JPH10306352A - Ferritic stainless steel sheet excellent in antibacterial characteristic and surface characteristic and having high workability, and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferritic stainless steel sheet excellent in surface characteristic as well as in antibacterial characteristic and having high workability, and its production. SOLUTION: This steel sheet has a composition consisting of, by weight, <=0.03% C, 0.1-2.0% Si, <=2.0% Mn, 0.01-0.10% P, <=0.005% S, 10-40% Cr, 1.0-5.0% Cu, <=0.01% O, <=0.03% N, 0.005-1.0%, in total, of one or >=2 elements selected from Nb, Ti, V, Ta, Hf, and Zr, and the balance Fe with inevitable impurities. Further, the amount of precipitation of Cu is regulated to >=0.030% by weight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferritic stainless steel sheet which imparts an antibacterial effect to a pressed product and has good surface properties and workability as a press material, and a method for producing the same.

[0002]

2. Description of the Related Art Ferritic stainless steel sheets have been widely used in kitchen appliances centered on sinks and household electric appliances such as microwave oven side panels, but recently, hand-washing bats have been used in terms of cleanliness, design, and aesthetics. It has also been used for medical equipment such as, and interior building materials such as handrails. That is, the use of stainless steel sheets in places where germs are likely to occur or where germs are not preferable is increasing. Therefore,
There is an increasing tendency to be concerned about the adverse effects on the human body due to the propagation of such germs. In particular, there is a strong demand for antibacterial properties for medical equipment and kitchen equipment that require cleanliness, and building materials for buildings where many people gather.

To meet such needs, Japanese Patent Laid-Open No.
According to JP-A-28202, JP-A-6-10191 and the like, a method of coating and laminating a resin containing an antibacterial agent on the surface of stainless steel, a method of plating an antibacterial component in a matrix, and the like are known.

[0004] However, when a resin containing an antibacterial agent is applied to the surface, the surface gloss peculiar to stainless steel is lost. In addition, the antibacterial resin film is easily damaged by cracking or chipping during press working or use, and when exposed to a humid atmosphere, the antibacterial components elute and not only deteriorate the appearance, but also Loses its antibacterial action. The same is true for plating containing antimicrobial agents.

Further, ferritic stainless steel sheets used for kitchen appliances and home electric appliances are often manufactured by deep drawing, so that the critical drawing ratio needs to be as high as 2.5 or more. Also, good ridging resistance is required.

[0006]

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a highly workable stainless steel sheet having excellent antibacterial properties and surface properties.

[0007]

The gist of the present invention is as follows. (1) In terms of% by weight, C ≦ 0.03%, Si: 0.1 to
2.0%, Mn ≦ 2.0%, P: 0.01 to 0.10
%, S ≦ 0.005%, Cr: 10 to 40%, Cu:
1.0-5.0%, O ≦ 0.01%, N ≦ 0.03%,
And 1 selected from Nb, Ti, V, Ta, Hf, Zr
A total of 0.005 to 1.0% of a species or two or more species, the balance being Fe and unavoidable impurities, and a Cu precipitation amount of 0.030% or more by weight. Highly workable ferritic stainless steel sheet with excellent antibacterial properties and surface properties.

(2) As an alloy component, the weight%
And one or two selected from B and Be are added in a total of 0.0
The high workability ferritic stainless steel sheet having excellent antibacterial properties and surface properties according to the above (1), which contains 005 to 0.05%.

(3) As an alloy component, further,
And a high workability ferritic stainless steel sheet having excellent antibacterial properties and surface properties according to the above (1) or (2), characterized by containing Mo: 0.1 to 5.0%.

(4) When hot rolling a ferritic stainless steel slab containing the components described in (1), (2) or (3) above, the heating temperature is set to 1100 to 1300 ° C. and rough rolling is performed. After finishing, the final rolling temperature in finish rolling is set to 900 ° C. or higher, and after winding, 300 to 800 ° C.
A method for producing a high-workability ferritic stainless steel sheet having excellent antibacterial properties and surface properties, which is characterized by performing cold rolling and annealing after the heat treatment described above.

