Low-surface-hardness oriented silicon steel production method for removing magnesium silicate bottom layer through laser technology

Abstract

The invention discloses a low-surface-hardness oriented silicon steel production method for removing a magnesium silicate bottom layer by using a laser process. The method comprises the following steps: smelting, carrying out vacuum treatment and casting into a blank; heating the casting blank; hot rolling; performing coiling; normalizing is conducted; performing primary cold rolling; carrying out decarburization annealing; nitriding treatment is carried out; coating a conventional high-temperature annealing isolating agent which takes MgO as a main component; performing high-temperature annealing; uncoiling and carrying out laser treatment under a protective atmosphere; stretching, flattening and annealing; and coating a semi-organic insulating coating. After the magnesium silicate bottom layer is removed through the laser process and the semi-organic insulating coating is coated, the surface hardness HV 0.5 can be remarkably reduced to not more than 120, the oriented silicon steel punching performance, namely the number of punched sheets of a blade die at a time, is improved by 8-15 times compared with the existing variety, the magnetic performance B800 is larger than or equal to 1.83 T, the magnetic performance P17 / 50 is smaller than or equal to 1.45 W / kg, and the finished product is low in surface hardness and excellent in punching machinability.

Description

Technical Field

[0001] The present invention relates to a cold-rolled grain-oriented silicon steel and a production method thereof, and more particularly to a production method of low surface hardness grain-oriented silicon steel using a laser process to remove the magnesium silicate bottom layer. Background Art

[0002] Grain-oriented silicon steel is mainly used as the core of transformers and is the "heart" material of various power transmission and transformation transformers. It is an important soft magnetic alloy indispensable in the power and electronics industries. The quality grade of grain-oriented silicon steel plays a decisive role in the development of the national power industry. Grain-oriented silicon steel is regarded as an important symbol of the steel manufacturing technology level because of its most complex manufacturing process, high technical content and high added value. Grain-oriented silicon steel can be divided into ordinary grain-oriented silicon steel (CGO) and high magnetic induction grain-oriented silicon steel (HiB) according to the manufacturing process and magnetic induction. Typically, ordinary grain-oriented silicon steel is the grain-oriented silicon steel developed by the Upper Iset and Novolipetsk Steel Works in Russia, etc., with Cu2S as the main inhibitor. Typically, high magnetic induction grain-oriented silicon steel is the high magnetic induction grain-oriented silicon steel (HiB) with higher magnetic induction and lower iron loss first produced by Nippon Steel using the single large reduction cold rolling method, with AlN as the main and MnS as the auxiliary inhibitor. Later, the Yawata Works of Nippon Steel first proposed not to use the precipitated AlN before decarburizing annealing as an inhibitor, that is, not to use the "inherent inhibitor", but to carry out nitriding treatment after decarburizing annealing, so that the inhibitor formed by N and Als in the steel, that is, the inhibitor obtained by the subsequent process, can reduce the slab heating temperature to 1150-1200 °C. Energy conservation and environmental protection have become a global trend today. At the same time, with the large-scale power construction in China, the domestic demand for grain-oriented silicon steel is increasing, and there is a huge market space. Therefore, the development of high-performance grain-oriented silicon steel is becoming more and more urgent, and higher magnetic induction and lower iron loss have always been the pursuit and goal of grain-oriented silicon steel production.

[0003] Most domestic and foreign wind power motors, thermal power motors and nuclear power motors use high-grade non-oriented silicon steel. However, in recent years, with the rapid development of the motor industry, in order to further improve the efficiency of motors, some users have improved the design and selected grain-oriented silicon steel with high magnetic polarization intensity as the main material for the core or other components. At the same time, in addition to meeting excellent electromagnetic performance, in order to meet the requirements of punching process, it is required that the surface of the grain-oriented silicon steel sheet used for large motors has no magnesium silicate bottom layer. However, when used as the main material for the core, an insulating isolation coating still needs to be applied to meet insulation, adhesion, low surface hardness, etc., while when used for other components, the surface of the steel sheet needs to be completely free of the magnesium silicate bottom layer to ensure excellent welding performance. At the same time, the finished product of non-oriented silicon steel without magnesium silicate bottom layer without applying an insulating coating can be used as the base material for preparing ultra-thin grain-oriented silicon steel strips with a thickness of 0.03-0.10 mm.

