JP3309769B2 - Cu-containing stainless steel sheet and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for producing Cu
The present invention relates to a Cu-containing ferritic stainless steel sheet having a structure in which precipitates are dispersed and exhibiting excellent antibacterial properties, and a method for producing the same.

[0002]

2. Description of the Related Art Ferritic stainless steel sheets are preferred for their excellent corrosion resistance, beautiful appearance, cleanliness, and high-grade appearance, and are widely used in various applications such as kitchens, dishes, bathtubs, washing machine tubs, and the like. Is one of the materials used. However, recently, in materials used for the above-mentioned applications, the generation of dirt and odor due to the propagation of various bacteria in the use environment has become a problem, and furthermore, pathogenic bacteria such as Escherichia coli and Staphylococcus aureus have become problematic. There is a growing concern about the effects of breeding on the human body.

However, problems such as various germs and pathogens are common to all kinds of items around us, and therefore, a material having resistance to various germs and pathogens (performance called "antibacterial property") has been desired. In the field of plastic products, chemical fiber products, paints and the like, the development and sales of antibacterial products have already been actively carried out. Needless to say, as described above, antimicrobial demands have been increasing for metal materials, and various studies have been conducted, and they have been known as antibacterial metal elements.
It has been studied to use Au, Ag, Cu, Ni, etc. in their original form for “particularly antibacterial members”.

Further, recent studies have revealed that “Cu, Ni as an alloying element” contained in stainless steel also contributes to the development of antibacterial properties of the material (stainless steel). Therefore, based on such research results, for example, JP-A-8-53738, JP-A-8-60301, JP-A-8-60302, and JP-A-8-603
No. 03 or Japanese Patent Application Laid-Open No. H08-104953 proposes a technique relating to a stainless steel sheet which exhibits antibacterial properties by concentrating Cu in the surface layer.

[0005] However, in the techniques proposed through the above publications, the stainless steel sheet according to the proposal is subjected to plastic working such as press working, bending work, etc. in order to form a final product, or a design is applied to the stainless steel sheet. When mechanical surface polishing such as buffing, hairline polishing, etc., is performed to impart a property, the joint after welding (weld temper)
If a treatment such as pickling or electrolytic polishing is applied to make the color part less noticeable, the problem is pointed out that the Cu-enriched layer on the surface of the stainless steel plate disappears and the antibacterial effect tends to be lost. Was done.

[0006] For this reason, Japanese Patent Application Laid-Open No. 8-229107 discloses a method of regenerating a Cu-concentrated layer on a surface once lost and imparting antibacterial property again by using a "polished or processed Cu-containing stainless steel product. Immersion in acidic solution ". However, this proposed method also leads to the need for a general processing maker, a polishing maker, and other consumers to install a new acidic solution immersion equipment.
There has been a concern that problems such as an increase in production costs of the product accompanying this will occur. In addition, a decrease in productivity due to an increase in the number of treatment steps (acid solution immersion step) could not be denied.

In view of the above, an object of the present invention is to provide various kinds of ferritic stainless steel sheets which are frequently used in kitchens, tableware, bathtubs, washing machine tubs and the like, where antibacterial properties tend to be particularly problematic. An object of the present invention is to provide a means for stably exhibiting an antibacterial effect without requiring special treatment even after plastic working or surface polishing treatment.

[0008]

The antibacterial activity of Cu is based on the fact that Cu eluted as an ion from the ingot reacts efficiently with the thiol present in the respiratory metabolic oxygen of the cell, thereby inactivating the thiol. Is considered to be caused by suppressing the propagation of various bacteria and pathogenic bacteria. However, the upper limit of the Cu content in practical Cu-containing stainless steel is naturally limited from the viewpoint of hot workability, corrosion resistance, and the like. And
In the Cu content range of such a practical Cu-containing stainless steel, the amount of Cu eluted in the use environment is small, and the above antibacterial property of Cu is not sufficiently exhibited. Therefore, the conventionally known `` means for imparting antibacterial properties to Cu-containing stainless steel '' is based on the idea of forming a concentrated layer of Cu on the surface layer of stainless steel, thereby securing the amount of Cu eluted. It was devised below.

