WO2022202507A1

WO2022202507A1 - Stainless steel material and method for manufacturing same, and antibacterial/antiviral member

Info

Publication number: WO2022202507A1
Application number: PCT/JP2022/011738
Authority: WO
Inventors: 明訓河野; 一幸景岡
Original assignee: 日鉄ステンレス株式会社
Priority date: 2021-03-26
Filing date: 2022-03-15
Publication date: 2022-09-29
Also published as: KR20230076838A; EP4317481A1; MX2023011015A; US20240060151A1; TWI814284B; TW202242161A; CN116368246A

Abstract

This stainless steel material has an ε-Cu phase exposed on the surface. The ε-Cu phase in the surface of the stainless steel material has an area fraction of 0.1-4.0%, an average particle size of 10-300 nm, and a maximum inter-particle distance of 100-1000 nm.

Description

Stainless steel material, manufacturing method thereof, and antibacterial/antiviral member

The present invention relates to a stainless steel material, its manufacturing method, and an antibacterial/antiviral member.

Because of its excellent corrosion resistance, stainless steel is used in a wide range of applications, including kitchen equipment, home appliances, medical equipment, interior building materials, and transportation equipment. use is also increasing. In recent years, there has been a growing concern about the adverse effects on the human body caused by the propagation of bacteria and attachment of viruses. Antibacterial and antiviral properties are also required for various members used for goods and transportation equipment.

Since Ag, Cu, and the like are known as metal elements having antibacterial and antiviral properties, stainless steel materials to which antibacterial and antiviral properties are imparted by adding these metal elements have been proposed.
For example, Patent Document 1 contains C: 0.1% by weight or less, Si: 2% by weight or less, Mn: 2% by weight or less, Cr: 10 to 30% by weight, and Cu: 0.4 to 3% by weight. , a ferritic stainless steel material having excellent antibacterial properties in which a Cu-rich phase (ε-Cu phase) is precipitated in a matrix at a rate of 0.2% by volume or more has been proposed. This ferritic stainless steel material contains C: 0.1% by weight or less, Si: 2% by weight or less, Mn: 2% by weight or less, Cr: 10 to 30% by weight, and Cu: 0.4 to 3% by weight. It is produced by cold-rolling stainless steel, final annealing, and aging treatment at 500 to 800° C. to precipitate a Cu-rich phase (ε-Cu phase) to 0.2% by volume or more.

Further, in Patent Document 2, C: 0.1% by weight or less, Si: 2% by weight or less, Mn: 5% by weight or less, Cr: 10 to 30% by weight, Ni: 5 to 15% by weight, Cu: 1 It has a composition containing 0 to 5.0% by weight, and has excellent antibacterial properties in which the second phase (ε-Cu phase) mainly composed of Cu is dispersed in the matrix at a rate of 0.2% by volume or more. Austenitic stainless steel materials have been proposed. This austenitic stainless steel material contains C: 0.1% by weight or less, Si: 2% by weight or less, Mn: 5% by weight or less, Cr: 10 to 30% by weight, Ni: 5 to 15% by weight, and Cu: 1.0% by weight. It is produced by subjecting austenitic stainless steel containing 0 to 5.0 wt.

JP-A-9-170053 JP-A-9-176800

In the stainless steel materials described in Patent Documents 1 and 2, the distribution state of the ε-Cu phase on the surface is not properly controlled, so the desired antibacterial properties cannot be obtained or the antibacterial properties tend to be lost early. Sometimes.
Also, since viruses are smaller than bacteria, if the virus adheres between the ε-Cu phases on the surface, little antiviral properties may be obtained.

The purpose of the present invention is to provide a stainless steel material that can maintain antibacterial and antiviral properties for a long period of time, a method for manufacturing the same, and an antibacterial/antiviral member.

The inventors of the present invention have made intensive studies to solve the above problems, and as a result, the distribution state of the ε-Cu phase on the surface of the stainless steel material (particularly, the area ratio of the ε-Cu phase on the surface, the ε-Cu The inventors have found that the average particle size of the phase and the maximum interparticle distance of the ε-Cu phase) are closely related to the antibacterial and antiviral properties and their durability, and have completed the present invention.

That is, the present invention has an ε-Cu phase exposed on the surface,
The ε-Cu phase on the surface is a stainless steel material having an area ratio of 0.1 to 4.0%, an average particle diameter of 10 to 300 nm, and a maximum interparticle distance of 100 to 1000 nm.

Further, in the present invention, on the mass basis, C: 0.10% or less, Si: 4.00% or less, Mn: 2.00% or less, P: 0.050% or less, S: 0.030% or less, Slab having a ferritic composition containing Ni: 4.00% or less, Cr: 10.00 to 32.00%, Cu: 0.40 to 4.00%, the balance being Fe and impurities, or mass basis C: 0.12% or less, Si: 4.00% or less, Mn: 6.00% or less, P: 0.050% or less, S: 0.030% or less, Ni: 4.00-20. 00%, Cr: 10.00 to 32.00%, Cu: 2.00 to 6.00%, and the balance being Fe and impurities. In the hot rolling step to obtain, the finish hot rolling finish temperature is 700 to 900 ° C. when the slab composition is the ferrite system, and the finish hot rolling finish temperature is 850 to 1050 ° C. when the slab composition is the austenite system. process and
a cooling step of cooling the hot-rolled material obtained in the hot-rolling step to a temperature between 900 and 500°C at an average cooling rate of 0.2 to 5°C/sec;
and a heat treatment step of heating the hot-rolled material cooled in the cooling step at 750 to 850° C. for 4 hours or longer.

Further, the present invention is an antibacterial/antiviral member containing the stainless steel material.

According to the present invention, it is possible to provide a stainless steel material capable of maintaining antibacterial and antiviral properties for a long period of time, a method for producing the same, and an antibacterial/antiviral member.

1 is a schematic diagram of the surface of a typical stainless steel material of the present invention; FIG.

The present invention is a stainless steel material having an ε-Cu phase exposed on the surface. The ε-Cu phase has an area ratio of 0.1 to 4.0%, an average particle diameter of 10 to 300 nm, and a maximum interparticle distance of 100 to 1000 nm.
FIG. 1 shows a schematic diagram of the surface of a typical stainless steel material of the present invention.
As shown in FIG. 1, the stainless steel material 10 has an ε-Cu phase 11 exposed on the surface of the parent phase. A passive film 12 is formed on the surface of the matrix phase where the ε-Cu phase 11 is not exposed.

By exposing the ε-Cu phase 11 on the surface of the parent phase, Cu ions can be eluted from the ε-Cu phase 11 when water contacts the surface of the stainless steel material 10 . For example, when a human hand touches the surface of the stainless steel material 10, Cu ions can be eluted from the ε-Cu phase 11 by the moisture of the hand. Therefore, even if bacteria adhere to the surface, they can be sterilized, and even if viruses adhere to the surface, they can be inactivated and eventually killed.
Moreover, since the passivation film 12 is formed on the surface of the matrix phase where the ε-Cu phase 11 is not exposed, corrosion resistance is also good.

The composition of the stainless steel material of the present invention is not particularly limited, but C: 0.12% or less, Si: 4.00% or less, Mn: 6.00% or less, P: 0.050% or less, S: 0.05% or less. 030% or less, Ni: 20.00% or less, Cr: 10.00 to 32.00%, Cu: 0.40 to 6.00%, and the balance being Fe and impurities.
Here, in this specification, "%" for components means "% by mass" unless otherwise specified.

Although the metallographic structure of the stainless steel material of the present invention is not particularly limited, it is preferably ferritic or austenitic.
Hereinafter, embodiments of the present invention will be specifically described with reference to ferritic stainless steel materials and austenitic stainless steel materials as examples. The present invention is not limited to the following embodiments, and modifications and improvements can be made to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. are also within the scope of the present invention.

