JP2000313940A - Duplex stainless steel material and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a duplex stainless steel material excellent in antibacterial characteristics and resistance to the sticking of marine life, and its manufactur ing method. SOLUTION: The duplex stainless steel material has a composition containing <=0.05% C, <=2.0% Si, <=2.0% Mn, 16-30% Cr, 3.0-9.0% Ni, 0.2-2.0% Mo, 1.0-5.0% Cu, 0.005-0.05% Al, and 0.10-0.35% N and is provided, in its surface, with a Cu ion supply source in which the proportion of Cu to the total of Fe, Cr, Ni, and Cu is made to >=3 atomic %. It is desirable that the Cu ion supply source is a Cu-enriched layer in which major axis is 0.01-0.5 μm and the number of Cu precipitates is made to >=10 pieces for 100 μm2 of the ferritic-phase surface of the steel material or the content of Cu within the region between the surface of the steel material and a position at a depth of 50 Å from the surface is made to >=4 atomic %. This steel can be easily manufactured by subjecting a duplex stainless steel with the above chemical composition to heating at 550-900 deg.C for 0.1-8 hr or to heating up to 850-1,150 deg.C in an oxidizing atmosphere and then applying acid pickling to remove oxide scales from the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a heat storage tank, a wastewater purifying treatment apparatus, a food production apparatus, etc., which require antibacterial properties, or a marine structure, seawater, etc., which require biofouling resistance. The present invention relates to a duplex stainless steel material suitable for a material such as an exchanger and a method for producing the same.

[0002]

2. Description of the Related Art In a heat exchanger or the like that uses marine structures or seawater for cooling, marine organisms such as barnacles and shellfish adhere to and propagate on the steel surface during use, and gaps are formed on the steel surface. This causes problems such as a corrosion accident, a blockage in the pipe, obstruction of the flow of cooling water, and a decrease in heat exchange efficiency.

[0003] As measures to prevent the adhesion of marine organisms, such treatments as electrolytic protection using mild steel, Zn or the like as a sacrificial anode, chlorine injection, sponge ball cleaning, and the like are performed. However, there is an adverse effect such as environmental pollution by Zn and an increase in maintenance cost.

[0004] In addition, it is desired that stainless steel materials used in medical equipment and kitchen equipment have antimicrobial properties as a measure against hospital infection and food poisoning.

As a stainless steel having antibacterial properties, Japanese Patent Laid-Open Publication No. Hei 8-60301 discloses that the Cu concentration of the surface layer is 0.1%.
A martensitic stainless steel having an atomic percentage of 0.2% or more of the Cu concentration of the base steel is disclosed in Japanese Patent Application Laid-Open No. 8-603.
No. 02 discloses an austenitic stainless steel having a surface Cu concentration in a similar range, and Japanese Unexamined Patent Publication No. Hei 8-60303 discloses a ferritic stainless steel having a surface Cu concentration in a similar range. Each of the above publications discloses a method for producing a stainless steel material by alternating electrolytic treatment.

JP-A-9-170053 discloses a ferritic stainless steel containing 0.4 to 3% by weight of Cu, and JP-A-9-176800 discloses a ferrite stainless steel containing 1 to 3% by weight of Cu.
Japanese Patent Application Laid-Open No. 9-195016 discloses a martensitic stainless steel containing 5% by weight of an austenitic stainless steel containing 0.4 to 5% by weight of Cu. In all of these stainless steels, 0.2% by volume or more of Cu-rich phase is precipitated in the matrix.

Japanese Patent Publication No. 1-24206 discloses a steel containing Cu in duplex stainless steel.
The purpose of containing u is to improve corrosion resistance, and no technique relating to antibacterial properties and bioadhesion resistance is disclosed.

[0008]

It is important for a heat exchanger or the like that cools by using an offshore structure or seawater to have pitting corrosion resistance, intergranular corrosion resistance, stress corrosion resistance, and the like. A duplex stainless steel material comprising a ferrite phase and an austenitic phase has excellent strength characteristics and corrosion resistance against seawater, and is therefore frequently used as a material for these structural members. In addition, according to the conventional method, in order to prevent marine organisms such as barnacles and shellfish from adhering to and propagating on the structural members, and to prevent the corrosion resistance and performance of the structure from deteriorating, ancillary work such as cathodic protection and periodic cleaning treatment is performed. In need of. However, these additional operations require enormous costs and man-hours, and their effects are not always sufficient. For this reason, there has been a demand for a method capable of efficiently preventing biological adhesion.