(5) When hot rolling a ferritic stainless steel slab containing the components described in (1), (2) or (3) above, the heating temperature is set to 1100 to 1300 ° C. and rough rolling is performed. After finishing the final rolling temperature in finish rolling is less than 900 ° C., after winding, subjected to hot-rolled sheet annealing, and subsequently subjected to heat treatment at 300 to 800 ° C., then subjected to cold rolling, annealing Of high workability ferritic stainless steel sheet with excellent antibacterial properties and surface properties.

(6) The steel sheet after cold rolling or annealing
After performing a solution treatment at a temperature exceeding 0 ° C. to 1050 ° C., quenching is performed,
The method for producing a highly workable ferritic stainless steel sheet having excellent antibacterial properties and surface properties according to the above (4) or (5), wherein the aging treatment is performed at 300 to 800 ° C.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the reasons for limiting the alloy of the present invention will be described in detail. When C is 0.030% or less, the formability is remarkably improved, and it is possible to perform severe deep drawing, which is one of the objects of the present invention and requires a critical drawing ratio of 2.5 or more. Therefore, the C content is set to 0.030% or less. Furthermore, in order to improve ductility, less than 0.005% is desirable.

Si acts as a deoxidizing element and improves high-temperature oxidation resistance. However, if added in a large amount, it hardens and deteriorates ductility. Therefore, the Si content is set to 2.0% or less. Desirably, 1.0% or less is good. Further, Cu added to improve the antibacterial property of the steel of the present invention easily forms a Cu-enriched layer immediately below the scale during heating before hot working, but when the Si content is 0.1% or more, the Cu-enriched layer is formed. Since the effect of suppressing the oxide layer is recognized, the Si content is desirably set to 0.1% or more.

Mn is necessary to prevent grain boundary embrittlement due to segregation of the deoxidizing agent and S at the crystal grain boundaries, but too much Mn reduces the cold workability of the steel sheet. Therefore, Mn
The content was 2.0% or less.

P is a grain boundary segregation element, and if contained in an excessively large amount, it deteriorates the cold workability and toughness of the steel sheet. Also,
Cu added to improve the antibacterial properties of the steel of the present invention,
During heating before hot working, it is easy to form a Cu-enriched layer directly below the scale, which lowers the critical rupture stress at the grain boundaries and causes surface defects as barbs after hot working. .0
When the content exceeds 1%, the critical rupture stress at the grain boundary is increased to suppress the generation of barbs. Therefore, the range of the P content is set to 0.01 to 0.10%. Further, preferably 0.0
3-0.07% is good.

S is an element that deteriorates corrosion resistance and formability, and is set to 0.005% or less.

Cr is required to be added in an amount of 10% or more to improve corrosion resistance and high-temperature oxidation resistance, and if it exceeds 40%, formability is deteriorated. Furthermore, from the viewpoint of ensuring corrosion resistance and moldability, it is 15 to 25.
% Is desirable.

Cu is the most important element for improving the antibacterial property in the steel of the present invention, and its effect is 1.0%
The above is demonstrated. However, if the content is too large, the slab will crack, so the content was set to 5.0% or less.

O increases the amount of inclusions in the steel as the content increases, thereby deteriorating corrosion resistance and workability.
It was as follows.

N increases the content, so that the moldability deteriorates. Therefore, the content of N is set to 0.03% or less. Furthermore, 0.01% or less is desirable from the viewpoint of ensuring corrosion resistance.

Nb, Ti, V, Ta, Hf, and Zr are elements for improving the formability because they are carbonitride forming elements. If one or more of them is less than 0.005% in total, they are not effective. The effect is small, and if added over 1.0%, the toughness is impaired, so that Nb, Ti, V, Ta, Hf,
The range in which one or more of Zr is added is 0.0
05 to 1.0%. More preferably, 0.05 to
0.7% is good. In addition, when adding one kind alone,
0.1-0.5% is good.

B and Be are elements that improve the secondary formability after deep drawing. If less than 0.0005%, the effect is small. Deterioration of cold workability. Therefore, B, Be
The range in which one or two of them are added is 0.0005 to
0.05%. More preferably, 0.0010
0.01% is good.

