JP2001011660A - Production of stainless steel excellent in antibacterial property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing stainless steel excellent in antibacterial properties and corrosion resistance. SOLUTION: A stainless cold rolled steel sheet contg. 0.001 to 0.10 wt.% Ag is subjected to annealing treatment in an oxidizing atmosphere and is thereafter immersed into an aq.soln. of nitrohydrofluoric acid contg. 0.0001 to 1.0 mol/l silver ions, 20 to 200 g/l nitric acid and 5 to 100 g/l hydrofluoric acid which does not form a complex with metallic ions. Or, after annealing treatment and descaling treatment, immersing treatment in which it is immersed into a soln. of nitric acid contg. 0.0001 to 1.0 mol/l silver ions or a soln. of sodium hydroxide contg. 0.0001 to 1.0 mol/l silver ions may be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel sheet, and more particularly to a stainless steel sheet having excellent antibacterial properties and being suitable for use in daily necessities, medical equipment and building materials. The stainless steel sheet in the present invention includes a steel sheet, a steel strip, a steel pipe, and a steel wire.

[0002]

2. Description of the Related Art It has long been known that silver (Ag) and copper (Cu) have an action of suppressing the growth of pathogenic bacteria represented by Escherichia coli and Salmonella. Recently, materials having an effect of inhibiting bacterial growth (hereinafter referred to as antibacterial properties) using these metals have been developed. For example, JP-A-8-4908
No. 5 publication, Ag sputtering by magnet sputtering
A stainless steel sheet having excellent antibacterial properties in which a metal layer or an alloy layer of Cr, Ti, Ni, Fe or the like containing Cu is formed on the surface of a stainless steel base material is disclosed. In this steel sheet, it is preferable to form an alloy layer or a metal layer containing 19 to 60% by weight of Ag.

Further, Japanese Patent Application Laid-Open No. 8-156175 proposes a coated steel sheet which can suppress the propagation of bacteria by applying a pigment containing silver. However, in the above-described method of forming an alloy layer or a metal layer containing an antibacterial metal on the surface of a steel sheet, or a method of applying a pigment containing an antibacterial metal, a layer containing the antibacterial metal is formed by drawing or polishing the surface. Is removed or removed, and the effect cannot be expected. Further, in applications such as kitchen supplies, there is also a problem that the antibacterial property cannot be maintained for a long time because the surface is rubbed by cleaning.

[0004] JP-A-8-239726 discloses that the weight ratio is
Iron: 10 to 80%, Aluminum: 1 to 10%, or further contains 1 to 15% of any one or more of chromium, nickel, manganese, and silver, with the balance being copper and unavoidable impurities, antibacterial and sea resistant A living material is disclosed. However, this material is a copper-based alloy or an iron-based alloy containing 1 to 10% of aluminum, and has low workability. For example, there is a problem in providing a use for forming a thin plate such as tableware, kitchenware, and electric parts. Had left.

To cope with such a problem, Japanese Unexamined Patent Publication No. Hei 8-104953 discloses an austenitic stainless steel containing 1.1 to 3.5% by weight of Cu and having an improved antibacterial property.
No. 457 discloses that Cu is 0.5 to 4.0% by weight and Ag is 0.05 to 1.0% by weight.
The austenitic stainless steel containing anti-bacterial property by weight percent contains Cu.
-5.0% by weight of martensitic stainless steel having improved antibacterial properties, and JP-A-9-170053 discloses that
Ferritic stainless steel containing 0.4 to 3.0% by weight and having improved antibacterial properties has been proposed.

However, in order to exhibit antibacterial properties, it is necessary for Cu to be dissolved as ions from the surface of the steel sheet. The dissolution of Cu as ions means that the passive film is destroyed at that location, and even if the antibacterial property is improved, the corrosion resistance is significantly deteriorated. Therefore, it was difficult to achieve both antibacterial properties and corrosion resistance in stainless steel containing a large amount of Cu.

[0007] Japanese Patent Application Laid-Open No. Hei 10-259456 discloses a composition containing 8% by weight or more of Cr and 0.05 to 1.0% by weight of Ag and having a minor axis of 10%.
An antibacterial stainless steel sheet in which an Ag phase of μm or less is dispersed in a matrix in an area fraction of 0.03% or more has been proposed.
However, in the technique described in JP-A-10-259456, it is practically difficult to control the minor axis of the Ag phase to 10 μm or less, and the area ratio of the Ag phase having the minor axis of 10 μm or less is 0.03% or less.
In order to achieve the above, a large amount of Ag must be added, and as a result, there is a problem that workability, corrosion resistance, and surface properties are reduced.

[0008]

Generally, a stainless steel material is made into a final product through a descaling step by pickling or the like. In the case of a 2B, 2D finished stainless steel material,
After cold rolling, it is annealed in an oxidizing atmosphere and then descaled by pickling or the like to obtain a product. Antibacterial elements such as Cu and Ag that exist in the steel surface layer cannot be dissolved as ions when the steel surface is covered with an oxide film that remains after pickling, and the surface layer portion is more insoluble than the inner layer. Antibacterial properties may be significantly reduced. In addition, the antibacterial element (Ag) may disappear from the surface layer during annealing, and a region having a low concentration of the antibacterial element may be formed on the surface layer. However, there is a problem that the antibacterial element concentration is not sufficiently recovered even if the varnish is exposed, so that sufficient antibacterial properties may not be obtained.

