Ultrahigh-magnetic-induction non-oriented electrical steel as well as preparation method and application thereof

Abstract

The invention provides ultrahigh-magnetic-induction non-oriented electrical steel as well as a preparation method and application thereof. The non-oriented electrical steel comprises the following chemical components in percentage by weight: less than or equal to 0.005% of C, less than or equal to 0.3% of Si, 0.6% of 1t, less than or equal to 0.05% of P, less than or equal to 0.05% of S and the balance of Fe. Mn < = 0.8%, Al < = 0.005%, S < = 0.01%, P < = 0.01%, RE < = 0.002% and < = 0.005%, B < = 0.001% and < = 0.003%, N < = 0.003%, and the mass ratio of B to N is (1.4-1.6): 1. Rare earth elements Ce and La as well as B and N are added into molten steel for preparing the non-oriented electrical steel, so that the iron loss is synergistically reduced by 0.3-0.5, the magnetic induction is improved by 0.02-0.07 T, and the mechanical property is enhanced.

Description

Technical Field

[0001] This application relates to the technical field of steel manufacturing, and particularly relates to a kind of ultra-high magnetic induction non-oriented electrical steel and its preparation method and application. Background Art

[0002] Non-oriented electrical steel is widely used in manufacturing the iron cores of high-efficiency motors due to its excellent magnetic properties, low iron loss and moderate mechanical properties. However, with the progress of technology and the improvement of environmental protection requirements, the magnetic induction intensity of traditional non-oriented electrical steel is difficult to meet the needs of higher energy efficiency motors. The main technical means involved in the production process of high magnetic induction non-oriented silicon steel include extremely pure purification of molten steel, addition of micro-alloying elements, normalization treatment, stress relief annealing, etc. The application of these technical means has improved the magnetic induction intensity of non-oriented electrical steel to a certain extent, but still cannot fully meet the market demand. Therefore, developing a kind of ultra-high magnetic induction non-oriented electrical steel has become a research hotspot.

[0003] The patent with the publication number CN108486453A discloses a preparation method of a low iron loss and high magnetic induction non-oriented silicon steel sheet. After hot rolling, it introduces a small amount of cold rolling deformation and batch annealing process, and then through secondary cold rolling and annealing to improve the magnetic properties of low-silicon non-oriented silicon steel. Although the obtained magnetic properties are excellent, this technology requires batch annealing of hot rolled sheets and two cold rolling processes, with complex manufacturing processes and high production costs.

[0004] The patent with the publication number CN109112268A discloses a method for improving the magnetic properties of non-oriented silicon steel. Its chemical composition is Si 0.1 - 1.2%, Al 0.1 - 0.5%, Mn 0.05 - 0.4%, Sb 0 - 0.2%, Sn 0 - 0.2%, etc. The typical process is to control the final rolling temperature below the γ / α phase transformation temperature by 70 - 120°C, so that there are a small number of unrecrystallized grains with low stored energy in the hot rolled sheet. After normalization treatment, coarse grains of 120 - 200μm are obtained through the deformation-induced grain boundary migration mechanism to improve the magnetic properties of non-oriented silicon steel. The final rolling temperature is relatively low, the rolling force is large, and it is difficult to control the thickness and shape. Summary of the Invention

[0005] This application is carried out in view of the above problems, and its purpose is to provide a kind of ultra-high magnetic induction non-oriented electrical steel and its preparation method and application.

[0006] Specifically, in the first aspect of the present application, a kind of non-oriented electrical steel with ultra-high magnetic induction is provided. The chemical composition of the non-oriented electrical steel includes, by weight percentage: C≤0.005%, Si≤0.3%, 0.6%<Mn≤0.8%, Al≤0.005%, S≤0.01%, P≤0.01%, 0.002%≤RE≤0.005%, 0.001%≤B≤0.003%, N≤0.003%, and the mass ratio of B to N is 1.4 - 1.6:1, with the balance being Fe and inevitable inclusions.

[0007] Further, the RE includes at least one of Ce or La;

[0008] And / or, the mass ratio of Ce to La in the RE is 1:0.8 - 1.2.

[0009] In the second aspect of the present application, a preparation method of a non-oriented electrical steel with ultra-high magnetic induction is provided, including the following steps:

[0010] (1) Electromagnetically stir and continuously cast the refined molten steel to obtain a slab;

[0011] (2) Perform hot continuous rolling on the slab to obtain hot-rolled steel;

[0012] (3) Slowly cool the hot-rolled steel to obtain cooled steel;

[0013] (4) Perform pickling cold continuous rolling on the cooled steel to obtain cold-rolled steel;

[0014] (5) Anneal the cold-rolled steel to obtain non-oriented electrical steel.

