JP4541089B2 - Ferritic stainless steel welding wire with excellent antibacterial properties - Google Patents

Description

  The present invention relates to a welding wire that imparts an effect of suppressing the propagation of pathogenic bacteria (hereinafter referred to as antibacterial) to a weld metal when welding ferritic stainless steel materials, low alloy steel materials, and various steel materials such as carbon steel materials. is there.

  The ferritic stainless steel welding wire of the present invention is used in fields in which antibacterial properties are required in addition to corrosion resistance for weld metals of ferritic stainless steel materials (for example, kitchens, medical treatment, food processing, underground buried pipes, water storage tanks, water heaters, Applicable to various pipes). Moreover, when build-up welding of a low alloy steel material or a carbon steel material is performed using the ferritic stainless steel welding wire of the present invention, it can be used as an antibacterial clad material having corrosion resistance.

  It has been conventionally known that Ag has an effect of suppressing the growth of pathogenic bacteria represented by Escherichia coli and Salmonella and preventing food poisoning caused by the pathogenic bacteria. The effect of inhibiting the growth of pathogenic bacteria (ie, antibacterial) is attributed to the damage of Ag ions to pathogenic bacteria, and Ag ions are also more effective than Cu ions, which also have antibacterial properties. Has been shown to exert significant effects. Thus, various techniques for providing antibacterial properties in addition to the corrosion resistance of general stainless steel by depositing Ag in and / or on the surface of stainless steel have been proposed.

For example, Patent Document 1 and Patent Document 2 disclose a stainless steel plate containing 0.0005 to 0.30 mass% of Ag. These stainless steel plates have excellent corrosion resistance and antibacterial properties. However, when these stainless steel plates are welded in the course of manufacturing a stainless steel product, the antibacterial properties are lowered at the welds. This is because the conventional stainless steel welding wire has a component design that can maintain the corrosion resistance of the weld metal at the same level as the base metal (ie, stainless steel plate), but the antibacterial properties of the weld metal are not taken into consideration. It is impossible to impart the same antibacterial properties to the weld metal.
JP 11-12692 A Japanese Patent Laid-Open No. 11-158585

  An object of the present invention is to provide a ferritic stainless steel welding wire capable of providing antibacterial and corrosion resistance to a weld metal when welding a ferritic stainless steel material, a low alloy steel material, or a carbon steel material. And

  In order to develop a ferritic stainless steel welding wire for obtaining a weld metal with excellent antibacterial and corrosion resistance, the present inventors have conducted intensive research on a technology that utilizes Ag that has excellent antibacterial properties and high safety to the human body. Piled up. As a result, it was found that, by specifying the components of the ferritic stainless steel welding wire within a suitable range and adding Ag, the corrosion resistance of the weld metal is increased and Ag is concentrated on the surface layer of the weld metal.

  If Ag concentrates on the surface of the weld metal, the antibacterial properties of the weld metal can be ensured. The present invention has been made based on such knowledge.

  That is, the present invention includes C: 0.0010 to 0.150 mass%, Si: 0.20 to 1.0 mass%, Mn: 0.20 to 2.5 mass%, P: 0.010 to 0.030 mass%, S: 0.00010 to 0.020 mass%, Al: 0.00050 to 0.30. It is a ferritic stainless steel welding wire having a composition comprising: mass%, Cr: 10 to 30 mass%, N: 0.005 to 0.40 mass%, Ag: 0.010 to 1.0 mass%, and the balance consisting of Fe and inevitable impurities.

  In addition to the composition described above, the ferritic stainless steel welding wire of the present invention includes one or more of Mo: 0.01 to 6.0 mass%, Cu: 0.01 to 2.5 mass%, and W: 0.01 to 0.30 mass%. It is preferable to contain. Further, Nb: 0.01 to 2.0 mass%, Ti: 0.01 to 1.0 mass%, Zr: 0.001 to 1.0 mass%, Ta: 0.01 to 2.0 mass%, and B: 0.0001 to 0.0050 mass% It is preferable to contain.

