High-performance non-oriented silicon steel and preparation method therefor

Abstract

The present invention provides a high-performance non-oriented silicon steel, comprising the following components in percentage by mass: C: 0-0.003%, Si: 1.0-4.5%, Al: 0.022-1.0%, Mn: 0.12-0.93%, N: 0-0.003%, S: 0-0.003%, P: 0-0.005%, and the balance being Fe and inevitable impurities. The present invention further provides a preparation method for the high-performance non-oriented silicon steel, and an annealing process of flash heating and instantaneous heat preservation is used. The high-performance non-oriented silicon steel is a non-oriented silicon steel having low iron loss and high permeability, has iron loss Pt of about 2.81 W / Kg and magnetic induction intensity B of about 1.71 T at a low frequency, and has iron loss Pt of about 21.82 W / Kg and magnetic induction intensity B of about 1.72 T at a high frequency.

Description

A high performance non-oriented silicon steel and its preparation method Technical Field

[0001] The present invention belongs to the technical field of metal materials, and in particular relates to high-performance non-oriented silicon steel and a preparation method thereof. Background Art

[0002] Electricity is an indispensable energy source in modern society, the most common and important. The production, transmission, and use of electrical energy are inseparable from generators, transmission transformers, motors, and various electrical equipment and components such as ballasts, amplifiers, voltage regulators, relays, and rectifiers. Electromagnetic principles enable the conversion of mechanical energy into electrical energy, voltage into current, and the driving of electromechanical devices. A key component of these devices is the electromagnet core, the raw material of which is electrical steel, a cornerstone of the power and electrical industry.

[0003] Silicon steel is the most widely used soft magnetic material in industry, and industrial non-oriented silicon steel is the most widely used electrical steel, widely used in various motors. The performance of non-oriented silicon steel sheets not only directly affects power loss but also determines the performance, size, weight, and cost of products such as motors and transformers. Therefore, reducing iron loss and magnetic anisotropy and improving magnetic induction have become key research areas for silicon steel.

[0004] Summary of the Invention

[0005] The object of the present invention is to provide a non-oriented silicon steel with low iron loss and high magnetic permeability.

[0006] To this end, the present invention provides a high-performance non-oriented silicon steel, which comprises the following components, in percentage by mass: C: 0-0.003%, Si: 1.0-4.5%, Al: 0.022-1.0%, Mn: 0.12-0.93%, N: 0-0.003%, S: 0-0.003%, P: 0-0.005%, and the remainder is Fe and unavoidable impurities.

[0007] The present invention also provides a method for preparing the above-mentioned high-performance non-oriented silicon steel, comprising the following steps: smelting molten steel according to a set composition, casting the molten steel into ingots, hot rolling, normalizing pickling, cold rolling and annealing the ingots to obtain high-performance non-oriented silicon steel.

[0008] Specifically, the annealing comprises the following steps: (1) heating to an annealing temperature at a rate of 200-600° C. / s in an inert atmosphere; and (2) maintaining the temperature at the annealing temperature and then cooling.

[0009] Specifically, the annealing temperature is 700-1100°C.

[0010] Specifically, the inert atmosphere is a 30-95% nitrogen atmosphere.

[0011] Specifically, in the above step (2), the temperature is kept in a 30-95% nitrogen atmosphere.

[0012] Specifically, the holding time in the above step (2) is 0-10s.

[0013] Specifically, in the above step (2), cooling is performed at a cooling rate of 30°C / s.

[0014] Specifically, the temperature of the molten steel in the casting tundish is 1500°C-1580°C; the starting temperature of the hot rolling is 920°C-980°C, the finishing temperature of the hot rolling is 800°C-860°C; and the normalizing soaking temperature of the normalizing pickling is 900°C-1100°C.

[0015] Specifically, the thickness of the steel strip after cold rolling is 0.15-0.65 mm.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0017] The high-performance non-oriented silicon steel provided by the present invention is a non-oriented silicon steel with low iron loss and high magnetic permeability, which greatly improves the magnetic properties of non-oriented silicon steel with medium silicon content. At low frequency, the core loss Pt is about 2.81W / Kg, and the magnetic induction intensity B is about 1.71T. At high frequency, the core loss Pt is about 21.82W / Kg, and the magnetic induction intensity B is about 1.72T.

