JP2001121420A - Method of manufacturing stainless steel polished excellent in germ resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a stainless steel which is polished being excelling in germ resistance. SOLUTION: A stainless steel material containing Ag, excellent in germ resistance, is mechanically polished with polishing oil containing not more than 1 wt.% of S, or preferably having a ratio S/Ag between the content of S and the content of Ag in the stainless steel, which is not more than 25. Further, it may be mechanically polished without using the polishing oil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a stainless steel material having excellent antibacterial properties, and more particularly to a method for polishing and finishing a stainless steel material, which is suitable for daily necessities, medical equipment and building materials. The stainless steel material referred to in the present invention includes a steel plate, a steel strip, and a steel pipe.

[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, as disclosed in JP-A-8-156175, an alloy layer or a metal layer containing an antibacterial metal is formed on the surface of a stainless steel sheet. Various steel plates having both corrosion resistance and antibacterial properties by applying a pigment containing silver have been proposed. However, applications of steel sheets that are required to have both antibacterial properties and corrosion resistance properties include, for example, cleaning and repeated washing with a scourer for a long period of time, such as kitchen utensils and tableware used at home. There is a member whose surface is rubbed as a result.

In such severe applications, Japanese Patent Application Laid-Open
In the methods disclosed in JP-A-8-49085 and JP-A-8-156175, there is a problem that the layer containing the antibacterial metal is peeled off or removed, and the effect cannot be expected. To solve such a problem, a method of adding an antibacterial metal to steel has been proposed. For example, JP-A-10-259457 discloses that
Austenitic stainless steel containing 0.5 to 4.0% by weight of Cu and 0.05 to 1.0% by weight of Ag and having improved antibacterial properties has been proposed.

[0004] However, when Cu is contained as an antibacterial metal in a stainless steel plate, the following problems have emerged. In order for a Cu-containing stainless steel plate to exhibit antibacterial properties, it is necessary for Cu to be dissolved as ions from the surface of the steel plate. Dissolution of Cu as ions means that the passive film is destroyed at that point,
Even if the antibacterial property is improved, the corrosion resistance is significantly deteriorated. Therefore, it has been difficult for a stainless steel sheet containing a large amount of Cu to achieve both antibacterial properties and corrosion resistance.

Japanese Patent Application Laid-Open No. Hei 10-259456 discloses that a matrix 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 μm or less has an area fraction of 0.03% or more in matrix. An antibacterial stainless steel sheet dispersed therein has been proposed. Further, JP-A-11-12692 discloses that Ag: 0.0005 to
A ferritic stainless steel excellent in antibacterial properties containing 0.30% by weight and V: 0.01 to 0.30% by weight has been proposed.

[0006]

Generally, a stainless steel material is subjected to a heat treatment after cold rolling, and further to a descaling treatment such as pickling. Depending on the application, the stainless steel material is further finished with No. 4 finish and HL. (Hairline) Polishing by mechanical polishing such as finishing is performed. However, when the polishing finish by such a mechanical polishing process is applied to an antibacterial stainless steel sheet manufactured by the technology described in JP-A-10-259456, JP-A-11-12692, etc., the antibacterial property varies. In some cases, the antibacterial property was not stably exhibited.

An object of the present invention is to provide a method for producing a polished stainless steel excellent in antibacterial properties, which can advantageously solve such problems of the prior art and stably exhibit antibacterial properties. The stainless steel material targeted by the present invention is
A stainless steel material containing Ag was used. Ag exerts the same antibacterial properties even with a content of about one-hundredth of Cu. Ag has a very low degree of damage to the passivation film even when dissolved as ions, and has an advantage that corrosion resistance is much less deteriorated than Cu. For this reason, in the present invention, Ag was selected as the antibacterial metal element.

