An aging-resistant stainless steel material and its casting process

Abstract

This invention relates to the field of stainless steel casting preparation technology, specifically to an aging-resistant stainless steel material and its casting process. The chemical composition, by weight percentage, includes: C: 0.01-0.03%, Cr: 18-22%, Ni: 8-11%, Mo: 0.1-0.8%, Mn: 0.5-1.5%, Si: 0.2-1.0%, Cu: 1.0-3.6%, Nb: 0.2-0.5%, N: 0.15-0.25%, with the remainder being Fe. This invention achieves a series of synergistic effects through precise proportioning and a rigorous process flow of lime, fluorite, aluminum powder, and sodium silicate solution. This optimizes the physicochemical properties of the smelting slag. The high-alkalinity, high-fluidity slag produced by the synergistic effect of lime and fluorite provides ideal thermodynamic and kinetic conditions for desulfurization and dephosphorization reactions. Harmful elements such as sulfur and phosphorus can rapidly combine with CaO to form stable compounds that enter the slag phase and are removed, thus improving the toughness and corrosion resistance of the stainless steel.

Description

Technical Field

[0001] This invention relates to the field of stainless steel casting preparation technology, specifically to an aging-resistant stainless steel material and its casting process. Background Technology

[0002] Stainless steel is widely used in chemical, energy, medical, and consumer goods industries due to its excellent corrosion resistance, high-temperature strength, and good processing properties. However, the corrosion resistance of stainless steel largely depends on its purity and the integrity of the final surface. During the smelting process, impurities such as sulfur and phosphorus can significantly deteriorate the toughness and corrosion resistance of stainless steel; and if the oxide scale and weld spots formed during subsequent processing are not properly pickled, they can easily lead to surface defects, which will also impair its corrosion resistance.

[0003] Currently, slag-making processes are commonly used to remove harmful elements in the smelting and refining of stainless steel. However, traditional slag systems suffer from problems such as high melting point, high viscosity, and uneven composition, resulting in low dephosphorization and desulfurization efficiency and difficulty in effectively adsorbing non-metallic inclusions, ultimately leading to unsatisfactory purity of the molten steel. In addition, while conventional combinations of fluorite and lime can improve fluidity, improper proportioning and mixing processes can easily cause uneven effects or excessive erosion of the furnace lining refractory materials.

[0004] Subsequently, after smelting, the stainless steel surface needs to be pickled. Traditional mixed acid pickling, such as nitric acid-hydrofluoric acid systems, can effectively remove oxide scale, but it poses environmental pollution risks and can easily lead to a decline in workpiece surface quality due to excessive corrosion or deposition of reaction products, affecting the uniformity and stability of the stainless steel surface. Therefore, there is an urgent need in this field for an innovative stainless steel material and its casting process that can synergistically improve the corrosion resistance of the material from two core levels: steel purity control and surface treatment.

[0005] Therefore, the present invention provides an aging-resistant stainless steel material and its casting process to solve the problems existing in the prior art. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an aging-resistant stainless steel material and its casting process.

[0007] An aging-resistant stainless steel material, wherein the chemical composition by weight percentage includes: C: 0.01-0.03%, Cr: 18-22%, Ni: 8-11%, Mo: 0.1-0.8%, Mn: 0.5-1.5%, Si: 0.2-1.0%, Cu: 1.0-3.6%, Nb: 0.2-0.5%, N: 0.15-0.25%, with the remainder being Fe.

[0008] A casting process for an aging-resistant stainless steel material specifically includes the following steps:

[0009] S1: Smelting and Refining

[0010] The above-mentioned components are added to the EAF furnace for melting to obtain stainless steel liquid, which is then transferred to the AOD furnace. 3-5% of the total mass of the stainless steel liquid and 3-4 cm in diameter of pre-melted slag are added to the AOD furnace. After the temperature of the stainless steel liquid reaches 1620-1650℃, oxygen blowing begins. When the decarburization is greater than 0.3%, the furnace door is tilted 30° to allow slag to flow. Slag flow is stopped when the amount of slag flowing is greater than 90% of the total steel slag in the furnace. Then, 2-3% of the total mass of the stainless steel liquid and 5-15 mm of purification slag balls are added. Oxygen blowing continues for 30-60 minutes. The steel is then tapped into the LF furnace to obtain crude steel.

[0011] S2: Pickling

[0012] Crude steel is rolled into steel coils through rough rolling and continuous rolling. The steel coils are cooled for 72-96 hours and then annealed at 1100-1200℃. After that, they are shot peened with stainless steel shot and then pickled with pickling solution to obtain stainless steel coils.

[0013] S3: Rolling and annealing treatment

[0014] Stainless steel coils are precision rolled and then annealed at a high temperature of 1080-1150℃, and then cooled to room temperature of 23-25℃ to obtain aging-resistant stainless steel materials.

[0015] Furthermore, step S2 pickling specifically includes the following steps:

[0016] Crude steel is rolled into steel coils through rough rolling and continuous rolling. The steel coils are cooled for 72-96 hours and then annealed at 1100-1200℃ to obtain annealed steel coils.