[0004] After retrieval:

[0005] The document with Chinese Patent Application No. CN201210315658.2 discloses "A High Magnetic Induction Grain Oriented Electrical Steel and Its Manufacturing Method". The weight percentage of its chemical elements is as follows: C 0.035 - 0.120%, Si 2.9 - 4.5%, Mn 0.05 - 0.20%, P 0.005 - 0.050%, S 0.005 - 0.012%, Als 0.015 - 0.035%, N 0.001 - 0.010%, Cr 0.05 - 0.30%, Sn 0.005 - 0.090%, V ≤ 0.0100%, Ti ≤ 0.0100%, at least one of the trace elements Sb, Bi, Ni and Mo, and Sb + Bi + Ni + Mo: 0.0015 - 0.0250%, with the balance being Fe and other inevitable impurities; the manufacturing method includes obtaining a slab after smelting and casting, hot rolling, normalizing annealing, cold rolling, decarburizing annealing, nitriding treatment, high-temperature annealing after applying an MgO coating on the steel plate, applying an insulating coating, and hot tensile leveling annealing to obtain a high magnetic induction grain oriented electrical steel. This document adopts a one-rolling process of low-temperature hot rolling and nitriding treatment, but the surface is in the mode of the traditional magnesium silicate bottom layer + T2 tension coating of grain oriented electrical steel, with a high surface hardness of the steel plate, which is not conducive to stamping processing.

[0006] The document with Chinese Patent Application No. CN201911126524.4 discloses "A Grain Oriented Electrical Steel Capable of Reducing Surface Hardness and Its Preparation Method". The weight percentage of its main chemical components is as follows: C 0.020 - 0.095%, Si 2.80 - 3.60%, Als 0.020% - 0.035%, N 0.0050% - 0.0100%, Mn 0.010% - 1.00%, S 0.0030% - 0.0300%. Through low-temperature or high-temperature hot rolling at 1100°C - 1400°C and normalizing treatment of the hot-rolled sheet at 1000°C - 1150°C, after one cold rolling, decarburizing annealing, nitriding treatment (no nitriding when the hot-rolled slab is heated at ≥ 1260°C), applying a magnesium oxide isolation coating, and high-temperature annealing, a non-magnesium silicate bottom layer grain oriented electrical steel with a thickness of 0.15 mm - 0.50 mm is obtained, and after applying a semi-organic insulating coating, a grain oriented electrical steel finished product with 800 B 17 / 50 ≥ 1.80 T, P

[0007] It can be seen that the above-mentioned literature or surface is a traditional oriented silicon steel with a magnesium silicate bottom layer + a T2 tension coating, which is not conducive to punching processing (the surface hardness cannot be reduced, and the punching property is difficult to improve), or the inhibitor is unstable during the high-temperature annealing process, resulting in unstable magnetic properties, and it is difficult to obtain an oriented silicon steel without a magnesium silicate bottom layer with a smooth surface across the whole plate (the surface hardness cannot be reduced, and the punching property is difficult to improve), all of which are essentially different from the present invention. Summary of the Invention

[0008] The present invention aims to overcome the deficiencies of the prior art and provides a production method of non-magnesium silicate bottom layer low surface hardness oriented silicon steel with excellent finished product stamping processability. After removing the magnesium silicate bottom layer by a laser process and coating a semi-organic insulating coating, the surface hardness HV 0.5 can be significantly reduced to no more than 120, and the punching property of the oriented silicon steel, that is, the number of punchings in one pass of the cutting die, can be increased by 8 to 15 times compared with the existing varieties, and the magnetic properties B 800 ≥1.83T, P 17 / 50 ≤1.45W / kg.

