Manufacturing process of multifunctional stainless steel

Abstract

The invention discloses a manufacturing process of multifunctional stainless steel, belongs to the technical field of stainless steel manufacturing, and aims to solve the problems that an existing nano reinforced phase is easy to agglomerate and difficult to uniformly disperse in molten steel, and the performance improvement effect of a material is influenced. By introducing the rare earth-intermetallic compound composite additive, rare earth elements yttrium and scandium can effectively refine grains, purify grain boundaries and improve the strength, toughness and corrosion resistance of the material, nickel trialuminide and a steel matrix are well combined, the dispersion strengthening effect is achieved, and meanwhile the high-temperature performance and thermal conductivity of the material are improved; vanadium and niobium elements are added to form fine carbides, the material is further strengthened, the various elements and the additive have a synergistic effect, parameters of all steps of the preparation process are clear, required equipment can be realized by properly modifying existing metal material processing equipment, the process stability is good, the production efficiency is high, and the production cost is low. The method is suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of stainless steel manufacturing, in particular to a manufacturing process of multifunctional stainless steel. Background Art

[0002] As a core basic material in the industrial field, stainless steel occupies a pivotal position in many industries such as construction engineering, machinery manufacturing, medical equipment, and food processing. With the continuous improvement of science and technology and the increasing diversification of market demand, the application scope of stainless steel is continuing to extend outward, and its potential value in emerging fields is also constantly being explored and expanded. The requirements for the comprehensive performance of stainless steel are becoming increasingly stringent, and it must simultaneously meet multiple requirements such as high strength, high corrosion resistance, good thermal conductivity and antibacterial properties.

[0003] However, existing technologies include methods of adding nano-reinforced phases to improve the performance of stainless steel, but these technologies still have limitations. Nano-reinforced phases are easy to agglomerate in molten steel and are difficult to disperse evenly, which affects the effect of improving material performance. Although the addition of some components can improve a single performance, it will have a negative impact on other performances, making it difficult to achieve synergistic optimization of multiple performances. At the same time, traditional preparation processes have limited effects in refining grains and improving surface properties, and cannot fully tap the potential of the material, making it difficult to meet the needs of modern high-end manufacturing for high-performance stainless steel materials.

[0004] Therefore, in order to solve such problems, we proposed a manufacturing process of multifunctional stainless steel. Summary of the Invention

[0005] The purpose of the present invention is to provide a manufacturing process for multifunctional stainless steel, aiming to solve the problem in the above-mentioned background technology that the nano-reinforced phase is easy to agglomerate in the steel liquid and is difficult to disperse evenly, which affects the effect of improving material performance.

[0006] In order to achieve the above object, the present invention provides the following technical solution: a manufacturing process of multifunctional stainless steel, comprising the following implementation steps:

[0007] S1: Raw material proportioning and pretreatment, prepare raw materials by mass percentage, and control the carbon content to be 0.03% to 0.07%, silicon 0.4% to 0.9%, manganese 1.0% to 1.6%, chromium 17% to 20%, nickel 9% to 12%, molybdenum 2.5% to 4.0%, copper 3.50% to 4.00%, vanadium 0.1% to 0.3%, niobium 0.05% to 0.15%, rare earth-intermetallic compound composite additive 0.05% to 0.2%, and the balance is iron;

[0008] S2: Vacuum induction melting and composite strengthening: the raw materials are melted in a vacuum induction melting furnace and kept warm, rare earth-intermetallic compound composite additives are added and electromagnetic stirring is performed, and then refining is performed;

[0009] S3: semi-solid extrusion molding, after refining, cooling to the solid-liquid two-phase region, and extrusion molding;

[0010] S4: double gradient heat treatment, the blank is subjected to two gradient heat treatments;

[0011] S5: Surface treatment: the plate is first micro-arc oxidized in an electrolyte containing sodium silicate to form a ceramic layer, and then a silver-copper alloy layer is chemically plated in a plating solution containing silver nitrate.