[0009] However, in such a means, when stainless steel subjected to a treatment for imparting antibacterial properties (stainless steel having a Cu-concentrated layer formed on a surface layer portion) is subjected to plastic working, surface polishing, or the like, the surface layer is subjected to such processing. As described above, there is a possibility that the Cu-enriched layer disappears and the antibacterial effect is lost.

Therefore, the present inventors, after conducting research from various viewpoints, have found that “the amount of Cu eluted in the environment in which stainless steel sheets are used” is changed to “the form and distribution of Cu itself present in the stainless steel sheets”. And the correlation between "the state of Cu present in the final product" and "the amount of Cu eluted in that state" and "antibacterial activity" for various Cu-containing ferritic stainless steel sheets. As a result of the investigation, `` If Cu precipitates with a size greater than a certain value in a Cu-containing ferritic stainless steel sheet at the final product stage are present in a dispersed state at a ratio of a certain amount or more, they will elute in the use environment The amount of Cu to be added increases, so that excellent antibacterial properties are stably exhibited. " That is, regardless of the type of Cu-containing ferritic stainless steel sheet, the diameter is 0.05 μm or more when Cu is precipitated in a spherical shape, and the length is 0.05 μm or more when Cu is precipitated in a rod shape. If the Cu precipitates are dispersed and precipitated at a rate of 10 or more per 100 μm ^{2 of} an arbitrary cross section, the amount of Cu eluted as ions in the use environment becomes sufficiently large, and the ferrite-based It has been found that stainless steel sheets exhibit extremely good antibacterial properties.

FIG. 1 is a graph showing the results of an investigation of the relationship between the size and the number of precipitated Cu and the antibacterial performance in a Cu-containing ferritic stainless steel sheet.

The present invention has been made based on the above findings, and provides the following Cu-containing ferritic stainless steel sheet and a method for producing the same. (1) Cu precipitate having a size of 0.05 μm or more has a cross section of 100
Microstructure dispersed at a rate of 10 or more per μm ² (however , Cu
If the rich phase is precipitated at a rate of 0.2% by volume or more
Excluding) , a Cu-containing ferritic stainless steel sheet. ( 2) When hot- rolling Cu-containing ferritic stainless steel to produce sheet material, acid
When the product is washed, it is softened and annealed after hot rolling.
And wherein the score facilities prolonged annealing of one hour or more in a temperature range of 750 to 900 ° C. Te is size 0.05μm or Cu
Precipitates dispersed at a rate of 10 or more per 100 μm ^{2 in} cross section
For producing a Cu-containing ferritic stainless steel sheet having a reduced structure . ( 3) When rolling a Cu-containing ferritic stainless steel to produce a sheet material, 7
The process is characterized by securing a process of performing long-time annealing for 1 hour or more in a temperature range of 50 to 900 ° C., and a dimension of 0.05 μm or less.
Cu precipitates on the top of 10 or more per 100μm ²
A method for producing a Cu-containing ferritic stainless steel sheet having a structure dispersed in a proportion . ( 4) When rolling a Cu-containing ferritic stainless steel to produce a sheet material, 7
A process of performing long-time annealing for 1 hour or more in a temperature range of 50 to 900 ° C. is secured, and recrystallization annealing after final cold rolling is performed in 9 hours.
And carrying out at a temperature range of 50 ° C. or less, dimensions
Cu precipitates of 0.05 μm or more are 1 per 100 μm ^{2 in} cross section.
A method for producing a Cu-containing ferritic stainless steel sheet having a structure dispersed at zero or more .

