Antibacterial stainless steel and preparation method thereof

Abstract

The invention discloses antibacterial stainless steel and a preparation method thereof. The antibacterial stainless steel provided by the invention comprises the following components: 0.03-0.14 wt% of C; 0.35 to 0.50 wt% of Si; 0.70 to 1.10 wt% of Mn; the content of S is 0.001 to 0.015 percent by weight; 0.01 to 0.06 wt% of P; 18.00 wt% to 20.00 wt% of Cr; 7.50 to 11.00 wt% of Ni; 0.03 to 0.50 wt% of Mo; 0.10 to 0.35 wt% of Cu; 0.26 to 0.66 wt% of Ce; and the balance of Fe and inevitable impurities. The antibacterial stainless steel has good antibacterial performance and mechanical performance.

Description

Technical Field

[0001] The invention relates to an antibacterial stainless steel and a preparation method thereof, and in particular to an antibacterial stainless steel free of heat treatment and a preparation method thereof. Background Art

[0002] In modern human society, stainless steel products, equipment and facilities have been widely used. However, stainless steel utensils, equipment and facilities that people come into direct or indirect contact with in daily life generally only have corrosion resistance and no antibacterial function, which may lead to potential risk of bacterial infection after contact or use. Some stainless steels with antibacterial properties need to add precious antibacterial metals such as silver during the production process, and also need to undergo solution treatment and aging heat treatment, which is a cumbersome process.

[0003] CN103667978A discloses a method for preparing an antibacterial austenitic stainless steel strip, wherein the stainless steel is further added with 0.4-0.6wt% Ag, 0.2-0.4wt% Ti, and the rest is Fe and unavoidable impurity elements, and the preparation method comprises the following steps: (1) smelting; (2) blanking; (3) hot rolling; (4) cold rolling and annealing; (5) solid solution and aging treatment. In this method, not only a specific amount of Ag and Ti is added, but also hot rolling, cold rolling, annealing, solid solution and aging treatment are performed, which is cumbersome and increases the cost.

[0004] CN104480407A discloses an antibacterial stainless steel containing copper and cerium and a preparation method thereof. The preparation method firstly smelts and prepares a stainless steel blank, then performs a solid solution treatment so that Cu and Ce are dissolved into a matrix material of the stainless steel blank in a supersaturated solid solution state, and then performs an aging treatment.

[0005] CN102181822A discloses an antibacterial stainless steel containing copper-cerium on the surface and a preparation method thereof, wherein the preparation method is to infiltrate and plate a copper-cerium alloy on the surface of a stainless steel substrate. The antibacterial stainless steel prepared by the preparation method has antibacterial properties only on the surface.

[0006] CN107761008A discloses an antibacterial and mildew-proof negative ion stainless steel and a preparation method thereof. The stainless steel contains many kinds of rare earth elements and also contains Ag, which results in a high cost. Summary of the invention

[0007] In view of this, one object of the present invention is to provide an antibacterial stainless steel having good antibacterial properties and mechanical properties. Another object of the present invention is to provide a method for preparing the antibacterial stainless steel as described above, which does not require solution treatment and aging treatment steps.

[0008] The present invention adopts the following technical solutions to achieve the above-mentioned purpose.

[0009] In one aspect, the present invention provides an antibacterial stainless steel having the following composition:

[0010] C 0.03~0.14wt%;

[0011] Si 0.35~0.50wt%;

[0012] Mn 0.70~1.10wt%;

[0013] S 0.001~0.015wt%;

[0014] P 0.01~0.06wt%;

[0015] Cr 18.00~20.00wt%;

[0016] Ni 7.50~11.00wt%;

[0017] Mo 0.03~0.50wt%;

[0018] Cu 0.10~0.35wt%;

[0019] Ce 0.26~0.66wt%;

[0020] The balance is Fe and inevitable impurities.