(Embodiment 1)
The ferritic stainless steel material according to Embodiment 1 of the present invention contains C: 0.10% or less, Si: 4.00% or less, Mn: 2.00% or less, P: 0.050% or less, and S: 0.05% or less. 030% or less, Ni: 4.00% or less, Cr: 10.00-32.00%, Cu: 0.40-4.00%, and the balance being Fe and impurities.
Here, in this specification, the term "steel material" means materials of various types such as steel plates. In addition, the term “steel plate” is a concept including a steel strip. Further, the term "impurities" refers to components mixed in by various factors in the manufacturing process, such as raw materials such as ores and scraps, during the industrial production of stainless steel materials, and is permissible within a range that does not adversely affect the present invention. means to be

Further, the ferritic stainless steel material according to Embodiment 1 of the present invention has Nb: 1.00% or less, Ti: 0.60% or less, V: 1.00% or less, W: 2.00% or less, Mo: 3.00% or less, N: 0.050% or less, Sn: 0.50% or less, Al: 5.00% or less, Zr: 0.50% or less, Co: 0.50% or less, B: 0.50% or less. 010% or less, Ca: 0.10% or less, and REM: 0.20% or less.
Each component will be described in detail below.

<C: 0.10% or less>
C is an effective element for improving the strength of the ferritic stainless steel material and uniformly dispersing and precipitating the ε-Cu phase by forming Cr carbide. However, if the C content is too high, the material becomes hard and workability deteriorates, and in addition, sensitization occurs when subjected to thermal effects such as welding, and the corrosion resistance of ferritic stainless steel deteriorates. Therefore, the upper limit of the C content is controlled to 0.10%, preferably 0.06%, more preferably 0.04%, still more preferably 0.03%. On the other hand, the lower limit of the C content is not particularly limited, but is preferably 0.001%, more preferably 0.003%, and still more preferably 0.005%.

<Si: 4.00% or less>
Si is an element that forms a ferrite phase (α phase), and is an element that is effective in improving the corrosion resistance and strength of ferritic stainless steel materials. However, if the content of Si is too high, the workability of the ferritic stainless steel decreases due to hardening. Therefore, the upper limit of the Si content is controlled to 4.00%, preferably 2.00%, more preferably 1.50%, still more preferably 1.00%. On the other hand, the lower limit of the Si content is not particularly limited, but is preferably 0.01%, more preferably 0.05%, and still more preferably 0.10%.

<Mn: 2.00% or less>
Mn is an element that improves the heat resistance of ferritic stainless steel. However, if the Mn content is too high, the corrosion resistance of the ferritic stainless steel will be lowered. Moreover, since Mn is an austenite phase (γ phase)-forming element, it forms a γ phase (a martensite phase at room temperature) at high temperatures, thereby deteriorating the workability of ferritic stainless steel materials. Therefore, the upper limit of the Mn content is controlled to 2.00%, preferably 1.50%, more preferably 1.20%, still more preferably 1.00%. On the other hand, the lower limit of the Mn content is not particularly limited, but is preferably 0.01%, more preferably 0.05%, and still more preferably 0.10%.

<P: 0.050% or less>
If the content of P is too high, the corrosion resistance and workability of the ferritic stainless steel will be lowered. Therefore, the upper limit of the P content is controlled to 0.050%, preferably 0.040%, more preferably 0.030%. On the other hand, the lower limit of the P content is not particularly limited. 010%.

<S: 0.030% or less>
If the S content is too high, the hot workability is lowered, the manufacturability of the ferritic stainless steel is lowered, and the corrosion resistance is also adversely affected. Therefore, the upper limit of the S content is controlled to 0.030%, preferably 0.020%, more preferably 0.010%. On the other hand, the lower limit of the S content is not particularly limited. 0003%.

<Ni: 4.00% or less>
Ni is an element that improves the corrosion resistance of ferritic stainless steel. However, Ni, like Mn, is an austenite phase (γ phase)-forming element. sexuality declines. In addition, since Ni is an expensive element, it also leads to an increase in manufacturing costs. Therefore, the upper limit of the Ni content is controlled to 4.00%, preferably 2.00%, more preferably 1.00%, still more preferably 0.60%. On the other hand, the lower limit of the Ni content is not particularly limited, but is preferably 0.005%, more preferably 0.01%, and still more preferably 0.03%.

<Cr: 10.00 to 32.00%>
Cr is an important element for maintaining the corrosion resistance of ferritic stainless steel. However, if the Cr content is too high, the refining cost will increase, and solid-solution strengthening will harden the steel, thereby degrading the workability of the ferritic stainless steel material. Therefore, the upper limit of the Cr content is controlled to 32.00%, preferably 22.00%, more preferably 20.00%, still more preferably 18.00%. On the other hand, if the Cr content is too small, sufficient corrosion resistance cannot be obtained. Therefore, the lower limit of the Cr content is controlled to 10.00%, preferably 14.00%, more preferably 15.00%, still more preferably 16.00%.

<Cu: 0.40 to 4.00%>
Cu is an element necessary for precipitating the ε-Cu phase, which provides antibacterial and antiviral properties. Cu is also an element that improves the workability of ferritic stainless steel. In order to obtain such effects, the lower limit of the Cu content is controlled to 0.40%, preferably 0.70%, more preferably 1.00%, still more preferably 1.30%. On the other hand, if the Cu content is too high, the corrosion resistance of the ferritic stainless steel material is lowered, and a low-melting-point phase is formed during casting, resulting in poor hot workability. Therefore, the upper limit of the Cu content is controlled to 4.00%, preferably 3.00%, more preferably 2.00%, still more preferably 1.70%.

<Nb: 1.00% or less>
Nb is an element that exhibits the effect of forming precipitates and uniformly precipitating the ε-Cu phase around them, and is added as necessary. However, if the Nb content is too high, the workability of the ferritic stainless steel material will deteriorate. Therefore, the upper limit of the Nb content is controlled to 1.00%, preferably 0.80%, more preferably 0.60%, still more preferably 0.55%. On the other hand, the lower limit of the Nb content is not particularly limited, but from the viewpoint of obtaining the effect of Nb, it is preferably 0.05%, more preferably 0.10%, still more preferably 0.20%, and particularly preferably 0.25%.

<Ti: 0.60% or less>
Ti, like Nb, is an element that forms precipitates and exhibits the effect of uniformly precipitating the ε-Cu phase around them, and is added as necessary. However, if the content of Ti is too high, it causes surface defects, leading to deterioration in quality and deterioration in workability of the ferritic stainless steel material. Therefore, the upper limit of the Ti content is controlled to 0.60%, preferably 0.30%. On the other hand, the lower limit of the Ti content is not particularly limited, but from the viewpoint of obtaining the effect of Ti, it is preferably 0.01%, more preferably 0.03%.

<V: 1.00% or less>
V, like Nb and Ti, is an element that exhibits the effect of forming precipitates and uniformly precipitating the ε-Cu phase around them, and is added as necessary. However, if the V content is too high, it causes surface flaws, resulting in deterioration of quality and deterioration in workability of the ferritic stainless steel material. Therefore, the upper limit of the V content is controlled to 1.00%, preferably 0.50%. On the other hand, the lower limit of the V content is not particularly limited, but from the viewpoint of obtaining the effect of V, it is preferably 0.01%, more preferably 0.03%.

<W: 2.00% or less>
W, like Nb, Ti, and V, is an element that exhibits the effect of forming precipitates and uniformly precipitating the ε-Cu phase around them, and is added as necessary. However, if the W content is too high, it causes surface flaws, resulting in deterioration in quality and deterioration in workability of the ferritic stainless steel material. Therefore, the upper limit of the W content is controlled to 2.00%, preferably 1.00%. On the other hand, the lower limit of the W content is not particularly limited, but from the viewpoint of obtaining the effect of W, it is preferably 0.01%, more preferably 0.03%.

