Medium-high silicon non-oriented silicon steel thin strip as well as preparation method and application thereof

Abstract

The invention discloses a medium-high silicon non-oriented silicon steel thin strip and a preparation method and application thereof. The preparation method comprises the following steps: smelting molten steel which comprises the following elements in percentage by mass: less than or equal to 0.004% of C, 4.6-5.4% of Si, less than or equal to 0.01% of Al, 0.50-1.75% of Mn, less than or equal to 0.02% of P, less than or equal to 0.005% of S, less than or equal to 0.002% of Nb, less than or equal to 0.002% of V, less than or equal to 0.002% of Cr, less than or equal to 0.002% of Ti and the balance of Fe and inevitable impurity elements; the molten steel is subjected to double-roller thin-strip cast rolling to form a cast-rolled strip; and then sequentially carrying out hot rolling, cold rolling and the like to obtain the medium-high silicon non-oriented silicon steel thin strip. The medium-high silicon non-oriented silicon steel thin strip disclosed by the invention has relatively good magnetic property and mechanical property.

Description

Technical Field

[0001] The present invention relates to a medium-high silicon non-oriented electrical steel strip, a preparation method thereof and an application thereof, and belongs to the technical field of steel materials. Background Art

[0002] As an important soft magnetic material, non-oriented electrical steel is often used in key components of electronic devices such as motor stators (rotors) that need to work in a rotating magnetic field. As one of the key performance parameters for evaluating non-oriented electrical steel, iron loss and magnetic induction intensity are often emphasized. When used as a motor stator (rotor), the magnetic induction intensity of the non-oriented electrical steel material is related to the torque of the motor, while the iron loss, thermal conductivity, fatigue strength, etc. of the material are related to the maximum speed of the motor. There are various ways to improve the magnetic properties of electrical steel, and one of the more effective methods is to increase the silicon element content. Generally, it is considered that the content of (Si + Al) elements has a direct relationship with the magnetic properties of the material. However, as the silicon element content increases, various Fe-Si room-temperature brittle phases will form between iron and silicon elements, and the existence of these brittle phases will seriously affect the subsequent rolling process.

[0003] The vertical twin-roll strip casting and rolling technology is a production process that can directly cast and roll strip steel. It uses two reversely rotating copper rolls to solidify molten steel under sub-rapid process conditions and form a continuous steel strip. Compared with the traditional hot rolling process, this technology has the advantages of simple production process, short production line, near-net shape, low energy consumption, and low product cost.

[0004] Due to the high solidification and cooling rate of the vertical twin-roll strip casting and rolling technology, which is much higher than that of the traditional process, the sub-rapid solidification state it reaches can not only help reduce the adverse effects caused by element segregation, but also effectively avoid the generation of B2 and DO3 room-temperature low-plasticity deformation Fe-Si structures under the condition of medium-high silicon element content to a certain extent, thereby reducing the difficulty and problems of subsequent rolling.

[0005] CN117845029A discloses a method for efficiently preparing ultra-thin non-oriented electrical steel with high magnetic permeability and low iron loss. The chemical composition of the ultra-thin non-oriented electrical steel with high magnetic permeability and low iron loss includes, by weight percentage: Si: 2.42-3.82%, Al: 0.65-0.95%, Mn: 0.05-0.35%, C: 0.0015-0.0025%, N: 0.0005-0.002%, S: 0.0005-0.002%; the starting hot rolling temperature is 1000-1200°C, and the finishing rolling temperature is about 800-900°C; ultra-thin high magnetic induction non-oriented silicon steel with a thickness of ≤0.20mm is prepared using hot-rolled coils as raw materials; the ultra-thin high magnetic induction non-oriented silicon steel is prepared by primary cold rolling, intermediate annealing, secondary cold rolling, and annealing. The ultra-thin non-oriented electrical steel obtained by the method after final annealing has a strong advantageous texture, thereby achieving the purpose of high magnetic permeability and low iron loss of the ultra-thin non-oriented electrical steel.

[0006] CN116240350A discloses a low iron loss and high magnetic induction non-oriented silicon steel strip and its preparation method and application. The preparation method can directly form 1.5-3mm thick thin strip from molten steel by adjusting chemical composition and adopting vertical double-roll casting and rolling processes, and directly hot rolling. The preparation method has simple process and low energy consumption, and the non-oriented silicon steel strip obtained has excellent magnetic and mechanical properties.

[0007] The silicon content involved in the above-mentioned prior art is about 2.0 to 3.8 wt%. This medium silicon content cannot independently form a product with magnetic properties that meet the performance requirements. In ordinary processes, aluminum is generally added to improve the required magnetic properties. However, the special casting nozzle design of the twin-roll thin strip casting process causes aluminum elements to precipitate, agglomerate and block the nozzle, so the aluminum content needs to be controlled. Therefore, for processes such as twin-roll thin strip casting that require control of the aluminum content, the magnetic properties of the silicon process cannot be compensated, resulting in defects.

[0008] CN105598164B discloses a rolling preparation method for a high-silicon electrical steel thin strip. The method first uses a high-silicon electrical steel ingot heated with a furnace as a raw material to prepare a high-silicon electrical steel slab, then gradually cools down the high-silicon electrical steel slab and warm-rolls it to obtain a high-silicon electrical steel warm-rolled strip, and performs low-temperature annealing and cold rolling on the high-silicon electrical steel warm-rolled strip to prepare a high-silicon electrical steel thin strip. The method adopts gradual cooling and warm rolling, which can reduce the rolling temperature without affecting the cumulative maximum warm rolling deformation, thereby obtaining a better toughening and plasticizing effect; after warm rolling, annealing is performed under appropriate conditions, effectively reducing the residual tensile stress at the edge of the high-silicon electrical steel warm-rolled strip while avoiding the orderly structure recovery and improving the cold rolling yield.

[0009] CN110172634B discloses a high-silicon electrical steel sheet and a preparation method thereof. The chemical composition of the high-silicon electrical steel sheet by weight percentage includes: Si: 6.91% - 6.98%, Ce: 0.02 - 0.03%, Al: 0.6 - 0.8%, C < 0.01%, Mn < 0.01%, N < 0.003%, O < 0.003%, P < 0.01%, S < 0.01%, and the balance is Fe. This technology adds rare earth Ce element to Fe-6.9%Si steel to improve the processing performance of the high-silicon steel sheet. At the same time, an asynchronous combined warm rolling process is adopted to refine the grain size of the rolled piece, effectively solving the problem of poor processing performance of the high-silicon steel sheet. Moreover, cross cold rolling ensures the reduction force and reduction amount at the edge of the rolled plate, overcomes the problems of edge cracking and poor plate shape of the sheet, and improves the mechanical properties.

