Martensitic stainless steel having excellent antibacterial properties and method for manufacturing the same

Abstract

The application discloses a kind of martensitic stainless steel with excellent antibacterial performance and manufacturing method thereof, belong to special stainless steel material technical field.The stainless steel of the application is based on iron, and alloy elements such as C, Cr, Cu, Mo, Ni, V, Si and Mn are reasonably proportioned, the mass percentage of each component is accurately controlled, the high-efficiency antibacterial effect is realized by relying on copper element nano-dispersed precipitated phase, and the basic performance of high hardness, high strength, excellent wear resistance and corrosion resistance of martensitic stainless steel is retained.The components of the stainless steel are as follows in terms of mass percentage:C 0.30%-0.50%, Cr 12.00%-14.00%, Cu 0.80%-1.80%, Mo 0.20%-0.80%, Ni 0.10%-0.30%, V 0.05%-0.20%, Si≤0.50%, Mn≤0.60%, P≤0.030%, S≤0.010%, and the balance is Fe and unavoidable impurities.The application uses a special process of vacuum melting, electroslag remelting, forging rolling and step-by-step gradient heat treatment to uniformly precipitate nano-sized copper-rich antibacterial phase in the stainless steel matrix, and solves the technical problems of performance attenuation, insufficient corrosion resistance, and difficulty in balancing hardness and antibacterial properties after heat treatment.

Description

Technical Field

[0001] This invention relates to the field of special stainless steel materials technology, specifically to a martensitic stainless steel with excellent antibacterial properties and its manufacturing method, which is suitable for medical devices, food processing, kitchen and bathroom equipment, precision wear-resistant parts and other scenarios with stringent requirements for hardness, corrosion resistance and antibacterial properties. Background Technology

[0002] Martensitic stainless steel, with its high hardness, high strength, excellent wear resistance, and hardenability, is widely used in cutting tools, medical surgical instruments, precision mechanical parts, and food processing equipment. However, traditional martensitic stainless steel lacks antibacterial properties. During long-term use, harmful bacteria such as Escherichia coli and Staphylococcus aureus easily adhere to its surface. The large-scale proliferation of bacteria can cause hygiene contamination, not only affecting product lifespan but also endangering human health, failing to meet the hygiene and safety standards of high-end fields such as medical care and food processing.

[0003] Existing antibacterial martensitic stainless steels mostly employ a single copper modification method, which has significant technical drawbacks: First, the copper content ratio is unreasonable. Too low a copper content fails to form an effective antibacterial precipitate, resulting in poor antibacterial effect and insufficient durability; too high a copper content easily leads to deterioration of the steel's hot working properties, causing cracking, inclusion defects, and reduced mechanical properties and corrosion resistance. Second, the heat treatment process is singular, making it impossible to precisely control the size and distribution of copper-rich phase precipitation, easily leading to precipitate agglomeration and coarseness, which not only results in poor antibacterial stability but also reduces the steel's hardness and toughness. Third, the alloy element matching in existing formulation systems is poor, with imbalances in the proportions of elements such as carbon, chromium, and molybdenum, leading to a significant decrease in the corrosion resistance of the stainless steel after antibacterial modification, making it unsuitable for humid and corrosive environments. Fourth, conventional preparation processes result in high impurity content and poor matrix density, further restricting the improvement of antibacterial performance and comprehensive mechanical properties.

[0004] Currently available antibacterial martensitic stainless steels generally suffer from low antibacterial rates, poor performance stability, and an inability to simultaneously achieve high hardness, antibacterial properties, and corrosion resistance, severely limiting their application in high-end, precision, and high-hygiene environments. Therefore, developing a martensitic stainless steel that balances high hardness, high corrosion resistance, efficient and durable antibacterial properties, and is suitable for industrial production, has become a key research focus for those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a martensitic stainless steel with excellent antibacterial properties and its manufacturing method, thereby solving the technical problems of poor antibacterial effect, insufficient stability, imbalance between mechanical properties and corrosion resistance, and poor processing performance of traditional products, and achieving synergistic optimization of antibacterial properties, hardness, wear resistance and corrosion resistance.