[0015] Further, in step (1), the transverse magnetic field intensity during the electromagnetic stirring process is 0.3 - 0.5T.

[0016] Further, in step (2), the furnace charging temperature of the hot continuous rolling process is ≥200°C.

[0017] Further, in step (2), the heating temperature of the hot continuous rolling process is 1130 - 1170°C, the total time in the furnace is 200 - 400 min, the furnace discharging temperature is 1080 - 1120°C, the finishing rolling temperature is 860 - 900°C, and the coiling temperature is 730 - 770°C.

[0018] Further, in step (3), the temperature of the hot-rolled steel coil during the slow cooling process is ≥150°C.

[0019] Further, in step (4), the relative reduction ratio of the pickling cold continuous rolling process is 75% - 85%.

[0020] Further, the temperature of the annealing treatment in step (5) is 930-940°C, and the heat preservation time is 1.5-2 min.

[0021] The third aspect of the present application provides an application of the above-mentioned ultra-high magnetic induction non-oriented electrical steel in the iron core of an electric motor, a generator or a transformer.

[0022] The present invention has the following beneficial effects:

[0023] (1) By adding rare earth elements Ce and La to the molten steel for preparing non-oriented electrical steel, the present invention combines with impurity elements such as residual oxygen (O) and sulfur (S) in the molten steel to form rare earth oxysulfides with high melting points (such as Ce2O2S, La2S3). Eliminate grain boundary segregation, inhibit the aggregation of sulfur and oxygen at grain boundaries, and reduce grain boundary brittleness; at the same time, reduce hysteresis loss. The pure grain boundaries reduce the resistance to magnetic domain movement and improve the magnetic permeability (the magnetic induction of B5000 is increased by 0.02-0.05 T). In addition, the formed rare earth oxysulfides serve as heterogeneous nucleation cores during hot rolling, refine austenite grains, and reduce the pinning points for magnetic domain wall movement (the iron loss P1.5 / 50 is reduced by 0.3-0.5 W / kg); at the same time, inhibit the abnormal growth promotion of grains during annealing by pinning grain boundaries, {100} and {110} cubic textures, and inhibit the unfavorable {111} texture.

[0024] (2) By adding B atoms, during annealing, they diffuse along grain boundaries and segregate to grain boundaries, reducing the grain boundary energy and inhibiting grain coarsening, thereby increasing the proportion of the favorable {100} texture; at the same time, B atoms react with N atoms to form BN. During the hot rolling stage, BN particles are dispersed at grain boundaries and dislocations, inhibiting grain boundary migration during annealing. Specific embodiments

[0025] In order to make the objectives, technical solutions and advantages of the present application clearer, the following describes and illustrates the present application with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments provided in the present application without creative efforts belong to the scope of protection of the present application.

[0026] Obviously, the following description is only some examples or embodiments of the present application. For those of ordinary skill in the art, without creative efforts, the present application can also be applied to other similar scenarios. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for those of ordinary skill in the art related to the content disclosed in the present application, some design, manufacturing, or production changes based on the technical content disclosed in the present application are only conventional technical means and should not be understood as the content disclosed in the present application being insufficient.

[0027] If not specifically stated, the "including" and "comprising" mentioned in the present application mean open-ended, and can also be closed-ended. For example, the "including" and "comprising" can mean that other components not listed can also be included or comprised, or only the listed components can be included or comprised.

[0028] If not specifically stated, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) while B is true (or exists); or both A and B are true (or exist).

[0029] The first aspect of the present application provides a non-oriented electrical steel with ultra-high magnetic induction. The chemical composition of the non-oriented electrical steel by weight percentage includes C ≤ 0.005%, Si ≤ 0.3%, 0.6% < Mn ≤ 0.8%, Al ≤ 0.005%, S ≤ 0.01%, P ≤ 0.01%, 0.002% ≤ RE ≤ 0.005%, 0.001% ≤ B ≤ 0.003%, N ≤ 0.003%, and the mass ratio of B to N is 1.4 - 1.6:1, with the balance being Fe and unavoidable inclusions.

[0030] The RE includes at least one of Ce or La; the mass ratio of Ce to La in the RE is 1:0.8 - 1.2, preferably 1:1, and the weight percentage of RE is preferably 0.004%. By precisely controlling the composition ratio, the magnetic induction intensity and stability of the electrical steel are significantly improved.