[0018] The preparation method of high-performance non-oriented silicon steel provided by the present invention adopts an annealing process of flash heating and instantaneous insulation. Compared with non-oriented silicon steel at a low heating rate and a long insulation time, the produced non-oriented silicon has lower iron loss and higher magnetic induction, which better meets the application requirements of new energy vehicle motors. At the same time, the significant shortening of the insulation time also speeds up the process flow and improves production efficiency.

[0019] The present invention will be described in further detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a comparison of magnetic properties in the RD direction under different insulation processes: (left) iron loss, (right) magnetic induction.

[0021] Figure 2 is a comparison of magnetic properties in the TD direction under different insulation processes: (left) iron loss, (right) magnetic induction.

[0022] Figure 3 shows the metallographic microstructures of silicon steel prepared under different heat preservation processes: (a) route 1; (b) route 2; (c) route 3; (d) route 4; (e) route 5.

[0023] Figure 4 shows the IPF-Z diagram and typical texture distribution diagram: (a, b) route 1; (c, d) route 2; (e, f) route 3; (g, h) route 4; (i, j) route 5.

[0024] Figure 5 ODF diagram: (a) route 1; (b) route 2; (c) route 3; (d) route 4; (e) route 5. DETAILED DESCRIPTION

[0025] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Although the representative embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that various modifications and changes can be made to the present invention without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the embodiments, but should be defined by the appended claims and their equivalents.

[0026] The present invention provides a high-performance non-oriented silicon steel. The high-performance non-oriented silicon steel comprises the following components, measured in percentage by mass: C: 0-0.003%, Si: 1.0-4.5%, Al: 0.022-1.0%, Mn: 0.12-0.93%, N: 0-0.003%, S: 0-0.003%, P: 0-0.005%, and the remainder is Fe and unavoidable impurities. The microstructure is mainly ferrite.

[0027] Si is an essential element in electrical steel. Adding Si to electrical steel can increase its resistivity and significantly reduce eddy current losses. It also helps reduce magnetostriction, thereby reducing the noise level during core operation. However, increasing Si content significantly decreases the saturation magnetic induction intensity and the plasticity of the steel sheet, making cold working more difficult and significantly increasing the risk of strip breakage and edge cracking. Therefore, the Si content in electrical steel generally does not exceed 3.5%. In the present invention, the Si content is controlled within a range of 1.0% to 4.5%.

[0028] Al has similar effects to Si in increasing resistivity and stabilizing ferrite in steel. Therefore, it is also a common element in non-oriented electrical steel. Al's increased resistivity significantly reduces induced eddy currents, making it a primary means of reducing eddy current losses in electrical steel. However, its drawback, similar to Si's, is that it reduces the density and saturation magnetic induction intensity of electrical steel, affecting the magnetic induction value of the steel sheet. In the present invention, the Al content is controlled within a range of 0.022-0.32%.

[0029] Mn is an important element for increasing resistivity and reducing eddy current loss. It also promotes the formation of favorable surface textures, reduces the occupancy of (111) surface textures, and improves magnetic properties. Mn is also an indispensable element for preventing hot brittleness. It can form MnS particles with S to prevent hot brittleness caused by FeS. However, the effect of Mn is also closely related to the S content. Excessive S content will promote the increase of MnS precipitation, thereby increasing iron loss. In the present invention, the Mn content is controlled to be 0.12-0.93%.

[0030] Both carbon and nitrogen are harmful elements in electrical steel, easily causing carbide and nitride precipitation, which impairs the magnetic properties of the steel. Excessive carbon content can easily cause cracking in hot-rolled steel. Nitride particles formed by nitrogen can pin grain boundaries and migrate, forming surface fine-grained areas and increasing iron loss. Therefore, the carbon and nitrogen content in electrical steel must be strictly controlled. In the present invention, the carbon and nitrogen content is controlled to be below 0.003%.

[0031] S and P are the most common non-metallic impurity elements in electrical steel. S is considered an unavoidable impurity element that generates sulfide particles, hinders the movement of magnetic domains, and is harmful to the magnetic properties of steel, so it should be removed as much as possible. The P element has a significant solid solution strengthening effect, which can increase the hardness of the steel plate and help improve the punching performance of the steel plate. The solid-solution P element also increases the resistivity and reduces eddy current loss. However, the P element also has a significant tendency to segregate at dislocations and grain boundaries, which will hinder grain growth, increase hysteresis loss, and affect the evolution of texture, thereby affecting the magnetic induction of electrical steel. Therefore, the S element content in electrical steel should be strictly limited. The P element content is affected by the specific production products and conditions and generally does not exceed 0.1%. In the present invention, the S element content is controlled to be below 0.003%, and the P element content is controlled to be below 0.005%.

