CN112981219A - Preparation method of ferrite antibacterial stainless steel by precision investment casting - Google Patents
Preparation method of ferrite antibacterial stainless steel by precision investment casting Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
- C22C33/06—Making ferrous alloys by melting using master alloys
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/02—Sand moulds or like moulds for shaped castings
- B22C9/04—Use of lost patterns
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
Abstract
A preparation method of an investment precision casting ferrite antibacterial stainless steel comprises the following components: c is less than or equal to 0.03 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 2.0 percent; p is less than or equal to 0.05 percent; s is less than or equal to 0.05 percent; 24.0-26.0% of Cr; 2.0-4.0% of Ni; 1.8-2.5% of Cu; 0.18-0.24% of Nb; the balance of Fe and impurities. The preparation process comprises the following steps: smelting → precision investment casting → solution treatment → antibacterial annealing. 1.8-2.5% of copper is added into cast Cr25 ferrite stainless steel, and through appropriate solid solution treatment and antibacterial annealing heat treatment, 50-500 nm copper-rich phases are uniformly distributed on a ferrite matrix, so that a passivation film of the stainless steel can be broken through, the casting is endowed with antibacterial performance, and the antibacterial rate of Escherichia coli is as high as 99%. The cast ferrite antibacterial stainless steel prepared by the invention has excellent corrosion resistance. And the antibacterial agent has lasting antibacterial performance and wide antibacterial range, and can be used for producing precision casting products such as high-end cast stainless steel water taps, door handles and the like.
Description
Technical Field
The invention relates to the technical field of ferrite stainless steel materials, in particular to an investment precision casting ferrite antibacterial stainless steel and a preparation method thereof.
Background
In view of escherichia coli and staphylococcus aureus which are increasingly abused and enhanced in drug resistance, scientists at home and abroad widely carry out research on antibacterial stainless steel, and the antibacterial stainless steel integrally generates strong, broad-spectrum and durable antibacterial function by adding a proper amount of antibacterial metal elements such as copper (Cu), silver (Ag) and the like into the existing stainless steel material and carrying out special heat treatment. Among various antibacterial stainless steels, the copper-containing ferrite antibacterial stainless steel has the advantages of obvious price advantage, excellent antibacterial property, heat resistance and atmospheric corrosion resistance. The antibacterial stainless steel is mainly applied to medical appliances, edible appliances and the like which are rich in Cl-And is in direct contact with the human body. The antibacterial property and safety of the antibacterial stainless steel are confirmed, the ingestion amount of Cu required by a human body is 2-6 mg per day, the insufficient ingestion can influence the synthesis of hemoglobin, so as to cause anemia or hypoevolutism, and when the ingestion amount is too much, Cu can be deposited in central nerves and various organs, so that various diseases can be caused. Since the dissolution concentration of the antibacterial stainless steel in water is far lower than the lower limit of the amount of Cu ions needed to be absorbed by a human body, excessive Cu absorption caused by the use of the antibacterial stainless steel can be avoided. Furthermore, Cu2+The growth of beneficial bacteria is not influenced while the escherichia coli is killed, and the bacterial cell membrane is not damaged. The detection of national drug and biological product tests shows that the antibacterial stainless steel completely meets the national toxicity and human body safety standards for medical materials.
Under the background that the steel productivity is seriously surplus and the homogenization competition is fierce in China at present, the functional requirement of high-quality special stainless steel is higher and higher, but the Cu-containing antibacterial stainless steel still has more problems in the aspects of obdurability, corrosion resistance, antibacterial property and the like, and can not meet the industrial requirement. At present, various large steel plants in China mainly concentrate on developing stainless steel rolled materials, but in life, a plurality of appliances need to be produced by casting, such as water taps, door handles and the like. In the production process, the antibacterial stainless steel contains more copper elements, so that copper is enriched on the surface of the material during high-temperature heat preservation before hot working, part of the copper falls off along with oxide scale to cause copper loss, and the rest copper is particularly easy to cause copper brittleness in the hot working process, but the problem does not exist in a cast part.