[0031] In the present invention, rare earth elements Ce and La are added to the molten steel for preparing non-oriented electrical steel, which combine with impurity elements such as residual oxygen (O) and sulfur (S) in the molten steel to form rare earth oxysulfides with high melting points (such as Ce2O2S, La2S3). Grain boundary segregation is eliminated, the aggregation of sulfur and oxygen at grain boundaries is inhibited, and grain boundary brittleness is reduced; at the same time, hysteresis loss is reduced. The pure grain boundaries reduce the resistance to magnetic domain movement and improve the magnetic permeability (the magnetic induction B5000 is increased by 0.02 - 0.05 T). In addition, the formed rare earth oxysulfides serve as heterogeneous nucleation cores during hot rolling, refine austenite grains, and reduce the pinning points for magnetic domain wall movement (the iron loss P1.5 / 50 is reduced by 0.3 - 0.5 W / kg); at the same time, by pinning grain boundaries, the abnormal growth promotion of grains during annealing is inhibited, {100} and {110} cubic textures are promoted, and the unfavorable {111} texture is inhibited.

[0032] In the present invention, by adding B atoms, during annealing, they diffuse through grain boundaries and segregate to grain boundaries, reducing the grain boundary energy and inhibiting grain coarsening, so that the proportion of the favorable {100} texture is increased; at the same time, B atoms react with N atoms to form BN. During the hot rolling stage, BN particles are dispersed at grain boundaries and dislocations, inhibiting grain boundary migration during annealing. And the mass ratio of B to N is 1.4 - 1.6:1, preferably 1.5:1, to ensure the uniform distribution of BN particles, further refine grains, and improve the comprehensive properties of electrical steel. If the mass ratio of B to N is too high or too low, it will affect the distribution of BN particles and the effect of grain refinement, form coarse BN, deteriorate magnetism, and lead to a decline in magnetic properties.

[0033] The weight percentage of Mn is 0.6 - 0.8%. Excessive amount will cause excessive lattice distortion, instead increasing the dislocation pinning effect, hindering magnetic domain wall movement, and reducing magnetic induction and magnetic permeability; too low amount is not sufficient to effectively refine grains and affects magnetic properties. The solid solution strengthening effect of Mn can reduce the tendency of grain coarsening during annealing after cold rolling, refine grains, improve the yield strength and tensile strength of the steel, and enhance the mechanical properties of the material; at the same time, it inhibits the generation of γ phase and reduces the energy loss during the phase change process, ensuring the stability of electrical steel under high-frequency magnetic fields.

[0034] A trace amount of Al element is added to effectively purify the molten steel, reduce non-metallic inclusions, and improve the purity of the material; the S and P elements are strictly controlled within 0.01% to prevent grain boundary embrittlement and ensure the reliability of electrical steel under high-temperature and high-pressure environments.

[0035] The second aspect of the present application provides a method for preparing a super-high magnetic induction non-oriented electrical steel, including the following steps:

[0036] (1) Subjecting the refined molten steel to electromagnetic stirring and continuous casting to obtain a slab;

[0037] (2) Subjecting the slab to hot continuous rolling to obtain hot-rolled steel;

[0038] (3) Slow cooling treatment is carried out on the hot-rolled steel to obtain cooled steel;

[0039] (4) Pickling and cold tandem rolling treatment is carried out on the cooled steel to obtain cold-rolled steel;

[0040] (5) Annealing treatment is carried out on the cold-rolled steel to obtain non-oriented electrical steel.

[0041] Specifically, the tundish superheat degree of the continuous casting treatment in step (1) is 15 - 40 °C. The specific steps of the continuous casting treatment are to inject the molten steel into the tundish, control the superheat degree within the range of 15 - 40 °C to ensure good fluidity of the molten steel and reduce the generation of inclusions; then electromagnetic stirring is carried out to promote the floating of inclusions and improve the purity of the molten steel. During electromagnetic stirring, the transverse magnetic field strength is 0.3 - 0.5 T, which induces the migration of Si to the surface layer to form gradient Si. The Si content in the surface layer is 0.6 - 0.8% to reduce high-frequency eddy current, and the Si content in the core is 0.3% to maintain magnetic induction; the continuous casting speed is 1.5 - 2.5 m / min to ensure the quality of the slab.

[0042] Specifically, the furnace inlet temperature of the hot tandem rolling treatment in step (2) is ≥200 °C. The heating temperature of the hot tandem rolling treatment is 1130 - 1170 °C, high temperature promotes the diffusion of B and Ce, the total in-furnace time is 200 - 400 min, the furnace outlet temperature is 1080 - 1120 °C, the finish rolling temperature is 860 - 900 °C, triggering the precipitation of BN, Ce2O2S, etc., and the coiling temperature is 730 - 770 °C. After hot tandem rolling, the surface temperature of the slab is uniform, the grains are refined, the distribution of the precipitation phase is uniform, and the internal stress is reduced.

