Method for preparing non-oriented silicon steel for driving motor by using copper-containing molten iron

Abstract

The invention discloses a method for preparing non-oriented silicon steel for a driving motor by using copper-containing molten iron. The method comprises the following steps: preparing low-copper thin-specification non-oriented silicon steel by using molten iron with Cu being less than 0.04%, or preparing high-copper high-strength non-oriented silicon steel by using molten iron with Cu being greater than or equal to 0.04%. According to the method, selective production is performed according to the Cu content in the molten iron. The harmless treatment of Cu is carried out through the cooperation of a low-copper molten iron whole-flow process, so that the low-copper thin-specification non-oriented silicon steel is prepared. And the high-copper high-strength non-oriented silicon steel is prepared by further increasing the Cu content. And the magnetic property and mechanical property requirements of the copper-containing molten iron for preparing the non-oriented silicon steel for the stator and the rotor of the driving motor can be met.

Description

Technical Field

[0001] The present invention relates to the field of metallurgical technology, and in particular to a method for preparing non-oriented silicon steel for a drive motor by using copper-containing molten iron. Background Art

[0002] At present, metal materials with high copper content have relatively low requirements for the magnetic and mechanical properties of the finished products. For example, Chinese patents CN110157972A, CN116536587A and CN116356214A mainly produce antibacterial and anti-corrosion materials through the Cu element content. Chinese patent CN103757543A invents a rare earth-reinforced copper-containing precipitation-reinforced steel and its preparation method. By controlling the alloy composition and heat treatment process, the aging precipitation of Cu is used to achieve the effect of strengthening the base alloy steel. Regarding the application of Cu in silicon steel production, a large number of scholars have conducted research on its influence on the organization, texture, magnetic properties and mechanical properties of silicon steel, but its control research in production is almost missing. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method for preparing non-oriented silicon steel for drive motor using copper-containing molten iron.

[0004] The present invention solves the technical problem by adopting the following technical solutions.

[0005] The invention provides a method for preparing non-oriented silicon steel for driving motor by using copper-containing molten iron, which comprises: preparing low-copper thin-gauge non-oriented silicon steel by using molten iron with Cu<0.04%, or preparing high-copper high-strength non-oriented silicon steel by using molten iron with Cu≥0.04%.

[0006] The present invention also provides a low-copper thin-gauge non-oriented silicon steel prepared by the above method, wherein the low-copper thin-gauge non-oriented silicon steel comprises the following chemical components in mass percentage: 3.2-3.3wt.% Si, 0.9-1.0wt.% Al, 0.3-0.4wt.% Mn, 0.0010-0.0015wt.% S, 0.0010-0.0018wt.% Ti, 0.01-0.05wt.% Cu, 0.06wt.% Sn, and the rest is Fe and unavoidable impurities.

[0007] The present invention also provides a high-copper and high-strength non-oriented silicon steel prepared by the above method, wherein the high-copper and high-strength non-oriented silicon steel comprises the following chemical components by mass percentage: 3.4-3.6wt.% Si, 0.7-0.8wt.% Al, 0.4-0.6wt.% Mn, 0.0010-0.0015wt.% S, 0.0010-0.0018wt.% Ti, 0.75-1.5wt.% Cu, 0.06wt.% Sn, and the rest is Fe and unavoidable impurities.

[0008] The present invention also provides an application of the above-mentioned low-copper, thin-gauge non-oriented silicon steel in the preparation of a stator for a new energy vehicle drive motor, or an application of the above-mentioned high-copper, high-strength non-oriented silicon steel in the preparation of a rotor for a new energy vehicle drive motor.

[0009] The present invention has the following beneficial effects:

[0010] The present invention provides a method for preparing non-oriented silicon steel for driving motors by using copper-containing molten iron, which comprises: preparing low-copper thin-gauge non-oriented silicon steel by using molten iron with Cu < 0.04%, or preparing high-copper high-strength non-oriented silicon steel by using molten iron with Cu ≥ 0.04%. When the copper content of molten iron is low, the adverse effect of Cu in silicon steel is reduced by controlling the Cu content in molten steel and process control, thereby improving the magnetic properties of silicon steel. When the copper content of molten iron is high, an appropriate amount of Cu content is added, and the process treatment is coordinated to improve the strength of silicon steel by the precipitation phase of Cu, while ensuring the good magnetic properties of non-oriented silicon steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0012] Figure 1 Low copper thin gauge non-oriented silicon steel structure for drive motor stator;

[0013] Figure 2 High copper and high strength non-oriented silicon steel structure for driving motor rotor;

[0014] Figure 3 Copper precipitation phase in high copper and high strength non-oriented silicon steel. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0016] In view of the problem that the existing high-Cu molten iron is not conducive to the organization, texture and magnetic properties of high-grade non-oriented silicon steel, the present invention provides a method for preparing non-oriented silicon steel using copper-containing molten iron, including the method of harmlessly treating Cu through the whole process of low-copper molten iron to prepare low-copper thin-gauge non-oriented silicon steel; and preparing high-copper and high-strength non-oriented silicon steel by further increasing the Cu content. Different post-process matching treatments are carried out according to the Cu content to improve the magnetic and mechanical properties of the non-oriented silicon steel, improve the availability of copper-containing molten iron, reduce the adverse effects of copper on non-oriented silicon steel, and further improve the performance of non-oriented silicon steel for drive motors.

