Abstract: In a tandem gas-shielded arc welding method, carbon dioxide is used as a shielding gas for a leading electrode formed by a solid wire, an argon-carbon dioxide gas mixture containing at least 60% by volume of argon gas is used as a shielding gas for a trailing electrode formed by a solid wire or a flux-cored wire, both the leading electrode and the trailing electrode have a reverse polarity, the leading electrode satisfies the relationships “5.00?(I·V·10?8)/(Wf·?r2)?10.00” and “(I2·10?3)/V?4.50”, and the trailing electrode satisfies the relationships “4.00?(I·V·10?8)/(Wf·?r2)?7.00” and “(I2?10?3)/V?8.00”.

Abstract: The purpose of the present invention is, in gas shielded arc welding using an active gas and flux-cored wire with primer-coated steel plates as a base material, to suppress occurrences of poor appearance in welded parts caused by pores originating in the primer. A welding method for a welded article positions a first steel plate and a second steel plate formed from primer-coated steel plates in a T shape and welds each of corner parts formed in two locations.

Abstract: Arc welding is performed with a flux-cored welding wire using pure Ar shielding gas with a pulsed current having a peak current of 340 to 540 A and a peak current time of 0.7 to 2.5 ms as a welding current, in which the wire includes a carbon-steel sheath and contains, on a mass percent basis, 0.02% to 0.15% C, 0.30% to 1.50% Si, 0.70% to 2.30% Mn, 0.010% to 0.100% S, 0.01% to 0.18% Ti, 0.030% or less P, and 0.15% or less Cr, with respect to the total mass of the wire, in which the wire has a flux content of 10.0% to 30.0%, the flux has a S content of 0.030% to 0.600%, and the wire satisfies [Sf]>([Sh]+0.010), where [Sf] represents the S content (%) of the flux, and [Sh] represents the S content (%) of the sheath.

Abstract: Disclosed is a steel sheet, containing: Si: 0.20-2% (the term “%” herein means “mass %”, the same is true hereinbelow), Mn: 1-2.5%, a total mass of Si and Mn being 1.5% or more, and O: 0.002% or less (exclusive of 0%), C: 0.02-0.25%, P: 0.1% or less (exclusive of 0%), S: 0.05% or less (exclusive of 0%), Al—0.02-0.2%, and N: 0.0015-0.015%. The steel sheet of the invention can be advantageously used for forming wide beads even in high-speed arc welding of 100 cm/min or higher.

Abstract: In consumable-electrode gas-shield arc welding, carbon dioxide gas is used as shield gas; the molten pool is formed using a pulsed arc as a leading electrode arc transferring one droplet per cycle by alternately outputting, in each cycle, pulses of two different pulse waveforms of which a pulse peak current level and/or a pulse width per period differ; the conductively heated filler wire is inserted into the molten pool as a trailing electrode; the distance between a tip of the filler wire inserted into the molten pool and a conductive point of the filler wire is set within a range of 200×10?3 to 500×10?3 m; and a leading-electrode base current value is set larger than a trailing-electrode filler current value. According to such a method, even when inexpensive carbon dioxide gas is used as shield gas, the amount of spatter can be reduced, and high weldability can be achieved in multipass welding.

Abstract: A welding tip replacement apparatus is used for a welding torch that includes a tubular tip connection body, a tubular retaining member fitted over the tip connection body, and a tubular welding tip fitted within the tip connection body, the welding torch being configured such that displacing the retaining member toward the proximal end of the tip connection body along the axis of the tip connection body causes the welding tip axially fastened to the tip connection body to be released. The apparatus includes a first grasping mechanism grasping the retaining member, a second grasping mechanism grasping the welding tip protruding from the retaining member in a direction away from the distal end of the tip connection body, a first driving mechanism driving the first grasping mechanism axially, and a second driving mechanism driving the second grasping mechanism axially.

Abstract: A solid wire is for gas-shielded arc welding, using a shielding gas, and for galvanized steel sheet welding. The solid wire comprises, to the mass of the whole of the solid wire, predetermined amount of C, Si, Mn, P, S, O, and Cr, with the balance consisting Fe and inevitable impurities. The solid wire satisfies “1.0?(percentage by mass of Si+that by mass of Mn)/{100(that by mass of S+that by mass of O}?4.0” and “0.50?percentage by mass of Mn/that by mass of Si?2.00”. The shielding gas is an Ar gas comprising 25 to 40% of CO2 gas. It is achieved to improve spatter-decreasing performance and pore-resisting performance (performance of restraining the generation of porosity defects, such as pits and blowholes).