[0043] Specifically, the temperature of the hot-rolled steel coil in the slow cooling treatment in step (3) is ≥150 °C. The slow cooling treatment adopts segmented cooling. First, it is cooled at a rate of 5 - 10 °C / min to 600 °C, and then cooled at a rate of 2 - 5 °C / min to ensure uniform grain size and reduce internal stress; the slow cooling treatment time is 4 - 6 hours to ensure full recovery of grains and gradual release of internal stress, avoiding abnormal grain growth and stress concentration caused by too fast cooling rate, and providing a good tissue basis for subsequent cold tandem rolling.

[0044] Specifically, the relative reduction ratio of the pickling and cold tandem rolling treatment in step (4) is 75% - 85%. During cold tandem rolling, multi-pass reduction is adopted, and the reduction ratio of each pass is controlled at 10% - 15% to ensure uniform thickness of the steel plate and excellent surface quality; the temperature of the pickling solution is controlled at 60 - 80 °C, and hydrochloric acid solution is used for pickling, with the concentration controlled at 10 - 15% to remove the surface oxide layer and improve the surface cleanliness of the steel plate, laying a foundation for subsequent annealing treatment.

[0045] Specifically, in step (5), the annealing temperature is 930 - 940 °C, and the holding time is 1.5 - 2 min. This promotes the precipitation of BN particles, further refines the grains, and improves the magnetic properties. Finally, through the leveling treatment, the surface stress is eliminated to ensure the flatness and service performance of the electrical steel.

[0046] The third aspect of this application provides an application of the above-mentioned ultra-high magnetic induction non-oriented electrical steel in the iron core of an electric motor, a generator, or a transformer. The electrical steel has the characteristics of high magnetic induction and low loss, significantly improving the motor efficiency and reducing energy consumption. Its excellent mechanical properties and heat resistance ensure the long-term stable operation of the iron core, extend the service life of the equipment, and are widely used in various high-precision electrical equipment.

[0047] Example 1

[0048] An ultra-high magnetic induction non-oriented electrical steel, the chemical composition of the non-oriented electrical steel by weight percentage includes C 0.003%, Si 0.2%, Mn 0.7%, Al 0.001%, S 0.008%, P 0.005%, Ce + La 0.003%, B 0.0015%, N 0.001%. The mass ratio of Ce to La is 1:1, and the balance is Fe and inevitable inclusions.

[0049] The preparation method of the ultra-high magnetic induction non-oriented electrical steel includes the following steps: (1) Continuous casting treatment is carried out on the refined molten steel to obtain a slab. The tundish superheat during continuous casting is 25 °C, and electromagnetic stirring is carried out, with the transverse magnetic field intensity of 0.4 T; (2) Hot continuous rolling treatment is carried out on the slab. The charging temperature of hot continuous rolling is ≥200 °C, the heating temperature is 1150 °C, the total in-furnace time is 300 min, the tapping temperature is 1100 °C, the finishing rolling temperature is 880 °C, and the coiling temperature is 750 °C to obtain hot-rolled steel; (3) Slow cooling treatment is carried out on the hot-rolled steel to obtain cooled steel. The temperature of the hot-rolled steel coil during slow cooling treatment is ≥150 °C; (4) Pickling and cold continuous rolling treatment is carried out on the cooled steel to obtain cold-rolled steel. The relative reduction rate of pickling and cold continuous rolling treatment is 80%; (5) Annealing treatment is carried out on the cold-rolled steel. The annealing temperature is 930 °C, and the holding time is 2 min to obtain non-oriented electrical steel.

[0050] Example 2

[0051] An ultra-high magnetic induction non-oriented electrical steel, the chemical composition of the non-oriented electrical steel by weight percentage includes C 0.004%, Si 0.2%, Mn 0.65%, Al 0.004%, S 0.005%, P 0.006%, Ce + La 0.002%, B 0.0028%, N 0.002%. The mass ratio of Ce to La is 1:1, and the balance is Fe and inevitable inclusions.