[0032] The present invention also provides a method for preparing the above-mentioned high-performance non-oriented silicon steel, comprising the following steps:

[0033] S1. Smelt molten steel according to the set composition and cast the molten steel into ingots; the temperature of the molten steel in the casting tundish is 1500℃-1580℃.

[0034] S2. Hot rolling the ingot and coiling it after hot rolling; the starting temperature of the hot rolling is 920° C.-980° C., and the finishing temperature of the hot rolling is 800° C.-860° C.

[0035] S3. Normalize and pickle the hot coil, and perform normalization and soaking at a temperature of 900° C. to 1100° C., and then cold roll the hot coil to obtain a cold-rolled strip having a thickness of 0.15 to 0.65 mm.

[0036] The methods for smelting molten steel include electric furnace and converter smelting methods, the methods for forming molten steel into billets include continuous casting and rolling, ESP, CSP and thin strip continuous casting methods, and cold rolling includes continuous rolling and single-stand reversible rolling.

[0037] S4, cold rolled strip adopts flash heating and instantaneous heat preservation annealing process

[0038] (1) In an inert atmosphere, preferably a 0-100% nitrogen + 100-0% hydrogen atmosphere, the temperature is raised from 30°C to the annealing temperature T between 700°C and 1100°C at a rate of 200-600°C / s;

[0039] (2) In an inert atmosphere, preferably 0-100% nitrogen + 100-0% hydrogen atmosphere, keep the annealing temperature T for 0-10s;

[0040] (3) Under an inert atmosphere, preferably 0-100% nitrogen + 100-0% hydrogen atmosphere, cooling from the annealing temperature T to 30° C. at a rate of 30° C. / s to obtain high-performance non-oriented silicon steel.

[0041] The effects of the high performance non-oriented silicon steel and the preparation method of the present invention are studied below through specific examples.

[0042] Example 1:

[0043] This embodiment provides a high-performance non-oriented silicon steel, which includes the following components, in percentage by mass: C: 0.003%; Si: 2.9%; Al: 0.75%; Mn: 0.15%; N: 0.0025%; S: 0.0015%; P: 0.002%, and the remainder is Fe and unavoidable impurities.

[0044] The high performance non-oriented silicon steel is prepared by the following steps.

[0045] S1. Molten steel is smelted according to the set composition and cast into ingots; the temperature of the molten steel in the casting tundish is 1520℃.

[0046] S2. Hot rolling the ingot and coiling it; the hot rolling start temperature is 950° C., and the hot rolling finish temperature is 840° C.

[0047] S3. The hot coil is normalized and pickled and then cold rolled to obtain a 0.35 mm thick cold rolled strip.

[0048] S4, cold rolled strip annealing process

[0049] (1) In a 75% nitrogen + 25% hydrogen atmosphere, the air content in the annealing furnace is strictly controlled and the temperature is increased from 30°C to 980°C at a rate of 400°C / s;

[0050] (2) In a 75% nitrogen + 25% hydrogen atmosphere, strictly control the air content in the annealing furnace and keep the annealing temperature T for 0s;

[0051] (3) In an atmosphere of 75% nitrogen + 25% hydrogen, the air content in the annealing furnace is strictly controlled, and the steel is cooled from 980°C to 30°C at a rate of 30°C / s to obtain high-performance non-oriented silicon steel, which is marked as route 3.

[0052] Example 2:

[0053] This embodiment provides a high-performance non-oriented silicon steel, which includes the following components, in percentage by mass: C: 0.003%; Si: 2.9%; Al: 0.75%; Mn: 0.15%; N: 0.0025%; S: 0.0015%; P: 0.002%, and the remainder is Fe and unavoidable impurities.

[0054] The high performance non-oriented silicon steel is prepared by the following steps.

[0055] S1. Molten steel is smelted according to the set composition and cast into ingots; the temperature of the molten steel in the casting tundish is 1520℃.

[0056] S2. Hot rolling the ingot and coiling it; the hot rolling start temperature is 950° C., and the hot rolling finish temperature is 840° C.

[0057] S3. The hot coil is normalized and pickled and then cold rolled to obtain a 0.35 mm thick cold rolled strip.

[0058] S4. The cold rolled strip is subjected to annealing process.

