JP3201750B2 - Manufacturing method of stainless steel with excellent antibacterial properties - 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 No. 2 finished stainless steel material which has excellent antibacterial properties and is suitable for use in daily necessities, medical equipment and building materials. The stainless steel material in the present invention is a steel plate, a steel strip,
It shall include steel pipes, steel wires and stainless steel products.

[0002]

2. Description of the Related Art Silver and copper have long been known to 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, Japanese Patent Application Laid-Open No. 8-49085 discloses an antibacterial property in which a metal layer or an alloy layer of Cr, Ti, Ni, Fe or the like containing Ag and / or Cu is formed on the surface of a stainless steel substrate by magnet sputtering. An excellent stainless steel sheet 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 process by pickling. In the case of a No. 2 finish stainless steel material, an oxidizing atmosphere is required after cold rolling. After being annealed in the interior, it is pickled and made into 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) disappears from the surface layer during annealing, and a region having a low antibacterial element concentration may be formed on the surface layer, and sufficient antibacterial properties can be obtained even after pickling after annealing. There was a problem that it could not be obtained.

[0009] The present invention advantageously solves the prior art problems described above, with enhanced relatively small Ag content, yet antimicrobial final product surface layer portion, the production of antibacterial and excellent corrosion resistance stainless steel material The aim is to provide a method.

[0010]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve both antibacterial properties and corrosion resistance in stainless steel materials. As a result, a small amount of Ag was added to the stainless steel cold-rolled steel material, and an appropriate amount of Ag particles remained on the surface of the stainless steel material after the annealing and pickling treatment. It has been found that the antibacterial properties of steel can be significantly improved.

Further, the present inventors have proposed that the finish pickling be pickling in a nitric acid aqueous solution in a specific concentration range in order to leave an appropriate amount of Ag particles on the surface of the stainless steel material after the pickling treatment. Preferably, it has been found that it is important to keep the dissolution potential of the stainless steel material in the aqueous nitric hydrofluoric acid solution at a predetermined value or less. The present invention has been completed based on the above findings.

That is, according to the present invention , Ag : 0.0010 to 0.10 wt.
% Of a cold-rolled stainless steel material containing 1% by weight , the annealing process and the pickling process are sequentially performed.
0 g / l and 5-100 g / l hydrofluoric acid in an aqueous nitric hydrofluoric acid solution.
The melting potential of the stainless steel cold rolled steel is -50 mV or less with respect to the AgCl electrode.
Adjusted down, and the cold-rolled stainless steel surface dissolving 0.1 [mu] m or more in depth, No. 2 finish stainless steel with excellent antibacterial, characterized in that the pickling in nitric-hydrofluoric acid solution It is a manufacturing method of.

[0013] Also, in the present invention, following the pickling in the nitric-hydrofluoric acid solution, in 1 to 15 wt% nitric acid aqueous solution, at least once, the potential of the cold-rolled stainless steel to AgCl electrode -100 Nitric acid electrolytic pickling may be performed to maintain the voltage at mV or less.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The No. 2 finished stainless steel of the present invention is No. 2 of ferritic stainless steel, austenitic stainless steel and martensitic stainless steel.
Finished products are all suitable. The chemical composition of ferritic stainless steel is as follows: C: 0.0001-0.1 wt%, Si: 1.0 wt%
%, Mn: 2.0 wt% or less, P: 0.1 wt% or less, S: 0.
It is preferable to contain 1 wt% or less, 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, Cu: 1.0 wt% or less, W: 0.3 wt% or less, Co: 0.001 to 0.5 wt%, B: 0.01 wt% or less.

The chemical composition of 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: 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: 0.01 wt% or less.

The steel material of the present invention, which has been subjected to an annealing treatment and a pickling treatment successively after cold rolling, preferably has the chemical components in the above-mentioned ranges, and further contains 0.0010 to 0.10 wt% of Ag. Alternatively, it is a stainless steel material containing V: 0.001 to 0.30 wt%, and a No. 2 finish stainless steel material in which Ag particles are dispersed in an area ratio of 0.0002% or more on the surface of the stainless steel material.