<Mo: 3.00% or less>
Mo is an element that improves the corrosion resistance of ferritic stainless steel materials and is added as necessary. However, if the Mo content is too high, the manufacturing cost will increase. Therefore, the upper limit of the Mo content is controlled to 3.00%, preferably 2.00%, more preferably 1.50%, still more preferably 1.00%. On the other hand, the lower limit of the Mo content is not particularly limited, but from the viewpoint of obtaining the effect of Mo, it is preferably 0.01%, more preferably 0.03%, and still more preferably 0.10%.

<N: 0.050% or less>
N, like Mo, is an element that improves the corrosion resistance of ferritic stainless steel materials and is added as necessary. However, if the N content is too high, the workability of the ferritic stainless steel material is reduced due to hardening. Therefore, the upper limit of the N content is controlled to 0.050%, preferably 0.030%, more preferably 0.025%, still more preferably 0.015%. On the other hand, the lower limit of the N content is not particularly limited, but from the viewpoint of obtaining the effect of N, it is preferably 0.001%, preferably 0.003%.

<Sn: 0.50% or less>
Sn, like Mo and N, is an element that improves the corrosion resistance of ferritic stainless steel materials, and is added as necessary. However, if the Sn content is too high, the manufacturing cost will increase. Therefore, the upper limit of the Sn content is controlled to 0.50%, preferably 0.30%. On the other hand, the lower limit of the Sn content is not particularly limited, but from the viewpoint of obtaining the effect of Sn, it is preferably 0.01%, more preferably 0.03%.

<Al: 5.00% or less>
Al is an element used for deoxidation in the refining process and is added as necessary. Al is also an element that improves the corrosion resistance and oxidation resistance of ferritic stainless steel. However, if the Al content is too high, the amount of inclusions produced increases and the quality deteriorates. Therefore, the upper limit of the Al content is 5.00%, preferably 3.00%, more preferably 2.00%, still more preferably 1.00%. On the other hand, the lower limit of the Al content is not particularly limited, but from the viewpoint of obtaining the effect of Al, it is preferably 0.01%, more preferably 0.05%.

<Zr: 0.50% or less>
Zr, like Al, is an element that improves the oxidation resistance of ferritic stainless steel materials, and is added as necessary. However, if the Zr content is too high, it will lead to an increase in manufacturing costs. Therefore, the upper limit of the Zr content is controlled to 0.50%, preferably 0.30%. On the other hand, the lower limit of the Zr content is not particularly limited, but from the viewpoint of obtaining the effect of Zr, it is preferably 0.01%, more preferably 0.03%.

<Co: 0.50% or less>
Co, like Al and Zr, is an element that improves the oxidation resistance of ferritic stainless steel materials, and is added as necessary. However, if the Co content is too high, the manufacturing cost will increase. Therefore, the upper limit of the Co content is controlled to 0.50%, preferably 0.30%. On the other hand, the lower limit of the Co content is not particularly limited, but from the viewpoint of obtaining the effect of Co, it is preferably 0.01%, more preferably 0.03%.

<B: 0.010% or less>
B is an element that improves the hot workability of ferritic stainless steel materials, and is added as necessary. B is also an element that improves the secondary workability of ferritic stainless steel materials by strengthening grain boundaries. However, if the content of B is too high, the weldability and fatigue strength will be lowered. Therefore, the upper limit of the B content is controlled to 0.010%, preferably 0.070%. On the other hand, the lower limit of the content of B is not particularly limited, but from the viewpoint of obtaining the effect of B, it is preferably 0.001%, more preferably 0.002%.

<Ca: 0.10% or less>
Ca, like B, is an element that improves the hot workability of ferritic stainless steel materials, and is added as necessary. Ca is also an element that forms sulfides and suppresses grain boundary segregation of S, thereby improving grain boundary oxidation resistance. However, if the Ca content is too high, workability is lowered. Therefore, the upper limit of the Ca content is controlled to 0.10%, preferably 0.05%. On the other hand, the lower limit of the Ca content is not particularly limited, but is preferably 0.001%, more preferably 0.003%, from the viewpoint of obtaining the effect of Ca.

<REM: 0.20% or less>
REM (rare earth element), like B and Ca, is an element that improves the hot workability of ferritic stainless steel materials, and is added as necessary. REM is also an element that improves corrosion resistance by forming sulfides that are difficult to elute and suppressing the formation of MnS, which is a starting point for corrosion. However, if the REM content is too high, it will lead to an increase in manufacturing costs. Therefore, the upper limit of the REM content is controlled to 0.20%, preferably 0.10%. On the other hand, the lower limit of the REM content is not particularly limited, but is preferably 0.001%, more preferably 0.01%, from the viewpoint of obtaining the effect of REM.
In this specification, "REM" is a general term for two elements, scandium (Sc) and yttrium (Y), and fifteen elements (lanthanoids) from lanthanum (La) to lutetium (Lu). These may be used alone or as a mixture of two or more.

Next, the features of the ε-Cu phase exposed on the surface of the ferritic stainless steel material according to Embodiment 1 of the present invention will be described in detail.

<Area ratio: 0.1 to 4.0%>
As the area ratio of the ε-Cu phase exposed to the surface increases, the amount of Cu ions eluted increases, so antibacterial and antiviral properties can be enhanced. The area fraction of this ε-Cu phase mainly depends on the crystal structure and the Cu content. Therefore, considering the Cu content in the ferritic stainless steel material, the upper limit of the area ratio of the ε-Cu phase is 4.0%, preferably 2.0%, more preferably 1.9%, and even more preferably controlled at 1.8%. On the other hand, the lower limit of the area ratio of the ε-Cu phase is controlled to 0.1%, preferably 0.3%, more preferably 0.6% from the viewpoint of ensuring antibacterial and antiviral properties.

Here, the "area ratio of the ε-Cu phase exposed on the surface" in this specification can be calculated by observing the surface of the stainless steel material with a TEM (transmission electron microscope). Specifically, after photographing TEM images at three or more randomly selected locations on the surface of the stainless steel material, the TEM images are image-analyzed to measure the area of the ε-Cu phase. is divided by the visual field area, the "area ratio of the ε-Cu phase exposed on the surface" can be calculated. Although the field of view area is not particularly limited, it is preferably 10 μm ² or more in total of the photographed locations.

<Average particle size: 10 to 300 nm>
As the average particle size of the ε-Cu phase exposed on the surface is larger, Cu ions can be eluted over a longer period of time, thereby improving the durability of the antibacterial and antiviral properties. However, if the average particle size of the ε-Cu phase is too large, the distance between particles of the ε-Cu phase exposed on the surface tends to increase. Therefore, when bacteria or viruses adhere between the particles of the ε-Cu phase exposed on the surface, sufficient antibacterial and antiviral properties may not be obtained. Therefore, the upper limit of the average particle size of the ε-Cu phase is controlled to 300 nm, preferably 250 nm, more preferably 200 nm. On the other hand, the lower limit of the average particle size of the ε-Cu phase is controlled to 10 nm, preferably 30 nm, more preferably 50 nm, from the viewpoint of ensuring the elution sustainability of Cu ions.

Here, the "average particle size of the ε-Cu phase exposed on the surface" in this specification can be calculated by observing the surface of the stainless steel material with a TEM (transmission electron microscope). Specifically, after photographing TEM images at three or more randomly selected locations on the surface of the stainless steel material, the TEM images are image-analyzed to obtain the circle-equivalent diameter of the ε-Cu phase, and the average value is calculated as " The average particle size of the ε-Cu phase exposed on the surface”.

