A production method for improving the surface and edge quality of silicon steel

Abstract

The present invention relates to a production method for improving the surface and edge quality of silicon steel, comprising: 1) preparing a protective coating; the protective coating is composed of material A and material B, material A is plastic particles, and material B is continuous casting crystallizer protective slag; 2) spraying the protective coating evenly onto the surface of the silicon steel slab before loading the furnace; 3) heating the silicon steel slab in the furnace; 4) descaling the silicon steel slab with high-pressure water after it is taken out of the furnace. The present invention sprays the protective coating before heating the silicon steel slab, heats the slab under a corresponding heating system, reduces burn loss and heating quality defects, and can especially improve the surface and corner decarburization problems of high-silicon products, improve the subsequent processing capacity of the steel plate, reduce edge cutting, and reduce the occurrence of broken belt accidents, thereby producing high-quality and high-yield cold-rolled non-oriented silicon steel products.

Description

Technical Field

[0001] The invention relates to the technical field of cold-rolled non-oriented silicon steel production, and in particular to a production method for improving the surface and edge quality of silicon steel. Background Art

[0002] Cold-rolled non-oriented silicon steel is an important functional metal material, widely used in the manufacture of iron cores of various motors. With the intensified competition among electrical steel manufacturers, how to improve product quality and reduce production costs has become the goal pursued by manufacturers.

[0003] The production process of cold-rolled silicon steel is long, and the quality defects of the products are caused by or accompanied by various process intersections. In the production process of hot-rolled raw materials, surface quality and edge quality defects are common. Surface quality defects include residual iron oxide scale, which causes the steel plate to be under-pickled after normal pickling; especially for high-grade high-silicon and high-aluminum steels, the hot rolling heating process will produce iron oxide scale containing silicon-iron olivine components, which is highly adhesive, difficult to descale, and difficult to remove by subsequent shot peening and pickling. During the hot rolling heating, the surface and edges of the steel plate are prone to decarburization and edge cracking, and surface decarburization will further promote the pressing and adhesion of the iron scale. In addition, in the production of high-silicon, high-aluminum, high-grade cold-rolled silicon steel, due to the presence of "super-large" grains in the solidification structure of the slab, oxidation and decarburization are easily generated at the grain boundary during the heating process, resulting in the aggravation of the "brittle fracture" phenomenon in the subsequent cold rolling production, which is extremely unfavorable to the control of product quality and yield indicators.

[0004] In the hot-rolled production of silicon steel, the use of "low temperature and long time" heating is the mainstream process to improve the electromagnetic properties of the product. However, in steel joint ventures, the production scale of silicon steel varieties determines that it is impossible to form a "professional production line". In the production process of many varieties on the same line, even if the "furnace head steel and furnace tail steel" are heated in the transition material position, the quality of low-temperature heating cannot be guaranteed; high-grade silicon steel slabs are still difficult to avoid decarburization due to the easily oxidizable characteristics of silicon-aluminum alloy elements.

[0005] In terms of related heating control, it is more common to apply special high-temperature coatings to the oriented silicon steel slabs during high-temperature heating to reduce the burning rate. However, the high-temperature heating method has been gradually eliminated.

[0006] The Chinese invention patent with application number CN202210247339.6 discloses "a method for improving the wedge-shaped accuracy of short-process hot-rolled non-oriented silicon steel". By controlling the process such as the temperature during slab heating and the slab travel speed in different zones, the occurrence of wedge-shaped out-of-tolerance defects of non-oriented silicon steel can be effectively reduced.

[0007] The Chinese invention patent with application number CN201910398225.X discloses "a production method for reducing the narrowness of the head of non-oriented silicon steel". By controlling the slab furnace temperature, the accident rate caused by the narrowness of the head is reduced and the occurrence of scrap is reduced.

[0008] The Chinese invention patent with application number CN202011059345.6 discloses a "control method and control device for low-temperature heating of non-oriented silicon steel slabs", which achieves the purpose of reducing the slab heating temperature, heating time and improving the temperature uniformity of the slab by improving the heating system.

[0009] The Chinese invention patent with application number CN202311403107.6 discloses a "high-grade non-oriented silicon steel with excellent surface quality and its preparation method". Through improvements in component ratio and process, the high-grade non-oriented silicon steel with excellent surface quality is achieved.

[0010] Compared with the above-mentioned patent documents disclosed, the present invention sprays a protective coating before heating the silicon steel slab, heats the slab under a corresponding heating process, and reduces burning and heating quality defects. Summary of the invention

[0011] The present invention provides a production method for improving the surface and edge quality of silicon steel. A protective coating is sprayed before heating the silicon steel slab, and the slab is heated under a corresponding heating system to reduce burning and heating quality defects. In particular, the surface and edge decarburization problems of high-silicon products can be improved, the subsequent processing capacity of the steel plate can be improved, the edge cutting can be reduced, and the occurrence of strip breakage accidents can be reduced, thereby producing high-quality and high-yield cold-rolled non-oriented silicon steel products.

