Method for overcoming line scale defect of 300-series stainless steel BA plate

Abstract

The invention discloses a method for solving the line scale defect of a 300-series stainless steel BA plate, which comprises the following steps: grinding and proportioning bauxite, quartz sand and chromium ore powder to prepare coating powder which comprises the following chemical components: 6-8% of chromium oxide, 8-10% of silicon oxide, 81-86% of aluminum oxide and less than or equal to 1% of other components; the coating powder, water glass and water are mixed and stirred according to the weight ratio of 1: 1: 2, and a coating is prepared; (3) the surface temperature of a 300-series stainless steel casting blank is naturally cooled to 350-450 DEG C, the surface of the casting blank is ground, the surface roughness of the casting blank is controlled to be smaller than or equal to 50 microns, when the surface temperature of the casting blank is 210-250 DEG C, a spray gun is used for spraying the coating on the upper surface and the lower surface of the casting blank, and the spraying thickness is controlled to be 0.2-0.3 mm; and after the coating is sprayed, the casting blank is heated in a heating furnace and subjected to hot rolling, and the 300-series stainless steel BA plate is obtained. According to the method, the problems that in-grain boundary oxidation of the surface of the casting blank occurs during heating and oxide in the grain boundary cannot be eliminated after hot rolling are solved, and therefore the problem of line scale defects of the 300-series stainless steel BA plate is effectively solved.

Description

Technical Field

[0001] The invention belongs to the technical field of stainless steel production, and in particular relates to a method for solving the linear scale defect of 300 series stainless steel BA plates. Background Art

[0002] The high-end 300 series stainless steel BA plate market is mainly occupied by Japan's Nisshin Steel and South Korea's Posco, while the domestic 300 series stainless steel BA plate has low user recognition and low market share mainly due to the high line phosphorus defect rate and low production rate of the production plant.

[0003] The scale defects of 300 series stainless steel BA plates are mainly distributed within 150mm of the rolled edge, with a defect length of about 5 to 20mm and a width of about 0.5 to 2mm. The scale defects of 300 series stainless steel BA plates affect the performance and aesthetics of the end product. In severe cases, the rolled coils will be downgraded or even scrapped.

[0004] After research and analysis, the main cause of the line scale defect of 300 series stainless steel BA plate is: the surface of the 300 series stainless steel ingot is heated by a heating furnace, and the grain boundaries on the surface of the ingot are oxidized. After hot rolling, the oxides in the grain boundaries cannot be eliminated, resulting in line scale defects on the surface of the BA plate after cold rolling. Summary of the invention

[0005] In order to solve the above technical problems existing in the prior art, the present invention provides a method for solving the line scale defect of 300 series stainless steel BA plate, comprising the following steps:

[0006] (1) grinding and mixing bauxite, quartz sand and chromium ore powder to prepare a coating powder, wherein the chemical composition of the coating powder is controlled by weight percentage as follows: chromium oxide: 6-8%, silicon oxide: 8-10%, aluminum oxide: 81-86%, and others ≤ 1%;

[0007] (2) mixing the coating powder, water glass and water in a weight ratio of 1:1:2 to prepare a coating, and loading the coating into a spray gun for standby use;

[0008] (3) The surface temperature of the 300 series stainless steel ingot is naturally cooled to 350-450°C, and the surface of the ingot is ground to control the surface roughness of the ingot to ≤50 μm. When the surface temperature of the ingot is 210-250°C, the coating is sprayed on the upper and lower surfaces of the ingot using a spray gun, and the spraying thickness is controlled to be 0.2-0.3 mm.

[0009] Furthermore, in the above method for solving the scale defect of 300 series stainless steel BA plate, after spraying the coating, the ingot is heated in a heating furnace and hot rolled to obtain the 300 series stainless steel BA plate.

[0010] Furthermore, in the above method for solving the scale defect of 300 series stainless steel BA plate, a fully automatic ingot hot grinding machine is used and a 30# hot grinding wheel is used to grind the surface of the ingot.

