Production method for improving surface coating quality of middle-low grade non-oriented silicon steel

Abstract

The invention provides a production method for improving the surface coating quality of medium-low-grade non-oriented silicon steel, and relates to the technical field of steel production. Comprising the steps of surface alkali washing, CA annealing line annealing treatment, surface cleaning, strip steel lower surface infiltration, strip steel upper surface coating liquid bubble removal, double-roller coating, coating drying and sintering and finishing packaging. Strip steel is infiltrated in advance, the depth of a notch groove of a lower roller is increased so as to increase the thickness of a coating on the lower surface and improve resistance, bubbles in the coating liquid are discharged by increasing the liquid level of a liquid collecting funnel, adding a filter screen on the upper surface and closing a circulating pipeline of the coating liquid, the bubbles in the coating liquid are prevented from being pressed into the coating, and the problem of white points of the coating is solved. Meanwhile, the thickness of the lower surface is increased, the thickness consistency of coatings on the upper surface and the lower surface is improved, and the adhesiveness of the coatings is improved, so that the surface coating quality of a produced product is good, the surface color of strip steel is uniform and free of color difference, roller marks and white points, the adhesiveness is good, and application requirements can be better met.

Description

Technical Field

[0001] The present application relates to the technical field of steel production, and in particular to a production method for improving the quality of surface coatings on medium and low grade non-oriented silicon steels. Background Art

[0002] Cold-rolled non-oriented silicon steel is an important energy-saving metal functional material with the largest consumption among soft magnetic materials. It is widely used in the iron cores of electric motors, generators, small transformers and other motors. It is an important soft magnetic alloy that is indispensable in the power, electronics and military industries. When manufacturing the iron core, silicon steel sheets need to be stacked together layer by layer. In order to limit the eddy current within each stack and effectively reduce the eddy current loss of the iron core, it is often necessary to apply an insulating coating on the surface of the silicon steel to generate high impedance.

[0003] But the surface insulation coating cannot be too thick, because too thick will affect the lamination factor of non-oriented silicon steel on the one hand, and reduce the magnetic properties of the steel sheet on the other hand. However, if the coating is too thin, the insulation of the coating will be reduced, and since the non-oriented silicon steel sheet needs to be stress-relieved annealed at 700-800℃ during application, the insulation performance will be lower after annealing.

[0004] At present, the types of non-oriented silicon steel insulation coatings are mainly divided into three categories: organic coatings, inorganic coatings and semi-organic coatings. Among them, the chromium-containing coating in the semi-organic coating of non-oriented silicon steel is the mainstream of the market, and more than 85% of the market is chromium-containing coatings. The surface coating requirements of non-oriented silicon steel are very high. The main points are as follows: good insulation, good heat resistance, thin and uniform insulation film, high interlayer resistance, good adhesion, good punching performance, good corrosion resistance, good weldability, non-toxicity, etc., which have high requirements for the coating unit.

[0005] The coating unit for domestic medium and low grade non-oriented silicon steel coating is generally a double-roller mode. The double-roller coating unit has the advantages of simple structure, easy operation and low production cost. However, due to the large pressure difference between the upper and lower rollers, a large number of bubbles are mixed in the coating liquid circulation process, and the groove depth of the groove roller is not selected reasonably, resulting in defects such as roller marks and white spots on the strip surface. The difference between the upper and lower resistance values ​​of the surface insulation resistance is too large (thick on the top and thin on the bottom), and the coating liquid production consumption is large. As a result, the finished product is largely reclassified as a second-class product due to surface coating quality problems.

[0006] In view of this, the present application aims to provide a production method for improving the quality of surface coating of medium and low grade non-oriented silicon steel, so as to better solve the above technical problems. Summary of the invention

[0007] The purpose of the embodiments of the present application is to provide a production method for improving the quality of surface coating of medium and low grade non-oriented silicon steel, which can solve the technical problems of no color difference on the surface of silicon steel strip, elimination of white spots on the coating and good adhesion.

[0008] The present application provides a production method for improving the quality of surface coating of medium and low grade non-oriented silicon steel, comprising the following steps:

[0009] Surface alkali washing, CA annealing line annealing treatment, surface cleaning, strip lower surface infiltration, strip upper surface coating liquid bubble removal, double roller coating, coating drying and sintering, finishing and packaging.

