Flux-cored wire for gas-shielded arc welding

Abstract

To provide a flux-cored wire for gas-shielded arc welding capable of obtaining excellent mechanical performance and having excellent welding workability in all-position welding.SOLUTION: In terms of the total of a stainless-steel outer skin and a flux, the flux-cored wire for gas-shielded arc welding includes: C: 0.005-0.015%, Si: 0.10-0.40%, Mn: 0.5-3.5%, Ni: 7-10%, Cr: 18-24%, Mo: 0.8-2.8%, Ti: 0.001-2.000%, Al: 0.001-0.100%, Bi: 0.001-0.100%, N: 0.005-0.150%, sum of TiO2 equivalent values: 5-9%, sum of SiO2 equivalent values: 0.1 to 1.0%, sum of ZrO2 equivalent values of Zr compounds: 0.1 to 1.0%, sum of Al2O3 equivalent values: 0.1 to 1.0%, sum of FeO equivalent values: 0.05 to 0.50%, sum of Na2O equivalent values and K2O equivalent values: 0.3 to 1.0%, sum of F equivalent values: 0.01 to 0.50%, and a balance comprising unavoidable impurities.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a flux-cored wire for austenitic stainless steel, which has good mechanical properties and good weldability in all positions. [Background technology]

[0002] Austenitic stainless steel is widely used due to its workability and corrosion resistance, and the representative SUS304 steel type is used for heat-resistant steel, food equipment, building materials, etc. SUS304N1 steel type, which has been strengthened by adding N, is also widely used, and is used as a structural strength member because it can be made thinner than SUS304.

[0003] In addition, automatic welding materials such as gas-shielded arc welding and submerged arc welding are also widely used, and the technology is widely utilized.

[0004] Meanwhile, with the recent increase in size of welded structures, there is a demand for even higher strength and thinner steel sheets to be used. In response to this situation, various technologies have been proposed. For example, Patent Document 1 discloses a technology relating to an austenitic stainless steel flux-cored wire that can produce weld metal with excellent cryogenic toughness. However, the austenitic stainless steel flux-cored wire described in Patent Document 1 is unable to achieve sufficient strength.

[0005] Furthermore, Patent Document 2 discloses a technology relating to a flux-cored wire for gas-shielded arc welding of low-temperature steel, which has good welding workability in all positions, is free from welding defects, and enables stable low-temperature toughness of the weld metal. However, the flux-cored wire for gas-shielded arc welding described in Patent Document 2 cannot obtain sufficient strength. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-007982 [Patent Document 2] Japanese Patent Application Publication No. 2019-000887 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been devised in view of the above-mentioned problems, and an object of the present invention is to provide a flux-cored wire for stainless steel that can obtain good mechanical properties in welded joints produced using austenitic stainless steel such as SUS304N1 and has good welding workability in all positions. [Means for solving the problem]

[0008] A flux-cored wire for gas shielded arc welding, which is made by filling an austenitic stainless steel sheath with flux, and which contains, in mass % relative to the total mass of the wire, the total of the stainless steel sheath and flux, C: 0.005 to 0.015%, Si: 0.10 to 0.40%, Mn: 0.5 to 3.5%, Ni: 7 to 10%, Cr: 18 to 24%, Mo: 0.8 to 2.8%, Ti: 0.001 to 2.000%, Al: 0.001 to 0.100%, Bi: 0.001 to 0.100%, N: 0.005 to 0.150%, and Ti of a Ti compound. The total of O2 equivalent values: 5 to 9%, the total of SiO2 equivalent values ​​of Si compounds: 0.1 to 1.0%, the total of ZrO2 equivalent values ​​of Zr compounds: 0.1 to 1.0%, the total of Al2O3 equivalent values: 0.1 to 1.0%, the total of FeO equivalent values ​​of Fe compounds: 0.05 to 0.50%, the total of Na2O equivalent values ​​of Na compounds and K2O equivalent values: 0.3 to 1.0%, the total of F equivalent values ​​of F compounds: 0.01 to 0.50%, and the remainder being Fe from the stainless steel outer shell, Fe from the iron alloy powder, iron powder, unavoidable impurities, etc. [Effects of the Invention]