[0017] Subsequently, the annealed steel coil is shot-blasted using a shot blasting machine with stainless steel shot at a speed of 70-100 m / s and a diameter of 0.3-0.6 mm to obtain a pretreated steel coil.

[0018] Next, add the pickling solution to the soaking tank, completely immerse the pretreated steel coil in the soaking tank, heat it to 38-42℃, introduce compressed air to stir the soaking tank, remove it and wash it 2-3 times with running cold water to obtain stainless steel coil.

[0019] Furthermore, the specific preparation process of the pre-melted slag in step S1 includes the following steps:

[0020] Pour 62-70% lime, 25-30% fluorite and 3-8% aluminum powder by weight into a forced mixer and dry mix at 200-300 r / min for 3-5 minutes.

[0021] Then add 8-12% sodium silicate solution of the total mass of the system, and add it to the dry powder being stirred by atomization spraying. Continue stirring for 10-15 minutes until the mixture is uniform in color, free of white dry powder particles, and forms premixed granules.

[0022] The premixed pellets are transferred to a molding press and pressed into spherical shapes with a diameter of 3-4 cm under a pressure of 20-40 MPa to obtain a green body;

[0023] The green body is left to stand for 12-24 hours in an environment with room temperature of 23-25℃ and humidity greater than 80%. The green body that has been cured at room temperature is placed in an oven and baked at 220-280℃ for 1-2 hours. Then it is left to stand at room temperature of 23-25℃ to obtain pre-melted slag.

[0024] Furthermore, the specific preparation process of the purified slag balls in step S1 includes the following steps:

[0025] Mix and grind 55-60% magnesia, 30-35% alumina and 5-10% silicon carbide by weight, and pass through a 150-mesh sieve. Then add 0.2-0.4% foaming agent by weight of the system and form small balls of 5-15mm in a disc pelletizer. Then calcine at 1200-1300℃ for 10-20 minutes to obtain purified slag balls.

[0026] Furthermore, the specific preparation process of the pickling solution in step S2 includes the following steps:

[0027] Add deionized water to the container, start the stirrer and stir at 100-120 r / min, and slowly add ammonium persulfate while stirring to make the concentration of ammonium persulfate 80-150 g / L. Continue stirring until the ammonium persulfate is completely dissolved to obtain a colorless and transparent solution.

[0028] While stirring, add the weighed citric acid and gluconic acid to the colorless and transparent solution in sequence, so that the concentration of citric acid is 60-100 g / L and the concentration of gluconic acid is 20-40 g / L. After they are completely dissolved, add thiourea and stir until completely dissolved, so that the concentration of thiourea is 2-6 g / L.

[0029] Finally, add 0.5-2 g / L of surfactant, stir continuously for 15-20 minutes, and then let stand for 30-40 minutes to obtain pickling solution.

[0030] Furthermore, the concentration of the sodium silicate solution is 35-40 wt%.

[0031] Furthermore, when compressed air is introduced to agitate the soaking tank, the pressure of the compressed air is 0.1-0.3MPa, the airflow velocity is 0.01-0.05m / s, and the agitation time is 2-4 minutes.

[0032] Furthermore, the foaming agent is calcium carbonate or magnesium carbonate with a particle size of 2-5 μm.

[0033] Furthermore, the surfactant is sodium dodecyl sulfate.

[0034] The present invention has the following advantages:

[0035] 1. This invention achieves a series of synergistic effects through precise proportioning and rigorous process flow of lime, fluorite, aluminum powder, and sodium silicate solution, optimizing the physicochemical properties of the smelting slag. Lime, as an alkaline oxide, provides the framework for the pre-melted slag, while the addition of fluorite disrupts the crystal structure of lime, acting as a powerful flux to lower the melting point of the slag system and significantly reduce its viscosity. Through forced stirring and pelletizing in the early stages, lime and fluorite achieve close contact at the microscale. During smelting, fluorite can instantly and uniformly act on each lime particle, causing it to dissolve rapidly and form a homogeneous liquid slag with excellent fluidity. Subsequently, the atomized spraying of sodium silicate solution ensures that the dry powders of lime and fluorite are uniformly wetted. After being wetted, molded, and baked, the loose powder is not only solidified into spheres of moderate strength that are easy to transport and feed, but also the SiO2 and Na2O produced by the decomposition of sodium silicate through lime and fluorite during the high-temperature process participate in the construction of the slag system, further optimizing the fluidity and foaming ability of stainless steel slag. The high-alkalinity and high-fluidity slag produced by the synergistic effect of lime and fluorite provides ideal thermodynamic and kinetic conditions for desulfurization and dephosphorization reactions. Harmful elements such as sulfur and phosphorus can quickly combine with CaO to form stable compounds that enter the slag phase and are removed. At the same time, the good slag fluidity enables it to effectively adsorb floating deoxidation products and other non-metallic inclusions, thereby greatly purifying the molten steel and improving the toughness and corrosion resistance of stainless steel.

