Method for improving performance of insulating coating on surface of non-oriented silicon steel

Abstract

The invention discloses a method for improving the performance of an insulating coating on the surface of non-oriented silicon steel, and belongs to the technical field of silicon steel production. The steel strip is subjected to continuous annealing, in the circulating jet cooling section of continuous annealing, an oxidation film is formed on the surface of the steel strip by inputting air or humidifying nitrogen, and the thickness of the oxidation film is 0.05-3.0 microns. On the basis that the thickness of the coating is not increased and other characteristics of the original coating are not influenced, the composite coating with the inter-layer resistance characteristic is produced.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon steel production, relates to a production method of cold-rolled non-oriented electrical steel coating products, and specifically relates to a method for improving the performance of insulating coating on the surface of non-oriented silicon steel. Background Art

[0002] Cold-rolled non-oriented electrical steel is a metallic soft magnetic functional material, usually used to process into the iron core components required for electromagnetic conversion; in the production of the motor industry, it mainly refers to the stator and rotor iron cores of the motor. In order to reduce the iron core loss and improve the conversion efficiency, the surface of the electrical steel product needs to be coated with an insulating coating. Under the condition of ensuring the iron core stacking coefficient (net iron core ratio), the insulating coating needs to have a high interlayer resistance, good adhesion and corrosion resistance, and good punching or blanking properties during the preparation of the iron core; in special uses, the coating also needs to have heat resistance (iron core stress relief heat treatment), refrigerant erosion resistance (refrigeration compressor motor field) and other requirements, which is one of the key technical components of the functionality of electrical steel functional materials.

[0003] In the industrial-scale production of non-oriented electrical steel products, the finished product process usually adopts a multifunctional continuous annealing furnace. After the heat treatment of the base material is completed, the steel strip is coated with the corresponding coating liquid, dried and sintered to complete the process preparation of the finished product.

[0004] According to the demand and production method, the coating types of non-oriented electrical steel are generally divided into inorganic coating, organic coating, semi-organic coating and self-adhesive coating; and combined with the coating process, the production of thin coating (less than 0.4μm), conventional thickness coating (0.4-1.0μm), thick coating and ultra-thick coating (≥1.0μm) and other products of different thicknesses can be controlled. The coating process requires that the coating equipment is divided into two-roller coating, two-roller scoring coating, three-roller double-sided coating and other control methods, and finally obtain coating products that meet the requirements.

[0005] Under the premise that non-oriented electrical steel meets many performance indicators (processing, adhesion, corrosion resistance, heat resistance, etc.), the main required characteristic is interlayer resistance, which is usually 2 to 50Ω·cm 2 / sheet. As users' requirements for interlayer resistance increase, it is necessary to develop non-oriented electrical steel with high interlayer resistance. The existing technology mainly increases the interlayer resistance by increasing the coating thickness, but the increase in coating thickness not only increases the production cost, but also affects the electromagnetic properties of the product. Generally speaking, the iron loss will gradually increase with the increase of coating thickness. Summary of the invention

[0006] In order to solve the problems of the prior art, the present invention provides a method for improving the performance of insulating coating on the surface of non-oriented silicon steel. Under the conventional non-oriented silicon steel production tooling conditions, the present invention uses the existing multifunctional continuous annealing unit to control the steel strip substrate in the cooling section after the finished product heat treatment to form an oxide film, which matches the subsequent coating process, and produces a "composite coating" with high inter-layer resistance characteristics without increasing the coating thickness to affect other properties of the original coating, so as to achieve the purpose of low-cost and high-efficiency production of non-oriented full-process coating products.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A method for improving the performance of insulating coating on the surface of non-oriented silicon steel, wherein the steel strip is subjected to continuous annealing, and in a circulating jet cooling section (RJC nitrogen jet cooling section, RJC section) of the continuous annealing, an oxide film is formed on the surface of the steel strip substrate by inputting air or humidified nitrogen, wherein the thickness of the oxide film is 0.05 to 3.0 μm, thereby improving the insulation resistance characteristics of the non-oriented silicon steel; and the adhesion of the oxide film can also be controlled in combination with different coatings to prevent the coating from peeling off during application.