[0010] The silicon content involved in the above prior art is approximately 6.5 - 6.9 wt%, and good magnetic properties are relatively easy to form under such a high silicon content. However, a large number of B2 and DO3 room-temperature low-plasticity deformation Fe-Si structures are likely to be generated in the as-cast products, making the subsequent rolling process difficult to carry out, and thus the stable industrial production of non-oriented electrical steel products cannot be achieved. Summary of the Invention

[0011] To solve at least one of the above technical problems, an object of the present invention is to provide a medium-high silicon non-oriented silicon steel strip and a preparation method and application thereof. The medium-high silicon non-oriented silicon steel strip of the present invention has better magnetic properties and mechanical properties.

[0012] To achieve the above object, in the first aspect of the present invention, a preparation method of a medium-high silicon non-oriented silicon steel strip is provided, which includes the following steps:

[0013] (1) Smelting molten steel, by mass percentage, the molten steel includes the following elements: C ≤ 0.004%, Si: 4.6 - 5.4%, Al ≤ 0.01%, Mn: 0.50 - 1.75%, P ≤ 0.02%, S ≤ 0.005%, Nb ≤ 0.002%, V ≤ 0.002%, Cr ≤ 0.002%, Ti ≤ 0.002%, and the balance is Fe and inevitable impurity elements;

[0014] (2) Passing the molten steel through twin-roll strip casting and rolling to form a cast-rolled strip;

[0015] (3) Hot rolling the cast-rolled strip to obtain a hot-rolled strip;

[0016] (4) Cold rolling the hot-rolled strip to obtain a cold-rolled strip, and then annealing to obtain the medium-high silicon non-oriented silicon steel strip.

[0017] According to a specific embodiment of the present invention, preferably, in step (2), the molten steel flows into the molten pool through a tundish, a transition ladle, and a flow distributor in a nitrogen atmosphere, and then is formed into a cast-rolled strip by twin-roll thin strip casting. The superheat of the molten steel in the molten pool is 70 to 100 °C, and the roll gap during the twin-roll thin strip casting process is 1.0 to 2.5 mm.

[0018] According to a specific embodiment of the present invention, preferably, step (2) includes: adjusting the solidification cooling rate during the twin-roll thin strip casting process according to the silicon content in the molten steel, so that the solidification cooling rate and the silicon content in the molten steel satisfy the following relationship: where w Si is the mass percentage of silicon in the molten steel, without unit; is the solidification cooling rate, °C / s.

[0019] According to a specific embodiment of the present invention, preferably, step (2) includes: adjusting the casting and rolling speed during the twin-roll thin strip casting process according to the silicon content in the molten steel, so that the casting and rolling speed and the silicon content in the molten steel satisfy the following relationship: v 拉 = [1 - 0.25(w Si - 4.37)]V, where w Si is the mass percentage of silicon in the molten steel, without unit; V takes a value of 1 m / s; v 拉 is the casting and rolling speed, m / s.

[0020] According to a specific embodiment of the present invention, preferably, step (2) includes: the twin-roll thin strip casting process is carried out in a hot box filled with protective gas. Adjust the content of the protective gas components in the hot box during the twin-roll thin strip casting process according to the silicon content in the molten steel. The protective gas in the hot box includes a mixture of argon and nitrogen, so that the content of the protective gas components in the hot box and the silicon content in the molten steel satisfy the following relationship: N2 content = 20 + 50(w Si - 4.37)%, Ar content = 80 - 50(w Si - 4.37)%, where w Si is the mass percentage of silicon in the molten steel, without unit.

[0021] According to a specific embodiment of the present invention, preferably, step (2) includes: uniformly cooling the cast-rolled strip in a hot box filled with protective gas to 1000 to 1200 °C, the cooling time is less than 60 s, the cooling rate is less than 20 °C / s, and the content of the protective gas components in the hot box during the cooling process is the same as that in the hot box during the twin-roll thin strip casting process.

[0022] According to a specific embodiment of the present invention, preferably, step (3) includes: performing single-pass hot rolling when the temperature of the cast-rolled strip drops to 850-1200 °C, the reduction ratio of the hot rolling being 15-75%, and coiling at 450-650 °C after the hot rolling to obtain the hot-rolled strip.

[0023] According to a specific embodiment of the present invention, preferably, in step (3), the thickness of the hot-rolled strip is 0.8-1.6 mm.

[0024] According to a specific embodiment of the present invention, preferably, step (4) includes: subjecting the hot-rolled strip to single-pass cold rolling or two-pass cold rolling with intermediate annealing to obtain the cold-rolled strip.

[0025] According to a specific embodiment of the present invention, preferably, in step (4), the thickness of the cold-rolled strip is 0.1-0.35 mm.

[0026] According to a specific embodiment of the present invention, preferably, in step (4), when two-pass cold rolling with intermediate annealing is adopted, the reduction ratio of the first cold rolling is 60% or less, and the first cold rolling is carried out to a thickness of 0.5-0.75 mm; the intermediate annealing is carried out in one of the following methods or method two: Method one: annealing is carried out at 800-1000 °C in an atmosphere of a hydrogen-argon gas mixture for 2-8 min, and then cooled to room temperature; Method two: in a wet hydrogen-nitrogen gas mixture atmosphere, the temperature is raised to 1000-1100 °C for annealing for 1-6 min, the dew point d.p. of the wet hydrogen-nitrogen gas mixture atmosphere = 35-45 °C, the temperature of the water in the atmosphere is 60-65 °C, and the ratio P H2O / P H2 = 0.35-0.45; then it is cooled to room temperature in a dry hydrogen-nitrogen gas mixture atmosphere, the dew point d.p. of the dry hydrogen-nitrogen gas mixture atmosphere < -20 °C, the temperature of the dry hydrogen-nitrogen gas mixture atmosphere is room temperature, and the ratio P H2O / P H2 = 0.03; the reduction ratio of the second cold rolling is 10-50%, and the second cold rolling is carried out to a thickness of 0.1-0.35 mm.

[0027] According to the specific embodiments of the present invention, preferably, in step (4), the annealing includes one or both of continuous annealing and batch annealing; the conditions for continuous annealing include: annealing is carried out at 1000-1200°C in an atmosphere of a hydrogen-argon gas mixture, for a time of 2-10 min, with a heating rate of more than 50°C / s and a cooling rate of less than 80°C / s; the conditions for batch annealing include: annealing is carried out at 900-1200°C in an atmosphere of a hydrogen-argon gas mixture, for a time of 0.1-1 h, and then cooled to room temperature at a rate of 10°C / s or less.

[0028] According to the specific embodiments of the present invention, preferably, step (4) further includes: according to the index requirements of the product, selecting to carry out continuous annealing, or batch annealing, or continuous annealing and batch annealing; more preferably, the indexes of the product include one or more of grain size, texture state and magnetic properties. Further preferably, in step (4), after continuous annealing of the cold-rolled strip, if one or more of the grain size, texture state and magnetic properties of the product do not reach the predetermined value, or it is necessary to further adjust one or more of the grain size, texture state and magnetic properties of the product, then batch annealing is carried out further.