[0009] Measures to achieve the above object:

[0010] A production method of low surface hardness oriented silicon steel using a laser process to remove the magnesium silicate bottom layer, the steps are as follows:

[0011] 1) Smelting, vacuum treatment, and casting into billets;

[0012] 2) Heating the billets, with the heating temperature controlled at 1100 - 1400 °C;

[0013] 3) Performing hot rolling, controlling the final rolling temperature at 850 - 1100 °C, and the thickness of the hot rolled plate at 2.0 - 2.8 mm;

[0014] 4) Coiling, controlling the coiling temperature not exceeding 600 °C;

[0015] 5) Normalizing, controlling the normalizing temperature at 1000 - 1150 °C, and holding at this temperature for 30 - 180 s;

[0016] 6) Performing first cold rolling, with at least one pass of aging rolling in the cold rolling, controlling the aging temperature at 160 - 250 °C, and the finished product thickness at 0.15 - 0.35 mm;

[0017] 7) Performing decarburization annealing in a wet protective atmosphere, controlling the decarburization annealing temperature at 750 - 900 °C, and holding at this temperature for 60 - 180 s, with the dew point at 25 °C, and the protective atmosphere being a mixed gas of wet H2 and N2, where the volume content of H2 is 15 - 80%;

[0018] 8) Performing nitriding treatment:

[0019] When the heating temperature of the slab is not lower than 1260 °C, nitriding is not required;

[0020] When the heating temperature of the slab is lower than 1260 °C, nitriding is required. The nitriding atmosphere is a wet mixed gas of H2, N2 and NH3, where the volume content of H2 is 15-80%, and the amount of nitrogen infiltrated is controlled at 50-350 PPm;

[0021] 9) Coating with a conventional high-temperature annealing release agent mainly composed of MgO;

[0022] 10) Conducting conventional high-temperature annealing;

[0023] 11) Unwinding and laser treatment under a protective atmosphere:

[0024] Laser treatment parameters: The average power of the continuous laser is 20-3500 W; the laser pulse repetition frequency is 1-

[0025] 160 kHz; the laser pulse width is 1-10 ms; the fill line spacing is 0.01-0.06 mm; the scanning rate is

[0026] 10-8000 mm / s; the focus of the beam is focused on the surface of the steel plate; the protective gas is nitrogen or argon, and the protective gas flow rate is 1-50 L / min;

[0027] 12) Conducting conventional stretch leveling annealing treatment on the steel strip;

[0028] 13) Coating a semi-organic insulating coating and controlling the single-sided coating thickness at 0.5-5.0 μm.

[0029] Preferably: The average power of the continuous laser is 45-3420 W.

[0030] Preferably:: The laser pulse repetition frequency is 8-145 kHz.

[0031] Preferably: The fill line spacing is 0.02-0.05 mm.

[0032] Preferably: The scanning rate is 20-7750 mm / s.

[0033] Preferably: The laser pulse width is 1.5-9 ms.

[0034] It lies in that: the composition and weight percentage content of the ultra-high magnetic induction oriented silicon are as follows: C: 0.015 - 0.095%, Si: 2.50 - 4.50%, Als: 0.010 - 0.040%, N: 0.0050 - 0.0100%, Mn: 0.010 - 1.00%, S: 0.0030 - 0.0300%, and any at least two of P, Cu, Sn, Bi, Sb, Cr and As are compound-added and satisfy (P + Cu + Sn + Bi + Sb + Cr + As) ≤ 1.80%, and the rest is iron and inevitable impurities.

[0035] It lies in that: the composition and weight percentage content of the semi-organic insulating coating are as follows: water-based resin 2.0 - 30.0%, aluminum dihydrogen phosphate 10.0 - 50.0%, boric acid 1.0 - 10.0%, water-based auxiliary agent 1.0 - 5.0%, and the rest is water, and it satisfies that the non-volatile content after the coating is conventionally dried is 30 - 80%.