  If a ferritic stainless steel material having antibacterial properties is welded using a ferritic stainless steel welding wire (hereinafter referred to as an antibacterial welding wire) excellent in antibacterial properties of the present invention, it is equivalent to the ferritic stainless steel material of the base material. Antibacterial and corrosion resistance can be imparted to weld metal.

  In addition, by using the antibacterial welding wire of the present invention, the cladding material having antibacterial properties and corrosion resistance by performing build-up welding of low alloy steel materials, carbon steel materials, or ordinary ferritic stainless steel materials not imparted with antibacterial properties Can be used as

  Furthermore, when the antibacterial welding wire of the present invention is used to construct a pipe in which ferritic stainless steel pipe, low alloy steel pipe, and carbon steel pipe are welded and connected, a welded joint made of a weld metal having antibacterial properties can be formed. The cutting and polishing of the weld metal is not required, and the adhesion of microorganisms can be suppressed in the welded state. When pipes are constructed using conventional stainless steel welding wires, the fluid flowing in the pipes is retained by macro unevenness of the weld metal, and microorganisms floating in the fluid easily adhere to and propagate on the weld metal. It was. Therefore, conventionally, in order to prevent the adhesion of microorganisms, it has been necessary to cut and polish the weld metal (especially the inner side of the pipe) to obtain a smooth surface. On the other hand, when the antibacterial welding wire of the present invention is used, although there is a macro unevenness of the weld metal, the weld metal has antibacterial properties, so that the growth of microorganisms can be suppressed.

  As explained above, the antibacterial welding wire of the present invention exhibits a great and remarkable effect.

  Generally, welding wires are roughly classified into solid wires and flux cored wires. The solid wire is a welding wire made of a carbon steel wire or a stainless steel wire, and there is a wire in which the surface of the wire is plated or a lubricant is applied. The flux cored wire is a welding wire in which a welding flux is filled inside a carbon steel outer shell or a stainless steel outer shell.

  The ferritic stainless steel welding wire (that is, the antibacterial welding wire) excellent in antibacterial property of the present invention is a solid wire among welding wires roughly classified into a solid wire and a flux cored wire.

  The reason which limited the component of the antibacterial welding wire of this invention is demonstrated.

C: 0.0010 to 0.150 mass%
C is a solid solution strengthened element and needs to be contained in an amount of 0.0010% by mass or more in order to increase the strength of the weld metal. However, if it exceeds 0.150% by mass, it combines with Cr, which will be described later, to produce Cr carbide in the weld metal, resulting in reduced corrosion resistance. Therefore, C needs to satisfy the range of 0.0010 to 0.150 mass%.

Si: 0.20 to 1.0 mass%
Si increases the oxidation resistance and is therefore an effective element for improving the corrosion resistance of the weld metal. Also, since it has an effect of improving the fluidity of the molten metal, a smooth bead shape can be obtained by adding Si, which is effective in improving the welding workability. In order to exhibit this effect, it is necessary to contain 0.20 mass% or more. However, if the content exceeds 1.0% by mass, not only the high temperature cracking susceptibility of the weld metal is increased (that is, high temperature cracking is likely to occur), but also wire drawing due to a decrease in the cold workability of the antibacterial welding wire. Productivity is reduced. Therefore, Si needs to satisfy the range of 0.20 to 1.0 mass%.

Mn: 0.20 to 2.5 mass%
Mn has a deoxidizing action and a desulfurizing action, and has the effect of fixing S that causes weld cracking and lowering the hot cracking susceptibility of the weld metal (that is, hot cracking is less likely to occur). In order to exhibit this effect, it is necessary to contain 0.20 mass% or more. However, if the content exceeds 2.5% by mass, the fluidity of the molten metal is deteriorated and the welding workability is lowered. Moreover, the productivity of wire drawing decreases due to the decrease in cold workability of the antibacterial welding wire. Therefore, Mn needs to satisfy the range of 0.20 to 2.5% by mass.