It is an object of the present invention to provide a method for solving such problems, and more specifically, to provide a duplex stainless steel material excellent in antibacterial properties and bio-adhesion resistance and a method for producing the same. It is in.

[0010]

Means for Solving the Problems The present inventors have conducted various studies for the purpose of improving the antibacterial property and bio-adhesion resistance of a duplex stainless steel material, and have obtained the following new findings. .

A. The biofouling resistance is an index of the difficulty of biofouling on the surface of the duplex stainless steel, and is therefore proportional to the antibacterial property, and those having excellent antibacterial properties are considered to have excellent biofouling resistance. When the Cu ions come into contact with the microorganisms attached to the steel surface, the Cu ions reach the cell membrane and are adsorbed by the protein. The adsorbed Cu ions destroy the radicals of protein SH groups, which are constituents of cells,
It exhibits an antibacterial effect that disables the energy metabolism function of microorganisms.

B. However, in order to improve the bioadhesion resistance, it is necessary to supply a Cu ion having a much higher concentration than the Cu ion concentration required for antibacterial resistance. Such a high concentration of C on the surface of duplex stainless steel
As the u-ion source, the surface of the steel material may be provided with a portion containing Cu in which the ratio of Cu to the total of Fe, Cr, Ni and Cu is 3% or more in atomic%.

As the method, a Cu precipitate having a predetermined size is arranged on the surface of the ferrite phase, or a layer containing the above concentration of Cu (hereinafter, also simply referred to as “Cu-enriched layer”) is formed on the surface of the steel material. Preferably, it is provided.

C. Such steel uses a duplex stainless steel containing Cu exceeding the solid solubility limit of the ferrite phase as a material, and is subjected to a heat treatment to expose Cu precipitates on the surface of the steel material, or Cu on the surface layer of
It can be easily manufactured by performing heat treatment and pickling so as to form an enriched layer.

The present invention has been completed on the basis of the above findings, and the gist of the present invention is as described in the following (1) to (3), which is a duplex stainless steel material excellent in antibacterial properties and bioadhesion resistance. And (4) and (5).

(1) C: 0.05% or less by weight%, S
i: 2.0% or less, Mn: 2.0% or less, Cr: 16 to
30%, Ni: 3.0-9.0%, Mo: 0.2-2.
0%, Cu: more than 1.0% and 5.0% or less, Al: 0.0
A duplex stainless steel material containing 0.05 to 0.05% and N: 0.10 to 0.35%, the surface of which is Fe, C
The ratio of Cu to the total of r, Ni and Cu is atomic%
A duplex stainless steel material having excellent antibacterial properties and bio-adhesion resistance, characterized by having a Cu ion supply source of 3% or more.

(2) The Cu ion supply source has a long diameter of 0.01 to 0.5 on at least the ferrite phase surface of the steel material.
(2) The duplex stainless steel material as described in (1) above, wherein the density is 10 or more Cu precipitates per 100 μm ² .

(3) When the Cu ion supply source has a depth of 50 angstrom from the surface of the steel,
(2) The duplex stainless steel material according to the above (1), wherein the material is a Cu-enriched layer in which the ratio of Cu to the total of e, Cr, Ni and Cu is 3% or more in atomic%.

(4) The duplex stainless steel having the chemical composition described in (1) above is subjected to a heat treatment at 550 to 900 ° C. for 0.1 to 8 hours. Manufacturing method for duplex stainless steel.

(5) A duplex stainless steel having the chemical composition described in (1) above is prepared in an oxidizing atmosphere at 850 to 13
The method for producing a duplex stainless steel according to the above (3), wherein the scale is heated to 50 ° C. and then pickled to remove oxide scale on the surface.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The duplex stainless steel material of the present invention and a method for producing the same will be described in detail below. In addition,
Unless otherwise specified, the chemical composition shown below in% means weight%.

Chemical composition of steel: C: C is precipitated as a carbide in the steel, impairing the ductility of the steel material and deteriorating the corrosion resistance. In order to ensure toughness, ductility, and corrosion resistance, the C content is set to 0.
It shall be not more than 05%.

Si: Si is not an essential element, but may be included because it has a function of deoxidizing molten steel and improving the corrosion resistance of steel. Although the above effects can be obtained even with a small amount of Si, it is preferable to contain 0.10% or more to exhibit these effects more remarkably. If the Si content exceeds 2.0%, weldability and workability are impaired, so the content is set to 2.0% or less.