First, the reasons for limiting the contents of Ag and V in the composition of the stainless steel material of the present invention will be described. In addition,
In the present invention, the components other than Ag and V are preferably in the range of the various types of commonly known stainless steels described above. Ag: 0.001 to 0.10 wt% The antibacterial agent in the present invention is a trace amount of Ag contained in the stainless steel material. In order to express stable antibacterial properties, in the present invention, Ag is uniformly distributed in the steel material,
In addition, the presence form is controlled 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.

Ag is the most important element in the present invention, and has the effect of suppressing the growth of bacteria and enhances the antibacterial properties. These effects are observed when added at 0.001 wt% or more, but when added over 0.10 wt%, they have the effect of increasing antibacterial properties. However, corrosion resistance is degraded, surface defects during hot rolling are increased, and the cost is increased. Since a large amount of Ag is added in a large amount, the cost is increased, which is economically disadvantageous. For these reasons, the amount of Ag contained in steel 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 Ag in the above range.
%. 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 plate thickness, and uniformly dispersing Ag particles and Ag compounds in steel. Is an element effective for improving the antibacterial property of steel. 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 added in excess of 0.30 wt%, the workability of the steel material tends to decrease.
For this reason, V is preferably in the range of 0.001 to 0.30 wt%. It is more preferably 0.001 to 0.10%, and still more preferably 0.010 to 0.025 wt%.

The stainless steel material of the present invention is a steel material having the above-described composition, which has been subjected to cold rolling, annealing treatment, and pickling treatment in that order.
% Or more. Ag contained in the stainless steel material exists in the form of Ag particles, Ag oxide, Ag sulfide, etc., but after cold rolling, the surface layer of the annealed stainless steel material is annealed. More preferably, there is an Ag-deficient layer in which Ag has disappeared, and the antibacterial property tends to be reduced unless an appropriate surface layer is dissolved and removed by the pickling treatment following the annealing treatment. Therefore, in the present invention, by appropriately dissolving and removing the surface layer, Ag particles are dispersed in an area ratio of 0.0002% or more on the surface of the stainless steel material after the annealing and pickling treatment. Thereby, a minimum antibacterial property can be secured.

Ag particles on the surface of the stainless steel material have an area ratio of 0.
If it is less than 0002%, the antibacterial properties deteriorate. Even if the amount of Ag particles on the surface of the steel material is large, the Ag particles themselves do not adversely affect the corrosion resistance.However, if the amount of Ag particles is large, the Ag particles may come off the surface in the polishing process or the like, causing surface flaws. Is also conceivable. Therefore, the area ratio of the Ag particles is preferably set to 0.05% or less.

From the above, the annealing of the present invention
Ag particles dispersed on the surface of the stainless steel material after pickling,
The area ratio is 0.0002% or more, preferably 0.05% or less.
More preferably, the area ratio is 0.001 to 0.03%. More preferably, the area ratio is 0.001 to 0.02%. It is preferable that the amount of Ag particles on the surface of the stainless steel material is measured by a field emission Auger electron spectrometer or an electron beam microanalyzer.

Next, a method for producing the steel material of the present invention will be described. In the present invention, Ag: 0.0010 to 0.10 wt%,
Alternatively, a cold-rolled stainless steel material containing V: 0.001 to 0.30 wt% is subjected to annealing treatment and pickling treatment. The conditions of the annealing treatment 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 solid solution of the necessary element can be further achieved.

The annealed cold rolled stainless steel is then subjected to an acid pickling treatment to remove the scale formed during the annealing treatment. It is needless to say that a preliminary descaling treatment may be performed by a salt bath method, a neutral salt electrolysis method or the like before the pickling treatment. In the present invention, the finishing pickling in the pickling treatment is pickling in an aqueous nitric hydrofluoric acid solution.

