JP2000234125A - Manufacture of silver-containing stainless steel strip excellent in antibacterial characteristic, and steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively produce an antibacterial action by Ag and to maintain highly stable antibacterial characteristic over a long period by rolling a steel strip containing specific amounts of Ag, holding it at a temperature in a specific region, and subjecting Ag phases to spheroidizing treatment. SOLUTION: As a stainless steel to be the object, ferritic, austenitic, martensitic, dual-phase stainless steels, etc., are exemplified, without restrictions on the kind of steels so far as 0.01-1 wt.% Ag is contained. The spheroidizing of Ag phases is accelerated by heat treating the stainless steel strip at a temperature not lower than the melting point of Ag. Because Ag in the steel is present in the form of compounds or solid solutions of C, S, Si, Mn, O, Mg, Al, Zn, etc., these Ag phases are ordinarily melted by heating and holding at 900-1,300 deg.C and spheroidized. Accordingly, heat treatment at >=900 deg.C is necessary to spheroidize the Ag phases; spheroidizing becomes more accelerated the higher the temperature rises, but this effect reaches saturation if the temperature exceeds 1,300 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to kitchen appliances, electric appliances,
The present invention relates to a stainless steel strip suitable for applications requiring antibacterial properties in a wide range of fields such as building materials, mechanical devices, and chemical devices.

[0002]

2. Description of the Related Art SUs are required for corrosion resistance in a general environment, because various equipment used in kitchen appliances, hospitals, etc., pipes for handrails provided in transportation means such as buses and trains are required to have corrosion resistance in general environments.
Stainless steel represented by S304 is used.
However, in recent years, hospital infections caused by Staphylococcus aureus have become a problem, and as equipment used in environments used by an unspecified number of people, materials that have not only corrosion resistance but also excellent hygiene functions are desired. ing. In addition, as a material used for various machines and instruments, a maintenance-free material having antibacterial performance that does not need to prevent infection such as periodic disinfection is not limited to the properties as a general structural material. I have. Examples of the material having antibacterial properties include a stainless steel sheet coated with a paint containing an antibacterial agent, a resin or the like, a stainless steel sheet plated with a matrix containing an antibacterial component, and a stainless steel sheet provided with antibacterial properties to the steel itself ( JP-A-5-228202, JP-A-6-10191, and JP-A-9-170053) are known.

[0003]

When a paint or resin containing an antibacterial agent is applied and laminated on the surface of a stainless steel plate, the texture and surface gloss peculiar to the stainless steel are impaired, and the commercial value is reduced. In addition, the antibacterial coating is susceptible to damage such as cracking, chipping, and abrasion during processing or use. When the damaged film is exposed to a moist environment, the dissolution of antibacterial components is promoted,
It causes deterioration of appearance and antibacterial property. With composite plating mixed with antibacterial components, the adhesion of the plating layer is not sufficient,
There is a disadvantage that the workability is reduced. In addition, the appearance is deteriorated due to the dissolution, abrasion, chipping and the like of the plating layer, and the antibacterial action is weakened. On the other hand, stainless steel to which antibacterial components such as Ag and Cu are added has antibacterial properties as compared with painting and plating, since the material itself has antibacterial properties. Is not damaged.

[0004] In Cu-added antibacterial stainless steel, the antibacterial effect is improved by distributing Cu as a precipitate in the steel.
However, long-term aging treatment is required after hot rolling for Cu precipitation, which causes a decrease in productivity and an increase in production cost. When the Cu content is set high, C
As a result, u is easily precipitated, and aging treatment for a short time becomes possible.
However, a high Cu content deteriorates the hot workability of stainless steel and causes a reduction in productivity.

[0005]

SUMMARY OF THE INVENTION The present invention has been devised to solve such a problem.
By using g as an antibacterial component and spheroidizing the Ag phase, the antibacterial action of Ag can be effectively exerted, and an object of the present invention is to provide a stainless steel strip exhibiting highly stable antibacterial properties for a long time. I do. In order to achieve the object, the production method of the present invention rolls a stainless steel strip containing 0.01 to 1% by weight of Ag, and then 900 to 130%.
It is characterized in that the Ag phase is subjected to a spheroidizing treatment while being kept in a temperature range of 0 ° C. Rolling prior to the spheroidizing treatment of the Ag phase includes cold rolling.