[0009] The flux-cored wire for gas shielded arc welding of the present invention provides good mechanical properties in welded joints produced using austenitic stainless steel such as SUS304N1, and has good welding workability in all positions, thereby significantly improving the reliability of welded joints in various steel structures. DETAILED DESCRIPTION OF THE INVENTION

[0010] In order to solve the above-mentioned problems, the present inventors have produced a flux-cored wire for gas-shielded arc welding and have investigated in detail the strength and toughness of the weld metal.

[0011] As a result, it was found that the strength of the weld metal can be ensured by optimizing the contents of C, Mn, Ni, Mo, and N, and further that the toughness of the weld metal can be ensured by optimizing the contents of C, Si, Ni, Mo, Ti, Al, and Bi.

[0012] In addition, with regard to welding workability, it was found that arc stabilization and reduction of spatter generation can be achieved by optimizing the Ti content, the sum of the TiO2 equivalent values ​​of Ti compounds, the sum of the Al2O3 equivalent values ​​of Al compounds, the sum of the FeO equivalent values ​​of Fe compounds, the sum of the Na2O equivalent values ​​of Na compounds and the K2O equivalent values ​​of K compounds, and the sum of the F equivalent values ​​of F compounds, and that the bead shape and bead appearance can be improved by optimizing the sum of the TiO2 equivalent values ​​of Ti compounds, the sum of the SiO2 equivalent values ​​of Si compounds, the sum of the ZrO2 equivalent values ​​of Zr compounds, and the sum of the Al2O3 equivalent values ​​of Al compounds.

[0013] In addition, it was found that the slag removability and fluidity can be improved by optimizing the Bi content, the total TiO2 equivalent value of Ti compounds, the total SiO2 equivalent value of Si compounds, the total ZrO2 equivalent value of Zr compounds, and the total Al2O3 equivalent value of Al compounds.

[0014] Furthermore, it was discovered that by optimizing the contents of Si, Mn, Al, and N, it is possible to suppress the occurrence of porosity defects such as blowholes, and by optimizing the total FeO equivalent value of Fe compounds, it is possible to suppress welding defects such as poor penetration.

[0015] Additionally, it was discovered that the corrosion resistance can be improved by optimizing the Cr and Mo contents.

[0016] The composition of the flux in the flux-cored wire for gas-shielded arc welding according to the present invention and the reasons for limiting the composition of the flux will be described in detail below. The content of each component is expressed in mass% relative to the total mass of the wire, and when expressing mass%, it will be simply written as %.

[0017] [C: 0.005~0.015%] C is added from alloy powders such as Fe-Mn and Fe-Cr in the flux, as well as from components contained in the austenitic stainless steel sheath, and is used to increase the strength of the weld metal. If C is less than 0.005%, the strength of the weld metal is insufficient. On the other hand, if C exceeds 0.015%, the strength of the weld metal becomes excessively high and the toughness decreases. Therefore, the C content is set to 0.005 to 0.015%.

[0018] [Si: 0.10~0.40%] Silicon is added to the austenitic stainless steel sheath as a component, and also as metallic silicon, Fe-Si, Fe-Si-Mn, and other alloy powders from the flux. It is used to deoxidize the weld metal. If the silicon content is less than 0.10%, deoxidation is insufficient, resulting in the formation of blowholes in the weld metal. On the other hand, if the silicon content exceeds 0.40%, low-melting-point oxides are precipitated at the grain boundaries of the weld metal, reducing the toughness of the weld metal. Therefore, the silicon content is set to 0.10 to 0.40%.