[0012] In order to achieve the above object, the present invention adopts the following technical solutions:

[0013] A production method for improving the surface and edge quality of silicon steel comprises the following steps:

[0014] 1) Preparing a protective coating; the protective coating is composed of material A and material B, and by volume percentage, material A: 1% to 15%, material B: 85% to 99%; the material A is plastic particles, the particle size of the plastic particles is 0.05 to 1.2 mm, and the particle size distribution is that the particle size of 0.1 to 0.7 mm accounts for more than 95%; the melting point of the plastic particles is 60 to 250° C.; the material B is continuous casting crystallizer protection slag, the hemispherical point temperature of the continuous casting crystallizer protection slag is 930 to 1180° C., and the viscosity at 1300° C. is 0.05 to 0.15 Pa.s;

[0015] 2) Silicon steel slabs are hot transported and hot charged into the furnace, with the charging temperature ≥350°C; before charging into the furnace, the protective coating is evenly sprayed onto the surface of the slab, with a coating thickness of 2 to 10 mm;

[0016] 3) Put the silicon steel slab coated with protective coating into the furnace for heating, control the temperature of the heating section to 1200-1300℃, and control the air-fuel ratio to 0.90-0.98; after heating, the plastic particles melt and burn, and the continuous casting crystallizer protection slag and the original iron sheet on the surface of the silicon steel slab form a molten thin sticky film that adheres to the surface of the slab to prevent oxidation and decarburization of the slab surface;

[0017] 4) After the silicon steel slab is taken out of the furnace, high-pressure water is used to descale it. During this process, the molten slag layer formed by the molten thin mucous film meets water to form crystalline and non-crystalline slag shells and is peeled off. The descaled silicon steel slab enters the hot rolling process.

[0018] Furthermore, the plastic particles are polyethylene particles or polypropylene particles.

[0019] Furthermore, the continuous casting mold protection slag is continuous casting mold protection slag for silicon steel slab production, or continuous casting mold protection slag for ultra-low carbon steel production.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1) Spray protective coating before heating silicon steel slabs, heat the slabs under the corresponding heating system to reduce burning and heating quality defects, especially to improve the surface and corner decarburization problems of high-silicon products, improve the subsequent processing capacity of steel plates, reduce edge cutting and reduce the occurrence of broken strip accidents, and thus produce high-quality and high-yield cold-rolled non-oriented silicon steel products.

[0022] 2) The raw materials of protective coatings are easy to obtain, low in cost, simple in preparation and use, and have significant effects. They can effectively improve the heating quality of slabs, avoid defect transfer and conduction, directly improve the rolling surface quality and edge quality, and effectively control the edge cracking and broken belt rate of high-silicon products. DETAILED DESCRIPTION

[0023] The production method for improving the surface and edge quality of silicon steel described in the present invention mainly improves the heating process of silicon steel slab before hot rolling. The key points of improvement are as follows:

[0024] Prepare protective coating; the protective coating is composed of material A and material B.

[0025] 1. Material A is plastic microparticles, with a particle size requirement of 0.05-1.2 mm, of which 0.1-0.7 mm particle size accounts for more than 95%. The melting point of plastic microparticles is 60-250°C. For environmental protection reasons, the best material is polyethylene microparticles or polypropylene microparticles.

[0026] Material B is continuous casting mold protection slag, which can be continuous casting mold protection slag used in ultra-low carbon steel continuous casting production, or continuous casting mold protection slag used in silicon steel slab continuous casting production. The hemisphere point temperature of continuous casting mold protection slag is 930-1180℃, and the viscosity at 1300℃ is 0.05-0.15Pa.s.

[0027] Before spraying, mix material A and material B according to the ratio: material A 1%~15%, material B 85%~99%. The ratio can be selected according to the spraying method.

[0028] 2. Silicon steel slabs are hot transported and hot charged into the furnace. The charging temperature is ≥350℃. Before charging, the protective coating is evenly sprayed on the surface of each part of the silicon steel slab (the two ends of the silicon steel slab do not need to be sprayed). The coating thickness (effective adhesion thickness) is controlled at 2-10mm. After entering the furnace, at the heating temperature, the plastic particles melt and adhere the continuous casting crystallizer protection slag to the surface of the silicon steel slab to form a protective layer.

