JP3398620B2 - Stainless steel material excellent in antibacterial property and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel material, and more particularly to a stainless steel material which has excellent antibacterial properties and is suitable for use in daily life-related products such as kitchens, medical equipment, electrical equipment, chemical equipment and building materials, and a method for producing the same. . The steel material in the present invention includes a steel plate, a steel strip, a steel pipe, and a steel wire.

[0002]

2. Description of the Related Art It has been conventionally known that silver and copper have an effect of suppressing the growth of pathogenic bacteria represented by Escherichia coli and Salmonella and preventing food poisoning caused by pathogenic bacteria. Recently, a material has been proposed which utilizes these metals and has a bacterial growth inhibitory effect (hereinafter referred to as antibacterial property). For example, in Japanese Unexamined Patent Publication No. 8-49085, by magnet sputtering, Cr containing Ag and / or Cu,
A stainless steel sheet having excellent antibacterial properties is disclosed in which a metal layer or alloy layer of Ti, Ni, Fe or the like is formed on the surface of a stainless steel base material. In this steel sheet, it is preferable to form a metal layer or an alloy layer containing 19 to 60% by weight of Ag.

Further, Japanese Unexamined Patent Publication No. 8-156175 proposes a coated steel sheet which can be coated with a pigment containing silver to suppress the growth of bacteria. However, in the method of forming a metal layer or an alloy layer containing an antibacterial metal on the surface of the steel sheet described above, or in the method of applying a pigment containing an antibacterial metal, a layer containing an antibacterial metal is drawn by polishing or surface polishing. There is a problem that the effect cannot be expected because it is peeled off or removed.In addition, the surface is always rubbed for cleaning in applications such as steel plates used in the interior of washing machines and for cleaning in kitchen appliances. In some applications, the antibacterial property cannot be maintained for a long period of time. Further, in the above-mentioned method, the number of manufacturing steps is increased in comparison with the conventional method in order to form a coating or a metal layer or an alloy layer, and the surface area per unit weight becomes larger as the plate thickness becomes thinner. There are many layers and alloy layers, which is disadvantageous in terms of cost.

In order to solve the above problems, Japanese Patent Laid-Open No. 8-10
Japanese Patent No. 4953 discloses an austenitic stainless steel containing 1.1 to 3.5% by weight of Cu to improve antibacterial properties.
In Japanese Patent No. 104952, a martensitic stainless steel containing 0.3 to 5% by weight of Cu to improve antibacterial property is disclosed in
In 9-170053, a ferritic stainless steel containing 0.4 to 3.0% by weight of Cu and having improved antibacterial properties is proposed.

[0005]

SUMMARY OF THE INVENTION
In the techniques described in JP-A-8-104953 and JP-A-8-104952 and JP-A-9-170053, it is necessary to dissolve Cu as ions from the surface of the steel sheet in order to exhibit antibacterial properties. The elution of Cu as an ion means that the passivation film is destroyed at that location, and therefore the antibacterial property is improved but the corrosion resistance is significantly deteriorated. Therefore, it was difficult to achieve both antibacterial property and corrosion resistance in the Cu-added stainless steel.

The present invention advantageously solves the above-mentioned problems of the prior art, has both excellent corrosion resistance and antibacterial property, and is still excellent antibacterial even when subjected to the currently widely used surface treatment including polishing. An object of the present invention is to provide a stainless steel material having properties and a method for producing the same.

[0007]

In order to develop a stainless steel plate having both excellent antibacterial properties and corrosion resistance, the present inventors have been particularly interested in analysis devices such as field emission Auger electron spectroscopy devices and electron beam microanalyzers. As a result of earnestly researching the relationship between the chemical composition of the surface of the stainless steel sheet and the antibacterial property, the appropriate amount of Ag was added to the stainless steel,
It has been newly found that a proper amount of silver oxide is uniformly dispersed on the surface of the stainless steel plate and the steel plate to obtain a stainless steel plate having high antibacterial property and excellent corrosion resistance.
Further, the present inventors have found that the continuous casting speed and the addition of V have a great influence on the uniform dispersion of silver oxide. Further, the inventors of the present invention have found that a steel sheet in which an appropriate amount of silver oxide is uniformly dispersed in the steel sheet has a stable antibacterial property even in applications where molding processing, polishing processing is performed, and applications where the surface is rubbed or scraped off during use. I found that I showed sex.