P: 0.010 to 0.030 mass%
P is an element that enhances the hot cracking susceptibility of the weld metal, so it needs to be reduced as much as possible. When the P content exceeds 0.030% by mass, the hot cracking susceptibility increases remarkably, so the content was made 0.030% by mass or less. However, in order to reduce P to less than 0.010% by mass, a large amount of refining time is required at the melting stage of ferritic stainless steel, which is the material of the antibacterial welding wire. Invite. Therefore, P needs to satisfy the range of 0.010-0.030 mass%.

S: 0.00010 to 0.020 mass%
S is an element that is easily segregated at the crystal grain boundaries of the weld metal and promotes intergranular embrittlement to increase the hot cracking susceptibility. Moreover, since the cold workability at the time of manufacturing an antibacterial welding wire is lowered, the productivity of the wire drawing process is lowered. Therefore, S needs to be reduced as much as possible. However, in order to reduce the S content to less than 0.00010% by mass, a great amount of refining time is required at the melting stage of ferritic stainless steel, which is the material of the antibacterial welding wire. Invite rise. On the other hand, when S exceeds 0.020% by mass, the hot cracking sensitivity is remarkably increased. Therefore, S needs to satisfy the range of 0.00010-0.020 mass%.

Al: 0.00050 to 0.30 mass%
Since Al is an element effective for deoxidation, it needs to be 0.00050% by mass or more. However, excessive addition increases the amount of alumina inclusions, causes frequent surface flaws and lowers workability, and is 0.30% by mass or less. Limited to. Therefore, Al needs to satisfy the range of 0.00050 to 0.30 mass%.

Cr: 10-30% by mass
Cr is an essential element for maintaining the corrosion resistance of the weld metal, and if it is less than 10% by mass, sufficient corrosion resistance cannot be obtained. On the other hand, when it exceeds 30% by mass, an intermetallic compound is easily generated in the weld metal, and the toughness is lowered. Moreover, since the cold workability of the antibacterial welding wire is lowered, the productivity of the wire drawing process is lowered. Therefore, Cr needs to satisfy the range of 10-30 mass%.

N: 0.005-0.40 mass%
N, like C, is a solid solution strengthened element and is an effective element for increasing the strength of the weld metal. In order to acquire the effect, it is necessary to contain 0.005 mass% or more. However, when it contains exceeding 0.40 mass%, the blow hole by N will generate | occur | produce in a weld metal. Therefore, N needs to satisfy the range of 0.005-0.40 mass%.

Ag: 0.010 to 1.0 mass%
Ag is the most important element in the present invention. By adding Ag to the antibacterial welding wire, a concentrated region of Ag is formed on the surface of the weld metal, and the propagation of pathogenic bacteria can be suppressed and the antibacterial property of the weld metal can be enhanced. However, since Ag is an easily oxidizable element, considering the oxidative consumption due to welding, sufficient antibacterial properties cannot be obtained if the Ag content is less than 0.010% by mass. On the other hand, if the content exceeds 1.0% by mass, hot cracking of the weld metal tends to occur. Moreover, even if expensive Ag is added excessively exceeding 1.0 mass%, further improvement in antibacterial properties cannot be expected, which is not preferable from the viewpoint of economy. Therefore, Ag must satisfy the range of 0.010 to 1.0 mass%.

  Furthermore, in the present invention, in addition to the above composition, the antibacterial welding wire preferably contains Mo, Cu, W, Nb, Ti, Zr, Ta, and B.

