KR20230076838A - Stainless steel material and its manufacturing method, and antibacterial/antiviral member - Google Patents

Abstract

It is a stainless steel material having an ε-Cu phase exposed on the surface. The ε-Cu phase on the surface of stainless steel materials 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.

Description

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

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

Since stainless steel materials are excellent in corrosion resistance, they are used in a wide range of applications such as kitchen equipment, home appliances, medical equipment, interior building materials, and transportation equipment, and are also increasingly used in environments where bacteria propagation or virus attachment easily occurs. . In recent years, there has been a growing tendency to worry about adverse effects on the human body due to the propagation of these bacteria or the attachment of viruses. Antibacterial and antiviral properties are also required for various members used in objects and transportation equipment.

Since Ag, Cu, and the like are known as metal elements having antibacterial and antiviral properties, stainless steel materials having antibacterial and antiviral properties imparted thereto have been proposed by adding these metal elements.

For example, in Patent Document 1, 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 are included, and the matrix Among them, ferritic stainless steel materials having excellent antibacterial properties in which a Cu-rich phase (ε-Cu phase) is precipitated at a ratio of 0.2% by volume or more have 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 manufactured by cold-rolling, performing an aging treatment at 500 to 800°C after final annealing, and precipitating a Cu-rich phase (ε-Cu phase) at 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: 1.0 to 5.0% by weight An austenitic stainless steel material having excellent antibacterial properties, in which a second phase (ε-Cu phase) mainly composed of Cu is dispersed in a matrix at a ratio of 0.2% by volume or more has been proposed. This austenitic stainless steel material is C: 0.1 wt% or less, Si: 2 wt% or less, Mn: 5 wt% or less, Cr: 10 to 30 wt%, Ni: 5 to 15 wt%, Cu: 1.0 to 5.0 It is manufactured by performing heat treatment one or more times in a temperature range of 500 to 900 ° C. between after hot rolling of austenitic stainless steel including weight percent until it becomes a final product.

Japanese Patent Laid-Open No. 9-170053 Japanese Patent Laid-Open No. 9-176800

In the stainless steel materials described in Patent Literatures 1 and 2, since the distribution state of the ε-Cu phase on the surface is not appropriately controlled, desired antibacterial properties may not be obtained or the antimicrobial properties may be easily lost at an early stage.

In addition, since viruses are smaller than bacteria, antiviral properties may hardly be obtained when viruses adhere between the ε-Cu phases on the surface.

An object of the present invention is to provide a stainless steel material capable of maintaining antibacterial and antiviral properties over a long period of time, a manufacturing method thereof, and an antibacterial and antiviral member.

As a result of intensive research to solve the above problems, the inventors of the present invention have found that the distribution state of the ε-Cu phase on the surface of a stainless steel material (particularly, the area ratio of the ε-Cu phase on the surface, the average of the ε-Cu phase) Particle size and maximum distance between particles of ε-Cu phase) were found to be closely related to antibacterial and antiviral properties and their persistence, and the present invention was completed.

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.

In the present invention, on a 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% or less, Cr: 10.00 to 10.00% 32.00%, Cu: 0.40 to 4.00%, the balance being Fe and impurities, or a slab having a ferritic composition, or based on mass, 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 to 20.00%, Cr: 10.00 to 32.00%, Cu: 2.00 to 6.00%, the balance being Fe and impurities. A slab having an austenitic composition is hot rolled. A hot rolling process for obtaining a hot-rolled material by performing a hot-rolling process, wherein when the composition of the slab is ferritic, the finish hot-rolling end temperature is 700 to 900° C., and when the slab is austenitic, the finish hot-rolling end temperature is 850 to 1050° C.;

A cooling step of cooling the hot-rolled material obtained in the hot rolling step between 900 and 500 ° C. at an average cooling rate of 0.2 to 5 ° C./sec;

Heat treatment process of heating the hot-rolled material cooled in the cooling process at 750 to 850 ° C. for 4 hours or more

A method for producing a stainless steel material comprising a.

Moreover, this invention is an antibacterial/antiviral member containing the said stainless steel material.

ADVANTAGE OF THE INVENTION According to this invention, the stainless steel material which can maintain antibacterial and antiviral properties over a long period of time, its manufacturing method, and an antibacterial/antiviral member can be provided.

1 is a schematic view of the surface of a typical stainless steel material of the present invention.

The present invention is a stainless steel material having an ε-Cu phase exposed on the surface. This 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.

Here, the schematic diagram of the surface of the typical stainless steel material of this invention is shown in FIG.

As shown in FIG. 1, in the stainless steel material 10, the ε-Cu phase 11 is exposed on the surface of the mother phase. In addition, a passivation film 12 is formed on the surface of the parent phase where the ε-Cu phase 11 is not exposed.

By exposing the ε-Cu phase 11 on the surface of the mother phase, Cu ions can be eluted from the ε-Cu phase 11 when moisture contacts the surface of the stainless steel materials 10 . For example, when a person's 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, it can be sterilized, and even if viruses adhere to the surface, they are inactivated and killed before long.

In addition, since the passivation film 12 is formed on the surface of the mother phase where the ε-Cu phase 11 is not exposed, the 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: 0.030% or less, Ni: 20.00% or less, It is preferable that it is a composition which contains Cr: 10.00-32.00% and Cu: 0.40-6.00%, and the balance consists of Fe and impurities.

Here, in this specification, the "%" expression regarding a component means "mass %" unless otherwise indicated.

The metal structure of the stainless steel material of the present invention is not particularly limited, but is preferably ferritic or austenitic.

Hereinafter, embodiments of the present invention will be specifically described by taking ferritic stainless steel materials and austenitic stainless steel materials as examples. The present invention is not limited to the following embodiments, and changes, improvements, etc. are appropriately added to the following embodiments based on the common knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that entering the scope.

(Embodiment 1)

Ferritic stainless steel according to Embodiment 1 of the present invention, 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% or less, It has a composition including Cr: 10.00 to 32.00% and Cu: 0.40 to 4.00%, the remainder being Fe and impurities.