[0052] The preparation method of the ultra-high magnetic induction non-oriented electrical steel comprises the following steps: (1) subjecting refined molten steel to continuous casting treatment to obtain a slab, with the tundish superheat degree of 30 °C during continuous casting treatment, and performing electromagnetic stirring, wherein the transverse magnetic field intensity is 0.3 T; (2) subjecting the slab to hot continuous rolling treatment, with the furnace charging temperature ≥ 200 °C, the heating temperature being 1170 °C, the total time in the furnace being 300 min, the tapping temperature being 1080 °C, the finishing rolling temperature being 880 °C, and the coiling temperature being 770 °C, to obtain hot-rolled steel; (3) subjecting the hot-rolled steel to slow cooling treatment to obtain cooled steel, with the temperature of the hot-rolled steel coil during slow cooling treatment ≥ 150 °C; (4) subjecting the cooled steel to pickling cold tandem rolling treatment to obtain cold-rolled steel, with the relative reduction ratio of pickling cold tandem rolling treatment being 80%; (5) subjecting the cold-rolled steel to annealing treatment, with the annealing temperature being 930 °C and the holding time being 2 min, to obtain non-oriented electrical steel.

[0053] Example 3

[0054] An ultra-high magnetic induction non-oriented electrical steel, the chemical composition of the non-oriented electrical steel by weight percentage comprises C 0.005%, Si 0.15%, Mn 0.7%, Al 0.003%, S 0.01%, P 0.01%, Ce + La 0.004%, B 0.0016%, N 0.001%, the mass ratio of Ce to La is 1:1, and the balance is Fe and inevitable inclusions.

[0055] The preparation method of the ultra-high magnetic induction non-oriented electrical steel comprises the following steps: (1) subjecting refined molten steel to continuous casting treatment to obtain a slab, with the tundish superheat degree of 15 °C during continuous casting treatment, and performing electromagnetic stirring, wherein the transverse magnetic field intensity is 0.5 T; (2) subjecting the slab to hot continuous rolling treatment, with the furnace charging temperature ≥ 200 °C, the heating temperature being 1150 °C, the total time in the furnace being 200 min, the tapping temperature being 1120 °C, the finishing rolling temperature being 860 °C, and the coiling temperature being 750 °C, to obtain hot-rolled steel; (3) subjecting the hot-rolled steel to slow cooling treatment to obtain cooled steel, with the temperature of the hot-rolled steel coil during slow cooling treatment ≥ 150 °C; (4) subjecting the cooled steel to pickling cold tandem rolling treatment to obtain cold-rolled steel, with the relative reduction ratio of pickling cold tandem rolling treatment being 75%; (5) subjecting the cold-rolled steel to annealing treatment, with the annealing temperature being 940 °C and the holding time being 2 min, to obtain non-oriented electrical steel.

[0056] Example 4

[0057] A kind of non-oriented electrical steel with ultra-high magnetic induction. The chemical composition of the non-oriented electrical steel by weight percentage includes C 0.002%, Si 0.2%, Mn 0.8%, Al 0.002%, S 0.009%, P 0.009%, Ce + La 0.005%, B 0.0023%, N 0.0015%. The mass ratio of Ce to La is 1:1, and the balance is Fe and unavoidable inclusions.

[0058] The preparation method of the non-oriented electrical steel with ultra-high magnetic induction includes the following steps: (1) Continuously casting the refined molten steel to obtain a slab. The superheat of the tundish during continuous casting is 40°C, and electromagnetic stirring is carried out, with the transverse magnetic field intensity of 0.4T; (2) Carry out hot continuous rolling on the slab. The furnace charging temperature for hot continuous rolling is ≥200°C, the heating temperature is 1130°C, the total time in the furnace is 400 min, the furnace discharging temperature is 1100°C, the finishing rolling temperature is 900°C, and the coiling temperature is 730°C to obtain hot-rolled steel; (3) Carry out slow cooling on the hot-rolled steel to obtain cooled steel. The temperature of the hot-rolled steel coil during slow cooling is ≥150°C; (4) Carry out pickling and cold continuous rolling on the cooled steel to obtain cold-rolled steel. The relative reduction ratio during pickling and cold continuous rolling is 85%; (5) Carry out annealing on the cold-rolled steel. The annealing temperature is 935°C, and the holding time is 1.5 min to obtain non-oriented electrical steel.

[0059] Example 5

[0060] A kind of non-oriented electrical steel with ultra-high magnetic induction. The chemical composition of the non-oriented electrical steel by weight percentage includes C 0.003%, Si 0.03%, Mn 0.8%, Al 0.001%, S 0.007%, P 0.004%, Ce + La 0.002%, B 0.003%, N 0.002%. The mass ratio of Ce to La is 1:1, and the balance is Fe and unavoidable inclusions.