[0036] The mechanism and function of the main processes in the present invention

[0037] The reason why the present invention controls the heating temperature of the steel billet at 1100 - 1400 °C is that it is necessary to ensure that part of the AlN in the continuous casting billet is solid-solved or completely and fully solid-solved to form AlN second-phase particles with appropriate sizes in the subsequent processes.

[0038] The reason why the present invention limits the finish rolling temperature within the range of 850 - 1100 °C to ensure hot rolling within a relatively high temperature range is that it is necessary to ensure hot rolling within a relatively high temperature range and a relatively high finish rolling temperature so that no large-particle AlN and other second-phase particles precipitate during hot rolling.

[0039] The reason why the present invention controls the normalizing temperature at 1000 - 1150 °C and holds at this temperature for 30 - 180 s is that in order to ensure that the AlN second-phase particles with appropriate sizes are completely solid-solved to form (or form during nitriding treatment) favorable second phases. When normalizing at a temperature lower than 1000 °C, since the temperature is low, it is difficult for AlN to be solid-solved; when higher than 1150 °C, the grains of the steel strip coarsen, resulting in grain growth after primary recrystallization annealing and increasing costs at the same time.

[0040] The reason why the present invention controls at least one pass of aging rolling at 160 - 250 °C during cold rolling is that cold rolling aging can increase the content of carbon and nitrogen solid-solved in the steel. During cold rolling, the solid-solved carbon and nitrogen aggregate at dislocations, hinder the movement of dislocations, change the normal slip system, promote the formation of more transition zones, and form more favorable primary recrystallization texture components after cold rolling and annealing.

[0041] The reason for the present invention to control the decarburizing annealing temperature at 750 - 900 °C, hold for 60 - 180 s at this temperature, the dew point in the furnace at 15 - 55 °C, and the protective atmosphere as a wet H2 and N2 mixed gas with the H2 volume content of 15 - 80% is as follows: to complete primary recrystallization, so that there are a sufficient number of

[110] (001) grains (secondary nuclei) in the matrix, as well as a primary recrystallization structure and texture conducive to their growth; to reduce the carbon in the steel to below 0.0030% to ensure that the subsequent high-temperature annealing is in a single α phase; and to form a dense and uniform SiO2 film on the surface of the steel strip.

[0042] The reason for the present invention to control the heating temperature of the continuous casting billet at 1100 - 1260 °C and require nitriding treatment in the subsequent process, while not requiring nitriding treatment in the subsequent process when the heating temperature is at 1260 - 1400 °C, is that when the heating temperature of the continuous casting billet is at 1100 - 1260 °C, AlN in the continuous casting billet can only be partially dissolved, and nitriding treatment must be carried out in the annealing process to increase the content of AlN second-phase particles to ensure sufficient inhibitory force to obtain a perfect secondary recrystallization structure and texture; when the heating temperature is at 1260 - 1400 °C, AlN in the continuous casting billet can be completely and fully dissolved, and a sufficient amount of AlN second-phase particles can be obtained in the normalizing and annealing processes of the hot-rolled sheet to ensure sufficient inhibitory force to obtain a perfect secondary recrystallization structure and texture, so nitriding treatment is not required.

[0043] The purpose of the nitriding treatment is to ensure that there is sufficient nitrogen content in the steel to generate AlN and (Si,Al)N, form a favorable second phase, inhibit the normal growth of primary grains during high-temperature annealing, and promote the perfection of secondary recrystallization.

[0044] The present invention coats a high-temperature annealing release agent with MgO as the main component, which plays a role in isolating the steel coils layer by layer during high-temperature annealing.