[0029] 3. After the silicon steel slabs are coated with protective coatings, they are heated in the furnace. The furnace gas temperature in the heating section is controlled at 1200℃~1300℃, and the furnace gas air-fuel ratio is controlled within the range of 0.90~0.98. The furnace time and furnace temperature control of the silicon steel slabs are the same as the heating system of conventional silicon steel products of the same grade. At the corresponding furnace gas temperature, the plastic particles melt and burn, and the continuous casting crystallizer protection slag and the original iron sheet on the surface of the silicon steel slab form a molten thin sticky film that adheres to the surface of the slab to prevent oxidation and decarburization of the slab surface.

[0030] 4. After leaving the furnace, high-pressure water descaling and rolling are the same as the conventional production process of the same grade of silicon steel. During high-pressure water descaling, the molten slag layer on each surface of the silicon steel slab meets water to form crystalline and amorphous slag shells, which collapse and peel off quickly.

[0031] In order to more intuitively embody the present invention, the embodiments of the present invention are further described in conjunction with examples. The following examples are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any technical solution that can be obviously obtained by a person skilled in the art within the technical scope disclosed in the present invention, including simple changes or equivalent replacements, is within the protection scope of the present invention.

[0032] [Example 1]

[0033] In this embodiment, the production of typical non-oriented low-grade silicon steel (Si content 0.57%) is taken as an example.

[0034] Prepare protective coating. Material A, i.e., plastic microparticles, has a particle size of 0.05 to 1.2 mm, and a particle size distribution of 97% of particles having a particle size of 0.1 to 0.7 mm; the melting point of the plastic microparticles is 120°C; material B uses the continuous casting crystallizer protective slag used in the continuous casting of silicon steel slabs in this embodiment, with a hemisphere point temperature of 965°C and a viscosity (1300°C) of 0.07 Pa.s; material A and material B are mixed before spraying, with a ratio of 5% material A and 95% material B.

[0035] Silicon steel slabs are hot-transported and hot-charged in the furnace, and the charging temperature is 450℃. Before charging, the protective coating mixed according to the ratio is sprayed evenly on the surfaces of the silicon steel slabs (the two ends of the slabs are not sprayed). The coating adheres to the surface of the slabs, and the coating thickness is controlled at 4mm. The silicon steel slabs after coating are heated in the furnace, and the furnace gas temperature in the heating section is controlled at 1240℃, the furnace gas air-fuel ratio is controlled at 0.96, the overall furnace time is 195min, and the furnace temperature is 1140℃. The silicon steel slabs after being discharged from the furnace are descaled by high-pressure water, and the slag shell and the original associated cast iron scale are all detached. The descaled silicon steel slabs enter the next hot rolling process.

[0036] The residual iron scale rate on the surface of the silicon steel produced in this embodiment decreased from 9.8% before implementation to 1.9%, and the edge crack rate decreased from 17.5% before implementation to 5.6%.

[0037] [Example 2]

[0038] In this embodiment, the production of typical non-oriented medium grade silicon steel (Si content 1.27%) is taken as an example.

[0039] Prepare protective coating. Material A, i.e., plastic microparticles, has a particle size of 0.05 to 1.2 mm, and a particle size distribution of 96% of particles having a particle size of 0.1 to 0.7 mm; the melting point of the plastic microparticles is 125°C; material B uses the continuous casting crystallizer protective slag used in the continuous casting of silicon steel slabs in this embodiment, with a hemisphere point temperature of 985°C and a viscosity (1300°C) of 0.09 Pa.s; material A and material B are mixed before spraying, with a ratio of 7% material A and 93% material B.

[0040] Silicon steel slabs are hot-delivered and hot-charged in the furnace, with a charging temperature of 430°C. Before charging, the protective coating mixed according to the ratio is sprayed evenly on the surfaces of the silicon steel slabs (the two ends of the slabs are not sprayed). The coating adheres to the surface of the slabs, and the coating thickness is controlled at 3mm. The silicon steel slabs after coating are heated in the furnace, and the furnace gas temperature in the heating section is controlled at 1250°C, the furnace gas air-fuel ratio is controlled at 0.97, the overall furnace time is 205min, and the furnace temperature is 1135°C. After the silicon steel slabs are discharged from the furnace, they are descaled by high-pressure water, and the slag shell and the original associated cast iron scale are all detached. The descaled silicon steel slabs enter the next hot rolling process.

[0041] The residual iron scale rate on the surface of the silicon steel produced in this embodiment decreased from 10.2% before implementation to 2.3%, and the edge crack rate decreased from 18.1% before implementation to 4.8%.

[0042] [Example 3]

[0043] In this embodiment, the production of typical non-oriented high-grade silicon steel (Si content 3.27%) is taken as an example.

[0044] Prepare protective coating. Material A, i.e., plastic microparticles, has a particle size of 0.05 to 1.2 mm, and a particle size distribution of 95% of particles having a particle size of 0.1 to 0.7 mm; the melting point of the plastic microparticles is 215°C; material B uses the continuous casting crystallizer protective slag used in the continuous casting of silicon steel slabs in this embodiment, with a hemisphere point temperature of 955°C and a viscosity (1300°C) of 0.06 Pa.s; material A and material B are mixed before spraying, with a ratio of 8% material A and 92% material B.