[0036] 2. In the stainless steel pickling solution formulation of this invention, citric acid, gluconic acid, and thiourea are used in combination. Citric acid, as the main acid, provides an acidic environment to dissolve the oxide scale. More importantly, it acts as a strong complexing agent, forming stable and soluble complexes with dissolved iron and chromium ions to prevent their redeposition and promote the continuous reaction. Glucolic acid, as an auxiliary complexing agent for citric acid, has a strong complexing ability for iron ions, further enhancing the prevention of iron redeposition on the stainless steel surface. It also works synergistically with citric acid to form a denser protective film on the metal surface, improving surface smoothness. Thiourea, on the other hand, has the dual function of a corrosion inhibitor and a reducing agent; it can selectively adsorb onto the surface of the stainless steel being cleaned. A protective film is formed on the surface, effectively inhibiting excessive acid corrosion of the substrate and thus protecting the substrate. At the same time, it can reduce high-valent chromium, facilitating complexation removal. This synergistic system brings multiple significant benefits to stainless steel pickling. First, it ensures excellent surface quality of stainless steel. Through the dual effects of strong complexation and substrate protection, a clean and smooth stainless steel surface can be obtained. Second, the complexation effect generated by the synergistic effect of citric acid and gluconic acid continuously removes reaction products and automatically promotes the pickling reaction, which can quickly remove oxide scale and weld spots. At the same time, the corrosion inhibition effect of thiourea ensures a gentle and uniform process, provides excellent substrate protection, fundamentally prevents the risk of material failure caused by excessive pickling, and extends the service life of the workpiece.

[0037] 3. This invention employs a step-by-step method of using pre-melted slag and subsequently added magnesia-alumina-based purification slag balls for stainless steel smelting. In the initial oxygen blowing stage, large-particle pre-melted slag is added, utilizing its rapid melting characteristics to quickly form a high-basicity, highly oxidizing slag. Its main function is dephosphorization, creating conditions for subsequent slag removal of phosphorus. After removing over 90% of the high-phosphorus slag, smaller-particle magnesia-alumina purification slag balls are added. The purpose is to achieve deep desulfurization and adsorption of inclusions under a reducing atmosphere, and to utilize MgO to adjust the viscosity and basicity of the new slag. To mitigate the erosion of the refractory materials in the AOD furnace, the two types of slag are added separately rather than mixed together. This avoids the premature consumption of CaO by magnesia during the critical dephosphorization period, which would severely deteriorate the slag basicity and ensure the achievement of deep dephosphorization. At the same time, controlling the diameter of the pre-melted slag to 3-4 cm and the particle size of the purified slag to 5-15 mm optimizes the melting kinetics and the continuity of the action of the slag. Through a step-by-step and particle size- and raw material-specific treatment strategy, harmful interactions are avoided and the reaction process is optimized, ultimately resulting in the stable production of high-quality stainless steel with low phosphorus, low sulfur, and high purity. Attached Figure Description

[0038] Figure 1 This is a flowchart of the casting process for the aging-resistant stainless steel material of the present invention. Detailed Implementation

[0039] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention. Example 1

[0040] An aging-resistant stainless steel material, wherein the chemical composition by weight percentage includes: C: 0.01%, Cr: 18%, Ni: 8%, Mo: 0.1%, Mn: 0.5%, Si: 0.2%, Cu: 1.0%, Nb: 0.2%, N: 0.15%, with the remainder being Fe.

[0041] A casting process for aging-resistant stainless steel materials, such as Figure 1 As shown, the specific steps include:

[0042] S1: Smelting and Refining

[0043] Pour 67% lime, 30% fluorite and 3% aluminum powder by weight into a forced mixer and dry mix at 200 r / min for 3 minutes.

[0044] Then add 8% of the total mass of the system of 35wt% sodium silicate solution, and slowly and evenly add it to the dry powder being stirred by atomization spraying. Continue stirring for 10 minutes until the mixture is uniform in color, free of white dry powder particles, and forms premixed clumps.

[0045] The premixed pellets are transferred to a molding press and pressed into spherical shapes with a diameter of 3 cm under a pressure of 20 MPa to obtain a green body;

[0046] The green body was left to stand for 12 hours in an environment with room temperature of 23℃ and humidity greater than 80%. The green body that had been cured at room temperature was placed in an oven and baked at 220℃ for 1 hour. Then it was left to stand at room temperature of 23℃ to obtain pre-melted slag.

[0047] 55% magnesia, 35% alumina and 10% silicon carbide by weight were mixed, ground and passed through a 150-mesh sieve. Then, 0.2% of the foaming agent calcium carbonate with a particle size of 2μm was added to the system. The mixture was then made into 5mm pellets in a disc pelletizer and calcined at 1200℃ for 10 minutes to obtain purified slag pellets.

[0048] The above-mentioned components are added to the EAF furnace for melting to obtain stainless steel liquid, which is then transferred to the AOD furnace. 3% of the total mass of the stainless steel liquid is added to the AOD furnace as pre-melted slag. After the temperature of the stainless steel liquid reaches 1620℃, oxygen blowing begins. When the decarburization is greater than 0.3%, the furnace door is tilted 30° to allow slag to flow. Slag flow is stopped when the amount of slag flowing is greater than 90% of the total mass of steel slag in the furnace. Then, 2% of the total mass of the stainless steel liquid as purified slag balls is added, and oxygen blowing continues for 30-60 minutes. The steel is then tapped into the LF furnace to obtain crude steel.