Mn: Mn is not an essential element, but may be contained because it has a function of fixing S as a sulfide and suppressing hot brittleness together with the deoxidizing action of molten steel. Although the above-mentioned effects can be obtained even when Mn is a very small amount, it is preferable to contain 0.50% or more in order to exert these effects more remarkably. If Mn exceeds 2.0%, the corrosion resistance of the steel deteriorates, so the Mn content is set to 2.0% or less.

Cr: Cr has an effect of improving the corrosion resistance of steel and is a very important element. In order to secure good corrosion resistance as seawater resistant steel, it is necessary to contain 16% or more. It is preferably at least 18%. If the Cr content exceeds 30%, the workability and weldability of steel deteriorate. Further, when Cr is excessively contained, it is necessary to increase Ni necessary for obtaining a two-phase structure composed of a ferrite phase and an austenite phase, which increases costs. Therefore Cr
The content is 30% or less. Preferably it is 25% or less.

Ni: In order to improve the mechanical properties, workability and general corrosion resistance of the steel, and to make the steel structure a two-phase structure of austenite / ferrite, Ni is contained in an amount of 3.0% or more. It is preferably at least 4%. If the Ni content exceeds 9.0%, a performance improvement effect commensurate with cost cannot be obtained, so the Ni content is set to 9.0% or less. It is preferably at most 7%.

Mo: Mo is contained in an amount of 0.2% or more to improve the seawater resistance of the steel material. Preferably it is 0.8% or more. If the content exceeds 2.0%, the σ phase precipitates during the heat treatment for precipitating Cu precipitates, and the steel becomes brittle. Therefore, the Mo content is set to 2.0% or less. Preferably 1.5
% Or less.

Cu: Cu is the most important alloying element for exhibiting the antibacterial effect and the anti-biological effect in the duplex stainless steel material of the present invention. The steel material surface of the present invention is provided with a Cu ion supply source of 4% or more in atomic%. Cu ions eluted from the Cu ion source on the surface of steel in contact with atmospheric moisture and seawater suppress the growth and proliferation of fungi such as Escherichia coli and Staphylococcus aureus attached to the surface, thereby providing antibacterial effects and marine life. The effect of preventing adhesion (biological adhesion resistance) is exhibited.

In order to provide the above-mentioned desired concentration of Cu ion source on the steel material surface, the steel contains more than 1.0% of Cu. Preferably it is 1.5% or more. If the Cu content exceeds 5.0%, the production cost is increased, and problems such as cracking during hot rolling and significant embrittlement at around 500 ° C. are caused. Therefore, the upper limit of the Cu content is set to 5.0%. Preferably it is 2.5% or less. N: N is an austenite forming element like Ni. In addition, since it also has the effect of improving the corrosion resistance of the welded portion, 0.10% or more is contained in order to obtain these effects.
If the N content exceeds 0.35%, chromium nitride may precipitate at the welded portion and impair corrosion resistance, so the N content is set to 0.35% or less. Preferably it is 0.20% or less.

Al: Since Al has a deoxidizing effect on molten steel, Al is contained as a deoxidizing element. In order to obtain a sufficient deoxidizing effect, the Al content is set to 0.005% or more. If it exceeds 0.05%, the amount of precipitation as AlN increases, thereby impairing corrosion resistance and deteriorating toughness. Therefore, the Al content is set to 0.05% or less.

[0031] Ca, Zr, rare earth elements: These elements are not essential elements, but they have an effect of improving the hot workability of steel, so that one or more kinds may be contained. However, if it is contained excessively, the toughness may be impaired.
And Zr are preferably 0.01% or less, respectively, and rare earth elements are preferably 0.10% or less.

Nb, Ti, V: These are not essential elements, but one or more of these elements may be contained since they have the effect of further improving the corrosion resistance of steel. However, the effect of improving the corrosion resistance saturates even if it is contained excessively, so that even when it is contained, it is better to make each content 0.05% or less.

The balance is Fe and inevitable impurities.
Among the unavoidable impurities, P impairs the weldability and hot workability of steel. Therefore, the P content is preferably set to 0.03% or less. Further, since S deteriorates the corrosion resistance, ductility and toughness of steel, its content is preferably 0.01% or less.

Cu deposits: As a Cu ion source,
A Cu precipitate and / or a Cu-enriched layer in which the ratio of Cu to the total of Fe, Cr, Ni and Cu is 3% or more in atomic% on the steel surface is preferable.