[0012] Furthermore, the preparation of the rare earth-intermetallic compound composite additive in S1 includes the following implementation steps:

[0013] S11: preparing yttrium and scandium in a mass ratio of 2:1, and preparing nickel aluminide in a mass ratio of 1:3;

[0014] S12: Place the above materials into a ball mill, set the ball mill speed to 300-400 r / min, and the ball milling time to 8-12 hours;

[0015] S13: After the ball milling is completed, a rare earth-intermetallic compound composite additive powder with an average particle size of 5-10 μm is obtained.

[0016] Furthermore, the vacuum induction melting and composite strengthening in S2 includes the following implementation steps:

[0017] S21: Add the prepared basic raw materials into the vacuum induction melting furnace and control the vacuum degree to no more than 1×10 -4 Pa, heat to 1560-1620℃ at a heating rate of 18-22℃ / min, and keep warm for 45-55 minutes after the raw materials are completely melted;

[0018] S22: Under argon protection, the rare earth-intermetallic compound composite additive powder prepared in step 1 is added to the molten steel through a special quantitative feeding device, and electromagnetic stirring is turned on at the same time, the stirring speed is controlled at 200-250 r / min, and stirring is continued for 35-45 minutes to ensure that the composite additive is fully and evenly dispersed in the molten steel;

[0019] S23: After the stirring is completed, the temperature of the molten steel is lowered to 1460-1500°C at a cooling rate of 6-10°C / min under argon protection, and a refining treatment is performed for 30-40 minutes to further remove impurities and gases and improve the purity of the molten steel.

[0020] Furthermore, the semi-solid extrusion molding in S3 includes the following implementation steps:

[0021] S31: Cooling the refined molten steel to a solid-liquid two-phase region temperature of 1420-1450° C.;

[0022] S32: quickly transferring the cooled molten steel to a semi-solid extrusion molding device;

[0023] S33: Under the conditions of 80-120 MPa pressure and 5-10 mm / s extrusion speed, the molten steel is extruded through a die of a specific shape to obtain a stainless steel billet with a dense structure and uniform composition.

[0024] Furthermore, the dual gradient heat treatment in S4 includes the following implementation steps:

[0025] S41: placing the stainless steel billet into a heating furnace, heating it to 980-1020°C at a heating rate of 12-15°C / min, and keeping it at that temperature for 1.5-2.5 hours;

[0026] S42: Place the blank in a salt bath furnace at 400-450°C for isothermal treatment for 2-3 hours to complete the first gradient heat treatment, obtain fine bainite structure, and improve material strength and toughness;

[0027] S43: The blank is heated again to 550-600°C, kept at this temperature for 1-2 hours, and then naturally cooled to room temperature in air to complete the second gradient heat treatment to precipitate dispersed carbides to enhance material properties.

[0028] Furthermore, the surface treatment in S5 includes the following implementation steps:

[0029] S51: Prepare an electrolyte, and configure a micro-arc oxidation electrolyte consisting of 15-20 g / L sodium silicate, 5-10 g / L sodium hydroxide, and 3-5 g / L glycerol;

[0030] S52: Micro-arc oxidation treatment: the stainless steel plate after the double gradient heat treatment is placed in the electrolyte of the micro-arc oxidation equipment, and treated at a voltage of 350-450V and a frequency of 500-800Hz for 15-25 minutes to form a ceramic layer with a porous structure on the surface of the plate to improve the surface hardness and corrosion resistance;

[0031] S53: Prepare a chemical plating solution consisting of 3-5 g / L silver nitrate, 2-4 g / L copper sulfate, 10-15 g / L sodium hypophosphite, and 15-20 g / L sodium citrate;

[0032] S54: Chemical plating treatment: placing the plate after micro-arc oxidation treatment into a chemical plating solution, treating it at a temperature of 50-60°C and a pH value of 8-9 for 30 to 40 minutes, and depositing a silver-copper alloy layer on the surface of the ceramic layer.

[0033] Furthermore, the electromagnetic stirring process in S22 needs to control the temperature fluctuation range of the molten steel to be ≤±15°C, and the stirring speed needs to be gradually reduced to 100-150r / min 5 minutes before the end of stirring. By optimizing the stirring process to reduce the eddy current generated by stirring, the agglomeration phenomenon of the rare earth-intermetallic compound composite additive is weakened.