One or more of Mo: 0.01 to 6.0% by mass, Cu: 0.01 to 2.5% by mass and W: 0.01 to 0.30% by mass
By adding 0.01% by mass or more of Mo, Cu, and W, stress corrosion cracking resistance and pitting corrosion resistance can be improved. Further, in addition to these effects, Cu has an effect of enhancing antibacterial properties together with Ag. W has not only the effect of further increasing the antibacterial property by the combined effect with Ag, but also the effect of increasing the strength of the weld metal as a solid solution strengthened element. However, if Mo, Cu, W is added excessively, the mechanical properties of the weld metal deteriorate. That is, when Mo exceeds 6.0% by mass, an intermetallic compound is easily generated in the weld metal, and the corrosion resistance and toughness are lowered. If Cu exceeds 2.5% by mass, hot cracking of the weld metal tends to occur. When W exceeds 0.30% by mass, the cold workability of the antibacterial welding wire is lowered, so that the productivity of the wire drawing process is lowered. Therefore, when adding Mo, Cu, and W, it is preferable to satisfy the ranges of Mo: 0.01 to 6.0% by mass, Cu: 0.01 to 2.5% by mass, and W: 0.01 to 0.30% by mass.

Nb: 0.01 to 2.0% by mass, Ti: 0.01 to 1.0% by mass, Zr: 0.001 to 1.0% by mass, Ta: 0.01 to 2.0% by mass and B: 0.0001 to 0.0050% by mass or two or more
Since Nb, Ti, Zr, and Ta all have a strong affinity with C and preferentially generate carbides, they have the effect of suppressing grain boundary precipitation of Cr carbides in the weld metal and increasing intergranular corrosion resistance. B has the effect of strengthening the grain boundaries of ferritic stainless steel and enhancing the hot workability of the antibacterial welding wire. These effects are exhibited by adding Nb: 0.01% by mass or more, Ti: 0.01% by mass or more, Zr: 0.001% by mass or more, Ta: 0.01% by mass or more, and B: 0.0001% by mass or more. However, if Nb exceeds 2.0 mass%, the hot cracking susceptibility of the weld metal increases. When Ti exceeds 1.0% by mass, the fluidity of the molten metal is lowered and welding workability is deteriorated. When Zr exceeds 1.0% by mass, the fluidity of the molten metal is lowered and welding workability is deteriorated. When Ta exceeds 2.0 mass%, the hot cracking susceptibility of the weld metal increases. When B exceeds 0.0050 mass%, the hot cracking sensitivity of the weld metal increases. Therefore, when Nb, Ti, Zr, Ta, and B are added, Nb: 0.01 to 2.0% by mass, Ti: 0.01 to 1.0% by mass, Zr: 0.001 to 1.0% by mass, Ta: 0.01 to 2.0% by mass, B: It is preferable to satisfy the range of 0.0001 to 0.0050 mass%.

  Other than the components of the antibacterial welding wire described above, Fe and unavoidable impurities. Impurities that are inevitably mixed at the stage of melting ferritic stainless steel or the stage of manufacturing an antibacterial welding wire are preferably reduced as much as possible.

  In addition, when performing welding using the antibacterial welding wire of the present invention, TIG welding using an inert gas as a shielding gas in order to prevent Ag in the antibacterial welding wire from being oxidized and consumed by welding. Or it is preferable to employ | adopt MIG welding.

  Ferritic stainless steel containing Ag was melted, and hot working and cold working were further performed to produce a ferritic stainless steel welding wire (ie, antibacterial welding wire) having a diameter of 1.2 mm. The components of the obtained antibacterial welding wire are as shown in Tables 1 and 2. Sample Nos. 1 to 26 shown in Table 1 are examples in which the components satisfy the scope of the present invention, and this is an invention example. Sample numbers 27 to 42 shown in Table 2 are examples in which the components are outside the scope of the present invention, and this is used as a comparative example. That is, sample number 27 is an example in which the P content is outside the scope of the present invention, sample numbers 28 to 31, 33, 34, 37, 38, 42 are examples in which the P content and the Ag content are outside the scope of the present invention, Numbers 32, 35, 36, 39 and 41 are examples in which the Ag content is outside the scope of the present invention, and sample number 40 is an example in which the C content, the P content and the Ag content are outside the scope of the present invention.