[0061] The preparation method of the non-oriented electrical steel with ultra-high magnetic induction includes the following steps: (1) Continuously casting the refined molten steel to obtain a slab. The superheat of the tundish during continuous casting is 25°C, and electromagnetic stirring is carried out, with the transverse magnetic field intensity of 0.4T; (2) Carry out hot continuous rolling on the slab. The furnace charging temperature for hot continuous rolling is ≥200°C, the heating temperature is 1150°C, the total time in the furnace is 300 min, the furnace discharging temperature is 1100°C, the finishing rolling temperature is 880°C, and the coiling temperature is 750°C to obtain hot-rolled steel; (3) Carry out slow cooling on the hot-rolled steel to obtain cooled steel. The temperature of the hot-rolled steel coil during slow cooling is ≥150°C; (4) Carry out pickling and cold continuous rolling on the cooled steel to obtain cold-rolled steel. The relative reduction ratio during pickling and cold continuous rolling is 80%; (5) Carry out annealing on the cold-rolled steel. The annealing temperature is 930°C, and the holding time is 2 min to obtain non-oriented electrical steel.

[0062] Example 6

[0063] An extra-high magnetic induction non-oriented electrical steel, the chemical composition of the non-oriented electrical steel includes, by weight percentage, C 0.003%, Si 0.12%, Mn 0.7%, Al 0.001%, S 0.008%, P 0.006%, Ce + La 0.003%, B 0.0016%, N 0.001%, the mass ratio of Ce to La is 1:1.1, and the balance is Fe and unavoidable inclusions.

[0064] The preparation method of the extra-high magnetic induction non-oriented electrical steel includes the following steps: (1) continuous casting treatment is carried out on the refined molten steel to obtain a slab, the tundish superheat degree of the continuous casting treatment is 25°C, and electromagnetic stirring is carried out, wherein the transverse magnetic field intensity is 0.4T; (2) hot continuous rolling treatment is carried out on the slab, the furnace charging temperature of the hot continuous rolling is ≥200°C, the heating temperature is 1150°C, the total furnace time is 300min, the furnace discharging temperature is 1100°C, the finishing rolling temperature is 880°C, and the coiling temperature is 750°C to obtain hot-rolled steel; (3) slow cooling treatment is carried out on the hot-rolled steel to obtain cooled steel, the temperature of the hot-rolled steel coil in the slow cooling treatment is ≥150°C; (4) pickling cold continuous rolling treatment is carried out on the cooled steel to obtain cold-rolled steel, and the relative reduction ratio of the pickling cold continuous rolling treatment is 80%; (5) annealing treatment is carried out on the cold-rolled steel, the annealing temperature is 930°C, and the holding time is 2min to obtain non-oriented electrical steel.

[0065] Example 7

[0066] An extra-high magnetic induction non-oriented electrical steel, the chemical composition of the non-oriented electrical steel includes, by weight percentage, C 0.001%, Si 0.2%, Mn 0.7%, Al 0.001%, S 0.002%, P 0.005%, Ce + La 0.004%, B 0.0015%, N 0.001%, the mass ratio of Ce to La is 1:0.8, and the balance is Fe and unavoidable inclusions.

[0067] The preparation method of the ultra-high magnetic induction non-oriented electrical steel includes the following steps: (1) Continuously casting the refined molten steel to obtain a slab, with the tundish superheat of the continuous casting process being 25°C, and electromagnetic stirring being carried out, where the transverse magnetic field strength is 0.4T; (2) Conducting hot continuous rolling on the slab, with the charging temperature of the hot continuous rolling being ≥200°C, the heating temperature being 1150°C, the total time in the furnace being 300min, the discharging temperature being 1100°C, the finishing rolling temperature being 880°C, and the coiling temperature being 750°C to obtain hot-rolled steel; (3) Conducting slow cooling on the hot-rolled steel to obtain cooled steel, with the temperature of the hot-rolled steel coil during slow cooling being ≥150°C; (4) Conducting pickling cold continuous rolling on the cooled steel to obtain cold-rolled steel, with the relative reduction ratio of the pickling cold continuous rolling being 80%; (5) Conducting annealing on the cold-rolled steel, with the annealing temperature being 930°C and the holding time being 2min to obtain non-oriented electrical steel.

[0068] Example 8

[0069] An ultra-high magnetic induction non-oriented electrical steel, the chemical composition of the non-oriented electrical steel includes, by weight percentage, C 0.003%, Si 0.22%, Mn 0.7%, Al 0.003%, S 0.008%, P 0.005%, Ce+La 0.003%, B 0.0015%, N 0.001%, the mass ratio of Ce to La is 1:1, and the balance is Fe and inevitable inclusions.