<Maximum distance between particles: 100 to 1000 nm>
In general, the size of bacteria is 0.5-3 μm, whereas the size of viruses is very small, 10-200 nm. Therefore, if the maximum interparticle distance of the ε-Cu phase exposed on the surface is too large, sufficient antiviral properties cannot be obtained particularly when a virus adheres between the particles of the ε-Cu phase exposed on the surface. Sometimes. Therefore, the upper limit of the maximum interparticle distance of the ε-Cu phase is controlled to 1000 nm, preferably 800 nm, more preferably 500 nm. On the other hand, the smaller the maximum interparticle distance of the ε-Cu phase exposed on the surface, the better the antibacterial and antiviral properties. Considering the growth process of the ε-Cu phase due to heat treatment, the lower limit of the maximum distance between grains of the ε-Cu phase is thought to be 100 nm. Therefore, the lower limit of the maximum interparticle distance of the ε-Cu phase is controlled to 100 nm, preferably 150 nm, more preferably 200 nm.

Here, the "maximum interparticle distance of the ε-Cu phase exposed on the surface" in this specification can be calculated by observing the surface of the stainless steel material with a TEM (transmission electron microscope). Specifically, after photographing TEM images at three or more randomly selected locations on the surface of the stainless steel material, the TEM images are image-analyzed, and the position of the center of gravity (generating point) of the ε-Cu phase is obtained, followed by Voronoi division. do. Next, the distance between the centers of gravity of the ε-Cu phase in the adjacent Voronoi regions is measured as the inter-particle distance, and the maximum value can be taken as the "maximum inter-particle distance of the ε-Cu phase exposed on the surface".

The ferritic stainless steel material according to Embodiment 1 of the present invention preferably has a Vickers hardness of 160 Hv or less. By controlling the Vickers hardness in such a manner, workability can be ensured, so that it can be used for various purposes.
Although the lower limit of Vickers hardness is not particularly limited, it is generally 100Hv.
Here, the "Vickers hardness" in this specification can be measured according to JIS Z2244:2009. In the measurement of Vickers hardness, the measurement load is 10 kg, the measurement is performed at 5 or more randomly selected locations, and the average value is taken as the result of Vickers hardness.

The ferritic stainless steel material according to Embodiment 1 of the present invention preferably has an antibacterial activity value of 2.0 or more in an antibacterial test conforming to JIS Z2801:2010. With such an antibacterial activity value, high antibacterial properties can be objectively ensured.
Here, the "antibacterial test" in this specification conforms to JIS Z2801:2010 and is performed using Staphylococcus aureus as bacteria.

The ferritic stainless steel material according to Embodiment 1 of the present invention preferably has an antiviral activity value of 2.0 or more in an antiviral test conforming to ISO 21702:2019. With such an antiviral activity value, high antiviral properties can be objectively guaranteed.
Here, the "antiviral test" in the present specification is performed in accordance with ISO 21702:2019 using influenza A virus as the virus.

Although the type of the ferritic stainless steel material according to Embodiment 1 of the present invention is not particularly limited, it is preferably a hot-rolled material or a cold-rolled material.
In the case of hot-rolled material, its thickness is generally 3 mm or more. In the case of cold-rolled material, the thickness is generally less than 3 mm.

The ferritic stainless steel material according to Embodiment 1 of the present invention can be manufactured by a method including a hot rolling process, a cooling process, and a heat treatment process.
The hot-rolling step is a step of hot-rolling a slab having the above composition to obtain a hot-rolled material. Specifically, a hot-rolled material is obtained by subjecting a slab having the above composition to rough rolling, followed by finish hot rolling. This hot-rolled material may be wound into a coil.
The slab having the above composition is not particularly limited, but can be obtained, for example, by melting stainless steel having the above composition and forging or casting.

Finish hot rolling is carried out so that the finishing temperature of finish hot rolling is 700 to 900°C. By controlling the final hot rolling temperature within this temperature range, a small amount of fine "seeds" of the ε-Cu phase can be easily precipitated uniformly in the cooling process after the final hot rolling. As a result, by growing the ε-Cu phase in the heat treatment process, the distribution of the ε-Cu phase on the surface can be controlled as described above. On the other hand, if the finish hot rolling finish temperature is lower than 700° C., fine "seeds" of the ε-Cu phase are not sufficiently precipitated in the cooling step after the finish hot rolling finish. As a result, when the ε-Cu phase is grown in the heat treatment process, the average particle size and maximum inter-particle distance of the ε-Cu phase on the surface become too large. On the other hand, if the finish hot rolling finish temperature exceeds 900°C, the structure becomes coarse and the workability and toughness are lowered.
Other conditions in the hot rolling process may be appropriately set according to the composition of the slab, and are not particularly limited.

The cooling step is a step for precipitating fine “seeds” of the ε-Cu phase. °C by cooling. By gently cooling under such conditions, a small amount of fine "seeds" of the ε-Cu phase can be uniformly precipitated in the precipitation temperature range (900 to 500° C.) of the ε-Cu phase. Since the fine "seeds" of the ε-Cu phase preferentially grow in the heat treatment process, relatively large ε-Cu phases are uniformly dispersed. As a result, the distribution state of the ε-Cu phase on the surface can be controlled as described above. From the viewpoint of stably obtaining such effects, the average cooling rate is preferably 1 to 5° C./second, more preferably 2 to 4° C./second. In contrast, when cooling between 900 and 500° C. at an average cooling rate greater than 5° C./sec, fine “seeds” of the ε-Cu phase are not sufficiently precipitated. As a result, when the ε-Cu phase is grown in the heat treatment process, the average particle size and maximum inter-particle distance of the ε-Cu phase on the surface become too large. Further, when cooling between 900 and 500° C. at an average cooling rate of less than 0.2° C./sec, the amount of fine “seeds” of the ε-Cu phase is increased. As a result, a large amount of relatively small ε-Cu phase precipitates in the heat treatment process.
In addition, the cooling method in the cooling step is not particularly limited, and a method known in the art can be used. For example, just by putting the hot-rolled material wound into a coil into a heat insulating box, it is possible to gently cool the material under the above-mentioned cooling conditions by recuperation. Also, the cooling temperature can be finely adjusted by controlling the amount of gas (for example, Ar gas) supplied to the heat insulating box.

The heat treatment step is a step of growing fine ε-Cu phase “seeds” precipitated in the cooling step, and is performed by heating the hot-rolled material cooled in the cooling step at 750 to 850° C. for 4 hours or more. . By performing the heat treatment under such conditions, it becomes possible to control the distribution state of the ε-Cu phase on the surface as described above. From the viewpoint of stably obtaining such effects, the heating time is preferably 6 to 48 hours, more preferably 8 to 36 hours. On the other hand, when the heating temperature is less than 750° C. or the heating time is less than 4 hours, the fine “seeds” of the ε-Cu phase do not grow sufficiently, and the average grains of the ε-Cu phase The diameter becomes too small. Moreover, when the heating temperature exceeds 850° C., the ε-Cu phase dissolves in the matrix phase.

After the heat treatment step, a surface layer removing step of pickling and/or polishing may be further performed, if necessary. By carrying out the surface layer removing step, it is possible to remove scales and a Cr-poor layer formed on the surface.
The thickness of the surface layer to be removed in the surface layer removing step is not particularly limited and may be appropriately adjusted according to the composition of the slab. For example, when removing a Cr-poor layer, it is preferable to remove a surface layer having a thickness of 10 μm or more.

When the ferritic stainless steel material is a cold-rolled material, after the heat treatment process, cold rolling may be performed, followed by a cold rolling/annealing process in which annealing is performed within 300 seconds. When the surface layer removing process is performed after the heat treatment process, the cold rolling/annealing process may be performed after the surface layer removing process, or the surface layer removing process may be performed after the cold rolling/annealing process.
By setting the annealing treatment to a short time of 300 seconds or less, the strain caused by cold rolling can be removed while suppressing the influence on the ε-Cu phase exposed on the surface.
The conditions for cold rolling and annealing treatment are not particularly limited and may be appropriately adjusted according to the composition of the slab.