[0009] Furthermore, in the circulating jet cooling section, the steel strip running speed is 60-180 m / min, the inlet steel strip temperature is 760°C-950°C, the cooling rate is 10-100°C / s, the outlet steel strip temperature is 80-120°C, and the oxygen content is controlled to be 100ppm-5000ppm by inputting air or humidified nitrogen and adjusting the input amount according to the RJC section's own oxygen content tester.

[0010] The temperature of the steel strip at the entrance of the RJC section is controlled at 760℃~950℃, which is also the temperature at the end of the soaking section of conventional non-oriented silicon steel. This can ensure the surface oxidation reaction activity entering the RJC section and quickly form an oxide film. If the temperature is higher than 950℃ entering the RJC section, it is easy to cause excessive cooling rate and generate internal stress, affecting the plate shape and electromagnetic properties. 760℃ is the hydrogen safety point in the hydrogen-nitrogen mixed protective atmosphere of conventional non-oriented silicon steel.

[0011] The oxygen content is controlled to be 100ppm to 5000ppm: combined with the running speed of the steel strip, it is based on controlling the micro-oxide layer to a thick oxide layer on the surface of the steel strip.

[0012] The running speed of the steel strip is 60-180m / min: it is based on the process speed of continuous annealing of non-oriented silicon steel products. The cooling speed of the steel strip in the RJC section is 10-100℃ / s, which gives the surface of the steel strip sufficient oxidation reaction to form the required oxide film thickness.

[0013] Furthermore, in the circulating jet cooling section, an air input device or a nitrogen humidification device is added to control the oxygen content by inputting air or humidified nitrogen.

[0014] Furthermore, the content of Si in the non-oriented silicon steel is 0.3-3.0 wt%, and Al S The content is 0.15-0.9wt%, including high-grade to low-grade series products.

[0015] Furthermore, the steel strip is a cold-rolled steel strip.

[0016] Furthermore, the thickness of the cold-rolled steel strip is 0.35-0.50 mm.

[0017] Furthermore, the coating has a thickness of 0.35-1.15 μm.

[0018] The invention is applicable to a conventional multifunctional continuous annealing professional production line for cold-rolled non-oriented silicon steel, and can produce cold-rolled non-oriented silicon steel products with high inter-layer resistance at low cost.

[0019] Beneficial effects of the present invention:

[0020] (1) The present invention can be normally produced in the existing non-oriented silicon steel production line, and only needs to add a gas device or a gas humidifying device, with a small investment;

[0021] (2) The present invention can be combined with the existing series product production process (process speed) to obtain relatively fixed coating characteristics under a fixed process by adjusting the temperature, oxygen content, and oxide film thickness parameters to meet the needs of different users;

[0022] (3) The composite coating product of the present invention can increase the interlayer resistance by 140 to 1000 Ω·cm compared with conventional processes without increasing the coating thickness and affecting the existing coating varieties and coating processes. 2 / piece; when the Si content is greater than 2.0%, a SiO2·Fe2O3 oxide film will be formed on the surface of the steel strip substrate, and the interlayer resistance of the composite coating product of the present invention is ≥1000Ω·cm 2 / piece;

[0023] (4) The composite coating control technology of the present invention not only improves the interlayer resistance, but also retains or improves other performance indicators of the original coating, such as adhesion, stacking, corrosion resistance, processability (lubricity of punching sheets), etc.;

[0024] (5) The composite coating control technology of the present invention applies the coating liquid on the basis of the oxide film of the substrate, which increases the contact friction with the coating roller and enhances the adhesion of the coating liquid, thereby reducing coating leakage and quality loss;