[0049] S2: Pickling

[0050] Add deionized water to a container with a PVC inner wall, start the stirrer at 100 r / min, and slowly add ammonium persulfate while stirring to make the concentration of ammonium persulfate 80 g / L. Continue stirring until the ammonium persulfate is completely dissolved to obtain a colorless and transparent solution.

[0051] While stirring, add the weighed citric acid and gluconic acid to the colorless and transparent solution in sequence, so that the concentration of citric acid is 60 g / L and the concentration of gluconic acid is 20 g / L. After they are completely dissolved, add thiourea and stir until completely dissolved, so that the concentration of thiourea is 2 g / L.

[0052] Finally, add 0.5 g / L of the surfactant sodium dodecyl sulfate, stir continuously for 15 minutes, and then let stand for 30 minutes to mature, to obtain the pickling solution;

[0053] Crude steel is rolled into steel coils through rough rolling and continuous rolling. The steel coils are cooled for 72 hours and then annealed at 1100℃ to obtain annealed steel coils.

[0054] Subsequently, the annealed steel coil was shot blasted using a shot blasting machine with stainless steel shot at a speed of 70 m / s and a diameter of 0.3 mm, resulting in a pretreated steel coil.

[0055] Next, add the pickling solution to the soaking tank, completely immerse the pretreated steel coil in the soaking tank, heat it to 38°C, and introduce compressed air to stir the soaking tank. The pressure of the compressed air is 0.1MPa, the airflow speed is 0.01m / s, and stirring is maintained for 2 minutes. After taking it out, wash it twice with running cold water to obtain stainless steel coil.

[0056] S3: Rolling and annealing treatment

[0057] Stainless steel coils are precision rolled, then annealed at 1080℃, and cooled to room temperature of 23℃ to obtain aging-resistant stainless steel material. Example 2

[0058] An aging-resistant stainless steel material, wherein the chemical composition by weight percentage includes: C: 0.02%, Cr: 20%, Ni: 10%, Mo: 0.4%, Mn: 1.0%, Si: 0.7%, Cu: 2.3%, Nb: 0.4%, N: 0.20%, with the remainder being Fe.

[0059] A casting process for aging-resistant stainless steel materials, such as Figure 1 As shown, the specific steps include:

[0060] S1: Smelting and Refining

[0061] Pour 70% lime, 25% fluorite and 5% aluminum powder by weight into a forced mixer and dry mix at 250 r / min for 4 minutes.

[0062] Then add 10% of the total mass of the system with a concentration of 38wt% sodium silicate solution, and slowly and evenly add it to the dry powder being stirred by atomization spraying. Continue stirring for 13 minutes until the mixture is uniform in color, free of white dry powder particles, and forms premixed clumps.

[0063] The premixed pellets are transferred to a molding press and pressed into spherical shapes with a diameter of 3.5 cm under a pressure of 30 MPa to obtain a green body;

[0064] The green body was left to stand for 18 hours in an environment with room temperature of 24℃ and humidity greater than 80%. The green body that had been cured at room temperature was placed in an oven and baked at 250℃ for 1.5 hours. Then it was left to stand at room temperature of 24℃ to obtain pre-melted slag.

[0065] 60% magnesia, 35% alumina and 5% silicon carbide by weight were mixed, ground and passed through a 150-mesh sieve. Then, 0.3% of the foaming agent calcium carbonate with a particle size of 4μm was added. The mixture was made into 10mm balls in a disc pelletizer and then calcined at 1250℃ for 15 minutes to obtain purified slag balls.

[0066] The above-mentioned components are added to the EAF furnace for melting to obtain stainless steel liquid, which is then transferred to the AOD furnace. 4% of the total mass of the stainless steel liquid is added to the AOD furnace as pre-melted slag. After the temperature of the stainless steel liquid reaches 1635℃, oxygen blowing begins. When the decarburization is greater than 0.3%, the furnace door is tilted 30° to allow slag to flow. Slag flow is stopped when the amount of slag flowing is greater than 90% of the total mass of steel slag in the furnace. Then, 2.5% of the total mass of the stainless steel liquid as purified slag balls are added, and oxygen blowing continues for 45 minutes. The steel is then tapped into the LF furnace to obtain crude steel.

[0067] S2: Pickling

[0068] Add deionized water to a container with a PVC inner wall, start the stirrer at 110 r / min, and slowly add ammonium persulfate while stirring to make the concentration of ammonium persulfate 115 g / L. Continue stirring until the ammonium persulfate is completely dissolved to obtain a colorless and transparent solution.

[0069] While stirring, add the weighed citric acid and gluconic acid to the colorless and transparent solution in sequence, so that the concentration of citric acid is 80 g / L and the concentration of gluconic acid is 30 g / L. After they are completely dissolved, add thiourea and stir until completely dissolved, so that the concentration of thiourea is 4 g / L.