[0034] Furthermore, the pH value of the chemical plating solution in S54 is adjusted by adding ammonia water and citric acid, and nitrogen gas needs to be continuously introduced for stirring during the plating process. The gas flow rate is controlled at 0.5 to 1 L / min to promote uniform deposition of the silver-copper alloy layer and obtain a dense plating layer with a surface roughness Ra ≤ 0.8 μm.

[0035] Furthermore, during the micro-arc oxidation treatment in S52, the electrolyte temperature needs to be controlled at 20-40°C, and the temperature is maintained stable through a circulating cooling system during the treatment process to avoid loosening of the ceramic layer structure due to excessive temperature, which affects the surface hardness and corrosion resistance.

[0036] Furthermore, the raw material ratio in S1 also includes 0.02% to 0.05% by mass of nitrogen, which is added in the form of chromium nitride and manganese nitride to solid solution strengthen the matrix and increase grain boundary strength, while inhibiting σ phase precipitation and improving the corrosion resistance and mechanical properties of the material.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. The present invention proposes a multifunctional stainless steel manufacturing process. By introducing a rare earth-intermetallic compound composite additive, the rare earth elements yttrium and scandium can effectively refine grains, purify grain boundaries, and improve the material's strength, toughness, and corrosion resistance. Nickel aluminide combines well with the steel matrix, exerting a dispersion strengthening effect, while also improving the material's high-temperature performance and thermal conductivity. In addition, the addition of vanadium and niobium forms fine carbides, further strengthening the material. The synergistic effect of multiple elements and additives achieves an overall performance improvement.

[0039] 2. The present invention proposes a manufacturing process for multifunctional stainless steel. The semi-solid extrusion molding process breaks the traditional molding method and performs processing in the solid-liquid two-phase region, effectively improving material tissue defects, refining grains, and increasing density. The dual-gradient heat treatment obtains bainite structure and dispersed carbides respectively through two treatments at different temperatures and times, achieving synergistic optimization of strength and toughness. The micro-arc oxidation-chemical plating composite surface treatment first forms a ceramic layer to improve hardness and corrosion resistance, and then deposits a silver-copper alloy layer to impart antibacterial properties. Compared with a single surface treatment method, the performance improvement is more significant.

[0040] 3. The present invention proposes a manufacturing process for multifunctional stainless steel. Through the above-mentioned innovative components and processes, the tensile strength, yield strength and Vickers hardness of the prepared stainless steel are improved, and its corrosion resistance and antibacterial properties far exceed those of traditional stainless steel materials. Secondly, the parameters of each step of the preparation process of the present invention are clear, and the required equipment can be appropriately modified on the basis of existing metal material processing equipment. The process has good process stability, high production efficiency, controllable costs, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a process flow chart of the present invention;

[0042] Figure 2 This is a flow chart of raw material ratio and pretreatment in the present invention;

[0043] Figure 3 This is a flow chart of vacuum induction melting and composite strengthening in the present invention;

[0044] Figure 4 This is a flow chart of semi-solid extrusion molding in the present invention;

[0045] Figure 5 This is a flow chart of the dual gradient heat treatment in the present invention;

[0046] Figure 6 Flow chart of surface treatment in the present invention. DETAILED DESCRIPTION

[0047] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 efforts are within the scope of protection of the present invention.

[0048] In order to solve the problem that the existing nano-reinforced phase is easy to agglomerate in the steel liquid and difficult to disperse evenly, which affects the effect of improving the material performance, please refer to Figures 1-6 , provide the following preferred technical solution, including the following implementation steps:

[0049] S1: Raw material proportioning and pretreatment, prepare raw materials by mass percentage, and control the carbon content to be 0.03% to 0.07%, silicon 0.4% to 0.9%, manganese 1.0% to 1.6%, chromium 17% to 20%, nickel 9% to 12%, molybdenum 2.5% to 4.0%, copper 3.50% to 4.00%, vanadium 0.1% to 0.3%, niobium 0.05% to 0.15%, rare earth-intermetallic compound composite additive 0.05% to 0.2%, and the balance is iron;

[0050] S2: Vacuum induction melting and composite strengthening: the raw materials are melted in a vacuum induction melting furnace and kept warm, rare earth-intermetallic compound composite additives are added and electromagnetic stirring is performed, and then refining is performed;

[0051] S3: semi-solid extrusion molding, after refining, cooling to the solid-liquid two-phase region, and extrusion molding;

[0052] S4: double gradient heat treatment, the blank is subjected to two gradient heat treatments;

[0053] S5: Surface treatment: the plate is first micro-arc oxidized in an electrolyte containing sodium silicate to form a ceramic layer, and then a silver-copper alloy layer is chemically plated in a plating solution containing silver nitrate.