As the Cu precipitate, it is preferable that a duplex stainless steel material containing a predetermined amount of Cu is subjected to a heat treatment so that Cu atoms in a solid solution are randomly precipitated in the steel or on the steel surface. The Cu precipitate may be composed of only Cu, or may be Ni, which forms an intermetallic compound in addition to Cu,
It may contain Ti, Fe, Si, P or S. Although some of the Cu precipitates are present in the steel and some of them are exposed on the steel surface, the present invention specifies the Cu precipitates exposed on the steel material surface.

Since the solid solubility limit of Cu is smaller in the ferrite phase than in the austenite phase, precipitation of Cu is slightly observed in the austenite phase, but the ferrite phase is preferentially precipitated. The size and shape of the Cu precipitate can be adjusted by the heat treatment temperature or heat treatment time. If the heat treatment is performed at low temperature for a short time, a granular precipitate of about 10 nm is formed, and when the heat treatment is performed for a long time at a high temperature, the precipitate is formed as a rod-shaped precipitate having a major axis of 1 μm or less. The precipitation density defined in the present invention is measured by observing a Cu precipitate precipitated in a ferrite phase on a steel material surface.

The precipitation density of the Cu precipitate specified in the present invention is such that the major axis has a diameter of at least at least at the ferrite phase surface.
It is preferable that the particles in the range of 01 to 0.5 μm are precipitated at a rate of 10 per 100 μm ² . The antimicrobial and bioadhesive properties are more strongly affected by the size than the number of precipitates, and the larger the precipitates, the better the effect of improving antibacterial and bioadhesive properties.

If the major axis is less than 0.01 μm, sufficient antibacterial properties cannot be obtained. On the other hand, in order to obtain a large precipitate having a major axis exceeding 0.5 μm, it is necessary to perform a long-time heat treatment at a high temperature, but there is a problem that the steel is embrittled due to the precipitation of a heterophase described later. Therefore, the size of the Cu precipitate is preferably such that the major axis is 0.5 μm or less.

At least Cu on the surface of the ferrite layer
If the density of the precipitates is less than 10 per 100 μm ^2, sufficient antibacterial properties and bioadhesion resistance cannot be obtained. The size and density of the precipitate in the austenite phase are arbitrary.

The major axis of the Cu precipitate is the major axis obtained by collecting a thin film sample from steel and observing it with a transmission electron microscope. The diameter is the diameter when the shape is spherical or disk, and the length when the shape is rod. Let the length be the major axis. The density of Cu precipitates is the number of Cu precipitates in the ferrite phase existing in 100 μm ^{2 of the} duplex stainless steel.

Cu-enriched layer: C as a Cu ion source
The Cu concentration in the u-enriched layer is determined by the Cu content relative to the sum of Fe, Cr, Ni and Cu in the region from the steel surface to a depth of 50 Å in order to obtain the desired antibacterial and biofouling resistance. The ratio is 3% or more in atomic%. A portion exceeding a depth of 50 angstroms from the surface of the steel material is optional since it does not significantly affect the Cu ion concentration on the surface of the steel material. The atomic ratio of Cu in the Cu-rich layer can be determined by X-ray photoelectron spectroscopy (XPS).

Cu precipitates and Cu as a Cu ion supply source
With the enrichment layer together, a better antibacterial and bioadhesive surface is obtained.

Production method: The duplex stainless steel material of the present invention having excellent antibacterial and bioadhesive properties is obtained by rolling a steel having the above-mentioned chemical composition as a base material and heat-treating it by a known method. A duplex stainless steel having an austenitic structure is used.

When a Cu precipitate is used as a Cu ion supply source, a duplex stainless steel as
Cu heated to 50 to 900 ° C. and held for 0.1 to 8 hours
A precipitation treatment is preferably performed. If the heating temperature is lower than 550 ° C., a desired Cu precipitate cannot be obtained. Preferably it is 600 ° C. or higher. When the heating temperature exceeds 900 ° C,
This is not good because the precipitated Cu is dissolved again. Preferably 8
The temperature is preferably set to 50 ° C. or lower. If the holding time is less than 0.1 hour, the growth of Cu precipitates is insufficient. Therefore, the holding time is preferably set to 0.1 hour or more. If the holding time exceeds 8 hours, the steel is remarkably embrittled by σ phase precipitation, so the holding time is preferably 8 hours or less.

The atmosphere during the Cu deposition treatment is arbitrary, and may be air. As for the cooling method after the precipitation treatment, rapid cooling by water cooling or the like is preferable because there is embrittlement due to slow cooling at around 500 ° C.