Mo is an element which improves corrosion resistance and is 0.1%.
% Or more is required, and if it exceeds 5.0%, the toughness deteriorates. Therefore, the content is set in the range of 0.1 to 5.0%. Furthermore, from the viewpoint of ensuring pitting corrosion resistance and formability, 0.5 to 3.0%
Is desirable.

The present inventors have found that the antimicrobial effect of E. coli and staphylococci on ferritic stainless steel sheet and C
Various conditions for the existence of u were examined. The result is shown in FIG.
Here, the antibacterial property was evaluated by the sterilization rank, and the sterilization rate was 0.9.
9 or more: 、, 0.95 or more and less than 0.99, ○: 0.60
Above less than 0.95 was indicated as Δ, and less than 0.60 was indicated as x. The pass of the antibacterial property was evaluated as ○ or more. The Cu precipitate was obtained by performing electrolytic extraction using an acetylacetone-based non-aqueous solvent solution. From FIG. 1, it can be seen that when the Cu deposition amount is 0.030% or more, there is an antibacterial effect. Therefore, the amount of Cu deposition on the product plate was set to 0.030% or more.

In addition, the ridging generated by press working on a ferritic stainless steel sheet is caused by the {100} expanded grain formed at the center of the sheet thickness of the material before cold rolling, in which the recrystallization orientation is close even after cold rolling sheet annealing ( Colonies),
It is said to occur. Therefore, in order to improve the ridging resistance of the product sheet, it is desirable that the X-ray integrated intensity ratio of the {100} plane at the center of the sheet thickness of the material before cold rolling be 7.0 or less. The heat treatment time is required to be one hour or more, and desirably five hours or more in order to sufficiently precipitate Cu.

Next, the reason for defining the hot rolling conditions will be described. If the slab heating temperature is lower than 1100 ° C., a surface defect due to roll seizure, which has been a problem in the past, occurs. On the other hand, if the temperature exceeds 1300 ° C., the crystal grain size becomes coarse, so that linear barbed flaws are frequently generated during hot rolling and energy costs are increased. Therefore, the slab heating temperature was set to 1100 to 1300 ° C.

Regarding the hot-rolling finishing temperature, when performing hot-rolled sheet annealing, by setting the temperature to less than 900 ° C., strain is accumulated, recrystallization by hot-rolled sheet annealing is promoted, and the sheet thickness of the material before cold rolling is reduced. The X-ray integrated intensity ratio of the central {100} plane is 7.0 or less. On the other hand, when the hot-rolled sheet annealing is omitted, it has been found that promoting partial recrystallization by high-temperature finishing improves the ridging resistance of the product.
By doing so, the thickness of the material before cold rolling is reduced to
The X-ray integrated intensity ratio of the 0 ° plane becomes 7.0 or less.

With regard to the aging treatment after hot rolling or hot-rolled sheet annealing, C
In order to deposit u effectively, it is necessary for Cu to diffuse in the matrix, and at a temperature lower than 300 ° C., diffusion is insufficient. On the other hand, when the temperature exceeds 800 ° C., the precipitation of Cu from the matrix becomes insufficient. Therefore, the aging temperature was set to 300 to 800 ° C. Furthermore, 550-750 degreeC is desirable for improvement of diffusion and precipitation. The processing may be performed in two or more steps, or the processing may be performed in two or more steps as long as the temperature is within the above range.

The cold rolling and the annealing after the cold rolling are performed in a usual range applied to the ferritic stainless steel.
After annealing, temper rolling is performed as necessary.

Next, the reasons for limiting the solution treatment conditions and the aging treatment conditions will be described. In order to more effectively exert the antibacterial property of Cu, it is necessary to further precipitate Cu, and therefore, a solution treatment and an aging treatment as a subsequent treatment are important.

With respect to the solution treatment, Cu is used during the aging treatment.
In order to effectively precipitate Cu, it is necessary to form a solid solution of Cu in the matrix, and at a temperature of 800 ° C. or less, the effect is not sufficient. On the other hand, if it exceeds 1050 ° C., the crystal grain size becomes coarse and the surface properties after processing deteriorate. Therefore, the solution treatment temperature was set to more than 800 to 1,050 ° C.