[0029] According to the specific embodiments of the present invention, preferably, step (4) further includes: coating the cold-rolled strip after continuous annealing and / or batch annealing with a coating to obtain the medium-high silicon non-oriented silicon steel thin strip. More preferably, the thickness of the coating is 0.05-0.18 mm.

[0030] The second aspect of the present invention provides a medium-high silicon non-oriented silicon steel thin strip, which is obtained by the preparation method of the medium-high silicon non-oriented silicon steel thin strip described above.

[0031] The third aspect of the present invention provides the application of the above-mentioned medium-high silicon non-oriented silicon steel thin strip in an automotive drive motor.

[0032] The present invention has at least the following beneficial effects:

[0033] By controlling the silicon content in the molten steel to be medium-high silicon content, and controlling the contents of C, S, P, and the contents of Al, Mn, Nb, V, Cr, Ti, combined with the relationship between the silicon content in the molten steel developed in the present invention and the solidification cooling rate, casting and rolling speed, and the composition content of the hot box protective gas during the twin-roll thin strip casting and rolling process, the twin-roll thin strip casting and rolling process is further controlled. And preferably further combined with the control of processes such as cold rolling, continuous annealing, and box annealing, thereby not only being able to obtain the magnetic property gain brought by the medium-high silicon composition, but also helping to avoid the generation of B2 and DO3 room temperature low-plastic deformation Fe-Si structures, affecting the evolution of grain size and texture distribution, and further controlling the magnetic properties and mechanical properties of the product, while reducing the harmful effects of small-size inclusions. Moreover, by controlling the elemental composition of the molten steel and the twin-roll thin strip casting and rolling process, the present invention can uniformly form a cast strip during twin-roll thin strip casting and rolling, without generating cold steel, broken strip, leakage of steel, etc.; and form a solid continuous cast strip under the conditions of the sub-rapid solidification process, which can not only improve the magnetic properties, but also help to avoid the problems of poor product processability and difficult control of subsequent rolling processes. The present invention obtains a solution strengthening effect by adopting sub-rapid solidification and provides conditions for dispersion strengthening, so that the product can obtain ideal mechanical properties. Therefore, the medium-high silicon non-oriented silicon steel thin strip of the present invention has better magnetic properties and mechanical properties, and at the same time has the advantages of good processability and easy control of the rolling process. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic flow chart of the preparation method of the medium-high silicon non-oriented silicon steel thin strip in the specific embodiment of the present invention.

[0035] Figure 2 It is a schematic flow chart of the twin-roll thin strip casting and rolling process in the specific embodiment of the present invention.

[0036] Figure 3 It is a metallographic structure diagram of the cross section of the cast strip in Example 1.

[0037] Figure 4 It is the Fe-Si phase diagram of the medium-high silicon non-oriented silicon steel thin strip in Example 1.

[0038] Figure 5 It is the XRD spectrum diagram of the cross section of the cast strip in Example 1.

[0039] Description of the reference numerals in the drawings:

[0040] 1 - tundish; 2 - transition ladle; 3 - distributor; 4 - molten pool; 5 - vertical twin-roll thin strip caster; 6 - cast strip; 7 - pinch roll; 8 - hot rolling mill stand; 9 - water-cooled roller table; 10 - flying shear; 11 - coiler; 12 - continuous rolling and continuous annealing unit; 13 - box annealing furnace; 14 - composition detection device. SPECIFIC EMBODIMENTS

[0041] For a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the following detailed description of the present invention is provided, but it should not be construed as a limitation on the scope of implementation of the present invention.

[0042] According to a specific embodiment of the first aspect of the present invention, the present invention provides a method for preparing a medium-high silicon non-oriented silicon steel thin strip, which includes the following steps:

[0043] (1) Smelting molten steel, by mass percentage, the molten steel includes the following elements: C≤0.004%, Si: 4.6 - 5.4%, Al≤0.01%, Mn: 0.50 - 1.75%, P≤0.02%, S≤0.005%, Nb≤0.002%, V≤0.002%, Cr≤0.002%, Ti≤0.002%, and the balance is Fe and inevitable impurity elements;

[0044] (2) Passing the molten steel through twin-roll strip casting to form a cast strip;

[0045] (3) Hot-rolling the cast strip to obtain a hot-rolled strip;

[0046] (4) Cold-rolling the hot-rolled strip to obtain a cold-rolled strip, which is the medium-high silicon non-oriented silicon steel thin strip mentioned above.

[0047] In some embodiments, in step (2), the molten steel flows into the molten pool through a tundish, a transition ladle, and a distributor in a nitrogen atmosphere, and then forms a cast strip through twin-roll strip casting. The superheat of the molten steel in the molten pool is 70 - 100°C, and the roll gap during the twin-roll strip casting process is 1.0 - 2.5 mm. Among them, the tundish, transition ladle, distributor, and molten pool can adopt the devices in the prior art. The twin-roll strip casting can be carried out using a vertical twin-roll strip caster in the prior art. Those skilled in the art can understand that the roll gap during the twin-roll strip casting process is the thickness of the cast strip. Therefore, the thickness of the cast strip is 1.0 - 2.5 mm. Those skilled in the art can make conventional adjustments to control conditions such as the tundish, transition ladle, distributor flow rate, and molten pool depth, as long as a cast strip with a thickness of 1.0 - 2.5 mm can be continuously and stably cast.

[0048] In some embodiments, step (2) includes: adjusting the solidification cooling rate during the twin-roll strip casting process according to the silicon content in the molten steel, so that the solidification cooling rate and the silicon content in the molten steel satisfy the following relationship: where w Si is the mass percentage of silicon in the molten steel, without unit; is the solidification cooling rate, °C / s.

[0049] In some embodiments, step (2) includes: adjusting the casting speed during twin-roll strip casting according to the silicon content in the molten steel, such that the casting speed and the silicon content in the molten steel satisfy the following relationship: v 拉 =[1 - 0.25(w Si - 4.37)], where w Si is the mass percentage of silicon in the molten steel, unitless; V takes a value of 1 m / s; v 拉 is the casting speed, in m / s.

[0050] In some embodiments, step (2) includes: the twin-roll strip casting process is carried out in a hot box filled with protective gas. Adjust the content of the protective gas components in the hot box during the twin-roll strip casting process according to the silicon content in the molten steel. The protective gas in the hot box includes a mixture of argon and nitrogen, such that the content of the protective gas components in the hot box and the silicon content in the molten steel satisfy the following relationship: N2 content = 20 + 50(w Si - 4.37)%, Ar content = 80 - 50(w Si - 4.37)%, where w Si is the mass percentage of silicon in the molten steel, unitless. It should be noted that the N2 content and the Ar content here refer to the respective volume percentages (vol%) in the mixture gas.