[0011] As a specific implementation method, in the above-mentioned method for solving the line scale defects of 300 series stainless steel BA plate, the 300 series stainless steel is SUS304 austenitic stainless steel, and the cross-sectional dimensions of the SUS304 austenitic stainless steel ingot are thickness × width: 200mm×(1000~2100mm), and the chemical composition of the SUS304 austenitic stainless steel is as follows by weight percentage: 0.03%≤C≤0.05%, 0.30%≤Si≤0.70%, 1.00%≤Mn≤1.50%, P≤0.043%, S≤0.010%, 18.0%≤Cr≤18.6%, 8.00%≤Ni≤8.50%, 0.02%≤N≤0.06%, and the rest are Fe and unavoidable impurities.

[0012] As a specific implementation method, in the above-mentioned method for solving the line scale defects of 300 series stainless steel BA plate, the 300 series stainless steel is SUS304L austenitic stainless steel, and the cross-sectional dimensions of the SUS304L austenitic stainless steel ingot are thickness × width: 200mm×(1000~2100mm), and the chemical composition of the SUS304L austenitic stainless steel is as follows by weight percentage: C≤0.03%, 0.30%≤Si≤0.70%, 1.50%≤Mn≤2.00%, P≤0.043%, S≤0.010%, 18.00%≤Cr≤18.60%, 8.00%≤Ni≤8.50%, 0.02%≤N≤0.06%, and the rest are Fe and unavoidable impurities.

[0013] The method of the present invention for solving the line scale defect of 300 series stainless steel BA plate has the following advantages and beneficial effects: the present invention designs relevant spray material formulas, matching ingot grinding and spraying process parameters, and evenly sprays a coating with high-temperature oxidation resistance on the surface of the ingot that has been finely ground and has a certain surface temperature. The spray material can be completely and firmly attached to the surface of the ingot. The ingot sprayed with the coating is heated in a heating furnace and hot-rolled, which solves the problem of oxidation within the grain boundaries of the ingot surface during heating and the inability to eliminate the oxides within the grain boundaries after hot rolling. Therefore, the line scale defect problem of 300 series stainless steel BA plate is effectively solved, and the quality of 300 series stainless steel BA plate is improved. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0015] As mentioned above, the main causes of line scale defects in 300 series stainless steel BA plates are: oxidation within the grain boundaries on the surface of the ingot during heating, and the inability to eliminate the oxides within the grain boundaries after hot rolling. Therefore, the main technical concept of the method for solving the line scale defects in 300 series stainless steel BA plates proposed in the present invention is to spray a coating with high-temperature oxidation resistance on the surface of the 300 series stainless steel ingot, then heat it in a heating furnace and hot roll it.

[0016] Specifically, the method for solving the line scale defect of 300 series stainless steel BA plate of the present invention comprises the following steps:

[0017] (1) Grinding and mixing bauxite, quartz sand and chromium ore powder to prepare coating powder, wherein the chemical composition of the coating powder is controlled by weight percentage as follows: chromium oxide: 6-8%, silicon oxide: 8-10%, aluminum oxide: 81-86%, and others ≤1%.

[0018] (2) The coating powder, water glass and water are mixed and stirred in a weight ratio of 1:1:2 to prepare a coating, and the coating is loaded into a spray gun for standby use.

[0019] (3) The surface temperature of the 300 series stainless steel ingot is naturally cooled to 350-450°C, and the ingot surface is ground by a fully automatic ingot hot grinding machine and a 30# hot grinding wheel. The surface roughness of the ingot is controlled to be ≤50 μm by grinding. When the surface temperature of the ingot is 210-250°C, the coating is sprayed on the upper and lower surfaces of the ingot by a spray gun, and the spraying thickness is controlled to be 0.2-0.3 mm. After spraying the coating, the ingot is heated in a heating furnace and hot rolled to obtain a 300 series stainless steel BA plate.