[0019] [Mn: 0.5-3.5%] Mn is added not only as a component of the austenitic stainless steel sheath but also as metallic Mn, Fe-Mn, Fe-Si-Mn, and other alloy powders from the flux. Like Si, Mn is an important deoxidizer, stabilizing the austenite phase. If the Mn content is less than 0.5%, deoxidation is insufficient, making blowholes more likely to occur in the weld metal. On the other hand, if the Mn content exceeds 3.5%, the proportion of the austenite phase increases and the proportion of the ferrite phase decreases, resulting in insufficient strength of the weld metal. Therefore, the Mn content should be 0.5 to 3.5%.

[0020] [Ni: 7-10%] Ni is added not only as a component of the austenitic stainless steel sheath but also from metallic Ni and Fe-Ni alloy powders from the flux, and has the effect of stabilizing the austenite phase and improving low-temperature toughness. If Ni is less than 7%, the proportion of the austenite phase will be insufficient and the proportion of the ferrite phase will increase, resulting in a decrease in the toughness of the weld metal. On the other hand, if Ni is more than 10%, the proportion of the austenite phase will increase and the proportion of the ferrite phase will decrease, resulting in a lack of strength in the weld metal. Therefore, the Ni content is set to 7-10%.

[0021] [Cr:18~24%] Cr is added not only as a component of the austenitic stainless steel outer sheath, but also as metallic Cr from the flux and alloy powder such as Fe-Cr, and has the effect of improving corrosion resistance by forming a passive film. If the Cr content is less than 18%, the amount is insufficient to form a passive film, resulting in reduced corrosion resistance. On the other hand, if the Cr content exceeds 24%, Cr-C and Cr-N are formed, making it impossible to form a passive film, resulting in reduced corrosion resistance. Therefore, the Cr content is set to 18-24%.

[0022] [Mo: 0.8-2.8%] Mo is added not only as a component contained in the outer sheath of austenitic stainless steel, but also as metallic Mo and Fe-Mo alloy powder from the flux, and has the effect of stabilizing the ferrite phase and increasing strength. Mo also has the effect of promoting the formation of a passive film, thereby improving corrosion resistance. If Mo is less than 0.8%, the effect of promoting the formation of a passive film is not obtained, and corrosion resistance decreases. On the other hand, if Mo exceeds 2.8%, the proportion of the ferrite phase increases, causing the strength of the weld metal to become excessively high and reducing toughness. Therefore, the Mo content is set to 0.8 to 2.8%.

[0023] [Ti:0.001~2.000% or less] Ti is added not only as a component of the austenitic stainless steel sheath but also as metallic Ti and Fe-Ti alloy powder from the flux. Like Al, Ti is effective as a deoxidizer, while also stabilizing the arc by lowering the arc potential gradient. If Ti is less than 0.001%, the arc becomes unstable. On the other hand, if Ti exceeds 2.000%, other deoxidizers in the weld metal, such as Si and Mn, remain in the weld metal, preventing the desired weld metal microstructure from being obtained, resulting in reduced toughness of the weld metal. Therefore, Ti content is limited to 0.001-2.000%.

[0024] [Al: 0.001 to 0.100%] Al is added as a component contained in the outer sheath of austenitic stainless steel, as well as from alloy powders such as metallic Al, Fe-Al, and Al-Mg from the flux, and is used to deoxidize the weld metal. If the Al content is less than 0.001%, deoxidation is insufficient, making blowholes more likely to occur in the weld metal. On the other hand, if the Al content exceeds 0.100%, other deoxidizing agents such as Si and Mn in the weld metal remain in the weld metal, preventing the desired weld metal microstructure from being obtained, thereby reducing the toughness of the weld metal. Therefore, the Al content is set to 0.001 to 0.100%.