Here, in this specification, "steel material" means materials of various shapes, such as a steel plate. In addition, "steel plate" is a concept including a steel strip. In addition, "impurity" is a component that is mixed by various factors in raw materials such as ore and scrap and manufacturing process when manufacturing stainless steel materials industrially, and means that it is permitted within a range that does not adversely affect the present invention .

In the ferritic stainless steel according to Embodiment 1 of the present invention, 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% 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. can include more.

Hereinafter, each component is demonstrated in detail.

<C: 0.10% or less>

C is an element effective for improving the strength of a ferritic stainless steel material and uniformly distributing and precipitating an ε-Cu phase by generating Cr carbide. However, if the content of C is too large, in addition to being hard and poor in workability, sensitization occurs when subjected to heat effects such as welding, and the corrosion resistance of the ferritic stainless steel material is reduced. 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%, still more preferably 0.005%.

<Si: 4.00% or less>

Si is a ferrite phase (α phase) forming element, and is an element effective in improving the corrosion resistance and strength of ferritic stainless steel materials. However, when the content of Si is too large, it hardens and the workability of the ferritic stainless steel material is lowered. 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 content of Si is not particularly limited, but is preferably 0.01%, more preferably 0.05%, still more preferably 0.10%.

<Mn: 2.00% or less>

Mn is an element that improves the heat resistance of ferritic stainless steel materials. However, when the content of Mn is too large, the corrosion resistance of ferritic stainless steel materials will decrease. In addition, since Mn is an austenite phase (γ phase) forming element, it forms a γ phase (martensite phase at room temperature) at high temperatures, and the workability of ferritic stainless steel materials also deteriorates. 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%, still more preferably 0.10%.

<P: 0.050% or less>

If the content of P is too large, the corrosion resistance and workability of the ferritic stainless steel materials will decrease. Therefore, the upper limit of the P content is controlled to 0.050%, preferably 0.040%, and more preferably 0.030%. On the other hand, the lower limit of the P content is not particularly limited, but is preferably 0.001%, more preferably 0.005%, still more preferably 0.010%, since refining costs are incurred when the P content is reduced.

<S: 0.030% or less>

When there is too much content of S, while hot workability will fall and the manufacturability of ferritic stainless steel materials will fall, corrosion resistance will also be adversely affected. Therefore, the upper limit of the S content is controlled to 0.030%, preferably 0.020%, and more preferably 0.010%. On the other hand, the lower limit of the S content is not particularly limited, but is preferably 0.0001%, more preferably 0.0002%, still more preferably 0.0003%, since refining costs are incurred when the S content is reduced.

<Ni: 4.00% or less>

Ni is an element that improves the corrosion resistance of ferritic stainless steel materials. However, since Ni, like Mn, is an austenite phase (γ phase) forming element, if its content is too large, γ phase (martensite phase at room temperature) is formed at high temperatures, and the workability of ferritic stainless steel materials deteriorates. throw away In addition, since Ni is an expensive element, it also leads to an increase in manufacturing cost. 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%, 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 materials. However, when the content of Cr is too large, it causes an increase in refining cost, hardening due to solid solution strengthening, and the workability of the ferritic stainless steel material is lowered. 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, when the content of Cr is too small, corrosion resistance is not sufficiently 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 required to precipitate an ε-Cu phase imparting antibacterial and antiviral properties. Moreover, Cu is also an element which improves the workability of ferritic stainless steel materials. In order to obtain such an effect, 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, when the content of Cu is too large, the corrosion resistance of the ferritic stainless steel material is lowered, and a low melting point phase is formed during casting, resulting in a decrease in hot workability. Therefore, the upper limit of the content of Cu 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 forms precipitates and has an effect of uniformly precipitating an ε-Cu phase around them, and is added as necessary. However, when the content of Nb is too large, the workability of ferritic stainless steel materials will decrease. 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 a precipitate and has an effect of uniformly precipitating an ε-Cu phase around it, and is added as necessary. However, when the content of Ti is too large, it causes surface flaws and causes quality deterioration, and the workability of the ferritic stainless steel materials is lowered. Therefore, the upper limit of the content of Ti is controlled to be 0.60%, preferably 0.30%. On the other hand, the lower limit of the content of Ti 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 forms precipitates and has an effect of uniformly precipitating an ε-Cu phase around them, and is added as necessary. However, when the content of V is too large, it causes surface scratches and quality deterioration, and the workability of the ferritic stainless steel material is lowered. 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 forms precipitates and has an effect of uniformly precipitating an ε-Cu phase around them, and is added as necessary. However, when the content of W is too large, it causes surface flaws and causes quality deterioration, and the workability of the ferritic stainless steel material is lowered. 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 content of W 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 needed. However, when there is too much content of Mo, it will lead to the raise of manufacturing cost. 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 content of Mo is not particularly limited, but from the viewpoint of obtaining the effect of Mo, it is preferably 0.01%, more preferably 0.03%, 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 needed. However, if the content of N is too large, it hardens and the workability of the ferritic stainless steel material is lowered. 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, when there is too much content of Sn, it will lead to the raise of manufacturing cost. Therefore, the upper limit of the content of Sn is 0.50%, preferably controlled to 0.30%. On the other hand, the lower limit of the content of Sn 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 needed. Al is also an element that improves the corrosion resistance and oxidation resistance of ferritic stainless steel materials. However, if the content of Al is too large, 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 content of Al 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, when there is too much content of Zr, it will lead to the rise of 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 content of Zr 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, when the content of Co is too large, it leads to an increase in manufacturing cost. 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 content of Co 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 needed. In addition, B is also an element that improves the secondary workability of ferritic stainless steel materials by grain boundary strengthening. However, if the content of B is too large, 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 needed. In addition, Ca is also an element that improves grain boundary oxidation resistance by forming sulfides and suppressing grain boundary segregation of S. However, when the content of Ca is too large, a decrease in workability is caused. 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 content of Ca 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. Moreover, REM is also an element that improves corrosion resistance by forming sulfides that are difficult to elute and suppressing the formation of MnS serving as a starting point for corrosion. However, if there is too much content of REM, it will lead to a rise in manufacturing cost. Therefore, the upper limit of the REM content is controlled to be 0.20%, preferably 0.10%. On the other hand, the lower limit of the content of REM is not particularly limited, but from the viewpoint of obtaining the effect of REM, it is preferably 0.001%, more preferably 0.01%.