[0070] The preparation method of the ultra-high magnetic induction non-oriented electrical steel includes the following steps: (1) Continuously casting the refined molten steel to obtain a slab, with the tundish superheat of the continuous casting process being 25°C, and electromagnetic stirring being carried out, where the transverse magnetic field strength is 0.4T; (2) Conducting hot continuous rolling on the slab, with the charging temperature of the hot continuous rolling being ≥200°C, the heating temperature being 1150°C, the total time in the furnace being 300min, the discharging temperature being 1100°C, the finishing rolling temperature being 880°C, and the coiling temperature being 750°C to obtain hot-rolled steel; (3) Conducting slow cooling on the hot-rolled steel to obtain cooled steel, with the temperature of the hot-rolled steel coil during slow cooling being ≥150°C; (4) Conducting pickling cold continuous rolling on the cooled steel to obtain cold-rolled steel, with the relative reduction ratio of the pickling cold continuous rolling being 80%; (5) Conducting annealing on the cold-rolled steel, with the annealing temperature being 930°C and the holding time being 2min to obtain non-oriented electrical steel.

[0071] Comparative Example 1

[0072] This comparative example is basically the same as Example 1, except that Ce+La is not included in the raw materials for preparing the non-oriented electrical steel.

[0073] Comparative Example 2

[0074] This comparative example is basically the same as Example 1, except that B is not included in the raw materials for preparing the non-oriented electrical steel.

[0075] Comparative Example 3

[0076] This comparative example is basically the same as Example 1, except that the raw materials for preparing the non-oriented electrical steel do not contain N.

[0077] Comparative Example 4

[0078] This comparative example is basically the same as Example 1, except that the Mn content in the raw materials for preparing the non-oriented electrical steel is 0.4%.

[0079] Comparative Example 5

[0080] This comparative example is basically the same as Example 1, except that electromagnetic stirring is not carried out in the preparation of the non-oriented electrical steel, and gradient Si is not formed.

[0081] The magnetic properties of the non-oriented electrical steels prepared in Examples 1-8 and Comparative Examples 1-5 of this application were measured, and the measurement results shown in Table 1 were obtained.

[0082] Group P1.5 / 50 (W / kg) B5000 (T) Yield strength (MPa) Example 1 5.25 1.83 335 Example 2 5.31 1.82 330 Example 3 5.29 1.83 328 Example 4 5.23 1.81 329 Example 5 5.37 1.80 334 Example 6 5.28 1.82 332 Example 7 5.34 1.83 331 Example 8 5.36 1.81 326 Comparative Example 1 5.78 1.78 315 Comparative Example 2 5.56 1.79 320 Comparative Example 3 5.47 1.79 317 Comparative Example 4 5.58 1.76 286 Comparative Example 5 5.63 1.78 298

[0083] As can be seen from Examples 1-8 and Comparative Example 1 in the above table, in the present invention, by adding rare earth elements Ce and La to the raw materials of the non-oriented electrical steel, they combine with impurity elements such as residual oxygen (O) and sulfur (S) in the molten steel to form rare earth oxysulfides with high melting points (such as Ce2O2S, La2S3). Grain boundary segregation is eliminated, the aggregation of sulfur and oxygen at the grain boundaries is inhibited, and grain boundary brittleness is reduced; at the same time, the hysteresis loss is reduced, and the pure grain boundaries reduce the resistance to magnetic domain movement, improving the magnetic permeability (the B5000 magnetic induction is increased by 0.02-0.05 T). In addition, the formed rare earth oxysulfides serve as heterogeneous nucleation cores during hot rolling, refining the austenite grains and reducing the pinning points for magnetic domain wall movement (the iron loss P1.5 / 50 is reduced by 0.3-0.5 W / kg).

[0084] As can be seen from Examples 1-8 and Comparative Examples 2-3, adding trace element B can significantly enhance the grain boundary bonding force, inhibit grain boundary slip, reduce grain boundary defects, and further improve the magnetic property stability. At the same time, B atoms and N atoms form BN, and BN particles are dispersed at the grain boundaries and dislocations during the hot rolling stage, inhibiting grain boundary migration during annealing and reducing the hysteresis loss (P1.5 / 50 is reduced by 0.2-0.3 W / kg), and the magnetic induction (B5000) is increased by 0.01-0.04 T.

