Non-oriented silicon steel and preparation method thereof

Abstract

The present invention relates to the field of silicon steel, and discloses a non-oriented silicon steel and a preparation method thereof, wherein the non-oriented silicon steel comprises the following chemical components in weight percentage: C: 0.001-0.005%, Si: 2.4-3%, Mn: 0.25-0.5%, Al: 0.7-1.1%, P≤0.02%, S≤0.005%, Sn: 0.005-0.025%; wherein Mn / (Si+Al)≥8%, Si+Mn+Al: 3.3-4.6%; the rest is Fe and inevitable impurities. The method adds an appropriate amount of Sn, and then performs smelting, continuous casting, hot rolling, normalizing, cold rolling, and annealing, so as to finally obtain high-strength non-oriented silicon steel with excellent magnetic properties, and the non-oriented silicon steel has lower iron loss and higher strength.

Description

Technical Field

[0001] The invention relates to the field of silicon steel, and in particular to non-oriented silicon steel and a preparation method thereof. Background Art

[0002] With the increasing requirements for environmental protection, new energy vehicles, as an environmentally friendly means of transportation, are developing more and more rapidly; the drive motor is one of the core components of new energy vehicles and needs to meet the requirements of miniaturization, high efficiency and high torque. The miniaturization and high efficiency of the motor require that the non-oriented silicon steel used to make its iron core should have low iron loss and high magnetic induction; thinning the thickness of silicon steel can effectively reduce iron loss, and thin-gauge silicon steel is the development trend; with the increase in speed, the huge centrifugal force can easily damage the motor rotor, so non-oriented silicon steel is required to have higher strength to ensure safety at high speeds. Traditional non-oriented silicon steel can meet the requirements of low iron loss and high magnetic induction, but the strength is low. Strength and iron loss are contradictory indicators, and the increase in strength will reduce the magnetic properties. At the same time, the increase in strength will reduce the processing performance of silicon steel, and the difficulty of thinning is high. Therefore, it is an important research task to develop non-oriented silicon steel with thin specifications, low iron loss and high strength.

[0003] The main methods to improve the strength of non-oriented silicon steel include precipitation strengthening, solid solution strengthening, dislocation strengthening and composite strengthening. Precipitation strengthening mainly improves the strength by forming fine carbide particles through micro-alloy elements and C. These fine carbide particles will hinder the rotation of magnetic domains and reduce magnetic properties. Solid solution strengthening improves the strength through elements such as Si, Mn, Al, and Cu, but too high Si can easily lead to difficulties in cold rolling. The addition of Cu will cause "copper brittleness", which increases the difficulty of rolling. High-temperature annealing is required to temporarily dissolve Cu and delay recrystallization. Higher heating temperatures will cause abnormal grain growth, which is not conducive to improving strength.

[0004] At present, the pace of research and development of high-strength non-oriented silicon steel is also being accelerated. For example, patent application CN106282781A discloses a method for preparing high-strength non-oriented silicon steel based on nano-Cu precipitation strengthening. The nano-Cu precipitation has little hindering effect on the movement of magnetic domain walls, and has almost no effect on the magnetic induction while greatly improving the strength. However, the method of strengthening by Cu precipitation requires high-temperature annealing to temporarily dissolve Cu, delay recrystallization, and control the recrystallization rate. However, high-temperature annealing causes some grains to grow abnormally, with a yield strength of 640-750MPa and a magnetic induction of B. 50 1.67-1.74T, iron loss P 1.0 / 400 It is 22.5-31.5W / kg, and the iron loss is relatively high.

[0005] Patent application CN106435358A adopts twin-roll thin strip continuous casting technology, adds precipitation strengthening element Nb, and combines composition design, rolling and heat treatment to produce non-oriented silicon steel with excellent magnetic properties and high strength, with yield strength of 600-780MPa and magnetic induction B 50 1.68-1.73T, iron loss P 1.0 / 400 It is 25.5-37.5W / kg, and the iron loss is relatively high.