The present invention has been completed by further studies based on the above findings. That is, the first invention is a stainless steel material containing 0.001 to 0.30 wt% of Ag, wherein the steel material contains 0.0005 wt% or more of silver oxide, 1.1 ×
(Wt% Ag) Contains less than wt% , the silver oxide is uniform in the steel material
It dispersed have an excellent stainless steel antimicrobial characterized by Rukoto. From the viewpoint of obtaining better antibacterial properties, the size of the silver oxide is preferably 500 μm or less.

The second aspect of the present invention is Ag: 0.001 to 0.30.
wt%, further V: 0.001-1.0 wt%, preferably
A stainless steel material containing 0.001 to 0.30 wt%,
The steel contains 0.0005 wt% or more of silver oxide, 1.1 x (wt% Ag)
It is a stainless steel material having excellent antibacterial properties, characterized in that the content of wt% or less and the silver oxide is uniformly dispersed in the steel material, and the size of the silver oxide is 500 μm or less. Is preferred.

The third aspect of the present invention is Ag: 0.001 to 0.30.
In order to continuously cast a molten stainless steel containing Vt in the range of 0.001 to 1.0% by weight, preferably 0.001 to 0.30% by weight, into a steel material, the S content of the molten steel is 0.015% by weight. In addition to the following, the method for producing a stainless steel material is characterized in that the casting speed of the continuous casting is 0.8 to 1.6 m / min.

The fourth aspect of the present invention is a method for producing a stainless cold-rolled steel sheet, comprising the steps of continuously casting molten stainless steel into a steel material, and then hot rolling and cold rolling the molten stainless steel, wherein the molten stainless steel is S: At 0.015 wt% or less, Ag: 0.001 to 0.
Stainless steel molten steel containing 30 wt% or V: 0.001 to 1.0 wt% and having excellent antibacterial property, characterized in that the casting speed of the continuous casting is 0.8 to 1.6 m / min. It is a method of manufacturing a cold rolled steel sheet.

[0012]

The reasons for limiting the chemical composition of the steel material of the present invention will be described. From the viewpoint of corrosion resistance, the stainless steel material of the present invention preferably contains 10 wt% or more of Cr, austenitic stainless steel, ferritic stainless steel, martensitic stainless steel are preferable, and other stainless steels are also preferable. is there.

The chemical composition of the austenitic stainless steel is C: 0.001 to 0.1 wt%, Si: 2.0 wt% or less, Mn: 2.
0 wt% or less, P: 0.1 wt% or less, Cr: 10 to 35 wt%, Ni:
It is preferable to contain 6 to 15 wt% and N: 0.001 to 0.1 wt% with the balance being Fe and unavoidable impurities. Mo: 3.0
wt% or less, Cu: 1.0 wt% or less, W: 0.30 wt% or less, Al:
0.3 wt% or less, Ti: 1.0 wt% or less, Nb: 1.0 wt% or less,
Zr: 1.0wt% or less, Co: 0.001-0.5wt%, B: 0.01wt
You may contain 1 type (s) or 2 or more types in% or less.

The chemical composition of ferritic stainless steel is
C: 0.0001 to 0.1 wt%, Si: 1.0 wt% or less, Mn: 2.0 wt%
% Or less, P: 0.1 wt% or less, Cr: 10 to 50 wt%, N: 0.10.
It is preferable that the content of Fe and the unavoidable impurities be the balance of Fe and unavoidable impurities. Al: 0.3 wt% or less, Ni: 1.0 wt% or less, Mo: 3.0 wt% or less, Ti: 1.0 wt% or less, Nb: 1.0 wt%
% Or less, Zr: 1.0 wt% or less, Cu: 1.0 wt% or less, W: 0.
One or more of 30 wt% or less, Co: 0.001 to 0.5 wt% and B: 0.01 wt% or less may be contained.