[0006]

[A] Ag exhibits an antibacterial effect superior to Cu and is an element having a large microbicidal effect. Also, unlike Cu,
The presence of Ag or Ag ions kills surrounding bacteria and bacteria. Moreover, since Ag is an element having a large specific gravity and hardly forming a solid solution in Fe, Ag added to stainless steel does not require a long-term aging treatment after hot rolling like Cu, and is added to the matrix as a different phase. Spread. However, the mere addition of Ag to molten stainless steel does not result in a structure in which the Ag phase is unevenly distributed and the phase containing a high concentration of Ag is not uniformly dispersed in the matrix, and a material exhibiting a stable antibacterial action is obtained. hard. Therefore, in order to uniformly disperse the Ag phase in the Ag-containing stainless steel,
Various manufacturing conditions were investigated and examined.

First, the antibacterial properties of a sample made of a stainless steel containing Ag were evaluated. However, the antibacterial action of Ag was not stably exhibited in a stainless steel manufactured by a normal manufacturing method. Similarly, even in stainless steel containing a large amount of Ag, stable antibacterial properties could not be obtained. The unstable antibacterial properties are presumed to be the result of uneven distribution of Ag in the steel and uneven distribution of the Ag phase. The distribution form of the Ag phase is affected by manufacturing conditions. Most Ag phases are distributed in a linear form elongated in the rolling direction like A type inclusions as hot rolling → cold rolling and rolling progress, but some Ag phases are dispersed in a fine spherical form. are doing. In addition, antibacterial action and Ag
Investigation of the relationship with the distribution form of the phase revealed that the linear distribution of the Ag phase rather tended to degrade the antibacterial action, and that uniform dispersion of the spherical Ag phase was effective in stabilizing the antibacterial action. I learned.

The spheroidization and uniform dispersion of the Ag phase are promoted by heat-treating the rolled stainless steel strip at a temperature higher than the melting point of the Ag phase. When the stainless steel strip is heat-treated at a temperature equal to or higher than the melting point of the Ag phase, Ag in the steel is preferentially melted, and the Ag phase linearly expanded by rolling is divided and spheroidized. Moreover, since Ag does not form a solid solution in the matrix, the spheroidized Ag phase is uniformly dispersed in the matrix as fine particles. As a result, the spheroidized Ag phase having antibacterial activity dramatically improves the antibacterial properties, and exhibits a highly stable antibacterial action.

The spheroidization of the Ag phase is caused by the melting point of Ag (961.
9 ° C.) or more by heat treating the stainless steel strip at a temperature above 9 ° C.). Ag contained in steel is C, S,
It often exists as a compound or a solid solution with a metal element such as Si, Mn, O, Mg, Al, Zn, etc., and these Ag phases are usually melted by heating at 900 to 1300 ° C. to form spheroids. The spheroidization of the Ag phase requires a heat treatment at a temperature of 900 ° C. or higher, and the higher the heating temperature, the more the spheroidization is promoted. However, even when heating at a temperature exceeding 1300 ° C., no spheroidization promoting effect commensurate with the temperature rise was observed,
There is a concern that the yield may decrease due to oxidation of the matrix. The heating and holding time is preferably as long as possible, but when the linear Ag phase is dissolved, it changes into a divided form in a relatively short time. Therefore, the heating time can be shortened as long as spheroidization can be confirmed. The holding time defined in the present invention refers to the time for which the steel strip and the steel sheet placed in the heating furnace are kept at the target temperature, except for the time required for the steel strip and the steel sheet to reach the target temperature, and It is different from the furnace time until it comes out. The holding time refers to the time during which the steel strip and the steel sheet are maintained at a temperature equal to or higher than the target temperature in the range of 900 to 1300 ° C., and does not necessarily need to be maintained at a constant target temperature.

