AU2021299003B2

AU2021299003B2 - Gas shielded arc welding method, structure object production method, and shielding gas

Info

Publication number: AU2021299003B2
Application number: AU2021299003A
Authority: AU
Inventors: Mayumi Abe; Takanori KOZUKI; Naoki Mukai; Masamichi Suzuki
Original assignee: Kawasaki Heavy Industries Ltd; Kobe Steel Ltd; Kawasaki Jukogyo KK
Current assignee: Kobe Steel Ltd; Kawasaki Motors Ltd
Priority date: 2020-06-29
Filing date: 2021-02-03
Publication date: 2024-05-09
Anticipated expiration: 2041-02-03
Also published as: JP2022022608A; TW202200296A; CN115916445A; WO2022004032A1; JP7428601B2; AU2021299003C1; KR20230003531A; AU2021299003A1

Abstract

Provided is a gas shielded arc welding method with which arc stability is high and incomplete fusion can be suppressed, regardless of the conditions of a welding material, a welding base material, and the like. Also provided are a structure object production method using the welding method, and a shielding gas to be used in the welding method. The shielding gas to be used in the gas shielded arc welding contains, with respect to the total volume of the shielding gas, between 0.5 % by volume and 2.0 % by volume inclusive of CO

Description

GAS SHIELDED ARC WELDING METHOD, STRUCTURE OBJECT PRODUCTION METHOD, AND SHIELDING GAS TECHNICAL FIELD

[0001] The present disclosure relates to a gas shielded arc welding method in which welding is performed using a shielding gas containing Ar as a main component, a structure object production method, and a shielding gas.

BACKGROUND

[0002] In gas shielded arc welding, a shielding gas is used to protect a molten metal (hereinafter, also referred to as a molten pool) from adverse influences of nitrogen and oxygen in the atmosphere. The composition of the shielding gas is variously optimized depending on the steel type of a welding wire and a welding base metal (hereinafter, also simply referred to as a "base metal" or "workpiece") used, and the application of a structure object to be produced. For example, when high alloy steel such as a stainless steel is used as the welding wire, for the purpose of reducing the content of oxygen in a weld metal after welding and ensuring excellent mechanical performance, particularly toughness, it is generally to use, as a shielding gas, a mixed gas containing Ar as a main component and a small amount of 02 or C02.

[0003] Thus, when the mixed gas containing Ar as a main component is used as the shielding gas, it is possible to ensure excellent toughness by increasing the content of Ar in the shielding gas. On the other hand, there is a problem that the penetration performance is poor and welding defects such as lack of fusion occur. This is due to the property that the potential gradient of Ar is low, and the higher the ratio of Ar in the shielding gas, the easier the arc spreads, the smaller the current density, and the lower the force for pushing down the molten pool (hereinafter, also referred to as an arc force).

[0004] In order to solve such problems, Patent Literature 1 discloses a flux-cored wire made of a metal oxide, a carbonate salt, a metal fluoride, and a metal powder with a stainless steel or a nickel alloy as a sheath. The flux-cored wire disclosed in the above Patent

Literature 1 contains, as flux component, 5 wt% to 10 wt% of TiO2, 0 wt% to 1.5 wt% of Si0 2 , 0.1 wt% to 1 wt% of a carbonate salt, 0.05 wt% to 0.5 wt% of a metal fluoride in terms of a fluorine amount, and 1 wt% to 30 wt% of a metal powder mixture in which the amount of silicon is 0.1 wt% to 1.5 wt%, with respect to the total wire weight. It is disclosed that, by using the above flux-cored wire, even when welding is performed with a shielding gas composition of 80% Ar + 20% C02, welding can be performed same as a case of performing welding using a shielding gas containing 100% C02, and no defects occur.

[0005] In addition, Patent Literature 2 discloses a shielding gas for MAG welding for welding a high Cr steel containing 8 wt% or more and 13 wt% or less of Cr using a solid wire containing 8 wt% or more and 13 wt% or less of Cr. Specifically, the above shielding gas for MAG welding is for welding a narrow groove having a groove angle 01 of 10° or less in one layer one pass, in which a ratio of a thickness Hi of a pair of base metals to a groove distance WI between the base metals of 0.4 or less. In addition, the above Patent Literature 2 discloses that the above shielding gas contains three types of gases, i.e., a mixed gas containing 17 vol% or less of a carbon dioxide gas, 30 vol% or more and 80 vol% or less of a helium gas, with the remainder being an argon gas, and the penetration is improved.

CITATION LIST PATENT LITERATURE

[0006] Patent Literature 1: JP2001-25893A Patent Literature 2: JP2013-46932A

[0006A] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each of the appended claims. SUMMARY

[0007] However, Patent Literature 1 assumes only a shielding gas having an Ar gas of 80% or less, and does not consider the toughness of the weld metal. In addition, the welding material used is limited to the flux-cored wire, and no consideration is given to a solid wire. For example, when a flux-cored wire is used, since the flux itself contains a large amount of an oxide having a low work function, and this oxide acts as a cathode spot for emitting electrons, high arc stability can be obtained. In contrast, when a solid wire is used, the higher the ratio of Ar in the shielding gas, the more difficult it is for the cathode spot to be formed on the surface of the molten metal, so that arc deflection occurs frequently and the arc is unstable. Therefore, when a solid wire is used, lack of fusion is more likely to occur in a high Ar atmosphere than when a flux-cored wire is used.

[0008] The shielding gas disclosed in Patent Literature 2 contains three types of gases, i.e., a mixed gas containing a carbon dioxide gas (C0 2 ), a helium (He) gas, and an argon (Ar) gas, and the content of the He gas is 30 vol% to 80 vol%, which is a composition in which the He gas occupies most of the shielding gas. However, the He gas is known to be in short supply worldwide recently, and since it is a high-cost gas, it cannot be said to be a gas that can be used for general purposes. Further, welding conditions to which the shielding gas disclosed in Patent Literature 2 is applied are limited to one layer one pass, the ratio of the thickness Hi of the pair of base metals to the groove distance WI between the base metals being 0.4 or less, and being for welding a narrow groove having a groove angle 01 of 100 or less. Therefore, there is a demand for the development of a welding method capable of performing welding without using a He gas and without particularly limiting the welding conditions.

[0009] The present disclosure has been made in view of such problems, and some aspects or embodiments of the present disclosure may provide a gas shielded arc welding method in which a main component is Ar, which is a general-purpose gas, and which has high arc stability and can prevent lack of fusion regardless of conditions such as the type and shape of a welding material and a welding base metal, a structure object production method using this welding method, and a shielding gas for use in this welding method.

[0010] As a result of intensive research to solve the above problems, the present inventors have found that using a shielding gas containing Ar as a main component, having reduced amount of molecular gases having oxygen atoms such asC02and02, and having well- controlled C02 and H2 contents and a relative ratio thereof is effective.

[0011] The present disclosure provides the following configuration [1] related to a gas shielded arc welding method.