The present invention advantageously solves the above-mentioned problems of the prior art, and provides a method for producing a stainless steel sheet having a relatively small Ag content and having enhanced antibacterial properties in the surface layer of the final product and having excellent antibacterial properties and corrosion resistance. The purpose is to provide.

[0010]

Means for Solving the Problems The present inventors have developed a stainless steel sheet which has been annealed in an oxidizing atmosphere.
We conducted intensive research to achieve both antibacterial properties and corrosion resistance. As a result, the present inventors made the stainless steel cold-rolled steel sheet contain a small amount of Ag, and further performed descaling treatment as an immersion treatment in a nitric hydrofluoric acid aqueous solution containing an appropriate amount of Ag ions, or Ag after the descaling treatment. By performing the immersion treatment of immersion in a solution containing an appropriate amount of ions, the appropriate amount of Ag particles can be present on the surface of the stainless steel sheet after the descaling treatment, and the stainless steel sheet can be formed without deteriorating the corrosion resistance. It has been found that the antibacterial properties can be significantly improved.

The present invention has been completed based on the above findings. That is, in the present invention, Ag: 0.001 to 0.
In a method for manufacturing a stainless steel sheet in which a stainless steel cold-rolled steel sheet containing 10 wt% is subjected to annealing treatment in an oxidizing atmosphere and then descaling treatment, the descaling treatment is performed by using Ag ions: 0.0001 to 1.0 mol / l. And nitric acid: in an aqueous nitric acid solution containing 20 to 200 g / l, or nitric acid: 20 to 200 g / l
200 g / l, hydrofluoric acid not forming a complex with metal ions: 5 to
A method for producing an antibacterial stainless steel sheet, which is a descaling treatment in which the cold-rolled stainless steel sheet is immersed in an aqueous nitric hydrofluoric acid solution containing 100 g / l.

The present invention also relates to a method for producing a stainless steel sheet, comprising subjecting a cold-rolled stainless steel sheet containing Ag: 0.001 to 0.10 wt% to an annealing treatment in an oxidizing atmosphere and then to a descaling treatment. The descaling treatment contains Ag ions: 0.0001 to 1.0 mol / l, and nitric acid: 20 to 200 mol / l.
g / l in aqueous nitric acid or nitric acid: 20-200 g / l,
Hydrofluoric acid not forming a complex with metal ions: 5 to 100 g / l
As a descaling process of immersing the stainless steel cold-rolled steel sheet in an aqueous nitric hydrofluoric acid solution containing, after the descaling process, the stainless steel cold-rolled steel sheet is further immersed in a solution containing Ag ions: 0.0001 to 1.0 mol / l. A method for producing an antibacterial stainless steel sheet, characterized by performing an immersion treatment.

[0013] The present invention also provides a method for producing a stainless steel sheet comprising subjecting a cold-rolled stainless steel sheet containing Ag: 0.001 to 0.10 wt% to annealing treatment in an oxidizing atmosphere and then descaling treatment. A method for producing an antibacterial stainless steel sheet, characterized by further comprising immersing the cold-rolled stainless steel sheet in a solution containing Ag ions: 0.0001 to 1.0 mol / l after descaling.

Further, the present invention provides a method for producing a stainless steel sheet, comprising subjecting a cold-rolled stainless steel sheet containing 0.001 to 0.10 wt% of Ag to an annealing treatment in an oxidizing atmosphere and then to a descaling treatment. An antibacterial stainless steel characterized by subjecting the cold-rolled stainless steel sheet to a nitric acid aqueous solution containing Ag ions: 0.0001 to 1.0 mol / l and nitric acid: 10 to 200 g / l after the descaling treatment. This is a method for manufacturing a steel sheet.

Further, the present invention provides a method for producing a stainless steel sheet comprising subjecting a cold-rolled stainless steel sheet containing Ag: 0.001 to 0.10 wt% to an annealing treatment in an oxidizing atmosphere and then to a descaling treatment. After the descaling treatment, Ag ions: 0.0001 to 1.0 mol / l and sodium hydroxide:
A method for producing an antibacterial stainless steel sheet, comprising immersing the cold-rolled stainless steel sheet in an aqueous alkali solution containing 0.1 to 100 g / l.