In the present invention, the type of the target Cu-containing ferritic stainless steel sheet (chemical composition, or hot-rolled steel sheet, cold-rolled steel sheet, cold-rolled-annealed steel sheet, etc.)
And the Cu content is not particularly limited, but from the viewpoint of easiness and practicality in securing a Cu precipitate satisfying the above conditions, the Cu content is 0.8 to 3.5% by weight (hereinafter It is desirable that the percentage representing the component ratio be% by weight) (a more preferable range of the Cu content is 1.0 to 3.0%). That is, if the Cu content is less than 0.8%, depending on the precipitation treatment, Cu may not be sufficiently precipitated,
%, The hot workability deteriorates and industrial mass production becomes difficult. In addition, the corrosion resistance and cold
There is a possibility that the workability in the warm state may be deteriorated.

Further, as alloying elements or impurity elements contained in addition to Cu, C of 0.08% or less and C of 3.0% or less are contained.
Si, Mn of 1.0% or less, P of 0.05% or less, S of 0.01% or less, Cr of 10 to 30%, Ni of 1.0% or less, Mo of 2.0% or less,
N of 0.05% or less can be exemplified. Further, it is needless to say that one or two or more of 1.0% or less of Ti, 1.0% or less of Nb, and 1.0% or less of Al may be contained as needed.

[0015]

In the ferritic stainless steel sheet according to the present invention, Cu is an important element for imparting antibacterial properties to the steel sheet. In order for the Cu-containing ferritic stainless steel sheet to exhibit excellent antibacterial properties,
Must exist as a precipitate at the product stage, and its size is sufficiently large, and in order to suppress the dispersion of antibacterial performance depending on the sampling position of the manufactured ferritic stainless steel sheet, the thickness direction, It must be distributed as uniformly as possible in the width direction and in the longitudinal direction. According to transmission electron microscope observation results, the form of this precipitate is substantially spherical or rod-shaped, and when Cu is precipitated as a precipitate, its diameter is, or when Cu is deposited as a rod, Has a length of 0.05
Especially when it is more than μm, it exhibits remarkable antibacterial properties. The deposited Cu
Is present in a dispersed state at a rate of 10 or more per 100 μm ^{2 in} cross section, it becomes difficult for the Cu-containing ferritic stainless steel sheet to stably exhibit excellent antibacterial properties.

That is, if Cu is in a solid solution state in steel or even if it is precipitated, if the precipitation diameter or the precipitation length is less than 0.05 μm, the amount of Cu eluted in the use environment is reduced. It is insufficient and cannot provide excellent antibacterial properties to the Cu-containing ferritic stainless steel sheet. The more preferable size of the precipitated Cu is the precipitation diameter or the precipitation length.
0.1 μm or more. In addition, the precipitation diameter or precipitation length
Even if Cu is deposited with a size of 0.05 μm or more, if the precipitation state of such precipitates is not uniform, the antibacterial performance varies depending on the position where the material is collected from the steel sheet.
In order for stable antibacterial properties to be exhibited no matter where the material is sampled from the steel sheet, a "diameter or length of 0.05 mm
It is necessary that 10 or more Cu precipitates having a size of μm or more are dispersed and present at a rate of 10 or more per 100 μm ^{2 in} cross section. The number is 15 or more per 100 μm ^{2 of} steel sheet cross section.

The size and the number of precipitated Cu in the Cu-containing ferritic stainless steel sheet can be easily confirmed by observing with a transmission electron microscope.

As described above, in the Cu-containing ferritic stainless steel sheet according to the present invention (regardless of whether it is a hot-rolled steel sheet, a cold-rolled steel sheet or a cold-rolled-annealed steel sheet), a Cu precipitate having a specific size or more is obtained. Are almost uniformly dispersed and precipitated in the thickness direction, width direction, and longitudinal direction, so even if the surface layer is shaved off by plastic processing or surface polishing, it is exposed in the operating environment. Since Cu elutes stably from the deposited Cu as a starting point, the antibacterial property does not deteriorate.

Next, a method for producing the above-mentioned Cu-containing ferritic stainless steel sheet according to the present invention will be described in detail. In general, ferritic stainless steel sheets are prepared by hot rolling a slab obtained by continuous casting into a hot-rolled steel strip, which is then used for the purpose of “improving cold rollability” or “improving product performance”. The steel sheet is subjected to soft annealing and further subjected to pickling treatment and shipped as it is. Alternatively, the cold-rolled base material subjected to soft annealing is pickled and then subjected to "one cold rolling, annealing and acid treatment. Washing process (hereinafter referred to as "one cold rolling process") "or" two cold rolling and annealing / pickling processes (hereinafter referred to as "two cold rolling processes") " Usually, they are shipped.