[0045] The reason for the present invention to control the laser processing parameters: the average power of the continuous laser is 20 - 3500 W; the laser pulse repetition frequency is 1 - 160 kHz; the laser pulse width is 1 - 10 ms; the filling line spacing is 0.01 - 0.06 mm; the scanning speed is 10 - 8000 mm / s; the focus of the light beam is focused on the surface of the steel plate; the protective gas is nitrogen or argon, and the protective gas flow rate is 1 - 50 L / min; is based on the difference in the damage threshold between the magnesium silicate bottom layer and the matrix, and realizes the removal of the magnesium silicate bottom layer with low damage and smooth surface on the whole plate of grain-oriented silicon steel through processes such as precise ablation of the magnesium silicate bottom layer by high-energy pulsed laser, fast scanning of the galvanometer, purging of the protective gas, and filtration by the fume extractor. Its feature is that the position of the galvanometer can be longitudinally adjusted to make the focus of the light beam focus on the surface of the steel plate, realizing the efficiency of removing the bottom magnesium silicate layer, and it is easy to be automatically controlled, with a high surface finish effect on the whole plate. By carrying out tension leveling annealing treatment on the steel strip, high magnetic induction grain-oriented silicon steel without a magnesium silicate bottom layer with a smooth surface on the whole plate is obtained.

[0046] However, when the average power of the laser is lower than 20 W, incomplete removal of the magnesium silicate bottom layer of the final product will occur, and full-surface smoothness cannot be achieved (the product has a high surface hardness and poor steel plate stamping processability); when the average power of the laser is higher than 3500 W, local heating of the steel strip will occur, resulting in plastic deformation and poor plate shape; when the laser pulse repetition frequency is lower than 1 kHz, incomplete removal of the magnesium silicate bottom layer of the final product will occur, and full-surface smoothness cannot be achieved (the product has a high surface hardness and poor steel plate stamping processability); when the average power of the laser is higher than 160 kHz, local heating of the steel strip will occur, resulting in plastic deformation and poor plate shape; when the laser pulse width is lower than 1 ms, incomplete removal of the magnesium silicate bottom layer of the final product will occur, and full-surface smoothness cannot be achieved (the product has a high surface hardness and poor steel plate stamping processability); when the laser pulse width is higher than 10 ms, local heating of the steel strip will occur, resulting in plastic deformation and poor plate shape; when the laser pulse filling line spacing is lower than 0.01 mm, local heating of the steel strip will occur, resulting in plastic deformation and poor plate shape; when the laser filling line spacing is higher than 0.06 mm, incomplete removal of the magnesium silicate bottom layer of the final product will occur, and full-surface smoothness cannot be achieved (the product has a high surface hardness and poor steel plate stamping processability); when the laser scanning rate is lower than 10 mm / s, incomplete removal of the magnesium silicate bottom layer of the final product will occur, and full-surface smoothness cannot be achieved (the product has a high surface hardness and poor steel plate stamping processability); when the laser scanning rate is higher than 8000 mm / s, local heating of the steel strip will occur, resulting in plastic deformation and poor plate shape.

[0047] In the present invention, a semi-organic insulating coating is applied after tensile leveling annealing to obtain an oriented silicon steel sheet with a low surface hardness.

[0048] Compared with the prior art, after removing the magnesium silicate bottom layer by a laser process and applying a semi-organic insulating coating in the present invention, the surface hardness HV 0.5 can be significantly reduced to no more than 120, and the punching performance of the oriented silicon steel, that is, the number of punched sheets in one die cutting, is increased by 8 to 15 times compared with the existing varieties, and the magnetic properties B 800 ≥1.83 T, P 17 / 50 ≤1.45 W / kg, the surface hardness of the finished product is low, and the stamping processability is excellent. Specific embodiments

[0049] The present invention will be described in detail below:

[0050] Table 1 is a list of component values of each embodiment and comparative example of the present invention;

[0051] Table 2 is a list of main process parameters of each embodiment and comparative example of the present invention;

[0052] Table 3 is a list of performance detection situations of each embodiment and comparative example of the present invention.