[0070] Finally, add 1.3 g / L of sodium dodecyl sulfate surfactant, stir continuously for 18 minutes, and then let stand for 35 minutes to obtain pickling solution;

[0071] Crude steel is rolled into steel coils through rough rolling and continuous rolling. The steel coils are cooled for 84 hours and then annealed at 1150℃ to obtain annealed steel coils.

[0072] Subsequently, the annealed steel coil was shot blasted using a shot blasting machine with stainless steel shot at a speed of 85 m / s and a diameter of 0.4 mm, resulting in a pretreated steel coil.

[0073] Next, add the pickling solution to the soaking tank, completely immerse the pretreated steel coil in the soaking tank, heat it to 40°C, and introduce compressed air to stir the soaking tank. The pressure of the compressed air is 0.2MPa, the airflow speed is 0.03m / s, and stirring is maintained for 3 minutes. After taking it out, wash it twice with running cold water to obtain stainless steel coil.

[0074] S3: Rolling and annealing treatment

[0075] Stainless steel coils are precision rolled, then annealed at 1120℃, and cooled to room temperature of 24℃ to obtain aging-resistant stainless steel material. Example 3

[0076] An aging-resistant stainless steel material, wherein the chemical composition by weight percentage includes: C: 0.03%, Cr: 22%, Ni: 11%, Mo: 0.8%, Mn: 1.5%, Si: 1.0%, Cu: 3.6%, Nb: 0.5%, N: 0.25%, with the remainder being Fe.

[0077] A casting process for aging-resistant stainless steel materials, such as Figure 1 As shown, the specific steps include:

[0078] S1: Smelting and Refining

[0079] Pour 62% lime, 30% fluorite and 8% aluminum powder by weight into a forced mixer and dry mix at 300 r / min for 5 minutes.

[0080] Then add 12% of the total mass of the system with a concentration of 40wt% sodium silicate solution, and slowly and evenly add it to the dry powder being stirred by atomizing spray. Continue stirring for 15 minutes until the mixture is uniform in color, free of white dry powder particles, and forms premixed clumps.

[0081] The premixed pellets are transferred to a molding press and pressed into spherical shapes with a diameter of 4 cm under a pressure of 40 MPa to obtain a green body;

[0082] The green body was left to stand for 24 hours in an environment with room temperature of 25°C and humidity greater than 80%. The green body that had been cured at room temperature was placed in an oven and baked at 280°C for 2 hours. Then it was left to stand at room temperature of 25°C to obtain pre-melted slag.

[0083] 60% magnesia, 30% alumina and 10% silicon carbide by weight were mixed, ground and passed through a 150-mesh sieve. Then, 0.4% of the foaming agent calcium carbonate with a particle size of 5μm was added. The mixture was made into 15mm pellets in a disc pelletizer and then calcined at 1300℃ for 20 minutes to obtain purified slag pellets.

[0084] The above-mentioned components are added to the EAF furnace for melting to obtain stainless steel liquid, which is then transferred to the AOD furnace. 5% of the total mass of the stainless steel liquid is added to the AOD furnace as pre-melted slag. After the temperature of the stainless steel liquid reaches 1650℃, oxygen blowing begins. When the decarburization is greater than 0.3%, the furnace door is tilted 30° to allow slag to flow. Slag flow is stopped when the amount of slag flowing is greater than 90% of the total mass of steel slag in the furnace. Then, 3% of the total mass of the stainless steel liquid as purified slag balls is added, and oxygen blowing continues for 60 minutes. The steel is then tapped into the LF furnace to obtain crude steel.

[0085] S2: Pickling

[0086] Add deionized water to a container with a PVC inner wall, start the stirrer at 120 r / min, and slowly add ammonium persulfate while stirring to make the concentration of ammonium persulfate 150 g / L. Continue stirring until the ammonium persulfate is completely dissolved to obtain a colorless and transparent solution.

[0087] While stirring, add the weighed citric acid and gluconic acid to the colorless and transparent solution in sequence, so that the concentration of citric acid is 100 g / L and the concentration of gluconic acid is 40 g / L. After they are completely dissolved, add thiourea and stir until completely dissolved, so that the concentration of thiourea is 6 g / L.

[0088] Finally, add 2 g / L of the surfactant sodium dodecyl sulfate, stir continuously for 20 minutes, and then let stand for 40 minutes to mature, to obtain the pickling solution;

[0089] Crude steel is rolled into steel coils through rough rolling and continuous rolling. The steel coils are cooled for 96 hours and then annealed at 1200℃ to obtain annealed steel coils.

[0090] Subsequently, the annealed steel coil was shot blasted using a shot blasting machine with stainless steel shot at a speed of 100 m / s and a diameter of 0.6 mm, resulting in a pretreated steel coil.

[0091] Next, add the pickling solution to the soaking tank, completely immerse the pretreated steel coil in the soaking tank, heat it to 42°C, and introduce compressed air to stir the soaking tank. The pressure of the compressed air is 0.3MPa, the airflow speed is 0.05m / s, and stirring is maintained for 4 minutes. After taking it out, wash it 3 times with running cold water to obtain stainless steel coil.

[0092] S3: Rolling and annealing treatment

[0093] Stainless steel coils are precision rolled, then annealed at 1150℃, and cooled to room temperature of 25℃ to obtain aging-resistant stainless steel material.