Meanwhile, since the ferritic stainless steel uses little or no noble metal nickel, the cost of the ferritic stainless steel is low. Therefore, the existing commercial copper-containing ferritic antibacterial stainless steel is usually prepared by adding Cu into ferritic stainless steel and matching with the production process thereof, so that a copper-rich phase precipitated on a ferritic matrix can be obtained and has bactericidal performance. And the antibacterial phase is dispersed on the surface and inside of the stainless steel, so that the antibacterial function of the material cannot be lost due to abrasion. However, the carbon content of the ferrite antibacterial stainless steel is generally 0.03-0.05, the carbon content is high, a large amount of carbide exists on a matrix, the corrosion resistance is reduced, and the requirements of industries such as kitchens, bathrooms, medicines and the like on the corrosion resistance of the stainless steel cannot be met.
The faucet is a necessity for people to live, and is required to be used by every family every day, and is safe, reliable, durable and beautiful in appearance. The tap appeared in the 16 th century at the earliest, and was cast with bronze, and its main function was to control the water outlet switch of the water pipe and the water flow. Early faucets were screw-lift, and most of them were ceramic cartridge faucets on the market, and the screw-lift was essentially eliminated. Generally, the content of lead in copper materials and copper faucet castings is 4% -8%, if the faucet is not used for a long time, green patina is generated on the inner wall, and harmful substances such as lead existing in the faucet can be released into tap water. Drinking water with too high lead content can cause lead poisoning, which not only can affect the intelligence growth of drinkers, but also can seriously affect the health, and has greater influence on children. Scientific data indicates that severe lead contamination often endangers human reproductive ability, renal function, and nervous system.
The stainless steel water tap is a tap manufactured by using a stainless steel material, and the stainless steel is a healthy material, does not contain lead, is acid-resistant, alkali-resistant and corrosion-resistant, does not release harmful substances, and can ensure the health and sanitation of human bodies. Some manufacturers have used high-quality 304 stainless steel to make faucets, and faucets made of high-quality stainless steel have the characteristics of no lead, acid resistance, alkali resistance, corrosion resistance, no harmful substance release and no pollution to tap water sources compared with pure copper faucets, and stainless steel faucets do not need to be electroplated, are not easy to rust, have hardness and toughness more than two times higher than those of copper products, and are very convenient to clean. With the gradual maturity of stainless steel faucet manufacturing process in China, the stainless steel faucet has a great promotion no matter in production or grade, and although the share of the stainless steel faucet in the domestic market is smaller, the stainless steel faucet is more and more favored by consumers in recent years due to the characteristics of health, environmental protection, durability and the like, and gradually seizes the market share of the copper faucet, and the stainless steel faucet has become the development trend of the bathroom industry.
The door handle is also a necessity of daily life, is a door accessory which cannot be ignored or lacked, and has both decoration and functionality. The door handle is made of ceramic, solid wood, metal, glass, crystal, plastic, alloy and the like according to the material. The stainless steel door handle has obvious advantages, can not rust, has smooth and bright appearance, has changeable appearance design, is simple, fashionable and elegant, is more and more used in modern life, is produced by precision investment casting and is made of austenitic stainless steel.
In the public field, the reports that the water tap or the door handle is adhered with bacteria are frequently found, the public health of people is seriously affected, and particularly during the outbreak of the bacterial or viral epidemic situation, the development of the water tap or the door handle with the antibacterial effect is a very realistic work.
Based on the background, the invention researches and develops the ferrite antibacterial stainless steel by investment casting, a certain Cu element is added into the ferrite stainless steel, a copper-rich phase with the thickness of 50-500 nanometers is uniformly distributed on a ferrite matrix through a proper preparation process, particularly solid solution and annealing heat treatment, copper ions can be released by utilizing the copper-rich phase, the antibacterial effect is realized, the antibacterial rate to escherichia coli is up to 99%, and the antibacterial performance cannot disappear along with the corrosion and abrasion of the surface of a material because the copper-rich phase is uniformly distributed. The copper-containing ferritic stainless steel with the antibacterial effect is obtained through reasonable component design and preparation process control, and can be used for producing precision casting products such as high-end cast stainless steel water taps, door handles and the like. Can reduce the problem of bacterial infection caused by the domestic water faucet.