[0053] The embodiments of the present invention are produced according to the following steps:

[0054] 1) Smelting, vacuum treatment, and casting into billets;

[0055] 2) Heating the billets, with the heating temperature controlled at 1100 - 1400 °C;

[0056] 3) Performing hot rolling, controlling the final rolling temperature at 850 - 1100 °C, and the thickness of the hot rolled plate at 2.0 - 2.8 mm;

[0057] 4) Coiling, controlling the coiling temperature not exceeding 600 °C;

[0058] 5) Normalizing, controlling the normalizing temperature at 1000 - 1150 °C, and holding at this temperature for 30 - 180 s;

[0059] 6) Performing a first cold rolling, with at least one pass of age rolling during cold rolling, controlling the age temperature at 160 - 250 °C, and the finished product thickness at 0.15 - 0.35 mm;

[0060] 7) Performing decarburization annealing under a wet protective atmosphere, controlling the decarburization annealing temperature at 750 - 900 °C, and holding at this temperature for 60 - 180 s, with a dew point of 25 °C; the protective atmosphere is a mixed gas of wet H2 and N2, where the volume content of H2 is 15 - 80%;

[0061] 8) Performing nitriding treatment:

[0062] When the heating temperature of the billets is not lower than 1260 °C, nitriding is not required;

[0063] When the heating temperature of the billets is lower than 1260 °C, nitriding is required, and the nitriding atmosphere is a mixed gas of wet H2, N2, and NH3, where the volume content of H2 is 15 - 80%, and the amount of nitrogen infiltrated is controlled at 50 - 350 ppm;

[0064] 9) Coating with a conventional high - temperature annealing release agent mainly composed of MgO;

[0065] 10) Conventionally performing high - temperature annealing;

[0066] 11) Uncoiling and performing laser treatment under a protective atmosphere:

[0067] Laser treatment parameters: The average power of the continuous laser is 20 - 3500 W; the laser pulse repetition frequency is 1 -

[0068] 160 kHz; the laser pulse width is from 1 to 10 ms; the filling line spacing is from 0.01 to 0.06 mm; the scanning rate is from 10 to 8000 mm / s; the focus of the beam is focused on the surface of the steel plate; the protective gas is nitrogen or argon, and the flow rate of the protective gas is from 1 to 50 L / min;

[0069] 12) Perform conventional tensile leveling annealing treatment on the steel strip;

[0070] 13) Coat a semi-organic insulating coating and control the single-sided coating thickness to be from 0.5 to 5.0 μm.

[0071] Table 1 List of chemical component values of each example and comparative example of the present invention (wt%)

[0072]

[0073]

[0074] As can be seen from Table 1, in Comparative Example Q1, Als < 0.010%, the Als content is low, the number of AlN precipitates after decarburization (nitriding) decreases, the inhibitory force during high-temperature annealing decreases, and the finished product magnetic properties decrease; in Comparative Example Q2, Als > 0.040%, the solubility product of Als and N is high, and it is difficult to completely dissolve during heating at 1100°C to 1400°C, resulting in a decrease in the effective precipitation amount after decarburization (nitriding), thereby causing a decrease in the inhibitory force during high-temperature annealing and a decrease in the finished product magnetic properties; in Comparative Example Q3, (P + Cu + Sn + Bi + Sb + Cr + As) > 1.80%, the content of interfacial enrichment elements is too high, and the hot-rolled edge cracking is extremely large, making it difficult to carry out production smoothly.

[0075] Table 2 List of main process parameters of each example and comparative example of the present invention

[0076]

[0077]

[0078] Continued Table 2

[0079]

[0080] Note: In Table 2, except for the listed materials in the semi-organic insulating coating, the rest is water; in Table 2, the protective gas is nitrogen or argon, and the two can be interchanged.