[0006] Patent application CN108286014A improves the strength through the solid solution strengthening ability of Si, but the higher Si content reduces the toughness of the steel plate, which is not conducive to product processing; Patent application CN111235461A adopts a high C (0.03-0.08%) component system to improve the strength of non-oriented silicon steel by adding Nb, Ti and trace rare earth, but C and Ti will reduce the magnetic properties of non-oriented silicon steel. Yield strength 540-1060MPa, magnetic induction B 50 1.58-1.68T, iron loss P 1.0 / 400 8-60W / kg.

[0007] Patent application CN112030076A adopts a high Si (2.8-3.5%) composition system, and improves the strength of non-oriented silicon steel by adding Cr, Sn, and Ce for solid solution strengthening, but Cr significantly increases hysteresis loss and iron loss is high. Although the high Si composition system can greatly improve the strength, when the Si content exceeds 3.0%, rolling is difficult and the steel coil is easily broken. Summary of the invention

[0008] The purpose of the present invention is to overcome the above-mentioned problems existing in the prior art and to provide a non-oriented silicon steel and a preparation method thereof. The method comprises adding an appropriate amount of Sn, followed by smelting, continuous casting, hot rolling, normalizing, cold rolling and annealing, and finally obtaining high-strength non-oriented silicon steel with excellent magnetic properties, and making the non-oriented silicon steel have lower iron loss and higher strength.

[0009] In order to achieve the above-mentioned object, the present invention provides a non-oriented silicon steel on the one hand, which comprises the following chemical components in weight percentage: C: 0.001-0.005%, Si: 2.4-3%, Mn: 0.25-0.5%, Al: 0.7-1.1%, P≤0.02%, S≤0.005%, Sn: 0.005-0.025%; wherein, Mn / (Si+Al)≥8%, Si+Mn+Al: 3.3-4.6%; the rest is Fe and unavoidable impurities.

[0010] In the present invention, the functions and content control reasons of the chemical components of non-oriented silicon steel are as follows:

[0011] C: C is beneficial to improving the strength of the steel plate, but too high a C content will reduce the toughness of the steel plate, and C will damage the magnetic properties of the steel plate whether it exists in the form of solid solution or cementite. The present invention limits the C content to the above range.

[0012] Si: As the Si content increases, the strength of the steel plate increases, the magnetic induction decreases, and the brittleness of the steel plate increases, which is not conducive to the surface quality control of the hot-rolled coil. Therefore, the Si content in the steel should be reduced in the present invention. It is more appropriate to control the Si content in the present invention within the above range.

[0013] Mn: Mn is beneficial to improve the resistivity of silicon steel and reduce iron loss. It can also improve strength through solid solution strengthening. Therefore, the present invention increases the Mn content to be set within the above range, and at the same time, in order to ensure the role of Mn in steel, further control Mn / (Si+Al)≥8%, and the content of Si+Mn+Al is 3.3-4.6%.

[0014] Al: As the Al content increases, the strength of the steel plate increases and the magnetic induction increases. However, too high an Al content can easily cause the molten steel to become sticky. Therefore, the present invention controls the Al content to be within the above range.

[0015] P: P is promoted by Sn to produce segregation, refine grains, increase strength, and improve texture, but Fe3P segregation will make the steel plate brittle and reduce toughness, so the present invention controls the P content within the above range.

[0016] S: S and Mn in steel can form plastic MnS inclusions to reduce hot brittleness, but it will cause the strip steel to form a banded structure, reduce the toughness and formability of the steel plate, and S has a great influence on the magnetic properties. It is more appropriate to control the S content within the above range in the present invention.

[0017] Sn: Sn will segregate at the original grain boundary during hot rolling and promote the segregation of P, hindering grain growth, refining the grains, and improving the strength of the steel plate. However, grain refinement will lead to increased hysteresis loss. Since Sn and P segregation will improve the texture and reduce the influence of segregation on magnetic induction, the present invention controls the Sn content to the above range.

[0018] Preferably, the thickness of the non-oriented silicon steel of the present invention is 0.15 mm, and its magnetic induction intensity B 50 1.60-1.69T, high frequency iron loss W 1.0 / 400 11.5-18.5W / Kg, yield strength R el 560-645MPa, tensile strength R m It is 610-700MPa.

[0019] In the present invention, the magnetic induction intensity B 50 And high frequency iron loss W 1.0 / 400All tests were carried out according to the method of GB / T 3655-2008, and the yield strength R el And tensile strength R m All tests were carried out in accordance with the method of GB / T 3075-2008.