[0051] In some embodiments, step (2) includes: uniformly cooling the cast strip in a hot box filled with protective gas to 1000 - 1200 °C, with the cooling time being less than 60 s and the cooling rate being less than 20 °C / s. The content of the protective gas components in the hot box during the cooling process is the same as that in the hot box during the twin-roll strip casting process.

[0052] In some embodiments, step (2) includes: before the molten steel undergoes twin-roll strip casting, detect the silicon content in the molten steel. According to the detected silicon content in the molten steel, control the solidification cooling rate, casting speed, and the content of the protective gas components in the hot box during the twin-roll strip casting process in accordance with the above relationships. When the detected silicon content in the molten steel does not satisfy the above relationships with the solidification cooling rate, or the casting speed, or the content of the protective gas components in the hot box, it can be processed in a timely manner. Preferably, the component detection device for detecting the silicon content in the molten steel can be arranged above the molten pool. The component detection device can adopt various X-ray spectroscopy detection instruments in the prior art, and the present invention does not impose special restrictions on it.

[0053] The present invention controls the silicon content in molten steel to be medium-high silicon content (4.6 - 5.4%), and controls the contents of C, S, P, and the contents of Al, Mn, Nb, V, Cr, Ti. Combining the relationship between the silicon content in molten steel developed by the present invention and the solidification cooling rate, casting and rolling speed, and the composition content of the hot box protective gas during the twin-roll strip casting process, and then controlling the twin-roll strip casting process, it can enable the twin-roll strip casting to uniformly form a cast strip, ensuring no cold steel, strip breakage, steel leakage, etc.; and forming a solid continuous cast strip under the conditions of the semi-rapid solidification process, obtaining a solid solution strengthening effect by semi-rapid solidification, providing conditions for dispersion strengthening, and also helping to control the segregation of elements such as Si and Mn, reducing the harmful effects of small-size inclusions, so that the cast strip can still avoid forming the B2 and DO3 room-temperature low-plasticity deformation Fe-Si structures under the medium-high silicon content of the present invention, thereby avoiding problems such as poor product processing performance and difficult control of subsequent rolling processes, and at the same time affecting the evolution of grain size and texture distribution, so that the product obtains ideal mechanical properties and improved magnetic properties.

[0054] In some embodiments, step (3) includes: performing single-pass hot rolling when the temperature of the cast strip drops to 850 - 1200 °C, the reduction rate of the hot rolling being 15 - 75%, and coiling at 450 - 650 °C after the hot rolling to obtain the hot-rolled strip. Equipment such as a hot rolling mill stand and a coiler in the prior art can be used to perform hot rolling and coiling on the cast strip.

[0055] In some embodiments, in step (3), the thickness of the hot-rolled strip is 0.8 - 1.6 mm, preferably 1.0 - 1.6 mm.

[0056] In some embodiments, step (4) includes: obtaining the cold-rolled strip by subjecting the hot-rolled strip to single-pass cold rolling or two-pass cold rolling with intermediate annealing. Equipment such as a continuous cold rolling and annealing unit in the prior art can be used to uncoil and cold roll the hot-rolled strip and selectively perform intermediate annealing treatment.

[0057] In some embodiments, in step (4), the thickness of the cold-rolled strip is 0.1 - 0.35 mm.

[0058] In some embodiments, in step (4), when double cold rolling with intermediate annealing is adopted, the reduction ratio of the first cold rolling is 60% or less, and the first cold rolling is carried out to a thickness of 0.5 - 0.75 mm; the intermediate annealing is carried out in one of the following two ways: Way 1: Annealing is carried out at 800 - 1000 °C under a mixed gas atmosphere of hydrogen and argon for 2 - 8 min, and then cooled to room temperature (the cooling rate is preferably 10 °C / s or less); Way 2: Under a wet mixed gas atmosphere of hydrogen and nitrogen, it is heated to 1000 - 1100 °C for annealing for 1 - 6 min, the dew point d.p. of the wet mixed gas atmosphere of hydrogen and nitrogen is 35 - 45 °C, the temperature of water in the atmosphere is 60 - 65 °C, and the ratio of the partial pressure of water and the partial pressure of hydrogen in the atmosphere P H2O / P H2 = 0.35 - 0.45; then it is cooled to room temperature under a dry mixed gas atmosphere of hydrogen and nitrogen (the cooling rate is preferably 10 °C / s or less), the dew point d.p. of the dry mixed gas atmosphere of hydrogen and nitrogen is < -20 °C, the temperature of the dry mixed gas atmosphere of hydrogen and nitrogen is room temperature, and the ratio of the partial pressure of water and the partial pressure of hydrogen in the atmosphere P H2O / P H2 = 0.03; the reduction ratio of the second cold rolling is 10 - 50%, and the second cold rolling is carried out to a thickness of 0.1 - 0.35 mm. Among them, preferably, the mixed gas of hydrogen and argon in Way 1 of the intermediate annealing includes 25 vol% of hydrogen and 75 vol% of argon. Preferably, the mixed gas of hydrogen and nitrogen in Way 2 of the intermediate annealing includes 20 vol% of hydrogen and 80 vol% of nitrogen. Those skilled in the art can understand that the components of the mixed gas here refer to the components excluding water, and the water content in the mixed gas is controlled by the above-mentioned partial pressure ratio.

[0059] In some embodiments, in step (4), the annealing includes one or both of continuous annealing and batch annealing; the conditions of the continuous annealing include: annealing is carried out at 1000 - 1200 °C under a mixed gas atmosphere of hydrogen and argon for 2 - 10 min, the heating rate is 50 °C / s or more, and the cooling rate is 80 °C / s or less; the conditions of the batch annealing include: annealing is carried out at 900 - 1200 °C under a mixed gas atmosphere of hydrogen and argon for 0.1 - 1 h, and then cooled to room temperature at a rate of 10 °C / s or less. Among them, preferably, the mixed gas of hydrogen and argon in the continuous annealing includes 25 vol% of hydrogen and 75 vol% of argon. A continuous annealing and pickling line in the prior art can be used to carry out continuous annealing on the hot rolled strip after the above-mentioned cold rolling. Preferably, the mixed gas of hydrogen and argon in the batch annealing includes 25 vol% of hydrogen and 75 vol% of argon.

