JP4512434B2 - Stainless steel welding material - Google Patents

Description

  The present invention relates to a stainless steel welding material and a welding method, and particularly to a stainless steel welding material that is excellent in antibacterial properties and is suitable for use in daily life-related products, medical devices, and building materials.

High Ni—Cr stainless steel is used in many fields including life-related products, and various types of high Ni—Cr stainless steel welding materials for welding such high Ni—Cr stainless steel are also used. Things are being developed. Generally, as a high Ni—Cr stainless steel welding material, a welding material such as JIS standard Y310S is known.
JIS Handbook 40 Welding 2004 (page 912)

  However, in recent years, microbial corrosion has become a major problem as one of the causes of abnormal corrosion of water distribution pipes and reservoirs. Microbial corrosion is likely to occur near the weld bead, particularly with conventional welding materials. The reason for this is thought to be that fluid retention occurs due to the macro unevenness of the weld bead, and the microorganisms remarkably adhere to the surface of the smooth base material. Therefore, conventionally, it has been necessary to cut and polish the convex portion of the weld bead to the surface of the base material and finish it in the same manner as the base material, and time and cost have been spent on processing after welding.

  Moreover, even if sanitary goods were manufactured using conventional welding materials, the antibacterial properties of the welded part were not sufficient.

  An object of the present invention is to provide a stainless steel welding material that is easy to perform operations such as surface finishing after welding.

  Another object of the present invention is to provide a highly antibacterial stainless steel welding material that can prevent microorganisms.

  (1) The stainless steel welding material of the present invention has C: 0.15% by mass or less, Mn: 4.0% by mass or less, Si: 1% by mass or less, P: 0.03% by mass or less, S: 0.00%. 02% by mass or less, Ni: 8 to 30% by mass, Cr: 9 to 30% by mass, N: 0.005 to 0.40% by mass, Ag: 0.01 to 1.0% by mass, with the balance being Fe and Consists of inevitable impurities.

  (2) Moreover, C: 0.15 mass% or less, Mn: 2.1-4.0 mass%, Si: 1 mass% or less, P: 0.03 mass% or less, S: 0.02 mass% or less Ni: 10.2-30% by mass, Cr: 9-30% by mass, N: 0.005-0.40% by mass, Ag: 0.01-1.0% by mass, the balance being Fe and inevitable impurities Consists of.

  (3) The stainless steel welding material according to the present invention further contains at least one selected from Mo: 8% by mass or less and Cu: 2.5% by mass or less, (1) or (2). It is.

  (4) The stainless steel welding material of the present invention has a total of Nb and Ta: 0.01 to 2.0 mass%, Ti: 0.01 to 1.0 mass%, and Zr: 0.001 to 1.0 mass%. The stainless steel welding material according to any one of (1) to (3), further including one or more selected from%.

  (5) The stainless steel welding material of the present invention is the stainless steel welding material according to any one of (1) to (4) including B: 0.0001 to 0.0050 mass%.

  According to the present invention, Ag is concentrated on the outermost surface of the weld metal during the solidification process of the molten metal at the time of welding by containing Ag having high antibacterial properties and high safety to the human body in the welding material. To solidify. Therefore, microbial corrosion in the welded portion can be prevented without deleting and polishing the weld bead to the base metal surface and finishing the welded portion to the same level as the base metal surface. Moreover, the antibacterial property which was excellent in the weld metal surface can be obtained, and it can use for the welding of sanitary goods.

  In particular, in the present invention, the content range of Ni and Cr is higher than that of the conventional Y310S welding material. Thereby, the mechanical performance and corrosion resistance of a welding part can be improved.

  JP-A-11-172379 discloses an antibacterial stainless steel plate to which W and Ag are added, but the welding material of the present invention contains Al contained in the stainless steel plate. Absent. Therefore, generation | occurrence | production of a scale can be suppressed in the case of welding. The stainless steel plate exhibits antibacterial properties due to the interaction of W and Ag, whereas the welding material of the present invention has a higher Ag content than the stainless steel plate (base material) and exhibits antibacterial properties only with Ag. It is increasing.

