Antibacterial extra-super duplex stainless steel and preparation method thereof

Abstract

The invention relates to antibacterial extra-super duplex stainless steel and a preparation method thereof. The antibacterial extra-super duplex stainless steel comprises the following components in percentage by mass: less than or equal to 0.03% of C, less than or equal to 0.65% of Si, less than or equal to 1% of Mn, less than or equal to 0.035% of P, less than or equal to 0.03% of S, 6%-8% of Ni, 30%-34% of Cr, 3%-5% of Mo, 0.4%-0.5% of N, 0.15%-0.25% of Ce, 0%-3.5% of Cu, 0%-0.15% of Ag, 0.05%-0.2% of Ru, 0.05%-0.15% of Ti and the balance of Fe and inevitable impurities. The antibacterial extra-super duplex stainless steel is prepared by adding trace Cu, Ce, Ag, Ru and Ti into the extra-super duplex stainless steel, an as-cast material is subjected to hot forging treatment, and after solid solution, cold rolling and high-temperature short-time annealing treatment are performed, so that the antibacterial extra-super duplex stainless steel has a lamellar structure, and the phase ratio of austenite to ferrite is about 3: 7. The material shows more excellent tensile strength, corrosion resistance and good antibacterial property, and is suitable for a more stringent application environment.

Description

Technical Field

[0001] The invention belongs to the technical field of duplex stainless steel and relates to an antibacterial super duplex stainless steel and a preparation method thereof. Background Art

[0002] At present, the country is in a stage of rapid development, and infrastructure construction has been improved and reached a high level. However, engineering materials often face the problem of microbial adhesion corrosion during service, which often leads to a series of serious consequences such as leakage, damage and failure. Therefore, the research on corrosion and protection of engineering materials during service will become the focus of future work. In addition, the spread of harmful microorganisms in daily life is also a major hidden danger, which can cause various diseases, which makes people put forward the demand for antibacterial and antibacterial products such as kitchen utensils, public facilities, and medical devices.

[0003] Traditionally, people use bactericides to achieve antibacterial and antibacterial effects, but these substances usually have toxic side effects and are not environmentally friendly. In this context, antibacterial metal materials have attracted widespread attention as a new type of functional material. By adding an appropriate amount of antibacterial elements to the alloy matrix and combining it with specific process treatment, this material can maintain excellent comprehensive mechanical properties and corrosion resistance while effectively inhibiting the attachment and growth of bacteria on the material surface for a long time.

[0004] In the research of antibacterial metal materials, antibacterial stainless steel occupies a dominant position. Compared with other antibacterial metals, antibacterial stainless steel has significant advantages in comprehensive performance, corrosion resistance and antibacterial performance. However, most of the current research focuses on austenite, ferrite and martensite single-phase stainless steels, while there are few reports on antibacterial duplex stainless steels, especially antibacterial super duplex stainless steels with the addition of rare earth elements and antibacterial elements Cu and Ag.

[0005] Duplex stainless steel refers to a type of stainless steel whose solid solution structure is composed of two phases, ferrite and austenite. It combines the advantages of ferritic stainless steel and austenitic stainless steel, and has excellent welding performance, mechanical strength and corrosion resistance. Therefore, it is widely used in fields that require high corrosion resistance and high mechanical properties, such as chemical industry, ocean, oil and gas. However, duplex stainless steel itself does not have antibacterial properties, and when there are microorganisms in its application environment, it will cause serious corrosion damage to the material. Therefore, it is particularly important to develop duplex stainless steel materials with anti-microbial adhesion and antibacterial properties for the specific environment of bacterial microorganisms.