Since the ferritic stainless steel material according to Embodiment 1 of the present invention can maintain antibacterial and antiviral properties for a long period of time, it can be used as an antibacterial/antiviral member. In addition, since the ferritic stainless steel material according to Embodiment 1 of the present invention can have a Vickers hardness of 160 Hv or less, it can be easily processed into a shape suitable for antibacterial/antiviral members.

(Embodiment 2)
The austenitic stainless steel material according to Embodiment 2 of the present invention contains C: 0.12% or less, Si: 4.00% or less, Mn: 6.00% or less, P: 0.050% or less, and S: 0.05% or less. 030% or less, Ni: 4.00 to 20.00%, Cr: 10.00 to 32.00%, Cu: 2.00 to 6.00%, and the balance being Fe and impurities.
Further, the austenitic stainless steel material according to Embodiment 2 of the present invention has Nb: 1.00% or less, Ti: 1.00% or less, V: 1.00% or less, W: 2.00% or less, Mo: 6.00% or less, N: 0.350% or less, Sn: 0.50% or less, Al: 5.00% or less, Zr: 0.50% or less, Co: 0.50% or less, B: 0.50% or less. 020% or less, Ca: 0.10% or less, and REM: 0.20% or less.
Each component will be described in detail below.

<C: 0.12% or less>
C is an austenite-forming element, and is an element effective in improving the strength of the austenitic stainless steel material and uniformly dispersing and precipitating the ε-Cu phase by forming Cr carbide. However, if the C content is too high, the material becomes hard and workability is reduced, and in addition, sensitization occurs when subjected to thermal effects such as welding, and the corrosion resistance of the austenitic stainless steel is reduced. Therefore, the upper limit of the C content is controlled to 0.12%, preferably 0.10%, more preferably 0.09%, still more preferably 0.08%. On the other hand, the lower limit of the C content is not particularly limited, but is preferably 0.001%, more preferably 0.003%, and still more preferably 0.005%.

<Si: 4.00% or less>
Si is an effective element for improving the corrosion resistance and strength of austenitic stainless steel. However, if the Si content is too high, the workability of the austenitic stainless steel material will be reduced due to hardening. In addition, since Si is a ferrite phase (α phase) forming element, it causes destabilization of the austenite phase (γ phase) and formation of the ferrite phase. Therefore, the upper limit of the Si content is controlled to 4.00%, preferably 3.00%, more preferably 2.00%, still more preferably 1.50%. On the other hand, the lower limit of the Si content is not particularly limited, but is preferably 0.01%, more preferably 0.05%, and still more preferably 0.10%.

<Mn: 6.00% or less>
Mn is an austenite phase (γ phase) forming element. Also, Mn generates MnS, and MnS acts as a nucleus of the ε-Cu phase. However, if the Mn content is too high, the corrosion resistance of the austenitic stainless steel will be lowered. Therefore, the upper limit of the Mn content is controlled to 6.00%, preferably 4.00%, more preferably 3.00%, still more preferably 2.50%. On the other hand, the lower limit of the Mn content is not particularly limited, but is preferably 0.01%, more preferably 0.05%, and still more preferably 0.10%.

<P: 0.050% or less>
If the P content is too high, the corrosion resistance and workability of the austenitic stainless steel will be lowered. Therefore, the upper limit of the P content is controlled to 0.050%, preferably 0.040%, more preferably 0.035%. On the other hand, the lower limit of the P content is not particularly limited. 010%.

<S: 0.030% or less>
If the S content is too high, the hot workability is lowered, the manufacturability of the austenitic stainless steel is lowered, and the corrosion resistance is also adversely affected. Therefore, the upper limit of the S content is controlled to 0.030%, preferably 0.020%, more preferably 0.010%. On the other hand, the lower limit of the S content is not particularly limited. 0003%.

<Ni: 4.00 to 20.00%>
Ni, like Mn, is an austenite phase (γ phase) forming element and improves corrosion resistance and workability. Since Ni is an expensive element, an excessive Ni content leads to an increase in manufacturing costs. Therefore, the upper limit of the Ni content is controlled to less than 20.00%, preferably 15.00% or less, more preferably 12.00% or less, still more preferably 10.00% or less. On the other hand, if the Ni content is too low, the corrosion resistance of the austenitic stainless steel will be lowered. Therefore, the lower limit of the Ni content is controlled to 4.00%, preferably 6.00%, more preferably 8.00%, still more preferably 8.50%.

<Cr: 10.00 to 32.00%>
Cr is an important element for maintaining the corrosion resistance of austenitic stainless steel. However, if the Cr content is too high, the refining cost will increase, and solid-solution strengthening will harden the austenitic stainless steel. Therefore, the upper limit of the Cr content is controlled to 32.00%, preferably 25.00%, more preferably 22.00%, still more preferably 20.00%. On the other hand, if the Cr content is too small, sufficient corrosion resistance cannot be obtained. Therefore, the lower limit of the Cr content is controlled to 10.00%, preferably 14.00%, more preferably 15.00%, still more preferably 18.00%.

<Cu: 2.00 to 6.00%>
Cu is an element necessary for precipitating the ε-Cu phase, which provides antibacterial and antiviral properties. Cu is also an element that improves the workability of austenitic stainless steel. In order to obtain such effects, the lower limit of the Cu content is controlled to 2.00%, preferably 2.50%, more preferably 3.00%, still more preferably 3.60%. On the other hand, if the Cu content is too high, the corrosion resistance of the austenitic stainless steel material is reduced, and a low melting point phase is formed during casting, resulting in deterioration of hot workability. Therefore, the upper limit of the Cu content is controlled to 6.00%, preferably 5.00%, more preferably 4.80%, still more preferably 4.50%.

<Nb: 1.00% or less, Ti: 1.00% or less, V: 1.00% or less, W: 2.00% or less>
Nb, Ti, V and W are elements that form carbides and nitrides to reduce sensitization due to grain boundary segregation of C and N and improve intergranular corrosion resistance, and are added as necessary. be. However, if the contents of Nb, Ti, V, and W are too high, they cause surface flaws, leading to deterioration in quality and deterioration in workability of the austenitic stainless steel material. Therefore, the upper limits of the contents of Nb, Ti and V are all controlled to 1.00%, preferably 0.50%. Also, the upper limit of the W content is controlled to 2.00%, preferably 1.50%. On the other hand, the lower limit of the content of Nb, Ti, V and W is not particularly limited, but from the viewpoint of obtaining the effect of these elements, it is 0.01%, preferably 0.02%.

<Mo: 6.00% or less>
Mo is an element that improves the corrosion resistance of austenitic stainless steel materials and is added as necessary. However, if the Mo content is too high, the manufacturing cost will increase. Therefore, the upper limit of the Mo content is controlled to 6.00%, preferably 5.00%, more preferably 3.00%, still more preferably 2.00%. On the other hand, the lower limit of the Mo content is not particularly limited, but from the viewpoint of obtaining the effect of Mo, it is preferably 0.01%, more preferably 0.03%, and still more preferably 0.10%.

<N: 0.350% or less>
N, like Mo, is an element that improves the corrosion resistance of austenitic stainless steel materials and is added as necessary. However, if the content of N is too high, the workability of the austenitic stainless steel deteriorates due to hardening. Therefore, the upper limit of the N content is controlled to 0.350%, preferably 0.200%, more preferably 0.150%, still more preferably 0.050%. On the other hand, the lower limit of the N content is not particularly limited, but from the viewpoint of obtaining the effect of N, it is preferably 0.001%, preferably 0.003%.