[0025] (5) The present invention has fully taken into account the safe operation of hydrogen and can ensure the production safety under the original process conditions. DETAILED DESCRIPTION

[0026] The following non-limiting embodiments may enable a person skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0027] Example 1. Test of low grade typical product 50W1300

[0028] The steel strip runs at a speed of 150 m / min, the RJC section inlet temperature is 780°C, the RJC section outlet temperature is 90°C, humidified nitrogen is used, the cooling rate is 50°C / s, the oxygen content in the middle section of the RJC is controlled at 350 PPM, an oxide film is formed on the surface of the steel strip, and the oxide film thickness is controlled to be 0.17 μm; the same conventional production of T4 semi-organic coating solution, conventional thin coating coating process control, coating thickness of 0.35 μm, the implementation product is obtained.

[0029] Compared with the products produced by conventional coating (the oxygen content was not controlled by humidified nitrogen in the RJC section, the oxygen content was less than 100PPm, and the other processes were the same as the preparation of the implemented products), the surface color and luster of the implemented products were similar, but more uniform; there was no defect of thin coating leakage; the interlayer resistance was increased from 210 to 350Ω·cm 2 / piece; Adhesion A; Except for interlayer resistance, other performance indicators are similar or consistent with those of conventional coating products.

[0030] Example 2. Test of low grade typical product 50W1300

[0031] The steel strip runs at a speed of 180 m / min, the RJC section inlet temperature is 810°C, the RJC section outlet temperature is 100°C, humidified nitrogen is used, the cooling rate is 65°C / s, the oxygen content in the middle section of the RJC is controlled to 700 PPM, an oxide film is formed on the surface of the steel strip, and the oxide film thickness is controlled to 0.32 μm; the same conventional production T4 semi-organic coating solution and conventional coating coating process control are used, the coating thickness is 0.85 μm, and the implemented product is obtained.

[0032] Compared with the products produced by conventional coating (the oxygen content was not controlled by humidified nitrogen in the RJC section, the oxygen content was less than 100PPm, and the other processes were the same as the preparation of the implemented products), the surface color of the implemented products was light brown and uniform, and the interlayer resistance was increased from 320 to 650Ω·cm 2 / piece; Adhesion A; Except for interlayer resistance, other performance indicators are similar or consistent with those of conventional coating products.

[0033] Example 3. Test of typical product 50W600 of medium grade

[0034] The running speed of the steel strip is 135m / min, the inlet temperature of the RJC section is 850℃, the outlet temperature of the RJC section is 95℃, the air is input, the cooling rate is 45℃ / s, the oxygen content in the middle section of the RJC is controlled to 450PPm, and an oxide film is formed on the surface of the steel strip with a thickness of 0.20μm; the same conventional production of T4 semi-organic coating solution and conventional thin coating coating process control are used, the coating thickness is 0.40μm, and the implemented product is obtained.

[0035] Compared with the products produced by conventional coating (the oxygen content is not controlled by input air in the RJC section, the oxygen content is less than 100PPm, and the other processes are the same as the preparation of the implemented products), the surface color and luster of the implemented products are similar, but more uniform; no coating defects occur; the interlayer resistance is increased from 280 to 450Ω·cm 2 / piece; Adhesion A; Except for interlayer resistance, other performance indicators are similar or consistent with those of conventional coating products.

[0036] Example 4. Test of typical product 50W600 of medium grade

[0037] The steel strip runs at a speed of 150 m / min, the RJC section inlet temperature is 840°C, the RJC section outlet temperature is 90°C, air is input, and the cooling rate is 55°C / s, ensuring that the oxygen content in the middle section of the RJC is controlled at 600 PPM, and an oxide film is formed on the surface of the steel strip, and the oxide film thickness is controlled to be 0.38 μm; the same conventional production T4 semi-organic coating solution and conventional coating coating process control are used, the coating thickness is 0.65 μm, and the implemented product is obtained.