[0017] The following is a detailed description of a method for preparing non-oriented silicon steel for a drive motor by using copper-containing molten iron provided in an embodiment of the present invention.

[0018] In a first aspect, an embodiment of the present invention provides a method for preparing non-oriented silicon steel for drive motors using copper-containing molten iron, which comprises: preparing low-copper thin-gauge non-oriented silicon steel using molten iron with Cu < 0.04%, or preparing high-copper and high-strength non-oriented silicon steel using molten iron with Cu ≥ 0.04%.

[0019] Cu, as an important alloying element in steel, not only has an important influence on the microstructure, mechanical properties and corrosion resistance, but also has antibacterial and bactericidal effects after proper heat treatment. It is generally believed that adding an appropriate amount of Cu element to non-oriented silicon steel and making it concentrate on the surface of the steel plate can improve the corrosion resistance of the steel, while also increasing the resistivity and reducing the iron loss. Under proper annealing process, the occupancy of the {100} and {110} surface textures can be increased, thereby increasing the magnetic induction intensity. However, when the copper content is high (1100℃~1200℃) during heat treatment, liquid copper will be formed between the metal oxide layer and the metal matrix of the material, and it will penetrate into the grain boundary and cool and precipitate, causing intergranular cracking and embrittlement of the material.

[0020] For the production of non-oriented silicon steel with copper-containing molten iron, it is usually necessary to reduce the copper content in the molten steel to avoid the formation of a large amount of (Cu, Mn) during the hot rolling process. 1.8 S and (Mn, Cu)S particles increase the coercivity and hysteresis loss of silicon steel and make the steel brittle. The Cu content in molten steel is mainly brought in by molten iron and scrap steel. Under the premise that it is difficult to optimize the raw materials for ironmaking, the current method of removing Cu from steel is difficult to apply industrially. Therefore, reducing the use of copper-containing scrap steel is the key to reducing the Cu content in molten steel.

[0021] At present, the Cu content in steel has very limited effect on improving the magnetic properties of non-oriented silicon steel. Due to the high properties and strengthening effect of the Cu precipitation phase itself, it has good plastic coordination with the surrounding environment under complex stress and strain conditions. At the same time, it is not easy to generate high stress concentration areas or cracks that cause material failure near the Cu precipitation phase, which is beneficial to improve the service life of steel. The drive motor has higher requirements on the mechanical properties of non-oriented silicon steel. Therefore, it is necessary to use the strengthening effect of Cu precipitation on ferrite to improve the strength of steel.

[0022] Based on the existing problems in the application of Cu element in non-oriented silicon steel, the embodiment of the present invention provides a method for preparing non-oriented silicon steel for drive motor using copper-containing molten iron, which uses copper-containing molten iron as the source of molten iron, controls the Cu content in molten steel, and reduces the adverse effects of Cu in silicon steel through process control, thereby improving the magnetic properties of silicon steel. In addition, when the copper content of molten iron is high, an appropriate amount of Cu content is added, and the process is coordinated to improve the strength of silicon steel by Cu precipitation phase, while ensuring good magnetic properties of non-oriented silicon steel.

[0023] The above method uses copper-containing molten iron as the source of molten iron, effectively expands the source of raw materials for non-oriented silicon steel production, reduces excessive pickiness on molten iron composition in industrial production, and solves the problem of being unable to produce non-oriented silicon steel due to excessively high Cu content brought into the raw materials. By selecting the more suitable type of non-oriented silicon steel to be produced based on the composition of molten iron, the diversity of silicon steel can be fully realized.

[0024] In some optional implementations, the preparation process of low-copper thin-gauge non-oriented silicon steel is as follows: molten iron selection - KR desulfurization - converter smelting - CAS top slag modification - RH refining - casting - hot rolling - normalizing - cold rolling - annealing, wherein:

[0025] (1) Low copper: Reduce the Cu content in molten steel by selecting molten iron and using high-quality scrap steel;

[0026] (2) Desulfurization: Reduce the sulfur content in molten steel through KR process adjustment, converter charge optimization, CAS top slag modification, and RH desulfurization process optimization;

[0027] (3) Ti reduction: The Ti content in molten steel can be reduced by selecting low-Ti molten iron, controlling the amount of slag in the converter, modifying the top slag during refining, and selecting alloy components;

[0028] (4) Oxygen control: Control the refining process to improve cleanliness, secondary oxidation and strictly protect casting control to reduce the TO content in molten steel;

[0029] (5) The thickness of hot-rolled plate is reduced;

[0030] (6) Normalization rapid heating + high temperature short time annealing;

[0031] In some optional implementations, in step (1): the Cu content in the molten iron is less than 0.04%, and the Cu content in the molten steel is below 0.07% after adding the scrap steel.