[0021] According to the antibacterial stainless steel of the present invention, preferably, it has the following composition:

[0022] C 0.06~0.14wt%;

[0023] Si 0.40~0.50wt%;

[0024] Mn 0.80~1.09wt%;

[0025] S 0.007~0.015wt%;

[0026] P 0.03~0.05wt%;

[0027] Cr 18.00~19.00wt%;

[0028] Ni 7.80~9.00wt%;

[0029] Mo 0.04~0.45wt%;

[0030] Cu 0.15~0.32wt%;

[0031] Ce 0.27~0.66wt%;

[0032] The balance is Fe and inevitable impurities.

[0033] According to the antibacterial stainless steel of the present invention, preferably, it has the following composition:

[0034] C 0.09~0.14wt%;

[0035] Si 0.43~0.50wt%;

[0036] Mn 0.85~1.02wt%;

[0037] S 0.009~0.015wt%;

[0038] P 0.03~0.042wt%;

[0039] Cr 18.00~18.50wt%;

[0040] Ni 7.80~8.50wt%;

[0041] Mo 0.04~0.06wt%;

[0042] Cu 0.15~0.25wt%;

[0043] Ce 0.52~0.59wt%;

[0044] The balance is Fe and inevitable impurities.

[0045] According to the antibacterial stainless steel of the present invention, preferably, its antibacterial rate against Staphylococcus aureus is greater than or equal to 99.5%, and its antibacterial rate against Escherichia coli is greater than or equal to 92.5%.

[0046] According to the antibacterial stainless steel of the present invention, preferably, the antibacterial rate against Staphylococcus aureus reaches 99.83%, and the antibacterial rate against Escherichia coli reaches 99.92%.

[0047] On the other hand, the present invention also provides a method for preparing the antibacterial stainless steel as described above, comprising the following steps:

[0048] 1) melting raw materials other than the cerium raw material in a vacuum induction furnace or a medium frequency induction furnace at 1450-1500° C. to obtain an initial alloy melt; wherein the cerium raw material is selected from elemental cerium or ferrocerium alloy;

[0049] 2) heating the initial alloy solution to 1500-1600° C., adding single substance cerium or ferrocerium alloy to the initial alloy solution at 1500-1600° C., and keeping the temperature at this temperature for 1-5 minutes to obtain alloy liquid;

[0050] 3) pouring the alloy liquid into an ingot mold or a die for solidification to obtain a steel ingot or a steel part; the steel ingot or the steel part is the antibacterial stainless steel.

[0051] According to the preparation method of the present invention, preferably, based on the weight of the ferrocerium alloy, the content of cerium element is 10-90 wt %.

[0052] According to the preparation method of the present invention, preferably, in step 2), the temperature is kept at 1500-1600° C. for 1-3 min.

[0053] According to the preparation method of the present invention, preferably, no solution treatment step and no aging treatment step are included.

[0054] According to the preparation method of the present invention, preferably, step 1) and step 2) are carried out under vacuum conditions, and the vacuum degree is less than 0.1 Pa.

[0055] The antibacterial stainless steel of the present invention has good antibacterial properties, and its antibacterial rate against Staphylococcus aureus is greater than or equal to 99.5%, which can reach 99.83%, and its antibacterial rate against Escherichia coli is greater than or equal to 92.5%, which can reach 99.92%; the antibacterial stainless steel of the present invention also has good mechanical properties, and its tensile strength can reach more than 730MPa. The antibacterial stainless steel of the present invention does not contain Ag and Ti, and the cost is reduced. In the preparation of the antibacterial stainless steel of the present invention, the solid solution treatment and aging treatment steps can be omitted, and the process flow is simplified. DETAILED DESCRIPTION

[0056] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0057] <Antibacterial stainless steel>

[0058] The present invention provides an antibacterial stainless steel having the following composition: C 0.03-0.14wt%; Si 0.35-0.50wt%; Mn 0.70-1.10wt%; S 0.001-0.015wt%; P 0.01-0.06wt%; Cr 18.00-20.00wt%; Ni 7.50-11.00wt%; Mo 0.03-0.50wt%; Cu 0.10-0.35wt%; Ce 0.26-0.66wt%; the remainder is Fe and unavoidable impurities. Such antibacterial stainless steel has good antibacterial properties, for example, the antibacterial rate against Staphylococcus aureus and Escherichia coli is high. The antibacterial stainless steel of the present invention does not need to add elements such as Ag and Ti. In addition, the antibacterial stainless steel of the present invention has a large tensile strength value and still has good mechanical properties. In addition, the preparation of the antibacterial stainless steel of the present invention can omit the solid solution treatment and aging treatment steps, thereby simplifying the process flow.