[0020] A second aspect of the present invention provides a method for preparing the non-oriented silicon steel according to claim 1 or 2, the method comprising the following steps:

[0021] (1) hot rolling the ingot to obtain a steel plate, normalizing, pickling and cold rolling the steel plate in sequence to obtain a steel coil, and annealing the steel coil to obtain an annealed steel coil;

[0022] (2) coating a semi-organic coating on the surface of the annealed steel coil to obtain non-oriented silicon steel.

[0023] Preferably, in step (1), molten iron is smelted and continuously cast to obtain a cast billet having a thickness of 200-240 mm; the chemical composition content of the cast billet is consistent with the chemical composition content of the final finished product of non-oriented silicon steel.

[0024] Preferably, in step (1), the hot rolling conditions include: a starting rolling temperature of 1100-1200°C, a finishing rolling temperature of 850-890°C, and a coiling temperature of 660-720°C.

[0025] In the preferred case of step (1), the thickness of the steel plate is 1.8-2.2 mm.

[0026] In a preferred embodiment of the present invention, in step (1), the normalization conditions include: a temperature of 900-1000° C. and a time of 1-3 min.

[0027] In step (1) of the present invention, the steel plate is normalized, cooled, and then pickled.

[0028] Further preferably, in step (1), the cold rolling is performed using a 20-roll rolling mill to a thickness of 0.15 mm (the effects of subsequent annealing and coating of a semi-organic coating on the thickness are negligible), and the cold rolling passes are 4-6 passes, with a reduction rate of ≥35% for each of the first 3-4 passes, and a reduction rate of ≥30% for each of the last 1-2 passes.

[0029] The invention adopts a large reduction rate during cold rolling, which is beneficial to increasing the dislocation density and improving the strength of silicon steel through dislocation strengthening; at the same time, rolling with a large reduction rate leads to increased deformation energy storage, high dislocation density, increased recrystallization nucleation points, recrystallization during annealing, and formation of a recrystallized structure with relatively uniform size.

[0030] In step (1), the steel coil is annealed under the protection of a mixed gas of hydrogen and nitrogen; preferably, the content of hydrogen in the mixed gas is ≥ 20 volume %.

[0031] Furthermore, in step (1), the annealing conditions include: a temperature of 700-800°C and a time of 20-60s; wherein the annealing temperature is controlled at 700-800°C for the purpose of incomplete recrystallization and improving dislocation strength.

[0032] In step (2) of the present invention, the purpose of coating the semi-organic coating on the upper surface and the lower surface of the annealed steel coil is to ensure insulation and interlayer resistance. The semi-organic coating is a semi-organic coating commonly used in the art, and the coating operation is also a conventional operation process in the art.

[0033] Compared with the prior art, the present invention uses the characteristics of adding Sn and using Sn element microalloying to refine grains, as well as reasonable composition ratio and process, to improve the strength and magnetic properties of non-oriented silicon steel through microalloying, without the need to add solid solution metal elements such as Cr, Cu, and Ti, and the Si content is ≤3.0%, thereby avoiding the problem of rolling difficulties under high Si system. High reduction rate rolling increases dislocation density, increases steel plate strength and grain uniformity, reduces iron loss, promotes the formation of favorable textures, and does not require high temperature annealing, thereby solving the problem of abnormal grain growth and reduced grain size uniformity due to excessively high annealing temperature, so that the produced non-oriented silicon steel has high strength and excellent magnetic properties. DETAILED DESCRIPTION

[0034] The specific implementation of the present invention is described in detail below in conjunction with the examples. It should be understood that the specific implementation described herein is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0035] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0036] Example 1