[0060] In some embodiments, step (4) further includes: according to the index requirements of the product, selecting continuous annealing, or batch annealing, or both continuous annealing and batch annealing; preferably, the indexes of the product include one or more of grain size, texture state, and magnetic properties. More preferably, in step (4), after continuous annealing of the cold-rolled strip, if one or more of the grain size, texture state, and magnetic properties of the product do not reach the predetermined values, or if it is necessary to further adjust one or more of the grain size, texture state, and magnetic properties of the product, then batch annealing is further carried out. It should be noted that the present invention does not impose special restrictions on the specific index requirements of the product, and can be adjusted according to the performance requirements of the produced grades to meet the performance requirements of different grades of products. In the preferred embodiment of the present invention, after obtaining the cold-rolled strip that has been continuously annealed by the continuous rolling and continuous annealing process, if the grain size, texture state, or magnetic properties of the product still do not reach the predetermined values, or if it is necessary to further adjust the grain size, texture state, or magnetic properties of the product, then the above-mentioned batch annealing is carried out on the cold-rolled strip that has been continuously annealed to further adjust the grain size, texture state, or magnetic properties to obtain a medium and high silicon non-oriented silicon steel thin strip with low thickness, low iron loss, and high magnetic induction.

[0061] In some embodiments, step (4) further includes: coating the cold-rolled strip after continuous annealing and / or batch annealing to obtain the medium and high silicon non-oriented silicon steel thin strip. Among them, the coating can use the coatings adapted to non-oriented electrical steel in the prior art, and the present invention does not impose special restrictions on the composition of the coating. Preferably, the thickness of the coating is 0.05 - 0.18 mm.

[0062] The cold-rolled strip after continuous annealing and / or batch annealing of the present invention has oxide layer insulation performance, so the thickness of the coated coating can be appropriately reduced, improving the product lamination factor and performance utilization rate.

[0063] In some embodiments, as Figure 1 and Figure 2 shown, the process of the method for preparing the medium and high silicon non-oriented silicon steel thin strip of the present invention includes:

[0064] The molten steel flows into the molten pool 4 through the tundish 1, the transfer ladle 2, and the distributor 3. A composition detection device 14 is arranged above the side of the molten pool 4, and then it enters the vertical twin-roll thin strip casting and rolling mill 5 for casting and rolling to obtain the cast strip 6;

[0065] The cast strip 6 enters the hot rolling mill stand 8 for hot rolling through the pinch roll 7, and then successively passes through the water-cooled roller table 9 for cooling and the flying shear 10 for trimming, and then is coiled by the coiler 11 to obtain the hot-rolled strip;

[0066] The hot-rolled strip is cold-rolled by the continuous rolling and continuous annealing unit 12 to obtain the cold-rolled strip, and then continuous annealing is carried out to obtain the medium and high silicon non-oriented silicon steel thin strip;

[0067] Selectively anneal the cold-rolled strip after continuous annealing in the bell-type annealing furnace 13 to obtain a medium-high silicon non-oriented silicon steel thin strip.

[0068] According to a specific embodiment of the second aspect of the present invention, the present invention provides a medium-high silicon non-oriented silicon steel thin strip, which is obtained by the preparation method of the medium-high silicon non-oriented silicon steel thin strip described above.

[0069] According to a specific embodiment of the third aspect of the present invention, the present invention provides the application of the above-mentioned medium-high silicon non-oriented silicon steel thin strip in an automotive drive motor.

[0070] The present invention aims at the problems in the prior art that the process for preparing an ultra-thin strip of non-oriented electrical steel from a medium-thick plate or ingot with aluminum added at a medium silicon content is complex, energy-consuming and time-consuming, and the magnetic properties of the medium-silicon content products using the twin-roll thin strip casting process cannot be compensated, and also aims at the problem that the generation of the B2 and DO3 room-temperature low-plasticity deformation Fe-Si structures, which are difficult to avoid in the as-cast state with a high silicon content, makes the subsequent rolling process extremely difficult. Therefore, the present invention has developed a preparation method for a medium-high silicon non-oriented silicon steel thin strip.

[0071] The present invention controls the silicon content in the molten steel to be medium-high silicon content, and controls the contents of C, S, P and the contents of Al, Mn, Nb, V, Cr, Ti. Combining the relationship between the silicon content in the molten steel developed by the present invention and the solidification cooling rate, casting and rolling speed and the composition content of the hot box protective gas during the twin-roll thin strip casting process, the twin-roll thin strip casting process is further controlled. And preferably further combined with the control of processes such as cold rolling, continuous annealing, and bell-type annealing, it is possible to obtain the magnetic property gain brought by the medium-high silicon composition, and at the same time help to avoid the generation of the B2 and DO3 room-temperature low-plasticity deformation Fe-Si structures, which affect the evolution of grain size and texture distribution, and reduce the harmful effects of small-sized inclusions. Thus, both the magnetic properties and mechanical properties of the product reach better effects. The medium-high silicon non-oriented silicon steel thin strip of the present invention is a medium-high silicon, low-thickness, low iron loss, high magnetic induction, non-oriented electrical steel thin strip; its yield strength R p is 420 - 550 N / mm 2 , the tensile strength R m is 530 - 720 N / mm 2 , the elongation is 12 - 17%; its low-frequency iron loss P 1.5 / 50 is 2.00 - 2.50 W / kg, the medium-frequency iron loss P 1.0 / 400 is 10.00 - 14.50 W / kg, the magnetic induction B 50 is 1.60 - 1.73 T. At the same time, the present invention has the advantages of good processability and easy control of the rolling process.

[0072] The present invention will be specifically described below through embodiments. However, the present invention is not limited to these embodiments, and of course, various modifications can be made within the scope of the key points of the present invention for implementation.

[0073] Testing method:

[0074] Magnetic properties: Tested in accordance with GB / T 3655-2008.

[0075] Mechanical properties: Tested in accordance with GB / T 228-2010 and GB / T 235-2013.

[0076] Metallographic structure diagram: Tested in accordance with GB / T 13298-2015.

[0077] Example 1

[0078] Smelting: Molten steel is obtained through smelting. By mass percentage, the molten steel includes the following elements: 0.0035% C, 5.3% Si, 0.008% Al, 1.55% Mn, 0.01% P, 0.0035% S, Nb ≤ 0.001%, V ≤ 0.001%, Cr ≤ 0.001%, Ti ≤ 0.001%, and the balance is Fe and inevitable impurity elements;

[0079] Casting: In a nitrogen atmosphere, the molten steel flows into the molten pool 4 through the tundish 1, the transition ladle 2, and the distributor 3. A composition detection device 14 is arranged above the side of the molten pool 4, and then it enters the vertical twin-roll thin strip continuous casting and rolling mill 5 for casting and rolling. The superheat of the molten steel in the molten pool 4 is 80 ± 10 °C, the roll gap of the vertical twin-roll thin strip continuous casting and rolling mill 5 is 1.8 ± 0.1 mm, and the casting and rolling process is carried out in a hot box filled with protective gas. According to the silicon content in the molten steel, the solidification cooling rate, the casting and rolling speed, and the component content of the protective gas in the hot box during the casting and rolling process are adjusted to satisfy the following relationship: v 拉 =[1 - 0.25(w Si - 4.37)]V, N2 content = 20 + 50(w Si - 4.37)%, Ar content = 80 - 50(w Si-4.37)%, the silicon content in the molten steel of this embodiment is 5.3%, so the solidification cooling rate needs to be controlled at 1674 - 1860 °C / s, the casting and rolling speed needs to be controlled at 0.7675 m / s, the protective gas in the hot box is a nitrogen-argon mixture, and the volume content of nitrogen in this mixture is 66.5% and the volume content of argon is 33.5%, obtaining a casting and rolling strip 6 with a thickness of 1.8 ± 0.1 mm; then the casting and rolling strip 6 is uniformly cooled to 1100 °C in a hot box with protective gas, the cooling time is less than 1.5 s, the cooling rate is less than 20 °C / s, and the component content of the protective gas in the hot box during the cooling process is the same as that during the casting and rolling process;