[0006] Super duplex stainless steel is a type of duplex stainless steel with a pitting resistance equivalent (PREN) close to 50. By further optimizing the composition design on the basis of traditional duplex stainless steel, the content of Cr, Mo and N is significantly increased, thereby enhancing its strength and corrosion resistance. At the same time, the composition ratio of other elements is appropriately adjusted to maintain the balance of performance. Adding a certain amount of antibacterial elements, such as Cu, Ag, Ce, etc., to super duplex stainless steel can give it antibacterial properties. These antibacterial elements not only have antibacterial effects, but also affect other properties of duplex stainless steel. For example, the addition of Ce can purify the molten steel, improve the oxidation resistance, high temperature strength and creep strength of the steel, and increase the corrosion resistance of the material; Cu is the main antibacterial and corrosion resistant element, which can provide antibacterial properties and improve the performance of the passivation film at the same time; Ag can significantly enhance the antibacterial effect at low concentrations and optimize the density and stability of the passivation film. Summary of the invention

[0007] The present invention aims to provide an antibacterial super duplex stainless steel and a preparation method thereof. By adding trace amounts of Ce, Cu, Ag, Ru and Ti to super duplex stainless steel and optimizing the deformation heat treatment process, an innovative material that achieves a multifunctional balance between antibacterial, corrosion-resistant and mechanical properties is provided, achieving a multifunctional balance of antibacterial, corrosion-resistant and mechanical properties. The antibacterial rate of the antibacterial super duplex stainless steel against Escherichia coli and Staphylococcus aureus exceeds 97%, showing an ideal antibacterial effect, and its preparation and processing technology is simple and the effect is significant, so it is particularly suitable for high-demand application environments, such as the demand for sterility in the field of medical devices, the dual demand for antibacterial and corrosion resistance in marine engineering, and the challenge of high strength of energy equipment.

[0008] To achieve the above object, the present invention adopts the following technical solution: The first aspect of the present invention provides an antibacterial super duplex stainless steel, wherein the composition and mass percentage of the antibacterial super duplex stainless steel are: C≤0.03%, Si≤0.65%, Mn≤1%, P≤0.035%, S≤0.03%, Ni: 6%-8%, Cr: 30%-34%, Mo: 3%-5%, N: 0.4%-0.5%, Ce: 0.15%-0.25%, Cu: 0%-3.5%, Ag: 0%-0.15%, Ru: 0.05%-0.2%, Ti: 0.05%-0.15%, and the balance is Fe and unavoidable impurities.

[0009] Preferably, the composition and mass percentage of the above-mentioned antibacterial super duplex stainless steel are: C: 0.02%, Si: 0.65%, Mn: 0.89%, S: 0.03%, P: 0.02%, Cr: 32.00%, Ni: 7.53%, Mo: 4.74%, N: 0.49%, Ce: 0.17%, Ru: 0.1%, Ti: 0.08%, and the balance is Fe and unavoidable impurities.

[0010] Preferably, the composition and mass percentage of the above-mentioned antibacterial super duplex stainless steel are: C: 0.02%, Si: 0.56%, Mn: 0.98%, S: 0.03%, P: 0.02%, Cr: 31.08%, Ni: 7.94%, Mo: 4.8%, N: 0.45%, Ce: 0.23%, Cu: 2.58%, Ru: 0.12%, Ti: 0.11%, and the balance is Fe and unavoidable impurities.

[0011] Preferably, the composition and mass percentage of the above-mentioned antibacterial super duplex stainless steel are: C: 0.02%, Si: 0.47%, Mn: 0.97%, S: 0.03%, P: 0.02%, Cr: 31.16%, Ni: 7.64%, Mo: 4.32%, N: 0.48%, Ce: 0.2%, Cu: 3.05%, Ag: 0.11%, Ru: 0.13%, Ti: 0.12%, and the balance is Fe and unavoidable impurities.

[0012] Furthermore, the above-mentioned antibacterial super duplex stainless steel has a lamellar structure, an austenite content of 26.4% to 28.5%, a ferrite content of 71.5% to 72.6%, a tensile strength of 1174 to 1289 MPa, an elongation of 30.5% to 33.4%, and an antibacterial rate greater than 97%.

[0013] The second aspect of the present invention provides a method for preparing the above-mentioned antibacterial super duplex stainless steel, comprising the following steps: S1: According to the above ingredients and mass percentages, the steel is melted and cast in a vacuum induction furnace to obtain a steel ingot; S2: The steel ingot is subjected to deformation heat treatment to obtain antibacterial super duplex stainless steel.

[0014] Furthermore, the above smelting includes melting treatment and refining treatment. The temperature of the melting treatment is 1620-1650°C and the time is 30-40 minutes. The temperature of the refining treatment is 1600-1620°C and the time is 10 minutes. The casting temperature is 1520-1570°C and the time is controlled within 30 seconds.

