Production method of 430 stainless steel matte surface product for roof tile

Abstract

The invention discloses a production method of a 430 stainless steel matte surface product for a roof tile, and belongs to the technical field of metal processing. The surface of the 430 stainless steel matte surface steel belt prepared through the method is matte, the glossiness is uniform, the surface does not become white, and the glossiness reaches 200-250 GU; according to the mechanical properties of the product, the yield strength ranges from 310 MPa to 330 MPa, the tensile strength ranges from 510 MPa to 550 MPa, the ductility ranges from 29% to 32%, and the hardness ranges from 155 HV to 165 HV. A layer of uniform passivation film is attached to the surface of the product, the rust-proof and corrosion-resistant performance is improved, the rust-proof and corrosion-resistant performance is good, and the neutral salt spray test time reaches 600 hours. Through systematic optimization and innovation of the production process, the surface passivation, glossiness, corrosion resistance and rust resistance indexes of the steel strip are well improved, and the product has a high quality level and a wide market prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of metal processing, and particularly relates to a production method for a 430 stainless steel matte surface product for roofing tiles. Background Art

[0002] As one of the oldest building materials, tiles have been widely used for thousands of years. Tiles are the main roofing materials, which not only play the role of protecting from wind and rain and indoor lighting, but also have important decorative effects. With the continuous development of technology, the production materials of tiles are also constantly updated, and new stainless steel tiles have gradually emerged from traditional clay tiles. The steel used for roofing tiles is usually mainly plain carbon steel galvanized sheets or color-coated sheets. Although the raw material prices are low, due to problems such as easy rusting, low service life, low recyclability, and environmental pollution in the production and recycling processes, production enterprises have been seeking new materials with low energy consumption, environmental protection, and low comprehensive costs for the roofing tile field. The price of 304 stainless steel is expensive, the overall investment is large, and the comprehensive cost is high, so it has not been promoted.

[0003] 430 stainless steel, namely 10Cr17, is a ferritic stainless steel with good corrosion resistance and oxidation resistance. Its thermal conductivity is better than that of austenitic stainless steel, and its expansion coefficient is smaller than that of austenitic stainless steel. It has good thermal conductivity and mechanical properties, and the material strength is higher than that of plain carbon steel. 430 stainless steel does not contain nickel, has a low and stable price, and is the most common steel grade in the 400 series of stainless steels. Due to its excellent performance and stable and low price, its application fields are becoming more and more extensive, and it has become a substitute for 304 stainless steel in many fields and is increasingly favored by the market. Because 430 stainless steel does not contain nickel, has a cheap and stable price, a long service life, is environmentally friendly, and has a high recyclability, 430 stainless steel has a high cost performance as a roofing tile and has good promotion and market prospects.

[0004] In the production process of 430 stainless steel for roofing tiles, due to the update of product indicators, the existing process parameters cannot be directly copied, and the relevant production processes and parameters need to be adjusted for performance. For example, during the annealing and pickling of cold-rolled steel strips, it is necessary to study the process of each link such as annealing temperature, holding time, and cooling rate to improve mechanical properties and processing performance. If the annealing process is inappropriate, martensite structure may be generated and the grains may become coarse, which will affect mechanical properties and subsequent processing and use, and also affect corrosion resistance. Another example is that when 430 stainless steel is used as a roofing tile, in addition to requiring good processing performance and corrosion and rust resistance, strict requirements are also put forward for surface quality. If the pickling process is inappropriate, the surface roughness of the steel strip is uneven, and the passivation is uneven, etc., which will also affect the rust and corrosion resistance and aesthetics of the steel strip. Summary of the Invention

[0005] Aiming at the above-mentioned existing technology, the purpose of the present invention is to provide a production method for a 430 stainless steel matte surface product for roofing tiles.