[0025] [Bi: 0.001~0.100%] Bi is added in the form of an alloy powder such as metallic Bi, and segregates at the interface between the molten slag and the molten pool, improving slag removability. If the Bi content is less than 0.001%, the effect of improving slag removability cannot be obtained. On the other hand, if the Bi content exceeds 0.100%, low-melting-point oxides are precipitated at the grain boundaries of the weld metal, reducing the toughness of the weld metal. Therefore, the Bi content is set to 0.001 to 0.100%.

[0026] [N:0.005~0.150%] N is added from alloy powder such as Mn nitride, and has the effect of filling voids by penetrating into the atomic arrangement, thereby increasing strength. If the N content is less than 0.005%, the effect of increasing strength is not obtained, and the strength is insufficient. On the other hand, if the N content exceeds 0.150%, blowholes are more likely to occur. Therefore, the N content is set to 0.005 to 0.150%.

[0027] [Total TiO2 equivalent value of Ti compounds: 5-9%] Ti compounds are added from rutile, titanium oxide, titanium slag, calcium titanate, etc., and have the effects of stabilizing the arc, adjusting the viscosity of the molten slag to improve slag fluidity, and improving bead shape. If the total TiO2 equivalent of Ti compounds is less than 5%, the arc will become unstable and the bead shape will be poor. On the other hand, if the total TiO2 equivalent of Ti compounds exceeds 9%, the viscosity of the molten slag will increase, the slag fluidity will be poor, and the bead shape will become convex. Therefore, the total TiO2 equivalent of Ti compounds should be 5-9%.

[0028] [Total SiO2 equivalent value of Si compounds: 0.1-1.0%] Silicon compounds are added from silica sand, zircon sand, potassium feldspar, solid components of water glass such as sodium silicate and potassium silicate, and wollastonite. They increase the viscosity of the molten slag, ensuring the slag has the appropriate viscosity, improving its fluidity, slag removability, and bead shape. If the total SiO2 equivalent of silicon compounds is less than 0.1%, the viscosity of the molten slag will be low, resulting in poor slag fluidity and poor bead shape. On the other hand, if the total SiO2 equivalent of silicon compounds exceeds 1.0%, the slag will become glassy and its removability will be poor. Therefore, the total SiO2 equivalent of silicon compounds should be 0.1-1.0%.

[0029] [Total ZrO2 equivalent value of Zr compounds: 0.1-1.0%] Zr compounds, added from zircon sand, zirconia, etc., increase the viscosity of the molten slag, ensuring the slag has the appropriate viscosity, improving the fluidity of the slag and improving the bead shape. If the total ZrO2 equivalent of Zr compounds is less than 0.1%, the viscosity of the molten slag will be low, resulting in poor slag fluidity. On the other hand, if the total ZrO2 equivalent of Zr compounds exceeds 1.0%, the viscosity of the molten slag will be high, the fluidity of the slag will be poor, and the bead shape will be convex. Therefore, the total ZrO2 equivalent of Zr compounds should be 0.1 to 1.0%.

[0030] [Total Al2O3 equivalent value of Al compounds: 0.1-1.0%] Al compounds are added from alumina, potassium feldspar, etc., and have the effects of stabilizing the arc, improving bead shape, and improving slag removability. If the total Al2O3 equivalent value of Al compounds is less than 0.1%, the arc becomes unstable and the bead shape becomes poor. On the other hand, if the total Al2O3 equivalent value of Al compounds exceeds 1.0%, slag removability becomes poor. Therefore, the total Al2O3 equivalent value of Al compounds is set to 0.1 to 1.0%.

[0031] [Total of Fe compounds converted into FeO: 0.05 to 0.50% or less] Fe compounds are added in the form of hematite, magnetite, etc., and have the effect of strengthening the arc blow strength and suppressing poor penetration. If the total FeO equivalent value of Fe compounds is less than 0.05%, the arc blow strength will be insufficient, making welding defects such as poor penetration more likely to occur. On the other hand, if the total FeO equivalent value of Fe compounds exceeds 0.50%, the arc blow strength will be excessively strong, resulting in a large amount of spatter. Therefore, the total FeO equivalent value of Fe compounds should be 0.05 to 0.50% or less.