[0059] The antibacterial stainless steel of the present invention is different from the traditional antibacterial mechanism that relies on antibacterial metal elements such as Cu and Ag. The traditional antibacterial stainless steel using antibacterial metal elements such as Cu and Ag must be subjected to antibacterial heat treatment to make the antibacterial metal elements solid-dissolve and precipitate at high temperature to form a phase with antibacterial function in order to achieve the antibacterial ability. The present invention is based on the antibacterial ability of rare earth elements and their compounds themselves, combined with the characteristics of rare earth in steel, and uses rare earth compounds and solid-dissolved rare earth elements as antibacterial phases to achieve the purpose of antibacterial steel.

[0060] In the present invention, C is carbon element. Based on the total weight of the antibacterial stainless steel, the C content may be 0.03-0.14 wt%, preferably 0.06-0.14 wt%, more preferably 0.09-0.14 wt%, and further preferably 0.11-0.14 wt%.

[0061] In the present invention, Si is silicon element. Based on the total weight of the antibacterial stainless steel, the Si content may be 0.35-0.50 wt%, preferably 0.40-0.50 wt%, more preferably 0.43-0.50 wt%, and further preferably 0.44-0.48 wt%.

[0062] In the present invention, Mn is manganese element. Based on the total weight of the antibacterial stainless steel, the Mn content may be 0.70-1.10 wt %, preferably 0.80-1.09 wt %, and more preferably 0.85-1.02 wt %.

[0063] In the present invention, S is sulfur. Based on the total weight of the antibacterial stainless steel, the S content may be 0.001 to 0.015 wt %, preferably 0.007 to 0.015 wt %, and more preferably 0.009 to 0.015 wt %.

[0064] In the present invention, P is phosphorus. Based on the total weight of the antibacterial stainless steel, the P content may be 0.01 to 0.06 wt %, preferably 0.03 to 0.05 wt %, and more preferably 0.03 to 0.042 wt %.

[0065] In the present invention, Cr is a chromium element. Based on the total weight of the antibacterial stainless steel, the Cr content may be 18.00 to 20.00 wt %, preferably 18.00 to 19.00 wt %, and more preferably 18.00 to 18.50 wt %.

[0066] In the present invention, Ni is a nickel element. Based on the total weight of the antibacterial stainless steel, the Ni content may be 7.50 to 11.00 wt %, preferably 7.80 to 9.00 wt %, and more preferably 7.80 to 8.50 wt %.

[0067] In the present invention, Mo is molybdenum element. Based on the total weight of the antibacterial stainless steel, the Mo content may be 0.03-0.50 wt %, preferably 0.04-0.45 wt %, and more preferably 0.04-0.06 wt %.

[0068] In the present invention, Cu is copper element. Based on the total weight of the antibacterial stainless steel, the Cu content may be 0.10 to 0.35 wt %, preferably 0.15 to 0.32 wt %, and more preferably 0.15 to 0.25 wt %.

[0069] In the present invention, Ce is cerium. Based on the total weight of the antibacterial stainless steel, the Ce content can be 0.26-0.66wt%, preferably 0.27-0.66wt%, more preferably 0.52-0.59wt%, for example, 0.52wt%, 0.53wt%, 0.54wt%, 0.55wt%, 0.56wt%, 0.57wt%, 0.58wt%, 0.59wt%.

[0070] In the present invention, Fe is an iron element.