[0006] 1. Carbon (C): Carbon is the core element for strengthening martensitic stainless steel. It enhances the hardness and wear resistance of steel through solid solution strengthening and carbide precipitation strengthening. This invention controls the carbon content to 0.30%~0.50%, ensuring that the steel obtains a high-hardness martensitic matrix after quenching to meet the requirements for wear resistance, while avoiding excessive carbon content that leads to the formation of a large amount of chromium carbide, resulting in chromium depletion in the matrix and reduced corrosion resistance. At the same time, it prevents the carbon content from being too low, which would lead to insufficient matrix strength and hardness.

[0007] 2. Chromium (Cr): Chromium is the core element for the corrosion resistance of stainless steel. It can form a dense passivation film on the steel surface, blocking the intrusion of corrosive media. This invention controls the chromium content to 12.00%~14.00% to ensure that the steel has excellent resistance to atmospheric corrosion and water corrosion. At the same time, it is suitable for martensitic structure forming and avoids the austenite structure residue caused by excessive chromium content, which would affect the quenching hardness.

[0008] 3. Copper (Cu): Copper is the core element for the antibacterial properties of this invention. During the tempering process of stainless steel, copper precipitates a nano-sized copper-rich phase, which continuously releases trace amounts of copper ions, disrupting bacterial cell membranes, enzyme systems, and genetic material, thus achieving a broad-spectrum antibacterial effect. This invention precisely controls the copper content to 0.80%~1.80%, ensuring sufficient antibacterial phase formation for highly efficient antibacterial effects while avoiding defects such as heat-processing cracking and inclusions caused by excessive copper content.

[0009] 4. Molybdenum (Mo): Molybdenum can refine the grains of steel, improve the density of the matrix, and significantly improve the resistance of stainless steel to pitting corrosion and crevice corrosion. At the same time, it works synergistically with carbon and chromium to improve the high-temperature stability and wear resistance of steel, offsetting the slight decrease in corrosion resistance caused by the addition of copper. In this invention, the molybdenum content is controlled at 0.20%~0.80%.

[0010] 5. Nickel (Ni): Nickel can improve the toughness and hot working performance of steel, refine the martensitic structure, reduce residual stress after quenching, and prevent steel from cracking. The addition of trace amounts of nickel can balance the brittle defects of high-hardness matrix. This invention controls the nickel content to 0.10%~0.30% to avoid excessive nickel content affecting the martensitic phase transformation.

[0011] 6. Vanadium (V): Vanadium is a strong carbide-forming element that can refine grains, disperse and strengthen the matrix, improve the hardness, wear resistance and structural stability of steel, inhibit grain coarsening during heat treatment, reduce impurity segregation, and improve the overall performance of steel. This invention controls the vanadium content to be 0.05%~0.20%.

[0012] 7. Silicon (Si) and Manganese (Mn): Silicon is used for deoxidation and refining to improve the purity of molten steel; manganese is used for desulfurization and to improve processing performance. The upper limit of its content must be strictly controlled to avoid excessive silicon and manganese inclusions from affecting corrosion resistance and the uniform distribution of antibacterial precipitates.

[0013] 8. Phosphorus (P) and Sulfur (S): Strictly limit the content of harmful impurities, reduce grain boundary segregation and inclusion defects, improve the toughness, corrosion resistance and uniformity of the steel structure, and ensure stable output of antibacterial properties.