In addition, in this specification, "REM" refers to the generic name of the two elements scandium (Sc) and yttrium (Y), and 15 elements (lanthanoids) ranging from lanthanum (La) to lutetium (Lu). These may be used independently and may be used as a mixture of 2 or more types.

Next, the characteristics 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 elution amount of Cu ions increases, so antibacterial and antiviral properties can be improved. The area ratio of this ε-Cu phase mainly depends on the crystal structure and the content of Cu. Therefore, the upper limit of the area ratio of the ε-Cu phase is 4.0%, preferably 2.0%, more preferably 1.9%, still more preferably 1.8%, considering the Cu content in the ferritic stainless steel material. controlled On the other hand, the lower limit of the area ratio of the ε-Cu phase is controlled to 0.1%, preferably 0.3%, and more preferably 0.6%, from the viewpoint of ensuring antibacterial and antiviral properties.

Here, "the area ratio of the epsilon-Cu phase exposed to the surface" in this specification is computable by observing the surface of stainless steel materials with a TEM (transmission electron microscope). Specifically, on the surface of the stainless steel material, TEM images were taken at three or more randomly selected locations, the TEM images were image analyzed, the area of the ε-Cu phase was measured, and the area of the ε-Cu phase was determined by visual field By dividing by the area, "the area ratio of the ε-Cu phase exposed to the surface" can be calculated. The field of view area is not particularly limited, but is preferably 10 μm ² or more in total of imaging locations.

<average particle diameter: 10 to 300 nm>

As the average particle size of the ε-Cu phase exposed to the surface is larger, Cu ions can be eluted over a long period of time, so the durability of antibacterial and antiviral properties is improved. However, when 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, there are cases where sufficient antibacterial and antiviral properties cannot be obtained. Therefore, the upper limit of the average particle size of the ε-Cu phase is controlled to 300 nm, preferably 250 nm, and more preferably 200 nm. On the other hand, the lower limit of the average particle diameter of the ε-Cu phase is controlled to 10 nm, preferably 30 nm, and more preferably 50 nm, from the viewpoint of ensuring the persistence of elution of Cu ions.

Here, "the average particle diameter of the epsilon-Cu phase exposed to the surface" in this specification is computable by observing the surface of stainless steel materials with a TEM (transmission electron microscope). Specifically, on the surface of a stainless steel material, after photographing TEM images at three or more points randomly selected, the TEM images were image analyzed to determine the equivalent circle diameter of the ε-Cu phase, and the average value was calculated as "ε exposed to the surface". -Average particle diameter of Cu phase”.

<Maximum interparticle distance: 100 to 1000 nm>

In general, the size of bacteria is 0.5 ~ 3μm, whereas the size of viruses is very small, 10 ~ 200nm. Therefore, if the maximum distance between the particles of the ε-Cu phase exposed to the surface is too large, in particular, when a virus adheres between the particles of the ε-Cu phase exposed to the surface, sufficient antiviral properties may not be obtained. Therefore, the upper limit of the maximum distance between particles of the ε-Cu phase is controlled to 1000 nm, preferably 800 nm, and more preferably 500 nm. On the other hand, the smaller the maximum interparticle distance of the ε-Cu phase exposed to the surface, the higher the antibacterial and antiviral properties. In the case of a relatively large ε-Cu phase with an average particle diameter of 10 to 300 nm, Considering the growth process of the phase, it is considered that the lower limit of the maximum distance between particles of the ε-Cu phase is 100 nm. Therefore, the lower limit of the maximum interparticle distance of the ε-Cu phase is controlled to 100 nm, preferably 150 nm, and more preferably 200 nm.

Here, the “maximum distance between particles 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, on the surface of a stainless steel material, after taking a TEM image at 3 or more randomly selected locations, the TEM image is image analyzed, the center of gravity (parent point) position of the ε-Cu phase is obtained, and Voronoi divide Next, the distance between the centers of gravity of the ε-Cu phase in adjacent Voronoi regions is measured as the distance between particles, and the maximum value thereof can be taken as "the maximum distance between particles 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. Since workability can be ensured by controlling to such a Vickers hardness, it becomes possible to use for various applications.

In addition, although the lower limit of Vickers hardness is not specifically limited, It is generally 100 Hv.

Here, "Vickers hardness" in this specification can be measured based on JIS Z2244:2009. In the measurement of the Vickers hardness, the measurement load is set to 10 kg, measurements are made at 5 or more randomly selected locations, and the average value is taken as the result of the Vickers hardness.

It is preferable that the antibacterial activity value of the ferritic stainless steel material concerning Embodiment 1 of this invention is 2.0 or more in the antibacterial test based on JIS Z2801:2010. If it is such an antibacterial activity value, it can objectively ensure that antibacterial property is high.

Here, the "antibacterial test" in this specification is based on JIS Z2801: 2010, and is conducted using Staphylococcus aureus as a bacterium.

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 based on ISO 21702:2019. If it is such an antiviral activity value, it can objectively ensure that antiviral property is high.

Here, the "antiviral test" in this specification is based on ISO 21702: 2019, and is conducted using an influenza A virus as a virus.

The type of ferritic stainless steel according to Embodiment 1 of the present invention is not particularly limited, but is preferably a hot-rolled material or a cold-rolled material.

In the case of hot-rolled steel, the thickness is generally 3 mm or more. Moreover, in the case of a 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 obtaining a hot rolled material by hot rolling a slab having the above composition. Specifically, after rough rolling a slab having the above composition, a hot-rolled material is obtained by finishing hot rolling. This hot-rolled material may be wound into a coil shape.