[0006] In the steelmaking process of the present invention, the processes of triple dephosphorization of hot metal + phosphorus removal and slag skimming + TSR + LF + continuous casting + grinding are adopted to provide qualified continuous casting billets; the continuous casting billets are heated and kept warm in a heating furnace, hot-rolled, and hot pickled to provide qualified white skin steel strips; the white skin steel strips are rolled by a 20-high rolling mill to provide cold-hardened steel strips with the surface quality, shape, and thickness meeting the requirements; the cold-hardened steel strips are degreased + continuously annealed + neutral salt electrolytic pickling + nitric acid electrolytic pickling + nitric acid pickling to produce a product with a uniformly passivated surface and obtain a matte surface product for roofing tiles.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] In the first aspect of the present invention, a production method of a 430 stainless steel matte surface product for roofing tiles is provided, including the following steps:

[0009] (1) Adopt the processes of triple dephosphorization of hot metal, phosphorus removal and slag skimming, TSR, LF, continuous casting, and grinding to obtain continuous casting billets;

[0010] (2) The continuous casting billets are heated and kept warm, hot-rolled, and hot pickled to obtain white skin steel strips;

[0011] (3) The white skin steel strips are rolled through multiple passes to obtain cold-hardened steel strips;

[0012] (4) The cold-hardened steel strips are degreased, continuously annealed, neutral salt electrolyzed, nitric acid electrolyzed, and nitric acid pickled to produce a 430 stainless steel matte surface product for roofing tiles.

[0013] Further, in step (1), when performing TSR full hot metal smelting, bottom blowing gas is carried out. CO2 is blown in the early and middle stages, and argon is blown in the later stage. After the mass ratio of the molten steel composition meets the requirements, the molten steel is tapped into the ladle to obtain reduced molten steel; during refining, oxygen is introduced and vacuum degassing is carried out to reduce the carbon, nitrogen content and gas content in the molten steel; the continuous casting drawing speed, liquid level and precise cooling are controlled, and the continuous casting billets are ground with temperature to obtain continuous casting billets.

[0014] Further, in step (2), the continuous casting billets are discharged from the furnace, rough rolled, finish rolled, and coiled to obtain qualified hot-rolled steel strips; mechanical descaling, shot blasting descaling, sulfuric acid pickling, and nitric acid pickling are carried out on the hot-rolled steel strips;

[0015] The hot-rolling heating temperature is 1150 °C, the holding time is 220 - 230 minutes, the coiling furnace temperature is 1040 - 1080 °C, the residual oxygen content is below 6%, and the coiling temperature is 710 - 730 °C; the sulfuric acid pickling concentration is 180 - 220 g / L, the temperature is 70 - 80 °C, and the metal ion content < 75 g / L; the nitric acid concentration is 120 - 160 g / L, the temperature is 40 - 45 °C, and the metal ion content < 45 g / L.

[0016] Further, in step (3), the white skin coil is rolled through 11 - 13 passes, the roughness of the rough roll is 0.4 - 0.6 μm, and the roughness of the finishing roll is 0.1 - 0.12 μm.

[0017] Further, in step (4), during degreasing, the conductivity of the degreasing solution is 10 - 13 ms / cm, the temperature is 70 - 75 °C, and the pressure of the brushing water is 0.5 - 0.6 MPa; the conductivity of the rinsing water is ≤ 30 μs / cm.

[0018] Further, in step (4), during continuous annealing, the annealing holding temperature is 865 - 875 °C, and the holding time is 11 - 13 s; the cooling rate: when the temperature is greater than 750 °C, the cooling rate is 20 - 30 °C / s, and when the temperature is less than 750 °C, the cooling rate is 38 - 45 °C / s.

[0019] Further, in step (4), in the processes of neutral salt electrolysis, nitric acid electrolysis, and nitric acid pickling, the temperature of the neutral salt section is 70 - 75 °C, the concentration is 180 - 200 g / L, and the electrolysis current is 10 - 15 A / cm 2 , 3 < pH ≤ 6, and the metal ion content is ≤ 50 g / L; the concentration of the nitric acid electrolyte is 130 - 160 g / L, the temperature is 40 - 45 °C, and the electrolysis current is 10 - 12 A / cm 2 , and the metal ion content is ≤ 40 g / L; the concentration of the nitric acid pickling is 30 - 60 g / L, and the temperature is 45 - 50 °C.

