Abstract: A gas-shielded arc welding method includes welding a steel plate having a tensile strength of 780 MPa or more while feeding a consumable electrode via a welding torch and flowing a shielding gas. The consumable electrode includes, in mass %, C: 0 to 0.20%, Si: 0 to 0.50%, Mn: 0 to 0.50%, Cr: 1.00% to 9.00%, S: 0.0020% to 0.0600%, and Ni: 0 to 0.50%. The shielding gas includes, in vol. %, at least one of CO2 and O2: 1% to 15% in total, with the remainder being Ar and unavoidable impurities. Welding is performed under the condition satisfying the relationship of 1?{?0.05×[CO2+O2]}+[Cr]?8.3, and [Cr] represents the content of Cr in the consumable electrode, and [CO2+O2] represents a total content of at least one of CO2 and O2 in the shielding gas.

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) and containing 0.35 mass % or more of C, the method being characterized by forming a weld metal having a structure in which the proportion of an austenitic structure exceeds 80%; and a welding wire suitable for being used therefor. 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: 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: Disclosed is a method for producing a steel part, which includes the steps of: preparing a built-up steel sheet including a steel sheet 20 including: C: 0.15 to 0.5% by mass, Si: 0.10 to 3% by mass, Mn: 0.5 to 5% by mass, P: 0.05% by mass or less (excluding 0%), S: 0.05% by mass or less (excluding 0%), Al: 0.01 to 1% by mass, B: 0.0002 to 0.01% by mass, Ti: 0.005 to (3.4[N]+0.1) % by mass (in which [N] represents a content of N (% by mass)), and N: 0.001 to 0.01% by mass, with the balance being iron and inevitable impurities, and one or more built-up portions 30 provided on the steel sheet 20; hot-forming the built-up steel sheet at a temperature of an Ac3 point or higher of the steel sheet 20; and cooling the hot-formed built-up steel sheet to a temperature of an Ms point or lower of the steel sheet such that an area ratio of martensite in the metal structure of the steel sheet 20 is 70% or more.

Abstract: In this flux-cored wire, the contents of F, Li, acid-soluble Al, Mg, S, CO2, Ba, Ca, Sr, REM, P, C which is not derived from a carbonate, Mn, Ni, and Cu are set to fall within prescribed ranges with respect to the total mass of the wire, and the blending ratio among these components is set to fall within a particular range.

Abstract: An arc welding device is provided with including: a wire feed motor; a rocker arm attached freely rotatably to an output shaft of the wire feed motor; a pair of wire feed rollers attached to the rocker arm; a rotation transmitting mechanism for transmitting the rotation of the wire feed motor to the wire feed roller; a rocker drive unit; and a welding power supply unit. The wire feed roller has inserted therein welding wire disposed along the rocking direction of the rocker arm. The welding wire is fed towards a torch tip by the wire feed roller, and arcing and shorting can be repeated with forward and backward movement by the rocker arm in the direction of the wire feed.

Abstract: A welding torch (100) for arc welding in a shielding gas atmosphere, includes: a contact tip (25) for feeding a welding wire (13); a suction nozzle (23) surrounding the welding wire, and sucking a gas from a space between the suction nozzle (23) and the welding wire; and a shielding gas supply nozzle (21) provided on the outer periphery of the suction nozzle (23), and supplying the shielding gas toward a welded portion from a space between the shielding gas supply nozzle (21) and the suction nozzle (23). The welding torch (100) satisfies “7?Ltk?17 and 0?Lts?18”, where Lts [mm] is a distance between the tip of the contact tip (25) and the tip of the shielding gas supply nozzle (21), and Ltk [mm] is a distance between the tip of the contact tip (25) and the tip of the suction nozzle (23).

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 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 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 provides the following: a covered flux which has a low chromium content and which can improve the fatigue strength of a weld in additional welding; and a covered electrode. The covered flux used for a covered electrode has a composition that contains, relative to the total mass of the covered flux, 35-55 mass % of a metal carbonate (in terms of CO2), 10-30 mass % of a metal fluoride (in terms of F), and 8.5-20 mass % of Mn and/or 7.5-20 mass % of Ni. In addition, the covered electrode is obtained by coating an iron-based core wire with this covered flux.

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 welding system includes a welding torch that welds a workpiece by using a wire, a suction device that sucks shielding gas, and a sucked shielding gas supply path for allowing the sucked shielding gas to flow, wherein the welding torch includes a contact chip that guides the wire, a shielding gas supply nozzle that supplies the shielding gas to a weld zone, and a suction nozzle that surrounds a periphery of the wire protruding from the contact chip, and is opened toward a tip of the wire to suck the shielding gas.

Abstract: Provided is a flux-cored wire which can be MIG-welded at any welding position using a pure Ar gas as a shielding gas. A flux-cored wire having a flux filled in the outer skin thereof, wherein TiO2, Al2O3, SiO2 and ZrO2 are contained in amounts of 4.7 to 8.5% by mass, 0.5 to 3.5% by mass, 0.5 to 2.0% by mass and 0.8 to 3.0% by mass, respectively, and metal oxides are also contained in the total amount of 8.0 to 13.5% by mass all relative to the total mass of the wire, and the amount of a metal fluoride is limited to 0.02% by mass or less (including 0% by mass).

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: A pure Ar-MIG welding wire for welding steel according to the present invention is formed of a flux-cored wire. The flux-cored wire is formed in the manner that a formation formed by welding a carbon steel hoop into a pipe shape or a seamless pipe is used as an outer sheath, the outer sheath is filled with a flux, and a wire drawing process is performed. The flux accounts for 7 to 27 mass % of the total wire mass. The wire contains graphite in the amount of 0.16 to 2.00 mass % on the basis of the total wire mass and iron powder in the amount of 20 mass % on the basis of the total flux mass. According to the construction, neither expensive metal resource nor a greenhouse effect gas is used, slag and fume generation is inhibited, and a weld joint having a high static tensile strength and fatigue strength can be obtained.

Abstract: There is provided a flux-cored wire containing flux within a stainless steel or mild steel outer cover for use in stainless steel welding and gas-shielded arc welding using a shielding gas. The flux-cored wire contains, based on the total mass of the flux-cored wire, predetermined amounts of C, Si, Mn, P, S, Cr, Ti, and O. The remainder are Fe and incidental impurities. The shielding gas is pure Ar gas.

Abstract: A fillet weld joint of steel formed by arc welding, wherein 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 Ms(° C.)?375×[?/t]+320 is satisfied, and a crack defect does not exist in the fillet weld joint.

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: Provided is a flux-cored wire that is for build-up welding, can obtain a target welding metal composition by means of a low number of layers, and has a low base material dilution. The flux-cored wire for build-up welding, which is such that flux fills the inside of an outer skin, has a composition satisfying the belowmentioned formula (I) when, with respect to the total mass of the flux, the total content (F equivalent value) of alkali metal fluorides and alkaline earth metal fluorides is A (mass %), the total content of alkali metal elemental metals and alkaline earth metal elemental metals is B (mass %), and the total content of alkali metal oxides and alkaline earth metal oxides is C (mass %): 0.3?[A/{1+0.7×(B+2C)}]?2.0??(I).