The chemical composition of martensitic stainless steel is C: 0.001 to 1.0 wt%, Si: 1.0 wt% or less, Mn: 2.
0 wt% or less, P: 0.1 wt% or less, Cr: 10 to 19 wt%, N:
It is preferable to contain 0.001 to 0.1 wt% and the balance Fe and unavoidable impurities. Al: 1.5 wt% or less, Ti: 1.
0 wt% or less, Nb: 1.0 wt% or less, W: 0.3 wt% or less, Z
r: 1.0 wt% or less, Ni: 3.0 wt% or less, Mo: 3.0 wt% or less, Cu: 1.0 wt% or less, Co: 0.001 to 0.5 wt%, B: 0.
You may contain 1 type (s) or 2 or more types among 01 wt% or less.

In the present invention, stainless steel, preferably stainless steel having a chemical composition within the above range, is further added with Ag: 0.001 to 0.30 wt%, or further V: 0.001.
˜1.0 wt% and silver oxide 0.0005 wt% or more and 1.1 × (wt% Ag) wt% or less. In addition, 1.1
× (wt% Ag) is the Ag content in the stainless steel (wt%)
Means 1.1 times. As a result, a markedly high antibacterial property can be stably expressed without deterioration in corrosion resistance.

Ag: 0.001 to 0.30 wt% Ag is the most important element in the present invention, has the effect of suppressing the growth of bacteria, and enhances the antibacterial property. These effects are observed when the content is 0.001 wt% or more, but 0.30
If it is contained in excess of wt%, the corrosion resistance deteriorates, surface defects during hot rolling increase, and a large amount of expensive Ag is added, which is disadvantageous in terms of cost. Therefore, Ag is
It was limited to the range of 0.001 to 0.30 wt%. Further, in order to improve the corrosion resistance, Ag is preferably less than 0.05 wt%.

Ag contained in the steel material is Ag (silver) particles,
Although present in the form of silver oxide and silver sulfide, the present inventors have found that the antibacterial action is excellent in the order of silver oxide> silver particles> silver sulfide, and in the present invention, the antibacterial action is remarkably high. Most of the Ag contained to improve antibacterial properties is present as silver oxide. The details of the reason why the antibacterial action is superior in the order of silver oxide, silver particles, and silver sulfide are currently unknown,
It is presumed that the difference in the ionization rate of the silver compound containing silver particles resulted in the difference in the elution rate of Ag ions having an antibacterial action, and appeared as a difference in the antibacterial action.

Therefore, in the present invention, the silver oxide is contained in the steel material in an amount of 0.0005 wt% or more and 1.1 × (wt% Ag) wt% or less. If the above-mentioned amount of silver oxide is uniformly dispersed in the steel material, not only the surface at the time of product shipment but also the surface after polishing, cutting and grinding, or a new surface is formed due to abrasion, etc. Even on the surface, the silver oxide is always present on the surface of the steel material, the growth of bacteria is suppressed, and the antibacterial property is significantly improved. The silver oxide is exemplified by AgO or Ag ₂ O.

If the content of silver oxide having an excellent antibacterial action is 0.0005 wt% or more, good antibacterial property can be obtained. If the content of silver oxide is less than 0.0005 wt%, a sufficient effect of suppressing bacterial growth cannot be expected, and it becomes necessary to add a large amount of Ag exceeding 0.30 wt% to supplement the effect, resulting in a decrease in corrosion resistance. From such a point, the lower limit of the content of silver oxide is limited to 0.0005 wt%. On the other hand, when the content of silver oxide exceeds 1.1 × (wt% Ag) wt%, the silver oxide tends to collect at grain boundaries and the like, and coarse oxide tends to be formed, resulting in deterioration of corrosion resistance. In order to fully bring out the antibacterial action of silver oxide, the upper limit of silver oxide content was limited to 1.1 x (wt% Ag) wt%. here
wt% Ag is the Ag content in steel.