[0012]

[1] A gas shielded arc welding method including welding a base metal while flowing a shielding gas to a weld region in the base metal using a welding wire as an electrode, in which the shielding gas contains, with respect to a total volume of the shielding gas, C02: 0.6 vol% or more and 2.0 vol% or less, and H2: 0.5 vol% or more and 3.0 vol% or less,

with the remainder being Ar and an unavoidable impurity, and the following expression (1) and expression (2) are satisfied, 1.56 < [C02]+[H2] < 4.40 (1) 0.35 < [H2]/([CO2]+[H2]) < 0.74 (2) in which the content of C02 with respect to the total volume of the shielding gas is

[C0 2 ] in vol% and the content of H2 with respect to the total volume of the shielding gas is

[H2] in vol%.

[0013] Preferred embodiments of the present disclosure related to a gas shielded arc welding method relates to the following [2] to [6].

[0014]

[2] The gas shielded arc welding method according to [1], in which the following expression (3) is satisfied, 57.0 < 0.5x[Ar]+1.5x[CO2]+10x[H2] < 80.0 (3) in which the content of Ar with respect to the total volume of the shielding gas is

[Ar] in vol%.

[0015]

[3] The gas shielded arc welding method according to [1] or [2], in which the welding wire contains, with respect to a total mass of the welding wire, Cr: 18 mass% or more and 28.5 mass% or less, and Ni: 8.0 mass% or more and 37.0 mass% or less, and the welding wire's chemical composition corresponds to a microstructure having a ferrite percentage of 15.3% or less based on a DeLong diagram.

[0016]

[4] The gas shielded arc welding method according to [3], in which the welding wire contains, with respect to the total mass of the welding wire, C: 0.20 mass% or less (including 0 mass%), Si: 1.00 mass% or less (including 0 mass%), Mn: 4.8 mass% or less (including 0 mass%), P: 0.03 mass% or less (including 0 mass%), S: 0.03 mass% or less (including 0 mass%), Cu: 4.0 mass% or less (including 0 mass%), Mo: 4.0 mass% or less (including 0 mass%), Nb: 1.0 mass% or less (including 0 mass%), and N: 0.30 mass% or less (including 0 mass%).

[0017]

[5] The gas shielded arc welding method according to any one of [1] to [4], in which the weld region in the base metal has a groove, the groove has one of groove shape selected from a single V shape, a single bevel, an I shape, a double bevel, an X shape, a J shape, and a U shape, and the groove has a groove angle of 0° to 90.

[0018]

[6] The gas shielded arc welding method according to any one of [1] to [5], in which a gas flow rate Q of the shielding gas is 10 L/min to 30 L/min, a wire extension L is 10 mm to 30 mm, and a ratio of the gas flow rate Q (L/min) to the wire extension L (mm) satisfies the following expression (4), 0.5 < Q/L < 2.2 (4).

[0019] In addition, some aspects or embodiments of the present disclosure may provide the following configuration [7] related to a structure object production method.

[0020]

[7] A structure object production method by gas shielded arc welding using a welding wire and a shielding gas, in which the shielding gas contains, with respect to a total volume of the shielding gas,

C02: 0.6 vol% or more and 2.0 vol% or less, and H2: 0.5 vol% or more and 3.0 vol% or less, with the remainder being Ar and an unavoidable impurity, and the following expression (1) and expression (2) are satisfied, 1.56 <[C02]+[H2]< 4.40 (1) 0.35 < [H2]/([CO2]+[H2])< 0.74 (2) in which the contentof C02with respect to the total volume of the shielding gas is

[C0 2 ] in vol% and the content of H2with respect to the total volume of the shielding gas is

[H2] in vol%.

[0021] Further, some aspects or embodiments of the present disclosure may provide the following configuration [8] related to a shielding gas.

[0022]

[8] A shielding gas for use in gas shielded arc welding, the shielding gas containing: with respect to a total volume of the shielding gas, C02: 0.6 vol% or more and 2.0 vol% or less, and H2: 0.5 vol% or more and 3.0 vol% or less, with the remainder being Ar and an unavoidable impurity, in which the following expression (1) and expression (2) are satisfied, 1.56 <[C02]+[H2]< 4.40 (1) 0.35 < [H2]/([CO2]+[H2])< 0.74 (2) in which the contentof C02with respect to the total volume of the shielding gas is

[H2] in vol%.

[0023] With the gas shielded arc welding method according to the present disclosure, the arc stability is high and it is possible to prevent lack of fusion regardless of conditions such as the type and shape of a welding material and a welding base metal. In addition, with the structure object production method according to the present disclosure, it is possible to produce a good joint in which the occurrence of lack of fusion is prevented.

BRIEF DESCRIPTION OF DRAWINGS

[0024]

[Fig. 1] Fig. 1 is a DeLong diagram when the vertical axis is nickel equivalent (%) and the horizontal axis is chromium equivalent (%).

[Fig. 2] Fig. 2 is a schematic view showing an example of a welding device that can be used in the present disclosure.

[Fig. 3] Fig. 3 is a photograph substituted for drawing showing a cross section of a weld metal in Sample No. B Iin Test No. T (welding current: 150 A).

[Fig. 4] Fig. 4 is a photograph substituted for drawing showing a cross section of a weld metal in Sample No. B16 in Test No. T16 (welding current: 150 A).

[Fig. 5] Fig. 5 is a photograph substituted for drawing showing a bead appearance in a test plate welded by a method according to the present disclosure.

[Fig. 6] Fig. 6 is a photograph substituted for drawing showing a cross section of the weld metal in the test plate welded by the method according to the present disclosure.

DESCRIPTION OF EMBODIMENTS

[0025] Embodiments for carrying out the present disclosure will be described in detail below. The present disclosure is not limited to the embodiment to be described below. In the description, the numerical range using the word "to" between numerical values indicates that the numerical value described before the word "to" is included as the lower limit value of the numerical range and the numerical value described after the word "to" is included as the upper limit value of the numerical range.

[0025A] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[0026]

[Gas Shielded Arc Welding Method] A gas shielded arc welding method according to the present disclosure is a method in which a consumable electrode (hereinafter, also referred to as a welding wire) is supplied via a welding torch, and welding is performed while flowing a shielding gas into a weld region in a welding base metal. Since the present disclosure also relates to a shielding gas for use in the above welding method, the shielding gas according to the present disclosure will be described first.

[0027]

[Shielding Gas] The shielding gas according to the present disclosure containsC02 (carbon dioxide) and H2 (hydrogen), and the remainder is Ar (argon) and an unavoidable impurity. As described above, the shielding gas is used to protect a molten metal from adverse influences of nitrogen and oxygen in the atmosphere. On the other hand, when the shielding gas contains a molecular gas having oxygen atoms such asC02and02, the oxygen atoms contained in the shielding gas enter the molten metal. In order to ensure excellent toughness of the weld metal, which is the premise of the present disclosure, it is a condition that the weld metal has low oxygen. Therefore, the shielding gas according to the present disclosure contains an Ar gas, which is a general-purpose inert gas, as a main component while minimizing the amount of the molecular gas having an oxygen atom.

[0028] Further, as described above, the shielding gas dominated by an Ar gas has a problem that lack of fusion occurs due to a decrease in arc force and arc instability caused by arc deflection. In contrast, in the present disclosure, the contents of theC02gas and the H2gas are appropriately controlled, and the remainder is, for example, 95 vol% or more of Ar gas. Therefore, it is possible to maintain the arc stability and the arc force and prevent lack of fusion while maintaining a low oxygen amount in the weld metal. As will be described later, theC02gas is a gas that contributes to the arc stability, and the H2gas is a gas that contributes to the arc force. Hereinafter, each gas composition and an appropriate range thereof will be described in detail.