[0094] Comparative Example 1:

[0095] Compared with Example 1, the difference of Comparative Example 1 is that the sodium silicate solution in step S1 is replaced with deionized water by an equal mass, while the other steps remain unchanged. This is referred to as Comparative Example 1.

[0096] Comparative Example 2:

[0097] Compared with Example 1, Comparative Example 2 differs in that the mass of lime in step S1 is replaced with fluorite, while the other steps remain unchanged. It is referred to as Comparative Example 2.

[0098] Comparative Example 3:

[0099] Compared with Example 1, the difference of Comparative Example 3 is that the mass of fluorite in step S1 is replaced with lime, while the other steps remain unchanged. It is referred to as Comparative Example 3.

[0100] Comparative Example 4:

[0101] Compared with Example 1, Comparative Example 4 differs in that the citric acid in step S2 is replaced with gluconic acid by mass, while the other steps remain unchanged. It is referred to as Comparative Example 4.

[0102] Comparative Example 5:

[0103] Compared with Example 1, Comparative Example 5 differs in that gluconic acid in step S2 is replaced with citric acid by mass, while the other steps remain unchanged. It is referred to as Comparative Example 5.

[0104] Comparative Example 6:

[0105] Compared with Example 1, the difference of Comparative Example 6 is that only pre-melted slag is added in step S1, and no purification slag balls are added. Specifically, it is: "An aging-resistant stainless steel material, wherein the chemical composition by weight percentage includes: C: 0.01%, Cr: 18%, Ni: 8%, Mo: 0.1%, Mn: 0.5%, Si: 0.2%, Cu: 1.0%, Nb: 0.2%, N: 0.15%, and the remainder is Fe;

[0106] S1: Smelting and Refining

[0107] Pour 67% lime, 30% fluorite and 3% aluminum powder by weight into a forced mixer and dry mix at 200 r / min for 3 minutes.

[0108] Then add 8% of the total mass of the system of 35wt% sodium silicate solution, and slowly and evenly add it to the dry powder being stirred by atomization spraying. Continue stirring for 10 minutes until the mixture is uniform in color, free of white dry powder particles, and forms premixed clumps.

[0109] The premixed pellets are transferred to a molding press and pressed into spherical shapes with a diameter of 3 cm under a pressure of 20 MPa to obtain a green body;

[0110] The green body was left to stand for 12 hours in an environment with room temperature of 23℃ and humidity greater than 80%. The green body that had been cured at room temperature was placed in an oven and baked at 220℃ for 1 hour. Then it was left to stand at room temperature of 23℃ to obtain pre-melted slag.

[0111] The above-mentioned components were added to the EAF furnace for melting to obtain stainless steel liquid, which was then transferred to the AOD furnace. 3% of the total mass of the stainless steel liquid was added to the AOD furnace as pre-melted slag. After the temperature of the stainless steel liquid reached 1620℃, oxygen blowing was started. When the decarburization amount was greater than 0.3%, the furnace door was tilted 30° to allow slag to flow. Slag flow was stopped when the amount of slag flowing was greater than 90% of the total mass of steel slag in the furnace. Then, 2% of the total mass of the stainless steel liquid as pre-melted slag was added, and oxygen blowing continued for 30 minutes. The steel was then tapped into the LF furnace to obtain crude steel. The remaining steps remained unchanged and were recorded as Comparative Example 6.

[0112] Comparative Example 7:

[0113] Compared with Example 1, Comparative Example 7 differs in that only purification slag balls are added in step S1, and no pre-melted slag is added. "An aging-resistant stainless steel material, wherein the chemical composition by weight percentage includes: C: 0.01%, Cr: 18%, Ni: 8%, Mo: 0.1%, Mn: 0.5%, Si: 0.2%, Cu: 1.0%, Nb: 0.2%, N: 0.15%, and the remainder is Fe;

[0114] S1: Smelting and Refining

[0115] 55% magnesia, 35% alumina and 10% silicon carbide by weight were mixed, ground and passed through a 150-mesh sieve. Then, 0.2% of the foaming agent calcium carbonate with a particle size of 2μm was added to the system. The mixture was then made into 5mm pellets in a disc pelletizer and calcined at 1200℃ for 10 minutes to obtain purified slag pellets.

[0116] The above-mentioned components were added to the EAF furnace for melting to obtain stainless steel liquid, which was then transferred to the AOD furnace. 3% of the total mass of the stainless steel liquid was added to the AOD furnace as purification slag balls. Oxygen blowing was started after the stainless steel liquid reached 1620℃. When the decarburization rate was greater than 0.3%, the furnace door was tilted 30° to allow slag to flow. Slag flow was stopped when the amount of slag flowing exceeded 90% of the total mass of steel slag in the furnace. Then, 2% of the total mass of the stainless steel liquid as purification slag balls was added, and oxygen blowing continued for 30 minutes. The steel was then tapped into the LF furnace to obtain crude steel. The remaining steps remained unchanged, and this was recorded as Comparative Example 7.