The shape of the silver oxide contained in the steel is not particularly limited, but the size of the silver oxide is 50.
If it exceeds 0 μm, the corrosion resistance may be deteriorated, so that the size is preferably 500 μm or less. In addition,
The production amount of Ag oxide in the steel material in the present invention, inclusion analysis by the electrolytic extraction method, or any cross section of the test piece collected from the steel material, evaluated by a field emission Auger electron spectroscope or electron beam microanalyzer I shall.

In the present invention, in addition to Ag in the above range,
Further, it is desirable to contain V: 0.001 to 1.0 wt%. Fig. 1 shows that 16.2wt% Cr stainless steel slab containing 0.042wt% Ag is hot-rolled, hot-rolled sheet annealed (850 ℃ × 60sec.
), Cold rolling, bright annealing (850 ° C x 60 sec)
The results of examining the effect of V addition on the antibacterial property of stainless steel used as a 1.0 mm BA (Bright Annealing) product in the surface layer and the center of the plate thickness are shown.

In the central part of the plate thickness, stable antibacterial properties can be obtained regardless of whether or not V is added, while in the surface part,
If the amount of V added is less than 0.001% by weight, the antibacterial activity is reduced.
This is considered to be because V has a so-called dispersant effect, which markedly improves the tendency of silver particles, silver oxides, and silver sulfides to be unevenly distributed in the central portion of the plate thickness. On the other hand, 0.
Above 30wt%, the above effects saturate and 1.0wt
If it exceeds%, the workability and corrosion resistance tend to deteriorate. Therefore, it is desirable that V be in the range of 0.001 to 1.0 wt%. The content is preferably 0.001 to 0.30 wt%, more preferably 0.01 to 0.25 wt%.

The stainless steel material of the present invention comprises the balance Fe and inevitable impurities, except for the chemical composition within the above range. The steel material of the present invention can be melted by applying all known melting methods, and thus the melting method is not particularly limited. For example, as a steelmaking method, the steel is melted in a converter, an electric furnace, or the like, and SS-VOD (Strongly Stirred Vacuum Oxygen Decarbu
It is preferable to carry out secondary refining by rrization).

In the present invention, a stainless steel composition is further provided.
Ag: 0.001 to 0.30 wt% included, or V: 0.00
Molten stainless steel containing 1 to 1.0 wt% is melted by a commonly known melting method. The melted molten steel can be made into a steel material by a generally known casting method, but it is preferable to apply the continuous casting method from the viewpoint of productivity and quality. In the continuous casting method, the casting speed is set in the range of 0.8 to 1.6 m / min in order to finely and uniformly disperse 0.0005 wt% or more of silver oxide in the steel. The casting speed should be in the range of 0.8 to 1.6 m / min, and the S content of the molten stainless steel should be 0.015 wt.
% Or less, preferably 0.010 wt% or less.

When the pouring speed is less than 0.8 m / min, the silver oxide becomes coarse and the corrosion resistance deteriorates, and it becomes difficult to stably develop the antibacterial property. On the other hand, the casting speed is 1.
If it exceeds 6m / min, stable casting is difficult and 0.0005
More than wt% of silver oxide is not uniformly dispersed in the steel. Therefore, the silver oxide is unevenly dispersed on the surface of the steel material during use, so that the antibacterial property is not stably exhibited. For this reason, it is desirable that the casting speed in the continuous casting method be in the range of 0.8 to 1.6 m / min.

The amount of silver oxide is 0.0005 wt% or more, 1.1 × (wt
% Ag) wt% or less, the casting speed should be set to 0.
8 to 1.6 m / min and S content of the molten stainless steel is 0.015wt% or less, preferably 0.010wt%
The following is preferable. Adjustment of S content in molten steel is
A generally known smelting method may be used, and although not particularly limited, a method of adding ferrosilicon and a calcium compound in a converter and / or a VOD furnace and desulfurizing is preferable.