[0085] It can be seen from Examples 1-8 and Comparative Example 4 that the solution strengthening effect of Mn can reduce the tendency of grain coarsening during annealing after cold rolling and refine the grains. When the Mn content is controlled at 0.4%, its austenite stabilization effect in the Fe-Mn-Si system weakens. A decrease in the Mn content will expand the γ-phase region, resulting in an increase in the volume fraction of the γ-phase during hot rolling or annealing, thereby reducing the yield strength. In addition, the addition of B and N relies on the solution strengthening of Mn to maintain the fine-grained structure. If Mn is insufficient, the grain boundary segregation efficiency of B decreases, the BN precipitates coarsen, and the pinning effect declines; the residual γ-phase leads to a decrease in the proportion of the favorable {100} texture, and further weakens the magnetic induction directionality. Therefore, optimizing the element ratio of Mn, B, and N and synergistically using rare earths Ce and La are the keys to achieving high performance of non-oriented electrical steel.

[0086] It can be seen from Examples 1-8 and Comparative Example 5 that the absence of transverse magnetic field and gradient Si will lead to a decline in magnetic properties. In the present invention, the high-Si surface layer preferentially forms a {100} cubic texture during annealing, enhancing the magnetic induction; the low-Si core allows a small amount of γ-phase to remain, and a {111} texture and {100} are formed in a mixed distribution during annealing, suppressing magnetic anisotropy. In addition, the high-Si + B / N grain boundary segregation in the surface layer forms a high-resistance grain boundary network, further reducing the eddy current loss; the B / N precipitates in the low-Si region of the core are finer in size, pinning dislocations and simultaneously reducing the pinning of magnetic domain walls, enhancing the magnetic induction. The gradient distribution of Si in the surface layer and the core, synergistically with B / N, refines the grains, optimizes the texture, and comprehensively improves the magnetic properties.

[0087] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same structure and the same effect as the technical idea within the scope of the technical solution of this application are included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various deformations that can be thought of by those skilled in the art are applied to the embodiments, and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of this application.

Claims

1. A non-oriented electrical steel with ultra-high magnetic induction, characterized in that The chemical composition of the non-oriented electrical steel by weight percentage includes C≤0.005%, Si≤0.3%, 0.6%<Mn≤0.8%, Al≤0.005%, S≤0.01%, P≤0.01%, 0.002%≤RE≤0.005%, 0.001%≤B≤0.003%, N≤0.003%, and the mass ratio of B to N is 1.4-1.6:1, with the balance being Fe and inevitable inclusions.

2. The non-oriented electrical steel with ultra-high magnetic induction according to claim 1, characterized in that, The RE includes at least one of Ce or La; and / or, the mass ratio of Ce to La in the RE is 1:0.8-1.

2.

3. A preparation method of the ultra-high magnetic induction non-oriented electrical steel according to claim 1 or 2, characterized in that, It includes the following steps: (1) Electromagnetic stirring and continuous casting treatment are carried out on the refined molten steel to obtain a slab; (2) The slab is subjected to hot continuous rolling treatment to obtain hot-rolled steel; (3) The hot-rolled steel is subjected to slow cooling treatment to obtain cooled steel; (4) The cooled steel is subjected to pickling cold continuous rolling treatment to obtain cold-rolled steel; (5) The cold-rolled steel is subjected to annealing treatment to obtain non-oriented electrical steel.

4. The preparation method of the non-oriented electrical steel with ultra-high magnetic induction according to claim 3, characterized in that, In step (1), the transverse magnetic field strength during the electromagnetic stirring process is 0.3-0.5T.

5. The preparation method of the non-oriented electrical steel with ultra-high magnetic induction according to claim 3, characterized in that, In step (2), the furnace inlet temperature of the hot continuous rolling treatment is ≥200°C.

6. The preparation method of the ultra-high magnetic induction non-oriented electrical steel according to claim 3, characterized in that, In step (2), the heating temperature of the hot continuous rolling treatment is 1130-1170°C, the total in-furnace time is 200-400 min, the furnace outlet temperature is 1080-1120°C, the finishing rolling temperature is 860-900°C, and the coiling temperature is 730-770°C.

7. The preparation method of the ultra-high magnetic induction non-oriented electrical steel according to claim 3, characterized in that, In step (3), the temperature of the hot-rolled steel coil during the slow cooling treatment is ≥150°C.

8. The preparation method of the non-oriented electrical steel with ultra-high magnetic induction according to claim 3, characterized in that In step (4), the relative reduction ratio of the pickling cold continuous rolling treatment is 75%-85%.

9. The preparation method of the non-oriented electrical steel with ultra-high magnetic induction according to claim 3, characterized in that, In step (5), the temperature of the annealing treatment is 930-940°C, and the holding time is 1.5-2 min.

10. Application of the ultra-high magnetic induction non-oriented electrical steel according to claim 1 or 2 in the iron core of an electric motor, generator or transformer.