[0117] Comparative Example 8:

[0118] Compared with Example 1, Comparative Example 8 differs in that, in step S1, the pre-melted slag and purified slag balls are simultaneously added to the AOD furnace for smelting, specifically: "S1: Smelting and Refining"

[0119] Pour 67% lime, 30% fluorite and 3% aluminum powder by weight into a forced mixer and dry mix at 200 r / min for 3 minutes.

[0120] Then add 8% of the total mass of the system of 35wt% sodium silicate solution, and slowly and evenly add it to the dry powder being stirred by atomization spraying. Continue stirring for 10 minutes until the mixture is uniform in color, free of white dry powder particles, and forms premixed clumps.

[0121] The premixed pellets are transferred to a molding press and pressed into spherical shapes with a diameter of 3 cm under a pressure of 20 MPa to obtain a green body;

[0122] The green body was left to stand for 12 hours in an environment with room temperature of 23℃ and humidity greater than 80%. The green body that had been cured at room temperature was placed in an oven and baked at 220℃ for 1 hour. Then it was left to stand at room temperature of 23℃ to obtain pre-melted slag.

[0123] 55% magnesia, 35% alumina and 10% silicon carbide by weight were mixed, ground and passed through a 150-mesh sieve. Then, 0.2% of the foaming agent calcium carbonate with a particle size of 2μm was added to the system. The mixture was then made into 5mm pellets in a disc pelletizer and calcined at 1200℃ for 10 minutes to obtain purified slag pellets.

[0124] The above-mentioned components were added to the EAF furnace for melting to obtain stainless steel liquid, which was then transferred to the AOD furnace. 3% of the total mass of the stainless steel liquid was added to the AOD furnace as pre-melted slag and 2% of the total mass of the stainless steel liquid as purified slag balls. After the temperature of the stainless steel liquid reached 1620℃, oxygen blowing was started. When the decarburization amount was greater than 0.3%, the furnace door was tilted 30° to allow slag to flow. After the amount of slag flowing was greater than 90% of the total mass of steel slag in the furnace, slag flowing was stopped, and oxygen blowing continued for 30 minutes. The steel was then tapped into the LF furnace to obtain crude steel. The remaining steps remained unchanged and were recorded as Comparative Example 8.

[0125] Examples 1-3 and Comparative Examples 1-8 were cut into 5cm*5cm samples and subjected to the following tests:

[0126] According to GB / T32571-2016 "Corrosion of Metals and Alloys - Test Method for Intergranular Corrosion of High-Chromium Ferritic Stainless Steel", the corrosion resistance of Examples 1-3 and Comparative Examples 1-5 was tested using the sulfuric acid-ferric sulfate corrosion test. The corrosion resistance was evaluated by calculating the weight loss after corrosion, and the results are shown in Table 1.

[0127] The phosphorus and sulfur content of Examples 1-3 and Comparative Examples 6-8 was detected by spectroscopic detection method, and the results are shown in Table 2.

[0128]

[0129]

[0130] As can be seen from Table 1, the weight loss in Examples 1-3 was between 0.17 and 0.21 g, while in Comparative Example 1, after replacing the sodium silicate solution with deionized water, the weight loss increased from 0.17 g to 0.92 g. This indicates that sodium silicate, as a binder, can promote the formation of pre-melted slag, improve the refining effect, and thus enhance the corrosion resistance of stainless steel.

[0131] Comparative Examples 2-3 showed that using fluorite or lime alone resulted in a significant increase in weight loss and a decrease in the corrosion resistance of stainless steel. This indicates that the synergistic effect of fluorite and lime, together with sodium silicate solution, in preparing pre-melted slag can adjust the alkalinity and fluidity of stainless steel liquid during smelting, promote the removal of impurities, and thus improve the corrosion resistance of stainless steel.

[0132] Comparative Examples 4-5 show that the weight loss also increased when citric acid or gluconic acid was used alone, indicating that citric acid and gluconic acid need to work synergistically in the pickling solution. Using either acid alone resulted in a weight loss of nearly 1g, indicating that the corrosion resistance of stainless steel decreased.

[0133] As can be seen from Table 2, in Examples 1-3, the phosphorus content was ≤0.005% and the sulfur content was ≤0.019%, reaching the level of high-purity stainless steel, far exceeding the standard. In Comparative Examples 6 and 7, which used pre-melted slag or purified slag balls alone, the phosphorus content increased to over 0.009% and the sulfur content increased to over 0.03%, proving that the combined use of pre-melted slag and purified slag balls can achieve deep dephosphorization and desulfurization. In Comparative Example 8, which used pre-melted slag and purified slag balls simultaneously, the phosphorus content was 0.0085% and the sulfur content increased to 0.027%, which also had a negative impact on the purity of the stainless steel material.