Disclosure of Invention
The invention aims to provide a ferrite antibacterial stainless steel cast by precision investment and a preparation method thereof. By adding a certain content of copper element and matching with proper solid solution and antibacterial annealing treatment, a copper-rich phase with the size of 50-500 nanometers uniformly distributed on a ferrite matrix is obtained, so that the material has an antibacterial function, and the copper-rich phase is uniformly distributed, so that when the surface material is consumed due to corrosion or abrasion, the copper-rich phase is still distributed inside the material, and the material still has the same antibacterial effect. When the alloy is designed, firstly, the good antibacterial performance is considered, meanwhile, the corrosion resistance and the process performance are fully considered, the Cr25 type ferritic stainless steel is adopted, according to the n/8 rule, not only can a compact passive film be formed, but also a high electrode potential can be obtained, the alloy has good corrosion resistance, and in order to prevent intergranular corrosion caused by forming a chromium-poor area due to the generation of chromium carbide on a crystal boundary, a proper amount of strong carbide forming element Nb is added to react with carbon in the steel to generate niobium carbide; the addition of a proper amount of Ni element can improve the electrode potential of stainless steel on one hand, and can reduce copper segregation in the solidification process on the other hand, improve the high-temperature thermoplasticity of the alloy, prevent the generation of hot cracks and reduce the rejection rate of castings.
A preparation method of an investment precision casting ferrite antibacterial stainless steel is characterized by comprising the following steps: the chemical components by weight percentage are as follows: c is less than or equal to 0.03 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 2.0 percent; p is less than or equal to 0.05 percent; s is less than or equal to 0.05 percent; 24.0-26.0% of Cr; 2.0-4.0% of Nis; 1.8-2.5% of Cu; 0.18-0.24% of Nb; the balance of Fe and impurities; the preparation process comprises the following steps: smelting → precision investment casting → solution treatment → antibacterial annealing.
The preparation method of the ferrite antibacterial stainless steel by investment casting is characterized by comprising the following specific preparation steps
(1) Smelting: smelting in a vacuum induction furnace or an electric arc furnace;
(2) precision investment casting: casting the smelted molten steel into a precision casting shell to obtain a precision casting with accurate size and low surface roughness;
(3) solution treatment: heating the precision casting to 1050 ℃, preserving heat for a period of time to enable alloy elements to be uniformly diffused, and rapidly cooling to form a single ferrite structure;
(4) and (3) antibacterial annealing: heating the solution-treated precision casting to 800 +/-20 ℃, preserving the temperature for 3-4h, then air-cooling, and uniformly precipitating a copper-rich phase of 50-500 nm on a ferrite matrix to ensure that good antibacterial performance is obtained.
Furthermore, the chemical composition contains 1.8-2.5 wt% of Cu; through solution treatment at 1050 ℃ and antibacterial annealing treatment at 800 +/-20 ℃ for 3-4h, a copper-rich phase of 50-500 nm is uniformly precipitated on a ferrite matrix, the antibacterial property is good, the antibacterial rate of escherichia coli is up to 99%, and the copper-rich phase is uniformly distributed, so that the antibacterial effect is long-term effective and cannot disappear along with corrosion and abrasion of the surface of the material.
Furthermore, the chemical composition contains 24.0-26.0 wt% of Cr, belongs to Cr type ferritic stainless steel, can generate a compact passive film, and elements such as Cr, Ni and Cu are dissolved in the ferrite in a solid manner, so that the electrode potential is obviously improved,
furthermore, the chemical components of 0.18-0.24 wt% of Nb react with carbon in steel to generate niobium carbide, so that chromium carbide precipitation on grain boundaries is inhibited to form a chromium-poor area, and intergranular corrosion is avoided.