[0020] In the second aspect of the present invention, there is provided a 430 stainless steel matte surface product for roofing tiles obtained by the production method described above. The product includes the following components by weight: carbon 0.019 - 0.03%, silicon 0.20 - 0.50%, manganese 0.30 - 0.50%, phosphorus ≤ 0.035%, sulfur ≤ 0.006%, chromium 16.5 - 17.5%, nitrogen 0.015 - 0.030%, nickel ≤ 0.30%, and the balance is Fe and impurities.

[0021] In the third aspect of the present invention, there is provided the application of the 430 stainless steel matte surface product obtained by the production method described above in the preparation of roofing tiles.

[0022] The beneficial effects of the present invention:

[0023] The stainless steel for 430 roofing tiles in the present invention reduces the carbon and nitrogen contents, the gas content and impurities in the molten steel during smelting, avoids composition segregation and internal inclusions, and improves the corrosion resistance and pitting resistance of the product; in the hot rolling process, the heating temperature, holding temperature, rolling temperature, coiling temperature and descaling process are controlled to obtain a hot-rolled steel strip with uniform properties and surface quality meeting the requirements; during the rolling of the steel strip, the shape of the steel strip is controlled by the selection of roll profile, roll shifting, shape meter, etc., and better surface quality of the steel plate is obtained through the deformation amount; through the systematic optimization and innovation of the parameters of the neutral salt electrolysis + nitric acid electrolysis + nitric acid pickling process (without using hydrofluoric acid), the present invention preferably solves the passivation, glossiness, corrosion resistance and rust resistance of the steel strip surface.

[0024] The 430 stainless steel matte surface product produced by the present invention has high mechanical properties, with a yield strength of 310 - 350 MPa, a tensile strength of 510 - 550 MPa, and a hardness of 155 - 165 HV, which is suitable for the high strength requirements of roofing tiles. The 430 stainless steel matte surface product produced by the present invention has uniform surface glossiness, with a glossiness of 200 - 250 GU (20°). Compared with other production methods, the surface matte does not turn white or shiny, meeting the requirements of customers for the matte surface of 430 stainless steel 2B products. The 430 stainless steel matte surface product produced by the present invention has good surface rust and corrosion resistance, and the neutral salt spray test reaches more than 600 hours. The 430 stainless steel matte surface product produced by the present invention has a low and stable price, a long service life, little environmental pollution, and a high recyclability. The comprehensive cost can be reduced by more than 30% compared with roofing tiles made of galvanized sheets, color-coated sheets, etc., meeting the market requirements for stainless steel for roofing tiles, and the product has broad market application prospects in the field of roofing tiles. Detailed implementation mode

[0025] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0026] As described in the background art, the present invention provides a production method for a 430 stainless steel matte surface product for roofing tiles, including the following steps:

[0027] 1. Adopt the processes of triple dephosphorization of hot metal, phosphorus removal and slag skimming, TSR, LF, continuous casting, and grinding to obtain a continuous casting billet.

[0028] The steelmaking process adopts hot metal three-decarburization, phosphorus removal and slag skimming, TSR, LF, continuous casting, and grinding processes to reduce carbon and nitrogen contents, stabilize chromium content, control inclusion and gas contents, stabilize casting speed and liquid level, and grind the continuous casting billet while it is still warm. When conducting full hot metal smelting in TSR, bottom blowing gas is used. CO2 is blown in the early and middle stages, and argon is blown in the later stage. After the mass ratio of the molten steel composition meets the requirements, the molten steel is tapped into the ladle to obtain reduced molten steel. Through refining in a VOD furnace, oxygen is introduced for vacuum degassing to reduce the carbon, nitrogen, and gas contents in the molten steel, avoiding defects such as gas holes and inclusions. Control the continuous casting speed, liquid level, and precise cooling. Grind the continuous casting billet while it is still warm to remove surface defects of the steel strip and obtain the continuous casting billet.