[0008]

Means for Solving the Problems In order to achieve the above object, the present inventors have intensively studied to find out what factors affect antibacterial properties. As a result, the present inventors have found that, when polishing and finishing an antibacterial stainless steel material containing Ag, there is a problem in the form in which Ag is present and the polishing oil used for mechanical polishing. Then, S added to the polishing oil for the purpose of improving the polishing power, and Ag on the surface of the steel material react to become Ag ₂ S, and it was found that the antibacterial property was relatively reduced. It has been found that the antibacterial property of the stainless steel material can be maintained even when the polishing is performed by suppressing the content to 0 or 1% by mass or less. Antibacterial action is Ag
Oxide> Ag particles> Ag sulfide is superior, and antibacterial activity is lower when Ag is present as Ag sulfide than when it is present as Ag particles or Ag oxide.

First, a description will be given of experimental results on which the present invention is based. A No. 2B-finished SUS 430 steel sheet containing 0.045% by mass of Ag is further mechanically polished using a polishing oil using a # 180 abrasive belt, and a No. 4 finished polished stainless steel sheet. did. The polishing oil used was a mineral polishing oil whose S content in the polishing oil was changed in the range of 0.2 to 2.5% by mass by changing the content of the additive. In addition, No. 4 finishing treatment by mechanical polishing without using polishing oil was also performed.

[0010] The steel plate thus polished was subjected to an antibacterial test according to the film adhesion method of the Antibacterial Products Technology Council. The result is shown in FIG. From FIG. 1, the number of viable bacteria decreases as the S content in the polishing oil decreases, and when the S content in the polishing oil becomes 1.0% by mass or less, the number of viable bacteria decreases to 10 ² cfu or less. It is seen that the antibacterial property of the steel sheet is maintained by 99.9% or more.

The present inventors have found that a similar effect is obtained in FIG.
As shown in the above, it has been found that it can be achieved also by mechanical polishing without using polishing oil. The present invention has been completed based on the above findings. That is,
The present invention provides a method for producing a stainless steel material in which a surface of a stainless steel material containing Ag: 0.0001 to 0.10% by mass is subjected to mechanical polishing to obtain a polished stainless steel material. % Is a method for producing a polished stainless steel material excellent in antibacterial properties, characterized in that it is a mechanical polishing process using a polishing oil of not more than%, and in the present invention, the S content of the polishing oil further comprises: In relation to the Ag content in the stainless steel material, the following equation (1) is used: S / Ag ≦ 25 (1) (where, S: S content of polishing oil (mass%), Ag: Ag of stainless steel material) (Content (% by mass)).

In the present invention, the content of Ag is 0.001 to 0.10% by mass.
In a method for producing a stainless steel material by mechanically polishing a surface of a stainless steel material containing the same to obtain a polished stainless steel material, the mechanical polishing process is a mechanical polishing process using no polishing oil. This is a method for producing a polished stainless steel material excellent in quality.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The steel to which the present invention is applied is Ag
Is a highly antibacterial stainless steel material containing 0.001 to 0.10% by mass, subjected to hot rolling and cold rolling, further subjected to annealing treatment and pickling treatment, and further to mechanical polishing of the steel material surface. It is a polished stainless steel material whose surface is finished by processing. Polishing finish in the present invention is No.3, No.4, HL, # 240, # 320, # 4 specified in JIS.
00 surface finish, but is not limited to.

The mechanical polishing in the present invention is an ordinary mechanical polishing in which the surface of a steel material is mechanically polished with a polishing belt having abrasive grains to obtain a predetermined finished surface. In the present invention,
In the case of polishing by supplying a polishing oil to the surface of a steel material during mechanical polishing, it is preferable to use a polishing oil having an S content of 1% by mass or less. When the S content of the polishing oil exceeds 1% by mass, as shown in FIG. 1, the antibacterial property of the polished steel material is significantly lower than the antibacterial property of the base material itself. It is said that the mechanism by which Ag exhibits antibacterial properties is that Ag reacts with bacterial respiratory enzymes such as Escherichia coli to stop bacterial respiration. For this purpose, it is important that Ag elutes in a solution such as water. When S is contained in the polishing oil,
S combines with Ag existing in the steel surface layer to form Ag ₂ S, and Ag
It is considered that the expression of antibacterial activity is reduced due to the inhibition of ionization.