[0059] (1) In a 75% nitrogen + 25% hydrogen atmosphere, the air content in the annealing furnace is strictly controlled and the temperature is increased from 30°C to 1050°C at a rate of 400°C / s;

[0060] (2) In a 75% nitrogen + 25% hydrogen atmosphere, strictly control the air content in the annealing furnace and keep the annealing temperature T for 0s;

[0061] (3) In an atmosphere of 75% nitrogen + 25% hydrogen, the air content in the annealing furnace is strictly controlled, and the steel is cooled from 1050°C to 30°C at a rate of 30°C / s to obtain high-performance non-oriented silicon steel, which is marked as route 4.

[0062] Example 3:

[0063] This embodiment provides a high-performance non-oriented silicon steel, which includes the following components, in percentage by mass: C: 0.003%; Si: 2.9%; Al: 0.75%; Mn: 0.15%; N: 0.0025%; S: 0.0015%; P: 0.002%, and the remainder is Fe and unavoidable impurities.

[0064] The high performance non-oriented silicon steel is prepared by the following steps.

[0065] S1. Molten steel is smelted according to the set composition and cast into ingots; the temperature of the molten steel in the casting tundish is 1520℃.

[0066] S2. Hot rolling the ingot and coiling it; the hot rolling start temperature is 950° C., and the hot rolling finish temperature is 840° C.

[0067] S3. The hot coil is normalized and pickled and then cold rolled to obtain a 0.35 mm thick cold rolled strip.

[0068] S4. The cold rolled strip is subjected to annealing process.

[0069] (1) In a 75% nitrogen + 25% hydrogen atmosphere, the air content in the annealing furnace is strictly controlled and the temperature is increased from 30°C to 1050°C at a rate of 400°C / s;

[0070] (2) In a 75% nitrogen + 25% hydrogen atmosphere, strictly control the air content in the annealing furnace and keep it at the annealing temperature T for 10s;

[0071] (3) In an atmosphere of 75% nitrogen + 25% hydrogen, the air content in the annealing furnace is strictly controlled, and the steel is cooled from 980°C to 30°C at a rate of 30°C / s to obtain high-performance non-oriented silicon steel, which is marked as route 5.

[0072] Comparative Example 1:

[0073] This comparative example provides a non-oriented silicon steel. The high-performance non-oriented silicon steel comprises the following components, in percentage by mass: C: 0.003%; Si: 2.9%; Al: 0.75%; Mn: 0.15%; N: 0.0025%; S: 0.0015%; P: 0.002%, and the remainder is Fe and unavoidable impurities.

[0074] The non-oriented silicon steel is prepared by the following steps.

[0075] S1. Molten steel is smelted according to the set composition and cast into ingots; the temperature of the molten steel in the casting tundish is 1520℃.

[0076] S2. Hot rolling the ingot and coiling it; the hot rolling start temperature is 950° C., and the hot rolling finish temperature is 840° C.

[0077] S3. The hot coil is normalized and pickled and then cold rolled to obtain a 0.35 mm thick cold rolled strip.

[0078] S4. The cold rolled strip is subjected to annealing process.

[0079] (1) In a 75% nitrogen + 25% hydrogen atmosphere, the air content in the annealing furnace is strictly controlled and the temperature is increased from 30°C to 980°C at a rate of 100°C / s;

[0080] (2) In a 75% nitrogen + 25% hydrogen atmosphere, strictly control the air content in the annealing furnace and keep the annealing temperature T for 0s;

[0081] (3) In an atmosphere of 75% nitrogen + 25% hydrogen, the air content in the annealing furnace is strictly controlled, and the steel is cooled from 980°C to 30°C at a rate of 30°C / s to obtain non-oriented silicon steel, which is marked as route 1.

[0082] Comparative Example 2:

[0083] This comparative example provides a non-oriented silicon steel. The high-performance non-oriented silicon steel comprises the following components, in percentage by mass: C: 0.003%; Si: 2.9%; Al: 0.75%; Mn: 0.15%; N: 0.0025%; S: 0.0015%; P: 0.002%, and the remainder is Fe and unavoidable impurities.

[0084] The non-oriented silicon steel is prepared by the following steps.

[0085] S1. Molten steel is smelted according to the set composition and cast into ingots; the temperature of the molten steel in the casting tundish is 1520℃.

[0086] S2. Hot rolling the ingot and coiling it; the hot rolling start temperature is 950° C., and the hot rolling finish temperature is 840° C.

[0087] S3. The hot coil is normalized and pickled and then cold rolled to obtain a 0.35 mm thick cold rolled strip.