[0081] As can be seen from Table 2:

[0082] In comparative example Q1, the slab hot rolling heating temperature is less than 1100°C, the final rolling temperature is less than 850°C, AlN cannot be completely dissolved during the heating process, and the final rolling temperature is low, large particles of AlN will be precipitated, and the effective AlN precipitation in the subsequent process will be reduced. The normalization time is less than 30s, small particles of AlN cannot be completely dissolved, and the effective precipitation amount after decarburization (nitriding) is reduced, resulting in reduced inhibition during high-temperature annealing and reduced magnetic properties of the finished product; in comparative example Q2, the slab hot rolling heating temperature is greater than 1400°C, the heating temperature is high, the ingot grain size grows, resulting in the hot-rolled plate and the primary recrystallization annealed plate grain size At the same time, if the heating temperature is too high, the burning loss of the ingot will be aggravated, the yield rate will be reduced, and the normalizing time is greater than 180s. If the normalizing time is too long, the favorable precipitation will be aggregated and coarsened, thereby reducing the inhibition force in the subsequent annealing process. At the same time, if the heating time is too long, the grains of the hot-rolled plate will grow, which will lead to the growth of the grain size of the primary recrystallization annealing plate, the instability of the secondary recrystallization, and the reduction of the magnetic properties of the finished product; in the comparative example Q3, the normalizing temperature is less than 1000℃, and the small particles of AlN in the normalizing are difficult to dissolve, and the number of effective precipitations after decarburization (nitriding) is reduced, which leads to the reduction of inhibition force in high-temperature annealing and the reduction of the magnetic properties of the finished product.

[0083] In comparative example Q1, the average power is less than 20W, the laser pulse repetition frequency is less than 1kHz, the pulse width is less than 1ms, and the scanning rate is less than 10mm / s, resulting in incomplete removal of the magnesium silicate bottom layer of the final product, and the entire plate surface cannot be smooth. The product surface hardness is high, the steel plate stamping processability is poor, the filling line spacing is less than 0.01mm, and the steel strip is locally heated to produce plastic deformation, resulting in poor plate shape; in comparative example Q2, the average power is less than 20W, the laser pulse repetition frequency is less than 1kHz, the pulse width is less than 1ms, and the scanning rate is less than 10mm / s, resulting in incomplete removal of the magnesium silicate bottom layer of the final product. The whole plate cannot be smooth, the surface hardness of the product is high, the stamping processability of the steel plate is poor, the filling line spacing is less than 0.01mm, and the local heating of the steel strip produces plastic deformation, resulting in a poor plate shape; in the comparative example Q3, the average power is greater than 3500W, the laser pulse repetition frequency is greater than 160kHz, the pulse width is greater than 10ms, the scanning rate is greater than 8000mm / s, the local heating of the steel strip produces plastic deformation, resulting in a poor plate shape, the filling line spacing is greater than 0.06mm, the magnesium silicate bottom layer of the product is not completely removed, the whole plate surface cannot be smooth, the product surface hardness is high, and the stamping processability of the steel plate is poor.

[0084] Table 3 Performance test results of various embodiments of the present invention and comparative examples

[0085]

[0086]

[0087] It can be seen from Table 3 that the magnetic induction B of the finished product in comparative example Q1 is 800 <1.83T, loss P17 / 50 > 1.45 W / kg, the content of water-based resin in the insulating paint is low, the plate shape is poor, the magnesium silicate bottom layer remains on the plate surface, the surface hardness of the product is high, and the stamping processability is poor; in Comparative Example Q2, the finished product magnetic induction B 800 < 1.83 T, loss P 17 / 50 > 1.45 W / kg, the content of water-based resin in the insulating paint is low, the plate shape is poor, the magnesium silicate bottom layer remains on the plate surface, the surface hardness of the product is high, and the stamping processability is poor; in Comparative Example Q3, since (P + Cu + Sn + Bi + Sb + Cr + As)> 1.80%, the production process cannot proceed and it is a waste product.

[0088] This specific embodiment is only the best example and not a restrictive implementation of the technical solution of the present invention.

