0.3wt%, and the balance is Fe and inevitable impurities; white sheets are obtained after stamping; the grain size of the white sheets is 113μm; the white sheets have 9 grooves and 2 buckle points; the annealing temperature is 790°C; the annealing time is 45 minutes; the thickness of the insulating coating before annealing is 1.2μm; and the height of the motor core is 35mm.

[0080] Comparative Example 5

[0081] This comparative example provides a method for preparing a motor core, comprising the following steps:

[0082] The silicon steel sheets are sequentially subjected to stamping, lamination, welding and annealing treatment to obtain a motor core; wherein the annealing treatment is carried out under a vacuum atmosphere.

[0083] The chemical composition of the silicon steel sheet, in percentage by mass, includes: Si 2.5 wt%, Al 0.9 wt%, Mn 0.3 wt%, with the remainder being Fe and unavoidable impurities; a white sheet is obtained after stamping; the grain size of the white sheet is 115 μm; the white sheet has 9 grooves and 2 buckle points; the annealing temperature is 850° C.; the annealing time is 45 minutes; the thickness of the insulating coating before annealing is 1.2 μm; and the height of the motor core is 35 mm.

[0084] Comparative Example 6

[0085] This comparative example provides a method for preparing a motor core, comprising the following steps:

[0086] The silicon steel sheets are sequentially subjected to stamping, lamination, welding and annealing treatment to obtain a motor core; wherein the annealing treatment is carried out under a vacuum atmosphere.

[0087] The chemical composition of the silicon steel sheet, in percentage by mass, includes: Si 2.0 wt%, Al 0.6 wt%, Mn 0.5 wt%, with the remainder being Fe and unavoidable impurities; a white sheet is obtained after stamping; the grain size of the white sheet is 103 μm; the white sheet has 9 grooves and 2 buckle points; the annealing temperature is 820° C.; the annealing time is 30 minutes; the thickness of the insulating coating before annealing is 1.2 μm; and the height of the motor core is 35 mm.

[0088] The motor cores obtained in the above examples and comparative examples were tested for insulation coating analysis using a copper sulfate corrosion method combined with the metallographic second-phase planimetry method. The grain size of the heat-treated cores was measured using the metallographic intercept method. The corresponding core loss was measured using an iron loss meter. Specific data are shown in Table 1. The cores were then wound into motors, and motor efficiency was tested. Specific data are shown in Table 2.

[0089] Table 1 The grain size, insulation coating and iron loss data of the motor core corresponding to different schemes

[0090]

[0091] Table 2 Motor efficiency corresponding to different schemes

[0092]

[0093] Combining Tables 1 and 2, it can be seen that Comparative Examples 1 to 3 above employ conventional methods to prepare motor cores, all using existing silicon steel material compositions and an annealing + bluing treatment. Because Comparative Examples 1-3 all employ existing low-silicon alloying elements, the grain growth effect after annealing is not significant. Furthermore, the existing annealing process is susceptible to oxidation and rusting, and the low temperature resistance of existing insulating coatings results in a lower residual insulating coating. In summary, Comparative Examples 1-3 exhibit the highest iron loss and the lowest motor efficiency.

[0094] Compared with Example 1, the annealing temperature in Comparative Example 4 is lower, and the silicon steel mainly undergoes grain recovery and recrystallization processes. At this time, the annealing heat treatment is mainly to remove the stress generated after the silicon steel punching and repair the silicon steel grains damaged after stamping to their original state, but no significant grain growth will occur, so the iron loss is larger and the corresponding motor efficiency is lower.

[0095] Compared with Example 1, the annealing temperature in Comparative Example 5 is higher, the insulating layer is destroyed by the high temperature, and the residual amount is smaller. Due to the lack of coating, the exposed area of ​​the silicon steel sheet increases, which will cause conduction between the sheets, thereby reducing the insulation resistance of the iron core, and the corresponding motor efficiency is lower.