[0029] 2. The continuous casting billet is heated and insulated in a heating furnace, hot-rolled, and hot pickled to obtain a white skin steel strip.

[0030] The heating temperature and holding time of the continuous casting billet are controlled in the heating furnace. After leaving the furnace, it undergoes rough rolling (single-pass phosphorus removal), finish rolling (steckel mill + three-stand tandem mill), and coiling to obtain a qualified hot-rolled steel strip: The hot-rolled steel strip undergoes mechanical descaling, shot blasting descaling, sulfuric acid pickling, and single acid (HNO3) pickling to remove the oxide on the surface of the steel strip.

[0031] The hot-rolling heating temperature is 1150°C, and the holding time is 220 - 230 minutes. The steckel mill and three-stand tandem mill processes are adopted to roll the hot-rolled steel strip with a finished thickness of 3.0mm * 1245mm. The temperature of the coiling furnace is controlled at 1060 ± 20°C, and the residual oxygen content is controlled below 6%. The coiling temperature is controlled at 720 ± 10°C). During the rolling process, the high-pressure descaling water for even-numbered passes is turned off to control the surface quality of the steel strip; hot pickling line.

[0032] Adopt mechanical descaling, shot blasting descaling, sulfuric acid pickling (concentration 180 - 220g / L, temperature 70 - 80°C, metal ion content < 75g / L), mixed acid pickling (nitric acid concentration 120 - 160g / L, temperature 40 - 45°C, metal ion content < 45g / L), and heavy brushing pickling processes to remove the oxide on the surface of the steel strip, improve defects such as peeling marks and color differences on the surface of the steel strip. Improve the uniformity of the surface roughness of the steel strip.

[0033] 3. The white skin steel strip is rolled through multiple passes to obtain a cold-rolled hard steel strip.

[0034] Through a 20-high reversible rolling mill, a small-deformation, multi-pass rolling mill, and controlled by different roll profiles, one intermediate tandem roll, a shape meter, a thickness gauge, etc., a cold-rolled hard product with thickness, shape, and surface all meeting the requirements is obtained. Specifically as follows:

[0035] Adopt a Sendzimir type 20-high rolling mill to roll the 3.0 * 1245mm 430 white skin coil through 11 passes to a 0.4 * 1245mm cold-rolled hard product. The roughness of the rough roll is 0.4 - 0.6μm, and the roughness of the finish roll is 0.1 - 0.12μm.

[0036] 4. The cold-rolled hard steel strip is degreased, continuously annealed, electrolyzed with neutral salt, electrolyzed with nitric acid, and pickled with nitric acid to produce a 430 stainless steel matte surface product for roofing tiles.

[0037] The cold-rolled hard steel strip is degreased to remove the rolling oil and foreign matters on the surface of the steel strip; the steel strip is annealed in a horizontal continuous annealing furnace heated by natural gas. By controlling the annealing temperature, holding time, cooling rate, and oxygen content in the furnace, an annealed steel strip with uniform surface oxidation and performance meeting the requirements is obtained; the annealed steel strip is electrolyzed and pickled with neutral salt, electrolyzed and pickled with nitric acid, and pickled with nitric acid to obtain a product with uniform surface passivation and a matte surface.

[0038] 4.1 Degreasing of the cold-rolled product of the rolling mill:

[0039] The conductivity of the degreasing solution is 10 - 13 ms / cm, the temperature is 70 - 75 °C, the pressure of the brushing water is 0.5 - 0.6 MPa; the conductivity of the rinsing water is ≤ 30 μs / cm. Remove the rolling oil and impurities on the surface of the steel strip, and control the residue of the degreasing agent and the water mark residue.