By pickling in a nitric hydrofluoric acid aqueous solution, the surface of the cold-rolled stainless steel is dissolved by 0.1 μm or more in the depth direction.
Thereby, the Ag deficiency layer of the surface layer generated by the annealing treatment can be removed, and the antibacterial property of the surface layer can be secured. If the amount of dissolution is less than 0.10 μm in the depth direction, the removal of the Ag-deficient layer on the surface layer is insufficient, and the antibacterial property of the surface layer decreases. Also, pickling in a nitric hydrofluoric acid aqueous solution, the dissolution potential of stainless steel cold rolled steel material, Ag
It is preferable to adjust the voltage to −50 mV or less with respect to the Cl electrode and perform pickling. By setting the melting potential of the stainless steel cold-rolled steel material to −50 mV or less with respect to the AgCl electrode, Ag contained in the steel material is more stable when present as Ag particles than ionized,
It disperses and remains on the steel surface as the pickling time elapses. On the other hand, in this range of potential, the cold rolled stainless steel
It dissolves relatively easily with the passage of the pickling time.

On the other hand, if the dissolution potential of the cold-rolled stainless steel is set to a potential exceeding −50 mV with respect to the AgCl electrode, the acid is selectively dissolved, and the antibacterial property of the surface layer is deteriorated.
For this reason, in the present invention, in a nitric hydrofluoric acid aqueous solution, the dissolution potential of the stainless steel cold-rolled steel material is adjusted to −50 mV or less with respect to the AgCl electrode, and the pickling is performed so that the dissolution potential is 0.1 μm or more in the depth direction. Is preferred. In addition, from the viewpoint of descaling speed, it is more preferably -100 mV or less.

In the present invention, the nitric hydrofluoric acid aqueous solution used for the finish pickling is preferably an aqueous nitric hydrofluoric acid solution containing 20 to 200 g / l of nitric acid and 5 to 100 g / l of hydrofluoric acid. By making the concentration of the nitric hydrofluoric acid aqueous solution as described above, the potential for reaction is lowered, only the base iron is selectively dissolved, the dispersion dispersion of Ag on the steel material surface becomes remarkable, and the antibacterial property is remarkably improved. I do. If the nitric acid concentration in the aqueous nitric hydrofluoric acid solution is less than 20 g / l, pickling (dissolution of the base iron) does not proceed, and the surface residue of Ag is small. Further, when the nitric acid concentration in the nitric hydrofluoric acid aqueous solution exceeds 100 g / l, generation of NO _X becomes remarkable. In addition, when the potential for reaction increases, Ag re-elution occurs, which inhibits Ag from remaining on the surface, and is not preferable from an environmental point of view.

If the concentration of hydrofluoric acid is less than 5 g / l, pickling (dissolution of ground iron) does not proceed, an Ag-deficient region remains, and antibacterial properties cannot be ensured. On the other hand, when the hydrofluoric acid concentration exceeds 100 g / l,
The surface of the steel material becomes rough and impairs corrosion resistance and abrasiveness. Therefore, the nitric acid concentration of the nitric hydrofluoric acid aqueous solution used for finish pickling is
Preferably, the concentration is 20 to 200 g / l and the concentration of hydrofluoric acid is 5 to 100 g / l. From the viewpoint of descaling speed, more preferably, the concentration of the aqueous nitric hydrofluoric acid solution is 50 to 130 g / l of nitric acid and 20 to 130 g of hydrofluoric acid.
It is 50 g / l. The preferred temperature of the nitric hydrofluoric acid aqueous solution is
40-70 ° C. If the temperature is lower than 40 ° C., a large amount of time is required for descaling. If the temperature exceeds 70 ° C., there is a problem that the generation of NOx becomes severe.