[0096] Compared with Example 1, the silicon steel material in Comparative Example 6 has lower silicon and aluminum contents and higher manganese content. Silicon and aluminum are the main elements that promote grain growth in silicon steel, and their alloying element contents are relatively low. The effect of alloying elements on the grain growth of silicon steel during heat treatment is significantly reduced. Therefore, although the same annealing process as that in Example 1 is adopted, the grain size of the silicon steel is smaller after annealing, so the iron loss is reduced, and the corresponding motor efficiency is lower.

[0097] It is easy for those skilled in the art to understand that, under the premise of no conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0098] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention. The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art may make various improvements and variations without departing from the technical principles of the present invention, and such improvements and variations shall also be considered within the scope of protection of the present invention.

Claims

1. A silicon steel material, characterized in that: Calculated in mass percentage, the chemical composition of the silicon steel material includes: Si 2.4-2.6 wt%, Al 0.8-1.0 wt%, Mn 0.2-0.3 wt%, and the balance is Fe and unavoidable impurities.

2. The silicon steel material according to claim 1, characterized in that In the silicon steel material: The mass percentage of Al is a, and the sum of the mass percentages of Al and Si is b; wherein a / b=0.25-0.3; and / or The sum of the mass percentages of Al, Si and Mn is 3.6-3.8 wt %; preferably, the sum of the mass percentages of Al and Si is 3.3-3.5 wt %.

3. A method for preparing a motor core, characterized in that: The following steps are involved: The silicon steel sheets are sequentially subjected to core forming and annealing treatment to obtain the motor core; Wherein, the silicon steel sheet is made of the silicon steel material described in claim 1 or 2.

4. The method for preparing a motor core according to claim 1, wherein: Before the step of forming the iron core, the method further includes: coating the silicon steel sheet to form an insulating coating on the surface of the silicon steel sheet; Wherein, the thickness of the insulating coating on the surface of the silicon steel sheet is 0.8 to 1.5 μm; The insulating coating is a semi-organic magnesium chromate coating; the chemical composition of the semi-organic magnesium chromate coating includes, by mass percentage, Mg 3-3.5wt%, Al 1-1.5wt%.

5. The method for preparing a motor core according to claim 1, wherein: The steps of forming and manufacturing the iron core include: stamping, laminating and consolidating the silicon steel sheets in sequence; Wherein, a white sheet is obtained after stamping; the grain size of the white sheet is 105-115 μm; and the yield strength of the white sheet is 350-360 MPa.

6. The method for preparing a motor core according to claim 5, wherein: The white piece has two buckle points; Preferably, the buckle point is circular; the diameter ΦA of the circular buckle point is 1.9-2.1 mm, and the distance H1 between the center of the circular buckle point and the outer diameter of the white piece is 1.5-2 mm.

7. The method for preparing a motor core according to claim 1, wherein: After the step of forming the iron core, the method further includes: polishing the formed iron core; Preferably, the roughness of the inner diameter of the iron core after polishing is Ra<0.

4.

8. The method for preparing a motor core according to claim 1, wherein: The annealing treatment is carried out in a vacuum atmosphere; Preferably, the annealing temperature is 800-840° C., and the annealing time is 30-60 min.

9. The method for preparing a motor core according to any one of claims 3 to 8, characterized in that: The coverage area of ​​the surface insulation coating of the motor core is ≥50%; Preferably, the coverage area of ​​the insulating coating on the surface of the motor core is obtained by the following method: immersing the motor core in a CuSO4 solution, and then calculating the area of ​​the insulating coating on the surface of the motor core by metallographic second phase area; Further preferably, the mass percentage concentration of the CuSO4 solution is 3%.

10. A motor core, characterized in that: The grain size of the motor core is 135-145 μm; the yield strength of the motor core is 360-370 MPa; Preferably, the motor core is obtained by the preparation method according to any one of claims 3 to 9.

11. A motor, characterized in that: The motor core comprises the motor core as claimed in claim 10.

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