  Using these antibacterial welding wires, three-layer overlay welding was performed on SUS430 steel plate 1 (thickness 12 mm, width 100 mm, length 150 mm). The welding conditions are as shown in Table 3.

Next, as shown in FIG. 1, an antibacterial test was performed on the surface of the central portion of the weld metal in accordance with JIS standard Z2801. Antibacterial properties were evaluated using the film adhesion method established by the Antibacterial Product Technology Association in accordance with JIS standard Z2801. The procedure of the film adhesion method is as follows.
(1) with absorbent cotton or the like containing 99.5% ethanol, washed, degreased test piece 25 cm ^2.
(2) Disperse E. coli in 1/500 NB solution and adjust the number of E. coli to 2 × 10 ^{6 to} 6 × 10 ⁶ cfu / ml.
(3) Inoculate the test solution (3 pieces each) with the above bacterial solution of (2) at a ratio of 0.5 ml / 2.5 cm ² .
(4) Cover the surface of the weld metal 2 with the covering film 3 and keep it in close contact, and store it for 24 hours at a temperature of 35 ± 1 ° C. and a relative humidity (RH) of 90% or more.
(5) Wash out the inoculated test bacteria.
(6) Measure the viable cell count by agar culture method (temperature: 35 ± 1 ° C, time: 40-48hr).
(7) Calculate the sterilization rate.

  The NB solution is a solution obtained by diluting a Buion medium (NB) 500 times with sterilized purified water. Buion medium refers to a meat extract of 5.0 g, sodium chloride 5.0 g, peptone 10.0 g, purified water 1000 ml, pH 7.0 ± 0.2.

The sterilization rate is a value calculated by the following formula. The number of control bacteria in the formula was the number of viable bacteria after the antibacterial test was performed in a sterile petri dish, and was 9.30 × 10 ⁷ cfu / ml. The number of bacteria after the test refers to the measured number of viable bacteria.

Bacterial sterilization rate (%) = 100 × (bacterial number of control−bacterial number after test) / bacterial number of control The sterilization rate thus obtained is shown in Tables 1 and 2 together. As shown in Table 1, the inventive examples all had a sterilization rate of 99.9%. However, as shown in Table 2, the comparative example was 32.0% or less. Therefore, it was confirmed that a weld metal having excellent antibacterial properties can be obtained by welding using the antibacterial welding wire of the present invention.

In addition, as shown in Table 1, the antibacterial welding wire of the present invention has a component equivalent to that of ordinary ferritic stainless steel, so that it is clear that a weld metal having excellent corrosion resistance can be obtained.

It is a perspective view which shows typically the SUS430 steel plate and weld metal which were used for the antimicrobial test.

Explanation of symbols

1 SUS430 steel plate 2 welded metal 3 coating film

Claims (3)

  C: 0.0010 to 0.150 mass%, Si: 0.20 to 1.0 mass%, Mn: 0.20 to 2.5 mass%, P: 0.010 to 0.030 mass%, S: 0.00010 to 0.020 mass%, Al: 0.00050 to 0.30 mass%, Cr: A ferritic stainless steel welding wire comprising 10 to 30% by mass, N: 0.005 to 0.40% by mass, Ag: 0.010 to 1.0% by mass, the balance being composed of Fe and inevitable impurities.   In addition to the said composition, it contains 1 type (s) or 2 or more types in Mo: 0.01-6.0 mass%, Cu: 0.01-2.5 mass%, and W: 0.01-0.30 mass%. The ferritic stainless steel welding wire as described.   In addition to the above composition, Nb: 0.01 to 2.0 mass%, Ti: 0.01 to 1.0 mass%, Zr: 0.001 to 1.0 mass%, Ta: 0.01 to 2.0 mass%, and B: 0.0001 to 0.0050 mass% Or the ferritic stainless steel welding wire of Claim 1 or 2 containing 2 or more types.

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