The slab having the above composition is not particularly limited, but can be obtained by forging or casting, for example, by melting stainless steel having the above composition.

Finishing hot rolling is performed so that the finishing temperature of finishing hot rolling becomes 700-900 degreeC. By controlling the finish hot rolling end temperature within this temperature range, it becomes easy to deposit a small amount and uniformly of fine "seeds" of the ε-Cu phase in the cooling step from the end of finish hot rolling. As a result, by growing the ε-Cu phase in the heat treatment step, it becomes possible to control the distribution state of the ε-Cu phase on the surface as described above. On the other hand, if the finish hot rolling end temperature is less than 700°C, fine "seeds" of the ε-Cu phase are not sufficiently precipitated in the cooling step from the end of finish hot rolling. As a result, when the ε-Cu phase is grown in the heat treatment step, the average particle diameter of the ε-Cu phase or the maximum interparticle distance on the surface becomes too large. In addition, when the finish hot rolling end temperature exceeds 900°C, the structure becomes coarse and workability and toughness deteriorate.

In addition, other conditions in the hot rolling process may be appropriately set depending on the composition of the slab, and are not particularly limited.

The cooling process is a process for depositing fine “seeds” of the ε-Cu phase, and is performed by cooling the hot-rolled material obtained in the hot rolling process between 900 and 500° C. at an average cooling rate of 0.2 to 5° C./sec. By cooling gently under these conditions, a small amount of fine “seeds” of the ε-Cu phase can be uniformly deposited in the ε-Cu phase precipitation temperature range (900 to 500° C.). Since the fine "seed" of this ε-Cu phase preferentially grows in the heat treatment step, a relatively large ε-Cu phase is uniformly dispersed. As a result, 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 these effects, the average cooling rate is preferably 1 to 5°C/sec, and more preferably 2 to 4°C/sec. On the other hand, 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 step, the average particle diameter of the ε-Cu phase or the maximum interparticle distance on the surface becomes too large. In addition, when cooling between 900 and 500 ° C. at an average cooling rate of less than 0.2 ° C./sec, the amount of precipitation of fine “seeds” of the ε-Cu phase increases. As a result, a large amount of relatively small ε-Cu phase is deposited in the heat treatment step.

In addition, the cooling method in a cooling process is not specifically limited, A well-known method in the said technical field can be used. For example, it becomes possible to cool gently under the cooling conditions described above by recuperating heat only by putting a hot-rolled material wound into a coil into a holding box. Further, fine adjustment of the cooling temperature can be performed by controlling the supply amount of gas (for example, Ar gas) supplied to the thermal insulation box.

The heat treatment step is a step of growing fine “seeds” of the ε-Cu phase 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 these 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 these effects, the heating time is preferably 6 to 48 hours, and more preferably 8 to 36 hours. On the other hand, if the heating temperature is less than 750°C or the heating time is less than 4 hours, fine "seeds" of the ε-Cu phase do not grow sufficiently and the average particle diameter of the ε-Cu phase becomes too small. In addition, when the heating temperature exceeds 850°C, the ε-Cu phase is dissolved in the mother phase.

After the heat treatment step, if necessary, a surface layer removal step of acid washing and/or polishing may be further performed. By performing the surface layer removal process, the scale and Cr sparse layer formed on the surface can be removed.

The thickness of the surface layer removed in the surface layer removal step may be appropriately adjusted depending on the composition of the slab and the like, and is not particularly limited. For example, in the case of removing the Cr sparse layer, it is preferable to remove the 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 step, cold rolling and subsequent annealing treatment for 300 seconds or less may be further performed. In the case where the surface layer removal step is performed after the heat treatment step, the cold rolling/annealing step may be performed after the surface layer removal step, or the surface layer removal step may be performed after the cold rolling/annealing step.

By performing the annealing treatment for a short time of 300 seconds or less, strain caused by cold rolling can be removed while suppressing the influence on the ε-Cu phase exposed on the surface.

In addition, the conditions of the cold rolling and annealing treatment may be appropriately adjusted depending on the composition of the slab and the like, and are not particularly limited.

Since the ferritic stainless steel material according to Embodiment 1 of the present invention can maintain antibacterial and antiviral properties over a long period of time, it can be used for 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 is easy to process it into a shape suitable for an antibacterial/antiviral member.

(Embodiment 2)

In the austenitic stainless steel material according to Embodiment 2 of the present invention, 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 to 20.00 %, Cr: 10.00 to 32.00%, Cu: 2.00 to 6.00%, the balance has a composition consisting of Fe and impurities.

In the austenitic stainless steel material according to Embodiment 2 of the present invention, 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, REM: 0.20% or less. may further include.

Hereinafter, each component is demonstrated in detail.

<C: 0.12% or less>

C is an austenite forming element, and is an effective element for improving the strength of an austenitic stainless steel material and uniformly distributing and precipitating an ε-Cu phase by generating Cr carbide. However, if the content of C is too large, in addition to being hard and poor in workability, sensitization occurs when subjected to heat effects such as welding, and the corrosion resistance of the austenitic stainless steel material deteriorates. 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%, 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 materials. However, when the content of Si is too large, it hardens and the workability of the austenitic stainless steel material is lowered. 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 content of Si is not particularly limited, but is preferably 0.01%, more preferably 0.05%, 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 on ε-Cu. However, if the content of Mn is too large, the corrosion resistance of the austenitic stainless steel material will decrease. 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%, still more preferably 0.10%.

<P: 0.050% or less>

If the content of P is too large, the corrosion resistance and workability of the austenitic stainless steel materials will decrease. Therefore, the upper limit of the P content is controlled to 0.050%, preferably 0.040%, and more preferably 0.035%. On the other hand, the lower limit of the P content is not particularly limited, but is preferably 0.001%, more preferably 0.005%, still more preferably 0.010%, since refining costs are incurred when the P content is reduced.