The present invention also relates to a method for producing a stainless steel sheet comprising subjecting a cold-rolled stainless steel sheet containing 0.001 to 0.10 wt% of Ag to annealing treatment in an oxidizing atmosphere and then descaling treatment. For descaling treatment, Ag ion: 0.0001 to 1.0 mol / l, and nitric acid: 20 to 200 g / l
The stainless steel cold-rolled steel sheet is immersed in a nitric acid aqueous solution containing nitric acid: 20 to 200 g / l, nitric acid: 20 to 200 g / l, and hydrofluoric acid not forming a complex with metal ions: 5 to 100 g / l. A scale treatment, and after the descaling treatment, further subjected to immersion treatment in an aqueous nitric acid solution containing Ag ions: 0.0001 to 1.0 mol / l and nitric acid: 10 to 200 g / l. It is a manufacturing method. In the present invention,
Ag ion: 0.00 instead of the immersion treatment in the nitric acid aqueous solution
It may be immersed in an alkaline aqueous solution containing 01 to 1.0 mol / l and sodium hydroxide: 0.1 to 100 g / l.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION As the stainless steel sheet used in the present invention, any of ferritic stainless steel, austenitic stainless steel and martensitic stainless steel can be suitably used. The chemical composition of ferritic stainless steel is as follows: 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, S: 0.1 wt% or less,
It is preferable to contain Cr: 8 to 50 wt% and N: 0.1 wt% or less, with the balance being Fe and unavoidable impurities. In addition, Al: 0.3
wt% or less, Ni: 1.0 wt% or less, Mo: 5.0 wt% or less, Ti:
1.0 wt% or less, Nb: 1.0 wt% or less, Zr: 1.0 wt% or less, C
u: 1.0 wt% or less, W: 0.3 wt% or less, Co: 0.001 to 0.5
wt%, B: one or more of 0.01 wt% or less may be contained.

The chemical composition of the austenitic stainless steel is as follows: 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, S: 0.1 wt% or less, C
r: 10 to 35 wt%, Ni: 6 to 15 wt%, N: 0.001 to 0.1 wt
%, With the balance being Fe and unavoidable impurities. In addition, Al: 0.3 wt% or less, Mo: 3.0 wt% or less, T
i: 1.0 wt% or less, Nb: 1.0 wt% or less, Zr: 1.0 wt% or less, Cu: 1.0 wt% or less, W: 0.3 wt% or less, Co: 0.001
0.5 wt%, B: one or more of 0.01 wt% or less.

The chemical composition of martensitic stainless steel is as follows: 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, S: 0.1 wt% or less, C
r: 8 to 19 wt%, N: 0.001 to 0.1 wt%, the balance Fe
And it is preferable to use unavoidable impurities. In addition, Al:
1.5 wt% or less, Ni: 3.0 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: 0.3 wt% or less, Co: 0.001
0.5 wt%, B: one or more of 0.01 wt% or less.

The stainless steel sheet used in the present invention preferably has the chemical composition of various stainless steels in the above-described commonly known range, and further contains 0.001 to 0.10 wt% of Ag, or 0.001 to 0.30 wt% of V. , A cold-rolled stainless steel sheet subjected to cold rolling. In the present invention, first, the stainless steel plate itself needs to have antibacterial properties. For this reason, the steel sheet used in the present invention is a cold-rolled steel sheet containing a specific range of Ag.

The antibacterial agent in the present invention is a trace amount of Ag contained in a stainless steel plate. To express stable antibacterial properties, Ag is evenly distributed in the steel sheet,
In addition, it is important to control the existing form so as to elute at an appropriate rate. That is, the point is to control the Ag content and the form of existence for the expression of antibacterial properties, the addition of a special element for uniform distribution of Ag, and the control of manufacturing conditions.

Next, among the compositions of the cold-rolled stainless steel sheet used in the present invention, the reasons for limiting the contents of Ag and V will be described. Ag: 0.001 to 0.10 wt% Ag is the most important element in the present invention, and has an effect of suppressing the growth of bacteria and is an element that enhances antibacterial properties. These effects are observed when 0.001 wt% or more is added.
Addition of more than wt% has the effect of enhancing antibacterial properties,
Deterioration of corrosion resistance and surface defects during hot rolling increase, and a large amount of expensive Ag is added, resulting in high cost and disadvantageous economically. When the amount of Ag in the steel exceeds 0.10 wt%, the amount of Ag oxide in the surface layer increases. Oxides affect corrosion resistance, and when the amount of Ag oxide in the surface layer increases,
The passive film formed by the pickling does not exist stably, and the corrosion resistance deteriorates. For these reasons, the amount of Ag contained in the steel sheet is limited to the range of 0.001 to 0.10 wt%. In addition, more preferably, it is 0.01 to 0.05 wt%.

V: 0.001 to 0.30 wt% V is 0.001 to 0.30 wt% in addition to the above range of Ag.
%. V has the effect of remarkably improving the tendency of Ag compounds such as Ag particles, Ag oxides, and Ag sulfides to be unevenly distributed in the center of the sheet thickness, and uniformly dispersing Ag particles and Ag compounds in the steel sheet. Is an element effective for improving the antibacterial properties of steel sheets. By containing V in an amount of 0.001 wt% or more, uniform antibacterial properties of the steel surface can be achieved. On the other hand, if it exceeds 0.30 wt%, the workability of the steel sheet tends to decrease.
For this reason, V is preferably in the range of 0.001 to 0.30 wt%. More preferably, it is 0.001 to 0.10 wt%, and still more preferably, 0.010 to 0.025 wt%.