[0029] <CO2: 0.5 vol% or more and 2.0 vol% or less> C02 easily dissociates into atoms in the arc and takes dissociation heat from the arc, which thus contributes to the pinch effect of arc. The ratio of the potential gradientof C02 when air is 1 is 1.5. The 0 obtained by dissociation (oxygen atom) reacts with a deoxidizing element on the molten pool to form an oxide on the surface of the molten pool, and this oxide acts as a cathode spot to prevent arc deflection and stabilizes the arc. However, when the 0 obtained by dissociation enters the molten metal, the amount of oxygen in the weld metal may increase as a result, so thatC02 in the shielding gas needs to be appropriately controlled. When the contentof C02 is less than 0.5 vol%, mainly the arc stabilizing effect cannot be ensured. Therefore, the contentof CO2 in the shielding gas is 0.5 vol% or more, preferably 0.6 vol% or more, and more preferably 0.9 vol% or more, with respect to the total volume of the shielding gas.

[0030] On the other hand, when the contentof CO2 is more than 2.0 vol% and is contained in an excessive amount, the mixing of oxygen into the molten metal and excessive pinch of arc result in a globule transfer form of droplet transfer, which tends to result in an unstable arc. Therefore, the contentof CO2 in the shielding gas is 2.0 vol% or less with respect to the total volume of the shielding gas. When the contentof C02 in the shielding gas is preferably 1.5 vol% or less, and more preferably 1.1 vol% or less, with respect to the total volume of the shielding gas, oxygen entering the molten metal can be further prevented, so that better toughness can be ensured.

[0031] When the shielding gas containsC02,C (carbon) or CO (carbon monoxide) is generated during dissociation, and the action of reducing 0 adsorbed on the surface of the molten pool works. Therefore, although it is a molecular gas having oxygen atoms, oxygen entering the molten metal can be prevented as much as possible. Such an effectof C02 cannot be replaced by another molecular gas having oxygen atoms, for example,02which is mentioned as a general-purpose gas for welding. This is because when the shielding gas contains02, after the dissociationof 02,0 is not reduced but is adsorbed on the surface of the molten pool, and oxygen enters the molten metal. As a result, the amount of oxygen in the weld metal increases, and the glossiness of the bead surface after welding deteriorates. Therefore, in the present disclosure,CO2 is selected as the molecular gas having oxygen atoms that ensures the arc stability while preventing an increase in amount of oxygen in the weld metal and maintaining a good bead appearance.

[0032] <H2: 0.5 vol% or more and 3.0 vol% or less> H2 is a molecule having a potential gradient higher than other molecules, and the ratio of the potential gradient of H2when air is 1 is 10. This is due to the extremely low dissociation voltage of H2,which takes away a large amount of dissociation heat, and thus greatly contributes to the pinch effect of arc. In addition, H2also has a reducing effect and has an effect of preventing oxygen entering the molten metal. When the content of H2 is less than 0.5 vol%, the pinch effect of arc cannot be obtained, the current density decreases, and the arc force decreases, resulting in lack of fusion. Therefore, the content of H2 in the shielding gas is 0.5 vol% or more, preferably 0.8 vol% or more, and more preferably 1.0 vol% or more, with respect to the total volume of the shielding gas.

[0033] On the other hand, when the content of H2 is more than 3.0 vol%, the excessive action of the pinch effect of arc causes the droplet transfer to be in a globule transfer form. The globule transfer is a phenomenon in which droplets are pushed up by the arc force and coarse droplets having a wire diameter or more are irregularly separated, so that the arc is unstable. Therefore, the content of H2 in the shielding gas is 3.0 vol% or less, and preferably 2.8 vol% or less, with respect to the total volume of the shielding gas.

[0034] <Remainder: Ar and unavoidable impurity> (Ar: 95 vol% or more and 98.5 vol% or less) The Ar gas is also called an inert gas or a noble gas because Ar is a monatomic molecule and has a property of not forming a stable chemical bond. In welding, the larger the ratio of Ar gas, that is, an inert gas, contained in the shielding gas, the more oxygen and the like entering the molten metal from the shielding gas can be prevented, and the amount of oxygen in the weld metal can be reduced. Therefore, the shielding gas according to the present disclosure contains the above C02 and H2 with the remainder being Ar and an unavoidable impurity, and the content of Ar is not particularly limited. When the content of Ar is 95 vol% or more, the content of oxygen in the weld metal can be decreased and excellent toughness can be ensured. Therefore, the content ofAr in the shielding gas is preferably 95 vol% or more, more preferably more than 95 vol%, and still more preferably 96 vol% or more, with respect to the total volume of the shielding gas.

[0035] On the other hand, when content of Ar is 98.5 vol% or less, it is possible to prevent the potential gradient of the arc, that is, the voltage per unit distance, from becoming low, and the arc length and the spread of the arc can be maintained appropriately and the current density can be increased at an appropriate arc voltage. As a result, it is possible to prevent a decrease in arc force and prevent the occurrence of lack of fusion. In addition, it is possible to prevent the arc deflection due to the instability of the cathode spot, and the arc is stabilized. Therefore, the content of Ar in the shielding gas is preferably 98.5 vol% or less, and more preferably 98.1 vol% or less, with respect to the total volume of the shielding gas.

The ratio of the potential gradient of Ar when air is 1 is 0.5.

[0036] (Unavoidable impurity) Examples of the unavoidable impurity which may be contained in the shielding gas according to the present disclosure include oxygen, nitrogen, and water. Among the above unavoidable impurity, the smaller the content of oxygen, the better. When the content of02 in the shielding gas is 0.02 vol% or less with respect to the total volume of the shielding gas, the effect of the present disclosure is not hindered. In addition, the smaller the content of other unavoidable impurities, the better. When the content of each component other than 02 in the shielding gas is 0.03 vol% or less with respect to the total volume of the shielding gas, the effect of the present disclosure is not hindered. The total amount of the unavoidable impurity contained in the shielding gas is preferably limited to 0.05 vol% or less, and more preferably limited to 0.03 vol% or less, with respect to the total volume of the shielding gas.

[0037] <1.30 < [C02]+[H2] < 4.40> As described above, since both C02 and H2 are components that contribute to the pinch effect of arc and have the effect of improving the arc stability, the optimum range of the total amount thereof is also limited in the present disclosure. When, with respect to the total volume of the shielding gas, the content of C02 is

[C0 2 ] in vol% and the content of H2 is [H2] in vol%, if [C02]+[H2] is less than 1.30, it is not possible to obtain one or both of the effect of preventing the lack of fusion and the effect of improving the arc stability due to the pinch effect of arc. On the other hand, when [C02]+[H2] is more than 4.40, the pinch effect of arc is excessive, the arc is unstable.

[0038] Therefore, the content of C02 and the content of H2 satisfy the following expression (1). The value obtained by [C02]+[H2] is preferably 1.50 or more, more preferably 1.90 or more, and is preferably 4.30 or less, more preferably 3.90 or less.