<S: 0.030% or less>

When the content of S is too large, the hot workability is poor and the manufacturability of the austenitic stainless steel material 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%, and more preferably 0.010%. On the other hand, the lower limit of the S content is not particularly limited, but is preferably 0.0001%, more preferably 0.0002%, still more preferably 0.0003%, since refining costs are incurred when the S content is reduced.

<Ni: 4.00 to 20.00%>

Ni, like Mn, is an austenite phase (γ phase) generating element, and improves corrosion resistance and workability. Since Ni is an expensive element, too much content leads to an increase in manufacturing cost. Therefore, the upper limit of the Ni content is controlled to be 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, when the content of Ni is too small, the corrosion resistance of the austenitic stainless steel materials is 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 materials. However, if the content of Cr is too large, it not only causes an increase in refining cost, but also hardens due to solid solution strengthening, and the workability of the austenitic stainless steel material is lowered. 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, when the content of Cr is too small, corrosion resistance is not sufficiently 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 required to precipitate an ε-Cu phase imparting antibacterial and antiviral properties. Moreover, Cu is also an element which improves the workability of austenitic stainless steel materials. In order to obtain such an effect, 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, when the content of Cu is too large, the corrosion resistance of the austenitic stainless steel material is lowered, and a low melting point phase is formed during casting to cause a decrease in hot workability. Therefore, the upper limit of the content of Cu 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 reduce sensitization due to grain boundary segregation of C or N by forming carbides or nitrides and improve intergranular corrosion resistance, and are added as necessary. However, when the content of Nb, Ti, V, and W is too large, it causes surface flaws and deteriorates quality, and the workability of the austenitic stainless steel material deteriorates. Therefore, the upper limits of the contents of Nb, Ti and V are all controlled to 1.00%, preferably 0.50%. In addition, the upper limit of the W content is controlled to be 2.00%, preferably 1.50%. On the other hand, the lower limit of the contents 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 needed. However, when there is too much content of Mo, it will lead to the raise of manufacturing cost. 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 content of Mo is not particularly limited, but from the viewpoint of obtaining the effect of Mo, it is preferably 0.01%, more preferably 0.03%, 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 needed. However, if the content of N is too large, it hardens and the workability of the austenitic stainless steel material is reduced. 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 needed. However, when the content of Sn is too large, the hot workability of the austenitic stainless steel material is reduced. Therefore, the upper limit of the content of Sn is 0.50%, preferably controlled to 0.30%. On the other hand, the lower limit of the content of Sn 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 needed. Al is also an element that improves the corrosion resistance and oxidation resistance of austenitic stainless steel materials. However, if the content of Al is too large, 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 content of Al 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 needed. However, when there is too much content of Zr, it will lead to the rise of 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 content of Zr 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, when the content of Co is too large, it leads to an increase in manufacturing cost. 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 content of Co 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 needed. However, when the content of B is too large, the corrosion resistance and weldability of austenitic stainless steel materials will decrease. Therefore, the upper limit of the B content is controlled to 0.020%, preferably 0.015%, more preferably 0.010%, still 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%, and 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 needed. In addition, Ca is also an element that improves grain boundary oxidation resistance by forming sulfides and suppressing grain boundary segregation of S. However, when the content of Ca is too large, a decrease in workability is caused. 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 content of Ca 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 austenitic stainless steel materials, and is added as necessary. Moreover, REM is also an element that improves corrosion resistance by forming sulfides that are difficult to elute and suppressing the formation of MnS serving as a starting point for corrosion. However, if there is too much content of REM, it will lead to a rise in manufacturing cost. Therefore, the upper limit of the REM content is controlled to be 0.20%, preferably 0.10%. On the other hand, the lower limit of the content of REM is not particularly limited, but from the viewpoint of obtaining the effect of REM, it is preferably 0.001%, more preferably 0.01%.

In addition, REM may be used alone or as a mixture of two or more.

Next, the characteristics 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 elution amount of Cu ions increases, so antibacterial and antiviral properties can be improved. The area ratio of this ε-Cu phase mainly depends on the crystal structure and the content of Cu. Therefore, the upper limit of the area ratio of the ε-Cu phase is controlled to 4.0%, preferably 3.0%, and more preferably 2.0%, considering the Cu content in the austenitic stainless steel. On the other hand, the lower limit of the area ratio of the ε-Cu phase is controlled to 0.1%, preferably 0.3%, and more preferably 0.6%, from the viewpoint of ensuring antibacterial and antiviral properties.

<average particle diameter: 10 to 300 nm>

As the average particle size of the ε-Cu phase exposed to the surface is larger, Cu ions can be eluted over a long period of time, so the durability of antibacterial and antiviral properties is improved. However, when 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, there are cases where sufficient antibacterial and antiviral properties cannot 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 diameter of the ε-Cu phase is controlled to 10 nm, preferably 20 nm, and more preferably 30 nm, from the viewpoint of ensuring the persistence of elution of Cu ions.

<Maximum interparticle distance: 100 to 1000 nm>

In general, the size of bacteria is 0.5 ~ 3μm, whereas the size of viruses is very small, 10 ~ 200nm. Therefore, if the maximum distance between the particles of the ε-Cu phase exposed to the surface is too large, in particular, when a virus adheres between the particles of the ε-Cu phase exposed to the surface, sufficient antiviral properties may not be obtained. Therefore, the upper limit of the maximum distance between particles of the ε-Cu phase is controlled to 1000 nm, preferably 800 nm, and more preferably 500 nm. On the other hand, the smaller the maximum interparticle distance of the ε-Cu phase exposed to the surface, the higher the antibacterial and antiviral properties. In the case of a relatively large ε-Cu phase with an average particle diameter of 10 to 300 nm, Considering the growth process of the phase, it is considered that the lower limit of the maximum distance between particles of the ε-Cu phase is 100 nm. Therefore, the lower limit of the maximum interparticle distance of the ε-Cu phase is controlled to 100 nm, preferably 150 nm, and more preferably 200 nm.