S content of molten steel is 0.015 wt%
When it exceeds, the amount of silver sulfide generated by reacting with silver is increased, and the amount of silver oxide excellent in antibacterial action is suppressed, so that the antibacterial property is deteriorated. Therefore, in order to obtain good antibacterial properties, it is preferable that the S concentration in the molten steel be 0.015 wt% or less. In the present invention, molten stainless steel having the above chemical composition is preferably continuously cast under the above conditions to obtain a steel material, and if necessary, the steel material is heated to a predetermined temperature, and then hot rolled. A hot rolled plate having a desired plate thickness is obtained by rolling. The hot-rolled sheet is preferably annealed at 700 to 1200 ° C., if necessary, and then used as a hot-rolled sheet as it is, or subjected to cold rolling to be a cold-rolled sheet having a predetermined sheet thickness, It is used as desired.

The cold rolled sheet is preferably annealed at 700 to 1200 ° C. and pickled to obtain a cold rolled annealed sheet.

[0030]

Example A stainless steel having the chemical composition shown in Table 1 was melted and made into a slab (steel material) having a thickness of 200 mm by a continuous casting method in which the casting speed was changed, and then the slab was heated and hot rolled. A hot rolled plate having a plate thickness of 4 mm was used. Next, the hot rolled sheet was annealed at 700 to 1200 ° C., pickled and cold rolled to obtain a cold rolled sheet having a thickness of 0.8 mm. Next, this cold rolled sheet was annealed and, if necessary, pickled to obtain cold rolled annealed sheets with various surface finishes. The annealing temperature of the cold-rolled sheet was 1000 to 1200 ° C for austenitic stainless steel, 800 to 1100 ° C for ferritic stainless steel, and 750 to 1000 ° C for martensitic stainless steel. Note that some steel sheets were further subjected to polishing processing in accordance with JIS R 6001
Abrasive with 320 or # 400 finish.

Corrosion resistance tests and antibacterial tests were carried out on these cold rolled annealed plates. In addition, in order to confirm the durability and durability of the antibacterial property, the antibacterial property test was conducted again after the corrosion resistance test. The test method of each test is shown below. (1) Antibacterial property test The antibacterial property was evaluated according to the film adhesion method of the Society for Inorganic Antibacterial Agents such as silver. The procedure of the film adhesion method of the Society for Studying Inorganic Antibacterial Agents such as silver is as follows.

A 25 cm ² test piece is washed and degreased with absorbent cotton containing 99.5% ethanol. E. coli is dispersed in 1/500 NB solution. (The number of bacteria is 2.
The concentration was adjusted to 0 × 10 ^{5 to} 1.0 × 10 ⁶ cfu (colony from unite) / ml. 1/500 NB solution is normal Bion medium (N
B) was diluted 500 times with sterile purified water. Normal Bion medium (NB) means meat extract 5.0g, sodium chloride 5.0g, peptone 10.0g, purified water 1.000ml, pH: 7.0 ±
It means 0.2. ) Inoculate the test specimens (3 each) at a rate of 0.5 ml / 25 cm ² .

The surface of the test body is covered with a coating film. The test specimen is stored for 24 hours under the conditions of a temperature of 35 ± 1.0 ° C. and a relative humidity (RH) of 90% or more. Determine the viable cell count by the agar culture method (35 ± 1.0 ° C, 40 to 48 hours). The antibacterial property was evaluated by the sterilization rate defined by the following formula.

Sterilization rate (%) = (number of control bacteria-number of bacteria after test) / (number of control bacteria) × 100 The number of control bacteria is an antibacterial test using a stainless steel plate without addition of Ag. It is the viable cell count after performing. The stainless steel sheet without Ag used is SUS430 (steel N
o.40), austenitic SUS 304 (steel No. 13
), And martensite type is SUS 410 (steel No.23). The initial bacterial count of each test piece is about 2.3 × 10 ⁵ cfu / plate. The bacterial count after the test is the measured viable bacterial count.

A similar antibacterial test was carried out using the test body after the corrosion resistance test, and the persistence of antibacterial property was similarly evaluated. (2) Corrosion resistance test Corrosion resistance was evaluated by a salt dry-wet combined cycle test.
The test piece is sprayed with a 5.0% NaCl aqueous solution (temperature: 35 ° C) for 0.5 hr and then kept for 1.0 hr in a dry atmosphere with a humidity of 40% or less and a temperature of 60 ° C.