In the present invention, the cold-rolled stainless steel sheet having the above composition is subjected to an annealing treatment in an oxidizing atmosphere,
Then, descaling is performed. Conditions for the annealing treatment in an oxidizing atmosphere can be appropriately selected depending on the type of steel, and are not particularly limited in the present invention. In the annealing treatment, it suffices if the processing strain caused by the cold rolling can be softened and removed by recrystallization, or the solution dissolution of necessary elements can be achieved.

The annealed stainless steel cold-rolled steel sheet is then subjected to a descaling treatment to remove the scale formed during the annealing. Ag contained in cold rolled stainless steel sheet
Exists in the form of Ag particles, Ag oxides, Ag sulfides, etc., but after cold rolling, the surface layer of the annealed stainless steel sheet has an Ag-depleted layer in which Ag sublimates and disappears during annealing. And the antibacterial property tends to be reduced unless an appropriate surface treatment is performed in the descaling treatment following the annealing treatment.

Therefore, in the present invention, as an appropriate surface treatment, descaling treatment with a solution to which Ag ions are added or immersion treatment with a solution to which Ag ions are added after descaling treatment is performed. First, the case where the descaling treatment is immersion treatment in a solution to which Ag ions are added will be described.

The present inventors have found that when a steel sheet is immersed in an aqueous solution of nitric acid or nitric hydrofluoric acid to which Ag ions have been added, Ag is re-adhered to the surface, exhibiting excellent antibacterial properties, and the scale of the steel sheet surface is rapidly reduced. And found that it could be removed. For this reason, in the present invention, as one of appropriate surface treatments,
For the descaling treatment, an immersion treatment in a nitric acid or nitric hydrofluoric acid aqueous solution to which Ag ions were added was applied.

In an aqueous nitric acid solution or an aqueous nitric hydrofluoric acid solution to which Ag ions are added, the dissolution reaction of Ag is represented by the following formula. If the Ag ion concentration in the Ag → Ag ⁺ + e ⁻ solution is equal to or higher than a certain concentration, the reaction does not proceed rightward due to the equilibrium relationship, but rather proceeds leftward, and the Ag is attached to the steel sheet surface. . Further, the present inventors have found that if the Ag ion concentration in the solution is within a specific range, there is no fear that the dissolution reaction (descaling reaction) between nitric acid and hydrofluoric acid and the base iron and the oxide film will be inhibited. confirmed.
In the present invention, the concentration of Ag ions contained in the aqueous nitric acid solution or the aqueous nitric hydrofluoric acid solution is 0.0001 to 1.0 mol / l.

By adjusting the concentration of Ag ions in the aqueous nitric acid solution or the aqueous nitric hydrofluoric acid solution to 0.0001 mol / l or more, Ag adheres to the steel sheet surface even during the descaling process during dissolution of scale and ground iron, and The antibacterial property of the steel sheet surface after the scale treatment can be sufficiently improved. On the other hand, if the concentration of Ag ions in the aqueous nitric acid solution or the aqueous nitric hydrofluoric acid solution exceeds 1.0 mol / l, the scale will inhibit the reaction of the iron base with nitric acid and hydrofluoric acid (descaling reaction), and the remaining scale will be lost. Will occur. Therefore, Ag in nitric acid aqueous solution or nitric hydrofluoric acid aqueous solution
The concentration of ions was limited to the range of 0.0001 to 1.0 mol / l.

Before the descaling treatment, a preliminary descaling treatment such as a molten salt immersion method or a neutral salt electrolysis method may be performed. In the descaling process by immersion in a solution containing Ag ions, the nitric acid aqueous solution used is a solution containing 20 to 200 g / l of nitric acid. The nitric hydrofluoric acid aqueous solution used is nitric acid 20
~ 200g / l, hydrofluoric acid not forming complex with metal 5 ~ 100g / l
A solution containing By setting the concentration of the nitric acid aqueous solution or the nitric hydrofluoric acid aqueous solution as described above, only the base iron is selectively dissolved, the dispersion of Ag on the steel sheet surface becomes remarkable, and the antibacterial property is remarkably improved. If the nitric acid concentration in the nitric acid aqueous solution or nitric hydrofluoric acid aqueous solution is less than 20 g / l, the dissolution of the base iron does not proceed, and a large amount of time is required for descaling. Further, generation of the NO _X when the nitric acid concentration of nitric acid aqueous solution or nitric-hydrofluoric aqueous acid solution is more than 200 g / l becomes significant, to inhibit surface adhesion of Ag.

If the concentration of hydrofluoric acid that does not form a complex with the metal is less than 5 g / l, the dissolution of the base iron does not proceed, and a large amount of time may be required for descaling. The effect is particularly remarkable in the case of austenitic stainless steel. on the other hand,
If the concentration of hydrofluoric acid that does not form a complex with metal exceeds 100 g / l, the reaction with the ferrous iron becomes violent, which inhibits the adhesion of Ag surface and also the surface of the steel sheet becomes rough, impairing corrosion resistance and abrasiveness. I do.