[0071] According to one embodiment of the present invention, the antibacterial stainless steel of the present invention has the following composition: C 0.06-0.14wt%; Si 0.40-0.50wt%; Mn 0.80-1.09wt%; S0.007-0.015wt%; P 0.03-0.05wt%; Cr 18.00-19.00wt%; Ni7.80-9.00wt%; Mo 0.04-0.45wt%; Cu 0.15-0.32wt%; Ce 0.27-0.66wt%; the balance is Fe and unavoidable impurities.

[0072] According to a preferred embodiment of the present invention, the antibacterial stainless steel of the present invention has the following composition: C 0.09-0.14wt%; Si 0.43-0.50wt%; Mn 0.85-1.02wt%; S0.009-0.015wt%; P 0.03-0.042wt%; Cr 18.00-18.50wt%; Ni7.80-8.50wt%; Mo 0.04-0.06wt%; Cu 0.15-0.25wt%; Ce 0.52-0.59wt%; the balance is Fe and unavoidable impurities.

[0073] The antibacterial rate of the antibacterial stainless steel of the present invention against Staphylococcus aureus is greater than or equal to 99.5%, preferably greater than or equal to 99.8%, and can reach 99.83%; the antibacterial rate against Escherichia coli is greater than or equal to 92.5%, preferably greater than or equal to 99.0%, and can reach 99.92%.

[0074] <Method for preparing antibacterial stainless steel>

[0075] The present invention also provides a method for preparing the antibacterial stainless steel as described above, comprising the following steps: (1) a preliminary melting step; (2) a full raw material melting step; and (3) a casting step. The present invention can omit the solution treatment and the aging treatment. The following is a detailed description.

[0076] Initial Melting Step

[0077] The raw materials other than the cerium raw material are melted in a vacuum induction furnace at 1450-1500°C to obtain an initial alloy melt; wherein the cerium raw material is selected from single cerium or ferrocerium alloy. The present invention finds that by first melting the raw materials other than the cerium raw material, and then adding the cerium raw material to melt all at a certain temperature, not only can the solid solution treatment and aging treatment be omitted, but also antibacterial stainless steel with good antibacterial performance can be obtained, and the tensile strength is not reduced, and can even be improved.

[0078] In the present invention, the preliminary melting is carried out under vacuum conditions, and the vacuum degree is less than 0.1 Pa, preferably less than or equal to 0.01 Pa, and more preferably less than or equal to 0.001 Pa. The vacuum induction furnace can adopt a known one in the art. The temperature of the preliminary melting can be 1450-1500°C, for example, 1450°C, 1460°C, 1470°C, 1480°C, 1490°C, 1500°C, and the holding time of the preliminary melting can be 1-4 minutes, preferably 1-3 minutes.

[0079] All raw material melting step

[0080] The initial alloy solution is heated to 1500-1600°C, and single cerium or ferrocerium alloy is added to the initial alloy solution at 1500-1600°C, and the temperature is kept at this temperature for 1-5 minutes to obtain an alloy liquid. This is conducive to obtaining antibacterial stainless steel with good antibacterial and mechanical properties.

[0081] The inventor believes that after rare earth cerium is added, it is very easy to react with oxygen, sulfur and other elements in the steel raw material to form compounds. Since the solid solubility of rare earth cerium in steel is extremely low, most of the rare earth cerium exists in the steel in the form of compounds. The main forms of rare earth cerium in steel include compounds such as CeAlO3, Ce2O2S, CeS and CeO2, most of which are spherical, quasi-spherical and ellipsoidal, with a size of less than 5μm. These compounds remain unchanged in the subsequent processing of stainless steel in terms of morphology, composition and properties. The present invention can achieve the dispersion and uniform distribution of rare earth compounds with a size of less than 5μm in the steel matrix by controlling the addition process of single substance Ce or Ce-Fe alloy; during the rolling process of steel, the solid-solution rare earths concentrated at the grain boundaries and between dendrites gradually refine the grains as the billet is compressed and deformed, and the distribution is more uniform, without the need for separate solution treatment and aging treatment processes.

[0082] According to a specific embodiment of the present invention, the cerium raw material is ferrocerium alloy. Based on the weight of the ferrocerium alloy, the content of cerium element is 10-90wt%, preferably 15-80wt%, and more preferably 20-60wt%.