Claims

1. A production method of low surface hardness grain-oriented silicon steel using a laser process to remove the magnesium silicate bottom layer, the steps are as follows: 1) Smelt, perform vacuum treatment, and cast into billets; 2) Heat the billets, and control the heating temperature at 1100 - 1400 °C; 3) Perform hot rolling, control the finish rolling temperature at 850 - 1100 °C, and the thickness of the hot rolled sheet at 2.0 - 2.8 mm; 4) Perform coiling, and control the coiling temperature not exceeding 600 °C; 5) Perform normalizing, control the normalizing temperature at 1000 - 1150 °C, and hold at this temperature for 30 - 180 s; 6) Perform a first cold rolling, and perform at least one pass of aging rolling during cold rolling, control the aging temperature at 160 - 250 °C, and the finished product thickness at 0.15 - 0.35 mm; 7) Perform decarburization annealing under a wet protective atmosphere, control the decarburization annealing temperature at 750 - 900 °C, and hold at this temperature for 60 - 180 s, with a dew point of 25 °C; the protective atmosphere is a mixed gas of wet H2 and N2, where the volume content of H2 is 15 - 80%; 8) Perform nitriding treatment: When the heating temperature of the billet is not lower than 1260 °C, nitriding is not required; When the heating temperature of the billet is lower than 1260 °C, nitriding is required, and its nitriding atmosphere is a mixed gas of wet H2, N2 and NH3, where the volume content of H2 is 15 - 80%, and control the nitrogen infiltration amount at 50 - 350 PPm; 9) Coat a conventional high-temperature annealing release agent with MgO as the main component; 10) Perform conventional high-temperature annealing; 11) Uncoil and perform laser treatment under a protective atmosphere: Laser treatment parameters: The average power of the continuous laser is 20 - 3500 W; the laser pulse repetition frequency is 1 - 160 kHz; the laser pulse width is 1 - 10 ms; the filling line spacing is 0.01 - 0.06 mm; the scanning speed is 10 - 8000 mm / s; the focus of the beam is focused on the steel plate surface; the protective gas is nitrogen or argon, and the protective gas flow rate is 1 - 50 L / min; 12) Perform a conventional stretch leveling annealing treatment on the steel strip; 13) Coat a semi-organic insulating coating, and control the single-sided coating thickness at 0.5 - 5.0 μm.

2. The method for producing low surface hardness grain-oriented silicon steel by using a laser process to remove the magnesium silicate bottom layer as claimed in claim 1, wherein: The average power of the continuous laser is 50 - 3350 W.

3. A method for producing low surface hardness grain-oriented silicon steel by removing a magnesium silicate bottom layer using a laser process, characterized in that: The laser pulse repetition frequency is 3 - 150 kHz.

4. A method for producing low surface hardness grain-oriented silicon steel by removing the magnesium silicate bottom layer using a laser process, characterized in that: The filling line spacing is 0.02 - 0.05 mm.

5. A method for producing low surface hardness grain-oriented silicon steel by using a laser process to remove a magnesium silicate bottom layer, characterized in that: The scanning speed is 25 - 7800 mm / s.

6. The production method of low surface hardness grain-oriented silicon steel for removing the magnesium silicate bottom layer by using a laser process as described in claim 1, characterized in that: The laser pulse width is 1.5 - 9 ms.

7. A method for producing low surface hardness grain-oriented silicon steel by removing the magnesium silicate bottom layer using a laser process, characterized in that: The component composition and weight percentage content of the ultra-high magnetic induction grain-oriented silicon are as follows: C: 0.015 - 0.095%, Si: 2.50 - 4.50%, Als: 0.010 - 0.040%, N: 0.0050 - 0.0100%, Mn: 0.010 - 1.00%, S: 0.0030 - 0.0300%, any at least two of P, Cu, Sn, Bi, Sb, Cr and As are added in combination and satisfy (P + Cu + Sn + Bi + Sb + Cr + As) ≤ 1.80%, and the rest are iron and inevitable impurities.

8. A method for producing low surface hardness grain-oriented silicon steel by removing the magnesium silicate bottom layer using a laser process, characterized in that: The composition and weight percentage content of the semi-organic insulating coating are as follows: water-based resin 2.0 - 30.0%, aluminum dihydrogen phosphate 10.0 - 50.0%, boric acid 1.0 - 10.0%, water-based additive 1.0 - 5.0%, and the balance is water, and it meets the requirement that the non-volatile content of the coating after conventional drying is 30 - 80%.

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