[0054] Specifically, the carbon content is controlled at 0.03% to 0.07%, ensuring strength while avoiding a decrease in corrosion resistance due to excessive carbon content; silicon 0.4% to 0.9% and manganese 1.0% to 1.6% serve as deoxidizers and alloying elements. Silicon can improve the strength and hardness of steel, and manganese can improve the hot working properties of steel and strengthen the matrix; chromium 17% to 20% and nickel 9% to 12% are key elements for the corrosion resistance of stainless steel. Chromium forms a passivation film, and nickel stabilizes the austenite structure, improving corrosion resistance and toughness; molybdenum 2.5% to 4.0% further enhances resistance to pitting and crevice corrosion, especially in chloride environments. The effect is significant in the environment. 3.50% to 4.00% copper can be solid solution strengthened and precipitation strengthened in stainless steel, thereby improving corrosion resistance, processing performance and oxidation resistance. 0.1% to 0.3% vanadium and 0.05% to 0.15% niobium combine with carbon to form fine carbides. These carbides are dispersed in the steel and hinder dislocation movement through the precipitation strengthening mechanism, significantly improving the strength and hardness of the material. 0.02% to 0.05% nitrogen is added in the form of chromium nitride or manganese nitride and dissolved in the matrix to produce a solid solution strengthening effect, while increasing grain boundary strength, inhibiting the precipitation of harmful σ phase, and improving corrosion resistance and mechanical properties.

[0055] The preparation of the rare earth-intermetallic compound composite additive in S1 includes the following implementation steps:

[0056] S11: preparing yttrium and scandium in a mass ratio of 2:1, and preparing nickel aluminide in a mass ratio of 1:3;

[0057] S12: Place the above materials into a ball mill, set the ball mill speed to 300-400 r / min, and the ball milling time to 8-12 hours;

[0058] S13: After the ball milling is completed, a rare earth-intermetallic compound composite additive powder with an average particle size of 5-10 μm is obtained.

[0059] Specifically, yttrium and scandium, as rare earth elements, have extremely strong chemical activity. They can form high-melting-point compounds with impurities such as oxygen and sulfur in molten steel, thereby purifying the molten steel and reducing the weakening effect of impurities on grain boundaries. At the same time, rare earth elements are concentrated at the grain boundaries, reducing grain boundary energy, inhibiting grain growth, and playing a role in refining grains. Grain refinement can simultaneously improve the strength, toughness and corrosion resistance of the material. This is because the number of grain boundaries in the fine-grained structure increases, the effect of hindering dislocation movement is stronger, and the crack propagation path is more tortuous. Nickel trialuminide has good compatibility with the steel matrix. After being uniformly dispersed in the molten steel, it forms fine intermetallic compound particles, which play a dispersion strengthening role. These particles can exist stably at room temperature and high temperature, effectively hindering dislocation movement and improving the strength and hardness of the material. In addition, the addition of nickel trialuminide can also improve the high-temperature performance of the material, improve its oxidation resistance and creep resistance, and also have a certain effect on the thermal conductivity of the material. This is because the crystal structure of the intermetallic compound is conducive to heat conduction.

[0060] The vacuum induction melting and composite strengthening in S2 include the following implementation steps:

[0061] S21: Add the prepared basic raw materials into the vacuum induction melting furnace and control the vacuum degree to no more than 1×10 -4 Pa, heat to 1560-1620℃ at a heating rate of 18-22℃ / min, and keep warm for 45-55 minutes after the raw materials are completely melted;

[0062] S22: Under argon protection, the rare earth-intermetallic compound composite additive powder prepared in step 1 is added to the molten steel through a special quantitative feeding device, and electromagnetic stirring is turned on at the same time, the stirring speed is controlled at 200-250 r / min, and stirring is continued for 35-45 minutes to ensure that the composite additive is fully and evenly dispersed in the molten steel;

[0063] S23: After the stirring is completed, the temperature of the molten steel is lowered to 1460-1500°C at a cooling rate of 6-10°C / min under argon protection, and a refining treatment is performed for 30-40 minutes to further remove impurities and gases and improve the purity of the molten steel.