[0039] 1.30 < [C02]+[H2] < 4.40 (1)

[0040] <0.35 < [H2]/([CO2]+[H2]) < 0.74> Since H2 greatly contributes to the pinch effect of arc, the optimum range is also limited for the ratio of the content of H2 to the total amount of the content of C02 and the content of H2 in the present disclosure. That is, only when the total amount of the content of C02 and the content of H2 satisfies the above expression (1), and the ratio of H2 to the total amount satisfies the following expression (2), both the effect of preventing the lack of fusion and the effect of improving the arc stability, which are the effects of the present disclosure, are exhibited.

[0041] When the ratio of the content of H2 to the total amount of the content of C02 and the content of H2 is less than 0.35, the pinch effect of arc is reduced, and there is a risk of lack of fusion. On the other hand, when the ratio is more than 0.74, the arc stabilizing effect of C02 is not exhibited, and the droplet transfer is in a globule transfer form due to the excessive pinch effect of arc, resulting in a more unstable arc. Therefore, the content of C02 and the content of H2 satisfy the following expression (2). The value obtained by [H2]/([CO2]+[H2]) is preferably 0.40 or more, more preferably 0.47 or more, and is preferably 0.70 or less, more preferably 0.67 or less.

[0042] 0.35 < [H2]/([CO2]+[H2]) < 0.74 (2)

[0043] <57.0 < 0.5x[Ar]+1.5x[CO2]+10x[H2] < 80.0> As described above, in the present disclosure, when the content of C02, the content of H2, and the content of Ar in the shielding gas are appropriately controlled, it is possible to prevent the occurrence of lack of fusion and improve arc stability. The effect of each of these gases on preventing lack of fusion and improving arc stability is determined by the potential gradient ratio when air is 1.

[0044] When, with respect to the total volume of the shielding gas, the content of Ar is [Ar] in vol%, the content of C02 is [C0 2 ] in vol%, and the content of H2 is [H2] in vol%, if the value obtained by 0.5x[Ar]+1.5x[CO2]+10x[H2] is in the range of 57.0 or more and 80.0 or less, both the pinch effect of arc and the arc stabilizing effect can be obtained. Therefore, in the present disclosure, it is preferable to satisfy the following expression(3). The value obtained by 0.5x[Ar]+1.5x[CO2]+10x[H2] is preferably 59.0 or more, more preferably 63.0 or more, and is preferably 79.0 or less, more preferably 78.0 or less.

[0045] 57.0 < 0.5x[Ar]+1.5x[CO2]+10x[H2]< 80.0 (3)

[0046] The shielding gas according to the present disclosure is a mixed gas in which the contentof C02and the content ofH2are appropriately controlled and the remainder being Ar and an unavoidable impurity. In the use thereof, a method using a cylinder for gas (hereinafter, also referred to as a gas cylinder) filled with a prepared mixed gas or a method of mixing these gases using a gas mixer is preferred, and in order to obtain the effects in the present disclosure, a method of ejecting the mixed gas from one nozzle using a gas cylinder or a mixer is more preferred. On the other hand, in the method of mixing the gases near the molten metal using a double shielding gas method using two nozzles on an outer side and an inner side, the composition of the gas becomes non-uniform, and the effects in the present disclosure may not be exhibited. In addition, in the double shielding gas method, when Ar is used on the outer side andC02or H2gas is used on the inner side, the active gas is locally present, which may adversely influence the shape and glossiness. Therefore, it is desirable not to use the method of mixing the gases near the molten metal because the effects in the present disclosure may not be fully exhibited.

[0047] Next, a preferred form of the welding wire used in combination with the shielding gas for use in the gas shielded arc welding method according to the present disclosure will be described.

[0048]

[Welding Wire] The form of the welding wire used in the welding method according to the present disclosure is not particularly limited. The welding wire may be a solid wire or a flux-cored wire. The solid wire is a wire-shaped wire having a solid wire cross section. The surface of the solid wire may be or may not be plated with copper, and either form is acceptable.

[0049] The flux-cored wire includes a cylindrical sheath and a flux filled inside the sheath. The flux-cored wire may be of either a seamless type having no seam in the sheath or a seam type having a seam in the sheath. The wire surface (outside of the sheath) of the flux-cored welding wire may be or may not be plated with copper. The material of the sheath is not particularly limited as long as a composition with respect to the total mass of the welding wire can be selected according to the required properties of the welded structure object, and may be a mild steel or a stainless steel.

[0050] Hereinafter, a preferred embodiment of the welding wire that can be used in the present disclosure will be described in detail. When the welding wire shown below is a flux cored wire, the total mass of the welding wire refers to the sum of components in the sheath andtheflux. Examples of the sheath include ordinary steel, SUH409L(JIS G4312:2001), and SUS430, SUS304L, SUS316L, and SUS310S (all defined in JIS G 4305:2012).

[0051] <Cr: 18 mass% or more and 28.5 mass% or less, and Ni: 8.0 mass% or more and 37.0 mass% or less> Cr is a component that improves the corrosion resistance of the weld metal. Ni is a component that stabilizes the austenite structure of the weld metal and improves the toughness at a low temperature, and is a component that is added in a constant amount for the purpose of adjusting the amount of crystallization of the ferrite structure. In the present disclosure, the welding wire is preferably an austenitic stainless steel. It is preferable that both the content of Cr and the content of Ni in the welding wire are within the range specified by JIS Z3321:2013 (Stainless steel rods, wires and strip electrodes for welding) or JIS Z3323:2007 (Stainless steel flux cored wires and rods for arc welding). Specifically, the content of Cr in the welding wire is preferably 18 mass% or more and 28.5 mass% or less with respect to the total mass of the welding wire. The content of Ni in the welding wire is preferably 8.0 mass% or more and 37.0 mass% or less with respect to the total mass of the welding wire.

[0052] Fig. 1 is a DeLong diagram when the vertical axis is nickel equivalent (%) and the horizontal axis is chromium equivalent (%). When the welding wire's chemical composition corresponds to a microstructure having a ferrite percentage of 15.3% or less based on the DeLong diagram shown in Fig. 1 defined by JIS Z3119-2017, it is preferable even when an austenitic base metal is used and hydrogen is contained in the shielding gas, since it is possible to prevent the occurrence of cracks in the weld metal. In the welding wire that can be used in the present disclosure, regions beyond the nickel equivalent and chromium equivalent ranges in the DeLong diagram shown in Fig. 1 shall be extrapolated and applied based on a straight line in the DeLong diagram. It is preferable that the welding wire's chemical composition corresponds to a microstructure consisting only of austenite or a microstructure consisting of austenite and ferrite based on the DeLong diagram and having a ferrite percentage of 15.3% or less since cracks of the weld metal can be further prevented.

[0053] Further, the welding wire that can be used in the present disclosure may contain C, Si, Mn, P, S, Cu, Mo, Nb and N as optional elements in addition to the above Cr and Ni. As described above, the steel grade of the welding wire suitable for combination with the shielding gas according to the present disclosure is an austenitic stainless steel. Therefore, the preferred range of the content of these optional elements is preferably less than or equal to the maximum value of the content of each element specified in JIS Z3321:2013 (Stainless steel rods, wires and strip electrodes for welding) or JIS Z3323:2007 (Stainless steel flux cored wires and rods for arc welding). It is more preferable that the welding wire contains these optional elements and the remainder is Fe and an unavoidable impurity.

[0054] Hereinafter, a more preferred numerical range of the component amount of the welding wire that can be used in the present disclosure will be specifically described together with the reason for the limitation.