[0015] Furthermore, the method of the above-mentioned deformation heat treatment is: the steel ingot is kept at 1250°C for 2h, and then hot forged, with an initial forging temperature of 1250°C, a final forging temperature of 1150°C, a forging ratio of 1.95, an elongation of 92.31%, and a total ratio of 3.81, air cooled to room temperature, and then solution treated at 1100-1200°C for 1h, water cooled to room temperature, and then cold rolled, with a total cold rolling reduction of more than 60%, and then annealed at 1150°C for 5-30min, and water cooled to room temperature.

[0016] The third aspect of the present invention provides the use of the above-mentioned antibacterial super duplex stainless steel in the preparation of stainless steel products.

[0017] Furthermore, the above-mentioned stainless steel products include but are not limited to medical devices, sanitary ware, offshore platforms or steam turbine parts.

[0018] The chemical composition and effect of the antibacterial super duplex stainless steel of the present invention are described in detail below: C is an austenite forming element, and a too high content of C is easy to form chromium carbide with chromium, which deteriorates the corrosion resistance and toughness of the material. Therefore, the present invention controls the content of C to be below 0.03%.

[0019] Si is a ferrite-forming element. At high temperatures, it can form a continuous and dense silicon dioxide protective layer in the ferrite region, thereby improving the oxidation resistance of steel. An appropriate amount of Si can also improve the strength, plasticity, toughness and welding performance of steel, thereby improving its stress corrosion resistance. However, too high a Si content will promote the precipitation of intermetallic phases, so the present invention controls it to be below 0.65%.

[0020] Mn is an austenite forming element, which can increase the solid solubility of N in steel, balance the ratio of two phases, and reduce the number of precipitated phases. An appropriate amount of Mn can improve the corrosiveness and low-temperature toughness of steel, but excessive Mn will react with S to form MnS inclusions, promote the precipitation of σ phase, and reduce the corrosion resistance and plastic toughness of steel. The present invention controls the Mn content to be below 1%.

[0021] P and S are harmful elements, which are detrimental to the thermal processing and corrosion resistance of the material. In the present invention, P is controlled to be ≤0.035% and S to be ≤0.03%. Cr is an element that improves the corrosion resistance of steel and can promote the formation of chromium-containing passivation film to protect steel from atmospheric corrosion. However, too high Cr content will accelerate the precipitation of intermetallic compounds, seriously affecting the performance of steel and being unfavorable for the production and application of steel. The present invention controls the Cr content within 30% to 34%.

[0022] N can improve the corrosion resistance of steel and significantly improve the strength of steel. N can replace a part of Ni. In dual-phase steel, N is generally added to adjust the Ni content to achieve a proper phase balance. The content of the present invention is controlled at 0.4% to 0.5%.

[0023] Ni is an element that strongly forms and expands the austenite region. When the content of Ni is less than 6%, it is difficult to ensure the austenite content. However, the price of Ni is relatively high, so the content should be controlled within the range of 6% to 8%.

[0024] Mo is a ferrite forming element and can improve the corrosion resistance of steel. However, the presence of Mo also increases the tendency of stainless steel to form intermetallic phases. Therefore, Mo should not be added too much. The present invention controls the content within 3% to 5%.

[0025] The addition of rare earth Ce can purify molten steel, improve the oxidation resistance, high temperature strength and creep strength of steel, and increase the corrosion resistance of the material. A certain content of rare earth Ce also has an antibacterial effect, which is controlled at 0.15% to 0.25% in the present invention.

[0026] Cu is an important component in the antibacterial duplex stainless steel of the present invention. When a certain amount of copper is added to duplex stainless steel, a copper-rich phase is precipitated after aging to give the steel good antibacterial properties, but the processing performance and corrosion resistance of the steel are reduced. Copper is added to super duplex stainless steel to a content of less than 3.5%.

[0027] Ag has excellent antibacterial effect, and only a trace amount is needed to make the matrix have excellent antibacterial properties. However, Ag is difficult to directly dissolve in the stainless steel matrix, and is easy to precipitate at the grain boundary, affecting the material's forming performance and corrosion resistance. With the help of Cu as an intermediate element to improve the solid dissolution of Ag, the content of Ag in the present invention is controlled below 0.15%.