Regarding the aging treatment, it is necessary to diffuse Cu in the matrix in order to effectively precipitate Cu dissolved in the matrix.
At temperatures below ℃ the diffusion is insufficient. On the other hand, 800 ° C
When Cu exceeds 3, the precipitation of Cu from the matrix becomes insufficient. Therefore, the aging temperature was set to 300 to 800 ° C. The processing may be performed in two or more steps, or the processing may be performed in two or more steps as long as the temperature is within the above range.

[0034]

Next, the present invention will be specifically described with reference to examples. Tables 1 and 2 show examples of the present invention and comparative examples.
Tables 1 and 2 show the components, hot rolling conditions, cold rolling conditions, final annealing conditions, solution treatment conditions and aging treatment conditions, and evaluation results of manufacturability, antibacterial properties, surface properties and workability. Is shown.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

[0039]

[Table 5]

[0040]

[Table 6]

The alloy of the present invention and the comparative alloy were prepared by using a flat melting ingot (70 mm thick × 300 mm width × 4 mm) using a vacuum melting furnace.
(00 mm length). The ingot was subjected to hot rolling, cold rolling and heat treatment in a laboratory to prepare a sample for evaluation.

As for the manufacturability, scabs during hot rolling and cracks during cold rolling were evaluated. The scorching was evaluated by removing the scale on the surface of the hot-rolled plate by pickling with nitric acid and hydrofluoric acid, and then ranking the scorching status with “○” or “×”. ○ indicates a depth of 30μ per side
m is a flaw level that can be removed by surface grinding, and x is a level that cannot be removed by the grinding. The evaluation of cracks
When cold rolling was performed at room temperature, the test was performed depending on the condition of edge cracks and breakage.は indicates that no cracks occurred, and X indicates that ear cracks or breaks occurred.

The evaluation of antibacterial properties is in accordance with the antibacterial evaluation test method for antibacterial processed products of the Research Group for Inorganic Antibacterial Agents such as Silver. As test bacteria, Staphylococcus aureus IFO 12732 (Staphylococcus aureus) and Escherichia coli ATCC 8739 (Escherichia coli) were used. The test bacterium was cultured on a TrypticaseSoy Agar (BBL) agar plate medium at 35 ° C. for 18 to 24 hours, and the grown colonies were grown for 1 hour.
Suspended in a normal broth medium with a concentration of about 10 ⁸ CF
Adjust to U / ml. A test piece of 5 × 5 cm is collected from the product plate manufactured as described above, and 0.5 ml of the test bacterium suspension is uniformly brought into contact with the surface. A polyethylene film of the same size as the test piece was placed on the
Operate at 5% at a temperature of 36 ° C for 24 hours.

After the action for a predetermined time, the bacteria are wiped off in a sterilization booth and 10 ml of SCDL broth is added to shake out the adherent bacteria. A dilution example is prepared by using the shake-out solution as a stock solution, and a mixed plate with an agar medium is formed. The number of colonies after culturing is measured. In addition, the same operation is performed using a sterilized petri dish to make the test object. The evaluation was calculated by ((number of generated communities of test object) / (number of generated communities of test piece).
5 or more and less than 0.99, △ is 0.60 or more and less than 0.95,
X was less than 0.60. The pass was evaluated as ○ or more.

For evaluation of lysine gland as a surface property, a JIS No. 5 tensile test piece was prepared, and the surface of the test piece which had been subjected to 15% strain as a strain using a tensile tester was measured for ridging height with a surface roughness meter. The results were ranked. A has a ridging height of 10 μm or less, B has a thickness of 20 μm or less, C has a thickness of 30 μm or less, and C has a thickness of more than 30 μm.

For the workability, the critical draw ratio and the temperature at which cracking occurred during the secondary working were evaluated. The limit drawing ratio was measured by blanking a disc-shaped blank having a diameter of 60 mm to 120 mm from the product plate manufactured above and using a drawing tester having a punch having a diameter of 40 mm by cylindrical drawing. The limit drawing ratio used was the value obtained by dividing the maximum blank diameter drawn by the punch diameter. The cracking temperature at the time of the secondary processing was as follows: a blank having a diameter of 100 mm was blanked, a cylinder was drawn with a punch having a diameter of 40 mm, and a cylinder squeezed out was used.
The temperature at which a vertical crack occurred on the side wall of the cylinder when the weight was dropped from a height of 00 mm was measured.