[0080] Hot rolling: When the temperature of the casting and rolling strip 6 is uniformly cooled to 1100 °C, the casting and rolling strip 6 enters the hot rolling mill 8 from the pinch roll 7 for single-pass hot rolling, the rolling reduction rate of hot rolling is about 44%, and then it is cooled successively through the water-cooled roller table 9 and trimmed by the flying shear 10, and then coiled by the coiler 11 at 600 °C to obtain a hot-rolled strip with a thickness of 1.0 mm;

[0081] Continuous rolling and continuous annealing: After the hot-rolled strip is uncoiled on the continuous rolling and continuous annealing unit 12, it undergoes secondary cold rolling with intermediate annealing. The rolling reduction rate of the first cold rolling is 50%, and it is cold rolled to a thickness of 0.5 mm for the first time, and then undergoes intermediate annealing at 950 °C in an atmosphere of a hydrogen-argon mixture (25 vol% H2) for 2.5 min, and then cooled to room temperature at a rate not greater than 10 °C / s. The rolling reduction rate of the second cold rolling is 50%, and the second cold rolling rolls the intermediate annealed strip to a thickness of 0.25 mm; subsequently, continuous decarburization annealing is carried out at 1000 - 1100 °C in an atmosphere of a hydrogen-argon mixture (25 vol% H2) for 6 min, the heating rate is above 50 °C / s, and the cooling rate is below 80 °C / s to obtain a medium-high silicon non-oriented silicon steel thin strip.

[0082] The magnetic properties of the medium-high silicon non-oriented silicon steel thin strip of this embodiment are: the low-frequency iron loss P 1.5 / 50 is 2.35 W / kg, the medium-frequency iron loss P 1.0 / 400 is 11.16 W / kg, and the magnetic induction B 50 is 1.69 T.

[0083] The mechanical properties of the medium-high silicon non-oriented silicon steel thin strip of this embodiment are: the yield strength R p is 420 N / mm 2 , the tensile strength R m is 530 N / mm 2 , and the elongation is 17%.

[0084] The metallographic structure diagram of the cross-section of the casting and rolling strip of this embodiment is as shown in Figure 3 shown, and the Fe-Si phase diagram of the medium-high silicon non-oriented silicon steel thin strip of this embodiment is as shown inFigure 4 As shown in Figure 5 , the XRD spectrum of the cross-section of the cast-rolled strip in this embodiment is as follows: Figure 5 As can be seen from Figures 3 - 5 , this embodiment makes good use of the formation mechanism of the Fe-Si brittle structure and effectively avoids it through the sub-rapid solidification cooling rate, enabling the subsequent process to proceed normally. Figures 3 - 5

[0085] Example 2

[0086] Smelting: Molten steel is obtained through smelting. By mass percentage, the molten steel includes the following elements: 0.0023% C, 5.3% Si, 0.003% Al, 1.51% Mn, 0.01% P, 0.0030% S, Nb ≤ 0.001%, V ≤ 0.001%, Cr ≤ 0.001%, Ti ≤ 0.001%, and the balance is Fe and unavoidable impurity elements.

[0087] Casting: In a nitrogen atmosphere, the molten steel flows into the molten pool 4 through the tundish 1, the transition ladle 2, and the distributor 3. A composition detection device 14 is provided above the side of the molten pool 4, and then it enters the vertical twin-roll thin strip casting and rolling mill 5 for casting and rolling. The superheat of the molten steel in the molten pool 4 is 80 ± 10°C, the roll gap of the vertical twin-roll thin strip casting and rolling mill 5 is 1.8 ± 0.1 mm, and the casting and rolling process is carried out in a hot box filled with protective gas. The solidification cooling rate, casting and rolling speed, and the composition content of the protective gas in the hot box during the casting and rolling process are adjusted according to the silicon content in the molten steel to satisfy the following relationship: v 拉 = [1 - 0.25(w Si - 4.37)]V, N2 content = 20 + 50(w Si - 4.37)%, Ar content = 80 - 50(w Si - 4.37)%. The silicon content in the molten steel of this embodiment is 5.3%. Therefore, the solidification cooling rate needs to be controlled at 1674 - 1860°C / s, the casting and rolling speed needs to be controlled at 0.7675 m / s, and the protective gas in the hot box is a nitrogen-argon mixture. The volume content of nitrogen in this mixture is 66.5% and the volume content of argon is 33.5%, obtaining a cast-rolled strip 6 with a thickness of 1.8 ± 0.1 mm. Then, the cast-rolled strip 6 is uniformly cooled to 1100°C in a hot box filled with protective gas, the cooling time is less than 1.5 s, the cooling rate is less than 20°C / s, and the composition content of the protective gas in the hot box during the cooling process is the same as that during the casting and rolling process.

[0088] ​Hot rolling: When the temperature of the cast-rolled strip 6 is uniformly cooled to 1100 °C, the cast-rolled strip 6 enters the hot rolling mill stand 8 through the pinch roll 7 for single-pass hot rolling. The reduction ratio of hot rolling is about 17%. Then, it is cooled successively through the water-cooled roller table 9, trimmed by the flying shear 10, and coiled by the coiler 11 at 480 °C to obtain a hot-rolled strip with a thickness of 1.5 mm.

[0089] Continuous rolling and continuous annealing: After the hot-rolled strip is uncoiled on the continuous rolling and continuous annealing unit 12, it undergoes double cold rolling with intermediate annealing. The reduction ratio of the first cold rolling is about 67%, and it is cold-rolled to a thickness of 0.5 mm. Then, it is subjected to intermediate annealing at 950 °C in an atmosphere of a hydrogen-argon mixture (25 vol% H2) for 2.5 min, and then cooled to room temperature at a rate not exceeding 10 °C / s. The reduction ratio of the second cold rolling is 50%, and the intermediate annealed strip is cold-rolled to a thickness of 0.25 mm. Subsequently, continuous decarburization annealing is carried out at 1000 - 1100 °C in an atmosphere of a hydrogen-argon mixture (25 vol% H2) for 6 min, with a heating rate of more than 50 °C / s and a cooling rate of less than 80 °C / s to obtain a medium-high silicon non-oriented silicon steel thin strip.