<Sn: 0.50% or less>
Sn, like Mo and N, is an element that improves the corrosion resistance of austenitic stainless steel materials, and is added as necessary. However, if the Sn content is too high, the hot workability of the austenitic stainless steel will deteriorate. Therefore, the upper limit of the Sn content is controlled to 0.50%, preferably 0.30%. On the other hand, the lower limit of the Sn content is not particularly limited, but from the viewpoint of obtaining the effect of Sn, it is preferably 0.01%, more preferably 0.02%.

<Al: 5.00% or less>
Al is an element used for deoxidation in the refining process and is added as necessary. Al is also an element that improves the corrosion resistance and oxidation resistance of austenitic stainless steel. However, if the Al content is too high, the amount of inclusions produced increases and the quality deteriorates. Therefore, the upper limit of the Al content is 5.00%, preferably 3.00%, more preferably 2.00%, still more preferably 1.00%. On the other hand, the lower limit of the Al content is not particularly limited, but from the viewpoint of obtaining the effect of Al, it is preferably 0.01%, more preferably 0.03%.

<Zr: 0.50% or less>
Zr, like Al, is an element that improves the oxidation resistance of austenitic stainless steel materials, and is added as necessary. However, if the Zr content is too high, it will lead to an increase in manufacturing cost. Therefore, the upper limit of the Zr content is controlled to 0.50%, preferably 0.30%. On the other hand, the lower limit of the Zr content is not particularly limited, but from the viewpoint of obtaining the effect of Zr, it is preferably 0.01%, more preferably 0.03%.

<Co: 0.50% or less>
Co, like Al and Zr, is an element that improves the oxidation resistance of austenitic stainless steel materials and is added as necessary. However, if the Co content is too high, the manufacturing cost will increase. Therefore, the upper limit of the Co content is controlled to 0.50%, preferably 0.30%. On the other hand, the lower limit of the Co content is not particularly limited, but from the viewpoint of obtaining the effect of Co, it is preferably 0.01%, more preferably 0.03%.

<B: 0.020% or less>
B is an element that improves hot workability and is added as necessary. However, if the content of B is too high, the corrosion resistance and weldability of the austenitic stainless steel material will deteriorate. Therefore, the upper limit of the B content is controlled to 0.020%, preferably 0.015%, more preferably 0.010%, and even more preferably 0.005%. On the other hand, the lower limit of the content of B is not particularly limited, but is controlled to 0.0001%, preferably 0.0003%, more preferably 0.0005% from the viewpoint of obtaining the effect of B.

<Ca: 0.10% or less>
Ca, like B, is an element that improves the hot workability of austenitic stainless steel materials, and is added as necessary. Ca is also an element that forms sulfides and suppresses grain boundary segregation of S, thereby improving grain boundary oxidation resistance. However, if the Ca content is too high, workability is lowered. Therefore, the upper limit of the Ca content is controlled to 0.10%, preferably 0.05%. On the other hand, the lower limit of the Ca content is not particularly limited, but is preferably 0.001%, more preferably 0.003%, from the viewpoint of obtaining the effect of Ca.

<REM: 0.20% or less>
REM (rare earth element), like B and Ca, is an element that improves the hot workability of an austenitic stainless steel material, and is added as necessary. REM is also an element that improves corrosion resistance by forming sulfides that are difficult to elute and suppressing the formation of MnS, which is a starting point for corrosion. However, if the REM content is too high, it will lead to an increase in manufacturing costs. Therefore, the upper limit of the REM content is controlled to 0.20%, preferably 0.10%. On the other hand, the lower limit of the REM content is not particularly limited, but is preferably 0.001%, more preferably 0.01%, from the viewpoint of obtaining the effect of REM.
It should be noted that REM may be used singly or as a mixture of two or more.

Next, the features of the ε-Cu phase exposed on the surface of the austenitic stainless steel material according to Embodiment 2 of the present invention will be described in detail.

<Area ratio: 0.1 to 4.0%>
As the area ratio of the ε-Cu phase exposed to the surface increases, the amount of Cu ions eluted increases, so antibacterial and antiviral properties can be enhanced. The area fraction of this ε-Cu phase mainly depends on the crystal structure and the Cu content. Therefore, the upper limit of the area ratio of the ε-Cu phase is controlled to 4.0%, preferably 3.0%, more preferably 2.0%, considering the Cu content in the austenitic stainless steel material. . On the other hand, the lower limit of the area ratio of the ε-Cu phase is controlled to 0.1%, preferably 0.3%, more preferably 0.6% from the viewpoint of ensuring antibacterial and antiviral properties.

<Average particle size: 10 to 300 nm>
As the average particle size of the ε-Cu phase exposed on the surface is larger, Cu ions can be eluted over a longer period of time, thereby improving the durability of the antibacterial and antiviral properties. However, if the average particle size of the ε-Cu phase is too large, the distance between particles of the ε-Cu phase exposed on the surface tends to increase. Therefore, when bacteria or viruses adhere between the particles of the ε-Cu phase exposed on the surface, sufficient antibacterial and antiviral properties may not be obtained. Therefore, the upper limit of the average particle size of the ε-Cu phase is controlled to 300 nm, preferably 250 nm, more preferably 200 nm, still more preferably 150 nm. On the other hand, the lower limit of the average particle size of the ε-Cu phase is controlled to 10 nm, preferably 20 nm, more preferably 30 nm, from the viewpoint of ensuring the elution sustainability of Cu ions.

The austenitic stainless steel material according to Embodiment 2 of the present invention preferably has a Vickers hardness of 190 Hv or less, more preferably 180 Hv or less. By controlling the Vickers hardness in such a manner, workability can be ensured, so that it can be used for various purposes.
Although the lower limit of Vickers hardness is not particularly limited, it is generally 100Hv.

The austenitic stainless steel material according to Embodiment 2 of the present invention preferably has an antibacterial activity value of 2.0 or more in an antibacterial test conforming to JIS Z2801:2010. With such an antibacterial activity value, high antibacterial properties can be objectively ensured.

The austenitic stainless steel material according to Embodiment 2 of the present invention preferably has an antiviral activity value of 2.0 or more in an antiviral test conforming to ISO 21702:2019. With such an antiviral activity value, high antiviral properties can be objectively guaranteed.

Although the type of the austenitic stainless steel material according to the second embodiment of the present invention is not particularly limited, it is preferably a hot-rolled material or a cold-rolled material.
In the case of hot-rolled material, its thickness is generally 3 mm or more. In the case of cold-rolled material, the thickness is generally less than 3 mm.

The austenitic stainless steel material according to Embodiment 2 of the present invention can be manufactured by a method including a hot rolling process, a cooling process and a heat treatment process.
The hot-rolling step is a step of hot-rolling a slab having the above composition to obtain a hot-rolled material. Specifically, a hot-rolled material is obtained by subjecting a slab having the above composition to rough rolling, followed by finish hot rolling. This hot-rolled material may be wound into a coil.
The slab having the above composition is not particularly limited, but can be obtained, for example, by melting stainless steel having the above composition and forging or casting.

Finish hot rolling is carried out so that the finishing temperature of finish hot rolling is 850 to 1050°C. By controlling the final hot rolling temperature within this temperature range, a small amount of fine "seeds" of the ε-Cu phase can be easily precipitated uniformly in the cooling process after the final hot rolling. As a result, by growing the ε-Cu phase in the heat treatment process, the distribution of the ε-Cu phase on the surface can be controlled as described above. On the other hand, if the finish hot rolling finish temperature is lower than 850° C., the fine “seeds” of the ε-Cu phase are not sufficiently precipitated in the cooling step after the finish hot rolling finish. As a result, when the ε-Cu phase is grown in the heat treatment process, the average particle size and maximum inter-particle distance of the ε-Cu phase on the surface become too large. On the other hand, if the finish hot rolling finish temperature exceeds 1050°C, the structure becomes coarse and the workability and toughness are lowered. In addition, multiple times of rolling and heat treatment are required to return the coarsened structure to a fine structure, which increases the manufacturing cost.
Other conditions in the hot rolling process may be appropriately set according to the composition of the slab, and are not particularly limited.