[0083] This step of the present invention is carried out under vacuum conditions, and the vacuum degree is less than 0.1 Pa, preferably less than or equal to 0.01 Pa, and more preferably less than or equal to 0.001 Pa. The initial alloy solution is preferably heated to 1520-1580°C, and more preferably, heated to 1530-1570°C.

[0084] According to one embodiment of the present invention, the temperature is kept at 1500-1600° C. for 1-5 min, preferably for 1-4 min, and more preferably for 2-3 min.

[0085] Casting steps

[0086] The alloy liquid is poured into an ingot mold or a mold for solidification to obtain a steel ingot or a steel part; the steel ingot or the steel part is the antibacterial stainless steel. Such a steel ingot or steel part has good antibacterial properties and mechanical properties, and no solution treatment and aging treatment are required. The antibacterial stainless steel obtained by the present invention not only has antibacterial properties, but also improves the mechanical properties of the steel.

[0087] In the present invention, the steel ingot can be opened, and the opening method can be forging or rolling. The opening temperature can be 1000-1250°C. After opening, it can be rolled according to the final product specification requirements to obtain billets, plates and profiles that meet the product specification requirements.

[0088] Example 1

[0089] Prepare the raw materials according to the recipe in Table 1.

[0090] The raw materials except the ferrocerium alloy are melted in a vacuum induction furnace at 1470° C. to obtain an initial alloy melt. The vacuum degree in the vacuum induction furnace is less than or equal to 0.001 Pa.

[0091] The initial alloy solution was heated to 1550° C., ferrocerium alloy (the cerium content in the ferrocerium alloy was 30 wt%) was added to the initial alloy solution at 1550° C., and the temperature was maintained for 3 minutes to obtain alloy liquid.

[0092] The alloy liquid is poured into an ingot mold and solidified to obtain a steel ingot; the steel ingot is the antibacterial stainless steel.

[0093] The antibacterial properties and tensile strength of the obtained steel ingots were tested, and the results are shown in Tables 2 and 3.

[0094] Example 2

[0095] The difference between this embodiment and embodiment 1 is that the content of Ce is 0.56wt%. The formula of raw materials is shown in Table 1. The remaining steps and parameters are the same as those in embodiment 1. The test results of the antibacterial property and tensile strength of the obtained steel ingot are shown in Tables 2 and 3.

[0096] Comparative Example 1

[0097] The difference between this comparative example and Example 1 is that the amount of Ce added is 0. The formula of the raw materials is shown in Table 1. The remaining steps and parameters are the same as those in Example 1. The test results of the antibacterial property and tensile strength of the obtained steel ingot are shown in Tables 2 and 3.

[0098] Comparative Example 2

[0099] The difference between this comparative example and Example 1 is that the content of Ce is 0.21wt%. The formula of raw materials is shown in Table 1. The remaining steps and parameters are the same as those in Example 1. The test results of the antibacterial property and tensile strength of the obtained steel ingot are shown in Tables 2 and 3.

[0100] Table 1

[0101]

[0102] Performance evaluation experiment

[0103] The steel ingots (ie, antibacterial stainless steel) obtained in the embodiment and the comparative example were subjected to performance evaluation experiments respectively.

[0104] (I) Antibacterial performance testing:

[0105] According to the standard of “GBT21510-2008 Test Method for Antibacterial Performance of Nano-inorganic Materials”, the antibacterial rate of Escherichia coli and Staphylococcus aureus was tested.

[0106] The calculation formula of antibacterial rate R is:

[0107] R = (AB) / A × 100%;

[0108] Where:

[0109] R is the antibacterial rate, %;

[0110] A is the average number of bacteria recovered after the control sample was in contact with the test bacteria for a certain period of time, cfu / mL;

[0111] B is the average number of recovered bacteria after the test sample has been in contact with the test bacteria for a certain period of time, cfu / mL;

[0112] When testing the antibacterial rate, three samples were tested in each group for each strain, and the average value was taken after testing the three groups.