The alloy of the present invention is good against scabs and cracks during production, and has reached the acceptable rank in antibacterial properties, surface properties and workability. On the other hand, in the comparative alloy,
21,23,24,26,27,29,32,33,3
5 are C, Si, Mn, P, S, Cr, O, N,
Since the carbonitride forming element such as Nb is out of the range of the present invention, the critical draw ratio is less than 2.5, and the formability is deteriorated. No. Since Si and P are out of the range of the present invention in Nos. 22 and 25, scorching occurs due to the Cu layer concentrated immediately below the scale during heating before hot rolling. N
o. In Nos. 27 and 28, since S and Cr are out of the range of the present invention, rust in the product is remarkable and corrosion resistance is deteriorated. No. In the sample No. 30, the amount of Cu precipitated in the extraction residue in the product was 0.00
It is as low as 6%, the sterilization rate of the product is low, and the antibacterial property is deteriorated. No. 31, 34, 36 and 42 are each C
Since u, Nb + Ti + V + Ta + Hf + Zr, and Mo are out of the range of the present invention, edge cracks and fractures occur during cold rolling. No. Nos. 37, 38 and 41 have final rolling temperatures outside the range of the present invention, and the ridging characteristics after processing of the product have deteriorated. No. In 39 and 40, since the heating temperature before the hot rolling is out of the range of the present invention, barge caused by seizure by a roll and barge caused by a coarse structure are generated. No. In 43, 44, 45 and 46, since the solution heat treatment temperature and the aging treatment temperature are out of the range of the present invention, the re-solid solution of Cu occurs or the precipitation of Cu is insufficient, and the antibacterial property is low. Not good.

[0048]

As is apparent from the above, according to the present invention, a high-workability ferritic stainless steel sheet having excellent antibacterial properties and surface properties can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of Cu deposited and the sterilization rank.

Claims (6)

[Claims] 1. wt%, C ≦ 0.03%, Si: 0.1-2.0%, Mn ≦ 2.0%, P: 0.01-0.10%, S ≦ 0.005 %, Cr: 10 to 40%, Cu: 1.0 to 5.0%, O ≦ 0.01%, N ≦ 0.03%, and Nb, Ti, V, Ta, Hf,
One or more selected from Zr is 0.005 in total.
~ 1.0%, the balance being Fe and unavoidable impurities, and the precipitation amount of Cu was 0.030% by weight%.
A highly workable ferritic stainless steel sheet having excellent antibacterial properties and surface properties, characterized in that: 2. As an alloy component, B,
One or two selected from Be in total of 0.0005 to
The highly workable ferritic stainless steel sheet having excellent antibacterial properties and surface properties according to claim 1, containing 0.05%. 3. The alloy composition further comprises:
3. The highly workable ferritic stainless steel sheet having excellent antibacterial properties and surface properties according to claim 1 or 2, which contains 0.1 to 5.0% of o. 4. A hot rolling of a ferritic stainless steel slab containing the component according to claim 1, 2 or 3, a heating temperature of 1100 to 1300 ° C., a rough rolling, and a final rolling in finish rolling. High workability ferritic stainless steel with excellent antibacterial properties and surface properties characterized by rolling at a temperature of 900 ° C or higher, winding, heat-treating at 300 to 800 ° C, and then performing cold rolling and annealing. Steel plate manufacturing method. 5. A hot rolling of a ferritic stainless steel slab containing the components according to claim 1, 2 or 3 at a heating temperature of 1100 ° C. to 1300 ° C. The rolling temperature was set to less than 900 ° C., and after winding, hot-rolled sheet annealing was performed.
A method for producing a high-workability ferritic stainless steel sheet having excellent antibacterial properties and surface properties, comprising performing a heat treatment at -800 ° C, followed by cold rolling and annealing. 6. A steel sheet after cold rolling or annealing is subjected to a solution treatment at a temperature exceeding 800 ° C. to 1050 ° C., and then quenched.
The aging treatment is performed at a temperature of up to 800 ° C.
Or a method for producing a highly workable ferritic stainless steel sheet having excellent antibacterial properties and surface properties according to item 5.