Abstract: In a two-electrode welding method of the present invention, a leading electrode is used to perform gas-shielded arc welding and a trailing electrode is an energized filler. A trailing electrode wire protrudes from a guide lead or guide tip and is energized from an energizing tip. The distance between a welding surface and the energizing tip is 100 mm or more and 1500 mm or less. The distance between electrodes is 10 mm or less. The electric current of the leading electrode is 250 A or more, and the electric current of the trailing electrode is 10 A or more and 50% or less of the electric current of the leading electrode. The feeding speed of the trailing electrode wire is 20% or more and 50% or less of the feeding speed of the leading electrode wire.

Abstract: An arc welding apparatus includes a lifting motor. A speed adjustment circuit controls the lifting motor such that the rising speed of the welder decreases if a current of the welding power source is smaller than a set value, or increases if the value of the current is larger than the set value. A voltage adjustment circuit controls the welding power source such that the voltage increases if the number of times that the voltage falls below a determination voltage is larger than a set number of times or if periods for which the voltage remains below the determination voltage are longer than a set time, or decreases if the number of times that the voltage falls below a determination voltage is smaller than a set number of times or if periods for which the voltage remains below the determination voltage is shorter than a set time.

Abstract: A solid wire contains in mass percent C 0.005 to 0.080%, Si 0.30 to 1.20%, Mn 1.15 to 1.65%, S 0.050 to 0.200%, P 0.017% or less, O 0.0070% or less, and N 0.0050% or less, wherein C+(P*5)?0.135 mass percent is satisfied, and the remainder includes Fe and impurities, and the content of each of Ti, B, Cr, Ni, Nb, V, Zr, La and Ce as the impurities is controlled to be a certain content or less, and the amount of adhered oil on a surface of the relevant solid wire is controlled to be 1.2 g or less per wire of 10 kg. According to such a configuration, while increase in welding cost is controlled to the minimum, stability of wire feed, burn-through resistance, undercut resistance, and crack resistance becomes excellent, slag and spatter becomes hard to be generated, hardness of weld metal becomes equal to or higher than that of base metal, and brittle fracture becomes hard to occur.

Abstract: A welding tip replacement apparatus is used for a welding torch that includes a tubular tip connection body, a tubular retaining member fitted over the tip connection body, and a tubular welding tip fitted within the tip connection body, the welding torch being configured such that displacing the retaining member toward the proximal end of the tip connection body along the axis of the tip connection body causes the welding tip axially fastened to the tip connection body to be released. The apparatus includes a first grasping mechanism grasping the retaining member, a second grasping mechanism grasping the welding tip protruding from the retaining member in a direction away from the distal end of the tip connection body, a first driving mechanism driving the first grasping mechanism axially, and a second driving mechanism driving the second grasping mechanism axially.

Abstract: In a two-electrode welding method of the present invention, a leading electrode is used to perform gas-shielded arc welding and a trailing electrode is an energized filler. A trailing electrode wire protrudes from a guide lead or guide tip and is energized from an energizing tip. The distance between a welding surface and the energizing tip is 100 mm or more and 1500 mm or less. The distance between electrodes is 10 mm or less. The electric current of the leading electrode is 250 A or more, and the electric current of the trailing electrode is 10 A or more and 50% or less of the electric current of the leading electrode. The feeding speed of the trailing electrode wire is 20% or more and 50% or less of the feeding speed of the leading electrode wire.

Abstract: A welding torch includes: a first tip body to which a welding wire, gas, and current having passed through a torch body is supplied; a first tip provided at a distal end of the first tip body to supply electric current having passed through the first tip body to the welding wire; an insulating bushing provided inside the nozzle, on the outer periphery of the first tip body; a second tip body to which electric current from a power source is supplied; and a second tip provided at the distal end of the second tip body to supply the current having passed through the second tip body to the welding wire. The first tip and the second tip are axially arranged at a predetermined distance and supply electric current to the welding wire.

Abstract: A welding torch includes a tip connection body, a holding member, a fixing member, and a welding tip. The holding member is displaceable in the axial direction of the tip connection. The fixing member fixes the welding tip in place in the axial direction of the welding tip when the fixing member is in contact with a smaller diameter portion, and the fixing member releases the welding tip when the fixing member is in contact with a larger diameter portion.