[0037] (1) After smelting and continuous casting of molten iron, a cast billet is obtained, and the thickness of the cast billet is 240 mm. The cast billet is hot rolled, and the hot rolling conditions include: the starting rolling temperature is 1150° C., the final rolling temperature is 870° C., and the coiling temperature is 700° C. to obtain a steel plate, and the thickness of the steel plate is 2.0 mm. The steel plate is normalized, and the normalization conditions include: the temperature is 980° C., the time is 2 min, and then cooled, followed by pickling, and then cold rolled, and the cold rolling is rolled to 0.15 by a 20-roll rolling mill. mm thickness, and the cold rolling passes are 4-6 passes, the reduction rate of each of the first 3-4 passes is ≥35%, and the reduction rate of each of the last 1-2 passes is ≥30%, to obtain a steel coil, and the steel coil is placed in a high-temperature tubular annealing furnace, and annealed under the protection of a mixed gas of hydrogen and nitrogen. The annealing conditions include: a temperature of 750° C., a time of 30 seconds, a hydrogen content of 20% by volume, and a nitrogen content of 80% by volume in the mixed gas, to obtain an annealed steel coil;

[0038] (2) coating the upper surface and the lower surface of the annealed steel coil with a semi-organic coating to obtain non-oriented silicon steel;

[0039] The chemical composition content (weight percentage) of the ingot in step (1) of this embodiment is shown in Table 1 (the remainder not shown in Table 1 is Fe and inevitable impurities). The chemical composition content of the non-oriented silicon steel obtained in step (2) is the same as that of the ingot. The magnetic induction intensity B of the non-oriented silicon steel is 50 is 1.66T, high frequency iron loss W 1.0 / 400 =14.7W / Kg, yield strength R el The tensile strength R is 583MPa. m 645MPa; magnetic induction intensity B 50 And high frequency iron loss W 1.0 / 400 All tests were carried out according to the method of GB / T 3655-2008, and the yield strength R el And tensile strength R m All tests were carried out in accordance with the method of GB / T 3075-2008.

[0040] Table 1

[0041]

[0042] Example 2

[0043] (1) After smelting and continuous casting of molten iron, a cast billet is obtained, and the thickness of the cast billet is 240 mm. The cast billet is hot rolled, and the hot rolling conditions include: the starting rolling temperature is 1169° C., the final rolling temperature is 860° C., and the coiling temperature is 710° C. to obtain a steel plate, and the thickness of the steel plate is 2.0 mm. The steel plate is normalized, and the normalization conditions include: the temperature is 950° C., the time is 2 min, and then cooled, followed by pickling, and then cold rolled, and the cold rolling is rolled to 0.15 by a 20-roll rolling mill. mm thickness, and the cold rolling passes are 4-6 passes, the reduction rate of each of the first 3-4 passes is ≥35%, and the reduction rate of each of the last 1-2 passes is ≥30%, to obtain a steel coil, and the steel coil is placed in a high-temperature tubular annealing furnace, and annealed under the protection of a mixed gas of hydrogen and nitrogen. The annealing conditions include: a temperature of 800° C., a time of 30 seconds, a hydrogen content of 20% by volume, and a nitrogen content of 80% by volume in the mixed gas, to obtain an annealed steel coil;

[0044] (2) coating the upper surface and the lower surface of the annealed steel coil with a semi-organic coating to obtain non-oriented silicon steel;

[0045] The chemical composition content (weight percentage) of the ingot in step (1) of this embodiment is shown in Table 2 (the remainder not shown in Table 2 is Fe and inevitable impurities). The chemical composition content of the non-oriented silicon steel obtained in step (2) is the same as that of the ingot. The magnetic induction intensity B of the non-oriented silicon steel is 50 1.60T, high frequency iron loss W 1.0 / 400 =12.5W / Kg, yield strength R el The tensile strength is 560MPa and the m 610MPa; magnetic induction intensity B 50 And high frequency iron loss W 1.0 / 400 All tests were carried out according to the method of GB / T 3655-2008, and the yield strength R el And tensile strength R m All tests were carried out in accordance with the method of GB / T 3075-2008.

[0046] Table 2

[0047]

[0048] Example 3

[0049] (1) After smelting and continuous casting of molten iron, a cast billet is obtained, and the thickness of the cast billet is 240 mm. The cast billet is hot rolled, and the hot rolling conditions include: the starting rolling temperature is 1200° C., the final rolling temperature is 890° C., and the coiling temperature is 720° C. to obtain a steel plate, and the thickness of the steel plate is 2.0 mm. The steel plate is normalized, and the normalization conditions include: the temperature is 990° C., the time is 2 min, and then cooled, followed by pickling, and then cold rolled, and the cold rolling is rolled to 0.15 by a 20-roll rolling mill. mm thickness, and the cold rolling passes are 4-6 passes, the reduction rate of each of the first 3-4 passes is ≥35%, and the reduction rate of each of the last 1-2 passes is ≥30%, to obtain a steel coil, and the steel coil is placed in a high-temperature tubular annealing furnace, and the steel coil is annealed under the protection of a mixed gas of hydrogen and nitrogen. The annealing conditions include: a temperature of 700° C., a time of 30 seconds, a hydrogen content of 20% by volume, and a nitrogen content of 80% by volume in the mixed gas, to obtain an annealed steel coil;