[0032] In some optional embodiments, in step (2): the KR desulfurization process is adjusted to select a high-efficiency desulfurizer of lime + fluorite + aluminum slag, and the slag removal rate is increased to more than 98%; the converter charge selects low-sulfur auxiliary materials, and the sulfur content of the molten steel after adding the molten steel is required to be less than 10ppm; the CAS top slag is reformed, and the high-aluminum reforming agent Al40 is used for top slag reforming at a dosage of 1.5kg / t molten steel; the RH desulfurization process is optimized, and the A.KTB gun and powder spray desulfurization are selected, and the desulfurizer selects a calcium aluminate desulfurizer;

[0033] In some optional embodiments, in step (3), the Ti content of low-titanium ferrometallurgy is below 0.07%; the amount of slag in the converter is below 0.8 kg / t molten steel or the steel is retained for smelting (i.e., no slag is dumped); the alloy is low-titanium high-purity ferrosilicon, and the Ti content is 0.015%±0.005%.

[0034] In some optional embodiments, in step (4), the RH refining process: the alloy selects low-titanium high-purity ferrosilicon with a Ti content of 0.012%±0.005%; the RH desulfurization process uses A.KTB gun powder spray desulfurization, and the desulfurizer selects a calcium aluminate desulfurizer; the total oxygen content of the molten steel after refining is ≤0.0012%; the casting process includes: controlling the columnar crystal rate of the produced continuous casting billet to be 55%~65%.

[0035] In some optional embodiments, in step (5), the thickness of the hot-rolled plate is reduced to 1.8 mm, and the thickness after one cold rolling is 0.2 mm.

[0036] In some optional embodiments, in step (6), the normalization fast heating process is: in a N2 protective atmosphere, the temperature is increased to 960±3℃ at a heating rate of 20℃ / s and kept warm for 115-125s; the high temperature short time annealing process is: in a N2:H2 protective atmosphere of 2:1, the temperature is kept at 990±3℃ for 115-125s.

[0037] The method for preparing low-copper thin-gauge non-oriented silicon steel provided in an embodiment of the present invention uses molten iron with Cu < 0.04% to prepare low-copper thin-gauge non-oriented silicon steel. The method reduces the source of Cu through blast furnace ore matching + molten iron selection + high-quality scrap steel, controls the Cu content in molten steel, and realizes harmless treatment of Cu by reducing the content of other elements (S, Ti, TO), so as to reduce the adverse effect of Cu on the magnetic properties of non-oriented silicon steel.

[0038] Through refined industrial production process control, the thickness of hot-rolled plates is reduced to reduce the deterioration of annealing texture caused by excessive cold rolling reduction. The combined control of normalization rapid heating + high-temperature short-time annealing is adopted to increase the stable organization and favorable texture content of the finished plates. Without changing the composition of molten steel, the non-oriented silicon steel used for drive motors is upgraded by one grade.

[0039] In a second aspect, an embodiment of the present invention provides a method for preparing low-copper thin-gauge non-oriented silicon steel using copper-containing molten iron prepared by the above method, wherein the low-copper thin-gauge non-oriented silicon steel comprises the following chemical components in mass percentage: 3.2-3.3wt.% Si, 0.9-1.0wt.% Al, 0.3-0.4wt.% Mn, 0.0010-0.0015wt.% S, 0.0010-0.0018wt.% Ti, 0.01-0.05wt.% Cu, 0.06wt.% Sn, and the rest is Fe and unavoidable impurities.

[0040] In some optional embodiments, the Cu content in the low copper thin gauge non-oriented silicon steel is ≤ 0.015%;

[0041] In some optional embodiments, the S content in the low copper thin gauge non-oriented silicon steel is ≤ 0.0013%;

[0042] In some optional embodiments, the Ti content in the low copper thin gauge non-oriented silicon steel is ≤ 0.0014%.

[0043] In some optional embodiments, the magnetic induction intensity B of 0.2 mm low copper thin gauge non-oriented silicon steel is 50 is 1.666T, iron loss P 1.5 / 50 and P 10 / 400 They are 1.95W / kg and 10.88W / kg respectively.

[0044] In a third aspect, an embodiment of the present invention provides a method for preparing high-copper and high-strength non-oriented silicon steel, comprising the following steps: high-copper molten steel → adjusting the composition of molten steel → casting → hot rolling → normalizing → cold rolling → complete recrystallization annealing + aging treatment.

[0045] In some optional embodiments, the process of adjusting the composition of molten steel includes: adding pure copper blocks to increase the Cu content in the molten steel when tapping steel from a converter. Since it is difficult to change the Cu content in the molten steel in subsequent processes, after adding the copper blocks at this time, the Cu content in the molten steel should be the Cu content required for the finished product.