[0010] Furthermore, in the step of removing bubbles from the coating liquid on the strip surface:

[0011] The coating liquid is sprayed with a coating liquid base pipe, and the coating liquid manifold is not sprayed directly on the strip surface. A 10-100 mesh stainless steel filter is set under the manifold to reduce the flow rate of the coating liquid through the filter, so that the bubbles in the coating liquid have sufficient floating time and overflow, so that the coating liquid is evenly coated on the upper surface of the strip by the coating roller, avoiding the formation of white spots on the strip surface.

[0012] Furthermore, the coating liquid after double-roll coating is recovered through a collecting funnel, and a U-shaped pipeline is set at the outlet of the collecting funnel to raise the liquid level in the collecting funnel by 40-60 cm, so that the bubbles mixed in the coating liquid have enough floating time, thereby reducing the amount of bubbles in the recovered coating liquid.

[0013] Furthermore, the connection between the outlet of the coating liquid collecting funnel after double-roller coating and the circulation pipeline is set as a sealed connection to prevent the recovered coating liquid from being mixed with bubbles again.

[0014] Furthermore, in the double-roll coating step:

[0015] The coating is carried out using a coating unit, wherein the groove depth of the upper roller of the coating unit is set to 0.05-0.08 mm, and the groove depth of the lower roller is set to 0.1-0.12 mm, so as to increase the amount of liquid carried by the lower roller, thicken the lower surface coating, and thus increase the resistance.

[0016] Furthermore, in the double-roll coating step:

[0017] The coating thickness formed by coating is controlled to be 0.8-1.2 μm, the coating surface insulation resistance is ≥100Ω·mm 2, and the insulation resistance difference between the upper and lower surface coatings of the strip is less than 30%.

[0018] Beneficial effects of the present invention:

[0019] The production method for improving the surface coating quality of medium and low grade non-oriented silicon steel provided by the present invention comprises the steps of: surface alkali washing, CA annealing line annealing treatment, surface cleaning, strip lower surface infiltration, strip upper surface coating liquid bubble removal, double-roller coating, coating drying and sintering, and finishing packaging; the lower surface of the strip is infiltrated in advance, the groove depth of the lower roller of the coating unit is increased to increase the thickness of the lower surface coating and improve the resistance; the liquid level of the liquid collecting funnel is increased, a filter screen is added to the upper surface, and a circulation pipeline of the coating liquid is closed to discharge bubbles in the coating liquid and avoid bubbles in the coating liquid being pressed into the coating, thereby solving the problem of white spots on the coating; at the same time, the thickness of the lower surface is increased to improve the consistency of the thickness of the upper and lower surfaces, and the adhesion of the coating is improved, so that the surface coating quality of the produced product is good; after stress relief annealing at 750°C, the surface color of the strip is uniform without color difference, roller mark, and white spots, and the adhesion is good, which can better meet application requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is a production process flow chart in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively by way of examples, and preferred embodiments of the present invention are given below. However, the present invention can be implemented in a variety of different forms and is not limited to the embodiments described herein. Any other implementation schemes obtained by modifying or equivalently replacing the technical scheme of the present invention without creative results are within the protection scope of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0024] The numerical values ​​disclosed in the embodiments of the present invention are approximate values, not definite values. When the error or experimental conditions permit, all values ​​within the error range may be included without being limited to the specific numerical values ​​disclosed in the embodiments of the present invention.

[0025] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0026] Example

[0027] This embodiment provides a production method for improving the quality of surface coating of medium and low grade non-oriented silicon steel, comprising the following steps:

[0028] Surface alkali washing, CA annealing line annealing treatment, surface cleaning, strip lower surface infiltration, strip upper surface coating liquid bubble removal, double roller coating, coating drying and sintering, finishing and packaging.

[0029] Specifically, in this embodiment:

[0030] During the double-roll coating process, a set of headers is added 30 cm in front of the lower roller of the coating unit. The headers have two rows of small holes with a hole spacing of 13 mm and a hole diameter of 5 mm. The header pressure is 0.1 MPa.

[0031] Two layers of 20-mesh stainless steel filter screens are set on the upper surface coating liquid manifold.