[0134] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Parts not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. An age-resistant stainless steel material, characterized by, The chemical composition includes, in terms of percentage by weight, C: 0.01-0.03%, Cr: 18-22%, Ni: 8-11%, Mo: 0.1-0.8%, Mn: 0.5-1.5%, Si: 0.2-1.0%, Cu: 1.0-3.6%, Nb: 0.2-0.5%, N: 0.15-0.25%, and the rest is Fe; The casting process of the above-mentioned anti-aging stainless steel material specifically includes the following steps: S1: Melting and refining Pour 62-70% lime, 25-30% fluorite and 3-8% aluminum powder by weight percentage into a forced stirrer, dry mix for 3-5 minutes at a speed of 200-300 r / min; Then add 8-12% sodium silicate solution to the total mass of the system, and add it to the stirring dry powder in the form of atomized spraying, continue stirring for 10-15 minutes until the mixture is uniform in color and there are no white dry powder particles, forming a premixed ball; Transfer the premixed ball to a molding machine and press it into a spherical shape with a diameter of 3-4 cm under a pressure of 20-40 MPa to obtain a blank; Place the blank in an environment with a room temperature of 23-25°C and a humidity of greater than 80% for 12-24 hours, place the blank cured at room temperature into an oven, bake at a temperature of 220-280°C for 1-2 hours, and then stand until the room temperature is 23-25°C to obtain a pre-melted slag; Add the above-mentioned components to the EAF furnace for melting to obtain a stainless steel liquid, and add the pre-melted slag with a diameter of 3-4 cm to the AOD furnace, the pre-melted slag accounts for 3-5% of the total mass of the stainless steel liquid, start blowing oxygen after the temperature of the stainless steel liquid reaches 1620-1650°C, stop the slag flow when the decarburization amount is greater than 0.3% and the furnace door is tilted by 30°, the amount of slag flow is greater than 90% of the total amount of steel slag in the furnace, then add the purification slag ball with a particle size of 5-15 mm, which accounts for 2-3% of the total mass of the stainless steel liquid, continue blowing oxygen and continue for 30-60 minutes, avoid slag and pour out the steel into the LF furnace to obtain crude steel; S2: Pickling The crude steel is rolled into a steel coil through rough rolling and continuous rolling, the steel coil is cooled for 72-96 hours, then annealed at 1100-1200°C, then the steel coil is pretreated by shot blasting with stainless steel shots and pickling with a pickling solution to obtain a stainless steel coil; S3: Rolling and annealing treatment The stainless steel coil is rolled through finish rolling, then high-temperature annealing treatment is performed at 1080-1150°C, and the anti-aging stainless steel material is obtained after cooling to room temperature of 23-25°C.

2. The age-resistant stainless steel material according to claim 1, characterized in that, The pickling of step S2 specifically includes the following steps: The crude steel is rolled into a steel coil through rough rolling and continuous rolling, the steel coil is cooled for 72-96 hours, then annealed at 1100-1200°C to obtain an annealed steel coil; Then, the annealed steel coil is pretreated by shot blasting with stainless steel shots through a shot blasting machine at a speed of 70-100 m / s, the diameter of the stainless steel shots is 0.3-0.6 mm, and a pretreated steel coil is obtained. Then, the pickling solution is added into the soaking tank, the pretreated steel coil is completely immersed in the soaking tank, and heated to 38-42℃, compressed air is introduced to stir the soaking tank, and after taking out, it is washed with flowing cold water for 2-3 times to obtain the stainless steel coil plate.

3. The age-resistant stainless steel material according to claim 1, wherein The specific preparation process of the purification slag ball in step S1 includes the following steps: The magnesium sand of 55-60% by weight, the alumina of 30-35% by weight and the silicon carbide of 5-10% by weight are mixed and ground, then passed through a 150 mesh sieve, then a foaming agent of 0.2-0.4% of the system mass is added, and 5-15mm small balls are made in a disc balling machine, and then sent into 1200-1300℃ for 10-20min to obtain the purification slag ball.

4. The age-resistant stainless steel material according to claim 2, wherein The specific preparation process of the pickling solution in step S2 includes the following steps: Deionized water is added into a container, a stirrer is started to stir at a speed of 100-120r / min, and ammonium persulfate is slowly added under stirring, so that the concentration of ammonium persulfate is 80-150g / L, and the stirring is continued until the ammonium persulfate is completely dissolved to obtain a colorless transparent solution; The stirring is kept, and the weighed citric acid and gluconic acid are sequentially added into the colorless transparent solution, so that the concentration of citric acid is 60-100g / L and the concentration of gluconic acid is 20-40g / L, and after completely dissolving, thiourea is added, and stirred until completely dissolved, so that the concentration of thiourea is 2-6g / L; Finally, 0.5-2g / L of surfactant is added, and the stirring is continued for 15-20 minutes, and then it is left to mature for 30-40 minutes to obtain the pickling solution.

5. The age-resistant stainless steel material according to claim 1, wherein The concentration of the sodium silicate solution is 35-40wt%.

6. The age-resistant stainless steel material according to claim 2, wherein When the compressed air is introduced to stir the soaking tank, the pressure of the compressed air is 0.1-0.3MPa, the air flow velocity is 0.01-0.05m / s, and the stirring time is 2-4 minutes.

7. The age-resistant stainless steel material according to claim 3, wherein The foaming agent is calcium carbonate or magnesium carbonate, and the particle size is 2-5μm.

8. The age-resistant stainless steel material according to claim 4, wherein The surfactant is sodium dodecyl sulfate.

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