  Further, if a stainless steel welding material having a higher Ag content than the base material is used as the stainless steel welding material, a welded portion that is particularly susceptible to corrosion can be reliably prevented from corrosion.

  As a welding method of the stainless steel welding material of the present invention, TIG welding or MIG welding using an inert gas is suitable in order to suppress oxidation consumption of Ag as much as possible during welding. Below, the effect | action of each composition and the reason for limitation of content are demonstrated.

  C is a solid solution strengthened element and can increase the strength of the weld metal. However, if the content exceeds 0.15% by mass, it combines with Cr to produce Cr carbide, and the corrosion resistance decreases. Therefore, the content is set to 0.15% by mass or less.

  Mn has a deoxidizing action and a desulfurizing action at the time of welding, and can fix S, which is harmful to weld cracking, and reduce weld crack sensitivity. However, when it contains exceeding 4.0 mass%, the fluidity of a molten pool will fall at the time of welding, and welding workability will fall. Moreover, hot workability also falls and productivity of a welding wire also falls. Therefore, the content is set to 4.0% by mass or less. About steel grade with high weld crack sensitivity, it is preferable to make content into 2.1-4.0 mass%.

  Since Si enhances oxidation resistance, it is effective in improving the corrosion resistance under that kind of environment. Moreover, since fluidity | liquidity of a molten pool is made favorable, when Si is raised, a smooth bead shape will be obtained and welding workability will improve. However, when it exceeds 1 mass%, the hot cracking sensitivity at the time of welding will become high. Moreover, hot workability also falls and productivity of a welding wire also falls. Therefore, the content is set to 1% by mass or less.

  P increases the sensitivity to weld cracking, so it is desirable to reduce it as much as possible. When the content exceeds 0.03% by mass, the weld cracking sensitivity is particularly high, so the content is set to 0.03% by mass or less.

  S is preferable to be reduced as much as possible because it tends to segregate at the grain boundaries, significantly promotes brittleness of the grain boundaries, increases weld cracking sensitivity, and decreases hot workability. Since the tendency will become remarkable when it exceeds 0.02 mass%, content was made into 0.02 mass% or less.

  Ni can improve mechanical performance, and if it is 8 mass% or more, a high effect will be acquired. However, if it exceeds 30% by mass, the solubility of impurity elements such as S decreases and the weld cracking sensitivity increases. Therefore, the content was set to 8 to 30% by mass. In order to further improve the ductility and toughness of the weld metal, the content is preferably 10.2 to 30% by mass.

  Cr is essential for enhancing the corrosion resistance. If it is less than 9% by mass, sufficient corrosion resistance cannot be obtained. Moreover, when it exceeds 30 mass%, it becomes easy to produce | generate an intermetallic compound in a weld metal, and may become weak. Moreover, the workability to a welding wire falls and the productivity of a welding wire falls. Therefore, the content was set to 9 to 30% by mass.

  N, like C, is a solid solution strengthened element and increases the strength of the weld metal. In order to acquire the effect, 0.005 mass% or more is required. However, if the content exceeds 0.40% by mass, the solubility in stainless steel is exceeded and blowholes due to N are generated in the weld metal, and a strong weld cannot be obtained. Therefore, the content is set to 0.005 to 0.40 mass%.

  By adding Ag, an Ag concentrated region is formed on the surface of the weld metal. Therefore, the proliferation of bacteria is suppressed and the antibacterial property of the welded portion is increased. If the effect is less than 0.01% by mass, the oxidation consumption in welding is considered insufficient. Moreover, when it contains exceeding 1.0 mass%, it will become a cause of generation | occurrence | production of a weld crack, and since Ag is expensiveness, it will become high-cost. Therefore, the content was set to 0.01 to 1.0% by mass. As described above, the content of Ag is preferably higher than that of the stainless steel plate (base material).