Furthermore, the chemical components contain 2.0-4.0 wt% of Ni, so that the electrode potential of the stainless steel can be improved, the corrosion resistance of the stainless steel can be improved, the high-temperature thermoplasticity of the alloy can be improved, the copper segregation in the solidification process can be reduced, the generation of hot cracks can be prevented, and the rejection rate of castings can be reduced.
Further, smelting and casting by adopting an induction furnace or an electric arc furnace, adding the raw materials of scrap steel, ferrochrome, electrolytic copper and nickel into a vacuum induction furnace or an electric arc furnace for smelting, heating the molten steel to 1600-1630 ℃, testing the components after the molten steel is molten down, testing the components to be qualified, inserting aluminum for deoxidation, and preparing for tapping and pouring; and (3) casting and molding by adopting an investment casting process, roasting the precision casting shell at a proper temperature, pouring into molten steel at the pouring temperature of 1550-1580 ℃, removing a pouring gate after cooling and molding, and cleaning and polishing to obtain a precision casting with accurate size and smooth surface.
Further, the solid solution treatment step is that the casting formed by the precision casting is heated to 1050 ℃ for solid solution treatment, and the heat preservation time at the solid solution temperature is determined according to the wall thickness of the casting: the thickness of the casting (mm)/25+3 hours, the alloy elements are fully and uniformly diffused, intercrystalline carbides or ferrite are eliminated, and then the water cooling is carried out to the room temperature, so as to obtain a single-phase ferrite structure with uniform components.
Further, the antibacterial annealing is to heat the precision casting subjected to the solution treatment to 800 +/-20 ℃ and preserve the temperature for 3-4h, perform antibacterial annealing heat treatment, and then perform furnace cooling to room temperature.
Furthermore, in the antibacterial annealing heat treatment process of keeping the temperature at 800 +/-20 ℃ for 3-4h, niobium in the steel reacts with carbon to generate niobium carbide, so that the precipitation of chromium carbide can be inhibited, and intergranular corrosion caused by the generation of a chromium-poor area can be prevented.
The key points of the technology of the invention are as follows:
1. the composition design of the alloy firstly ensures that good antibacterial performance is obtained, 1.8-2.5 wt% of Cu is added, the single-phase ferrite structure with uniform components is obtained by controlling the preparation process, particularly the heat treatment process, through solution treatment at 1050 ℃, interdendritic carbide and high-temperature delta ferrite in a solidification structure are eliminated, and through antibacterial annealing treatment at 800 +/-20 ℃, a copper-rich phase with 50-500 nanometers is uniformly precipitated on a ferrite matrix, so that good antibacterial performance is ensured.
2. The Cr25 type ferritic stainless steel is selected, contains 24.0-26.0 wt% of Cr, according to the n/8 rule, when the atomic ratio of Cr element is n/8, the electrode potential of the Fe-Cr alloy solid solution system is suddenly increased, when the chromium content reaches the atomic ratio of 1/8 and 2/8, the weight ratio of the corresponding chromium content is 12.5% and 25%, and the reason that the chromium stainless steel has high corrosion resistance in an oxidizing medium only when the chromium content exceeds the minimum value of 12%. The Cr25 type ferritic stainless steel of the invention can not only generate a compact passive film, but also dissolve about 25 wt% of Cr and certain elements such as Ni and Cu in the ferrite, thereby obviously improving the electrode potential and having excellent corrosion resistance.