[0040] 4.2 Continuous annealing using a horizontal annealing furnace heated by natural gas

[0041] During the annealing process, a roofing tile annealing process is developed. The annealing holding temperature is 870 ± 5 °C, the holding time is 11 - 13 s, and the cooling rate: when the temperature is greater than 750 °C, the cooling rate is 20 °C / s, and when the temperature is less than 750 °C, the cooling rate is greater than 38 °C / s.

[0042] 4.3 Neutral salt (sodium sulfate) electrolysis, nitric acid electrolysis, and nitric acid pickling process. The temperature in the neutral salt section is 70 - 75 °C, the concentration is 180 - 200 g / L, the electrolysis current is 10 - 15 A / cm 2 , 3 < pH ≤ 6, the metal ion content is ≤ 50 g / L. The concentration of the nitric acid electrolyte is 130 - 160 g / L, the temperature is 40 - 45 °C, the electrolysis current is 10 - 12 A / CM2, and the metal ion content is ≤ 40 g / L. The concentration of the nitric acid pickling is 30 - 60 g / L, and the temperature is 45 - 50 °C.

[0043] 5. Trim the edges and wind the steel strip into coils on the finishing line.

[0044] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below with specific embodiments.

[0045] The test materials not specifically described in the embodiments of the present invention are all conventional test materials in the art and can be obtained through commercial channels.

[0046] Example 1

[0047] Production of 430 stainless steel matte surface products with a thickness of 0.4mm:

[0048] 1. Adopt the processes of triple dephosphorization of hot metal, phosphorus removal and slag skimming, TSR, LF, continuous casting, and grinding to obtain continuous casting billets.

[0049] In steelmaking, the processes of triple dephosphorization of hot metal, phosphorus removal and slag skimming, TSR, LF, continuous casting, and grinding are adopted to reduce carbon and nitrogen contents, stabilize chromium content, control inclusion and gas contents, stabilize casting speed and liquid level, and perform grinding on the continuous casting billet while it is still warm. When conducting full hot metal smelting in TSR, bottom blowing gas is used. CO2 is blown in the early and middle stages, and argon is blown in the later stage. After the mass ratio of the molten steel composition meets the requirements, the molten steel is tapped into the ladle to obtain reduced molten steel; through refining in a VOD furnace, oxygen is introduced for vacuum degassing to reduce the carbon, nitrogen, and gas contents in the molten steel and avoid defects such as gas pores and inclusions; control the continuous casting speed, liquid level, and precise cooling, perform grinding on the continuous casting billet while it is still warm, remove surface defects of the steel strip, and obtain continuous casting billets.

[0050] The surface of the continuous casting billet has no defects such as scars, pits, and cracks. The composition of the continuous casting billet is shown in Table 1 below:

[0051] Table 1 Chemical composition of products for 430 stainless steel roofing tiles

[0052] Project C％ Si% Mn% P％ S％ Cr％ N％ Ni% Content 0.019 0.20 0.30 0.035 0.006 16.5 0.015 0.30

[0053] 2. The continuous casting billet is heated and held in a heating furnace, hot rolled, and hot pickled to obtain a white skin steel strip.

[0054] The heating temperature and holding time of the continuous casting billet are controlled in the heating furnace. After leaving the furnace, it undergoes rough rolling (single-pass phosphorus removal), finish rolling (tandem mill + three-stand tandem mill), and coiling to obtain qualified hot-rolled steel strips: The hot-rolled steel strips are subjected to mechanical descaling, shot blasting descaling, sulfuric acid pickling, single acid (HNO3) pickling to remove the oxide layer on the surface of the steel strip.

[0055] The hot rolling heating temperature is 1150°C, the holding time is 223 minutes. The tandem mill and three-stand tandem mill processes are adopted to roll the finished product into a hot-rolled steel strip with a thickness of 3.0mm * 1245mm. The temperature of the coiling furnace is controlled at 1060 ± 20°C, the residual oxygen content is controlled below 6%, and the coiling temperature is controlled at 717°C. During the rolling process, the high-pressure descaling water for even-numbered passes is turned off to control the surface quality of the steel strip; hot pickling line.