When a Cu-enriched layer is provided on the surface as a Cu ion supply source, a duplex stainless steel as a base material is heated to 850 to 1350 ° C. to deposit Fe or Cr on the surface of the steel.
Is generated, and then pickling is performed to dissolve and remove the oxide scale and a part of the base material.
Is preferably electrochemically precipitated and concentrated on the surface of a steel material. The oxidizing atmosphere is preferably air. The pickling is not particularly limited, but a commonly used nitric hydrofluoric acid pickling is preferred. When both a Cu precipitate and a Cu-enriched layer are provided as a Cu ion supply source, it is efficient to perform the above pickling after the Cu deposition treatment.

[0047]

(Example 1) Steels having various chemical compositions shown in Table 1 were melted in a vacuum high-frequency furnace to form a steel ingot, which was hot-rolled into a 6 mm-thick steel plate and heated to 1050 ° C at 20 ° C. After holding for 2 minutes, a solution treatment was performed by cooling with water to prepare a duplex stainless steel sheet having a ferrite-austenite structure as a base material.

[0048]

[Table 1]

These base materials were heated to 800 ° C. in the air, held for 1.5 hours, cooled with water, pickled with a nitric hydrofluoric acid solution, and provided mainly with Cu precipitates as a Cu ion supply source. A treated material was obtained. The thin film samples obtained from the treated materials were observed with a transmission electron microscope, and the density and size of Cu precipitates observed on the ferrite phase surface of each treated material were measured.

The antibacterial test of the treated material was evaluated by the following method. The bacteria used for the test were Escherichia coli IFO 3
301 (Escherichia coli) and Staphylococcus aureus (Staphylococcus aureus). After culturing the two types of bacteria on a common agar medium, they were uniformly dispersed in a normal broth medium diluted 500-fold with sterile purified water to prepare a bacterial solution having a bacterial count of 2.5 × 10 ⁵ cells / ml. A 50 mm square test piece was cut out from each treated material, the surface was polished with # 600 emery paper, and 0.5 ml of each bacterial solution was applied to the surface, and a polyethylene film of the same size as the test piece was placed thereon. After standing at 35 ° C. and a relative humidity of 90% or more for 24 hours, the bacterial solution was wiped off,
The wiped bacterial solution was sprinkled into the diluent. A predetermined amount of the shake-out solution was mixed with a measurement medium, cultured at 37 ° C. for 48 hours, the number of colonies generated was counted, and the number of bacteria was 2.5 × 10 ³
It was judged that those having a number of cells / ml or less had an excellent antibacterial property with a sterilization rate of 99% or more. Table 2 shows the obtained results.

The corrosion resistance was evaluated by immersing in artificial seawater at 30 ° C. for 3 months according to the conditions specified in ASTM D-114152, and measuring the corrosion loss. In addition, length 5
A V-notch is applied to a 5 mm × 10 mm × 5 mm thick test piece, the toughness is measured in accordance with the conditions specified in JIS-Z2242, and the impact value is 20 J / cm ² at 0 ° C.
Those having the above were judged to be excellent in toughness. Table 2 shows the obtained results.

[0052]

[Table 2]

As can be seen from Table 2, on the surfaces of steels 1 to 5, 10 phases of Cu having a thickness of 0.01 to 0.5 μm were formed at a rate of 10/100.
It was deposited at a density of μm ² or more. On the other hand, in steels A and B in which the Cu content was less than the range specified by the present invention, C
The density of u precipitates formed was 10/100
μm ² , and no Cu precipitate was detected in steel E. According to the antibacterial test results, steels 1 to 5 and steel C exhibited excellent antibacterial properties when the number of colonies generated after culturing was 180 or less.
However, in the case of steels A, B and E, the number of bacteria was increased to 1.0 × 10 ⁶ or more, and there was no antibacterial effect. Steel D had a high Mo content, a σ phase was precipitated, the corrosion resistance was reduced, the impact value was low, and the toughness was poor. Steel C has too much Cu content, steel F has A
Since the l content was too large, rusting was observed and the toughness was poor.

(Example 2) Duplex stainless steel having a thickness of 6 mm obtained by hot rolling and annealing the steel 3 described in Example 1 was subjected to a heat treatment at various temperatures in the atmosphere to obtain C.
A steel sheet mainly provided with Cu precipitates as a u ion supply source was produced. The test pieces obtained from these steel sheets were examined for the state of Cu precipitation on the ferrite phase surface, antibacterial properties, corrosion resistance and toughness in the same manner as described in Example 1. The results are shown in Table 3.

