Abstract: A joint structure, includes: a first member including a high tensile strength steel; and a second member including a high tensile strength steel and superposed on the first member, the first member and the second member being resistance welded to each other, in which a gap between the first member and the second member is between 0 mm and 3 mm, a nugget is not formed at a joint portion between the first member and the second member, or when the nugget is formed at the joint portion between the first member and the second member, a diameter D1 of the nugget satisfies D1<5 mm, and a decarburized layer is provided on at least one of a superposition surface of the first member, on which the second member is superposed, and a superposition surface of the second member, on which the first member is superposed.

Abstract: A joint structure formed by resistance welding a plurality of superposed steel sheets includes a high tensile strength steel sheet having a tensile strength of at least 590 MPa and containing a chemical component having a carbon equivalent Ceq of at least 0.53%. The high tensile strength steel sheet has a decarburized layer between a base plate and a galvanized layer formed on at least one of a surface on a superposition surface side and a surface on a welding electrode side of the high tensile strength steel sheet, or has a decarburized layer on a superposition surface of the high tensile strength steel sheet adjacent to a galvanized layer of a galvanized steel sheet to be superposed. The decarburized layer has a thickness of at least 5 ?m and at most 200 ?m, and the carbon equivalent Ceq is a value defined by a formula: Ceq=C+Si/24+Mn/6.

Abstract: A joint structure, includes: a first member including a high tensile strength steel; a second member including a high tensile strength steel and superposed on the first member; a surface soft layer formed on at least one of a superposition surface of the first member, on which the second member is superposed, and a superposition surface of the second member, on which the first member is superposed; a molten-solidified portion formed by melting and solidifying the first member and the second member; and a heat affected zone formed around the molten-solidified portion, in which the surface soft layer has a total thickness of 5 ?m to 200 ?m, and the molten-solidified portion has a carbon amount of 0.21 mass % or more, and a maximum Vickers hardness of the surface soft layer in the heat affected zone is 100 Hv to 500 Hv.

Abstract: Provided is a welding method using a special torch and a flux cored wire, in which the special torch has a suction nozzle between the contact tip and the shield nozzle, and the flux cored wire has a flux filled inside the steel outer casing, and a seam portion where both ends of a metal in a width direction of the steel outer casing are butted or overlapped in a longitudinal direction of the flux cored wire.

Abstract: A welding method for joining a first plate made of a material other than steel and a second plate made of steel includes a step of making a hole through each of the first plate and the second plate, a press-fitting step, an overlapping step, and a filling and welding step. A shaft portion of a joining assist member being solid, being made of steel, and having an outer shape with step having the shaft portion and a flange portion is press-fitted in the hole of the first plate. The first plate and the second plate is overlapped such that the shaft portion faces the hole of the second plate. The hole of the second plate is filled with a weld metal and the second plate and the joining assist member are welded.

Abstract: The present invention relates to a method for manufacturing a joint structure of dissimilar materials. The method includes forming a low-temperature thermal spray coating on at least a part of a surface of an aluminum or aluminum alloy material by low-temperature thermal spraying a metal powder of at least one metal selected from the group consisting of ferritic stainless steel, austenitic stainless steel, and ferritic and austenitic two-phase stainless steel, overlapping the aluminum or aluminum alloy material and a steel material such that the low-temperature thermal spray coating and the steel material face each other, and joining the low-temperature thermal spray coating and the steel material by a laser welding from a steel material side.

Abstract: A joint structure is formed by joining a first plate-shaped member made of steel and a second plate-shaped member made of steel that is overlapped on the first plate-shaped member and that is formed in a long shape. A surface of the first plate-shaped member and both edge portions of the second plate-shaped member along a longitudinal direction are joined by a weld metal.

Abstract: The present invention relates to a method for joining a plated steel sheet, in which at least one of a first steel sheet and a second steel sheet is a plated steel sheet, and the first and second steel sheets overlapped with each other are subjected to an arc spot welding. The method includes press-working the first steel sheet into a desired shape and at the same time forming a linear groove on an overlapping surface with the second steel sheet of the first steel sheet, overlapping the first and second steel sheets, and setting a welding torch with the groove as a target position, and performing the arc spot welding so as to overlap the groove when viewed from a direction perpendicular to the overlapping surface.

Abstract: Provided is a manufacturing method for a joint body having a blank material plated with a metal material and a hoop material plated with a metal material joined together by placing the hoop material on the blank material and causing a laser oscillation system to irradiate a surface of the hoop material with laser light to form a joint portion including a line-shaped welded portion where the blank material and the hoop material are joined together. In this manufacturing method, the hoop material is supplied to be placed on the blank material and form a predetermined gap d between the blank material and the hoop material, and the hoop material is irradiated with a laser at a position where the predetermined gap d is located between the blank material and the hoop material to join the blank material and the hoop material together by laser welding.

Abstract: A gas-shielded arc welding method includes feeding a consumable electrode via a welding torch and performing welding while flowing a shielding gas. The welding torch includes a nozzle. An inner diameter of the nozzle is 15 mm or more. A nozzle-base material distance between a tip of the nozzle and a material to be welded is 22 mm or less. A ratio expressed by (the inner diameter of the nozzle/the nozzle-base material distance) is 0.7 or more and 1.9 or less.