In the present invention, electrolytic pickling of nitric acid under the following conditions may be performed following the pickling in the above-mentioned nitric hydrofluoric acid aqueous solution. In the present invention, the nitric acid electrolytic pickling is performed at 1 to 15 wt%.
In a nitric acid aqueous solution, the potential of the cold-rolled stainless steel is maintained at least once at -100 mV or less with respect to the AgCl electrode. Usually, Ag dissolves when immersed in an aqueous nitric acid solution, but by holding the potential of the cold-rolled stainless steel at least once at -100 mV or less with respect to the AgCl electrode, Ag enters the stable region and hardly dissolves . Conversely, holding at a potential higher than -100 mV causes selective dissolution of Ag. on the other hand,
By the potential of this range, the surface layer of impurities other than Ag _{(e.g., Ti0 2, SiO 2, MnO} , Cr 2 O 3 , etc.) is selectively dissolved. Therefore, Ag which is not a compound on the surface layer
The area ratio of the particles increases. In addition, from the viewpoint of the reaction rate,
The potential of cold rolled stainless steel is -150m with respect to the AgCl electrode.
V or less is more preferable.

The nitric acid concentration in the aqueous nitric acid solution is 1 wt%.
The above effects in is insufficient, also, generation of the NO _X when the nitric acid concentration in the nitric-hydrofluoric acid aqueous solution exceeds 15 wt% is remarkable less than. For this reason, it is preferable to use an aqueous solution of 1 to 15% by weight of nitric acid for nitric acid electrolytic pickling. The nitric acid concentration is more preferably 5.0 to 12.0 wt%. The stainless steel material of the present invention can be smelted by applying all commonly known smelting methods,
The smelting method does not need to be particularly limited.

The molten stainless 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 smelted molten steel can be made into a steel material by a generally known casting method, but the productivity,
It is preferable to apply the continuous casting method from the viewpoint of quality.
In the continuous casting method, the casting speed is desirably in the range of 0.8 to 1.6 m / min in order to uniformly distribute Ag or an Ag compound in the steel. If the casting speed is less than 0.8 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. For this reason, the casting speed in the continuous casting method is preferably in the range of 0.8 to 1.6 m / min.

Further, in the present invention, the molten stainless steel having the above-mentioned chemical composition is preferably continuously cast into a steel material under the above-mentioned conditions, and then, if necessary, the steel material is heated to a predetermined temperature. Then, a desired hot rolled sheet (steel strip or steel sheet after hot rolling) is formed by hot rolling. The hot rolled sheet is optionally annealed, preferably at a temperature of 700-1200 ° C,
Further, after being subjected to pickling, cold rolling is performed to obtain a cold rolled sheet (steel strip or steel sheet after cold rolling) having a predetermined thickness.

The cold rolled sheet is then subjected to annealing and pickling as described above. In the steel material of the present invention, there is no problem even if temper rolling is performed after pickling.

[0035]

EXAMPLES (Example 1) Stainless steel having the chemical composition shown in Table 1 was melted and made into a slab by a continuous casting method.
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 to a thickness of 0.8 mm.
Cold rolled sheet.

These cold rolled sheets were annealed in a C gas combustion atmosphere (3% oxygen, 7% carbon dioxide, 20% steam, balance nitrogen). The annealing temperature of the cold rolled sheet is
The temperature was 800 to 1050 ° C for ferritic stainless steel, 900 to 1200 ° C for austenitic stainless steel, and 780 to 850 ° C for martensitic stainless steel. Next, these cold-rolled sheets were subjected to electrolytic treatment (electricity: 40 C / dm ² ) in a neutral salt (20% Na ₂ SO ₄ , 80 ° C.), and nitric hydrofluoric acid having a concentration shown in Table 2 was obtained. Finish pickling was performed in the aqueous solution. At the time of finish pickling, the dissolution potential of the cold rolled sheet was adjusted to the potential shown in Table 2 by external potentiometer. The amount of dissolution was a value shown in Table 2.

An antibacterial test and a corrosion resistance test were performed on these No. 2 finished stainless steel sheets. Also,
To confirm the durability and durability of the antibacterial property,
After rubbing lightly back and forth five times with 400 abrasive papers, an antibacterial test was performed. In addition, Ag of No. 2 finish stainless steel sheet surface
The particle amount was measured for the area ratio by an image analyzer using an electron beam microanalyzer.

The outline of the test method for 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 x 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 placed 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 is a relative temperature.) The viable cell count 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.