[0032] [Total of NaO equivalent value of Na compounds and KO equivalent value of K compounds: 0.3-1.0%] Na compounds are added from solid components of water glass such as sodium silicate or sodium fluoride, while K compounds are added from solid components of water glass such as potassium silicate, potassium silicate fluoride, and potassium feldspar. These compounds optimize arc blow strength and improve arc stability. Sodium silicate and potassium silicate are also added to Si compounds, but the Na and K compounds, respectively, are extracted and the Si compound components are used to define the ranges of each component described above. If the sum of the NaO equivalent value of the Na compound and the KO equivalent value of the K compound is less than 0.3%, the arc blow strength will be insufficient and the arc will become unstable. On the other hand, if the sum of the NaO equivalent value of the Na compound and the KO equivalent value of the K compound exceeds 1.0%, the arc blow strength will be strong and the amount of spatter will increase. Therefore, the sum of the NaO equivalent value of the Na compound and the KO equivalent value of the K compound should be 0.3-1.0%.

[0033] [Total F-equivalent value of F compounds: 0.01-0.50%] Fluorine compounds are added from sodium fluoride, potassium silicofluoride, etc., and have the effect of lowering the potential gradient of the arc and stabilizing the arc. If the total F-equivalent value of the Fluorine compounds is less than 0.01%, the arc stabilizing effect is not obtained and the arc becomes unstable. On the other hand, if the total F-equivalent value of the Fluorine compounds exceeds 0.50%, the arc becomes coarse and the amount of spatter generated increases. Therefore, the total F-equivalent value of the Fluorine compounds is set to 0.01 to 0.50%.

[0034] The remainder of the flux-cored wire for gas-shielded arc welding of the present invention is Fe from the stainless steel sheath, Fe from the iron alloy powder, iron powder, inevitable impurities, etc. Examples of inevitable impurities include P, S, Cu, Nb, V, and B. In particular, P and S both form compounds with low melting points and reduce the toughness of the weld metal, so the total amount of impurities is preferably adjusted to 1.0% or less.

[0035] Furthermore, it is preferable to use SUS301 or SUS304 as specified in JIS G4305:2021 for the stainless steel sheath, with a C content of 0.08% or less, and the C content can be adjusted appropriately from the flux to adjust strength. P in the stainless steel sheath reduces toughness, so it is preferable that it be 0.010% or less, and S, which reduces the fluidity of the slag, is 0.010% or less. [Example]

[0036] The effects of the present invention will be explained in more detail below using examples, but the present invention is not limited to the following examples. In the examples, a welding power source for gas-shielded arc welding is used, but the type of welding power source is not limited.

[0037] Flux having the composition shown in Table 2 was filled into the stainless steel sheath shown in Table 1 to produce a prototype flux-cored wire for gas shielded arc welding.

[0038] [Table 1]

[0039] [Table 2]

[0040] Using the various prototype welding wires listed in Table 2, weld metal specimens were prepared using 20mm thick steel plates with the chemical compositions listed in Table 3, with a 20° groove angle and a 16mm root gap, and then buttered. The welding conditions listed in Table 4 were used to prepare weld metal specimens. Radiographic testing in accordance with JIS Z3104:1995 was then conducted to examine for weld defects. Tensile test specimens (JIS Z2241:2011 No. 10) and V-notch impact test specimens (JIS Z2242:2018) were then taken from the center of the plate thickness. For the tensile test, a tensile strength of 690-750 MPa was considered good. For toughness evaluation, a Charpy impact test was conducted at a test temperature of -196°C, and an average absorbed energy of 27 J or greater was considered good. Furthermore, a ferric chloride corrosion test on stainless steel was conducted in accordance with JIS G0578:2000. Pitting corrosion at 20°C was considered poor. Weldability was evaluated by measuring the amount of spatter generated using 9mm thick steel plates with the chemical composition shown in Table 3 under the conditions shown in Table 4, and investigating arc stability, bead shape, bead appearance, slag removability, and slag fluidity during welding. The test results are summarized in Table 5.