[0055] <C: 0.20 mass% or less (including 0 mass%)> C is a component that influences the strength or corrosion resistance of the weld metal. The lower the content of C in the welding wire, the better the corrosion resistance. Therefore, the lower the content of C in the welding wire, the better, and it may be 0 mass%. In order to adjust the mechanical performance of the obtained weld metal, when the welding wire contains C as an optional element, specifically, it is more preferable that the content of C in the welding wire is 0.20 mass% or less with respect to the total mass of the wire.

[0056] <Si: 1.00 mass% or less (including 0 mass%)> Si is an element that is a component that improves the strength of the weld metal, but on the other hand, is also a component that deteriorates the toughness. Therefore, the content of Si in the welding wire may be 0 mass%. In order to adjust the mechanical performance of the obtained weld metal, when the welding wire contains Si as an optional element, specifically, it is more preferable that the content of Si in the welding wire is 1.00 mass% or less with respect to the total mass of the wire.

[0057] <Mn: 4.8 mass% or less (including 0 mass%)> Mn is a component that improves the strength of the weld metal. In the present disclosure, the content of Mn in the welding wire may be 0 mass%. In order to adjust the mechanical performance of the obtained weld metal, when the welding wire contains Mn as an optional element, specifically, it is more preferable that the content of Mn in the welding wire is 4.8 mass% or less with respect to the total mass of the wire.

[0058] <P: 0.03 mass% or less (including 0 mass%)> <S: 0.03 mass% or less (including 0 mass%)> As the content of P and S in the weld metal increases, the crack resistance decreases. Therefore, the smaller the content of P and the content of S in the welding wire, the more preferred, and the P and S may each be 0 mass%. Specifically, each of the content of P and the content of S in the welding wire is preferably 0.03 mass% or less with respect to the total mass of the wire.

[0059] <Cu: 4.0 mass% or less (including 0 mass%)> Cu is a component that improves the strength and corrosion resistance of the weld metal. In the present disclosure, the content of Cu in the welding wire may be 0 mass%. In order to adjust the mechanical performance and corrosion resistance of the obtained weld metal, when the welding wire contains Cu as an optional element or when applying Cu plating to the surface for the purpose of improving electrical conductivity during welding, specifically, it is more preferable that the total content of Cu in the welding wire and plating is 4.0 mass% or less with respect to the total mass of the wire.

[0060] <Mo: 4.0 mass% or less (including 0 mass%)> Mo is a component that improves the hot strength and corrosion resistance, but on the other hand, is also a component that promotes a embrittlement. Therefore, the content of Mo in the welding wire may be 0 mass%. In order to adjust the mechanical performance and corrosion resistance of the obtained weld metal, when the welding wire contains Mo as an optional element, specifically, it is more preferable that the content of Mo in the welding wire is 4.0 mass% or less with respect to the total mass of the welding wire.

[0061] <Nb: 1.0 mass% or less (including 0 mass%)> Nb has the effect of stabilizing C by forming carbides, and is a component that prevents the formation of Cr oxides and improves the corrosion resistance. The carbides referred to here also include a composite compound containing C, such as a carbon sulfide and a carbonitride. On the other hand, when Nb is contained in the welding wire more than necessary, a low melting point compound is generated at the grain boundaries and the crack resistance is deteriorated. Therefore, the content of Nb in the welding wire may be 0 mass% In order to adjust the corrosion resistance of the obtained weld metal, when the welding wire contains Nb as an optional element, specifically, it is preferable that the content of Nb in the welding wire is 1.0 mass% or less with respect to the total mass of the welding wire. As a substitute for Nb, Ti may be contained in the same range as Nb.

[0062] <N: 0.30 mass% or less (including 0 mass%)> N is a component that penetrates the crystal structure and solid-solves to improve the strength and pitting corrosion resistance. On the other hand, N also causes pore defects such as blow holes and pits in the weld metal. Therefore, the content of N in the welding wire may be 0 mass%. In order to adjust the mechanical performance and pitting corrosion resistance of the obtained weld metal, when the welding wire contains N as an optional element, specifically, it is preferable that the content of N in the welding wire is 0.30 mass% or less with respect to the total mass of the welding wire.

[0063] The welding wire that can be used in the gas shielded arc welding method according to the present disclosure contains V, Sn, Na, Co, Ca, Li, Sb, W, and As as the unavoidable impurity, in addition to the above elements. When each element listed as the unavoidable impurity is contained in the welding wire as an oxide, 0 is also contained as an impurity.

[0064]

[Welding Device] Next, a welding device that can be used in the gas shielded arc welding method according to the present disclosure will be described. The welding device is not particularly limited as long as it is a welding device that performs gas shielded arc welding, and a welding device used for gas shielded arc welding in the related art can be used. Examples thereof include a semi-automatic welding device, an automatic welding device using a mobile carriage, and a welding robot system.

[0065] Fig. 2 is a schematic view showing an example of the welding device that can be used in the present disclosure. For example, as shown in Fig. 2, a welding device 1 includes a robot 10 to which a welding torch 11 is attached to the tip and that moves the welding torch 11 along the welding line of a workpiece W, a wire supply unit (not shown) that supplies the welding wire to the welding torch 11, and a welding power supply unit 30 that supplies a current to the consumable electrode via a wire supply unit to generate an arc between the consumable electrode and the material to be welded. In addition, the welding device includes a robot control unit 20 that controls a robot operation for moving the welding torch 11, and a teaching pendant 40 that serves as an interface for inputting a command from the operator to the robot control unit 20.

[0066] Further, various conditions applicable to the gas shielded arc welding method according to the present disclosure will be described in detail.

[0067] (Welding Torch) The position of the welding torch may be perpendicular to or may be tilted with respect to the base metal. In the case of tilting the welding torch toward the opposite side of a welding direction, an angle formed by a vertical line with respect to the base metal and the torch is referred to as a push angle, and in the case of tilting the welding torch toward the welding direction, an angle formed by the vertical line with respect to the base metal and the torch is referred to as a drag angle. By providing a push angle to the welding torch, it is possible to more effectively improve the shielding property during arc welding. By providing a drag angle to the electrode, the rear of the bead can be shielded, so that the oxidation reaction of the bead immediately after welding can be prevented. In the present disclosure, the conditions of the push angle and the drag angle may be changed as necessary in order to obtain proper penetration on the welding line and a good bead shape.

[0068]

<Shielding gas flow rate Q: 10 L/min to 30 L/min> The shielding gas flow rate Q contributes to the shielding property for protecting the molten metal from the atmosphere. When the shielding gas flow rate Q is 10 L/min or more, a sufficient shielding property can be ensured. In addition, when the shielding gas flow rate Q is 30 L/min or less, turbulence in the gas flow is prevented and a stable laminar flowisobtained. Therefore, the shielding gas flow rate Q is preferably 10 L/minto 30 L/min from the viewpoint of ensuring the shielding property, and the shielding gas flow rate Q is more preferably 15 L/min to 25 L/min from the viewpoint of further ensuring the shape and the glossiness of the bead.