  The welding material of the present invention preferably further contains at least one selected from Mo: 8% by mass or less and Cu: 2.5% by mass or less. If it does in this way, stress corrosion cracking resistance and pitting corrosion resistance can be improved. However, when it adds excessively, the mechanical performance and weldability of a welding part will fall. When Mo is added excessively, intermetallic compounds are likely to precipitate, and the corrosion resistance and mechanical performance are lowered. Therefore, the content is set to 8% by mass or less. Cu has antibacterial properties like Ag, but its effect is small when added in a small amount. Moreover, when it adds excessively, Cu will precipitate to a crystal grain boundary and it will become easy to generate | occur | produce a high temperature crack at the time of welding. Therefore, the content is set to 2.5% by mass or less.

  Further, the welding material of the present invention includes a total of Nb and Ta: 0.01 to 2.0 mass%, Ti: 0.01 to 1.0 mass%, and Zr: 0.001 to 1.0 mass%. It is preferable to further contain one or more selected ones. Since these elements have a strong affinity for C and generate carbides preferentially over Cr, they suppress grain boundary precipitation of Cr carbides in the thermal cycle by welding and subsequent heat treatment, and improve intergranular corrosion resistance. If Nb is less than 0.01% by mass, it is difficult to obtain the above effect. However, if added excessively, the weld cracking sensitivity becomes high. Further, Nb has the same effect even if a part thereof is replaced with Ta. Therefore, the total content of Nb and Ta was set to 0.01 to 2.0% by mass. When Ti is less than 0.01% by mass, it is difficult to obtain the above effect. However, when it adds excessively, welding workability will fall. Therefore, the content was set to 0.01 to 1.0% by mass. If Zr is less than 0.001% by mass, it is difficult to obtain the above effect. However, if it exceeds 1.0 mass% and is added excessively, welding workability will deteriorate. Therefore, the content is set to 0.001 to 1.0% by mass.

  Moreover, it is preferable to contain B: 0.0001-0.0050 mass% in the welding material of this invention. B increases the strength of the crystal grain boundaries and suppresses the occurrence of cracks during hot working, so that the productivity of the welding wire can be improved. If it is less than 0.0001% by mass, it is difficult to obtain the effect. However, if it exceeds 0.0050 mass% and it adds excessively, it will become easy to raise | generate a weld crack. Therefore, the content was set to 0.0001 to 0.0050 mass%.

  According to the present invention, Ag is concentrated on the outermost surface of the weld metal during the solidification process of the molten metal at the time of welding by containing Ag having high antibacterial properties and high safety to the human body in the welding material. To solidify. Therefore, microbial corrosion in the welded portion can be prevented without deleting and polishing the weld bead to the base metal surface and finishing the welded portion to the same level as the base metal surface. Moreover, the antibacterial property which was excellent in the weld metal surface can be obtained, and it can use for the welding of sanitary goods.

In order to confirm the effect of the present invention, stainless steel welding materials having various compositions were made, and the antibacterial effect of the weld metal of each welding material was examined. First, stainless steel welding materials having various compositions as shown in Table 1 were welded by processing into a welding wire by hot working and cold working.

  As shown in FIG. 1, three layers of overlay welding 2 were performed on a SUS304 steel plate 1 (Ag <0.005 mass%) of 12 tmm × 100 mm × 1501 mm using a welding wire. The main welding was performed by TIG welding with an Ar gas shield having a flow rate of 15 l / min. The welding conditions were a wire diameter of 1.2 mm, a welding current of 190 A, a welding voltage of 10.5 V, a welding speed of 100 mm / min, and a wire supply rate of 100 cm / min. In TIG welding, the oxidation atmosphere of Ag is suppressed by protecting the welding atmosphere with Ar gas, and the amount of Ag in the welding wire and the weld metal hardly changes. Therefore, the Ag content in the weld metal is almost equivalent to that of the welding wire even if the welding location such as overlay welding or joint welding changes.