The spheroidizing treatment of the Ag phase is a treatment for finely dividing the Ag phase linearly expanded by rolling. Since the divided Ag phase solidifies in the divided form as it is, it becomes a dispersed Ag phase effective for antibacterial properties even if it does not become a perfect sphere. Rolling includes the ingot rolling of ingots manufactured by the ingot casting method, the hot rolling of slabs manufactured by continuous casting and the ingots manufactured by ingot rolling, and the cold rolling after hot rolling. The spheroidizing heat treatment may be performed at any stage. The stainless steel strip referred to in the present invention also includes a hot-rolled sheet or a cold-rolled sheet produced by subjecting a hot-rolled sheet or a cold-rolled sheet to polishing, shot blasting, pickling, annealing, temper rolling and the like. Use in meaning. A
Although the g phase becomes spheroidized by one heat treatment, the dispersion form of the Ag phase is further improved by a plurality of spheroidization heat treatments. By performing the spherical heat treatment a plurality of times, it is possible to uniformly disperse the fine spherical Ag phase into the matrix.

The heat treatment atmosphere is vacuum, air, Ar, N
₂ , H ₂ , CO, CO ₂ and a mixed gas thereof are used. Even an atmosphere containing a small amount of impurity gas does not adversely affect the spheroidization of the Ag phase. As long as the stainless steel targeted by the present invention contains 0.01 to 1% by weight of Ag, there is no restriction on the type of steel, and ferritic, austenitic, martensitic,
There are phase systems, etc. Antibacterial action is 0.01% by weight or more of Ag
The content becomes remarkable and strengthens as the Ag content increases. From the viewpoint of the antibacterial effect, the higher the Ag content, the better. However, if an excess amount of Ag exceeding 1% by weight is included, the uneven distribution of the Ag phase proceeds, and the antibacterial properties are likely to vary. As alloying components other than Ag, 9 to 32% by weight of Cr required for ensuring corrosion resistance, and 26% by weight or less of Ni required for maintaining an austenite phase in an austenitic system.
Etc. In addition, C, S usually contained in stainless steel
i, Mn, and Mo, B,
Al, Ti, Nb, V, Zr, Zr, Y, Ca, Mg,
One or two or more of W, rare earth metal (REM) and the like can be included.

[0012]

Example 1 Various stainless steels having the compositions shown in Table 1 were used for 30 samples.
In a vacuum melting furnace, a hot rolled sheet was produced. Anneal and cold-roll the hot-rolled sheet, finally plate thickness 0.5-1.0mm
Cold rolled sheet.

[0013]

The cold rolled sheet was heated under the conditions shown in Table 2 to spheroidize the Ag phase. Some sheets were subjected to spheroidizing heat treatment after hot rolling. A test piece was cut out from each cold-rolled sheet, and after surface polishing, spheroidization of the Ag phase was observed by SEM. Next, the test piece cut out from each cold-rolled plate was subjected to an antibacterial test. In the antibacterial test, Staphylococcus
aureus IFO12732 (Staphylococcus aureus)
And cultured with shaking in a normal broth medium at 35 ° C. for 16 to 24 hours to prepare a culture solution. The culture was diluted 20,000-fold with a sterile phosphate buffer solution to prepare a bacterial solution.

1 ml of the bacterial solution is dropped on the surface of the test piece,
Stored at 24 ° C. for 24 hours. After storage, the test piece was washed out with an SCDLP medium, and the obtained liquid was subjected to a viable cell count by a pour plate method (cultured at 35 ° C. for 2 days) using a standard agar medium. According to this test method, the lower the viable count after 24 hours compared to the initial viable count, the stronger the antibacterial property of the material. In the antibacterial test, two test pieces were prepared for each steel type, and the antibacterial properties were evaluated by the average of two tests. In addition, (initial viable cell count−average viable cell count after 24 hours) / (initial viable cell count) × 100 = sterilization rate (%) It was determined that there was.