3. The generation of the stainless steel intergranular corrosion is often related to a chromium-poor area, the solid solubility of carbon in austenite in the stainless steel is increased along with the increase of the temperature, and at 500-700 ℃, the average solid solubility of the carbon in the austenite in the 1Cr18Ni9 steel is not more than 0.01%, and the solid solubility of ferrite is lower. After the stainless steel is rapidly cooled by solution treatment, carbon in austenite or ferrite is in a supersaturated state. When the steel is heated within a sensitization temperature range (427-816 ℃), supersaturated carbon in austenite can be rapidly diffused to grain boundaries, the carbon consumes chromium around the grain boundaries on the grain boundaries, the carbon and the chromium form chromium carbides, and the diffusion speed of the chromium is too slow to be supplemented in time, so that a severe chromium-poor area is formed around the grain boundaries. The difference in electrochemical properties between the chromium-depleted region and the grains themselves allows an activated-passivated cell to be established with a large potential difference between the chromium-depleted region (anode) and the substrate in the passivated state (cathode). The small anode of the chromium-poor region and the large cathode of the substrate form a corrosion cell, which subjects the chromium-poor region to intergranular corrosion. In order to prevent a chromium-poor area from being generated, 0.18-0.24 wt% of Nb is added into the ferritic stainless steel, niobium is a strong carbide forming element, niobium carbide is preferentially generated, precipitation of chromium carbide on a grain boundary is prevented, and intergranular corrosion is avoided.
4. In order to prevent copper-containing stainless steel from generating cracks in the production process, metal nickel is added, when the atomic ratio of nickel to copper is more than or equal to 1, the generation of heat cracks of the copper-containing steel can be effectively prevented, and the nickel is added, so that the high-temperature plasticity of the stainless steel can be improved, the segregation of copper can be reduced, the electrode potential can be improved, and the corrosion resistance of the stainless steel can be improved. The ferritic stainless steel of the present invention contains 3.0 to 4.0 wt% of Ni.
5. After the cast ferrite antibacterial stainless steel is subjected to solution treatment and antibacterial annealing, a large number of rod-shaped copper-rich phases are uniformly distributed in the stainless steel structure, the grain size of the copper-rich phases is 50-500 nm, a passive film of the stainless steel can be broken through, and good antibacterial performance is ensured. And because the copper-rich phase is uniformly distributed, the antibacterial property can not disappear along with the corrosion and abrasion of the surface of the material.
The cast ferrite antibacterial stainless steel can be used for manufacturing water faucets. The tap made of the cast ferrite antibacterial stainless steel can reduce the problem of bacterial infection caused by a domestic tap.
The invention has the advantages of
The invention relates to copper-containing low-carbon precision investment casting ferrite antibacterial stainless steel. (1) Through solution treatment, alloy elements are uniformly diffused and rapidly cooled to form a single ferrite structure; (2) through antibacterial annealing treatment, uniform and large enough copper is separated out from the interior of the casting plate, so that the copper protrudes out of the passivation film on the surface of the stainless steel enough to be in contact with the external environment, and 99% of escherichia coli can be killed in a humid environment; (3) because copper is precipitated and uniformly exists in the material, even if the surface is abraded in the using process, the excellent antibacterial performance can be ensured; (4) the addition of a proper amount of Nb reacts with carbon in steel to generate niobium carbide, thereby inhibiting chromium carbide precipitation on a crystal boundary to form a chromium-poor area, avoiding intergranular corrosion and improving the corrosion resistance; (5) by controlling the Ni content to be 2.0-4.0 wt%, the electrode potential of the stainless steel can be improved, the corrosion resistance of the stainless steel can be further improved, the high-temperature thermoplasticity of the alloy can be improved, the copper segregation in the solidification process can be reduced, the generation of hot cracks can be prevented, and the rejection rate of castings can be reduced; (6) the process flow is shortened, and the problem of hot brittleness caused by high copper content is avoided without a hot processing process; (7) the cast ferrite antibacterial stainless steel water faucet can reduce the problem of bacterial infection caused by a domestic water faucet.
The specific implementation mode is as follows:
in order to better explain the present invention and to facilitate the understanding of the technical solutions, the present invention is described in detail below, but the present invention is not limited thereto. According to the chemical composition range set by the method for casting the ferrite antibacterial stainless steel material, the smelted test steel is cast into a casting, and the chemical composition is shown in the table 3.