[0069] <Wire Extension L: 10 mm to 30 mm> The wire extension L contributes to the shielding property for protecting the molten metal from the atmosphere. When the wire extension L is 30 mm or less, a change in gas composition due to the influence of the atmosphere can be prevented and a sufficient shielding property can be ensured. In addition, when the wire extension Lis 10 mm or more, damage to the contact tip and shield nozzle due to arc heat can be prevented. Therefore, the wire extension L is preferably 10 mm to 30 mm from the viewpoint of ensuring the shielding property and preventing damage to the device, and the wire extension L is more preferably 15 mm to 20 mm from the viewpoint of preventing thermal damage, ensuring long-term weldability, and further ensuring the arc stability, and the shape and the glossiness of the bead.

[0070] <0.5 < shielding gas flow rate Q/wire extension L < 2.2> In the present disclosure, it is preferable to appropriately control the shielding gas flow rate Q and the wire extension L, and to control a ratio of the shielding gas flow rate Q to the wire extension L. When Q/L is 0.5 or more, a more preferred shielding property can be ensured, and when Q/L is 2.2 or less, the gas flow is in a more stable laminar flow state and the arc region can be protected. Therefore, the ratio of the shielding gas flow rate Q to the wire extension L preferably satisfies the following expression (4).

[0071] 0.5 < Q/L < 2.2 (4)

[0072] <Groove Shape and Groove Angle> In the gas shielded arc welding method according to the present disclosure, the groove shape of the welding base metal is not particularly limited, and one of groove shape selected from a single V shape, a single bevel, an I shape, a double bevel, an X shape, a J shape, and a U shape can be used. Further, the groove angle is not limited, and it is preferable that the groove angle is 0° or more since an I-shaped groove shape can be applied. On the other hand, it is preferable that the groove angle is 90° or less since consumption amounts of the welding wire and the shielding gas can be appropriately adjusted. Therefore, the groove angle is preferably 0° to 900.

[0073]

[Structure Object Production Method] The present disclosure also relates to a structure object production method by gas shielded arc welding using the welding wire and the shielding gas whose composition is controlled as described above. It is preferable that the composition of the welding wire is also controlled as described above.

Examples

[0074] Hereinafter, the present disclosure will be described in more detail with reference to Examples. However, the present disclosure is not limited to these Examples, and can be implemented with modifications within the scope that can be adapted to the gist of the present disclosure, and all of them are included in the technical scope of the present disclosure.

[0075] Welding was performed according to the welding test method and welding condition shown below, and the melting performance, shape, glossiness and droplet transfer were evaluated by the methods shown below.

[0076] <Welding test method and welding condition> One-layer, one-pass bead-on-plate welding was performed on a stainless steel base metal using shielding gases having various compositions under various welding conditions. The details of the welding conditions commonly used in Examples of the present disclosure and Comparative Examples are shown in Table 1 below, and the composition of the shielding gas is shown in Table 2 below. The arc length shown in Table 1 was adjusted by photographing the arc using a high-speed video camera and appropriately changing a voltage adjustment volume of the welding power supply to be 6 mm which was the reference length. An appropriate filter was applied to the lens of the high-speed video camera used such that arc light could be observed. The arc stability was evaluated by observing the droplet transfer during welding, and the melting performance, the shape and the glossiness were evaluated by observing the beads obtained by welding as a sample. The measurement methods and the evaluation criteria for each evaluation method are shown in Tables 3 to 9 below. Welding conditions other than those shown in Table 1 below are shown in Table 10 below, and the evaluation results are shown in Table 11 below.

[0077]

[Table 1] Welding method Automatic (using mobile carriage) Welding position Flat welding, bead-on-plate Polarity DC-EP (pulse) Wire diameter 1.2 mm Arc length 6 mm Welding speed 30 cm/min Welding wire YS308LSi (JIS Z3321:2013) SUS304L (JIS G4304:2012) Base metal 12 mm x 80 mm x 300 mm

CI5 I

A C- 000 m f kf) c~f

Cd

[0079]

[Test method and evaluation criteria] <Melting performance test method when welding current is 100 A> A low current welding condition with a welding current of 100 A is a condition usually applied to difficult welding positions such as vertical welding and overhead welding. Welding in such a position usually involves a very slow travel speed, so that the welding heat input is high, and thus lack of fusion defects are unlikely to occur. In Examples, simply flat welding was used.

[0080] <Melting performance evaluation criteria when welding current is 100 A> The melting performance was evaluated by measuring the bead width and the bead height and calculating a ratio of the bead width to the bead height (bead width/bead height). When the welding current was 100 A, if the value obtained by (bead width/bead height) was 2.3 or more, it was determined that the occurrence of lack of fusion can be prevented even when performing groove welding, which was evaluated to be passed.

[0081] <Melting performance test method when welding current is 150 A> A high current welding condition with a welding current of 150 A is a condition applied to flat welding and the bead shape obtained in this test is important.

[0082] <Melting performance evaluation criteria when welding current is 150 A> Similar to the case of a welding current of 100 A, the melting performance was evaluated by measuring the bead width and the bead height and calculating a ratio of the bead width to the bead height (bead width/bead height). When the welding current was 150 A, if the value obtained by (bead width/bead height) was 3.3 or more, it was determined that the occurrence of lack of fusion can be prevented, which was evaluated to be passed. The evaluation methods are shown in Table 3 below. The bead width and the bead height were measured with a caliper.

[0083] When the flank angle is 900 or more, which is shaped like a fillet joint in the welding of the next pass, it is possible to melt the weld toe to prepare a joint without lack of fusion. Therefore, with a margin, when the value obtained by (bead width/bead height) is within the above range as a range in which defects can be prevented, it is evaluated to be passed.

[0084]

[Table 3] Evaluation Measurement item Test (measurement) method and evaluation criteria item Bead width at three typical points in bead is Bead width (mm) measured with caliper, and median value is adopted. Sum of base metal height and bead height at three

typical points in bead is measured, bead height is Bead height (mm) Melting calculated by subtracting plate thickness, and performance median value is adopted. 2.3 or more: passed (A) Bead width Welding current: 100 A Less than 2.3: failed (D) (mm)/bead height 3.3 or more: passed (A) (mm) Welding current: 150 A Less than 3.3: failed (D)

[0085] <Evaluation and test method and evaluation criteria for shape property> Regarding the shape property, sensory evaluation was performed both when the welding current was 100A and when the welding current was 150 A. The shape property at each welding current was evaluated on a 5-point scale from 1 to 5, and the total of the shape property score when the welding current was 100 A and the shape property score when the welding current was 150 A was used as comprehensive evaluation. The evaluation criteria for shape property are shown in Table 4 below, and the evaluation criteria for comprehensive evaluation of shape property are shown in Table 5 below.

[0086]

[Table 4] Evaluation item Score Evaluation criteria State where bead toe is all in linear shape and can be 5 determined to have very good shape property 4 State between scores 3 and 5 State where bead toe is partially in wavy shape, and 3 difference between largest width and smallest width is about 0.5 mm or less State where toe is almost all in wavy shape, and difference Shape property between largest width and smallest width is about 0.5 mm or less 2 or state where toe is partially in wavy shape, and difference between largest width and smallest width is more than about 0.5 mm State where toe is almost all in wavy shape, and difference 1 between largest width and smallest width is more than about 0.5 mm

[0087]

[Table 5] Evaluation item Score Evaluation Comprehensive 6 to 10 A evaluation of 3 to 5 B shape property 1 to 2 C

[0088] <Evaluation and test method and evaluation criteria for glossiness> Regarding the glossiness, sensory evaluation was performed both when the welding current was 100 A and when the welding current was 150 A. The glossiness at each welding current was evaluated on a 3-point scale from 1 to 3, and the total of the glossiness score when the welding current was 100 A and the glossiness score when the welding current was 150 A was used as comprehensive evaluation. The evaluation criteria for glossiness are shown in Table 6 below, and the evaluation criteria for comprehensive evaluation of glossiness are shown in Table 7 below.