The austenitic stainless steel material according to Embodiment 2 of the present invention preferably has a Vickers hardness of 190 Hv or less, and more preferably 180 Hv or less. Since workability can be ensured by controlling to such a Vickers hardness, it becomes possible to use for various applications.

In addition, although the lower limit of Vickers hardness is not specifically limited, It is generally 100 Hv.

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 based on JIS Z2801:2010. If it is such an antibacterial activity value, it can objectively ensure that antibacterial property is high.

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 based on ISO 21702:2019. If it is such an antiviral activity value, it can objectively ensure that antiviral property is high.

The type of austenitic stainless steel material according to Embodiment 2 of the present invention is not particularly limited, but is preferably a hot-rolled material or a cold-rolled material.

In the case of hot-rolled steel, the thickness is generally 3 mm or more. Moreover, in the case of a 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 obtaining a hot rolled material by hot rolling a slab having the above composition. Specifically, after rough rolling a slab having the above composition, a hot-rolled material is obtained by finishing hot rolling. This hot-rolled material may be wound into a coil shape.

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 performed so that the finish hot rolling end temperature becomes 850-1050 degreeC. By controlling the finish hot rolling end temperature within this temperature range, it is easy to deposit a small amount and uniformly of fine "seeds" of the epsilon-Cu phase in the cooling step from the end of finish hot rolling. As a result, by growing the ε-Cu phase in the heat treatment step, it becomes possible to control the distribution state of the ε-Cu phase on the surface as described above. On the other hand, if the finish hot rolling end temperature is less than 850°C, fine "seeds" of the ε-Cu phase are not sufficiently precipitated in the cooling step from the end of finish hot rolling. As a result, when the ε-Cu phase is grown in the heat treatment step, the average particle diameter of the ε-Cu phase or the maximum interparticle distance on the surface becomes too large. In addition, when the finish hot rolling end temperature exceeds 1050°C, the structure becomes coarse and workability and toughness deteriorate. In addition, in order to return the coarsened structure to a fine structure, several rounds of rolling treatment or heat treatment are required, resulting in an increase in manufacturing cost.

In addition, other conditions in the hot rolling process may be appropriately set depending on the composition of the slab, and are not particularly limited.

The cooling process is a process for depositing fine “seeds” of the ε-Cu phase, and is performed by cooling the hot-rolled material obtained in the hot rolling process between 900 and 500° C. at an average cooling rate of 0.2 to 5° C./sec. By cooling gently under these conditions, a small amount of fine “seeds” of the ε-Cu phase can be uniformly deposited in the ε-Cu phase precipitation temperature range (900 to 500° C.). Since the fine "seed" of this ε-Cu phase preferentially grows in the heat treatment step, a relatively large ε-Cu phase is uniformly dispersed. As a result, 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 these effects, the average cooling rate is preferably 1 to 5°C/sec, and more preferably 2 to 4°C/sec. On the other hand, 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 step, the average particle diameter of the ε-Cu phase or the maximum interparticle distance on the surface becomes too large. In addition, when cooling between 900 and 500 ° C. at an average cooling rate of less than 0.2 ° C./sec, the amount of precipitation of fine “seeds” of the ε-Cu phase increases. As a result, a large amount of relatively small ε-Cu phase is deposited in the heat treatment step.

In addition, the cooling method in a cooling process is not specifically limited, A well-known method in the said technical field can be used. For example, it becomes possible to cool gently under the cooling conditions described above by reheating only by putting a hot-rolled material wound into a coil into a holding box. Further, fine adjustment of the cooling temperature can be performed by controlling the supply amount of gas (for example, Ar gas) supplied to the thermal insulation box.

The heat treatment step is a step of growing fine “seeds” of the ε-Cu phase 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 these 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 these effects, the heating time is preferably 6 to 48 hours, and more preferably 8 to 36 hours. On the other hand, if the heating temperature is less than 750°C or the heating time is less than 4 hours, fine "seeds" of the ε-Cu phase do not grow sufficiently and the average particle diameter of the ε-Cu phase becomes too small. In addition, when the heating temperature exceeds 850°C, the ε-Cu phase is dissolved in the mother phase.

After the heat treatment step, if necessary, a surface layer removal step of acid washing and/or polishing may be further performed. By performing the surface layer removal process, the scale formed on the surface and the Cr-saved layer can be removed.

The thickness of the surface layer removed in the surface layer removal step may be appropriately adjusted depending on the composition of the slab and the like, and is not particularly limited. For example, in the case of removing the Cr sparse layer, it is preferable to remove the surface layer having a thickness of 10 μm or more.

When the austenitic stainless steel material is a cold-rolled material, after the heat treatment step, cold rolling and subsequent annealing treatment for 300 seconds or less may be further performed. In the case where the surface layer removal step is performed after the heat treatment step, the cold rolling/annealing step may be performed after the surface layer removal step, or the surface layer removal step may be performed after the cold rolling/annealing step.

By performing the annealing treatment for a short time of 300 seconds or less, strain caused by cold rolling can be removed while suppressing the influence on the ε-Cu phase exposed on the surface.

In addition, the conditions of the cold rolling and annealing treatment may be appropriately adjusted depending on the composition of the slab and the like, and are not particularly limited.

Since the austenitic stainless steel material according to Embodiment 2 of the present invention can maintain antibacterial and antiviral properties over a long period of time, it can be used for an antibacterial/antiviral member. 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 is easy to process it into a shape suitable for an antibacterial/antiviral member.

The antibacterial/antiviral member of the present invention includes the above stainless steel material (eg, ferritic stainless steel according to Embodiment 1 of the present invention and/or austenitic stainless steel according to Embodiment 2 of the present invention). do. Said stainless steel materials 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 may further include members other than the stainless steel materials described above.

Examples of the antibacterial/antiviral member include, but are not particularly limited to, various members requiring antibacterial and antiviral properties used in kitchen equipment, home appliances, medical equipment, interior building materials for buildings, transportation equipment, laboratory equipment, sanitary equipment, and the like. can

Example

Although the content of this invention is explained in detail below with reference to examples, this invention is not limited to these and is not interpreted.