[0064] Specifically, when the vacuum degree is not higher than 1×10 -4Pa, which can reduce the contact of molten steel with oxygen, nitrogen and other gases in the air, reduce the content of gas impurities, and improve the purity of molten steel; control the heating rate to 18-22℃ / min and heat to 1560-1620℃ to ensure that the raw materials are fully melted and avoid coarse grains caused by overheating; keep warm for 45-55 minutes to make the molten steel composition uniform, add the composite additives, and then perform electromagnetic stirring under argon protection (200-250r / min, 35-45 minutes). The eddy current generated by the electromagnetic stirring makes the composite additive powder fully dispersed in the molten steel. The steel liquid is dispersed and agglomeration is reduced, while impurities in the steel liquid are promoted to float up, thereby further purifying the steel liquid. Before the end of stirring, the stirring speed is gradually reduced and the temperature fluctuation is controlled to be ≤±15°C, which can reduce the disturbance of the eddy current on the steel liquid, avoid the re-entry of inclusions caused by excessive stirring, and ensure the uniform distribution of the composite additives. The refining treatment (cooling to 1460-1500°C, 30-40 minutes) is carried out under argon protection. The gas and inclusions in the steel liquid are further removed by argon blowing and stirring, thereby improving the purity of the steel liquid and laying the foundation for subsequent forming and performance improvement.

[0065] The semi-solid extrusion molding in S3 includes the following implementation steps:

[0066] S31: Cooling the refined molten steel to a solid-liquid two-phase region temperature of 1420-1450° C.;

[0067] S32: quickly transferring the cooled molten steel to a semi-solid extrusion molding device;

[0068] S33: Under the conditions of 80-120MPa pressure and 5-10mm / s extrusion speed, the molten steel is extruded through a mold of a specific shape to obtain a stainless steel billet with a dense structure and uniform composition. In this process, the characteristics of the semi-solid molten steel fluidity combined with the solid support are utilized to effectively reduce defects such as pores and shrinkage, while promoting grain refinement and composition homogenization.

[0069] Specifically, the refined molten steel is cooled to the solid-liquid two-phase region of 1420-1450°C. At this time, the molten steel contains both solid crystals and liquid metal, which has both fluidity and certain support. Under a pressure of 80-120MPa and an extrusion speed of 5-10mm / s, it is extruded through a mold. In the semi-solid forming process, the solid crystals serve as the skeleton and the liquid metal fills the gaps. Under the action of pressure, the liquid metal is forced to flow and fill the microscopic pores, reducing defects such as pores and shrinkage. At the same time, the shear force and pressure in the extrusion process promote grain refinement, making the structure denser and the composition more uniform. This forming method breaks the limitations of traditional casting, effectively improves the structural defects of the material, and improves the density and mechanical properties.

[0070] The following table shows the experimental data of tensile strength, yield strength, Vickers hardness, corrosion resistance and antibacterial properties under different semi-solid extrusion molding pressures. The results are shown in Table 1;

[0071]

[0072] Table 1

[0073] The dual gradient heat treatment in S4 includes the following implementation steps:

[0074] S41: placing the stainless steel billet into a heating furnace, heating it to 980-1020°C at a heating rate of 12-15°C / min, and keeping it at that temperature for 1.5-2.5 hours;

[0075] S42: Place the blank in a salt bath furnace at 400-450°C for isothermal treatment for 2-3 hours to complete the first gradient heat treatment, obtain fine bainite structure, and improve material strength and toughness;

[0076] S43: The blank is heated again to 550-600°C, kept at this temperature for 1-2 hours, and then naturally cooled to room temperature in air to complete the second gradient heat treatment to precipitate dispersed carbides to enhance material properties.