[0090] The magnetic properties of the medium-high silicon non-oriented silicon steel thin strip in this embodiment are: the low-frequency iron loss P 1.5 / 50 is 2.03 W / kg, the medium-frequency iron loss P 1.0 / 400 is 10.06 W / kg, and the magnetic induction B 50 is 1.67 T.

[0091] The mechanical properties of the medium-high silicon non-oriented silicon steel thin strip in this embodiment are: the yield strength R p is 425 N / mm 2 , the tensile strength R m is 532 N / mm 2 , and the elongation is 17%.

[0092] Example 3

[0093] Smelting: Molten steel is obtained through smelting. By mass percentage, the molten steel includes the following elements: 0.0023% C, 5.3% Si, 0.003% Al, 1.51% Mn, 0.01% P, 0.0030% S, Nb ≤ 0.001%, V ≤ 0.001%, Cr ≤ 0.001%, Ti ≤ 0.001%, and the balance is Fe and inevitable impurity elements.

[0094] Casting: In a nitrogen atmosphere, the molten steel flows into the molten pool 4 through the tundish 1, the transition ladle 2, and the distributor 3. A composition detection device 14 is arranged above the side of the molten pool 4, and then it enters the vertical twin-roll strip casting and rolling mill 5 for casting and rolling. The superheat of the molten steel in the molten pool 4 is 80 ± 10 °C, the roll gap of the vertical twin-roll strip casting and rolling mill 5 is 2.3 ± 0.1 mm, and the casting and rolling process is carried out in a hot box filled with protective gas. According to the silicon content in the molten steel, the solidification cooling rate, the casting and rolling speed, and the composition content of the protective gas in the hot box during the casting and rolling process are adjusted to meet the following relationships: v 拉 =[1 - 0.25(w Si - 4.37)]V, N2 content = 20 + 50(w Si - 4.37)%, Ar content = 80 - 50(w Si - 4.37)%. The silicon content in the molten steel of this embodiment is 5.3%. Therefore, the solidification cooling rate needs to be controlled at 1674 - 1860 °C / s, the casting and rolling speed needs to be controlled at 0.7675 m / s, the protective gas in the hot box is a nitrogen-argon mixture, and the volume content of nitrogen in this mixture is 66.5% and the volume content of argon is 33.5%, obtaining a cast strip 6 with a thickness of 2.3 ± 0.1 mm; then the cast strip 6 is uniformly cooled to 1100 °C in a hot box filled with protective gas, the cooling time is less than 1.5 s, the cooling rate is less than 20 °C / s, and the composition content of the protective gas in the hot box during the cooling process is the same as that during the casting and rolling process;

[0095] Hot rolling: When the temperature of the cast strip 6 is uniformly cooled to 1100 °C, the cast strip 6 enters the hot rolling mill stand 8 through the pinch roll 7 for single-pass hot rolling. The reduction ratio of hot rolling is about 65%. Then it passes through the water-cooled roller table 9 for cooling and the flying shear 10 for trimming, and is coiled by the coiler 11 at 480 °C to obtain a hot-rolled strip with a thickness of 0.8 mm;

[0096] Continuous rolling and continuous annealing: After the hot-rolled strip is uncoiled on the continuous rolling and continuous annealing unit 12, it undergoes double cold rolling with intermediate annealing. The reduction ratio of the first cold rolling is about 44%, and it is cold-rolled to a thickness of 0.45 mm. Then it undergoes intermediate annealing at 950 °C in an atmosphere of hydrogen-argon mixture (25 vol% H2) for 2.5 min, and then is cooled to room temperature at a rate not greater than 10 °C / s. The reduction ratio of the second cold rolling is 44%, and the second cold rolling reduces the intermediate annealed strip to a thickness of 0.25 mm; subsequently, it undergoes continuous decarburization annealing at 1000 - 1100 °C in an atmosphere of hydrogen-argon mixture (25 vol% H2) for 6 min, the heating rate is above 50 °C / s, and the cooling rate is below 80 °C / s, obtaining a medium-high silicon non-oriented silicon steel thin strip.

[0097] The magnetic properties of the medium-high silicon non-oriented silicon steel strip in this embodiment are as follows: the low-frequency iron loss P 1.5 / 50 is 2.16 W / kg, and the medium-frequency iron loss P 1.0 / 400 is 11.02 W / kg, and the magnetic induction B 50 is 1.68 T.

[0098] The mechanical properties of the medium-high silicon non-oriented silicon steel strip in this embodiment are as follows: the yield strength R p is 422 N / mm 2 , the tensile strength R m is 533 N / mm 2 , and the elongation is 17%.

[0099] Comparative Example 1

[0100] Smelting: Molten steel is obtained through smelting. By mass percentage, the molten steel includes the following elements: 0.0023% C, 3.5% Si, 0.0029% Al, 1.48% Mn, 0.01% P, 0.0037% S, Nb ≤ 0.001%, V ≤ 0.001%, Cr ≤ 0.001%, Ti ≤ 0.001%, and the balance is Fe and unavoidable impurity elements;

[0101] Casting: In a nitrogen atmosphere, the molten steel is cast into a continuous casting strip with a thickness of 2.0 ± 0.1 mm through the ESP endless rolling technology; then the continuous casting strip is uniformly cooled to 1100°C in a hot box filled with protective gas;

[0102] Hot rolling: When the temperature of the continuous casting strip is uniformly cooled to 1100°C, the continuous casting strip enters a hot rolling mill for 6 passes of hot rolling. The reduction ratio of hot rolling is about 25%, and then it is coiled at 500°C by a coiler to obtain a hot rolled strip with a thickness of 1.5 mm;

[0103] Continuous rolling and continuous annealing: In the continuous rolling and continuous annealing unit process, the hot rolled strip undergoes two cold rollings with intermediate annealing. The reduction ratio of the first cold rolling is about 67%, and the first cold rolling is to a thickness of 0.50 mm. Then, intermediate annealing is carried out at 950°C in an atmosphere of a hydrogen-argon mixture (25 vol% H2) for 2.5 min, and then cooled to room temperature at a rate not exceeding 10°C / s. The reduction ratio of the second cold rolling is 50%, and the second cold rolling rolls the intermediate annealed strip to a thickness of 0.25 mm; subsequently, continuous decarburization annealing is carried out at 1000 - 1100°C in an atmosphere of a hydrogen-argon mixture (25 vol% H2) for 6 min, the heating rate is above 50°C / s, and the cooling rate is below 80°C / s to obtain the medium-high silicon non-oriented silicon steel strip.

[0104] The magnetic properties of the medium-high silicon non-oriented silicon steel strip in this comparative example are as follows: the low-frequency iron loss P 1.5 / 50 is 3.26 W / kg, and the medium-frequency iron loss P1.0 / 400 is 16.87 W / kg, magnetic induction B 50 is 1.58 T.