[0050] (2) coating the upper surface and the lower surface of the annealed steel coil with a semi-organic coating to obtain non-oriented silicon steel;

[0051] The chemical composition content (weight percentage) of the ingot in step (1) of this embodiment is shown in Table 3 (the remainder not shown in Table 3 is Fe and unavoidable impurities). The chemical composition content of the non-oriented silicon steel obtained in step (2) is the same as that of the ingot. The magnetic induction intensity B of the non-oriented silicon steel is 50 1.65T, high frequency iron loss W 1.0 / 400 =18.5W / Kg, yield strength R el The tensile strength is 660MPa and the m 700MPa; magnetic induction intensity B 50 And high frequency iron loss W 1.0 / 400 All tests were carried out according to the method of GB / T 3655-2008, and the yield strength R el And tensile strength R m All tests were carried out in accordance with the method of GB / T 3075-2008.

[0052] Table 3

[0053]

[0054] Example 4

[0055] (1) After smelting and continuous casting of molten iron, a cast billet is obtained, and the thickness of the cast billet is 240 mm. The cast billet is hot rolled, and the hot rolling conditions include: the starting rolling temperature is 1180° C., the final rolling temperature is 865° C., and the coiling temperature is 690° C. to obtain a steel plate, and the thickness of the steel plate is 2.0 mm. The steel plate is normalized, and the normalization conditions include: the temperature is 940° C., the time is 2 min, and then cooled, followed by pickling, and then cold rolled, and the cold rolling is rolled to 0.15 by a 20-roll rolling mill. mm thickness, and the cold rolling passes are 4-6 passes, the reduction rate of each of the first 3-4 passes is ≥35%, and the reduction rate of each of the last 1-2 passes is ≥30%, to obtain a steel coil, and the steel coil is placed in a high-temperature tubular annealing furnace, and annealed under the protection of a mixed gas of hydrogen and nitrogen. The annealing conditions include: a temperature of 790° C., a time of 30 seconds, a hydrogen content of 20% by volume, and a nitrogen content of 80% by volume in the mixed gas, to obtain an annealed steel coil;

[0056] (2) coating the upper surface and the lower surface of the annealed steel coil with a semi-organic coating to obtain non-oriented silicon steel;

[0057] The chemical composition content (weight percentage) of the ingot in step (1) of this embodiment is shown in Table 4 (the remainder not shown in Table 4 is Fe and unavoidable impurities). The chemical composition content of the non-oriented silicon steel obtained in step (2) is the same as that of the ingot. The magnetic induction intensity B of the non-oriented silicon steel is 50 1.65T, high frequency iron loss W 1.0 / 400 =11.5W / Kg, yield strength R el The tensile strength is 615MPa, m 680MPa; magnetic induction intensity B 50 And high frequency iron loss W 1.0 / 400 All tests were carried out according to the method of GB / T 3655-2008, and the yield strength R el And tensile strength R m All tests were carried out in accordance with the method of GB / T 3075-2008.

[0058] Table 4

[0059]

[0060] Example 5

[0061] (1) After smelting and continuous casting of molten iron, a cast billet is obtained, and the thickness of the cast billet is 240 mm. The cast billet is hot rolled, and the hot rolling conditions include: the starting rolling temperature is 1100° C., the final rolling temperature is 850° C., and the coiling temperature is 660° C. to obtain a steel plate, and the thickness of the steel plate is 2.0 mm. The steel plate is normalized, and the normalization conditions include: the temperature is 920° C., the time is 2 min, and then cooled, followed by pickling, and then cold rolled, and the cold rolling is rolled to 0.15 by a 20-roll rolling mill. mm thickness, and the cold rolling passes are 4-6 passes, the reduction rate of each of the first 3-4 passes is ≥35%, and the reduction rate of each of the last 1-2 passes is ≥30%, to obtain a steel coil, and the steel coil is placed in a high-temperature tubular annealing furnace, and annealed under the protection of a mixed gas of hydrogen and nitrogen. The annealing conditions include: a temperature of 780° C., a time of 30 seconds, a hydrogen content of 20% by volume, and a nitrogen content of 80% by volume in the mixed gas, to obtain an annealed steel coil;