In the case of manufacturing the “Cu-containing ferritic stainless steel sheet according to the present invention”, a sheet material is basically produced in substantially the same steps. After the hot rolling, or during the manufacturing process from the hot rolling to the final cold rolling, at least one long-time annealing for 1 hour or more in a temperature range of 750 to 900 ° C. is performed as a Cu precipitation treatment. Is done. The “long-time annealing as a Cu precipitation treatment” in the case of actual production is considered as “a product obtained by pickling as it is after softening annealing of a hot-rolled steel strip” or “one cold rolling process”. In the case of "2nd cold rolling process", "softening annealing of hot rolled steel strip" or "after the first cold rolling" And / or both of the "recrystallization annealing performed".

If the temperature of the “Cu precipitation treatment” is lower than 750 ° C., the deposited Cu cannot grow sufficiently and the size of the Cu precipitate in the product stage is insufficient, or the precipitation state The stainless steel plate does not exhibit stable antibacterial properties because of the non-uniformity. Further, when the temperature of the “Cu precipitation treatment” exceeds 900 ° C., when this Cu precipitation treatment is used in combination during the softening treatment of the hot-rolled steel strip, the crystal grains become coarse, so that the base material becomes brittle. In addition, it becomes difficult to pass the plate in the subsequent processing and the next step (cold rolling step), and when this Cu precipitation treatment is used in combination with the recrystallization annealing after the first cold rolling, the oxidation scale of the surface is reduced. The oxide scale cannot be removed in the next pickling step due to the formation of a thick layer, and a surface grinding step or the like is required, which leads to an increase in the number of steps or a deterioration in the surface gloss of the product, resulting in a decrease in commercial value. It is not preferable because it invites.

Similarly, if the "Cu precipitation treatment" is carried out after the final cold rolling, the oxide scale cannot be removed in the final pickling step, and the commercial value of the product also decreases. Also, even if the temperature of "Cu precipitation treatment (Cu precipitation annealing treatment)" is appropriate, if the annealing time is less than 1 hour, the growth of precipitated Cu is insufficient and stable antibacterial performance cannot be obtained. . Therefore, box type annealing is employed for this treatment.

Further, in the case where cold rolling (final cold rolling) is performed subsequent to the above-mentioned "Cu precipitation treatment" and then recrystallization annealing is performed, the recrystallization annealing is performed in a temperature range of 950 ° C. or less. It is necessary. That is, in the present invention, the method of recrystallization annealing is not particularly limited, and is a bright annealing method in which no pickling treatment is performed after annealing even in a continuous annealing pickling method in which pickling treatment is performed after annealing. However, if the temperature of the recrystallization annealing exceeds 950 ° C., the Cu precipitated by the Cu precipitation treatment will re-dissolve in the steel, and the precipitated Cu in the product stage
This is because there is a concern that the diameter or length of the Cu becomes small or the number of precipitated Cu decreases (in some cases, disappears). Therefore, it is not preferable to perform recrystallization annealing at a temperature exceeding 950 ° C. after the final cold rolling.

In some applications, the product which is obtained by omitting the recrystallization annealing after cold rolling may be provided as a product. In this case, since the Cu precipitated by the Cu precipitation treatment remains as it is, The antibacterial performance is not impaired.

Incidentally, the Cu precipitation treatment (75
Long-time annealing for 1 hour or more in the temperature range of 0 to 900 ° C)
Not only imparts the antibacterial performance of the product by precipitating Cu coarsely, but also results in the effect of reducing the amount of solute Cu in the steel and drastically softening the material. It also contributes to improved workability.