In the present invention, a mineral type is exemplified as a suitable kind of polishing oil. The S content in these polishing oils can be adjusted by changing the amount of the additive.
In order to prevent the formation of Ag ₂ S and to stably exert the antibacterial action of Ag, the following formula (1) is used according to the Ag content in the stainless steel material. S / Ag ≦ 25 (1) ( Here, it is preferable to adjust the S content in the polishing oil so as to satisfy the following: S: S content of polishing oil (% by mass), Ag: Ag content of stainless steel (% by mass). Contributes to antibacterial action when S / Ag exceeds 25
Ag content decreases, and stable antibacterial properties cannot be obtained.

[0016] When polishing a stainless steel material containing 0.001 to 0.10 wt% of Ag and having an excellent antibacterial property, a mechanical polishing process using no polishing oil may be used. Note that, in the present invention, the mechanical polishing without using the polishing oil, dry polishing, buff polishing, those that do not use a polishing liquid such as barrel polishing at all, or in order to obtain a predetermined surface finish, such as water or the like It is assumed that a liquid having a considerably lower S content than the polishing oil and a S content of approximately 0% is used, and includes a polishing process in which seizure is prevented.

By not using the polishing oil, the polishing oil does not adversely affect the antibacterial element Ag, that is, does not inhibit the ionization of Ag, and the antibacterial property of the base material containing Ag is reduced by polishing. No longer.
As the stainless steel material excellent in antibacterial properties, which is the target steel material of the present invention, Ag-containing, ferritic stainless steel, austenitic stainless steel, martensitic stainless steel, and other types of stainless steel are all suitable. It is. In order to exhibit antibacterial properties, the Ag content in stainless steel material should be 0.001-0.10 mass%
And When the Ag content is less than 0.001% by mass, the expression of antibacterial properties is small, and when the Ag content exceeds 0.10% by mass, the effect of improving the antibacterial properties is saturated, and an effect commensurate with the content cannot be expected. The alloy elements other than Ag are not particularly limited. Any element may be contained as long as the element does not inhibit the antibacterial property.

[0018]

EXAMPLES (Example 1) Steel having the chemical components shown in Table 1 was melted by a converter-secondary refining, and a slab having a thickness of 200 mm was produced by a continuous casting method. These slabs are heated to 1170 to 1240 ° C and hot-rolled into 4 mm thick hot-rolled sheets.These hot-rolled sheets are annealed, pickled, and then cold-rolled.
0.8 mm thick cold rolled sheet. Further, these cold-rolled sheets were annealed and pickled, and then mechanically polished using polishing oils shown in Table 2 to obtain polished stainless steel sheets shown in Table 3. In addition, some steel plates were subjected to mechanical polishing using no polishing oil (water was used to prevent seizure).

[0019]

[Table 1]

[0020]

[Table 2]

Test pieces (50 × 50 mm) were collected from these polished stainless steel plates and evaluated for antibacterial properties. The antibacterial properties were evaluated according to the following film adhesion method of the Antibacterial Product Technology Council. (Antibacterial test) 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 was adjusted to 2.5 × 10 ⁵ cfu / sheet. 1/500 N
The B solution is a 50% normal Bion medium (NB)
It is a dilution of 1: 0. Normal Bion medium (NB)
Means meat extract 5.0g, sodium chloride 5.0g, peptone 1
0.0 g, purified water 1.000 ml, 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: 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 in test) − (number of bacteria after test)} / (number of bacteria in control) × 100 Here, the number of bacteria in the control does not include antibacterial treatment. The number of viable bacteria after the antibacterial test of stainless steel sheet. (Here, 5.
It is 1 × 10 ⁶ . ) The number of bacteria after the test is the number of viable bacteria measured.