[0014] The manufacturing method principle of this invention This invention employs a two-stage purification process of vacuum melting and electroslag remelting, which significantly reduces the content of gas and impurities in molten steel, improves the density and uniformity of the matrix, and lays the foundation for the uniform precipitation of antibacterial phases. Through high-temperature gradient forging and rolling, the matrix grains are refined, casting defects are eliminated, and the mechanical properties of the steel are improved. A unique heat treatment process of quenching + deep cryogenic treatment + segmented tempering is adopted. First, a high-hardness martensitic matrix is ​​obtained through high-temperature quenching, and deep cryogenic treatment completely eliminates residual austenite and improves the stability of the structure. Finally, through medium-temperature precise tempering, nano-sized, dispersed copper-rich antibacterial phases can be controlled to precipitate, which ensures excellent antibacterial performance without sacrificing the hardness and corrosion resistance of the steel, achieving optimal synergy of multiple properties.

[0015] Beneficial effects Compared with the prior art, the present invention has the following significant advantages: 1. Excellent and stable antibacterial properties: This invention forms a copper-rich antibacterial phase with a 20~80nm diffuse distribution in the matrix through precise copper content ratio and exclusive tempering process. It has an antibacterial rate of ≥99.0% against Escherichia coli and Staphylococcus aureus, strong antibacterial durability, no antibacterial attenuation after long-term use, and has a broad-spectrum antibacterial effect.

[0016] 2. Excellent comprehensive mechanical properties: The finished steel has a hardness of ≥58HRC, and has high strength, high wear resistance and good toughness. It is free from processing cracking defects, fully meets the requirements of precision instruments and wear-resistant parts, and solves the problems of insufficient hardness and high brittleness of traditional antibacterial stainless steel.

[0017] 3. Excellent corrosion resistance: Through the synergistic ratio of chromium, molybdenum and nickel elements, the matrix structure is optimized, the passivation film of the steel has strong stability, and the corrosion resistance time in the neutral salt spray test is ≥200h. It can be adapted to humid, weak acid and weak alkali corrosion conditions, and has a wider range of applications.

[0018] 4. Controllable process and suitable for industrialization: The manufacturing process of this invention is simple and the parameters are precisely controllable. The two-stage purification process ensures the stability of steel quality, and the heat treatment process can precisely control the precipitation state of the antibacterial phase. It is suitable for large-scale industrial mass production and the production cost is controllable.

[0019] 5. Excellent performance synergy: Breaking through the bottleneck of mutual constraints between antibacterial properties, hardness, and corrosion resistance in traditional technologies, it achieves simultaneous excellence in the three core properties, with comprehensive performance far exceeding that of existing similar antibacterial martensitic stainless steel products. Attached Figure Description

[0020] Figure 1This is a process flow diagram for preparing martensitic stainless steel according to the present invention; Figure 2 This is a microstructure diagram of the stainless steel matrix of the present invention (distribution of nano-copper-rich precipitates). Figure 3 This is a bar chart comparing the antibacterial properties of the embodiments and comparative examples of the present invention; Figure 4 This is a graph comparing the hardness and corrosion resistance of the embodiments and comparative examples of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] A martensitic stainless steel with excellent antibacterial properties has the following composition by mass percentage: C: 0.38%, Cr: 13.00%, Cu: 1.30%, Mo: 0.50%, Ni: 0.20%, V: 0.12%, Si: 0.30%, Mn: 0.40%, P: 0.018%, S: 0.006%, with the balance being Fe and unavoidable impurities.

[0023] Manufacturing method: S1. Vacuum melting: Select high-purity raw materials according to the formula, put them into a vacuum induction melting furnace, vacuum degree 3Pa, heat up to 1600℃, hold for 25min to refine and remove impurities, and cast into steel ingots. S2. Electroslag remelting: Using CaF2-Al2O3-CaO ternary slag (CaF2: 70%, Al2O3: 20%, CaO: 10%), the remelting voltage is 40V, the current is 2000A, and the remelting speed is 10kg / min to obtain high-density steel ingots. S3. Forging and rolling: Preheat steel ingot to 1200℃, hold for 75min, forge billet, final forging temperature 980℃; hot roll at 1160℃, total deformation 80%, air cool to room temperature. S4. Gradient heat treatment: oil quenching at 1050℃ for 40 min; deep cryogenic holding at -80℃ for 100 min after quenching; tempering at 500℃ for 150 min; furnace cooling to 200℃ followed by air cooling. S5. Fine finishing and polishing to remove oxide scale and straighten to obtain finished stainless steel.