[0032] A U-shaped pipe is set at the outlet of the coating liquid collection funnel after coating to raise the liquid level in the collection funnel by 45 cm;

[0033] The outlet of the coating liquid collecting funnel and the circulation pipeline are changed from the open type in the prior art to a sealed connection.

[0034] The groove depth used on the upper roller of the coating unit is 0.05mm, and the groove depth used on the lower roller is 0.11mm.

[0035] The conventional production methods in this embodiment and the prior art were used to carry out batch production, and the surface coating quality of different batches of strip steel produced in batch production was tested. The test results are shown in the following table:

[0036]

[0037] Referring to the above table, it can be seen that the production method of the surface coating quality of medium and low grade non-oriented silicon steel provided by the present application includes the steps of: surface alkali washing, CA annealing line annealing treatment, surface cleaning, infiltration of the lower surface of the strip, removal of bubbles in the coating liquid on the upper surface of the strip, double-roll coating, coating drying and sintering, and finishing packaging; it infiltrates the lower surface of the strip in advance, increases the groove depth of the lower roller of the coating unit to increase the thickness of the coating on the lower surface, and improves the resistance, and increases the liquid level of the liquid collecting funnel, adds a filter screen on the upper surface, and closes the circulation pipeline of the coating liquid to discharge the bubbles in the coating liquid, so as to prevent the bubbles in the coating liquid from being pressed into the coating, thereby solving the problem of white spots on the coating. At the same time, by increasing the thickness of the lower surface, the consistency of the coating thickness on the upper and lower surfaces is improved, and the adhesion of the coating is improved, so that the surface coating quality of the produced product is good. After stress relief annealing at 750°C, the surface color of the strip is uniform without color difference, roller marks, and white spots, and the adhesion is good, which reduces the consumption of coating liquid, thereby reducing the production cost, and can better meet the application requirements.

[0038] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A production method for improving the quality of surface coating of medium and low grade non-oriented silicon steel, characterized in that: The following steps are involved: Surface alkali washing, CA annealing line annealing treatment, surface cleaning, strip lower surface infiltration, strip upper surface coating liquid bubble removal, double roller coating, coating drying and sintering, finishing and packaging.

2. The production method for improving the surface coating quality of medium and low grade non-oriented silicon steel according to claim 1, characterized in that: In the step of removing bubbles from the coating liquid on the strip surface: The coating liquid is sprayed with a coating liquid base pipe, and the coating liquid manifold is not sprayed directly on the strip surface. A 10-100 mesh stainless steel filter is set under the manifold to reduce the flow rate of the coating liquid through the filter, so that the bubbles in the coating liquid have sufficient floating time and overflow, so that the coating liquid is evenly coated on the upper surface of the strip by the coating roller, avoiding the formation of white spots on the strip surface.

3. The production method for improving the surface coating quality of medium and low grade non-oriented silicon steel according to claim 1, characterized in that: The coating liquid after double-roll coating is recovered through a collecting funnel. A U-shaped pipeline is set at the outlet of the collecting funnel to raise the liquid level in the collecting funnel by 40-60cm, so that the bubbles mixed in the coating liquid have enough floating time to reduce the amount of bubbles in the recovered coating liquid.

4. The production method for improving the surface coating quality of medium and low grade non-oriented silicon steel according to claim 3, characterized in that: The connection between the outlet of the coating liquid collecting funnel after double-roller coating and the circulation pipeline is set as a sealed connection to prevent the recovered coating liquid from being mixed with bubbles again.

5. The production method for improving the surface coating quality of medium and low grade non-oriented silicon steel according to claim 1, characterized in that: In the double-roll coating step: The coating is carried out using a coating unit, wherein the groove depth of the upper roller of the coating unit is set to 0.05-0.08 mm, and the groove depth of the lower roller is set to 0.1-0.12 mm, so as to increase the amount of liquid carried by the lower roller, thicken the lower surface coating, and thus increase the resistance.

6. The production method for improving the surface coating quality of medium and low grade non-oriented silicon steel according to claim 1, characterized in that: In the double-roll coating step: The coating thickness formed by coating is controlled to be 0.8-1.2 μm, the coating surface insulation resistance is ≥100 Ω·mm 2, and the insulation resistance difference between the upper and lower surface coatings of the strip is less than 30%.

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