[0055]

[Table 3]

As can be seen from Table 3, the test specimen having the heating temperature within the preferred range had a Cu precipitate having a desired precipitation density, and had good antibacterial properties, corrosion resistance and toughness. Those with large precipitates were particularly excellent in antibacterial properties. On the other hand, the test piece heat-treated at 500 ° C. or 1000 ° C. had poor Cu precipitation and poor antibacterial properties and toughness.

Example 3 The steel 3 described in Example 1 was hot-rolled, pickled, and cold-rolled into a cold-rolled steel sheet having a thickness of 1 mm, and heat-treated at various temperatures and times in the atmosphere. , 1
Pickling with a mixed acid solution of 0% nitric acid and 2% hydrofluoric acid is performed, and various concentrations of C
A test piece provided with a u-enriched layer was obtained. The state of Cu enrichment on the surfaces of these test pieces was investigated by X-ray photoelectron spectroscopy (XPS). Further, the antibacterial property of each test piece was investigated in the same manner as described in Example 1. Table 4 shows the obtained results.

[0058]

[Table 4]

As can be seen from Table 4, those heat-treated under preferable conditions had a desired Cu-enriched layer and had good antibacterial properties. Those subjected to precipitation treatment under unfavorable heat treatment conditions had poor Cu enrichment and poor antibacterial properties.

The test pieces similar to test numbers 3, 5, and 7 in Example 1 above, the test pieces in which no Cu precipitate was detected as in test number 26 described in Example 2, and the test pieces In the same manner as described in Test Nos. 33 and 36 of No. 3, test pieces having different Cu concentrations in the Cu-enriched layer were immersed in seawater for 3 months on the quay, and the adhesion of barnacles was observed. In the same test pieces as Test Nos. 3, 5, and 33, adhesion of barnacles was not recognized, and good bioadhesion resistance was shown. However, trial number 7, 26
Barnacles adhered to the same test specimens as in Nos. 36 and 36, and the bioadhesion resistance was poor.

[0061]

The duplex stainless steel material of the present invention is excellent in antibacterial properties and bio-adhesion resistance, and is also excellent in corrosion resistance. Excellent performance can be achieved when used as a material for water storage tanks or heat exchangers using seawater. Further, since the steel sheet of the present invention can be easily manufactured, it is extremely useful in industry.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshio Tarutani 4-5-33 Kitahama, Chuo-ku, Osaka Sumitomo Metal Industries, Ltd. F-term (reference) 4K053 PA03 PA12 QA01 RA16 RA17 TA02 TA03 TA04 TA16 TA24

Claims (5)

[Claims] 1. C: 0.05% or less by weight%, Si:
2.0% or less, Mn: 2.0% or less, Cr: 16 to 30
%, Ni: 3.0 to 9.0%, Mo: 0.2 to 2.0
%, Cu: more than 1.0% and 5.0% or less, Al: 0.00
A duplex stainless steel material containing 5 to 0.05% and N: 0.10 to 0.35%, the surface of which is Fe, Cr,
The ratio of Cu to the total of Ni and Cu is 3 in atomic%.
A duplex stainless steel material having excellent antibacterial properties and bio-adhesion resistance, characterized by having a Cu ion supply source of at least 0.1%. 2. The method according to claim 1, wherein the Cu ion supply source has a major axis of at least 0.01 to 0.5 μm on at least the ferrite phase surface of the steel material.
And a density of 10 or more C per 100 μm ²
The duplex stainless steel material according to claim 1, wherein the duplex stainless steel material is a u-precipitate. 3. The method according to claim 1, wherein the Cu ion supply source comprises Fe, C in a region having a depth from the steel material surface to a depth of 50 Å.
The ratio of Cu to the total of r, Ni and Cu is atomic%
2. The duplex stainless steel material according to claim 1, wherein the Cu-enriched layer is 3% or more. 3. 4. The antibacterial property according to claim 2, wherein the duplex stainless steel having the chemical composition according to claim 1 is subjected to heat treatment at 550 to 900 ° C. for 0.1 to 8 hours. A method for manufacturing duplex stainless steel with excellent bioadhesion resistance. 5. A duplex stainless steel having the chemical composition according to claim 1, which is heated to 850 to 1350 ° C. in an oxidizing atmosphere.
The method for producing a duplex stainless steel material having excellent antibacterial properties and bio-adhesion resistance according to claim 3, wherein the surface is oxidized and then pickled to remove oxide scale on the surface.