[0088] S4, cold rolled strip annealing process

[0089] (1) In a 75% nitrogen + 25% hydrogen atmosphere, the air content in the annealing furnace is strictly controlled and the temperature is increased from 30°C to 980°C at a rate of 400°C / s;

[0090] (2) In a 75% nitrogen + 25% hydrogen atmosphere, strictly control the air content in the annealing furnace and keep it at the annealing temperature T for 15 seconds;

[0091] (3) In an atmosphere of 75% nitrogen + 25% hydrogen, the air content in the annealing furnace is strictly controlled, and the steel is cooled from 980°C to 30°C at a rate of 30°C / s to obtain non-oriented silicon steel, which is marked as route 2.

[0092] Example 4:

[0093] In this example, the magnetic properties of the non-oriented silicon steels prepared in Examples 1-3 and Comparative Examples 1-2 in the RD and TD directions were studied, and the results are shown in Figures 1-2.

[0094] Route 1 low frequency P 15 / 50 About 3.41W / Kg, B 50 About 1.70T, P at high frequency 10 / 400 About 24.12W / Kg, B 50 About 1.71T.

[0095] Route 2 low frequency P 15 / 50 About 3.27W / Kg, B 50 About 1.69T, P at high frequency 10 / 400 About 23.30W / Kg, B 50 About 1.70T.

[0096] Route 3 low frequency P 15 / 50 About 2.81W / Kg, B 50 About 1.71T, P at high frequency 10 / 400 About 21.82W / Kg, B 50 About 1.72T.

[0097] Route 4 low frequency P 15 / 50 About 2.69W / Kg, B 50 About 1.70T, P at high frequency 10 / 400 About 21.54W / Kg, B 50 About 1.71T.

[0098] Route 5 low frequency P 15 / 50 About 2.76W / Kg, B 50 About 1.70T, P at high frequency 10 / 400 About 21.50W / Kg, B 50 About 1.70T.

[0099] As can be seen from the above, the core loss of Route 3 under the instantaneous holding process is lower, which is not much different from Route 4 and Route 5. However, Route 3 has a lower holding temperature and is easier to implement. At the same time, the magnetic induction intensity does not decrease compared with the other groups, and even increases. Therefore, Route 3 has the best magnetic properties.

[0100] The above examples are merely illustrative of the present invention and do not limit the scope of protection of the present invention. Any design that is identical or similar to the present invention falls within the scope of protection of the present invention.

Claims

1. A high performance non-oriented silicon steel, characterized in that: The high performance non-oriented silicon steel comprises the following components in percentage by mass: C: 0-0.003%, Si: 1.0-4.5%, Al: 0.022-1.0%, Mn: 0.12-0.93%, N: 0-0.003%, S: 0-0.003%, P: 0-0.005%, and the rest is Fe and unavoidable impurities.

2. The method for preparing high-performance non-oriented silicon steel according to claim 1, wherein: The following steps are involved: Molten steel is smelted according to the set composition, cast into ingots, and the ingots are hot rolled, normalized and pickled, cold rolled and annealed to obtain high-performance non-oriented silicon steel.

3. The method for preparing high-performance non-oriented silicon steel according to claim 2, wherein: The annealing comprises the following steps: (1) Raise the temperature to the annealing temperature at 200-600°C / s under an inert atmosphere; (2) Keep at the annealing temperature and then cool.

4. The method for preparing high-performance non-oriented silicon steel according to claim 3, wherein: The annealing temperature is 700-1100°C.

5. The method for preparing high-performance non-oriented silicon steel according to claim 3, wherein: The inert atmosphere is a 30-95% nitrogen atmosphere.

6. The method for preparing high-performance non-oriented silicon steel according to claim 3, wherein: In the step (2), the temperature is maintained in a 30-95% nitrogen atmosphere.

7. The method for preparing high-performance non-oriented silicon steel according to claim 3, wherein: The holding time in step (2) is 0-10s.

8. The method for preparing high-performance non-oriented silicon steel according to claim 3, wherein: In the step (2), cooling is performed at a cooling rate of 25°C / s to 40°C / s.

9. The method for preparing high-performance non-oriented silicon steel according to claim 2, wherein: The temperature of the molten steel in the casting tundish is 1500°C-1580°C; the starting temperature of the hot rolling is 920°C-980°C, the finishing temperature of the hot rolling is 800°C-860°C; and the normalized soaking temperature of the normalized pickling is 900°C-1100°C.

10. The method for preparing high-performance non-oriented silicon steel according to claim 2, wherein: The thickness of the steel strip after cold rolling is 0.15-0.65mm.

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