A high-strength steel allowing low-temperature welding and high-heat input welding and a production method thereof are provided, which belongs to the technical field of steel production. The high-strength steel includes the following chemical components by mass fraction: 0.03-0.16% of C, 0.05-0.5% of Si, 1.0-1.9% of Mn, 0.002-0.02% of P, 0.001-0.01% of S, 0.005-0.07% of A1, 0.005-0.04% of Ti, 0.1-0.5% of Cr, 0.0005-0.005% of B, 0.002-0.01% of Mg+Zr, 0.001-0.008% of O, 0.004-0.01% of N, and the balance of Fe and residual elements. Magnesium and zirconium are added to form magnesium/zirconium oxide, titanium and boron are added to form titanium/boron nitride, and the two types of precipitates work synergistically to improve the microstructure of a heat-affected zone. The method optimizes the chemical composition and production process of existing high-strength steel.

Bulk copper solder is highly desired as a solder compound because it is very electrically conductive and has a high melting point relative to other solders. A composition for a copper solder includes copper(II) oxide powder in the range of 37-53% by mass, silicon carbide (SiC) powder in the range of 8-14% by mass, and a flux in the range of 35%-53% by mass. Energy in the form of microwave energy can be applied to the copper solder to convert the Cu(II)O to Cu, for a Cu product conversion of >93%.

An aluminum wire body, in which an aluminum or aluminum alloy electric wire and a metal to be joined are joined by solder, wherein the solder includes an oxide glass including vanadium and a conducting particle. Preferably, the conducting particle contained in the solder is 90% by volume or less and the oxide glass is 20% by volume to 90% by volume. Further preferably, the oxide glass includes 40% by mass or more of Ag.sub.2O in terms of oxides and the glass transition point is 180° C. or less.

A flux-cored wire for are welding of a duplex stainless steel includes a stainless-steel sheath filled with a flux and contains, with respect to the total mass of the wire, predetermined amounts of Cr, Ni, Mo, N, Mn, and Si, in which letting a Ti alloy content in terms of Ti be [Ti] and letting an Al alloy content in terms of Al be [Al], [Ti] and [Al] are predetermined values, and in which parameter A expressed as A=[Ti]+2×[Al] satisfies a predetermined value, and the balance is composed of Fe, a slag-forming component, and incidental impurities.

[Object] There is provided a flux-cored wire capable of obtaining a weld metal having excellent low temperature toughness and improving welding efficiency, in which preheating performed for preventing cold cracking can be omitted or simplified. [Means for Solving Problems] The flux-cored wire includes one or more of CaF.sub.2, BaF.sub.2, SrF.sub.2, MgF.sub.2, and LiF and, when a total amount thereof is defined as α, the α is 2.0% to 7.0%, by mass %, with respect to a total mass of the flux-cored wire, one or more of a Ti oxide, a Si oxide, a Mg oxide, an Al oxide, a Zr oxide, and a Ca oxide are included in the flux-cored wire, and when a total amount thereof is defined as β, the β is 0.2% to 0.9%, by mass %, with respect to the total mass of the flux-cored wire, a ratio of an amount of the CaF.sub.2 with respect to the α is 0.90 or more, and a ratio of the α with respect to the β is 3.0 or more and 15.0 or less.

The invention provides an ignition flux for arc stud welding, including at least 30 wt % of an active agent, with the active agent selected from a group consisting of SiO.sub.2 and TiO.sub.2. As such, the electric arc can be easily created and smoothly formed. The invention further provides an arc stud welding method utilizing such ignition flux. As such, the fastener and the metal workpiece can be tightly connected together without the need of inserting an ignition tip into the welding portion of a fastener.

The present invention provides a flux-cored welding wire comprising a shell having a tubular cavity, which accommodates flux. The shell is made of 400 series stainless steels. The deposited metal formed after the welding using the flux-cored welding wire of the present invention has more uniform chemical compositions. Because the loss of chromium during the transition to the deposited metal is less than 0.1%, recourses is saved and welding cost is reduced. The filling ratio of the flux-cored welding wire of the present invention is 5%-25% (preferably 10%-20%). As a result, not only the stability of the compositions in the flux is increased, but also the disadvantages to the manufacture process caused by high filling ratio are avoided. The flux-cored welding wire of the present invention will not be rusty even after it is exposed to the air for a long time.

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.

The present invention relates to a flux-cored wire which can be used for straight-polarity gas-shielded arc welding, wherein a flux contains one or several types of metal compound powders and, when one or several metal elements constituting the metal compound powders are formed into stable compounds under a high-temperature environment, the relationship between the weighted geometric mean value (Φ) of the work functions of the stable compounds and the wire diameter (D) of the flux-cored wire satisfies the following formula: {1.00≤Φ≤−0.0908D.sup.2+0.5473D+1.547}.

A TIG welding flux for dissimilar steels is used to solve the problem that the conventional friction stir welding procedure for butt-joint welding a stainless steel workpiece and a carbon steel workpiece cannot be used on site, as well as the problem that the increased operating time and manufacturing cost due to forming bevel faces on both the stainless steel workpiece and the carbon steel workpiece. The TIG welding flux for dissimilar steels includes 25-35 wt % of silicon dioxide (SiO.sub.2), 20-30 wt % of cobalt (II, III) oxide (Co.sub.3O.sub.4), 15-20 wt % of manganese (II, III) oxide (Mn.sub.3O.sub.4), 10-15 wt % of nickel (III) oxide (Ni.sub.2O.sub.3), 7-12 wt % of molybdenum trioxide (MoO.sub.3), 6-11 wt % of manganese (II) carbonate (MnCO.sub.3), 5-10 wt % of nickel (II) carbonate (NiCO.sub.3), and 2-4 wt % of aluminum fluoride (AlF.sub.3).