[0105] The mechanical properties of the medium-high silicon non-oriented silicon steel strip in this comparative example are as follows: yield strength R p is 275 N / mm 2 , tensile strength R m is 422 N / mm 2 , and the elongation is 30%.

Claims

1. A method for preparing a medium-high silicon non-oriented silicon steel strip, comprising the following steps: (1) smelting molten steel, wherein the molten steel comprises the following elements in percentage by mass: C≤0.004%, Si: 4.6~5.4%, Al≤0.01%, Mn: 0.50~1.75%, P≤0.02%, S≤0.005%, Nb≤0.002%, V≤0.002%, Cr≤0.002%, Ti≤0.002%, the balance is Fe and unavoidable impurity elements; (2) passing the molten steel through twin-roll thin strip casting to form a cast-rolled strip; (3) hot rolling the cast strip to obtain a hot rolled strip; (4) cold rolling the hot-rolled strip to obtain a cold-rolled strip, and then annealing to obtain the medium-high silicon non-oriented silicon steel thin strip.

2. The preparation method according to claim 1, wherein In step (2), the molten steel flows into the molten pool through the tundish, transition ladle and flow distributor in a nitrogen atmosphere, and then is formed into a cast strip by double-roll thin strip casting. The superheat of the molten steel in the molten pool is 70-100°C, and the roll gap during the double-roll thin strip casting process is 1.0-2.5mm.

3. The preparation method according to claim 1, wherein Step (2) includes: adjusting the solidification cooling rate during the twin-roll thin strip casting process according to the silicon content in the molten steel, so that the solidification cooling rate and the silicon content in the molten steel satisfy the following relationship: Among them, w Si It is the mass percentage of silicon in molten steel, without unit; is the solidification cooling rate, ℃ / s.

4. The preparation method according to claim 1, wherein Step (2) includes: adjusting the casting speed during the twin-roll thin strip casting process according to the silicon content in the molten steel, so that the casting speed and the silicon content in the molten steel satisfy the following relationship: 拉 =[1-0.25(w Si -4.37)]V, where w Si is the mass percentage of silicon in molten steel, unitless; V is 1m / s; v 拉 is the casting and rolling speed, m / s.

5. The preparation method according to claim 1, wherein Step (2) comprises: the twin-roller thin strip casting process is carried out in a hot box with a protective gas, and the protective gas component content of the hot box in the twin-roller thin strip casting process is adjusted according to the silicon content in the molten steel, and the protective gas of the hot box includes an argon-nitrogen mixed gas, so that the protective gas component content of the hot box and the silicon content in the molten steel satisfy the following relationship: N2 content = 20 + 50 (w Si -4.37)%Ar content=80-50(w Si -4.37%)%, among which w Si It is the mass percentage of silicon in molten steel and has no units.

6. The preparation method according to claim 5, wherein: Step (2) comprises: uniformly cooling the cast strip to 1000-1200°C in a hot box with protective gas, with a cooling time of less than 60s and a cooling rate of less than 20°C / s, wherein the content of the hot box protective gas component during the cooling process is the same as the content of the hot box protective gas component during the twin-roll thin strip casting process.

7. The preparation method according to claim 1, wherein Step (3) comprises: when the temperature of the cast strip drops to 850-1200° C., performing a single-pass hot rolling, wherein the reduction rate of the hot rolling is 15-75%, and after the hot rolling is completed, curling at 450-650° C. to obtain the hot-rolled strip; Preferably, in step (3), the thickness of the hot-rolled strip is 0.8 to 1.6 mm.

8. The preparation method according to claim 1, wherein Step (4) comprises: subjecting the hot-rolled strip to a first cold rolling, or a second cold rolling with intermediate annealing, to obtain the cold-rolled strip; Preferably, in step (4), the thickness of the cold-rolled strip is 0.1 to 0.35 mm.

9. The preparation method according to claim 8, wherein: In step (4), when secondary cold rolling with intermediate annealing is used, the reduction rate of the first cold rolling is less than 60%, and the first cold rolling is performed to a thickness of 0.5 to 0.75 mm; The intermediate annealing is performed in the following manner 1 or manner 2: manner 1: annealing is performed at 800-1000°C in a hydrogen-argon mixed gas atmosphere for 2-8 minutes, and then cooled to room temperature; manner 2: annealing is performed at 1000-1100°C in a wet hydrogen-nitrogen mixed gas atmosphere for 1-6 minutes, the dew point of the wet hydrogen-nitrogen mixed gas atmosphere is dp=35-45°C, the temperature of water in the atmosphere is 60-65°C, and the ratio of the partial pressure of water to the partial pressure of hydrogen in the atmosphere is P H2O / P H2 =0.35~0.45, then cooled to room temperature under dry hydrogen-nitrogen mixed gas atmosphere, the dew point dp of the dry hydrogen-nitrogen mixed gas atmosphere is less than -20°C, the temperature of the dry hydrogen-nitrogen mixed gas atmosphere is room temperature, and the ratio of the partial pressure of water to the partial pressure of hydrogen in the atmosphere is P H2O / P H2 =0.03; The reduction rate of the second cold rolling is 10 to 50%, and the second cold rolling is performed to a thickness of 0.1 to 0.35 mm.

10. The preparation method according to claim 1, wherein: In step (4), the annealing includes one or both of continuous annealing and hood annealing; The continuous annealing conditions include: annealing at 1000-1200°C in a hydrogen-argon mixed gas atmosphere for 2-10 minutes, a heating rate of 50°C / s or more, and a cooling rate of 80°C / s or less; The hood annealing conditions include: annealing at 900-1200° C. in a hydrogen-argon mixed gas atmosphere for 0.1-1 h, and then cooling to room temperature at a rate of less than 10° C. / s.

11. The preparation method according to claim 10, wherein: Step (4) further comprises: selecting to perform continuous annealing, or hood annealing, or continuous annealing and hood annealing according to the product index requirements; preferably, the product index includes one or more of grain size, texture state and magnetic properties; Preferably, in step (4), after the cold-rolled strip is continuously annealed, if one or more of the grain size, texture state and magnetic properties of the product do not reach a predetermined value, or if one or more of the grain size, texture state and magnetic properties of the product need to be further adjusted, further hood annealing is performed.

12. The preparation method according to claim 10, wherein: Step (4) further comprises: coating the cold-rolled strip after continuous annealing and / or hood annealing to obtain the medium-high silicon non-oriented silicon steel thin strip; Preferably, the coating has a thickness of 0.05 to 0.18 mm.

13. A medium-high silicon non-oriented silicon steel thin strip, which is prepared by the method for preparing a medium-high silicon non-oriented silicon steel thin strip according to any one of claims 1 to 12.

14. Use of the medium-high silicon non-oriented silicon steel strip according to claim 13 in automobile drive motors.

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