<Ferritic stainless steel materials>

Stainless steel having a ferritic composition of steel grades A to J shown in Table 1 (the remainder being Fe and impurities) was melted and forged into a slab, and then the finishing temperature of finish hot rolling was controlled as shown in Table 2 to obtain a thickness of 3 mm. A hot-rolled material was obtained by hot pressing. The hot-rolled material was wound into a coil shape, quickly put into a warming box, and then cooled between 900 and 500°C at an average cooling rate shown in Table 2. The average cooling rate was adjusted by the supply amount of Ar gas supplied to the warming box. Next, the cooled hot-rolled material was subjected to heat treatment in which the cooled hot-rolled material was heated for a heating time shown in Table 2 at 800° C. in an air atmosphere using a batch annealing furnace. Next, the hot-rolled material subjected to heat treatment is cut into 100 mm (rolling direction) × 100 mm (width direction) by cutting, pickling to remove scale, polishing with P400 buff (#400), and ferrite A stainless steel material was obtained.

The following evaluation was performed about the obtained ferritic stainless steel materials.

(area ratio of ε-Cu phase exposed on the surface)

A test piece was produced by cutting out a disk with a diameter of 3 mm from a ferritic stainless steel material, grinding one side to a thickness of 0.5 mm, and electrolytically polishing the ground side. For the electrolytically polished surface of this test piece, a TEM image was taken at 10 randomly selected locations (total field area: 15 μm ² ), and then the TEM image was image analyzed to measure the area of the ε-Cu phase. The area ratio of the ε-Cu phase was calculated by dividing the area of the measured ε-Cu phase by the visual field area.

(average particle diameter of the ε-Cu phase exposed on the surface)

The average particle diameter of the ε-Cu phase was obtained by performing image analysis of the TEM image obtained in the same manner as the above area ratio to determine the equivalent circle diameter of the ε-Cu phase (30 pieces) and calculating the average value.

(maximum distance between particles of ε-Cu phase exposed on the surface)

The TEM image obtained in the same manner as the above area ratio was image analyzed, and the distance between the centers of gravity of the ε-Cu phase in the adjacent Voronoi region was measured as the distance between particles according to the above method, and the maximum value was obtained By doing so, the maximum interparticle distance of the ε-Cu phase was obtained.

(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 conducted based on JIS Z2801: 2010, and the antibacterial activity value (initial value) was determined. In the antibacterial test, Staphylococcus aureus was used as a bacterium, and a polyethylene film of 40 mm x 40 mm was used as an adhesion film. In addition, the inoculation amount of the bacterial solution was 0.4 mL, and immediately before the start of the test, the entire surface of the test piece was lightly wiped with gauze from the Japanese Pharmacopoeia in which 99% or more pure ethanol was absorbed, and the test was conducted after sufficiently drying.

In addition, in order to evaluate the persistence of the antibacterial effect, the test piece was immersed in 500 mL of water, maintained at 80 ° C. for 16 hours in a constant temperature bath, and then an antibacterial test was performed in the same manner as above, and the antibacterial activity value (after immersion in water) was determined. .

(Antiviral test: Antiviral activity value)

After cutting out a test piece of 50 mm (rolling direction) × 50 mm (width direction) from the ferritic stainless steel material, an antiviral test was conducted in accordance with ISO 21702: 2019, and the antiviral activity value (initial value) was determined. In the antiviral test, influenza A virus was used as a virus, and a polyethylene film of 40 mm x 40 mm was used as an adhesion film. In addition, the inoculation amount of the virus suspension (test solution) was 0.4 mL, and immediately before the start of the test, the entire surface of the test piece was lightly wiped with gauze from the Japanese Pharmacopoeia having absorbed 99% or more pure ethanol, and the test was conducted after sufficiently drying.

In addition, in order to evaluate the persistence of the antiviral effect, the test piece was immersed in 500 mL of water, maintained at 80 ° C. for 16 hours in a constant temperature bath, and then an antiviral test was performed in the same manner as above, and the antiviral activity value (after immersion in water ) was obtained.

(Vickers Hardness)

Vickers hardness was measured based on JIS Z2244:2009. The measurement was performed using a Vickers hardness tester Hv-100 manufactured by Mitutoyo Co., Ltd., measuring the Vickers hardness of the surface at 10 randomly selected locations with a measurement load of 10 kg, and taking the average value as the result.

Table 3 shows the above evaluation results.

As shown in Table 3, since the ferritic stainless steel materials (examples of the present invention) of Nos. 1-1 to 1-11 had a predetermined composition and a distribution state of the ε-Cu phase on the surface, the antibacterial activity value The results of (initial and after water immersion), antiviral activity value (initial and after water immersion) and Vickers hardness were all good.

On the other hand, in the ferritic stainless steel materials (comparative examples) of No. 1-12, the finish hot rolling end temperature was too low and the average cooling rate was too large, so the maximum distance between grains of the ε-Cu phase was too large. As a result, antiviral properties (antiviral activity value of 2.0 or more) were not obtained.

In No. 1-13 and No. 1-14 ferritic stainless steel materials (comparative examples), the average cooling rate was too large, so the average particle size of the ε-Cu phase and the maximum distance between particles became large. As a result, antiviral properties (antiviral activity value of 2.0 or more) were not obtained.

Since the ferritic stainless steel materials (comparative example) of No. 1-15 had too small average cooling rate, the maximum interparticle distance of the epsilon-Cu phase became small. As a result, the antibacterial activity value and the antiviral activity value after water immersion were low, and the effect of maintaining antibacterial and antiviral properties was not sufficient.

Since the ferritic stainless steel materials (comparative examples) of No. 1-16 and 1-17 did not have a predetermined composition, the distribution state of the epsilon-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.

In No. 1-18 (Comparative Example), cracks occurred during hot rolling, and ferritic stainless steel materials could not be manufactured.