[0026]

The present invention will be described below by way of examples. [Example 1] C: 0.007%, Si: 0.2%, Mn: 0.2%, Cr: 20
%, Ni: 0.3%, N: 0.009%, Cu: 1.8%, and the balance is Cu-containing ferritic stainless steel consisting of Fe and unavoidable impurities. 40mm thickness x 140 by hot forging and machining
A hot-rolled material having a width of 85 mm and a length of 85 mm was manufactured. Then, the hot-rolled material was hot-rolled to obtain a hot-rolled steel sheet having a thickness of 4.5 mm.

Next, a plurality of test materials were cut out from the Cu-containing hot-rolled ferritic stainless steel sheet,
After performing a Cu precipitation treatment by box annealing for 2 hours at a temperature range of 0 ° C., a thin film test piece was collected from an arbitrary position of each test material, and the deposition state of Cu was confirmed by a transmission electron microscope. . Table 1 shows the state of Cu precipitation under each Cu precipitation treatment condition.

[0028]

[Table 1]

[0029] In order to confirm the antibacterial performance of the respective test material, Shi issues a _^1/4 parts of _^1/2 parts of the plate thickness surfaces by surface grinding a sample was cut out from each test material of Cu precipitates treated The material which was further polished by # 1000 was used as an antibacterial evaluation material. The following method was used for evaluating the antibacterial performance.

[0030] That is, implanted in a standard broth medium was selected Escherichia coli (E. coli), using a constant temperature shaker after incubation at "37 ° C., the conditions of 16-hour culture", the number of cultured bacteria with 10 ⁸ Thus, the bacterial solution was adjusted by diluting 10-fold and then diluting 1000-fold with phosphate-buffered saline to a final bacterial count of 10 ⁵ (CFU / ml) in the final dilution step. Next, 0.5 ml of the bacterial solution was inoculated on the surface of each evaluation material so that the number of bacteria was about 10 ³ to 10 ⁴ CFU on the entire surface, and a polyethylene film was placed thereon, and “35” was placed in a thermostat. C., 95% relative humidity "for 24 hours. After 24 hours, the polyethylene film was removed, the bacteria were washed from the surface of each evaluation material and the polyethylene film with 10 ml of physiological saline, and the obtained liquid was continuously applied to a standard agar medium. And the number of bacteria grown on the surface of the medium was measured. In this case, if the number of bacteria after 24 hours is smaller than the initial number of bacteria, it can be said that it has antibacterial properties. Further, as a control test for confirming the state of the bacteria, several drops of the bacterial solution were dropped on an empty plastic sterile dish, and the number of bacteria was measured in the same manner. In this case, if the initial number of bacteria and the number of bacteria after 24 hours are almost the same, it can be concluded that it is appropriate to evaluate the antibacterial property of the evaluation material by the "measurement result of the number of bacteria".

Table 2 shows the evaluation results of the antibacterial properties.

[0032]

[Table 2]

As is evident from the results shown in Tables 1 and 2, as shown in FIG.
It can be seen that 10 or more Cu-containing ferritic stainless steel hot-rolled steel sheets (test numbers 1 to 4) precipitated per 0 μm ² exhibit excellent antibacterial properties without variation depending on the sampling position. On the other hand, the “size” and “precipitation number”
The antimicrobial effect of the Cu-containing ferritic stainless steel hot-rolled steel sheets (Test Nos. 5 and 6) lacking in the above-mentioned Test Nos.
It was confirmed that the Cu-containing ferritic stainless steel hot-rolled steel sheet (Test No. 7) with a small number of precipitates, even if the size of the precipitated Cu was 0.05 μm or more, was antibacterial depending on the sampling position. Variation was observed.