[0062] (2) coating the upper surface and the lower surface of the annealed steel coil with a semi-organic coating to obtain non-oriented silicon steel;

[0063] The chemical composition content (weight percentage) of the ingot in step (1) of this embodiment is shown in Table 5 (the remainder not shown in Table 5 is Fe and unavoidable impurities). The chemical composition content of the non-oriented silicon steel obtained in step (2) is the same as that of the ingot. The magnetic induction intensity B of the non-oriented silicon steel is 50 is 1.69T, high frequency iron loss W 1.0 / 400 =16.9W / Kg, yield strength R el The tensile strength is 590MPa and the m is 643MPa; magnetic induction intensity B 50 And high frequency iron loss W 1.0 / 400 All tests were carried out according to the method of GB / T 3655-2008, and the yield strength R el And tensile strength R m All tests were carried out in accordance with the method of GB / T 3075-2008.

[0064] Table 5

[0065]

[0066] Comparative Example 1

[0067] (1) After smelting and continuous casting of molten iron, a cast billet is obtained, and the thickness of the cast billet is 240 mm. The cast billet is hot rolled, and the hot rolling conditions include: the starting rolling temperature is 1150° C., the final rolling temperature is 870° C., and the coiling temperature is 705° C. to obtain a steel plate, and the thickness of the steel plate is 2.0 mm. The steel plate is normalized, and the normalization conditions include: the temperature is 960° C., the time is 2 min, and then cooled, followed by pickling, and then cold rolled, and the cold rolling is rolled to 0.15 by a 20-roll rolling mill. mm thickness, and the cold rolling passes are 4-6 passes, the reduction rate of each of the first 3-4 passes is ≥35%, and the reduction rate of each of the last 1-2 passes is ≥30%, to obtain a steel coil, and the steel coil is placed in a high-temperature tubular annealing furnace, and annealed under the protection of a mixed gas of hydrogen and nitrogen. The annealing conditions include: a temperature of 840° C., a time of 30 seconds, a hydrogen content of 20% by volume, and a nitrogen content of 80% by volume in the mixed gas, to obtain an annealed steel coil;

[0068] (2) coating the upper surface and the lower surface of the annealed steel coil with a semi-organic coating to obtain non-oriented silicon steel;

[0069] The chemical composition content (weight percentage) of the ingot in step (1) of this comparative example is shown in Table 6 (the remainder not shown in Table 6 is Fe and unavoidable impurities). The chemical composition content of the non-oriented silicon steel obtained in step (2) is the same as that of the ingot. The magnetic induction intensity B of the non-oriented silicon steel is 50 1.65T, high frequency iron loss W 1.0 / 400 =12.5W / Kg, yield strength R el The tensile strength is 520MPa and the m is 575MPa; magnetic induction intensity B 50 And high frequency iron loss W 1.0 / 400 All tests were carried out according to the method of GB / T 3655-2008, and the yield strength R el And tensile strength R m All tests were carried out in accordance with the method of GB / T 3075-2008.

[0070] Table 6

[0071]

[0072] Comparative Example 2

[0073] (1) After smelting and continuous casting of molten iron, a cast billet is obtained, and the thickness of the cast billet is 240 mm. The cast billet is hot rolled, and the hot rolling conditions include: the starting rolling temperature is 1140° C., the final rolling temperature is 865° C., and the coiling temperature is 685° C. to obtain a steel plate, and the thickness of the steel plate is 2.0 mm. The steel plate is normalized, and the normalization conditions include: the temperature is 940° C., the time is 2 min, and then cooled, followed by pickling, and then cold rolled, and the cold rolling is rolled to 0.15 by a 20-roll rolling mill. mm thickness, and the cold rolling passes are 4-6 passes, the reduction rate of each of the first 3-4 passes is ≥35%, and the reduction rate of each of the last 1-2 passes is ≥30%, to obtain a steel coil, and the steel coil is placed in a high-temperature tubular annealing furnace, and annealed under the protection of a mixed gas of hydrogen and nitrogen. The annealing conditions include: a temperature of 680° C., a time of 30 seconds, a hydrogen content of 20% by volume, and a nitrogen content of 80% by volume in the mixed gas, to obtain an annealed steel coil;