[0046] In some optional embodiments, the normalization step includes: in a N2 atmosphere, heating the temperature to 960±3°C at a heating rate of 20°C / s and keeping the temperature for 115-125s.

[0047] In some optional embodiments, the cold rolling process includes: cold rolling to 0.3 mm using a twenty-high rolling mill.

[0048] In some optional embodiments, the complete recrystallization annealing process includes: keeping the temperature at 990±3° C. for 115-125 seconds in a protective atmosphere of N2:H2 (2:1).

[0049] In some optional implementations, the aging treatment process includes: selecting an aging temperature of 550° C. and a time of 20 min.

[0050] The embodiment of the present invention provides a method for preparing high-copper and high-strength non-oriented silicon steel, which uses molten iron with Cu≥0.04% to prepare high-copper and high-strength non-oriented silicon steel. As the Cu content in molten iron is too high and the process of harmless treatment of copper to magnetic properties is complicated, the precipitation strengthening effect of Cu is used to produce high-strength non-oriented silicon steel, and the Cu in the molten iron is fully utilized, the amount of Cu alloy added is reduced, and cost reduction and efficiency improvement are achieved.

[0051] In addition, by controlling the normalizing process, the problem of high-copper non-oriented silicon steel being easy to harden or become brittle after normalizing is reduced, and through complete recrystallization annealing + precipitation aging treatment, the magnetic properties of the finished plate are further guaranteed to meet the current use requirements of drive motor rotors.

[0052] In a fourth aspect, an embodiment of the present invention provides a high-copper and high-strength non-oriented silicon steel prepared by the above method, the high-copper and high-strength non-oriented silicon steel comprising the following chemical components in mass percentage: 3.4-3.6wt.% Si, 0.7-0.8wt.% Al, 0.4-0.6wt.% Mn, 0.0010-0.0015wt.% S, 0.0010-0.0018wt.% Ti, 0.75-1.5wt.% Cu, 0.06wt.% Sn, and the rest is Fe and unavoidable impurities.

[0053] In some optional implementations, the Cu content in the high-copper and high-strength non-oriented silicon steel is 1.0-1.5%.

[0054] In some optional embodiments, the magnetic induction intensity B of 0.3 mm high copper high strength non-oriented silicon steel is 50 is 1.648T, iron loss P 1.5 / 50 and P 10 / 400 They are 2.28W / kg and 15.67W / kg respectively, and the tensile strength R m Reaching 735.7MPa.

[0055] In a fifth aspect, an embodiment of the present invention provides an application of the above-mentioned low-copper, thin-gauge non-oriented silicon steel in the preparation of a stator for a new energy vehicle drive motor, or an application of the above-mentioned high-copper, high-strength non-oriented silicon steel in the preparation of a rotor for a new energy vehicle drive motor.

[0056] The present invention will be further described below in conjunction with the embodiments.

[0057] The embodiment of the present invention provides a method for preparing low-copper thin-gauge non-oriented silicon steel for stators of new energy vehicle drive motors using copper-containing molten iron, comprising the following steps: ore matching and smelting molten iron in a blast furnace, when the Cu content of the prepared molten iron is lower than 0.04%, desulfurization is performed by a KR process, low-copper and low-sulfur scrap steel and steelmaking raw and auxiliary materials are selected, the molten iron is further smelted in a converter, top slag is modified before refining, and RH and rare earth treatment are used for further refining and impurity removal. After smelting, the chemical composition of the molten steel is: 3.2-3.3wt.%Si, 0.9-1.0wt.%Al, 0.3-0.4wt.%Mn, 0.0010-0.0015wt.%S, 0.0010-0.0018wt.%Ti, 0.010-0.065wt.%Cu, 0.060wt.%S, and the rest is Fe and unavoidable impurities. The columnar crystal rate of the ingot cast by molten steel is controlled at 55% to 65%, and hot rolled into a 1.8mm thick hot-rolled plate. Then, a normalizing process is adopted in which the temperature is increased to 960℃ and kept warm for 2min at a heating rate of 20℃ / s in a N2 protective atmosphere. After cold rolling to 0.2mm, an annealing process is carried out at 990℃ and kept warm for 2min in a N2:H2 protective atmosphere of 2:1, and then various properties are tested under standard conditions.

[0058] The embodiment of the present invention provides a method for preparing high-copper and high-strength non-oriented silicon steel for a new energy vehicle drive motor rotor by using copper-containing molten iron, comprising the following steps: by detecting the composition of the molten iron, when the Cu content is higher than 0.04%, after KR desulfurization and converter smelting, alloying is performed to adjust the composition of the molten steel to: 3.4-3.6wt.% Si, 0.7-0.8wt.% Al, 0.4-0.6wt.% Mn, 0.0010-0.0015wt.% S, 0.0010-0.0018wt.% Ti, 0.80-1.5wt.% Cu, 0.060wt.% Sn, and the rest is Fe and unavoidable impurities. The ingot was hot rolled into a 1.8 mm thick hot-rolled plate, and subjected to a normalizing process in a N2 protective atmosphere, where the temperature was raised to 960°C at a heating rate of 20°C / s and kept warm for 2 min. After cold rolling to 0.3 mm, it was annealed at 990°C for 2 min in a N2:H2 protective atmosphere of 2:1. The aging temperature was 550°C for 20 min, and the performance was tested under standard conditions.