[0077] Specifically, the first heat treatment (heating to 980-1020°C, holding for 1.5-2.5 hours, and isothermal treatment in a 400-450°C salt bath furnace for 2-3 hours) is performed by austenitizing and then isothermal treatment in the bainite transformation zone to obtain a fine bainite structure. The bainite structure has high strength and good toughness. This is because the ferrite laths and carbides in the bainite are evenly distributed, which can effectively hinder dislocation movement. At the same time, the residual austenite between the laths plays a role in coordinating deformation and improving the toughness of the material. The second heat treatment (heating to 550-600°C, holding for 1-2 hours, and air cooling) causes the supersaturated carbides in the steel to precipitate, forming dispersed fine carbide particles. These carbide particles further improve the strength and hardness of the material through the precipitation strengthening mechanism. At the same time, the tissue stress is released during the air cooling process, avoiding quenching cracking and ensuring the comprehensive mechanical properties of the material.

[0078] The following table shows the experimental data of tensile strength, yield strength, Vickers hardness, corrosion resistance and antibacterial properties at the first heat treatment and second heat treatment temperatures. The results are shown in Table 2 and Table 3.

[0079]

[0080] Table 2

[0081]

[0082] Table 3

[0083] The surface treatment in S5 includes the following implementation steps:

[0084] S51: Prepare an electrolyte, and configure a micro-arc oxidation electrolyte consisting of 15-20 g / L sodium silicate, 5-10 g / L sodium hydroxide, and 3-5 g / L glycerol;

[0085] S52: Micro-arc oxidation treatment: the stainless steel plate after the double gradient heat treatment is placed in the electrolyte of the micro-arc oxidation equipment, and treated at a voltage of 350-450V and a frequency of 500-800Hz for 15-25 minutes to form a ceramic layer with a porous structure on the surface of the plate to improve the surface hardness and corrosion resistance;

[0086] S53: Prepare a chemical plating solution consisting of 3-5 g / L silver nitrate, 2-4 g / L copper sulfate, 10-15 g / L sodium hypophosphite, and 15-20 g / L sodium citrate;

[0087] S54: Chemical plating treatment: placing the plate after micro-arc oxidation treatment into a chemical plating solution, treating it at a temperature of 50-60°C and a pH value of 8-9 for 30 to 40 minutes, and depositing a silver-copper alloy layer on the surface of the ceramic layer.

[0088] Specifically, an electrolyte composed of sodium silicate, sodium hydroxide and glycerol is prepared, and a stainless steel plate is placed therein, and micro-arc oxidation treatment is carried out at a voltage of 350-450V and a frequency of 500-800Hz. Under the action of the electric field, an electrolytic reaction occurs on the surface of the plate, generating a micro-arc discharge phenomenon, causing the surface metal to chemically react with oxygen, silicon and other elements in the electrolyte to generate a ceramic layer mainly composed of metal oxides (such as SiO2, Fe3O4, etc.). The ceramic layer has a porous structure and a moderate porosity. On the one hand, it improves the surface hardness (reaching HV1000 or above) and enhances wear resistance; on the other hand, the porous structure increases the surface roughness, providing a good bonding interface for subsequent chemical plating. At the same time, the ceramic layer itself has excellent corrosion resistance and can effectively protect the substrate from erosion by corrosive media. During the treatment process, the electrolyte temperature is controlled at 20-40°C, and the temperature is maintained stable by a circulating cooling system to avoid loosening the ceramic layer structure due to excessive temperature, which affects its performance.

[0089] Specifically, a chemical plating solution composed of silver nitrate, copper sulfate, sodium hypophosphite and sodium citrate is prepared. Under the conditions of 50-60°C and pH value of 8-9, the plate after micro-arc oxidation is immersed in the plating solution. Sodium hypophosphite is used as a reducing agent to reduce the silver ions and copper ions in the plating solution to metal elements, which are deposited on the surface of the ceramic layer to form a silver-copper alloy layer. Sodium citrate is used as a complexing agent to stabilize the metal ions in the plating solution, control the reduction reaction rate, and ensure uniform deposition of the alloy layer. The pH value is adjusted by adding ammonia water or citric acid to maintain the stability of the plating solution. -The copper alloy layer has good antibacterial properties. Silver ions can destroy the cell membrane and enzyme system of bacteria, inhibiting bacterial reproduction. Copper ions also have a certain antibacterial effect. The synergistic effect of the two gives the material an excellent antibacterial effect. At the same time, the alloy layer is tightly bonded to the ceramic layer, with a surface roughness of Ra ≤ 0.8μm, forming a dense protective layer, which further improves the corrosion resistance and wear resistance of the material. During the plating process, nitrogen gas (flow rate 0.5-1L / min) is continuously introduced for stirring, which can promote the uniform flow of the plating solution and ensure uniform deposition of the alloy layer.