Therefore, in the descaling treatment by immersion in a solution containing Ag ions, the nitric acid concentration of the aqueous nitric acid solution used is 20 to 200 g / l, and the nitric acid concentration of the aqueous nitric hydrofluoric acid solution is 20 to 200 g / l.
200 g / l and the concentration of hydrofluoric acid should be 5-100 g / l. From the viewpoint of descaling speed, more preferably, the concentration of the nitric acid aqueous solution is 50 to 150 g / l, and the concentration of the nitric hydrofluoric acid aqueous solution is nitric acid.
50-150 g / l, hydrofluoric acid 15-50 g / l. The preferred temperature of the aqueous nitric acid or nitric hydrofluoric acid solution is 40 to 60 ° C. Outside of this temperature range, there is a disadvantage that the descaling speed becomes slow.

Before the descaling treatment, a preliminary descaling treatment such as a molten salt immersion method or a neutral salt electrolysis method may be performed. Further, in the present invention, the descaling treatment by dipping in a nitric acid aqueous solution or a nitric hydrofluoric acid aqueous solution containing Ag ions may be performed, and a generally known descaling treatment not containing Ag ions may be performed. In this case, after the descaling treatment, further immersion treatment in a neutral solution containing 0.0001 to 1.0 mol / l of Ag ions, or 0.0001 to 1.0 mol / l of Ag ions:
And nitric acid: immersion treatment in an aqueous nitric acid solution containing 10 to 200 g / l,
Alternatively, it is preferable to perform immersion treatment in an aqueous alkali solution containing Ag ions: 0.0001 to 1.0 mol / l and sodium hydroxide: 0.1 to 100 g / l. After generally known descaling treatment,
A steel sheet is immersed in a neutral solution containing Ag ions: 0.0001 to 1.0 mol / l, in an aqueous nitric acid solution containing Ag ions: 0.0001 to 1.0 mol / l, or in an alkaline aqueous solution containing Ag ions: 0.0001 to 1.0 mol / l. By doing so, the antibacterial properties of the steel sheet can be recovered and improved to the same level as or higher than that of the base material.

The ordinary descaling treatment using a solution containing no Ag ions alone causes the Ag formed by sublimation of Ag during annealing.
A deficient layer is present on the surface of the steel sheet and does not exhibit antibacterial properties comparable to those of the base metal. Here, the commonly known descaling treatment with a solution containing no Ag is performed by immersion pickling in a nitric acid aqueous solution, electrolytic pickling in a nitric acid aqueous solution, or pickling using them together. preferable. The concentration of the nitric hydrofluoric acid aqueous solution used for immersion pickling was as follows: nitric acid: 20 to 200 g / l, hydrofluoric acid: 5 to
It is preferable that the concentration of the aqueous solution of nitric acid is 100 g / l and the concentration of the aqueous solution of nitric acid is 20 to 200 g / l. 5-30C / dm
Preferably it is ² . It is needless to say that a preliminary descaling treatment such as a molten salt immersion method and a neutral salt electrolysis method may be performed before the generally known descaling treatment.

After performing a generally known descaling treatment,
Steel Ag ions: When immersed in a neutral solution or an aqueous nitric acid solution containing 0.0001~1.0mol / l, Ag ← Ag + + e - reaction proceeds in, Ag is deposited adhering to the surface of the steel sheet in a very short time. Thereby, the antibacterial property can be restored to the same level as that of the base material without impairing the gloss and corrosion resistance of the surface.

The neutral solution or nitric acid aqueous solution used
When the concentration of Ag ions is 0.0001 mol / l or more, Ag adheres to the surface of the steel sheet, and the antibacterial property of the steel sheet surface after the descaling treatment can be sufficiently recovered. On the other hand, Ag
When the ion concentration exceeds 1.0 mol / l, the passivation of the surface layer is hindered, and the corrosion resistance is deteriorated. For this reason, the concentration of Ag ions in the neutral solution or nitric acid aqueous solution used is 0.0001.
The range was limited to ~ 1.0 mol / l. Preferably, the concentration of Ag ions in the neutral solution or aqueous nitric acid solution used is
It is 0.001 to 0.2 mol / l.

The nitric acid concentration in the aqueous nitric acid solution used for restoring the antibacterial property is preferably in the range of 10 to 200 g / l. If the concentration of nitric acid in the aqueous nitric acid solution is less than 10 g / l, the conductivity of the solution is low, and it becomes difficult for Ag to adhere to the steel sheet surface in a short time. On the other hand, the nitric acid concentration in the nitric acid aqueous solution was 200 g / l
If it exceeds 300, the generation of NO _X becomes remarkable, and the passivation film becomes too strong, so that Ag is prevented from adhering to the steel sheet surface. In addition, more preferably, the nitric acid concentration in the aqueous nitric acid solution is 50 to 150 g / l.

When the steel sheet is immersed in an alkaline aqueous solution containing 0.0001 to 1.0 mol / l of Ag ions after the generally known descaling treatment, Ag ₂ O precipitates on the steel sheet surface in addition to Ag alone, The antibacterial property can be improved in a short time without impairing gloss and corrosion resistance. In addition, the solubility of Ag ₂ O in water is very high, and shows much better antibacterial properties than Ag alone.