Table 3 shows the results of the antibacterial test.

[0026]

[Table 3]

In each of the examples of the present invention, no decrease in antibacterial property was observed, and the antibacterial property was equivalent to that without mechanical polishing (base material). In contrast, comparative examples that fall outside the scope of the present invention are:
Antibacterial properties disappear or decrease. By the way, the number of viable bacteria
5.1 × 10 ³ cfu or less and 99.9% or more of the sterilized cells passed. (Example 2) Steel having the chemical components shown in Table 4 was converted to converter-2.
The slab was melted by the following refining and made into a 200 mm thick slab by continuous casting. These slabs are heated to 1170 to 1240 ° C, hot-rolled into 4 mm thick hot-rolled sheets, annealed and pickled, and then cold-rolled into 0.8 mm-thick cold-rolled sheets. And Further, these cold-rolled sheets were annealed and pickled, and then mechanically polished using polishing oils shown in Table 5 to obtain No. 4 finished polished stainless steel sheets.

[0028]

[Table 4]

[0029]

[Table 5]

Test pieces (50 × 50 mm) were sampled from the polished stainless steel plates and subjected to an antibacterial test in the same manner as in Example 1 to evaluate antibacterial properties. The evaluation of antibacterial activity was evaluated as ◎ when the sterilization rate was 99% or more, ○ when less than 99% and 50% or more, and x when less than 50%. Table 6 shows the results.

[0031]

[Table 6]

Comparative examples (steel Nos. 18 and 19) which were mechanically polished using a polishing oil having an S content of more than 1% by mass outside the scope of the present invention were all antibacterial. Of the present invention (steel sheet N)
o.11 to No.17) show excellent antibacterial properties (evaluation: ◎, ○) with a sterilization rate of 50% or more. In addition, the ratio of the S content (mass%) in the polishing oil to the Ag content (mass%) in the stainless steel material, a mechanical polishing process using a polishing oil having an S / Ag of 25 or less. Invention Examples (Steel Sheet No.11, No.12
, No.14, No.15, No.17) all had a sterilization rate of 99.
% Or more (evaluation:）), showing particularly excellent antibacterial properties.

[0033]

According to the present invention, a polished stainless steel material having excellent antibacterial properties can be stably provided, and the industrially remarkable effect is achieved. Further, according to the present invention, there is also an effect that the antibacterial stainless steel material can be applied to members used for outer walls, handrails, and the like.

[Brief description of the drawings]

FIG. 1 is a graph showing the effect of the S content in polishing oil on the antibacterial properties of a polished stainless steel plate.

FIG. 2 is a graph showing the effect of polishing without polishing oil on the antibacterial properties of a polished stainless steel plate.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Haruhiko Ishizuka 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Chiba Works of Kawasaki Steel Corporation (72) Inventor Hideaki Yamashita 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Inside the Chiba Works, Steel Works (72) Inventor Takeshi Yokota 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba

Claims (3)

[Claims] 1. A method for producing a stainless steel material by mechanically polishing a stainless steel material containing 0.001 to 0.10 mass% of Ag to obtain a polished stainless steel material, wherein the mechanical polishing process is performed so that the S content is 1 mass%. A method for producing a polished stainless steel material having excellent antibacterial properties, characterized by mechanical polishing using the following polishing oil. 2. The polished stainless steel material according to claim 1, wherein the S content of the polishing oil further satisfies the following expression (1) in relation to the Ag content in the stainless steel material. Manufacturing method. S / Ag ≦ 25 (1) where, S: S content of polishing oil (% by mass), Ag: Ag content of stainless steel material (% by mass) 3. A method for producing a stainless steel material by mechanically polishing a stainless steel material containing 0.001 to 0.10 mass% of Ag to obtain a polished stainless steel material, wherein the mechanical polishing is performed without using a polishing oil. A method for producing a polished stainless steel material having excellent antibacterial properties, characterized by processing.