In a humid atmosphere with a humidity of 95% or more and a temperature of 40 ° C.
Hold for 1.0hr. Was repeated for a plurality of cycles set for each steel type, and then the rusting area ratio (%) on the surface of the test piece was measured. The number of repeated cycles is 10 cycles for ferritic stainless steel and 10 cycles for austenitic stainless steel.
30 cycles and 5 cycles for martensitic stainless steel.

The results are shown in Table 2.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

[0041]

[Table 4]

In the finishing state of the steel sheet surface in the table, 2B and BA show the finishing state according to JIS G 4305, and # 320 or # 400 shows the finishing state of polishing according to JIS R 6001. Show. Steel sheet containing Ag within the scope of the present invention and containing an amount of silver oxide within the scope of the present invention (Example of the present invention) is excellent in workability and corrosion resistance, and has an E. coli count of 99% or more in an antibacterial test. It can be confirmed that the antibacterial property is reduced and the antibacterial property is excellent, and the E. coli is also decreased in the test body after the corrosion resistance test, and the antibacterial property is also excellent in sustainability. Further, it can be confirmed that the antibacterial property continues regardless of the finished state of the steel sheet surface, and that it has sufficient antibacterial property even after polishing.

The above results can be confirmed in various types of stainless steel such as austenite type, ferritic type, martensitic type and other various stainless steels, regardless of the type of stainless steel. On the other hand, in Comparative Examples outside the scope of the present invention, regardless of the type of stainless steel, the decrease of E. coli is small and the antibacterial property is deteriorated, or the antibacterial property after the corrosion resistance test is decreased, and the antibacterial property is deteriorated. is doing.

[0044]

Industrial Applicability According to the present invention, it is possible to provide a stainless steel material having excellent antibacterial properties without deteriorating the corrosion resistance and having excellent antibacterial properties even when subjected to surface treatment including polishing. It has a remarkable effect. INDUSTRIAL APPLICABILITY The stainless steel material of the present invention is suitable for a member that has been subjected to molding and polishing and is used in applications where hygiene is important in a wet environment such as a kitchen or a bath.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the sterilization rate and the V content in the steel plate surface layer and the central portion.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-11-12692 (JP, A) JP-A-10-259456 (JP, A) JP-A-11-29879 (JP, A) JP-A-9- 249948 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C22C 38/00 302 A01N 59/16 B22D 11/00 B22D 11/20

Claims (4)

(57) [Claims] 1. A stainless steel material containing 0.001 to 0.30 wt% of Ag, wherein the steel material contains 0.0005 wt% or more of silver oxide, and 1.1.
X (wt% Ag) wt% or less , the silver oxide is evenly distributed in the steel.
Excellent stainless steel antimicrobial characterized that you have to one dispersed. 2. A stainless steel material containing Ag: 0.001 to 0.30 wt% and further containing V: 0.001 to 1.0 wt%, the steel material containing 0.0005 wt% or more of silver oxide, 1.1 × (wt% A
g) wt% or less , the silver oxide is uniformly dispersed in the steel material.
Antimicrobial excellent stainless steel, characterized in Tei Rukoto. 3. A stainless steel molten steel containing Ag: 0.001 to 0.30 wt% or V: 0.001 to 1.0 wt% is continuously cast into a steel material, and the S content of the stainless steel molten steel is 0.015. A method for producing a stainless steel material, characterized in that the casting rate of the continuous casting is 0.8 to 1.6 m / min while being less than or equal to wt%. 4. A method for producing a stainless cold-rolled steel sheet, comprising the steps of continuously casting molten steel of stainless steel into a steel material, and then hot rolling and cold rolling the molten steel.
It is a stainless steel molten steel containing 0.015 wt% or less, Ag: 0.001 to 0.30 wt%, or V: 0.001 to 1.0 wt%, further, the casting speed of the continuous casting is 0.8 to
A method for producing a stainless cold-rolled steel sheet having excellent antibacterial properties, which is characterized by being 1.6 m / min.