[0056] Adopt mechanical descaling, shot blasting descaling, sulfuric acid pickling (concentration 195g / L, temperature 73°C, metal ion content < 75g / L), mixed acid pickling (nitric acid concentration 134g / L, temperature 42°C, metal ion content < 45g / L), and heavy brushing pickling processes to remove the oxide layer on the surface of the steel strip, improve defects such as peeling marks and color differences on the surface of the steel strip. Improve the uniformity of the surface roughness of the steel strip.

[0057] 3. The white skin steel strip is rolled through multiple passes to obtain a cold-hardened steel strip.

[0058] Through a 20-high reversible rolling mill, a small-deformation, multi-pass rolling mill, and by controlling with different roll profiles, a middle series of rolls, a shape meter, a thickness gauge, etc., a cold-hardened product with the required thickness, flatness, and surface quality is obtained. Specifically as follows:

[0059] Using a Sendzimir-type 20-high rolling mill, a 3.0*1245mm 430 white skin coil is rolled to a 0.4*1245mm cold-hardened product through 11 passes. The roughness of the rough rolls is 0.4 - 0.6μm, and the roughness of the finishing rolls is 0.1 - 0.12μm. The rolling process is shown in Table 2:

[0060] Table 2 Rolling Process of Products for 430 Stainless Steel Roofing Tiles

[0061]

[0062] 4. The cold-hardened steel strip is degreased, continuously annealed, electrolyzed with neutral salt, electrolyzed with nitric acid, and pickled with nitric acid to produce a 430 stainless steel matte surface product for roofing tiles.

[0063] The cold-hardened steel strip is degreased to remove the rolling oil and foreign substances on the surface of the steel strip; the steel strip is annealed using a horizontal continuous annealing furnace heated by natural gas. By controlling the annealing temperature, holding time, cooling rate, and oxygen content in the furnace, an annealed steel strip with uniform surface oxidation and performance meeting the requirements is obtained; the annealed steel strip is pickled by electrolysis with neutral salt, electrolysis with nitric acid, and pickled with nitric acid to obtain a product with uniform surface passivation and a matte surface.

[0064] 4.1 The cold-hardened product of the rolling mill undergoes degreasing:

[0065] The conductivity of the degreasing solution is 11 ms / cm, the temperature is 71°C, the pressure of the brushing water is 0.5 MPa; the conductivity of the rinsing water is ≤30 μs / cm. Remove the rolling oil and impurities on the surface of the steel strip, and control the residue of the degreasing agent and the residue of water marks.

[0066] 4.2 Continuous annealing is carried out using a horizontal annealing furnace heated by natural gas.

[0067] During the annealing process, a roofing tile annealing process is developed. The annealing holding temperature is 869°C, the holding time is 11S, and the cooling rate: when the temperature is greater than 750°C, the cooling rate is 22°C / S, and when the temperature is less than 750°C, the cooling rate is 39°C / s.

[0068] 4.3 Neutral salt (sodium sulfate) electrolysis + nitric acid electrolysis + nitric acid pickling process. The temperature of the neutral salt section is 73°C, the concentration is 185 g / L, and the electrolysis current is 13 A / cm 2 , PH = 5, and the metal ion content is ≤50 g / L. The concentration of the nitric acid electrolyte is 152 g / L, the temperature is 42°C, and the electrolysis current is 10 A / cm 2, the metal ion content is ≤ 40 g / L. The concentration of nitric acid pickling is 45 g / L, and the temperature is 42 °C.

[0069] 5. The steel strip is trimmed and split into coils on the finishing line.

[0070] The production parameters of Examples 2-4 are shown in Table 3, and the rest are the same as those of Example 1.

