Provided is a solder paste which uses a conventional flux, and for which long-term preservation is made possible and an easy preservation method can be realized by suppressing changes in the viscosity of the paste over time. This solder paste is provided with a solder powder, a zirconium oxide powder, and a flux, and changes in the viscosity of the paste over time are suppressed.

A flux for submerged arc welding is a sintered flux and is for use in high speed welding. In the flux, the following relationships of contents in mass percent are satisfied: CaF.sub.2: 10.0% to 20.0%, MgO: 8.0% to 15.0%, a sum of Na.sub.2O and K.sub.2O: 2.1% to 3.5%, MnO: 1.5% to 5.0%, FeO: 0.5% to 5.0%, SiO.sub.2: 10.0% to 20.0%, Al.sub.2O.sub.3: 13.0% to 28.0%, and TiO.sub.2: 13.0% to 28.0%. In addition, the following relationships are further satisfied: 65≤(MgO+SiO.sub.2+Al.sub.2O.sub.3+TiO.sub.2)≤75, and 0.5≤(Al.sub.2O.sub.3/TiO.sub.2)≤2.0.

A method for the manufacture of a welded joint including the following successive steps: I. The provision of at least two metallic substrates wherein at least one metallic substrate is a steel substrate, and II. The welding of the at least two metallic substrates with a welding head while, simultaneously, applying on the at least two metallic substrates, ahead of the welding head, a welding flux including a titanate and a nanoparticulate oxide selected from the group consisting of TiO.sub.2, SiO.sub.2, ZrO.sub.2, Y.sub.2O.sub.3, Al.sub.2O.sub.3, MoO.sub.3, CrO.sub.3, CeO.sub.2, La.sub.2O.sub.3 and mixtures thereof.

The invention concerns a flux for brazing, a process for brazing metal parts employing said flux, a flux composition containing said flux, aluminum parts coated with said flux or said flux composition, a process for brazing and a brazed metal object obtainable by said brazing process. The flux is high in KAlF.sub.4 and low in K.sub.3AlF.sub.6.

According to an aspect of the present invention, there is provided a flux-cored wire including a steel sheath and a flux that fills the steel sheath. The flux contains fluorides of which a total value of F-equivalent values is 0.21% or more, oxides of which the total value of amounts ranges from 0.30% to 3.50%, and carbonates of which a total value of amounts ranges from 0% to 3.50%. An amount of CaO ranges from 0% to 0.20%. An amount of iron powder ranges from 0% to less than 10.0%. A Y-value is 5.0% or less. The amount of CaF.sub.2 is less than 0.50%. The amount of Ti oxides ranges from 0.10% to 2.50%. A ratio of to ranges from 0.10 to 4.00. A total value of amounts of MgCO.sub.3, Na.sub.2CO.sub.3, and LiCO.sub.3 ranges from 0% to 3.00%. A chemical composition excluding the fluorides, the oxides, the CaO, the carbonates, and the iron powder is within a predetermined range. Ceq ranges from 0.10% to 0.44%.

Provided is a flux capable of obtaining predetermined rheological characteristics both at room temperature and under a thermal history that is assumed for soldering and capable of suppressing the amount of a residue after soldering to realize a low residue. The flux contains a first alcohol compound that has two or more OH groups and has a melting point of lower than 25 C. and a second alcohol compound that has two or more OH groups and has a melting point of higher than 25 C., the first alcohol compound is glycerin, the second alcohol compound is 2,5-dimethylhexane-2,5-diol, the flux has a viscosity of 10 Pa.Math.s or more and 50 Pa.Math.s or less at 25 C. and has a viscosity of more than 0 Pa.Math.s and 1 Pa.Math.s or less at 100 C., and, in a case where 10 mg of the flux is heated up to 25 C. to 250 C. under a N.sub.2 atmosphere at a temperature rise rate of 10 C./min, the weight of the flux after heating is 15% or less of the weight of the flux before heating.

A universal approach is described to produce welding filler materials with enhanced grain refining, for making welded objects with hot-crack resistance. Some variations provide a welding filler material comprising a functionalized metal-containing powder, wherein the functionalized metal-containing powder comprises metal or metal alloy particles and a plurality of nanoparticles disposed on surfaces of the metal or metal alloy particles, and wherein the nanoparticles are consolidated in a three-dimensional architecture throughout the welding filler material. A welded object contains a welding filler material comprising the functionalized metal-containing powder, enabling the welded object to be free of hot cracks. Other variations provide methods of making a welding filler material. This approach has been successfully demonstrated by incorporating zirconium-based nanoparticle grain refiners within a welding precursor material for welding aluminum alloy Al 7075, as one non-limiting example.

An apparatus and method for cleaning an oxide film using a direct current reverse polarity are provided. The apparatus for cleaning an oxide film formed on a workpiece may include a power supply configured to apply direct current power and to include a positive electrode terminal and a negative electrode terminal, the workpiece configured to be electrically connected to the negative electrode terminal to act as a negative electrode to which a current is applied, and a torch having a positive electrode, which is spaced apart from the oxide film by a predetermined distance and is electrically connected to the positive electrode terminal, the torch being installed to be movable relative to the workpiece. The oxide film formed on the workpiece may be removed by applying a reverse polarity direct current between the workpiece, serving as the negative electrode, and the positive electrode to generate an arc.

The present disclosure relates to tubular welding electrodes that have a metallic sheath surrounding a granular core, wherein the metallic sheath comprises a metal matrix composite (MMC) that includes a ceramic material and aluminum or an aluminum alloy. The ceramic material may be in the form of microparticles or nanoparticles. The present disclosure also relates to method for making such tubular welding electrodes.

A manufacturing method of a copper bonded part in which a first copper member and a second copper member are bonded together. The first copper member and the second copper member are made of copper or a copper alloy, and at least one of the first copper member and the second copper member includes a copper porous body made of copper or a copper alloy. This manufacturing method has a bonding material disposing step S01 of disposing a bonding material between the first copper member and the second copper member, and a reduction sintering step S02 of heating and holding the first copper member, the second copper member, and the bonding material in a reducing atmosphere in a range of 600 C. or higher and 1,050 C. or lower. The bonding material contains a copper oxide or a mixture of metallic copper and the copper oxide.