[0074] (2) coating the upper surface and the lower surface of the annealed steel coil with a semi-organic coating to obtain non-oriented silicon steel;

[0075] The chemical composition content (weight percentage) of the ingot in step (1) of this embodiment is shown in Table 7 (the remainder not shown in Table 7 is Fe and unavoidable impurities). The chemical composition content of the non-oriented silicon steel obtained in step (2) is the same as that of the ingot. The magnetic induction intensity B of the non-oriented silicon steel is 50 is 1.58T, high frequency iron loss W 1.0 / 400 =21.9W / Kg, yield strength R el The tensile strength is 690MPa and the m is 743MPa; magnetic induction intensity B 50 And high frequency iron loss W 1.0 / 400 All tests were carried out according to the method of GB / T 3655-2008, and the yield strength R el And tensile strength R m All tests were carried out in accordance with the method of GB / T 3075-2008.

[0076] Table 7

[0077]

[0078] It can be seen from the above results that the present invention reasonably controls the ratio of Mn to silicon and aluminum content through composition and process design, thereby better exerting the solid solution strengthening effect of Mn. The obtained non-oriented silicon steel has excellent mechanical properties while ensuring magnetic properties.

[0079] It should be understood that parts not elaborated in detail in this specification belong to the prior art.

[0080] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A non-oriented silicon steel, characterized in that: The non-oriented silicon steel contains the following chemical components in weight percentage: C: 0.001-0.005%, Si: 2.4-3%, Mn: 0.25-0.5%, Al: 0.7-1.1%, P≤0.02%, S≤0.005%, Sn: 0.005-0.025%; wherein, Mn / (Si+Al)≥8%, Si+Mn+Al: 3.3-4.6%; the rest is Fe and unavoidable impurities.

2. The non-oriented silicon steel according to claim 1, characterized in that: The magnetic induction intensity B of the non-oriented silicon steel 50 1.60-1.69T, high frequency iron loss W 1.0 / 400 11.5-18.5W / Kg, yield strength R el 560-645MPa, tensile strength R m It is 610-700MPa.

3. A method for preparing the non-oriented silicon steel according to claim 1 or 2, characterized in that: The method comprises the following steps: (1) hot rolling the ingot to obtain a steel plate, normalizing, pickling and cold rolling the steel plate in sequence to obtain a steel coil, and annealing the steel coil to obtain an annealed steel coil; (2) coating a semi-organic coating on the surface of the annealed steel coil to obtain non-oriented silicon steel.

4. The method according to claim 3, characterized in that In step (1), molten iron is smelted and continuously cast to obtain a cast billet having a thickness of 200-240 mm.

5. The method according to claim 3 or 4, characterized in that: In step (1), the hot rolling conditions include: the starting rolling temperature is 1100-1200°C, the final rolling temperature is 850-890°C, and the coiling temperature is 660-720°C.

6. The method according to claim 3 or 4, characterized in that: In step (1), the thickness of the steel plate is 1.8-2.2 mm.

7. The method according to claim 3, characterized in that In step (1), the normalization conditions include: temperature of 900-1000° C. and time of 1-3 min.

8. The method according to claim 3 or 7, characterized in that: In step (1), the cold rolling is performed in 4-6 passes, the reduction ratio of each of the first 3-4 passes is ≥35%, and the reduction ratio of each of the last 1-2 passes is ≥30%.

9. The method according to claim 3, characterized in that: In step (1), the steel coil is annealed under the protection of a mixed gas of hydrogen and nitrogen; The content of hydrogen in the mixed gas is ≥20 volume %.

10. The method according to claim 3, characterized in that: In step (1), the annealing conditions include: temperature of 700-800° C. and time of 20-60 s.

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