[0071] Table 3: Process parameters of each example

[0072] Example 2 Example 3 Example 4 Standard Hot rolling holding time (min) 221 227 225 220-230 Coiling temperature (°C) 713 726 720 710-730 Sulfuric acid pickling concentration (g / L) 187 218 203 180-220 Sulfuric acid pickling temperature (°C) 71 79 76 70-80 Single acid pickling nitric acid concentration (g / L) 125 158 142 120-160 Single acid pickling temperature (°C) 40 45 43 40-45 Degreasing solution conductivity (ms / cm) 10 13 12 10-13 Degreasing solution temperature (°C) 70 74 73 70-75 Brushing water pressure (MPa) 0.5 0.6 0.6 0.5-0.6 Annealing holding temperature (°C) 866 874 870 865-875 Annealing holding time (S) 11 13 12 11-13 Cooling rate (°C / S) when temperature is greater than 750°C 20 25 24 20-30 Cooling rate (°C / S) when temperature is less than 750°C 38 42 40 38-45 Neutral salt section temperature (°C) 71 74 72 70-75 Neutral salt section concentration (g / L) 192 183 194 180-200 Neutral salt section electrolytic current (A / cm2) 12 10 11 10-15 Neutral salt section pH 5 4 5 3-6 Nitric acid electrolyte concentration (g / L) 135 137 145 130-160 Nitric acid electrolyte temperature (°C) 40 41 43 40-45 <![CDATA[Electrolysis current (A / cm 2 )]]> 11 12 11 10-12 Nitric acid pickling concentration (g / L) 35 37 51 30-60 Nitric acid pickling temperature (°C) 46 45 47 45-50

[0073] Comparative example

[0074] In this comparative example, a bell-type annealing furnace is used in step (5), and the rest of the steps and parameters are the same as those of Example 4. The specific steps of the treatment are as follows: the temperature of the bell-type annealing furnace is 850 °C, the holding time is 5 s, and the cooling rate is 50 °C / s.

[0075] Test example

[0076] The performance of the coiled sheets obtained in Examples 1-4 and the comparative example was tested by the following methods:

[0077] The glossiness was tested using a glossmeter. The yield strength, tensile strength, and elongation were tested according to the steps in "GB / T 228.1-2021 Metallic materials - Tensile testing - Part 1: Method of test at room temperature". The hardness was tested according to the steps in "GB / T 4340.1-2024 Metallic materials - Vickers hardness testing - Part 1: Test method". The salt spray experiment was tested according to the steps in "GB / T 10125-2021 Corrosion tests in artificial atmospheres - Salt spray tests".

[0078] The test results are shown in Table 4 below.

[0079] Table 4: Performance of the coiled sheets obtained in each example

[0080] Project Example 1 Example 2 Example 3 Example 4 Comparative example Glossiness (GU) 213 236 227 241 187 Yield strength (MPa) 317 325 342 331 295 Tensile strength (MPa) 526 536 513 548 467 Elongation (%) 29.1 31.4 30.5 31.3 27.4 Hardness (HV) 155 160 158 161 143 Neutral salt spray test time (h) 607 621 614 628 580

[0081] The 430 stainless steel matte surface steel strip prepared in the examples of the present invention has a matte surface, uniform glossiness, no white spots on the surface, and the glossiness reaches 200-250 GU (20°); the mechanical properties are stable and the strength is high: the yield strength of the product's mechanical properties is 310-330 MPa, the tensile strength is 510-550 Mpa, the elongation is 29-32%, and the hardness is 155-165 HV; a uniform passivation film is attached to the product surface, improving the rust and corrosion resistance performance, with good rust and corrosion resistance performance, and the neutral salt spray test time reaches 600 hours.

[0082] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various modifications and variations can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A method for producing 430 stainless steel matte surface products for roof tiles, characterized in that: The steps include: (1) The continuous casting billet is obtained by adopting the processes of three removals of molten iron, dephosphorization and slag removal, TSR, LF, continuous casting and grinding; (2) The continuous casting billet is subjected to heating and heat preservation, hot rolling, and hot pickling processes to obtain a white steel strip; (3) The white steel strip is rolled in multiple passes to obtain a cold-hardened steel strip; (4) The cold-hardened steel strip is subjected to degreasing, continuous annealing, neutral salt electrolysis, nitric acid electrolysis, and nitric acid pickling to produce 430 stainless steel matte surface products for roof tiles.