[0020] As an embodiment, the present invention is applicable to the production of SUS304 austenitic stainless steel BA plate, wherein the cross-sectional dimensions of the SUS304 austenitic stainless steel ingot are thickness × width: 200 mm × (1000-2100 mm), and the chemical composition of the SUS304 austenitic stainless steel is as follows by weight percentage: 0.03% ≤ C ≤ 0.05%, 0.30% ≤ Si ≤ 0.70%, 1.00% ≤ Mn ≤ 1.50%, P ≤ 0.043%, S ≤ 0.010%, 18.0% ≤ Cr ≤ 18.6%, 8.00% ≤ Ni ≤ 8.50%, 0.02% ≤ N ≤ 0.06%, and the rest are Fe and unavoidable impurities.

[0021] As another embodiment, the present invention is applicable to the production of SUS304L austenitic stainless steel BA plate, wherein the cross-sectional dimensions of the SUS304L austenitic stainless steel ingot are thickness × width: 200 mm × (1000-2100 mm), and the chemical composition of the SUS304L austenitic stainless steel is as follows by weight percentage: C≤0.03%, 0.30%≤Si≤0.70%, 1.50%≤Mn≤2.00%, P≤0.043%, S≤0.010%, 18.00%≤Cr≤18.60%, 8.00%≤Ni≤8.50%, 0.02%≤N≤0.06%, and the rest are Fe and unavoidable impurities.

[0022] The method for solving the line scale defect of 300 series stainless steel BA plate of the present invention is described in detail below in conjunction with specific embodiments.

[0023] Example 1

[0024] The steel involved in Example 1 is SUS304 austenitic stainless steel, the cross-sectional dimensions of the ingot are thickness × width: 200 mm × 1250 mm, and the steel composition is: C: 0.04%, Si: 0.51%, Mn: 1.11%, P: 0.040%, S: 0.002%, Cr: 18.2%, Ni: 8.02%, N: 0.04%, and the rest is Fe and unavoidable impurities. The method for solving the line scale defect of 300 series stainless steel BA plate in Example 1 comprises the following steps:

[0025] (1) Grinding and mixing bauxite, quartz sand and chromium ore powder to prepare coating powder, wherein the chemical composition of the coating powder is as follows by weight: chromium oxide: 6.5%, silicon oxide: 9.1%, aluminum oxide: 84.0%, and others: 0.4%.

[0026] (2) The coating powder, water glass and water are mixed and stirred in a weight ratio of 1:1:2 to prepare a coating, and the coating is loaded into a spray gun for standby use.

[0027] (3) After the SUS304 austenitic stainless steel ingot was cut, the surface temperature of the ingot was naturally cooled to 368°C, and the ingot surface was ground using a fully automatic ingot hot grinding machine and a 30# hot grinding wheel. After grinding, the surface roughness of the ingot was 41 μm. When the surface temperature of the ingot was 223°C, a spray gun was used to spray paint on the upper and lower surfaces of the ingot with a spray thickness of 0.24 mm. After spraying the paint, the ingot was heated in a heating furnace and hot rolled to obtain SUS304 austenitic stainless steel BA plate.

[0028] According to actual production tests, the scale defect rate of the SUS304 austenitic stainless steel BA plate produced by the application of Example 1 is 0%.

[0029] Example 2

[0030] The steel involved in Example 2 is SUS304 austenitic stainless steel, the cross-sectional dimensions of the ingot are thickness × width: 200 mm × 1525 mm, and the steel composition is: C: 0.04%, Si: 0.56%, Mn: 1.20%, P: 0.038%, S: 0.001%, Cr: 18.3%, Ni: 8.01%, N: 0.04%, and the rest is Fe and unavoidable impurities. The method for solving the line scale defect of 300 series stainless steel BA plate in Example 2 comprises the following steps:

[0031] (1) Grinding and mixing bauxite, quartz sand and chromium ore powder to prepare coating powder, wherein the chemical composition of the coating powder is as follows by weight: chromium oxide: 6.7%, silicon oxide: 9.0%, aluminum oxide: 84.1%, and others: 0.2%.