The results of the antibacterial test are shown in Table 2 together with the spheroidizing treatment conditions for the Ag phase. As is clear from Table 2, when the stainless steel plate was heat-treated at 900 ° C. or more, Ag
It can be seen that the phase is spheroidized, showing a high sterilization rate of 99% or more, and that a stable antibacterial action is maintained. On the other hand, when the spheroidizing treatment conditions did not satisfy the conditions specified in the present invention, as shown in Table 3, the spheroidizing of the Ag phase was insufficient, and the sterilization rate did not reach 99%. Latter 2
The number of viable bacteria determined from the test pieces also varied, and the antibacterial action was unstable.

[0017]

[0018]

[0019]

Example 2 C: 0.062% by weight, Si: 0.42% by weight, Mn: 0.30% by weight, Ni: 0.28% by weight,
Cr: 16.09% by weight, N: 0.018% by weight, M
o: 0.03% by weight, Cu: 0.02% by weight, Ag: 0.
A ferritic stainless steel containing 70% by weight (70 tons / charge) was melted through an electric furnace, a converter, and a VOD process, and continuously cast into a slab. The slab is hot-rolled to a thickness of 3.6 mm, then heated at 780 ° C. for 6 hours, and then subjected to hot-rolled annealing by furnace cooling, and 0.7 m in thickness without intermediate annealing after pickling.
m. Next, the steel sheet was passed through a continuous annealing furnace.
The Ag phase was subjected to spheroidizing treatment under the conditions shown in (1), and after pickling and temper rolling, a cold-rolled steel strip as a final product was produced.

A test piece was cut out from each of the obtained cold-rolled steel strips, and the spheroidization of the Ag phase was examined in the same manner as in Example 1, and the specimen was subjected to an antibacterial test. As can be seen from the survey results in Table 4,
When the Ag phase was subjected to spheroidizing treatment at a temperature of 900 ° C. or more, a stable antibacterial effect was exhibited with a high sterilization rate of 99% or more. On the other hand, when heat treatment was performed at a temperature below 900 ° C., the spheroidization of the Ag phase was insufficient, the sterilization rate was low, and the number of viable bacteria obtained from the two test pieces after the test was reduced. The antibacterial properties were also unstable, as can be seen from the variation in the antibacterial properties.

[0021]

[0022]

As described above, in the present invention, the Ag-containing stainless steel strip after rolling is 900-130.
By heating to 0 ° C., the linear Ag phase generated by rolling is divided and spheroidized, thereby effectively exhibiting the antibacterial action of Ag and imparting highly stable antibacterial properties. The stainless steel strip thus obtained exhibits excellent antibacterial properties even with solid materials and maintains excellent antibacterial properties for a long period of time, so that kitchen equipment, electrical equipment,
Used in a wide range of fields such as building materials, chemical equipment, and medical equipment.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shuhisa Hiruhama 4976 Nomura Minami-cho, Shinnanyo-shi, Yamaguchi Prefecture Inside Nisshin Steel Research Institute of Technology (72) Inventor Isamu Noguchi 4976 Nomura-minami-cho, Shinnanyo-shi, Yamaguchi Pref. New Steel Co., Ltd. Technical Research Laboratory F term (reference) 4C058 AA06 AA19 AA23 AA24 AA30 BB07 JJ03 JJ05 4K043 AA01 AB00 AB01 AB02 AB03 AB04 AB12 AB15 AB19 AB20 AB21 AB22 AB23 AB24 AB27 AB28 AB29 AB30 AB32 AB33 BB04 DA05 EA04 FA

Claims (3)

[Claims] 1. An antibacterial property, characterized in that a stainless steel strip containing Ag: 0.01 to 1% by weight is rolled and then kept in a temperature range of 900 to 1300 ° C. to spheroidize the Ag phase. An excellent method for producing an Ag-containing stainless steel strip. 2. The antibacterial A according to claim 1, wherein the stainless steel strip is cold-rolled before the spheroidizing treatment of the Ag phase.
Method for producing g-containing stainless steel strip. 3. An Ag-containing stainless steel strip excellent in antibacterial properties, produced by the method according to claim 1.