[0059] Example 1

[0060] A method for preparing low-copper thin-gauge non-oriented silicon steel for a drive motor stator, the production steps are as follows:

[0061] (1) The Cu content in the blast furnace iron water is less than 0.04%, and the Ti content is 0.037%. A high-efficiency desulfurizer of lime + fluorite + aluminum slag is used, and the slag removal rate is increased to 98% or above. After desulfurization, the sulfur content of the molten steel is 0.0010%.

[0062] (2) Converter smelting process: low-sulfur auxiliary materials and high-quality scrap steel are selected, and the steel retention smelting operation is adopted. The sulfur content in the molten steel is 0.0020% after smelting. The CAS station uses a high-aluminum reforming agent Al40 at a dosage of 1.5 kg / t of molten steel for top slag reforming. The RH refining desulfurization process uses A.KTB gun and powder spray desulfurization, and the desulfurizer is a calcium aluminate desulfurizer. The sulfur content in the molten steel after refining is 0.001%.

[0063] (3) The target columnar crystal content of the continuous casting billet is 55% to 65%; the billet is hot rolled to 1.8 mm; and the normalizing process is as follows: in a N2 protective atmosphere, the temperature is increased to 960°C at a heating rate of 20°C / s and kept at this temperature for 2 min.

[0064] (4) The normalized plate is cold rolled to 0.2 mm; the annealing process is: in a protective atmosphere of N2:H2 of 2:1, the temperature is kept at 990°C for 2 min.

[0065] The composition, magnetic and mechanical properties of the finished non-oriented silicon steel plate were tested, as shown in Table 1 and Example 1 in Table 2.

[0066] Embodiments 2 to 4

[0067] A method for preparing low-copper thin-gauge non-oriented silicon steel for a drive motor stator, wherein the specific steps of each embodiment are the same as those of embodiment 1, and the only difference is that the Cu content in the molten iron used is different.

[0068] The components of the non-oriented silicon steel finished plates of various embodiments are shown in Table 1, and the magnetic and mechanical properties are shown in Table 2.

[0069] Comparative Example 1

[0070] The production steps of a low-copper thin-gauge non-oriented silicon steel for a drive motor stator are basically the same as those in Example 1, except that:

[0071] (1) The Ti content in blast furnace hot metal is 0.083%;

[0072] (2) After the converter smelting is completed, the slag is removed normally during the steel tapping process; high-purity ferrosilicon with a Ti content of 0.045% is selected during the alloying process. The main difference in the composition of the finished non-oriented silicon steel plate of this comparative example is that the Ti content is 0.074%. The magnetic and mechanical properties are shown in Table 2.

[0073] Comparative Example 2

[0074] The production steps of a low-copper thin-gauge non-oriented silicon steel for a drive motor stator are basically the same as those in Example 1, except that:

[0075] (1) The converter smelting and subsequent refining process uses conventional auxiliary materials, slag materials and process operations, and the sulfur content of the molten steel after smelting is 0.012%;

[0076] (2) Adjust the desulfurization process of the RH refining process and select conventional (CaO+CaF2 system) desulfurizer, and the desulfurization content of the molten steel is 0.0030% after the refining and desulfurization.

[0077] After testing the finished non-oriented silicon steel plate of this comparative example, the main difference in composition is that the S content is 0.0030%. The magnetic and mechanical properties are shown in Table 2.

[0078] Comparative Example 3

[0079] The production steps and components of a low-copper thin-gauge non-oriented silicon steel for a drive motor stator are substantially the same as those of Example 1, except that:

[0080] (1) The ingot was hot-rolled into a 2.0 mm hot-rolled plate by a normalizing process in a N2 atmosphere at 950°C for 3 min;

[0081] (2) An annealing process is adopted in an atmosphere of N2:H2 of 3:1 at 940°C for 3 minutes.

[0082] The composition of the finished non-oriented silicon steel plate is shown in Table 1, and the magnetic and mechanical properties are shown in Table 2.

[0083] Example 5

[0084] A method for preparing high-copper and high-strength non-oriented silicon steel for a drive motor rotor, the production steps are as follows:

[0085] High copper molten steel → adjust molten steel composition → casting → hot rolling → normalizing → cold rolling → complete recrystallization annealing + aging treatment

[0086] (1) The Cu content in molten iron in blast furnace is above 0.04%. After KR desulfurization and converter smelting, pure copper blocks are used to perform Cu alloying to adjust the Cu content in molten steel to 0.80%;

[0087] (2) Casting and hot-rolling the molten steel into a 1.8 mm thick hot-rolled plate; heating the plate to 960°C at a heating rate of 20°C / s in a N2 atmosphere and keeping the temperature for 2 min.