[0028] Ru can enhance the stability and repassivation ability of the passivation film, especially in a chloride-containing environment, it has a significant inhibitory effect on pitting and crevice corrosion; it can also synergize with Cu and Ag to improve the antibacterial efficiency.

[0029] The Ti element can significantly improve the strength and toughness by refining the grains and stabilizing the secondary phase (such as TiC or TiN). It can also inhibit the grain growth at high temperature, refine the grain structure, and enhance the high temperature strength and toughness.

[0030] The research and application of single antibacterial elements to prepare antibacterial stainless steel has been around for quite a long time, and the addition of another antibacterial element is usually to improve the defects of a single element. For example, Cu is added to improve the solid solubility of Ag in the matrix while adding the Ag element; through the synergistic effect of Ru, Cu and Ag, a precipitate phase with significant antibacterial effect is formed on the surface of the material, and the antibacterial rates of Escherichia coli and Staphylococcus aureus can reach more than 99.9%. In fact, when two or more antibacterial elements are added, the antibacterial properties of the material can be significantly improved; while for mechanical properties and corrosion resistance, the effects of the addition of multiple elements are more complicated. In theory, Ti and Ru synergistically inhibit grain growth, which can significantly improve high-temperature oxidation resistance and mechanical properties; and Ti and Cr synergistically further improve corrosion resistance in chloride-containing environments.

[0031] The present invention provides a new idea in the design of antibacterial super duplex stainless steel composition. The multi-element synergistic antibacterial effect improves the comprehensive performance of steel under the premise of giving stainless steel antibacterial properties. The deformation heat treatment process of the present invention is: hot forging after keeping at 1250℃ for 2h, the initial forging temperature is 1250℃, the final forging temperature is 1150℃, air cooling, then, solution treatment at 1100-1200℃ for 1h and water cooling, and multiple cold rolling, the total cold rolling reduction is greater than 60%, the thickness after cold rolling is 1-2mm, and finally 1150℃ short-time annealing is performed for 5-30min, and the solution and annealing treatments are performed in a box-type resistance furnace.

[0032] Since the ingots and forged ingots are air-cooled, the σ secondary precipitation phase exists in the material, and the microstructure needs to be optimized through a solution treatment of high-temperature heating and rapid cooling. When the solution temperature is too low, the secondary phases (such as σ phases) that affect the performance cannot be eliminated, which seriously reduces the mechanical properties and corrosion resistance of the antibacterial duplex stainless steel; if the solution temperature is too high, the grains of the ferrite / austenite phase will be coarse. After many experiments in the early stage, when the solution temperature is 1100°C, there is neither a secondary phase in the antibacterial super duplex stainless steel, nor the grains in the two phases grow excessively, and the mechanical properties are optimal at this time. Therefore, the suitable solution treatment conditions in the present invention are: temperature of 1100°C, insulation for 1h, and water cooling to room temperature.

[0033] By designing the cold rolling and annealing process parameters, the best balance between performance and formability can be achieved, so that duplex stainless steel can achieve ideal performance in terms of high strength, good ductility and excellent corrosion resistance. Cold rolling is a process that imposes large plastic deformation on the material at room temperature. Plastic deformation introduces a large number of dislocations and increases the dislocation density, thereby significantly improving the strength and hardness of the material; the grains are elongated and broken by a certain amount of deformation, which is conducive to obtaining a more uniform and fine grain structure in the subsequent recrystallization process. Since the residual stress and work hardening introduced after cold rolling reduce the plasticity and ductility of the material, the ductility of the material is restored by recrystallization through annealing treatment, and the present invention adopts a high temperature short-time annealing of 1150°C and 5 to 30 minutes to avoid excessive growth of the grains after annealing.