Table 3 main chemical composition (wt.%) of ferritic stainless steels of examples and comparative examples
Solution treatment: heating the precision casting to 1050 ℃, preserving heat for a certain time to enable alloy elements to be uniformly diffused, and rapidly cooling to form a single ferrite structure. The heat preservation time is determined according to the thickness of the casting: casting wall thickness (mm)/25+3 (hours).
An antibacterial annealing process comprises: heating the solution treated precision casting to 800 +/-20 ℃, preserving the temperature for 3-4h, and then air cooling.
The specific solution treatment process and antibacterial annealing process of the examples and comparative examples are shown in table 4.
Detection of antibacterial Properties
According to the relevant standards of' Japanese national industrial standard JIS Z2801-.
Table 4 shows the heat treatment process parameters and the antibacterial property test results of the examples and the comparative examples
Example 1
In the present embodiment, the ferritic antibacterial stainless steel solution treatment is: the temperature is 1050 ℃ and the time is 3h, and the antibacterial annealing process comprises the following steps: 800 ℃ for 3.5 h. According to the antibacterial detection method, the result is as follows:
antibacterial ratio against Escherichia coli: not less than 99.9%, and the antibacterial rate to staphylococcus aureus is as follows: not less than 99.9%;
example 2
In the present embodiment, the ferritic antibacterial stainless steel solution treatment is: the temperature is 1050 ℃ and the time is 3h, and the antibacterial annealing process comprises the following steps: 780 ℃ for 3.5 h. According to the antibacterial detection method, the result is as follows:
antibacterial ratio against Escherichia coli: more than or equal to 98.5 percent, and the antibacterial rate to staphylococcus aureus is as follows: more than or equal to 98.9 percent;
example 3
In the present embodiment, the ferritic antibacterial stainless steel solution treatment is: the temperature is 1050 ℃ and the time is 3h, and the antibacterial annealing process comprises the following steps: 820 ℃ for 3.5 h. According to the antibacterial detection method, the result is as follows:
antibacterial ratio against Escherichia coli: not less than 99.4%, and the antibacterial rate to staphylococcus aureus is as follows: not less than 99.8%;
example 4
In the present embodiment, the ferritic antibacterial stainless steel solution treatment is: the temperature is 1050 ℃ and the time is 3.5h, and the antibacterial annealing process comprises the following steps: 800 ℃ for 3 h. According to the antibacterial detection method, the result is as follows:
antibacterial ratio against Escherichia coli: not less than 99.9%, and the antibacterial rate to staphylococcus aureus is as follows: not less than 99.9%;
example 5
In the present embodiment, the ferritic antibacterial stainless steel solution treatment is: the temperature is 1050 ℃ and the time is 3.5h, and the antibacterial annealing process comprises the following steps: 800 ℃ for 3.5 h. According to the antibacterial detection method, the result is as follows:
antibacterial ratio against Escherichia coli: not less than 99.2%, and the antibacterial rate to staphylococcus aureus is as follows: not less than 99.9%;
example 6
In the present embodiment, the ferritic antibacterial stainless steel solution treatment is: the temperature is 1050 ℃ and the time is 3.5h, and the antibacterial annealing process comprises the following steps: 800 ℃ for 4 h. According to the antibacterial detection method, the result is as follows:
antibacterial ratio against Escherichia coli: not less than 99.9%, and the antibacterial rate to staphylococcus aureus is as follows: not less than 99.9%;
comparative example 1
In the present comparative example, the ferritic antibacterial stainless steel solution treatment was: the temperature is 1050 ℃ and the time is 3h, and the antibacterial annealing process comprises the following steps: 800 ℃ for 3.5 h. According to the antibacterial detection, the result is as follows:
antibacterial ratio against Escherichia coli: greater than or equal to 94 percent, and the antibacterial rate to staphylococcus aureus is as follows: none;
comparative example 2
In the present comparative example, the ferritic antibacterial stainless steel solution treatment was: the temperature is 1050 ℃ and the time is 3h, and the antibacterial annealing process comprises the following steps: 700 ℃ X3.5 h, 870 ℃ X3.5 h, 800 ℃ X0.5 h. According to the antibacterial detection method, the result is as follows:
the antibacterial rate to escherichia coli is respectively as follows: 35%, 55% and 70%, and the antibacterial rate to staphylococcus aureus is respectively as follows: 50%, 60%;
as can be seen from the results of Table 4, the investment precision cast ferritic antimicrobial stainless steels of examples 1-6 of the present invention all exhibited excellent antimicrobial properties. The key point of the cast ferrite antibacterial stainless steel for the faucet provided by the invention is that the antibacterial performance and the good corrosion resistance can be exerted by ensuring the addition of high-content Si and a proper amount of Nb and the heat treatment process (solution heat treatment and antibacterial annealing). Generally, a material having an antibacterial rate of more than 90% may be referred to as an antibacterial material. The antibacterial results of the examples on two kinds of bacteria show that the antibacterial stainless steel prepared by the invention has an antibacterial rate of more than 90%.