[0032] (2) The coating powder, water glass and water are mixed and stirred in a weight ratio of 1:1:2 to prepare a coating, and the coating is loaded into a spray gun for standby use.

[0033] (3) After the SUS304 austenitic stainless steel ingot was cut, the surface temperature of the ingot was naturally cooled to 362°C, and the ingot surface was ground using a fully automatic ingot hot grinding machine and a 30# hot grinding wheel. After grinding, the surface roughness of the ingot was 39 μm. When the surface temperature of the ingot was 212°C, a spray gun was used to spray paint on the upper and lower surfaces of the ingot with a spray thickness of 0.22 mm. After spraying the paint, the ingot was heated in a heating furnace and hot rolled to obtain SUS304 austenitic stainless steel BA plate.

[0034] According to actual production tests, the scale defect rate of the SUS304 austenitic stainless steel BA plate produced by the application of Example 2 is 0%.

[0035] Example 3

[0036] The steel involved in Example 3 is SUS304L austenitic stainless steel, the cross-sectional dimensions of the ingot are thickness × width: 200 mm × 1250 mm, and the steel composition is: C: 0.02%, Si: 0.58%, Mn: 1.55%, P: 0.041%, S: 0.002%, Cr: 18.06%, Ni: 8.06%, N: 0.03%, and the rest is Fe and unavoidable impurities. The method for solving the line scale defect of 300 series stainless steel BA plate in Example 3 includes the following steps:

[0037] (1) Grinding and mixing bauxite, quartz sand and chromium ore powder to prepare coating powder, wherein the chemical composition of the coating powder is as follows by weight: chromium oxide: 7.5%, silicon oxide: 8.2%, aluminum oxide: 83.9%, and others: 0.4%.

[0038] (2) The coating powder, water glass and water are mixed and stirred in a weight ratio of 1:1:2 to prepare a coating, and the coating is loaded into a spray gun for standby use.

[0039] (3) After the SUS304L austenitic stainless steel ingot was cut, the surface temperature of the ingot was naturally cooled to 377°C, and the surface of the ingot was ground using a fully automatic ingot hot grinding machine and a 30# hot grinding wheel. After grinding, the surface roughness of the ingot was 43 μm. When the surface temperature of the ingot was 211°C, a spray gun was used to spray paint on the upper and lower surfaces of the ingot with a spray thickness of 0.25 mm. After spraying the paint, the ingot was heated in a heating furnace and hot rolled to obtain SUS304L austenitic stainless steel BA plate.

[0040] According to actual production tests, the scale defect rate of the SUS304L austenitic stainless steel BA plate produced by the application of Example 3 is 0%.

[0041] Example 4

[0042] The steel involved in Example 4 is SUS304L austenitic stainless steel, the cross-sectional dimensions of the ingot are thickness × width: 200 mm × 1550 mm, and the steel composition is: C: 0.01%, Si: 0.62%, Mn: 1.62%, P: 0.038%, S: 0.001%, Cr: 18.23%, Ni: 8.10%, N: 0.04%, and the rest is Fe and unavoidable impurities. The method for solving the line scale defect of 300 series stainless steel BA plate in Example 4 comprises the following steps:

[0043] (1) Grinding and mixing bauxite, quartz sand and chromium ore powder to prepare coating powder, wherein the chemical composition of the coating powder is as follows by weight: chromium oxide: 7.1%, silicon oxide: 8.7%, aluminum oxide: 83.7%, and others: 0.5%.

[0044] (2) The coating powder, water glass and water are mixed and stirred in a weight ratio of 1:1:2 to prepare a coating, and the coating is loaded into a spray gun for standby use.

[0045] (3) After the SUS304L austenitic stainless steel ingot was cut, the surface temperature of the ingot was naturally cooled to 372°C, and the ingot surface was ground using a fully automatic ingot hot grinding machine and a 30# hot grinding wheel. After grinding, the surface roughness of the ingot was 38 μm. When the surface temperature of the ingot was 237°C, a spray gun was used to spray paint on the upper and lower surfaces of the ingot with a spray thickness of 0.26 mm. After spraying the paint, the ingot was heated in a heating furnace and hot rolled to obtain SUS304L austenitic stainless steel BA plate.