Example 2 C: 0.007%, Si: 0.2%, Mn:
Contains 0.2%, Cr: 20%, Ni: 0.3%, N: 0.009%, Cu: 1.8%, with the balance being Fe and unavoidable impurities
Cu-containing ferritic stainless steel is melted by vacuum melting, and the obtained ingot is subjected to hot forging and machining to obtain 40
A hot-rolled steel sheet having a thickness of 140 mm, a width of 140 mm and a length of 85 mm was manufactured and then hot-rolled to obtain a hot-rolled steel sheet (hot-rolled steel strip) having a thickness of 4.5 mm. Next, the obtained hot-rolled steel sheets were subjected to box annealing at a temperature range of 500 to 980 ° C. for 3 hours.
Softening annealing for 0 minutes to 20 hours (combined with Cu precipitation treatment)
, A pickling treatment is performed for the purpose of removing the surface oxidation scale, and then a cold-rolled steel sheet having a thickness of 1.0 mm is formed by cold rolling. Subsequently, a recrystallization annealing treatment is performed in a temperature range of 880 to 980 ° C. And used as test materials. The recrystallization annealing treatment was carried out in two types: a continuous annealing pickling system in which the surface scale was removed by pickling after annealing, and a bright annealing system.

Then, a thin film test piece was collected from each test material in the same manner as in Example 1, and the deposition state of Cu was confirmed with a transmission electron microscope. Table 3 shows the Cu deposition status under each condition.

[0036]

[Table 3]

The results shown in Table 3 indicate that the Cu or ferritic stainless steel cold-rolled steel sheets (test numbers 8 to 14) manufactured under the conditions according to the present invention had a diameter or length of 0.05 μm.
Cu-containing ferritic stainless steel with a softening temperature lower than 750 ° C, corresponding to Cu precipitation treatment, while having a structure in which 10 or more precipitated Cu particles are dispersed at a rate of 10 or more per 100 μm ² Cold rolled steel sheet (test numbers 16 and 2
0) or C with softening time shorter than 1 hour
u-containing ferritic stainless steel cold-rolled steel sheet (Test No. 15
And 17) confirm that the size of precipitated Cu at the product stage is smaller than 0.05 μm. Further, even if the softening treatment conditions corresponding to the Cu precipitation treatment were appropriate, the recrystallization annealing temperature after cold rolling was higher than 950 ° C., and the Cu-containing ferritic stainless steel cold-rolled steel sheets (test numbers 18 and 19) Is the precipitated Cu
It turns out that the number of is insufficient.

Then, in order to confirm the antibacterial performance of each of these test materials, one in a state where the recrystallization annealing has been performed and ^one _quarter of the plate thickness by surface grinding were exposed.
Two of the polished ones were tested as antibacterial evaluation materials. The antibacterial performance of these evaluation materials was evaluated in the same manner as in Example 1, and the results are shown in Table 4.

[0039]

[Table 4]

As is evident from the results shown in Tables 3 and 4, as shown in FIG.
It can be seen that 10 or more Cu-containing ferritic stainless steel cold-rolled steel sheets (test numbers 8 to 14) precipitated per 0 μm ² show excellent antibacterial properties without variation depending on the sampling position. On the other hand, Cu-containing ferritic stainless steel cold-rolled steel sheets with small “size” of precipitated Cu (test numbers 15 to 17)
And 20) show no antibacterial activity, and the cold-rolled Cu-containing ferritic stainless steel sheet (Test Nos. 18 and 19), in which the number of precipitated Cu is insufficient, shows variations in the antibacterial properties depending on the sampling position.

Example 3 C: 0.007%, Si: 0.2%, Mn:
Contains 0.2%, Cr: 20%, Ni: 0.3%, N: 0.009%, Cu: 1.8%, with the balance being Fe and unavoidable impurities
Cu-containing ferritic stainless steel is melted by vacuum melting, and the obtained ingot is subjected to hot forging and machining to obtain 40
A hot-rolled steel sheet having a thickness of 140 mm, a width of 140 mm and a length of 85 mm was manufactured and then hot-rolled to obtain a hot-rolled steel sheet (hot-rolled steel strip) having a thickness of 4.5 mm. Next, 9 was added to the obtained hot-rolled steel sheets.
After soft annealing at 80 ° C for 30 minutes, the surface oxidation scale
Cold-rolled steel sheet having a thickness of 1.5 mm is subjected to pickling treatment for the purpose of removing steel, and then cold-rolled into a cold-rolled steel sheet having a thickness of 1.5 mm. After that, a pickling treatment was again performed for the purpose of removing the surface oxidation scale. Then, it was further cold-rolled into a cold-rolled steel sheet having a thickness of 0.6 mm.
The test material was subjected to a recrystallization annealing treatment in a temperature range of 80 to 980 ° C. Here, as in Example 2, the recrystallization annealing was performed in two types: a continuous annealing pickling method and a bright annealing method.