<Austenitic stainless steel materials>

Stainless steel having an austenitic composition of steel grades a to j shown in Table 4 (the balance being Fe and impurities) was melted and forged to obtain a slab, and then the finishing temperature of finish hot rolling was controlled as shown in Table 5 to obtain a thickness Hot-rolled steel was obtained by hot pressing to a thickness of 3 mm. The hot-rolled material was wound into a coil shape, quickly put into a warming box, and then cooled between 900 and 500°C at an average cooling rate shown in Table 5. The average cooling rate was adjusted by the supply amount of Ar gas supplied to the warming box. Next, heat treatment was performed to heat the cooled hot-rolled material using a batch annealing furnace in an air atmosphere at 800° C. for a heating time shown in Table 5. Next, the hot-rolled material subjected to heat treatment is cut into 100 mm (rolling direction) × 100 mm (width direction) by cutting, pickling to remove scale, and polishing with P400 buff (#400) to finish austen A nitrite-based stainless steel material was obtained.

About the obtained austenitic stainless steel material, the same evaluation as said ferritic stainless steel material was performed. The evaluation results are shown in Table 6.

As shown in Table 6, since the austenitic stainless steel materials (examples of the present invention) of Nos. 2-1 to 2-11 had a predetermined composition and a distribution state of the ε-Cu phase on the surface, antibacterial activity The results of values (initial and after water immersion), antiviral activity values (initial and after water immersion) and Vickers hardness were all good.

On the other hand, since the austenitic stainless steel material of No. 2-12 (Comparative Example) had a too low finish hot rolling end temperature and too large an average cooling rate, the average grain 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.

Since the austenitic stainless steel materials (comparative examples) of Nos. 2-13 and 2-14 had too large an average cooling rate, the maximum distance between grains of the ε-Cu phase became large. As a result, antiviral properties (antiviral activity value of 2.0 or more) were not obtained.

Since the austenitic stainless steel material (comparative example) of No. 2-15 had too small average cooling rate, the average grain size of the epsilon-Cu phase became small. As a result, the antibacterial activity value and the antiviral activity value after water immersion were low, and the effect of maintaining antibacterial and antiviral properties was not sufficient.

Since the austenitic stainless steel materials (comparative examples) of Nos. 2-16 and 2-17 did not have a predetermined composition, the distribution state of the epsilon-Cu phase on the surface could not be properly controlled. 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.

Since No. 2-18 (Comparative Example) did not have a predetermined composition, cracks occurred during hot rolling, and an austenitic stainless steel material could not be manufactured.

As can be seen from the above results, according to the present invention, a stainless steel material capable of maintaining antibacterial and antiviral properties over a long period of time, a manufacturing method thereof, and an antibacterial/antiviral member can be provided.

10: stainless steel
11: ε-Cu phase
12: passivation film

Claims (15)

Has an ε-Cu phase exposed on the surface,
The ε-Cu phase on the surface 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. The method of claim 1,
Based on mass, 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% or less, Cr: 10.00 to 32.00%, Cu: 0.40 A stainless steel material having a composition comprising ~6.00%, the balance being Fe and impurities. The method of claim 2,
A ferritic stainless steel material having a C content of 0.10% or less, a Mn content of 2.00% or less, a Ni content of 4.00% or less, and a Cu content of 0.40 to 4.00%. The method of claim 3,
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% or less, Sn: 0.50% or less, Al: 5.00% Hereinafter, 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, further comprising at least one selected from stainless steel materials. According to claim 3 or claim 4,
Stainless steel materials having a Vickers hardness of 160 Hv or less. The method of claim 2,
An austenitic, stainless steel material with a Ni content of 4.00 to 20.00% and a Cu content of 2.00 to 6.00%. The method of claim 6,
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% or less, Sn: 0.50% or less, Al: 5.00% Hereinafter, Zr: 0.50% or less, Co: 0.50% or less, B: 0.020% or less, Ca: 0.10% or less, REM: 0.20% or less, further comprising one or more selected from stainless steel materials. According to claim 6 or claim 7,
Stainless steel materials with a Vickers hardness of 190 Hv or less. The method according to any one of claims 1 to 8,
A stainless steel material having an antibacterial activity value of 2.0 or more in an antibacterial test based on JIS Z2801:2010. The method according to any one of claims 1 to 9,
A stainless steel material having an antiviral activity value of 2.0 or more in an antiviral test based on ISO 21702:2019. Based on mass, 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% or less, Cr: 10.00 to 32.00%, Cu: 0.40 4.00%, the balance being Fe and impurities, or, on a 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 to 20.00%, Cr: 10.00 to 32.00%, Cu: 2.00 to 6.00%, the balance being Fe and impurities. Hot rolling to obtain a hot rolled steel by hot rolling a slab having an austenitic composition. As a step, when the composition of the slab is ferritic, the finish hot rolling end temperature is set to 700 to 900 ° C., and when the slab is austenitic, the finish hot rolling end temperature is set to 850 to 1050 ° C.;
A cooling step of cooling the hot-rolled material obtained in the hot rolling step between 900 and 500 ° C. at an average cooling rate of 0.2 to 5 ° C./sec;
Heat treatment process of heating the hot-rolled material cooled in the cooling process at 750 to 850 ° C. for 4 hours or more
Including, the manufacturing method of the stainless steel material. The method of claim 11,
In the slab having the ferritic composition, 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 ,
In the slab having the austenitic composition, 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, REM: 0.20% or less To do, the manufacturing method of stainless steel materials. According to claim 11 or claim 12,
A method for producing a stainless steel material, further comprising a surface layer removal step of performing pickling and/or polishing after the heat treatment step. The method according to any one of claims 11 to 13,
The manufacturing method of stainless steel materials which further includes the cold rolling/annealing process which performs cold rolling after the said heat treatment process, and then performs an annealing process for 300 seconds or less. An antibacterial/antiviral member comprising the stainless steel material according to any one of claims 1 to 10.

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