2. The method for producing 430 stainless steel matte surface products for roof tiles according to claim 1, characterized in that: In step (1), during TSR full molten iron smelting, gas is blown from the bottom, CO2 is blown in the early and middle stages, and argon is blown in the later stages. After the mass ratio of the molten steel components reaches the requirements, the molten steel is discharged into a ladle to obtain reduced molten steel; during refining, oxygen is introduced and vacuum degassing is performed to reduce the carbon and nitrogen contents and gas content in the molten steel; the continuous casting speed and liquid level are controlled as well as the precise cooling, and the continuous casting billet is ground while warm to obtain a continuous casting billet.

3. The method for producing 430 stainless steel matte surface products for roof tiles according to claim 1, characterized in that: In step (2), the continuous casting slab is taken out of the furnace and subjected to rough rolling, finish rolling, and coiling to obtain a qualified hot-rolled steel strip; the hot-rolled steel strip is subjected to mechanical crushing, shot blasting for phosphorus removal, sulfuric acid pickling, and nitric acid pickling; Hot rolling heating temperature is 1150℃, holding time is 220-230 minutes, coiling furnace temperature is 1040-1080℃, residual oxygen content is below 6%, coiling temperature is 710-730℃; sulfuric acid pickling concentration is 180-220g / L, temperature is 70-80℃, metal ion content is <75g / L; nitric acid concentration is 120-160g / L, temperature is 40-45℃, metal ion content is <45g / L.

4. The method for producing 430 stainless steel matte surface products for roof tiles according to claim 1, characterized in that: In step (3), the white coil is rolled through 11-13 passes, with the roughness of the coarse roll being 0.4-0.6 μm and the roughness of the fine roll being 0.1-0.12 μm.

5. The method for producing 430 stainless steel matte surface products for roof tiles according to claim 1, characterized in that: In step (4), during degreasing, the conductivity of the degreasing liquid is 10-13ms / cm, the temperature is 70-75°C, the pressure of the scrubbing water is 0.5-0.6MPa; and the conductivity of the rinsing water is ≤30μs / cm.

6. The method for producing 430 stainless steel matte surface products for roof tiles according to claim 1, characterized in that: In step (4), during the continuous annealing process, the annealing holding temperature is 865-875°C, and the holding time is 11-13s; the cooling rate: when the temperature is greater than 750°C, the cooling rate is 20-30°C / s, and when the temperature is less than 750°C, the cooling rate is 38-45°C / s.

7. The method for producing 430 stainless steel matte surface products for roof tiles according to claim 1, characterized in that: In step (4), in the processes of neutral salt electrolysis, nitric acid electrolysis, and nitric acid pickling, the temperature of the neutral salt section is 70 - 75 °C, the concentration is 180 - 200 g / L, the electrolysis current is 10 - 15 A / cm 2 , 3 < pH ≤ 6, the metal ion content is ≤ 50 g / L; the concentration of the nitric acid electrolyte is 130 - 160 g / L, the temperature is 40 - 45 °C, the electrolysis current is 10 - 12 A / cm 2 , the metal ion content is ≤ 40 g / L; the concentration of the nitric acid pickling is 30 - 60 g / L, and the temperature is 45 - 50 °C.

8. The 430 stainless steel matte surface product for roofing tiles obtained by the production method according to any one of claims 1 to 7, characterized in that: The product comprises the following components by weight: carbon 0.019-0.03%, silicon 0.20-0.50%, manganese 0.30-0.50%, phosphorus ≤0.035%, sulfur ≤0.006%, chromium 16.5-17.5%, nitrogen 0.015-0.030%, nickel ≤0.30%, and the rest is Fe and impurities.

9. Use of the 430 stainless steel matte surface product obtained by the production method according to any one of claims 1 to 7 in the preparation of roof tiles.

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