Then, for each of the test materials, a “confirmation of Cu deposition state” and an “antibacterial evaluation test” were performed under the same conditions as in Example 2. Table 5 shows the Cu deposition status under each condition, and Table 6 shows the antibacterial evaluation results of these materials.

[0043]

[Table 5]

[0044]

[Table 6]

From the results shown in Tables 5 and 6,
As in the case of Example 2, according to the prescribed conditions (Cu precipitation treatment conditions and recrystallization treatment temperature) of the present invention, “diameter or length 0.05
A Cu-containing ferritic stainless steel cold-rolled steel sheet having 10 μm or more of precipitated Cu per 100 μm ² ”is obtained, and the obtained cold-rolled steel sheets have excellent antibacterial properties without variation depending on the sampling position. On the other hand, if the production conditions of the cold-rolled steel sheet deviate from the prescribed conditions of the present invention, a desired Cu precipitation structure cannot be obtained, and it can be confirmed that satisfactory antibacterial performance cannot be stably secured.

[0046]

[Summary of effects] As described above, according to the present invention, even if various kinds of processing such as plastic working and surface polishing are performed, the antibacterial performance is stable and excellent for a long time without special treatment. Thus, it is possible to provide a Cu-containing ferritic stainless steel sheet which exhibits industrially useful effects such as a great contribution in various fields where importance is placed on environmental pollution or hygiene.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph in which the investigation results of "the relationship between the size and the number of precipitated Cu and the antibacterial performance in a Cu-containing ferritic stainless steel sheet" are arranged.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroyuki Miyamoto 4-33, Kitahama, Chuo-ku, Osaka City, Osaka Prefecture Within Sumitomo Metal Industries, Ltd. (56) References JP-A-9-170053 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 38/00-38/60

Claims (4)

(57) [Claims] 1. A structure in which Cu precipitates having a size of 0.05 μm or more are dispersed at a rate of 10 or more per 100 μm ^{2 in} cross section.
(However , the Cu-rich phase precipitates at a rate of 0.2%
A ferrite stainless steel sheet containing Cu. 2. When hot rolling a Cu-containing ferritic stainless steel to produce a sheet material, the steel sheet is softened and annealed after hot-rolled steel strip.
Softened after hot rolling when it is pickled as it is as a product
Annealing and wherein the score facilities prolonged annealing of one hour or more in a temperature range of 750 to 900 ° C. As a dimensions than 0.05μm
Of Cu precipitates of 10 or more per 100 μm ^{2 in} cross section
A method for producing a Cu-containing ferritic stainless steel sheet having a structure dispersed in combination . 3. When a sheet material is manufactured by rolling a Cu-containing ferritic stainless steel, a long-time annealing of 1 hour or more is performed in a temperature range of 750 to 900 ° C. between hot rolling and final cold rolling. The process is characterized by securing dimensions.
Cu precipitates is 05μm or section 100 [mu] m ² per 10
A method for producing a Cu-containing ferritic stainless steel sheet having a structure dispersed in a proportion of at least two pieces . 4. When a sheet material is produced by rolling a Cu-containing ferritic stainless steel, a long-time annealing of 1 hour or more is performed in a temperature range of 750 to 900 ° C. between hot rolling and final cold rolling. Cu precipitates having a size of 0.05 μm or more and having a cross section of 100 μm , characterized by performing the recrystallization annealing after the final cold rolling in a temperature range of 950 ° C. or less while securing the process.
Having a structure dispersed at a rate of 10 or more per m ²
A method for producing Cu-containing ferritic stainless steel sheets.