[0034] The beneficial effects of the present invention are: The present invention adds trace amounts of Cu, Ce, Ag, Ru, and Ti elements to super duplex stainless steel, exerts the synergistic effect between the elements, and does not require aging heat treatment, so that the copper-rich phase is precipitated on the Ce particle, and the Ag element improves the solid solubility of Ag through the action of the Cu master alloy, and through the synergistic effect of Ru, Cu, and Ag, a precipitation phase with a significant antibacterial effect is formed on the surface of the material, which can improve the excellent mechanical properties and corrosion resistance of the material while giving the material excellent antibacterial properties. The present invention optimizes the deformation heat treatment process, combines hot forging and cold rolling processes, and the addition of trace elements is pollution-free to the environment, and the antibacterial effect is long-lasting, so that the material is suitable for related fields with antibacterial and high-performance requirements such as chemical industry, ocean, oil and natural gas. The deformation heat treatment method of the antibacterial super duplex stainless steel described in the present invention is simple, the performance improvement effect is significant, and it has significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 : Metallographic structure diagrams of comparative example 1 (a), example 1 (b), example 2 (c), and example 3 (d) super duplex stainless steel.

[0036] Figure 2 : The residual bacteria on the surface of the super duplex stainless steel of comparative example 1 after 24 hours of cultivation in the Escherichia coli antibacterial experiment.

[0037] Figure 3 : The residual bacteria on the surface of the super duplex stainless steel in Example 1 after 24 hours of cultivation in the Escherichia coli antibacterial experiment.

[0038] Figure 4 : The residual bacteria on the surface of the super duplex stainless steel of Example 2 after 24 hours of cultivation in the Escherichia coli antibacterial experiment.

[0039] Figure 5: The residual bacteria on the surface of the super duplex stainless steel of Example 3 after 24 hours of cultivation in the Escherichia coli antibacterial experiment.

[0040] Figure 6 : The residual bacteria on the surface of the super duplex stainless steel of comparative example 1 after 24h of cultivation in the antibacterial experiment of Staphylococcus aureus.

[0041] Figure 7 : The residual bacteria on the surface of the super duplex stainless steel of Example 1 after 24 hours of cultivation in the antibacterial experiment of Staphylococcus aureus.

[0042] Figure 8 : The residual bacteria on the surface of the super duplex stainless steel of Example 2 after 24 hours of cultivation in the antibacterial experiment of Staphylococcus aureus.

[0043] Fig. 9 : The residual bacteria on the surface of the super duplex stainless steel of Example 3 after 24h of cultivation in the antibacterial experiment of Staphylococcus aureus. DETAILED DESCRIPTION

[0044] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0045] The chemical compositions of the super duplex stainless steels of various embodiments and comparative examples are shown in Table 1.

[0046] Table 1 Chemical composition (wt%) The deformation heat treatment methods of the super duplex stainless steels of various embodiments and comparative examples are shown in Table 2.

[0047] Table 2 Deformation heat treatment method The preparation method of each embodiment and comparative example super duplex stainless steel adopts the following steps: (1) Ingredients: Ingredients are prepared according to the ingredients and mass percentages in Table 1. The required raw materials need to be degreased, degassed, derusted and dried to reduce the impurity content.

[0048] (2) Melting: The prepared materials are placed in a vacuum induction furnace and heated at 1620-1650°C and 1-10 Pa for 30-40 min until completely melted. Then, they are refined at 1600-1620°C and 0.1-1 Pa for 10 min to improve the purity and obtain stainless steel liquid.

[0049] (3) Casting: Cast the stainless steel liquid into shape, air cool it to room temperature, and obtain a steel ingot. Before casting, the stainless steel liquid needs to be preheated to 1520-1570°C to reduce the temperature gradient and prevent the occurrence of cold cracking defects. The casting speed is controlled at 100-200 mL / s, and the entire casting time is controlled within 30 seconds.

[0050] (4) Thermomechanical treatment: The steel ingot is subjected to thermomechanical treatment according to the method described in Table 2 to obtain super duplex stainless steel.

[0051] Figure 1 The metallographic organization diagrams of the super duplex stainless steel of Examples 1 to 3 and Comparative Example 1 are shown in Table 3, where the austenite is white lamellar and the ferrite is a black-gray matrix. The comparison between the two is shown in Table 3. As can be seen from the table, the austenite phase ratio of the super duplex stainless steel of Examples 1 to 3 is less than that of Comparative Example 1, but with the addition of Cu and Ag elements, the austenite phase ratio is increased.