[0038] Compared with the products produced by conventional coating (the oxygen content in the RJC section is not controlled by input air, the oxygen content is less than 100PPm, and the other processes are the same as the preparation of the implemented product), the surface color of the implemented product is light brown and uniform, and the interlayer resistance is increased from 320 to 580Ω·cm 2 / piece; Adhesion A; Except for interlayer resistance, other performance indicators are similar or consistent with those of conventional coating products.

[0039] Example 5. Test of high grade typical product 50W310

[0040] The running speed of the steel strip is 100m / min, the inlet temperature of the RJC section is 900℃, the outlet temperature of the RJC section is 105℃, humidified nitrogen, the cooling rate is 38℃ / s, the oxygen content in the middle section of the RJC is controlled to 500PPm, and an oxide film is formed on the surface of the steel strip with a thickness of 0.25μm; the same conventional production of T4 semi-organic coating solution and conventional thin coating process control are used, the coating thickness is 0.70μm, and the implemented product is obtained.

[0041] Compared with conventional products produced by conventional coating (the oxygen content was not controlled by humidified nitrogen in the RJC section, the oxygen content was less than 100PPm, and the other processes were the same as the preparation of the implemented product), the surface color of the implemented product was light brown and uniform; the interlayer resistance was increased from 300 to 480Ω·cm 2 / piece; Adhesion A; Except for interlayer resistance, other performance indicators are similar or consistent with those of conventional coating products.

[0042] Example 6. Test of typical high-grade new energy silicon steel product 35ADG1800

[0043] The running speed of the steel strip is 120m / min, the inlet temperature of the RJC section is 840℃, the outlet temperature of the RJC section is 85℃, humidified nitrogen, the cooling rate is 45℃ / s, the oxygen content in the middle section of the RJC is controlled to be 1100PPm, an oxide film is formed on the surface of the steel strip, the thickness of the oxide film is controlled to be 0.80μm, and a SiO2·Fe2O3 oxide base film will be formed on the surface of the steel strip substrate; the same conventional production T4 semi-organic coating solution and conventional coating coating process control are used, the coating thickness is 1.15μm, and the implemented product is obtained.

[0044] Compared with the products produced by conventional coating (the oxygen content was not controlled by humidified nitrogen in the RJC section, the oxygen content was less than 100PPm, and the other processes were the same as the preparation of the implemented products), the surface color of the implemented products was dark brown and uniform, and the interlayer resistance was increased from 480 to 1260Ω·cm 2 / piece; Adhesion A; Except for interlayer resistance, other performance indicators are similar or consistent with those of conventional coating products.

Claims

1. A method for improving the performance of insulating coating on the surface of non-oriented silicon steel, characterized in that: The steel strip is subjected to continuous annealing. In the circulating jet cooling section of the continuous annealing, an oxide film is formed on the surface of the steel strip by inputting air or humidified nitrogen. The thickness of the oxide film is 0.05 to 3.0 μm.

2. The method according to claim 1, characterized in that In the circulating jet cooling section, the steel strip running speed is 60-180 m / min, the inlet steel strip temperature is 760°C-950°C, the cooling rate is 10-100°C / s, the outlet steel strip temperature is 80-120°C, and the oxygen content is controlled to be 100ppm-5000ppm by inputting air or humidified nitrogen.

3. The method according to claim 2, characterized in that In the circulating jet cooling section, additional equipment for inputting air or a device for humidifying nitrogen is provided.

4. The method according to claim 1, characterized in that: The content of Si in non-oriented silicon steel is 0.3-3.0wt%, Al S The content is 0.15~0.9wt%.

5. The method according to claim 1, characterized in that The steel strip is a cold-rolled steel strip.

6. The method according to claim 5, characterized in that The thickness of the cold-rolled steel strip is 0.35-0.50 mm.

7. The method according to claim 1, characterized in that The thickness of the coating is 0.35-1.15 μm.