When the austenitic stainless steel material is a cold-rolled material, after the heat treatment step, cold rolling may be performed, followed by a cold rolling/annealing step of annealing within 300 seconds. When the surface layer removing process is performed after the heat treatment process, the cold rolling/annealing process may be performed after the surface layer removing process, or the surface layer removing process may be performed after the cold rolling/annealing process.
By setting the annealing treatment to a short time of 300 seconds or less, the strain caused by cold rolling can be removed while suppressing the influence on the ε-Cu phase exposed on the surface.
The conditions for cold rolling and annealing treatment are not particularly limited and may be appropriately adjusted according to the composition of the slab.

The austenitic stainless steel material according to Embodiment 2 of the present invention can maintain antibacterial and antiviral properties for a long period of time, so it can be used for antibacterial and antiviral members. In addition, since the austenitic stainless steel material according to Embodiment 2 of the present invention can have a Vickers hardness of 190 Hv or less, it can be easily processed into a shape suitable for antibacterial/antiviral members.

The antibacterial/antiviral member of the present invention includes the above stainless steel material (for example, the ferritic stainless steel material according to Embodiment 1 of the present invention and/or the austenitic stainless steel material according to Embodiment 2 of the present invention). The above stainless steel material used for this antibacterial/antiviral member may be processed into various shapes by methods known in the art.
The antibacterial/antiviral member of the present invention can further include members other than the stainless steel material described above.
The antibacterial/antiviral member is not particularly limited, but is used for kitchen equipment, home appliances, medical equipment, building interior building materials, transportation equipment, laboratory equipment, sanitary equipment, etc., and antibacterial and antiviral properties are required. and various members.

Although the contents of the present invention will be described in detail below with reference to Examples, the present invention is not to be construed as being limited to these.

<Ferritic stainless steel material>
Stainless steels having a ferritic composition (the balance being Fe and impurities) of steel grades A to J shown in Table 1 were melted and forged into slabs, and then the finish hot rolling finish temperature was measured as shown in Table 2. A hot-rolled material was obtained by hot-pressing to a thickness of 3 mm. The hot-rolled material was wound into a coil, quickly placed in a heat-insulating box, and then cooled at an average cooling rate shown in Table 2 between 900 and 500°C. The average cooling rate was adjusted by the amount of Ar gas supplied to the heat insulating box. Next, the cooled hot-rolled material was subjected to heat treatment using a batch annealing furnace in an air atmosphere at 800° C. for the heating time shown in Table 2. Next, the heat-treated hot-rolled material is cut into pieces of 100 mm (rolling direction) x 100 mm (width direction) by cutting, then pickled to remove scales, and polished with a P400 buff (#400). A ferritic stainless steel material was obtained.

The following evaluations were performed on the obtained ferritic stainless steel material.

(Area ratio of ε-Cu phase exposed on the surface)
A disk having a diameter of 3 mm was cut out from a ferritic stainless steel material, one surface of which was ground to a thickness of 0.5 mm, and then the ground surface was electropolished to prepare a test piece. TEM images were taken at 10 randomly selected points (total visual field area: 15 μm ² ) on the electrolytically polished surface of this test piece, and then the TEM images were image-analyzed to measure the area of the ε-Cu phase. . The area ratio of the ε-Cu phase was calculated by dividing the measured ε-Cu phase area by the viewing area.

(Average particle size of ε-Cu phase exposed on the surface)
The equivalent circle diameter of the ε-Cu phase (30 pieces) was obtained by image analysis of the TEM image obtained in the same manner as the area ratio above, and the average value was calculated to obtain the average particle diameter of the ε-Cu phase. got

(Maximum interparticle distance of ε-Cu phase exposed on the surface)
Image analysis of the TEM image obtained in the same manner as the above area ratio is performed, the distance between the centers of gravity of the ε-Cu phase in the adjacent Voronoi regions is measured as the distance between particles according to the method described above, and the maximum value is obtained. , to obtain the maximum interparticle distance of the ε-Cu phase.

(Antibacterial test: antibacterial activity value)
After cutting out a test piece of 50 mm (rolling direction)×50 mm (width direction) from the ferritic stainless steel material, an antibacterial test was performed in accordance with JIS Z2801:2010 to obtain an antibacterial activity value (initial). In the antibacterial test, Staphylococcus aureus was used as bacteria, and a polyethylene film of 40 mm×40 mm was used as the adhesion film. In addition, the inoculum amount of the fungus solution was 0.4 mL, and the entire surface of the test piece was lightly wiped with a local gauze soaked with ethanol having a purity of 99% or more just before the start of the test, and the test was performed after sufficiently drying. .
In addition, in order to evaluate the durability of the antibacterial effect, the test piece was immersed in 500 mL of water and held at 80 ° C. for 16 hours in a constant temperature bath. after immersion) was determined.

(Antiviral test: antiviral activity value)
After cutting a test piece of 50 mm (rolling direction) x 50 mm (width direction) from the ferritic stainless steel material, an antiviral test was performed in accordance with ISO 21702:2019 to determine the antiviral activity value (initial). In the antiviral test, influenza A virus was used as the virus, and a polyethylene film of 40 mm×40 mm was used as the adhesion film. In addition, the amount of virus suspension (test solution) inoculated was 0.4 mL, and just before the start of the test, the entire surface of the test piece was lightly wiped with a local gauze soaked with ethanol with a purity of 99% or more, and dried thoroughly. After that, the test was carried out.
In addition, in order to evaluate the durability of the antiviral effect, the test piece was immersed in 500 mL of water, held at 80 ° C. for 16 hours in a constant temperature bath, and then subjected to an antiviral test in the same manner as described above. Values (after immersion in water) were determined.

(Vickers hardness)
Vickers hardness was measured according to JIS Z2244:2009. For the measurement, a Vickers hardness tester HV-100 manufactured by Mitutoyo Co., Ltd. was used, the measurement load was 10 kg, the surface Vickers hardness was measured at 10 randomly selected points, and the average value was taken as the result. .

Table 3 shows the above evaluation results.

As shown in Table 3, No. Since the ferritic stainless steel materials 1-1 to 1-11 (examples of the present invention) had a predetermined composition and a distribution state of the ε-Cu phase on the surface, the antibacterial activity value (initial and after immersion in water), the antibacterial activity value Viral activity values (initial and after water immersion) and Vickers hardness results were all good.
On the other hand, No. In the ferritic stainless steel material 1-12 (comparative example), the finish hot rolling finish temperature was too low and the average cooling rate was too high, so that the maximum interparticle distance of the ε-Cu phase was too large. As a result, antiviral properties (antiviral activity value of 2.0 or more) were not obtained.
No. In the ferritic stainless steel materials 1-13 and 1-14 (comparative examples), the average cooling rate was too high, so the average particle size of the ε-Cu phase and the maximum distance between particles increased. As a result, antiviral properties (antiviral activity value of 2.0 or more) were not obtained.

No. In the ferritic stainless steel material 1-15 (comparative example), the average cooling rate was too small, so the maximum interparticle distance of the ε-Cu phase was small. As a result, the antibacterial activity value and the antiviral activity value after immersion in water were low, and the effect of maintaining the antibacterial and antiviral properties was not sufficient.
No. Since the ferritic stainless steel materials 1-16 and 1-17 (comparative examples) did not have a predetermined composition, the distribution state of the ε-Cu phase on the surface could not be controlled appropriately. As a result, antibacterial properties (antibacterial activity value of 2.0 or more) and antiviral properties (antiviral activity value of 2.0 or more) were not obtained.
No. In 1-18 (comparative example), cracks occurred during hot rolling, and a ferritic stainless steel material could not be produced.