[0090] The electromagnetic stirring process in S22 needs to control the temperature fluctuation range of the molten steel to ≤±15℃, and the stirring speed needs to be gradually reduced to 100-150r / min 5 minutes before the end of stirring. By optimizing the stirring process to reduce the eddy current generated by stirring, the agglomeration phenomenon of the rare earth-intermetallic compound composite additive is weakened.

[0091] The pH value of the chemical plating solution in S54 is adjusted by adding ammonia water and citric acid, and nitrogen gas needs to be continuously introduced for stirring during the plating process. The gas flow rate is controlled at 0.5 to 1 L / min to promote the uniform deposition of the silver-copper alloy layer and obtain a dense coating with a surface roughness Ra ≤ 0.8 μm.

[0092] During micro-arc oxidation treatment in S52, the electrolyte temperature needs to be controlled at 20-40°C, and the temperature is maintained stable through a circulating cooling system during the treatment process to avoid loosening the ceramic layer structure due to excessive temperature, which affects the surface hardness and corrosion resistance.

[0093] The following table shows the experimental data of tensile strength, yield strength, Vickers hardness, corrosion resistance and antibacterial properties at the first heat treatment and second heat treatment temperatures. The results are shown in Table 2 and Table 3.

[0094]

[0095]

[0096] Table 4

[0097] The raw material ratio in S1 also includes nitrogen with a mass percentage of 0.02% to 0.05%. The nitrogen is added in the form of chromium nitride and manganese nitride to strengthen the matrix and increase the grain boundary strength, while inhibiting the precipitation of σ phase and improving the corrosion resistance and mechanical properties of the material.

[0098] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements that are inherent to such process, method, article, or apparatus.

[0099] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A manufacturing process for multifunctional stainless steel, characterized in that: The implementation steps include: S1: Raw material proportioning and pretreatment, prepare raw materials by mass percentage, and control the carbon content to be 0.03% to 0.07%, silicon 0.4% to 0.9%, manganese 1.0% to 1.6%, chromium 17% to 20%, nickel 9% to 12%, molybdenum 2.5% to 4.0%, copper 3.50% to 4.00%, vanadium 0.1% to 0.3%, niobium 0.05% to 0.15%, rare earth-intermetallic compound composite additive 0.05% to 0.2%, and the balance is iron; S2: Vacuum induction melting and composite strengthening: the raw materials are melted in a vacuum induction melting furnace and kept warm, rare earth-intermetallic compound composite additives are added and electromagnetic stirring is performed, and then refining is performed; S3: semi-solid extrusion molding, after refining, cooling to the solid-liquid two-phase region, and extrusion molding; S4: double gradient heat treatment, the blank is subjected to two gradient heat treatments; S5: Surface treatment: the plate is first micro-arc oxidized in an electrolyte containing sodium silicate to form a ceramic layer, and then a silver-copper alloy layer is chemically plated in a plating solution containing silver nitrate.

2. The manufacturing process of multifunctional stainless steel according to claim 1, characterized in that: The preparation of the rare earth-intermetallic compound composite additive in S1 includes the following implementation steps: S11: preparing yttrium and scandium in a mass ratio of 2:1, and preparing nickel aluminide in a mass ratio of 1:3; S12: Place the above materials into a ball mill, set the ball mill speed to 300-400 r / min, and the ball milling time to 8-12 hours; S13: After the ball milling is completed, a rare earth-intermetallic compound composite additive powder with an average particle size of 5-10 μm is obtained.