[0046] According to actual production tests, the scale defect rate of the SUS304L austenitic stainless steel BA plate produced by the application of Example 4 is 0%.

[0047] In summary, the method for solving the line scale defect of 300 series stainless steel BA plate of the present invention designs relevant spray material formula, matching ingot grinding and spraying process parameters, and evenly sprays the coating with high-temperature oxidation resistance on the surface of the ingot that has been finely ground and has a certain surface temperature. The spray material can be completely and firmly attached to the surface of the ingot. The ingot after being sprayed with the coating is heated in a heating furnace and hot rolled, which solves the problem of oxidation within the grain boundaries of the ingot surface during heating and the inability to eliminate the oxides within the grain boundaries after hot rolling. Therefore, the line scale defect problem of 300 series stainless steel BA plate is effectively solved, and the quality of 300 series stainless steel BA plate is improved.

[0048] It should be noted that, in this article, the term "comprise" or any other variation thereof is intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such article or device.

[0049] It should also be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the present invention.

Claims

1. A method for solving the line scale defect of 300 series stainless steel BA plate, characterized in that: The steps include: (1) grinding and mixing bauxite, quartz sand and chromium ore powder to prepare a coating powder, wherein the chemical composition of the coating powder is controlled by weight percentage as follows: chromium oxide: 6-8%, silicon oxide: 8-10%, aluminum oxide: 81-86%, and others ≤ 1%; (2) mixing the coating powder, water glass and water in a weight ratio of 1:1:2 to prepare a coating, and loading the coating into a spray gun for standby use; (3) The surface temperature of the 300 series stainless steel ingot is naturally cooled to 350-450°C, and the surface of the ingot is ground to control the surface roughness of the ingot to ≤50 μm. When the surface temperature of the ingot is 210-250°C, the coating is sprayed on the upper and lower surfaces of the ingot using a spray gun, and the spraying thickness is controlled to be 0.2-0.3 mm.

2. The method for solving the line scale defect of 300 series stainless steel BA plate according to claim 1, characterized in that: After spraying the coating, the ingot is heated in a heating furnace and hot rolled to produce 300 series stainless steel BA plates.

3. The method for solving the line scale defect of 300 series stainless steel BA plate according to claim 1, characterized in that: Use a fully automatic billet hot grinding machine and a 30# hot grinding wheel to grind the billet surface.

4. The method for solving the line scale defect of 300 series stainless steel BA plate according to any one of claims 1 to 3, characterized in that: The 300 series stainless steel is SUS304 austenitic stainless steel. The cross-sectional dimensions of the SUS304 austenitic stainless steel ingot are thickness × width: 200 mm × (1000-2100 mm). The chemical composition of the SUS304 austenitic stainless steel is as follows by weight percentage: 0.03% ≤ C ≤ 0.05%, 0.30% ≤ Si ≤ 0.70%, 1.00% ≤ Mn ≤ 1.50%, P ≤ 0.043%, S ≤ 0.010%, 18.0% ≤ Cr ≤ 18.6%, 8.00% ≤ Ni ≤ 8.50%, 0.02% ≤ N ≤ 0.06%, and the rest is Fe and unavoidable impurities.

5. The method for solving the line scale defect of 300 series stainless steel BA plate according to any one of claims 1 to 3, characterized in that: The 300 series stainless steel is SUS304L austenitic stainless steel. The cross-sectional dimensions of the SUS304L austenitic stainless steel ingot are thickness × width: 200 mm × (1000-2100 mm). The chemical composition of the SUS304L austenitic stainless steel is as follows by weight percentage: C≤0.03%, 0.30%≤Si≤0.70%, 1.50%≤Mn≤2.00%, P≤0.043%, S≤0.010%, 18.00%≤Cr≤18.60%, 8.00%≤Ni≤8.50%, 0.02%≤N≤0.06%, and the rest is Fe and unavoidable impurities.