By setting the concentration of Ag ions in the aqueous alkaline solution to be 0.0001 mol / l or more, the
Ag adheres, and the antibacterial property of the steel sheet surface after the descaling treatment can be sufficiently recovered. On the other hand, if the concentration of Ag ions exceeds 1.0 mol / l, passivation of the surface layer is prevented, and Ag ₂ O adheres excessively to the surface more than necessary, deteriorating the corrosion resistance. For this reason, the concentration of Ag ions in the alkaline aqueous solution was limited to the range of 0.0001 to 1.0 mol / l. Preferably, the concentration of Ag ions in the aqueous alkaline solution is 0.001 to 0.1.
mol / l.

The alkaline aqueous solution used for restoring the antibacterial property is preferably an alkaline aqueous solution containing 0.1 to 100 g / l of sodium hydroxide. Note that potassium hydroxide, calcium hydroxide, ammonia, or the like may be used instead of sodium hydroxide. When the concentration of sodium hydroxide in the alkaline aqueous solution is less than 0.1 g / l, the pH of the solution is low, and the relationship between the reaction potential and the pH makes it difficult for Ag ₂ O to precipitate and adhere to the steel sheet surface in a short time, Less antibacterial recovery. On the other hand, if it exceeds 100 g / l, the pH of the solution becomes too high, and a stable precipitation area for other substances is formed, and the precipitation and adhesion of Ag ₂ O is reduced, and the recovery of antibacterial properties is reduced. More preferably, the concentration of sodium hydroxide in the alkaline aqueous solution is 1.0 to 50 g / l.

The Ag ion to be added to the solution in the present invention may be in any form without any problem. It is not necessary to limit the present invention, but AgNO ₃ , Ag ₂ O, etc., which do not react with the solution, are preferred. Further, in the present invention, after performing the descaling treatment of immersing in the aqueous nitric acid solution or the aqueous solution of nitric hydrofluoric acid containing the Ag ions described above, and further combining the immersion treatment of immersing in the solution containing the Ag ions described above. By applying, the antibacterial property is further improved.

For the cold-rolled stainless steel sheet of the present invention, any of the commonly known melting methods can be applied, and the melting method does not need to be particularly limited. Stainless steel molten steel containing 0.001 to 0.10 wt% of Ag, or 0.001 to 0.30 wt% of V is usually produced by a known melting method. The molten steel produced can be made into a steel material by a generally known casting method, but it is preferable to apply a continuous casting method from the viewpoint of productivity and quality.

In the continuous casting method, Ag or Ag
In order to distribute the compound evenly, the casting speed should be 0.8 ~
It is desirable to be in the range of 1.6 m / min. The casting speed is 0.
At less than 8 m / min, the Ag compound becomes coarse and the corrosion resistance deteriorates. On the other hand, when the casting speed exceeds 1.6 m / min, stable casting is difficult and the distribution of Ag compounds becomes uneven.
Therefore, the casting speed in the continuous casting method is set to 0.8 to 1.6.
It is preferably in the range of m / min.

In the present invention, the stainless steel molten steel having the above-mentioned chemical composition is preferably cast continuously under the above-mentioned conditions to obtain a steel material, and if necessary, the steel material is heated to a predetermined temperature. Then, a desired hot-rolled sheet (hot-rolled steel sheet) is formed by hot rolling. Hot rolled sheet is preferably used if necessary
After being annealed at a temperature of 700 to 1200 ° C., further subjected to pickling, and then subjected to cold rolling, a cold-rolled sheet (cold-rolled steel sheet) having a predetermined thickness is obtained.

In the present invention, the surface layer can be converted to the Ag form even if the skin pass rolling such as skin pass rolling (SK rolling) is performed after the usual descaling treatment or before immersion in a solution containing Ag ions. There is no problem because it does not make any changes.

[0046]

EXAMPLES (Example 1) A stainless steel having the chemical composition shown in Table 1 was melted and made into a slab by a continuous casting method at a casting speed of 1.2 m / min. These slabs were heated to form a hot-rolled sheet having a thickness of 4.0 mm by hot rolling. Next, these hot-rolled sheets were annealed at 700 to 1200 ° C., pickled, and then cold-rolled into cold-rolled sheets having a thickness of 0.8 mm.

These cold rolled sheets were subjected to a finish annealing treatment in a C gas combustion atmosphere (oxygen 3%, carbon dioxide 7%, steam 20%, balance nitrogen). The annealing temperature of the cold rolled sheet was 800 to 1050 ° C for ferritic stainless steel, 1000 to 1200 ° C for austenitic stainless steel, and 780 to 850 ° C for martensitic stainless steel. Next, these cold-rolled sheets were neutralized with a neutral salt (20% Na ₂ SO ₄ ,
After performing an electrolytic treatment (electricity: 40 C / dm ² ) at 80 ° C.), these cold-rolled sheets were immersed in a nitric acid aqueous solution or a nitric hydrofluoric acid aqueous solution containing Ag ions having a concentration shown in Table 2. And descaling treatment. After the descaling treatment, the state of descaling was observed by visual inspection.