[0113] The results of the antibacterial properties against Staphylococcus aureus and Escherichia coli are shown in Table 2.

[0114] Table 2

[0115]

[0116] (II) Tensile strength test:

[0117] GB-T228.1-2010 "Metallic materials tensile test Part 1: Room temperature test method" was used for testing. The results are shown in Table 3.

[0118] Table 3

[0119] serial number Tensile strength(MPa) Remark Example 1 730 Average value of 9 samples Example 2 779 Average value of 7 samples Comparative Example 1 584 Average value of 6 samples Comparative Example 2 694 Average value of 7 samples

[0120] In summary, the antibacterial stainless steel of the present invention has good antibacterial properties and its tensile strength is also significantly improved.

[0121] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be conceived by those skilled in the art shall fall within the scope of the present invention.

Claims

1. An antibacterial stainless steel, characterized in that: It has the following composition: C 0.03~0.14wt%; Si 0.35~0.50wt%; Mn 0.70~1.10wt%; S 0.001~0.015wt%; P 0.01~0.06wt%; Cr 18.00~20.00wt%; Ni 7.50~11.00wt%; Mo 0.03~0.50wt%; Cu 0.10~0.35wt%; Ce 0.26~0.66wt%; The balance is Fe and inevitable impurities.

2. The antibacterial stainless steel according to claim 1, characterized in that: It has the following composition: C 0.06~0.14wt%; Si 0.40~0.50wt%; Mn 0.80~1.09wt%; S 0.007~0.015wt%; P 0.03~0.05wt%; Cr 18.00~19.00wt%; Ni 7.80~9.00wt%; Mo 0.04~0.45wt%; Cu 0.15~0.32wt%; Ce 0.27~0.66wt%; The balance is Fe and inevitable impurities.

3. The antibacterial stainless steel according to claim 1, characterized in that: It has the following composition: C 0.09~0.14wt%; Si 0.43~0.50wt%; Mn 0.85~1.02wt%; S 0.009~0.015wt%; P 0.03~0.042wt%; Cr 18.00~18.50wt%; Ni 7.80~8.50wt%; Mo 0.04~0.06wt%; Cu 0.15~0.25wt%; Ce 0.52~0.59wt%; The balance is Fe and inevitable impurities.

4. The antibacterial stainless steel according to claim 1, characterized in that: Its antibacterial rate against Staphylococcus aureus is greater than or equal to 99.5%, and its antibacterial rate against Escherichia coli is greater than or equal to 92.5%.

5. The antibacterial stainless steel according to claim 4, characterized in that: Its antibacterial rate against Staphylococcus aureus reaches 99.83%, and its antibacterial rate against Escherichia coli reaches 99.92%.

6. A method for preparing antibacterial stainless steel according to any one of claims 1 to 5, characterized in that: The steps include: 1) melting raw materials other than the cerium raw material in a vacuum induction furnace or a medium frequency induction furnace at 1450-1500° C. to obtain an initial alloy melt; wherein the cerium raw material is selected from elemental cerium or ferrocerium alloy; 2) heating the initial alloy solution to 1500-1600° C., adding single substance cerium or ferrocerium alloy to the initial alloy solution at 1500-1600° C., and keeping the temperature at this temperature for 1-5 minutes to obtain alloy liquid; 3) pouring the alloy liquid into an ingot mold or a die for solidification to obtain a steel ingot or a steel part; the steel ingot or the steel part is the antibacterial stainless steel.

7. The preparation method according to claim 6, characterized in that: The content of cerium element is 10 to 90 wt % based on the weight of the ferrocerium alloy.

8. The preparation method according to claim 6, characterized in that: In step 2), the temperature is kept at 1500-1600° C. for 1-3 minutes.

9. The preparation method according to claim 6, characterized in that: Solution treatment and aging treatment are not included.

10. The preparation method according to any one of claims 6 to 9, characterized in that: Step 1) and step 2) are carried out under vacuum conditions, and the vacuum degree is less than 0.1Pa.

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