[0088] (3) After pickling and cold rolling to 0.3 mm, the steel was annealed at 980 °C for 3 min in a protective atmosphere of N2:H2 (2:1), and then aged at 550 °C for 20 min.

[0089] The composition, magnetic and mechanical properties of the finished non-oriented silicon steel plate were tested, as shown in Table 1 and Table 2, which is Example 5.

[0090] Embodiments 6 to 9

[0091] A method for preparing high-copper and high-strength non-oriented silicon steel for a drive motor rotor, wherein the specific steps of each embodiment are the same as those of embodiment 5. The only difference is that the Cu content in the molten steel used is different.

[0092] The composition of the non-oriented silicon steel finished plate is shown in Table 1, and the magnetic and mechanical properties are shown in Table 2.

[0093] Comparative Example 4

[0094] A high-copper, high-strength non-oriented silicon steel for a drive motor rotor, whose composition and preparation method are substantially the same as those of Example 8, except that:

[0095] The molten steel is cast and hot-rolled into a 2.3mm thick hot-rolled plate. After pickling, the end point of cold rolling is 0.2mm. When it is rolled to about 0.3mm, the cold-rolled plate will crack seriously.

[0096] Table 1 Main chemical components

[0097] Case Si, % Al，％ Mn, % S，％ Ti, % Cu, % Sn, % Example 1 3.243 0.9042 0.313 0.0013 0.0014 0.015 0.060 Example 2 3.258 0.9989 0.321 0.0019 0.0016 0.025 0.0605 Example 3 3.288 0.9997 0.318 0.0017 0.0015 0.042 0.0603 Example 4 3.304 0.9019 0.336 0.0020 0.0014 0.053 0.0602 Comparative Example 1 3.253 0.9360 0.0319 0.0014 0.0074 0.051 0.0611 Comparative Example 2 3.269 0.8042 0.313 0.0031 0.0023 0.049 0.0633 Comparative Example 3 3.242 0.9041 0.313 0.0018 0.0024 0.045 0.0600 Example 5 3.576 0.7959 0.511 0.0024 0.0024 0.755 0.0610 Example 6 3.486 0.8059 0.525 0.0025 0.0023 0.851 0.0603 Example 7 3.462 0.7875 0.527 0.0025 0.0023 0.898 0.0606 Example 8 3.479 0.7563 0.570 0.0026 0.0024 1.006 0.0604 Example 9 3.526 0.7975 0.554 0.0024 0.0023 1.469 0.0603

[0098] Table 2 Test results

[0099] Case Thickness, mm <![CDATA[P 1.5 / 50 ,W / kg]]> <![CDATA[P 1.0 / 400 ,W / kg]]> <![CDATA[B 50 ,T]]> <![CDATA[R m ,MPa]]> Example 1 0.2 1.95 10.88 1.666 551.4 Example 2 0.2 2.08 10.97 1.668 539.2 Example 3 0.2 2.05 10.98 1.664 544.5 Example 4 0.2 1.99 10.92 1.662 536.4 Comparative Example 1 0.2 2.11 11.77 1.659 561.4 Comparative Example 2 0.2 2.15 11.67 1.657 559.5 Comparative Example 3 0.2 2.19 11.99 1.655 541.1 Example 5 0.3 2.19 14.67 1.658 670.5 Example 6 0.3 2.22 15.10 1.654 696.1 Example 7 0.3 2.25 15.34 1.651 702.7 Example 8 0.3 2.25 15.64 1.652 711.5 Example 9 0.3 2.28 15.67 1.648 735.7

[0100] It can be seen from Table 1 and Table 2 that the stator of the drive motor mainly based on magnetic properties uses low-copper thin-gauge non-oriented silicon steel, and the magnetic properties of the product produced in Example 1 are the best, and the magnetic induction intensity B 50 is 1.666T, iron loss P 1.5 / 50 and P 10 / 400 The mechanical properties of the non-oriented silicon steel for driving motors are prepared by high-copper molten iron, and the mechanical properties of the product produced in Example 1 are the best. The magnetic induction intensity B 50 is 1.648T, iron loss P 1.5 / 50 and P 10 / 400 They are 2.28W / kg and 15.67W / kg respectively, and the tensile strength R m Reaching 735.7Mpa.

[0101] Combination Figure 1 and Figure 2It can be seen that the 0.2mm low copper thin gauge non-oriented silicon steel of Example 1 has a more uniform structure, a smaller proportion of magnetically unfavorable oriented grains (blue), and a larger proportion of magnetically favorable oriented grains (red). The process adjustment reduces the influence of Cu on the structure and magnetic properties of the finished non-oriented silicon steel. The 0.3mm high copper high strength non-oriented silicon steel of Example 9 has an uneven grain size distribution. Cu precipitates limit the uniform growth of the structure and inhibit the grains from deflecting in the magnetically favorable direction, reducing the grain size. Although it is not conducive to the improvement of magnetic properties, it can further improve the mechanical properties. Figure 3 The distribution of Cu precipitates shown in the figure is 2-3 nm Cu precipitates. Combined with electron diffraction analysis, the Cu-rich precipitates are bcc structures, which are completely coherent with the α matrix. The modulus difference and coherent strain of the nanoscale Cu precipitates are the main reasons for precipitation strengthening.