An antibacterial test and a corrosion resistance test were performed on these stainless steel plates. Further, in order to confirm the durability and durability of the antibacterial property, the surface was rubbed lightly and reciprocally five times with # 400 abrasive paper, and then an antibacterial test was carried out. The outline of the test method of each test is described below. (1) Antibacterial property test The antibacterial property was evaluated based on the film adhesion method of the Antibacterial Product Technology Council.

The test specimen (50 mm × 50 mm) is washed and degreased with absorbent cotton containing 99.5% ethanol. E. coli is dispersed in a 1/500 NB solution. (The number of bacteria is
It was adjusted to 2.5 × 10 ⁵ cfu / sheet. The 1/500 NB solution is a solution obtained by diluting a normal Bion medium (NB) 500 times with sterilized purified water. Ordinary Bion medium (NB) is meat extract 5.0g, sodium chloride 5.0g, peptone 10.0g, purified water
1.000ml, pH: 7.0 ± 0.2 Inoculate the test solution (3 each) with the bacterial solution at a rate of 0.4 ml / 25 cm ² .

A polyethylene film is put on the surface of the test piece. Store at a temperature of 35 ° C ± 1.0 ° C and RH 90% or more for 24 hours. (RH: relative temperature) The number of viable cells is measured by an agar plate method (35 ± 1.0 ° C., 48 hours). The antibacterial activity was evaluated by a sterilization rate defined by the following equation.

Bactericidal rate (%) = (number of bacteria of control−number of bacteria after test) / (number of bacteria of control) × 100 The number of bacteria of the control is the number of bacteria after the antibacterial test of the stainless steel sheet not subjected to the antibacterial treatment. It refers to the viable count. The number of bacteria after the test is the number of viable bacteria measured. (2) Corrosion resistance test The corrosion resistance was evaluated by a salt-dry / wet combined cycle test.

A test piece was sprayed with a 5.0% aqueous NaCl solution (temperature: 35 ° C.) for 0.5 hour for 0.5 hour, and then dried in a dry atmosphere at a humidity of 40% or less and a temperature of 60 ° C.
Hold for hours. Humidity: 95% or more, temperature: Keep in a humid atmosphere of 40 ° C for 1.0 hour. After a plurality of cycles (5 to 30 cycles) set for each steel type were repeated as one cycle, the rusting area ratio (%) of the test piece surface was measured.

Table 2 shows the results.

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

[Table 3]

[0057]

[Table 4]

The examples of the present invention show excellent antibacterial properties both as a product and after a corrosion resistance test. It also maintains excellent antibacterial properties even after rubbing lightly and reciprocally five times with # 400 abrasive paper. Further, the examples of the present invention have a low rusting area ratio and are excellent in corrosion resistance. The above results can be confirmed regardless of the type of stainless steel. On the other hand, the comparative examples out of the range of the present invention have deteriorated antibacterial properties and / or corrosion resistance.

The antibacterial property was judged to be acceptable if the sterilization rate was 99.0% or more. As for corrosion resistance, a sterilization rate of 99.0% or more was satisfied, and a rusting area rate of 15% or less was judged as acceptable. (Example 2) A stainless steel having a chemical composition shown in Table 3 was melted and formed into a slab by a continuous casting method at a casting speed of 1.2 m / min. These slabs were heated to form a hot-rolled sheet having a thickness of 4.0 mm by hot rolling. Next, these hot-rolled sheets were annealed at 700 to 1200 ° C., pickled, and then cold-rolled into cold-rolled sheets having a thickness of 0.8 mm.

These cold-rolled sheets were subjected to a finish annealing treatment in a C gas combustion atmosphere (oxygen 3%, carbon dioxide 7%, steam 20%, balance nitrogen). The annealing temperature of the cold rolled sheet was 800 to 1050 ° C for ferritic stainless steel and 780 to 850 ° C for martensitic stainless steel. Next, these cold-rolled sheets were subjected to an electrolytic treatment (electricity: 40 C / dm ² ) in a neutral salt (20% Na ₂ SO ₄ , 80 ° C.), and then, under the conditions shown in Table 4, a commonly known method was used. A descaling treatment was performed by electrolysis in a nitric acid aqueous solution. Then, under the conditions shown in Table 4, in a neutral solution containing Ag ions, in an aqueous nitric acid solution containing Ag ions, or
The immersion treatment was performed in an aqueous solution of sodium hydroxide containing Ag ions.

For these stainless steel sheets, an antibacterial test and a corrosion resistance test were carried out in the same manner as in Example 1.
As in Example 1, in order to confirm the durability and durability of the antibacterial property, the surface was rubbed lightly and reciprocally five times with # 400 abrasive paper, and then an antibacterial test was carried out. Table 4 shows the results.