[0024] Example 2 A martensitic stainless steel with excellent antibacterial properties has the following composition by mass percentage: C: 0.35%, Cr: 12.50%, Cu: 1.20%, Mo: 0.40%, Ni: 0.15%, V: 0.10%, Si: 0.25%, Mn: 0.35%, P: 0.015%, S: 0.005%, with the balance being Fe and unavoidable impurities.

[0025] The manufacturing method is the same as in Example 1, with minor parameter adjustments: melting temperature 1590℃, holding temperature 22min; tempering temperature 490℃, holding temperature 160min.

[0026] Example 3 A martensitic stainless steel with excellent antibacterial properties has the following composition by mass percentage: C: 0.45%, Cr: 13.50%, Cu: 1.50%, Mo: 0.60%, Ni: 0.25%, V: 0.15%, Si: 0.35%, Mn: 0.45%, P: 0.020%, S: 0.007%, with the balance being Fe and unavoidable impurities.

[0027] The manufacturing method is the same as in Example 1, with minor parameter adjustments: melting temperature 1610℃, holding temperature 28min; tempering temperature 510℃, holding temperature 140min.

[0028] Comparative Example 1 (Traditional Copper-Free Martensitic Stainless Steel) Composition: C: 0.40%, Cr: 13.00%, Si: 0.30%, Mn: 0.40%, P≤0.030%, S≤0.010%, balance Fe; prepared using conventional quenching and tempering process.

[0029] Comparative Example 2 (High-copper antibacterial stainless steel, copper content exceeds the standard) Composition: C: 0.38%, Cr: 13.00%, Cu: 2.00%, Mo: 0.50%, Ni: 0.20%, V: 0.12%, balance Fe; preparation process is the same as in Example 1.

[0030] Performance test results Performance tests were conducted on the products of each embodiment and comparative example. The testing standards were as follows: antibacterial performance was tested according to GB / T 21866-2008 "Test Method for Antibacterial Performance of Antibacterial Ceramic Products"; hardness was tested according to GB / T 230.1-2018; and corrosion resistance was tested according to GB / T10125-2021 neutral salt spray test. The test results are as follows: Example 1: Hardness 59.2 HRC, antibacterial rate of Escherichia coli 99.4%, antibacterial rate of Staphylococcus aureus 99.2%, no rust after 220h salt spray test; Example 2: Hardness 58.5 HRC, antibacterial rate of Escherichia coli 99.1%, antibacterial rate of Staphylococcus aureus 99.0%, no rust after 210h salt spray test; Example 3: Hardness 60.1 HRC, antibacterial rate of Escherichia coli 99.5%, antibacterial rate of Staphylococcus aureus 99.3%, no rust after 230h salt spray test; Comparative Example 1: Hardness 57.8 HRC, antibacterial rate 0%, slight corrosion after 180h salt spray test; Comparative Example 2: Hardness 55.3 HRC, antibacterial rate 99.6%, obvious corrosion after 150h salt spray test, micro-crack defects in hot working.

[0031] The test results show that the product of this invention has significantly improved antibacterial properties compared to traditional products. At the same time, its hardness and corrosion resistance are significantly better than the comparative example. It has no processing defects and has the best overall performance. Although the comparative example with excessive copper content has slightly higher antibacterial properties, its mechanical properties and corrosion resistance are significantly reduced, and its practicality is extremely poor.

[0032] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0033] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A martensitic stainless steel with excellent antibacterial properties, characterized in that, By mass percentage, it contains the following alloy components: C: 0.30%~0.50%, Cr: 12.00%~14.00%, Cu: 0.80%~1.80%, Mo: 0.20%~0.80%, Ni: 0.10%~0.30%, V: 0.05%~0.20%, Si≤0.50%, Mn≤0.60%, P≤0.030%, S≤0.010%, with the balance being Fe and unavoidable trace impurities.