[0089]

[Table 6] Evaluation item Score Evaluation criteria Bead has silver color on entire surface, and has metallic 3 luster. Glossiness 2 Bead is lightly dull on entire surface, and has whitish color.

and is covered with 1 Bead has grey color on entire surface, oxide film.

[0090]

[Table 7] Evaluation item Score Evaluation Comprehensive 5 to 6 A evaluation of 3 to 4 B glossiness 1 to 2 C

[0091] <Evaluation and test method and evaluation criteria for droplet transfer> Regarding the droplet transfer, observation with a high-speed video camera was performed at both when the welding current was 100 A and when the welding current was 150 A. The droplet transfer at each welding current was evaluated on a 3-point scale from 1 to 3. In addition, comprehensive evaluation for the arc stability was performed based on the total of the droplet transfer score when the welding current was 100 A and the droplet transfer score when the welding current was 150 A. The evaluation criteria for droplet transfer are shown in Table 8 below, and the evaluation criteria for comprehensive evaluation of arc stability are shown in Table 9 below.

[0092]

[Table 8] Evaluation item Score Evaluation criteria 3 Generally, one-pulse one-drop spray transfer. Most of time plural-pulse one-drop, or liquid column of wire

2 tip is elongated to be in contact with molten pool so that Droplet transfer short circuit occurs frequently.

larger than 1 Globule transfer in which drop having diameter wire diameter grows and ttransfers.

[0093]

[Table 9] Evaluation item Score Evaluation Both 3 A Comprehensive Both 2 or more, and evaluation of arc B total of 4 to 5 stability Either one is 1 D

[0094]

[Evaluation results] As shown in Table 10 to Table 12 below, since in Test Nos. Ti to T13, the composition of the shielding gas is within the range of the present disclosure, and the expression (1) and the expression (2) obtained by the content of C02 and the content of H2 are satisfied, excellent results are obtained in all of the items of melting performance, arc stability, shape property, and glossiness.

[0095]

[Table 10] Welding condition

Test No. SapeShielding gas flow Wire Extension L Welding No. Gas No. Q/L rate Q(L/min) (mm) current (A)

Al1 100 T1 15 1.66 Bi1 150

A2 100 12 12 2.08 B2 150 __________ ________ 25 _____ ______ A3 100 13 20 1.25 B3 150 ______ _____ ~Gi I_______ A4 100 14 25 1.00 B4 150

A5 100 15 15 1.00 B5 150

A6 100 16 10 0.67 B6 150

A7 100 Example 17 G3 B7 150

A8 100 18 - G4 B8 150

A9 100 19 - G5 15 B9 150

AlO 100 110 G6 25 1.66 BlO 150

All 100 111 G8 Bll 150

A12 100 112 - G9 B 12 150

A13 100 113 - G12 B 13 150

A14 100 114 - G2 B 14 150

A15 100 115 - G7 B15 150

Comparative A16 100 116 - GIO 25 15 1.66 Example B 16 150

A17 100 117 - Gil B 17 150

A18 100 118 G13 B8 150

[0096]

[Table11 ] Measurement result Arc voltage

Sam averag Bead TetN. pe Gas e value Bead Bead width/b Droplet Shape Gljsi Total Total Teto..~ No. (V) at width height ead transfer propert e shape Glossi

arc (mm) (mm) height state y property ness length (mm) of 1 6 mm IIII Al 24 8.2 2.2 3.8 3 2 3 TI 3 5 BI 26 13.6 2.6 5.2 3 1 2 A2 22 7.2 2.8 2.6 3 1 2 T2 4 4 B2 25 13.1 3.0 4.3 3 3 2 A3 24 7.8 2.8 2.7 3 3 3 T3 -6 5 B3 28 13.2 3.3 4.0 3 3 2 - GI A4 25 10.2 2.7 3.8 2 3 2 T4 4 3 B4 28 13.2 3.4 3.9 2 1 1

T5 A5 24 7.6 2.5 3.0 3 3 3 6 5 B5 26 14.1 2.9 4.9 3 3 2 A6 24 7.3 2.4 3.0 3 1 2 T6 -5 3 B6 26 10.9 2.5 4.3 3 4 1

Exml 7 A7 G3 24 6.8 2.6 2.6 3 4 3 6 5 B7 28 10.8 2.7 4.1 3 2 2 A8 24 6.9 2.9 2.4 3 1 3 T8 - G4 -2 5 B8 26 12.6 2.6 4.9 3 1 2

T9_A9 G5 22 9.2 2.4 3.8 3 3 3 6 5 B9 24 12.2 3.2 3.8 2 3 2 AlO 2 6.6 2.6 2.5 2 1 2 TlO - G6 5 4 BlO 25 11.5 3.0 3.9 2 4 2 All 22 8.3 2.5 3.3 3 2 2 Tll - G8 -5 3 Bll 24 12.9 2.6 5.0 3 3 1 A12 22 8.6 3.1 2.8 3 4 2 T12 - G9 - 6 3 B12 24 11.6 3.0 3.9 3 2 1 A13 22 7.3 3.0 2.5 3 3 3 T13 - G12 -8 4 B13 24 10.0 3.0 3.3 3 5 1

T4 A14 G2 24 8.6 2.8 3.0 3 3 3 5 5 B14 30 11.1 3.1 3.6 1 2 2

T5 A15 G 22 6.7 3.1 2.2 3 2 2 5 3 24 12.7 2.9 4.4 3 3 1 CmaaBlS5 CmaaA16 20 7.3 3.1 2.4 3 5 2 tive T16 - GIO -9 3 EapeB16 24 10.9 3.4 3.2 3 4 1

T7 A17 GI 22 6.7 3.0 2.2 3 3 3 8 4 B17 24 9.9 3.3 3.0 3 5 1 A18 21 5.2 3.6 1.4 2 2 2 T18 - G13 - 7 3 B18 23 10.1 3.1 3.3 2 5 1

[0097]

[Table 12] Comprehensive evaluation Test No. Gas No. Melting Arc Shape Glossiness performance stability property TI A A B A T2 A A B B T3 A A A A GI T4 A B B B T5 A A A A T6 A A B B Example T7 G3 A A A A T8 G4 A A C A T9 G5 A B A A TIO G6 A B B B T1l G8 A A B B T12 G9 A A A B T13 G12 A A A B T14 G2 A D B A T15 G7 D A B B Comparative T16 G1O D A A B Example T17 G11 D A A B T18 G13 D B A B

[0098] Fig. 3 is a photograph substituted for drawing showing a cross section of a weld metal in Sample No. Bi in Test No. T (welding current: 150 A). Fig. 3 shows an example in which the melting performance test is passed. In Test No. Ti (Sample No. B1), the welding current is 150 A, the value obtained by (bead width/bead height) is 5.2, and the flank angle is 1550. In welding in which such a smooth bead toe is formed, it is determined that the resistance to the lack of fusion defect is extremely good.