[0052] Combination Figure 1 The metallographic structure diagram shows that after cold rolling and high-temperature short-time annealing, the metallographic structure of the material presents a lamellar structure, and the distribution direction of the lamellar is parallel to the rolling direction. The austenite in the ultra-super duplex stainless steel of Comparative Example 1 is relatively uniform and fine, showing a uniform layered feature. The morphology of the austenite phase in the ultra-super duplex stainless steel of Examples 1 to 3 is significantly different, showing large long strips and small long strips dispersed therein.

[0053] Table 3 Statistics of two-phase ratio Sample Austenite(%) Ferrite(%) Example 1 26.4 72.6 Example 2 27.6 72.4 Example 3 28.5 71.5 Comparative Example 1 35.5 64.5 According to the Japanese standard JIS Z 2801:2000 "Test methods and antibacterial effects of antibacterial processed products" and the Chinese light industry standard QG / T 2591-2003 "Test methods and antibacterial effects of antibacterial plastics", the antibacterial properties of super duplex stainless steel were tested by coating method. This method is to quantitatively inoculate bacteria onto the test sample, let the bacteria contact the material for a certain period of time, and then use the plate colony counting method to determine the number of surviving bacteria, and then calculate the antibacterial rate. The colony count is carried out in accordance with GB / T 4789.2-2010 "National Food Safety Standard Food Microbiology Test Colony Count Determination". The test strains are Escherichia coli and Staphylococcus aureus. The experimental process is as follows: (1) 15 mm*15 mm square specimens were cut from the super duplex stainless steel of Examples 1 to 3 and Comparative Example 1, and the surfaces were grinded with sandpaper of 600, 800, 1000, 1200, and 1500 meshes, respectively, ultrasonically cleaned in ethanol, and sterilized at 121° C. for 20 min; (2) Place the sterilized sample in a sterile culture dish in a clean bench and use a pipette to take 30 μL of a 5*10 5The standard bacterial solution of cfu / ml is evenly dropped onto the surface of the experimental sample and the control sample; (3) Cover the sample surface with PE film, seal the culture dish and place it in an incubator at 36±1°C and 90% humidity for 24 h; (4) Finally, count the number of bacteria from the culture dish and calculate the sterilization rate.

[0054] Each strain and sample was repeated 3 times and the average value was taken. The calculation formula of antibacterial rate is: antibacterial rate (%) = (number of viable bacteria in control sample - number of viable bacteria in experimental sample) / number of viable bacteria in control sample * 100%. The antibacterial performance test results of the super duplex stainless steel of comparative example 1 as the control sample are shown in Table 4.

[0055] Table 4 Antibacterial performance test results It can be seen from Table 4 that the antibacterial super duplex stainless steels provided in Examples 1 to 3 have significant antibacterial effects. After 24 hours of cultivation, the number of live bacteria on the surface of the duplex stainless steel is very small, and the antibacterial rates of the super duplex stainless steel in Example 3 against Escherichia coli and Staphylococcus aureus are both above 99.9%.

[0056] The mechanical properties of the antibacterial super duplex stainless steel obtained by the above-mentioned deformation heat treatment method were tested in accordance with the national standard GB / T228-2002 "Room Temperature Tensile Test Method for Metallic Materials"; the corrosion resistance was tested using a Chenhua 660E electrochemical workstation, the test system was a standard three-electrode system, and the test solution was 3.5% NaCl solution. The results are shown in Tables 5 and 6.

[0057] Table 5 Comparison of mechanical properties and corrosion resistance of duplex stainless steel in the embodiments of the present invention and in the comparative examples It can be seen from Table 5 that after the thermomechanical treatment, the examples are superior to the comparative examples in both tensile strength and elongation, indicating that the thermomechanical treatment process of the present invention significantly improves the comprehensive mechanical properties of the material. In particular, Example 3 not only has the highest tensile strength, but also has a relatively high elongation, reflecting excellent strong-plastic matching characteristics.