The Cu content has important influence on the antibacterial performance of the ferrite antibacterial stainless steel. Under the same heat treatment condition, when the added copper content is less, the amount of the precipitated effective copper-rich phase is relatively less, the antibacterial rate is relatively reduced, when the added Cu content is 1.5%, the antibacterial rate to escherichia coli is 94%, the requirement is met, but the antibacterial effect to staphylococcus aureus is not achieved (comparative example 1).
The antibacterial annealing treatment has important influence on the antibacterial performance of the ferrite antibacterial stainless steel. When the antibacterial annealing temperature is too low, although the content of the precipitated copper-rich phase is relatively high, most of the copper-rich phase exists in a spherical or ellipsoidal shape, and a small amount of the copper-rich phase exists in a rod shape with a small length-width ratio, so that the size of the copper-rich phase is not enough to obtain a high antibacterial ratio (comparative example 2-1). When the antibacterial annealing temperature is too high, the copper-rich phase is partially dissolved, so that the number of effective copper-rich phases precipitated is sharply reduced, and the antibacterial rate is sharply reduced (comparative example 2-2). When the antibacterial annealing time is too short, similar to the antibacterial annealing temperature which is too low, most precipitated phases exist in a spherical shape, some precipitated phases exist in an ellipsoidal shape, only a few precipitated phases exist in a rod shape with small length-width ratio, and the size of precipitated copper is not enough to protrude the passive film on the surface of the stainless steel to contact with the external environment to kill bacteria, so that the antibacterial rate is low (comparative examples 2-3). Good bactericidal effect is achieved only when the copper-rich phase grows to a sufficient size.
Claims (10)
1. A preparation method of an investment precision casting ferrite antibacterial stainless steel is characterized by comprising the following steps: the chemical components by weight percentage are as follows: c is less than or equal to 0.03 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 2.0 percent; p is less than or equal to 0.05 percent; s is less than or equal to 0.05 percent; 24.0-26.0% of Cr; 2.0-4.0% of Nis; 1.8-2.5% of Cu; 0.18-0.24% of Nb; the balance of Fe and impurities; the preparation process comprises the following steps: smelting → precision investment casting → solution treatment → antibacterial annealing.
2. The method for preparing an investment precision cast ferritic antibacterial stainless steel according to claim 1, characterized by comprising the following steps
(1) Smelting: smelting in a vacuum induction furnace or an electric arc furnace;
(2) precision investment casting: casting the smelted molten steel into a precision casting shell to obtain a precision casting with accurate size and low surface roughness;
(3) solution treatment: heating the precision casting to 1050 ℃, preserving heat for a period of time to enable alloy elements to be uniformly diffused, and rapidly cooling to form a single ferrite structure;
(4) and (3) antibacterial annealing: heating the solution-treated precision casting to 800 +/-20 ℃, preserving the temperature for 3-4h, then air-cooling, and uniformly precipitating a copper-rich phase of 50-500 nm on a ferrite matrix to ensure that good antibacterial performance is obtained.