Abstract: The present invention relates to an arc welding method for dissimilar material joining for joining a first plate made of an aluminum alloy or a magnesium alloy and a second plate made of steel. A steel-made joining assist member has a stepped external shape including a large-diameter portion and a small-diameter portion, has a hollow portion formed to penetrate the large-diameter portion and the small-diameter portion, and has a total height of the large-diameter portion and the small-diameter portion being equal to or larger than a thickness of the first plate. A pressure is applied to the joining assist member to punch the first plate. The hollow portion of the joining assist member is filled with a weld metal. The weld metal is melted until a penetration bead is formed on the second plate, to weld the second plate and the joining assist member together.

Abstract: A manufacturing method for a joint body having a first metal member and a second metal member joined together by causing a laser oscillation system to irradiate a surface of the second metal member placed on the first metal member with laser light to form a joint portion including a welded portion where the first metal member and the second metal member are joined together includes continuously supplying the second metal member while pressing the second metal member against the first metal member, the second metal member being a hoop material, and causing the laser oscillation system to emit the laser light.

Abstract: The present invention pertains to: a method for arc spot welding a steel plate having a carbon equivalent CeqBM of 0.35 or more (the carbon equivalent CeqBM is defined in the specification), the method being characterized in that a welding wire containing 98.5 mass % or more of Fe is used, and the ratio between the carbon equivalent CeqWM of a weld metal formed by the method (the carbon equivalent CeqWM of the weld metal is defined in the specification) and the carbon equivalent CeqBM of the steel plate, CeqWM/CeqBM is 0.2-1.0. According to the arc spot welding method, brittle fracture can be prevented and high joint strength can be obtained even when the C content in the steel plate is high.

Abstract: Provided is a manufacturing method for a joint body having a first metal member and a second metal member joined together by welding. With a density of the welding set higher than a density of the welding of other portions, the second metal member is bent within a plane by changing a positional relation of the second metal member relative to the first metal member in plan view.

Abstract: The purpose of the present invention is to provide a flux cored wire which has good high-temperature cracking resistance, and which enables the achievement of a welded part exhibiting excellent coating adhesion. The present invention relates to a metal flux cored wire for gas-shielded are welding, which contains, relative to the total mass of the wire, 0.02-0.30% by mass of C, 0.3-1.5% by mass of Si, 0.3-2.5% by mass of Mn, and oxide of at least one element selected from the group consisting of Si, Cr and Ni in an amount of 0.01-0.30% by mass in total, 0.020% by mass or less of S, and 0.3% by mass or less of Al, Ca, Mg, K and Na in total in the form of metals or alloys, with the balance made up of Fe and unavoidable impurities.

Abstract: A method for welding a galvanized steel sheet includes utilizing a pulse welding of repeatedly applying a pulse peak current and a base current, setting a welding speed to 100 cm/min or less, and using a shielding gas in which 1 vol % or more and 10 vol % or less of at least either one of CO2 and O2 is added to Ar. The pulse peak current has a pulse peak time being in a range of 7% or more and less than 50% of one period depending on a sheet thickness of the galvanized steel sheet.

Abstract: A joint body includes first and second metal members and a joint portion including a welded portion where the first and second metal members are joined together, the welded portion having a line shape. The joint portion includes first and second longitudinal portions and a plurality of connecting portions. The first longitudinal portion has first intersecting portions arranged in a first direction and extends in the first direction. The second longitudinal portion has second intersecting portions arranged in the first direction and extends in the first direction. The welded portion intersects itself at the first and second intersecting portions. The connecting portions are arranged in the first direction. The connecting portions extend in a first direction and connect the first and second longitudinal portions.

Abstract: A plurality of welding torches, which are disposed in a welding device and are made movable in three-dimensional directions, are provided with welding wires that differ in composition and diameter from each other. When welding is performed in the horizontal direction, an arc is generated by at least two of the welding torches to form a bead while the welding wires are being fed. When welding is performed in the vertical direction, the arc is generated by any one welding torch of the two welding torches to form a bead while the welding wire is being fed. Thus, a steel sheet to which an anti-corrosion material has been applied can be welded continuously with high quality and high-efficiency in a horizontal orientation and vertical orientation.

Abstract: The present invention relates to a method for arc-welding a steel plate having a C content of 0.08-0.30% by mass, wherein the arc welding method comprises welding under a condition whereby X represented by formula (1) is 200 or less using a welding wire in which the total content of Cr and Ni thereof is 1.00% by mass or greater. (1): X=0.8×(300-279[C]W-25[Si]W-35[Mn]W-49[Ni]W-47[Cr]W-61[Mo]W) +0.2×(300-279[C]BM-25[Si]BM-35[Mn]BM-49[Ni]BM-47[Cr]BM-61[Mo]BM) (where [C]W, [Si]W, [Mn]W, [Ni]W, [Cr]W, [Mo]W, [C]BM, [Si]BM, [Mn]BM, [Ni]BM, [Cr]BM, and [Mo]BM are defined in the specification).

Abstract: A steel plate frame and a thin plate are made of different materials. A plurality of through holes are formed in a portion of the thin plate to be placed on the steel plate frame. A plurality of projections 6c are formed on a support plate, each of the projections being allowed to be inserted into a corresponding one of the through holes. An adhesive is applied to a portion of the steel plate frame on which the thin plate is placed. The thin plate is placed on the steel plate frame, and the steel plate frame and the thin plate are bonded together by the adhesive. The support plate is placed on the thin plate to insert the projections into the through holes. The projections and the steel plate frame are welded to form a plurality of welded spots.