[0041] [Welding workability] (Arc stability) When the arc was stable during welding and did not disappear, it was judged as good, and when the arc was unstable or disappeared even once, it was judged as bad.

[0042] (amount of spatter generated) It is preferable to generate as little spatter as possible during welding. Specifically, a copper collection box was used to measure the weight of spatter generated during one minute of welding, and the value per unit time (g / min) was calculated. Spatter was measured five times under the welding conditions shown in Table 3, and the average value was calculated. A value of 1.0 g / min or less was considered good.

[0043] (Bead shape and appearance) It is preferable that the bead waveform of the weld metal is uniform and free of disturbance, and that undercuts and overlaps that require rework do not occur. It is also preferable that the weld metal has a bead shape with excellent uniformity in the reinforcement height and bead width. Specifically, cases where the bead waveform on the weld metal bead surface is disturbed or has convex parts, or where undercuts and overlaps that require rework occur, are judged to be defective.

[0044] (Slag removability) It is preferable that the solidified slag on the weld bead surface can be easily removed after welding. If the slag peels off naturally after welding, or if the solidified slag on the weld bead surface is hit with a chipping hammer (total length 300 mm, weight 350 g) by gently swinging it down in an arc around the handle, the slag cracks and can then be easily removed, the result is considered good. If the slag does not peel off naturally and the slag does not crack when the chipping hammer is swung down in the above manner, the result is considered poor.

[0045] (Slag fluidity) A good case was judged as the molten slag remaining on or around the molten pool did not obstruct the arc and easily moved to the rear of the weld pool in the welding direction, while a poor case was judged as the molten slag remained too much and obstructed the arc.

[0046] [Welding defects] Specifically, radiographic testing was conducted in accordance with JIS Z3104:1995 to investigate the presence or absence of welding defects such as blowholes and poor penetration.

[0047] [Table 3]

[0048] [Table 4]

[0049] [Table 5]

[0050] In Tables 2 and 5, welding wires No. 1 to No. 11 are examples of the present invention, and welding rods No. 12 to No. 22 are comparative examples. In the welding wires No. 1 to No. 11, which are examples of the present invention, the total of the TiO2-equivalent values ​​of C, Si, Mn, Ni, Cr, Mo, Ti, Al, Bi, N, the total of the TiO2-equivalent values ​​of Ti compounds, the total of the SiO2-equivalent values ​​of Si compounds, the total of the ZrO2-equivalent values ​​of Zr compounds, the total of the Al2O3-equivalent values ​​of Al compounds, the total of the FeO-equivalent values ​​of Na compounds, the total of the Na2O-equivalent values ​​of K compounds, and the total of the F-equivalent values ​​of F compounds were all appropriate amounts, resulting in good arc stability, low spatter generation, and good welding workability, including good bead shape, bead appearance, slag removability, and slag fluidity. There were no weld defects, and the tensile strength and absorbed energy of the weld metal were good, as were the corrosion resistance, resulting in very satisfactory results.

[0051] Among the comparative examples, welding rod No. 12 had a high carbon content, resulting in excessive tensile strength of the weld metal and low absorbed energy. Also, because the total TiO2 equivalent value of Ti compounds was high, the slag fluidity was poor and the bead shape was convex. Furthermore, because the total Na2O equivalent value of Na compounds and K2O equivalent value of K compounds was low, the arc was unstable.