[0102] As can be seen from the above, the embodiment of the present invention provides a method for preparing non-oriented silicon steel for drive motor using copper-containing molten iron. The present invention also provides two types of non-oriented silicon steel for drive motor of new energy vehicle, one is low copper and thin gauge non-oriented silicon steel for drive motor stator, and the other is high copper and high strength non-oriented silicon steel for drive motor rotor. It is selectively produced according to the high and low Cu content in molten iron. Wherein: the preparation method of low-copper thin-gauge non-oriented silicon steel for drive motor stator comprises: on the basis of narrow composition control of main alloy elements, by controlling [S], reducing [Ti], controlling TO and post-process optimization and other operations, the low-copper thin-gauge non-oriented silicon steel comprises the following chemical compositions by mass percentage: 3.2-3.3wt.% Si, 0.9-1.0wt.% Al, 0.3-0.4wt.% Mn, 0.0010-0.0015wt.% S, 0.0010-0.0018wt.% Ti, 0.010-0.050wt.% Cu, 0.060wt.% Sn, and the rest are Fe and unavoidable impurities. The preparation method of high-copper and high-strength non-oriented silicon steel for driving motor rotors includes: by selecting high-copper molten iron, adding copper blocks to the converter steel, and then combining low-quantity treatment of inclusions and harmful elements in the steelmaking continuous casting process, complete recrystallization annealing and aging treatment, reducing the adverse effects of copper on magnetic properties while improving strength, low-copper thin-gauge non-oriented silicon steel includes the following chemical components in mass percentage: 3.4-3.6wt.% Si, 0.7-0.8wt.% Al, 0.4-0.6wt.% Mn, 0.0010-0.0015wt.% S, 0.0010-0.0018wt.% Ti, 0.8-1.5wt.% Cu, 0.060wt.% Sn, and the rest is Fe and unavoidable impurities. The low-copper thin-gauge non-oriented silicon steel for the stator provided in the embodiment of the present invention has excellent magnetic properties of the 0.2mm finished product through the coordinated control of the whole process process, and the magnetic induction intensity B 50 is 1.666T, iron loss P 1.5 / 50 and P 10 / 400The rotor uses high-copper and high-strength non-oriented silicon steel. Through the synergy of the whole process and the ε-Cu precipitation strengthening effect, the 0.3mm finished product has excellent magnetic properties and mechanical properties, and the magnetic induction intensity B 50 is 1.648T, iron loss P 1.5 / 50 and P 10 / 400 They are 2.28W / kg and 15.67W / kg respectively, and the tensile strength R m It reaches 735.7MPa, which can meet the magnetic and mechanical property requirements of copper-containing molten iron for preparing non-oriented silicon steel for drive motor stators and rotors.

[0103] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing non-oriented silicon steel for driving motor using copper-containing molten iron, characterized in that: The method comprises: using molten iron with Cu less than 0.04% to prepare low-copper thin-gauge non-oriented silicon steel, or using molten iron with Cu greater than or equal to 0.04% to prepare high-copper high-strength non-oriented silicon steel.

2. The method according to claim 1, characterized in that The method for preparing low-copper thin-gauge non-oriented silicon steel using molten iron with Cu < 0.04% comprises: on the basis of narrow composition control of main alloy elements, harmless treatment of Cu is performed by controlling [S], reducing [Ti], controlling TO and optimizing post-processing to prepare low-copper thin-gauge non-oriented silicon steel.