3. The manufacturing process of multifunctional stainless steel according to claim 1, characterized in that: The vacuum induction melting and composite strengthening in S2 include the following implementation steps: S21: Add the prepared basic raw materials into the vacuum induction melting furnace and control the vacuum degree to no more than 1×10 -4 Pa, heat to 1560-1620℃ at a heating rate of 18-22℃ / min, and keep warm for 45-55 minutes after the raw materials are completely melted; S22: Under argon protection, the rare earth-intermetallic compound composite additive powder prepared in step 1 is added to the molten steel through a special quantitative feeding device, and electromagnetic stirring is turned on at the same time, the stirring speed is controlled at 200-250 r / min, and stirring is continued for 35-45 minutes to ensure that the composite additive is fully and evenly dispersed in the molten steel; S23: After the stirring is completed, the temperature of the molten steel is lowered to 1460-1500°C at a cooling rate of 6-10°C / min under argon protection, and a refining treatment is performed for 30-40 minutes to further remove impurities and gases and improve the purity of the molten steel.

4. The manufacturing process of multifunctional stainless steel according to claim 1, characterized in that: The semi-solid extrusion molding in S3 includes the following implementation steps: S31: Cooling the refined molten steel to a solid-liquid two-phase region temperature of 1420-1450° C.; S32: quickly transferring the cooled molten steel to a semi-solid extrusion molding device; S33: Under the conditions of 80-120 MPa pressure and 5-10 mm / s extrusion speed, the molten steel is extruded through a die of a specific shape to obtain a stainless steel billet with a dense structure and uniform composition.

5. The manufacturing process of multifunctional stainless steel according to claim 1, characterized in that: The dual gradient heat treatment in S4 includes the following implementation steps: S41: placing the stainless steel billet into a heating furnace, heating it to 980-1020°C at a heating rate of 12-15°C / min, and keeping it at that temperature for 1.5-2.5 hours; S42: Place the blank in a salt bath furnace at 400-450°C for isothermal treatment for 2-3 hours to complete the first gradient heat treatment, obtain fine bainite structure, and improve material strength and toughness; S43: The blank is heated again to 550-600°C, kept at this temperature for 1-2 hours, and then naturally cooled to room temperature in air to complete the second gradient heat treatment to precipitate dispersed carbides to enhance material properties.

6. The manufacturing process of multifunctional stainless steel according to claim 1, characterized in that: The surface treatment in S5 includes the following steps: S51: Prepare an electrolyte, and configure a micro-arc oxidation electrolyte consisting of 15-20 g / L sodium silicate, 5-10 g / L sodium hydroxide, and 3-5 g / L glycerol; S52: Micro-arc oxidation treatment: the stainless steel plate after the double gradient heat treatment is placed in the electrolyte of the micro-arc oxidation equipment, and treated at a voltage of 350-450V and a frequency of 500-800Hz for 15-25 minutes to form a ceramic layer with a porous structure on the surface of the plate to improve the surface hardness and corrosion resistance; S53: Prepare a chemical plating solution consisting of 3-5 g / L silver nitrate, 2-4 g / L copper sulfate, 10-15 g / L sodium hypophosphite, and 15-20 g / L sodium citrate; S54: Chemical plating treatment: placing the plate after micro-arc oxidation treatment into a chemical plating solution, treating it at a temperature of 50-60°C and a pH value of 8-9 for 30 to 40 minutes, and depositing a silver-copper alloy layer on the surface of the ceramic layer.

7. The manufacturing process of multifunctional stainless steel according to claim 3, characterized in that: The electromagnetic stirring process in S22 needs to control the temperature fluctuation range of the molten steel to be ≤±15°C, and the stirring speed needs to be gradually reduced to 100-150r / min 5 minutes before the end of stirring.

8. The manufacturing process of multifunctional stainless steel according to claim 6, characterized in that: The pH value of the chemical plating solution in S54 is adjusted by adding ammonia water and citric acid, and nitrogen gas needs to be continuously introduced for stirring during the plating process, and the gas flow rate is controlled at 0.5 to 1 L / min.

9. The manufacturing process of multifunctional stainless steel according to claim 6, characterized in that: During the micro-arc oxidation treatment in S52, the electrolyte temperature needs to be controlled at 20-40° C., and the temperature is maintained stable through a circulating cooling system during the treatment process.

10. The manufacturing process of multifunctional stainless steel according to claim 1, characterized in that: The raw material ratio in S1 further includes nitrogen element with a mass percentage of 0.02% to 0.05%, and the nitrogen element is added in the form of chromium nitride and manganese nitride.

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