[0062]

[Table 5]

[0063]

[Table 6]

[0064]

[Table 7]

As in Example 1, the present invention shows excellent antibacterial properties both as a product and after rubbing lightly and reciprocally five times with # 400 abrasive paper. Further, the examples of the present invention have a low rusting area ratio and are excellent in corrosion resistance. The above results can be confirmed regardless of the type of stainless steel. On the other hand, the comparative examples outside the scope of the present invention have deteriorated antibacterial properties or deteriorated corrosion resistance. (Example 3) Stainless steel having the chemical composition shown in Table 5 was melted and made into a slab by a continuous casting method at a casting speed of 1.2 m / min. These slabs were heated to form a hot-rolled sheet having a thickness of 4.0 mm by hot rolling. Next, these hot-rolled sheets were annealed at 700 to 1200 ° C., pickled, and then cold-rolled into cold-rolled sheets having a thickness of 0.8 mm.

These cold rolled sheets were subjected to a finish annealing treatment in a C gas combustion atmosphere (oxygen 3%, carbon dioxide 7%, steam 20%, balance nitrogen). The annealing temperature of the cold-rolled sheet was 800 to 1050 ° C for ferritic stainless steel, 1000 to 1200 ° C for austenitic stainless steel, and 780 to 850 ° C for martensitic stainless steel. Next, these cold-rolled sheets were subjected to an electrolytic treatment (electric quantity: 40 C / dm ² ) in a neutral salt (20% Na ₂ SO ₄ , 80 ° C.), and then Ag ions were added under the conditions shown in Table 6. A descaling treatment was performed by dipping in a nitric acid aqueous solution or a nitric hydrofluoric acid aqueous solution. Then, under the conditions shown in Table 6,
The immersion treatment was performed in a neutral solution containing Ag ions, an aqueous nitric acid solution containing Ag ions, or an aqueous sodium hydroxide solution containing Ag ions.

For these stainless steel sheets, an antibacterial test and a corrosion resistance test were performed in the same manner as in Example 1.
As in Example 1, in order to confirm the durability and durability of the antibacterial property, the surface was rubbed lightly and reciprocally five times with # 400 abrasive paper, and then an antibacterial test was carried out. Table 6 shows the results.

[0068]

[Table 8]

[0069]

[Table 9]

[0070]

[Table 10]

As in Examples 1 and 2, the inventive examples show excellent antibacterial properties both as a product and after lightly reciprocating five times with # 400 abrasive paper. Further, the examples of the present invention have a low rusting area ratio and are excellent in corrosion resistance. The above results can be confirmed regardless of the type of stainless steel. On the other hand, the comparative examples outside the scope of the present invention have deteriorated antibacterial properties or deteriorated corrosion resistance.

[0072]

According to the present invention, it is possible to provide a ferritic, austenitic, or martensitic stainless steel material having excellent antibacterial properties and corrosion resistance and any surface finish. It works.
In addition, molding and polishing are performed, and materials with an emphasis on hygiene, such as stainless steel materials with excellent antibacterial properties and corrosion resistance applied to uses where bacteria easily proliferate in humid environments such as kitchens and bathtubs. There is also an effect that it can be easily manufactured.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Susumu Sato 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Co., Ltd. (72) Masayuki Ota 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Yoshihiro Satake (72) Inventor Yoshihiro Satake 1st Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba F-term in Kawasaki Steel Corporation Chiba Works (reference) AB02 AB03 AB04 BA08 BB02 BC00 CA02 CA04 CA15

Claims (4)

[Claims] 1. A method for producing a stainless steel sheet, comprising subjecting a cold-rolled stainless steel sheet containing 0.001 to 0.10 wt% of Ag to annealing treatment in an oxidizing atmosphere and then descaling the stainless steel sheet. , Ag ion: 0.0001-1.
Nitric acid aqueous solution containing 0 mol / l and nitric acid: 20-200 g / l, or nitric acid: 20-200 g / l, hydrofluoric acid not forming a complex with metal ions: 5-100 g / l A method for producing an antibacterial stainless steel sheet, which is a descaling treatment in which the stainless steel cold-rolled steel sheet is immersed in an acid aqueous solution. 2. After the descaling treatment, Ag ions: 0.
The method for producing an antibacterial stainless steel sheet according to claim 1, wherein an immersion treatment of immersing the cold-rolled stainless steel sheet in a solution containing 0001 to 1.0 mol / l is performed. 3. A method for producing a stainless steel sheet comprising subjecting a cold-rolled stainless steel sheet containing Ag: 0.001 to 0.10 wt% to an annealing treatment in an oxidizing atmosphere and then to a descaling treatment. , And Ag ions: 0.
A method for producing an antibacterial stainless steel sheet, comprising immersing the cold-rolled stainless steel sheet in a solution containing 0001 to 1.0 mol / l. 4. A solution containing the Ag ions: 0.0001 to 1.0 mol / l, the solution containing Ag ions: 0.0001 to 1.0 mol / l and nitric acid: 10 to 200 g.
nitric acid aqueous solution containing / l or Ag ion: 0.0001-1.0m
The method for producing an antibacterial stainless steel sheet according to claim 2 or 3, wherein the aqueous solution is an alkaline aqueous solution containing ol / l and sodium hydroxide: 0.1 to 100 g / l.