3. The method according to claim 2, characterized in that The process of preparing low-copper thin-gauge non-oriented silicon steel using molten iron with Cu < 0.04% includes: molten iron selection → KR desulfurization → converter smelting → CAS top slag reforming → RH refining → casting → hot rolling → fast heating normalization → primary cold rolling → high temperature short time annealing; Preferably, the molten iron selection process comprises: controlling the Cu content in the molten iron to be less than 0.04% and the Ti content to be less than 0.07%; Preferably, the KR desulfurization process includes: selecting a high-efficiency desulfurization agent of lime + fluorite + aluminum slag, and increasing the slagging rate to more than 98%; Preferably, the converter smelting process includes: selecting low-sulfur auxiliary materials and ultra-low copper scrap steel, requiring that the sulfur content of the molten steel after adding the molten steel is less than 10ppm; the Cu content of the molten steel after adding the scrap steel is less than 0.07%; the slag amount of the converter steel is ≤0.8kg / t or the steel is retained for smelting; after the smelting is completed, the alloy is selected to have a low titanium high purity ferrosilicon with a Ti content of 0.015%±0.005%; Preferably, the CAS top slag reforming process comprises: reforming the top slag using a high aluminum reforming agent Al40 at a dosage of 1.5 kg / t molten steel; Preferably, the RH refining process comprises: selecting a low-titanium high-purity ferrosilicon alloy with a Ti content of 0.012%±0.005%; selecting A.KTB gun powder spray desulfurization in the RH desulfurization process, and selecting a calcium aluminate desulfurization agent; the total oxygen content of the molten steel after refining is ≤0.0012%; Preferably, the casting process comprises: controlling the columnar crystal rate of the produced continuous casting billet to be between 55% and 65%; Preferably, the hot rolling process comprises: controlling the thickness of the hot rolled plate at the end point of hot rolling to be 1.8 mm; Preferably, the normalization fast heating process comprises: heating to 960±3°C at a heating rate of 20°C / s in a N2 protective atmosphere and keeping the temperature for 115s to 125s; Preferably, the cold rolling process comprises: cold rolling to 0.2 mm using a twenty-roll rolling mill; Preferably, the short-time annealing process comprises: keeping the temperature at 990±3° C. for 115s to 125s in a protective atmosphere of N2:H2 of 2:

1.

4. The method according to claim 1, characterized in that: Preparation of high-copper and high-strength non-oriented silicon steel using molten iron with Cu≥0.04%: On the basis of narrow composition control of main alloy elements, high-copper and high-strength non-oriented silicon steel is prepared by increasing the Cu content.

5. The method according to claim 4, characterized in that Preparation of high-copper and high-strength non-oriented silicon steel using molten iron with Cu≥0.04%: high-copper molten steel → converter smelting → CAS top slag reforming → RH refining → casting → hot rolling → normalizing → cold rolling → complete recrystallization annealing → aging treatment; Preferably, the converter smelting process comprises: adding pure Cu blocks when tapping the converter to increase the Cu content in the molten steel; Preferably, the normalization process comprises: in a N2 atmosphere, heating to 960±3°C at a heating rate of 20°C / s and keeping the temperature for 115s to 125s; Preferably, the cold rolling process comprises: cold rolling to 0.3 mm using a twenty-roll rolling mill; Preferably, the complete recrystallization annealing process comprises: keeping the temperature at 990±3°C for 115s to 125s in a protective atmosphere of N2:H2 of 2:1; Preferably, the aging treatment process includes: a temperature of 550° C. and a holding time of 20 min.

6. A low-copper thin-gauge non-oriented silicon steel prepared by the method of claim 1, 2 or 3, characterized in that: The low-copper thin-gauge non-oriented silicon steel comprises the following chemical components by mass percentage: 3.2-3.3wt.% Si, 0.9-1.0wt.% Al, 0.3-0.4wt.% Mn, 0.0010-0.0015wt.% S, 0.0010-0.0018wt.% Ti, 0.01-0.05wt.% Cu, 0.06wt.% Sn, and the rest is Fe and unavoidable impurities; Preferably, the Cu content in the low-copper thin gauge non-oriented silicon steel is ≤0.015%; Preferably, the S content in the low-copper thin gauge non-oriented silicon steel is ≤0.0013%; Preferably, the Ti content in the low-copper thin-gauge non-oriented silicon steel is ≤0.0014%.

7. The low copper thin gauge non-oriented silicon steel according to claim 6, characterized in that: Magnetic induction intensity B of 0.2mm low copper thin gauge non-oriented silicon steel 50 is 1.666T, iron loss P 1.5 / 50 and P 10 / 400 They are 1.95W / kg and 10.88W / kg respectively.

8. A high-copper and high-strength non-oriented silicon steel prepared by the method according to claim 1, 4 or 5, characterized in that: The high-copper high-strength non-oriented silicon steel comprises the following chemical components by mass percentage: 3.4-3.6wt.% Si, 0.7-0.8wt.% Al, 0.4-0.6wt.% Mn, 0.0010-0.0015wt.% S, 0.0010-0.0018wt.% Ti, 0.75-1.5wt.% Cu, 0.06wt.% Sn, and the rest is Fe and unavoidable impurities; Preferably, the Cu content in the high-copper and high-strength non-oriented silicon steel is 1.0-1.5%.

9. The high-copper and high-strength non-oriented silicon steel according to claim 8, characterized in that: 0.3mm high copper high strength non-oriented silicon steel magnetic induction intensity B 50 is 1.648T, iron loss P 1.5 / 50 and P 10 / 400 They are 2.28W / kg and 15.67W / kg respectively, and the tensile strength R m Reaching 735.7MPa.

10. Use of the low-copper, thin-gauge non-oriented silicon steel according to any one of claims 6-7 in preparing a stator for a new energy vehicle drive motor, or use of the high-copper, high-strength non-oriented silicon steel according to any one of claims 8-9 in preparing a rotor for a new energy vehicle drive motor.

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