[0058] Table 6 Comparison of corrosion resistance of duplex stainless steel in the present invention and comparative example 1 The higher the corrosion current density and the lower the pitting potential, the stronger the corrosion resistance. It can be seen from Table 6 that after the deformation heat treatment, the corrosion resistance of the embodiment is improved compared with the base material of comparative example 1. In terms of comprehensive antibacterial mechanics and corrosion resistance, the antibacterial super duplex stainless steel of the present invention has excellent comprehensive performance.

[0059] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. An antibacterial super duplex stainless steel, characterized by: The composition and mass percentage of the antibacterial super duplex stainless steel are: C≤0.03%, Si≤0.65%, Mn≤1%, P≤0.035%, S≤0.03%, Ni: 6%~8%, Cr: 30%~34%, Mo: 3%~5%, N: 0.4%~0.5%, Ce: 0.15%~0.25%, Cu: 0%~3.5%, Ag: 0%~0.15%, Ru: 0.05%~0.2%, Ti: 0.05%~0.15%, and the balance is Fe and unavoidable impurities.

2. The antibacterial super duplex stainless steel according to claim 1, characterized in that: The composition and mass percentage of the antibacterial super duplex stainless steel are: C: 0.02%, Si: 0.65%, Mn: 0.89%, S: 0.03%, P: 0.02%, Cr: 32.00%, Ni: 7.53%, Mo: 4.74%, N: 0.49%, Ce: 0.17%, Ru: 0.1%, Ti: 0.08%, and the balance is Fe and unavoidable impurities.

3. The antibacterial super duplex stainless steel according to claim 1, characterized in that: The composition and mass percentage of the antibacterial super duplex stainless steel are: C: 0.02%, Si: 0.56%, Mn: 0.98%, S: 0.03%, P: 0.02%, Cr: 31.08%, Ni: 7.94%, Mo: 4.8%, N: 0.45%, Ce: 0.23%, Cu: 2.58%, Ru: 0.12%, Ti: 0.11%, and the balance is Fe and unavoidable impurities.

4. The antibacterial super duplex stainless steel according to claim 1, characterized in that: The composition and mass percentage of the antibacterial super duplex stainless steel are: C: 0.02%, Si: 0.47%, Mn: 0.97%, S: 0.03%, P: 0.02%, Cr: 31.16%, Ni: 7.64%, Mo: 4.32%, N: 0.48%, Ce: 0.2%, Cu: 3.05%, Ag: 0.11%, Ru: 0.13%, Ti: 0.12%, and the balance is Fe and unavoidable impurities.

5. The antibacterial super duplex stainless steel according to claim 1, characterized in that: The antibacterial super duplex stainless steel has a lamellar structure, an austenite content of 26.4% to 28.5%, a ferrite content of 71.5% to 72.6%, a tensile strength of 1174 to 1289 MPa, an elongation of 30.5% to 33.4%, and an antibacterial rate of more than 97%.

6. The method for preparing the antibacterial super duplex stainless steel according to claim 1, characterized in that: The following steps are involved: S1: According to the composition and mass percentage of claim 1, the steel ingot is obtained by melting and casting in a vacuum induction furnace; S2: The steel ingot is subjected to deformation heat treatment to obtain antibacterial super duplex stainless steel.

7. The preparation method according to claim 6, characterized in that: The smelting includes melting treatment and refining treatment. The temperature of the melting treatment is 1620-1650°C and the time is 30-40 minutes. The temperature of the refining treatment is 1600-1620°C and the time is 10 minutes. The temperature of the casting is 1520-1570°C and the time is controlled within 30 seconds.

8. The preparation method according to claim 6, characterized in that: The method of the deformation heat treatment is: the steel ingot is kept at 1250°C for 2h, then hot forged, with an initial forging temperature of 1250°C, a final forging temperature of 1150°C, a forging ratio of 1.95, an elongation of 92.31%, and a total ratio of 3.81, air cooled to room temperature, then solution treated at 1100-1200°C for 1h, water cooled to room temperature, and then cold rolled, with a total cold rolling reduction of more than 60%, then annealed at 1150°C for 5-30min, and water cooled to room temperature.

9. Use of the antibacterial super duplex stainless steel according to claim 1 in the preparation of stainless steel products.

10. The use according to claim 9, characterized in that: The stainless steel products include but are not limited to medical equipment, sanitary ware, offshore platforms or steam turbine parts.

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