2. The martensitic stainless steel with excellent antibacterial properties according to claim 1, characterized in that, By mass percentage, it contains the following optimized components: C: 0.35%~0.45%, Cr: 12.50%~13.50%, Cu: 1.20%~1.50%, Mo: 0.40%~0.60%, Ni: 0.15%~0.25%, V: 0.10%~0.15%, Si: 0.20%~0.40%, Mn: 0.30%~0.50%, P≤0.020%, S≤0.008%, with the balance being Fe and unavoidable trace impurities.

3. The martensitic stainless steel with excellent antibacterial properties according to claim 1, characterized in that, The stainless steel matrix contains uniformly dispersed nanoscale copper-rich precipitates with a particle size of 20-80 nm and a volume percentage of 1.5%-3.0%.

4. A method for manufacturing martensitic stainless steel with excellent antibacterial properties, characterized in that, The method for preparing the martensitic stainless steel according to any one of claims 1-3 comprises the following steps: S1. Raw material proportioning and vacuum melting: Select high-purity raw materials according to the component proportions, put them into a vacuum induction melting furnace, heat and melt them under vacuum degree ≤5Pa conditions, melting temperature 1580~1620℃, hold for 20~30min, and then cast into steel ingots after refining and removing impurities. S2. Electroslag remelting purification: The smelted steel ingots are subjected to electroslag remelting treatment. The remelting voltage is 38~42V, the current is 1800~2200A, and the remelting speed is 8~12kg / min to obtain high-density, low-impurity remelted steel ingots. S3. High-temperature forging and rolling: The remelted steel ingot is preheated to 1180~1220℃ and held for 60~90min before forging. The final forging temperature is ≥950℃. Then, it is hot rolled at 1150~1180℃ in multiple passes with a total deformation of ≥75%. After rolling, it is air-cooled to room temperature. S4. Segmented gradient heat treatment: The rolled steel is subjected to gradient heat treatment in sequence, including quenching, deep cryogenic treatment, and tempering antibacterial precipitation treatment. S5. Finishing: After heat treatment, the steel is ground, straightened, and descaled to obtain the finished antibacterial martensitic stainless steel.

5. The method for manufacturing a martensitic stainless steel with excellent antibacterial properties according to claim 4, characterized in that, The quenching process in step S4 is as follows: heat up to 1030~1080℃, hold for 30~50min, oil quench and cool to room temperature, with a quenching cooling rate ≥80℃ / min.

6. The method for manufacturing a martensitic stainless steel with excellent antibacterial properties according to claim 4, characterized in that, The cryogenic treatment process in step S4 is as follows: immediately after quenching, the steel is placed in a low temperature environment of -70~-90℃ and held for 90~120 minutes to eliminate residual austenite and improve the hardness and structural stability of the matrix.

7. The method for manufacturing a martensitic stainless steel with excellent antibacterial properties according to claim 4, characterized in that, The tempering antibacterial precipitation process in step S4 is as follows: heat to 480~530℃, hold for 120~180min, cool with the furnace to below 200℃ and then air cool, so as to promote the uniform precipitation of nano-scale copper-rich antibacterial phase in the matrix.

8. The method for manufacturing a martensitic stainless steel with excellent antibacterial properties according to claim 4, characterized in that, The slag used in step S2 electroslag remelting is a ternary slag of CaF2-Al2O3-CaO, with a slag ratio of CaF2: 65%~75%, Al2O3: 15%~25%, and CaO: 5%~15%.

9. A martensitic stainless steel with excellent antibacterial properties according to claim 1, characterized in that, The finished stainless steel product meets the following performance requirements: Rockwell hardness ≥ 58 HRC, antibacterial rate against Escherichia coli and Staphylococcus aureus ≥ 99.0%, and corrosion resistance time in neutral salt spray test ≥ 200 h.

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