[0045] Silicon steel slabs are hot-delivered and hot-charged in the furnace, with a charging temperature of 430°C. Before charging, the protective coating mixed according to the ratio is sprayed evenly on all surfaces of the silicon steel slabs (the two ends of the slabs are not sprayed). The coating adheres to the surface of the slabs, and the coating thickness is controlled at 5mm. The silicon steel slabs after coating are heated in the furnace, and the furnace gas temperature in the heating section is controlled at 1260°C, the furnace gas air-fuel ratio is controlled at 0.95, the overall furnace time is 215min, and the furnace temperature is 1115°C. The silicon steel slabs after being discharged from the furnace are descaled by high-pressure water, and the slag shell and the original associated cast iron scale are all detached. The descaled silicon steel slabs enter the next hot rolling process.

[0046] The residual iron scale rate on the surface of the silicon steel produced in this embodiment decreased from 8.9% before implementation to 1.4%, and the edge crack rate decreased from 18.3% before implementation to 4.7%.

[0047] [Example 4]

[0048] In this embodiment, the production of oriented silicon steel (Si content 3.23%) by low temperature heating method is taken as an example.

[0049] Prepare protective coating. Material A, i.e., plastic microparticles, has a particle size of 0.05 to 1.2 mm, and a particle size distribution of 95% of particles having a particle size of 0.1 to 0.7 mm; the melting point of the plastic microparticles is 225°C; material B uses the continuous casting crystallizer protective slag used in the continuous casting of silicon steel slabs in this embodiment, with a hemisphere point temperature of 980°C and a viscosity (1300°C) of 0.10 Pa.s; material A and material B are mixed before spraying, with a ratio of 10% material A and 90% material B.

[0050] Silicon steel slabs are hot-delivered and hot-charged in the furnace, with a charging temperature of 530°C. Before charging, the protective coating mixed according to the ratio is sprayed evenly on all surfaces of the silicon steel slabs (the two ends of the slabs are not sprayed). The coating adheres to the surface of the slabs, and the coating thickness is controlled at 7mm. The silicon steel slabs after coating are heated in the furnace, and the furnace gas temperature in the heating section is controlled at 1300°C, the furnace gas air-fuel ratio is controlled at 0.96, the overall furnace time is 255min, and the furnace temperature is 1195°C. After the silicon steel slabs are discharged from the furnace, they are descaled by high-pressure water, and the slag shell and the original associated cast iron scale are all detached. The descaled silicon steel slabs enter the next hot rolling process.

[0051] The residual iron scale rate on the surface of the silicon steel produced in this embodiment decreased from 9.5% before implementation to 1.6%, and the edge crack rate decreased from 20.4% before implementation to 4.3%.

[0052] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A production method for improving the surface and edge quality of silicon steel, characterized in that: The steps include: 1) Preparing a protective coating; the protective coating is composed of material A and material B, and by volume percentage, material A: 1% to 15%, material B: 85% to 99%; the material A is plastic particles, the plastic particles are polyethylene particles or polypropylene particles, the particle size of the plastic particles is 0.05 to 1.2 mm, and the particle size distribution is that the particle size of 0.1 to 0.7 mm accounts for more than 95%; the melting point of the plastic particles is 60 to 250°C; the material B is a continuous casting crystallizer protection slag, the continuous casting crystallizer protection slag adopts the continuous casting crystallizer protection slag for silicon steel slab production, or the continuous casting crystallizer protection slag for ultra-low carbon steel production, the hemisphere point temperature of the continuous casting crystallizer protection slag is 930 to 1180°C, and the viscosity at 1300°C is 0.05 to 0.15 Pa.s; 2) Silicon steel slabs are hot transported and hot charged into the furnace, with the charging temperature ≥350°C; before charging into the furnace, the protective coating is evenly sprayed onto the surface of the slab, with a coating thickness of 2 to 10 mm; 3) Put the silicon steel slab coated with protective coating into the furnace for heating, control the temperature of the heating section to 1200-1300°C, and control the air-fuel ratio to 0.90-0.98; After heating, the plastic particles melt and burn, and the continuous casting mold protection slag and the original iron scale on the surface of the silicon steel slab form a molten thin sticky film that adheres to the surface of the slab to prevent oxidation and decarburization of the slab surface; 4) After the silicon steel slab is taken out of the furnace, high-pressure water is used to descale it. During this process, the molten slag layer formed by the molten thin mucous film meets water to form crystalline and non-crystalline slag shells and is peeled off. The descaled silicon steel slab enters the hot rolling process.