<Austenitic stainless steel material>
Stainless steels having an austenitic composition (the balance being Fe and impurities) of steel grades a to j shown in Table 4 were melted and forged into slabs, and the finish hot rolling finish temperature was measured as shown in Table 5. A hot-rolled material was obtained by hot-pressing to a thickness of 3 mm. The hot-rolled material was wound into a coil, quickly placed in a heat-insulating box, and then cooled between 900 and 500° C. at the average cooling rate shown in Table 5. The average cooling rate was adjusted by the amount of Ar gas supplied to the heat insulating box. Next, the cooled hot-rolled material was subjected to heat treatment using a batch annealing furnace in an air atmosphere at 800° C. for the heating time shown in Table 5. Next, the heat-treated hot-rolled material is cut into pieces of 100 mm (rolling direction) x 100 mm (width direction) by cutting, then pickled to remove scales, and polished with a P400 buff (#400). An austenitic stainless steel material was obtained.

The obtained austenitic stainless steel material was evaluated in the same manner as the above ferritic stainless steel material. Table 6 shows the evaluation results.

As shown in Table 6, No. The austenitic stainless steel materials 2-1 to 2-11 (examples of the present invention) had a predetermined composition and a distribution state of the ε-Cu phase on the surface. Viral activity values (initial and after water immersion) and Vickers hardness results were all good.
On the other hand, No. In the austenitic stainless steel material No. 2-12 (comparative example), the finish hot rolling finishing temperature was too low and the average cooling rate was too high, so that the average particle size of the ε-Cu phase was too large. As a result, antiviral properties (antiviral activity value of 2.0 or more) were not obtained.
No. In the austenitic stainless steel materials 2-13 and 2-14 (comparative examples), the average cooling rate was too high, so the maximum interparticle distance of the ε-Cu phase was large. As a result, antiviral properties (antiviral activity value of 2.0 or more) were not obtained.

No. In the austenitic stainless steel material No. 2-15 (comparative example), the average cooling rate was too low, so the average particle size of the ε-Cu phase was small. As a result, the antibacterial activity value and the antiviral activity value after immersion in water were low, and the effect of maintaining the antibacterial and antiviral properties was not sufficient.
No. Since the austenitic stainless steel materials 2-16 and 2-17 (comparative examples) did not have a predetermined composition, it was not possible to appropriately control the distribution of the ε-Cu phase on the surface. As a result, antibacterial properties (antibacterial activity value of 2.0 or more) and antiviral properties (antiviral activity value of 2.0 or more) were not obtained.
No. Since 2-18 (comparative example) did not have a predetermined composition, cracks occurred during hot rolling, and an austenitic stainless steel material could not be produced.

As can be seen from the above results, according to the present invention, it is possible to provide a stainless steel material capable of maintaining antibacterial and antiviral properties for a long period of time, a method for producing the same, and an antibacterial/antiviral member.

10 stainless steel material 11 ε-Cu phase 12 passive film

Claims

Having an ε-Cu phase exposed on the surface,
The stainless steel material, wherein the ε-Cu phase on the surface has an area ratio of 0.1 to 4.0%, an average particle size of 10 to 300 nm, and a maximum interparticle distance of 100 to 1000 nm.
On mass basis, C: 0.12% or less, Si: 4.00% or less, Mn: 6.00% or less, P: 0.050% or less, S: 0.030% or less, Ni: 20.00% The stainless steel material according to claim 1, having a composition containing 10.00 to 32.00% Cr, 0.40 to 6.00% Cu, and the balance being Fe and impurities.
C content is 0.10% or less, Mn content is 2.00% or less, Ni content is 4.00% or less, Cu content is a ferritic system of 0.40 to 4.00%. 2. The stainless steel material according to 2.
Based on mass, Nb: 1.00% or less, Ti: 0.60% or less, V: 1.00% or less, W: 2.00% or less, Mo: 3.00% or less, N: 0.050% Below, Sn: 0.50% or less, Al: 5.00% or less, Zr: 0.50% or less, Co: 0.50% or less, B: 0.010% or less, Ca: 0.10% or less, REM: The stainless steel material according to claim 3, further comprising one or more selected from 0.20% or less.
The stainless steel material according to claim 3 or 4, which has a Vickers hardness of 160 Hv or less.
The stainless steel material according to claim 2, which is austenitic with a Ni content of 4.00 to 20.00% and a Cu content of 2.00 to 6.00%.
Based on mass, Nb: 1.00% or less, Ti: 1.00% or less, V: 1.00% or less, W: 2.00% or less, Mo: 6.00% or less, N: 0.350% Below, Sn: 0.50% or less, Al: 5.00% or less, Zr: 0.50% or less, Co: 0.50% or less, B: 0.020% or less, Ca: 0.10% or less, REM: The stainless steel material according to claim 6, further comprising one or more selected from 0.20% or less.
The stainless steel material according to claim 6 or 7, which has a Vickers hardness of 190 Hv or less.
The stainless steel material according to any one of claims 1 to 8, which has an antibacterial activity value of 2.0 or more in an antibacterial test according to JIS Z2801:2010.
The stainless steel material according to any one of claims 1 to 9, which has an antiviral activity value of 2.0 or more in an antiviral test conforming to ISO 21702:2019.
On mass basis, C: 0.10% or less, Si: 4.00% or less, Mn: 2.00% or less, P: 0.050% or less, S: 0.030% or less, Ni: 4.00% Hereinafter, slabs having a ferritic composition containing Cr: 10.00 to 32.00%, Cu: 0.40 to 4.00%, and the balance being Fe and impurities, or C: 0.00% by mass. 12% or less, Si: 4.00% or less, Mn: 6.00% or less, P: 0.050% or less, S: 0.030% or less, Ni: 4.00 to 20.00%, Cr: 10 00 to 32.00%, Cu: 2.00 to 6.00%, and the balance being Fe and impurities. a step of setting the finish hot rolling finish temperature to 700 to 900° C. when the composition of the slab is ferritic, and setting the finish hot rolling finish temperature to 850 to 1050° C. when the composition is austenitic;
a cooling step of cooling the hot-rolled material obtained in the hot-rolling step to a temperature between 900 and 500°C at an average cooling rate of 0.2 to 5°C/sec;
and a heat treatment step of heating the hot-rolled material cooled in the cooling step at 750 to 850° C. for 4 hours or longer.
The slab having the ferrite-based composition has, on a mass basis, Nb: 1.00% or less, Ti: 0.60% or less, V: 1.00% or less, W: 2.00% or less, Mo: 3 .00% or less, N: 0.050% or less, Sn: 0.50% or less, Al: 5.00% or less, Zr: 0.50% or less, Co: 0.50% or less, B: 0.010 % or less, Ca: 0.10% or less, REM: 0.20% or less,
The slab having the austenitic composition is, on a mass basis, Nb: 1.00% or less, Ti: 1.00% or less, V: 1.00% or less, W: 2.00% or less, Mo: 6 .00% or less, N: 0.350% or less, Sn: 0.50% or less, Al: 5.00% or less, Zr: 0.50% or less, Co: 0.50% or less, B: 0.020 % or less, Ca: 0.10% or less, and REM: 0.20% or less.
The method for manufacturing a stainless steel material according to claim 11 or 12, further comprising a surface removal step of pickling and/or polishing after the heat treatment step.
The method for producing a stainless steel material according to any one of claims 11 to 13, further comprising a cold rolling/annealing step in which cold rolling is performed after the heat treatment step and then annealing treatment is performed within 300 seconds.
An antibacterial/antiviral member containing the stainless steel material according to any one of claims 1 to 10.