[0052] Welding rod No. 13 had a low carbon content, which resulted in insufficient tensile strength of the weld metal. Also, the total TiO2 equivalent value of the Ti compounds was low, which resulted in an unstable arc and poor bead shape. The total ZrO2 equivalent value of the Zr compounds was low, which resulted in poor slag fluidity. Additionally, the total FeO equivalent value of the Fe compounds was high, which resulted in increased spatter.

[0053] Welding rod No. 14 contained a large amount of Mo, resulting in excessive tensile strength of the weld metal and low absorbed energy. Also, the total SiO2 equivalent value of Si compounds was high, resulting in poor slag removability. Furthermore, the total ZrO2 equivalent value of Zr compounds was high, resulting in a convex bead shape. Additionally, the total FeO equivalent value of Fe compounds was low, resulting in poor penetration.

[0054] Welding rod No. 15 had a low Si content, which caused blowholes. It also had a high Ni content, which resulted in insufficient tensile strength in the weld metal. It also had a low Ti content, which resulted in an unstable arc. Additionally, the total Na2O equivalent value of the Na compounds and the K2O equivalent value of the K compounds was high, which resulted in increased spatter.

[0055] Welding rod No. 16 had a high Mn content, which resulted in insufficient tensile strength of the weld metal. It also had a high Cr content, which resulted in reduced corrosion resistance. Furthermore, the total SiO2 equivalent value of Si compounds was low, which resulted in poor slag fluidity and a poor bead shape.

[0056] Welding rod No. 17 had a low Mn content, which caused blowholes. It also had a low Ni content, which reduced the absorbed energy of the weld metal. It also had a low Mo content, which reduced corrosion resistance. Additionally, the total F-equivalent value of the fluorine compounds was low, which resulted in an unstable arc.

[0057] Welding rod No. 18 had a high Si content, which resulted in low absorbed energy in the weld metal. It also had a low Cr content, which resulted in reduced corrosion resistance. Furthermore, it had a low Al content, which resulted in blowholes.

[0058] Welding rod No. 19 had a high Ti content, so the absorbed energy of the weld metal was low. Also, because it had a high N content, blowholes occurred. Furthermore, because the total Al2O3 equivalent value of the Al compounds was low, the arc became unstable and the bead shape was poor. In addition, because the total F equivalent value of the F compounds was high, spatter increased.

[0059] Welding rod No. 20 had a high Al content, so the absorbed energy of the weld metal was low. Also, the total Al2O3 equivalent value of Al compounds was high, so slag removability was poor.

[0060] Welding rod No. 21 contained a large amount of Bi, so the absorbed energy of the weld metal was low.

[0061] Welding rod No. 22 had poor slag removal due to the low Bi content, and the low N content resulted in insufficient tensile strength of the weld metal.

Claims

[Claim 1] A flux-cored wire for gas shielded arc welding, which is made by filling a flux in an austenitic stainless steel outer sheath, The total mass of the stainless steel sheath and flux is expressed as a percentage by mass of the total wire mass. C: 0.005-0.015%, Si: 0.10-0.40%, Mn: 0.5-3.5%, Ni: 7 to 10%, Cr: 18-24%, Mo: 0.8-2.8%, Ti: 0.001 to 2.000%, Al: 0.001-0.100%, Bi: 0.001-0.100%, N: 0.005-0.150%, Ti compound TiO 2 Total conversion value: 5-9% Si compound SiO 2 Total conversion value: 0.1 to 1.0%, Zr compound ZrO 2 Total conversion value: 0.1 to 1.0%, Al in Al compounds 2 O 3 Total conversion value: 0.1 to 1.0%, Total of Fe compounds in terms of FeO: 0.05 to 0.50% Na in Na compounds 2 O equivalent value and K of K compounds 2 Total of O equivalent value: 0.3 to 1.0%, The total F-equivalent value of F compounds is 0.01 to 0.50%, A flux-cored wire for gas shielded arc welding, the balance of which is Fe in the stainless steel sheath, Fe from the iron alloy powder, iron powder, and unavoidable impurities.

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