Abstract: To provide a flux-cored welding wire and a method for arc overlay welding attaining excellent weldability and low dilution ratio and obtaining a weld bead excellent in corrosion resistance in overlay welding using the flux-cored welding wire having an advantage of high deposition rate and deposition efficiency. The flux-cored welding wire for gas shielded arc welding including flux filled up in an outer sheath and using pure Ar as a shielding gas contains, as percentage to the total mass of the flux-cored welding wire, C: 0.20 mass % or below, Si: 15.00 mass % or below, Mn: 20.00 mass % or below, P: 0.0500 mass % or below, S: 0.0500 mass % or below, and Cr: 15.0-50.0 mass %, with the remainder being Fe and inevitable impurities.

Abstract: A fillet weld joint of steel having high fatigue strength by improving stress concentration without excessively relying on imparting a compressive residual stress to a toe part by welding materials, free of cracking, and excellent in the toughness, and a method for gas shielded arc welding for obtaining the fillet weld joint are provided. In the fillet weld joint, a martensitic transformation starting temperature (Ms point) of a weld metal is 400° C. or above and 550° C. or below, a value obtained by dividing a toe radius ? of a toe part of welding by a sheet thickness t of a base metal (?/t) is 0.25 or above, an expression below Ms(° C.)?375×[?/t]+320??(1) is satisfied, and a crack defect does not exist.

Abstract: In consumable-electrode gas-shield arc welding, carbon dioxide gas is used as shield gas; the molten pool is formed using a pulsed arc as a leading electrode arc transferring one droplet per cycle by alternately outputting, in each cycle, pulses of two different pulse waveforms of which a pulse peak current level and/or a pulse width per period differ; the conductively heated filler wire is inserted into the molten pool as a trailing electrode; the distance between a tip of the filler wire inserted into the molten pool and a conductive point of the filler wire is set within a range of 200×10?3 to 500×10?3 m; and a leading-electrode base current value is set larger than a trailing-electrode filler current value. According to such a method, even when inexpensive carbon dioxide gas is used as shield gas, the amount of spatter can be reduced, and high weldability can be achieved in multipass welding.

Abstract: A solid wire contains C of 0.020 to 0.100 mass percent, Si of 0.25 to 1.10 mass percent, Mn of 1.20 to 1.65 mass percent, P of 0.008 to 0.017 mass percent, S of 0.045 to 0.150 mass percent, O of 0.0050 mass percent or less, N of 0.0050 mass percent or less, wherein P*(O+N)*105?15 is satisfied, and the remainder including Fe and impurities, wherein the relevant impurities contain Ti of 0.15 mass percent or less, B of 0.0050 mass percent or less, and Cr, Ni, Al, Nb, V, Zr, La and Ce of 0.20 mass percent or less respectively. According to such a configuration, a solid wire is provided, in which while increase in welding cost is controlled to the minimum, stability of wire feed, burn-through resistance, undercut resistance, and crack resistance are excellent, slag and spatter are hardly produced, hardness of weld metal is equal to or higher than that of base metal, and brittle fracture hardly occurs.

Abstract: Disclosed is a method for performing gas-shielded pulsed arc welding at high current densities with a flux-cored wire as an electrode wire. The pulsed arc welding is carried out by passing a pulsed current so that a pulse peak current density during a pulse peak time Tp is 400 to 950 A/mm2, a pulse base current density during a pulse base time Tb is 200 A/mm2 or more and differs from the pulse peak current density by 200 to 400 A/mm2, and an average current density is 350 to 750 A/mm2. The method allows significant spatter reduction while attaining a high deposition rate.

Abstract: A wire is adopted to hardfacing MIG-arc welding using a pure argon gas as a shielding gas. The wire is a flux-cored wire prepared through drawing a steel hoop or steel pipe as a sheath in which a flux is filled. The flux contains, based on the total mass of the wire, C: 0.12 to 5.00 percent by mass, Si: 0.50 to 3.00 percent by mass, Mn: 0.30 to 20.00 percent by mass, P: 0.050 percent by mass or less, S: 0.050 percent by mass or less, and at least one of TiO2, ZrO2, and Al2O3 (TiO2+ZrO2+Al2O3) in a total content of 0.10 to 1.20 percent by mass and has a total content of silicon and manganese (Si+Mn) of 1.20 percent by mass or more. The wire has a ratio of the total mass of the flux to the mass of the wire of 5 to 30 percent by mass.