Next, the antibacterial effect of the weld metal of each welding material was investigated. The antibacterial property was evaluated according to JIS-Z-2801 “Antimicrobial processed product—antibacterial property test / antibacterial effect” according to the following procedure. First, Escherichia coli was dispersed in a 1/500 NB solution in which the number of bacteria was adjusted to 2 × 10 ^{6 to} 6 × 10 ⁶ cfu / ml to prepare a bacterial solution. Here, the 1/500 NB solution is obtained by diluting a normal buion medium (NB) 500 times with sterilized purified water. The normal 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. Next, the surface of the test part 3 (FIG. 1) located at the center of the weld metal of the examples and comparative examples washed and degreased with 99.5% ethanol-containing absorbent cotton or the like is used at a rate of 0.5 ml / 25 cm ^2. After wetting with (inoculating), the surface of the test section 3 was covered with a coating film. Next, the test part 3 is stored for 24 hours at a temperature of 35 ± 1.0 ° C. and RH (relative humidity) of 90% or more, and then subjected to an agar culture method (35 ± 1.0 ° C., 40 to 48 hours). The number of viable bacteria was measured and the antibacterial activity value was determined by the following formula.

R = [log (B / A) -log (C / A)] = [log (B / C)]
Here, R is an antibacterial activity value, A is an average value (number) of viable bacteria immediately after inoculation of the unprocessed test piece, and B is an average value of viable cell count after 24 hours of the unprocessed test piece. C is an average value (number) of viable cell counts after 24 hours of the antibacterial processed test piece. As described in JIS-Z-2801 (5.2.6 Test operation), the unprocessed test piece means a test piece that does not affect the growth of bacteria. Yes, the number of viable bacteria was determined under the same conditions as in the test section. In this example, the unprocessed test piece is formed of SUS304.

Table 2 shows the measurement results.

  From Table 2, in the welding materials of Examples 1 to 13 of the present invention, the viable cell count after the culture is remarkably suppressed from that of the unprocessed test piece, and the ratio of the logarithmic value of the viable cell count, that is, The antibacterial activity value is also 2.0 or more. On the other hand, in the welding materials of Comparative Examples 1 to 3 that do not contain Ag and the welding material of Comparative Example 4 in which the Ag content is less than 0.01% by mass, the viable cell count after culturing is the book containing Ag. The amount of antibacterial activity is considerably lower than that of Examples 1 to 13 of the invention, and the antibacterial effect is not recognized. From this, it can be seen that in Examples 1 to 13 of the present invention containing Ag at an appropriate value, the weld metal surface has high antibacterial properties.

It is a figure used in order to demonstrate the aspect of the welding at the time of performing the test of embodiment of this invention.

Explanation of symbols

1 Steel plate 2 Overlay welding 3 Test section

Claims (5)

  C: 0.15 mass% or less, Mn: 4.0 mass% or less, Si: 1 mass% or less, P: 0.03 mass% or less, S: 0.02 mass% or less, Ni: 8-30 mass% , Cr: 9 to 30% by mass, N: 0.005 to 0.40% by mass, Ag: 0.01 to 1.0% by mass, and the balance consisting of Fe and inevitable impurities material.   C: 0.15 mass% or less, Mn: 2.1-4.0 mass%, Si: 1 mass% or less, P: 0.03 mass% or less, S: 0.02 mass% or less, Ni: 10. 2-30% by mass, Cr: 9-30% by mass, N: 0.005-0.40% by mass, Ag: 0.01-1.0% by mass, the balance being Fe and inevitable impurities And stainless steel welding material.   The stainless steel welding material according to claim 1 or 2, further comprising at least one selected from Mo: 8 mass% or less and Cu: 2.5 mass% or less.   The sum of Nb and Ta: 0.01 to 2.0% by mass, Ti: 0.01 to 1.0% by mass, and Zr: one or more selected from 0.001 to 1.0% by mass are further included. The stainless steel welding material as described in any one of -3.   B: The stainless steel welding material according to any one of claims 1 to 4, comprising 0.0001 to 0.0050 mass%.

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