3. The cast ferritic antibacterial stainless steel produced by the method as set forth in claim 1, characterized in that the chemical composition contains 1.8 to 2.5 wt% of Cu; through solution treatment at 1050 ℃ and antibacterial annealing treatment at 800 +/-20 ℃ for 3-4h, a copper-rich phase of 50-500 nm is uniformly precipitated on a ferrite matrix, the antibacterial property is good, the antibacterial rate of escherichia coli is up to 99%, and the copper-rich phase is uniformly distributed, so that the antibacterial effect is long-term effective and cannot disappear along with corrosion and abrasion of the surface of the material.
4. The cast ferritic antimicrobial stainless steel according to claim 1, wherein the chemical composition contains Cr 24.0 to 26.0 wt%, which is a Cr-type ferritic stainless steel, and the cast ferritic antimicrobial stainless steel can form a dense passive film, and the ferrite has Cr, Ni, Cu, and other elements dissolved in solid, thereby significantly increasing the electrode potential.
5. The cast ferritic antibacterial stainless steel prepared by the method as claimed in claim 1, characterized in that the chemical composition contains 0.18 to 0.24 wt% of Nb, which reacts with carbon in the steel to produce niobium carbide, which inhibits chromium carbide precipitation on grain boundaries to form chromium-poor regions, avoiding intergranular corrosion.
6. The cast ferrite antibacterial stainless steel prepared by the method of claim 1, wherein the chemical composition contains 2.0-4.0 wt% of Ni, which not only can improve the electrode potential of the stainless steel and further improve the corrosion resistance, but also can improve the high temperature thermoplasticity of the alloy, reduce the copper segregation during the solidification process, prevent the generation of hot cracks, and reduce the rejection rate of castings.
7. The cast ferrite antibacterial stainless steel prepared by the method of claim 1, wherein the smelting and casting step is smelting by using an induction furnace or an electric arc furnace, adding the raw materials of scrap steel, ferrochrome, electrolytic copper and nickel into a vacuum induction furnace or an electric arc furnace for smelting, heating the molten steel to 1600-1630 ℃, testing the components after the molten steel is completely melted, testing the components to be qualified, inserting aluminum for deoxidation, and preparing for tapping and pouring; and (3) casting and molding by adopting an investment casting process, roasting the precision casting shell at a proper temperature, pouring into molten steel at the pouring temperature of 1550-1580 ℃, removing a pouring gate after cooling and molding, and cleaning and polishing to obtain a precision casting with accurate size and smooth surface.
8. The cast ferritic antibacterial stainless steel according to the claim 1, characterized in that the solution treatment step is to heat the casting formed by the fine casting to 1050 ℃ for solution treatment, and the holding time at the solution temperature is determined according to the wall thickness of the casting: the thickness of the casting (mm)/25+3 hours, the alloy elements are fully and uniformly diffused, intercrystalline carbides or ferrite are eliminated, and then the water cooling is carried out to the room temperature, so as to obtain a single-phase ferrite structure with uniform components.
9. A cast ferritic antibacterial stainless steel according to claim 1, characterized in that the antibacterial annealing is a solution treatment of the finished cast product by heating to 800 ± 20 ℃ for 3-4 hours, and then by antibacterial annealing heat treatment, and then by furnace cooling to room temperature.
10. The cast ferritic antibacterial stainless steel prepared by the method as claimed in claim 1, characterized in that niobium in the steel reacts with carbon during antibacterial annealing heat treatment at 800 ± 20 ℃ for 3-4h to produce niobium carbide, which can inhibit chromium carbide precipitation and prevent intergranular corrosion caused by chromium-poor region.
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| CN114317898A (en) * | 2021-12-24 | 2022-04-12 | 哈尔滨工程大学 | Method for improving wear resistance and corrosion resistance of ferritic stainless steel surface |
| CN115287416A (en) * | 2022-10-08 | 2022-11-04 | 太原科技大学 | Copper-containing stainless steel and surface modification method thereof |
| CN115852253A (en) * | 2022-11-24 | 2023-03-28 | 上海交通大学内蒙古研究院 | Stainless steel for casting and preparation method thereof |
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