Bacterial reduction rate (%) = (number of bacteria of control−number of bacteria after test) / (number of bacteria of control) × 100 The number of bacteria of control is the number of bacteria after the antibacterial test of the stainless steel material 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 solution of NaCl (temperature: 35 ° C.) for 0.5 hours 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.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

[0046]

[Table 4]

The examples of the present invention show 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 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, the rusting area ratio is 15%.
The following were accepted. (Example 2) Stainless steel having the chemical composition shown in Table 3 was melted and made into a slab by a continuous casting method. 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 annealed in a C gas combustion atmosphere (oxygen 3%, carbon dioxide 7%, steam 20%, balance nitrogen). The annealing temperature of the cold rolled sheet is
The temperature was 800 to 1050 ° C for ferritic stainless steel, 900 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 (electricity: 40 C / dm ² ) in a neutral salt (20% Na ₂ SO ₄ , 80 ° C.), and nitric hydrofluoric acid having a concentration shown in Table 4 was obtained. Finish pickling was performed in the aqueous solution. In addition, at the time of finish pickling, the dissolution potential of the cold rolled sheet was adjusted to the potential shown in Table 4 by external potentiometer. The amount of dissolution was a value shown in Table 4.

Next, for some steel sheets, Table 4
Under the conditions shown below, nitric acid electrolytic pickling was performed. In addition, in this nitric acid electrolytic pickling, the electric potential of the steel plate was temporarily held once at the holding potential shown in Table 4. An antibacterial test and a corrosion resistance test were performed on these No. 2 finished stainless steel plates in the same manner as in Example 1. Also, as in Example 1, the surface was # 400 to confirm the antimicrobial durability and durability.
Rubbed lightly and reciprocally five times with an abrasive paper, and then performed an antibacterial test. The area ratio of the Ag particles on the surface of the No. 2 finished stainless steel sheet was measured by an image analyzer using an electron beam microanalyzer.

[0051]

[Table 5]

[0052]

[Table 6]

[0053]

[Table 7]

[0054]

[Table 8]

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, Comparative Examples outside the scope of the present invention have degraded antibacterial properties, degraded corrosion resistance, or both.

[0056]

According to the present invention, any type of ferritic, austenitic or martensitic stainless steel having excellent antibacterial properties and corrosion resistance can be provided.
It has a remarkable industrial effect. 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.

Continuing from the front page (72) Inventor Masayuki Ota 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Engineering Co., Ltd. (72) Inventor Shogo Kikuyama 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Engineering Co., Ltd. In the laboratory (56) References JP-A-10-259456 (JP, A) JP-A-11-12692 (JP, A) JP-A-4-333584 (JP, A) JP-A-10-237643 (JP, A) JP-A-10-259457 (JP, A) JP-A-11-256284 (JP, A) JP-A-2000-234125 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61L 2/16 C22C 38/46 C23G 1/00-1/10 C25F 1/06

Claims (2)

(57) [Claims] 1. A cold-rolled stainless steel containing 0.0010 to 0.10 wt% of Ag is subjected to annealing and pickling sequentially.
o. In the method for producing a two-finished stainless steel material , the final pickling of the pickling treatment is performed by nitric acid 20 to 200 g / l and hydrofluoric acid 5 to 10
In a nitric hydrofluoric acid aqueous solution containing 0 g / l, the dissolution potential of the cold-rolled stainless steel material is adjusted to −50 mV or less with respect to the AgCl electrode, and the surface of the cold-rolled stainless steel material is dissolved by 0.1 μm or more in the depth direction. A method for producing a No. 2 finished stainless steel material having excellent antibacterial properties, characterized by pickling in an aqueous nitric hydrofluoric acid solution. 2. Following the pickling in the aqueous nitric hydrofluoric acid solution,
In 15 wt% nitric acid aqueous solution, at least once, the antimicrobial according to claim 1, characterized in that the nitric acid electrolysis pickling for holding the potential of the cold-rolled stainless steel to AgCl electrode below -100mV Excellent No. 2 finish stainless steel sheet manufacturing method.