[0099] Similar to Test No. TI, in Test Nos. T2 to T13, excellent melting performance can beobtained. Among Test Nos. TI to T6 using Gas No. GI, particularly Test Nos. TI to T3,

T5, and T6, since the wire extension L is in the more preferred range of the present disclosure, excellent arc stability can be obtained without changing the gas composition due to the influence of the atmosphere.

[0100] Among Test Nos. T7 to T13 using different gases, in Test Nos. T7, T8, T11, and T12, since the value obtained by the expression (2) using the contentof C02and the content of H2 in the shielding gas is more than a more preferred lower limit value of the present disclosure, excellent arc stability can be obtained. In Test No. T13, since the contentof CO2 in the shielding gas is within the range of the present disclosure and is a high value, excellent arc stability can be obtained.

[0101] On the other hand, in Test No. T14, since the content of H2 in the shielding gas is more than the upper limit of the range of the present disclosure and is also more than the upper limit specified in the expression (1) and the expression (2) obtained by the content of CO2and the content of H2, the arc stability is low.

[0102] In Test No. T15, since the contentof C02 in the shielding gas is less than the lower limit of the range of the present disclosure and is more than the upper limit specified in the expression (2) obtained by the contentof C02and the content of H2, the melting performance is low.

[0103] In Test No. T16, since the content of H2 in the shielding gas is less than the lower limit of the range of the present disclosure and is less than the lower limit specified in the expression (1) and the expression (2) obtained by the contentof C02and the content of H2, the melting performance is low.

[0104] Fig. 4 is a photograph substituted for drawing showing a cross section of a weld metal in Sample No. B16 in Test No. T16 (welding current: 150 A). Fig. 4 shows an example in which the melting performance testis failed. In Test No. T16 (Sample No. B16), the welding current is 150 A, the value obtained by (bead width/bead height) is 3.2, and the flank angle is 125°. In the case of performing the next welding pass after such a bead toe is formed, when the arc does not hit the toe, a lack of fusion defect may occur. Therefore, it is determined as failed as a determination with a margin.

[0105] In Test No. 17, since the content of C02 in the shielding gas is more than the upper limit of the range of the present disclosure and is less than the lower limit specified in the expression (2) obtained by the content of C02 and the content of H2, the melting performance is low.

[0106] In Test No. 18, since the content of H2 in the shielding gas is less than the lower limit of the range of the present disclosure and is less than the lower limit specified in the expression (1) and the expression (2) obtained by the content of C02 and the content of H2, the melting performance is low.

[0107] Fig. 5 is a photograph substituted for drawing showing a bead appearance in a test plate welded by the method according to the present disclosure. Fig. 6 is a photograph substituted for drawing showing a cross section of the weld metal in the test plate shown in Fig. 5. The test plate shown in Fig. 5 and Fig. 6 is made by using SUS304L having a plate thickness of 12 mm as a welding base metal, setting the groove angle to 45, and applying the conditions in the above Test No. Ti to the vertical welding of 3 layers and 3 passes. As shown in Fig. 5 and Fig. 6, the joint obtained by the method according to the present disclosure can have sufficient penetration and a smooth bead shape.

[0108] Although various embodiments have been described above with reference to the drawings, it is needless to say that the present disclosure is not limited to these examples. It will be apparent to those skilled in the art that various changes and modifications may be conceived within the scope of the claims. It is also understood that the various changes and modifications belong to the technical scope of the present disclosure. Constituent elements in the embodiments described above may be combined freely within a range not departing from the spirit of the present disclosure.

[0109] The present application is based a Japanese patent application (Japanese patent application No. 2020-111997) filed on June 29, 2020, contents of which are incorporated by reference in the present application.

REFERENCES SIGNS LIST

[0110] 1 welding device 10 robot 11 welding torch 20 robot control unit 30 welding power supply unit 40 teaching pendant

Claims

CLAIMS 1. A gas shielded arc welding method comprising welding a base metal while flowing a shielding gas to a weld region in the base metal using a welding wire as an electrode, wherein the shielding gas contains, with respect to a total volume of the shielding gas, C02: 0.6 vol% or more and 2.0 vol% or less, and H2: 0.5 vol% or more and 3.0 vol% or less,

with the remainder being Ar and an unavoidable impurity, and the following expression (1) and expression (2) are satisfied, 1.56 < [C02]+[H2] < 4.40 (1) 0.35 < [H2]/([CO2]+[H2]) < 0.74 (2) wherein the content of C02 with respect to the total volume of the shielding gas is

[C0 2 ] in vol% and the content of H2 with respect to the total volume of the shielding gas is

[H2] in vol%.
2. The gas shielded arc welding method according to claim 1, wherein the following expression (3) is satisfied, 57.0 < 0.5x[Ar]+1.5x[CO2]+10x[H2] < 80.0 (3) wherein the content of Ar with respect to the total volume of the shielding gas is

[Ar] in vol%.
3. The gas shielded arc welding method according to claim 1 or 2, wherein the welding wire contains, with respect to a total mass of the welding wire, Cr: 18 mass% or more and 28.5 mass% or less, and Ni: 8.0 mass% or more and 37.0 mass% or less, and the welding wire's chemical composition corresponds to a microstructure having a ferrite percentage of 15.3% or less based on a DeLong diagram.
4. The gas shielded arc welding method according to claim 3, wherein the welding wire contains, with respect to the total mass of the welding wire, C: 0.20 mass% or less (including 0 mass%), Si: 1.00 mass% or less (including 0 mass%), Mn: 4.8 mass% or less (including 0 mass%),

P: 0.03 mass% or less (including 0 mass%), S: 0.03 mass% or less (including 0 mass%), Cu: 4.0 mass% or less (including 0 mass%), Mo: 4.0 mass% or less (including 0 mass%), Nb: 1.0 mass% or less (including 0 mass%), and N: 0.30 mass% or less (including 0 mass%).
5. The gas shielded arc welding method according to claim 1 or 2, wherein the weld region in the base metal has a groove, the groove has one of groove shape selected from a single V shape, a single bevel, an I shape, a double bevel, an X shape, a J shape, and a U shape, and the groove has a groove angle of 0° to 90.
6. The gas shielded arc welding method according to claim 1 or 2, wherein a gas flow rate Q of the shielding gas is 10 L/min to 30 L/min, a wire extension L is 10 mm to 30 mm, and a ratio of the gas flow rate Q (L/min) to the wire extension L (mm) satisfies the following expression (4), 0.5 < Q/L < 2.2 (4).
7. A structure object production method by gas shielded arc welding using a welding wire and a shielding gas, wherein the shielding gas contains, with respect to a total volume of the shielding gas, C02: 0.6 vol% or more and 2.0 vol% or less, and H2: 0.5 vol% or more and 3.0 vol% or less,

with the remainder being Ar and an unavoidable impurity, and the following expression (1) and expression (2) are satisfied, 1.56 < [C02]+[H2] < 4.40 (1) 0.35 < [H2]/([CO2]+[H2]) < 0.74 (2) wherein the content of C02 with respect to the total volume of the shielding gas is

[C0 2 ] in vol% and the content of H2 with respect to the total volume of the shielding gas is

[H2] in vol%.