Abstract: A process for manufacturing seamless flux-cored welding wires 0.8 to 4 mm in diameter with excellent cracking resistance and primer proof quality and containing very little diffusible hydrogen suited for the welding of high-tensile steels and steel structures subjected to large restraining forces by dehydrogenating by high-temperature heating comprises the steps of heating a straight wire 8 to 15 mm in diameter by direct electric heating through a first and a second pair of roll electrodes spaced 2 to 5 m apart and a ring transformer disposed therebetween to a temperature between 620.degree. and 1100.degree. C., cooling the heated wire to a temperature not higher than 500.degree. C. with a coefficient of heat transfer not higher than 250 kcal/m.sup.2 h.degree.C., and drawing to the desired diameter. The welding wire thus obtained a weld containing not more than 5 ml of diffusible hydrogen per 100 g deposited metal.

Abstract: A method for manufacturing tubes filled with powdery and/or granular substances comprising the steps of forming a metal strip into a tube, feeding powdery and/or granular substances into the tube being formed as a core, joining together the edges of the tube filled with the core of the powdery and/or granular substances by high-frequency welding, and reducing the diameter of the welded tube filled with the core of the powdery and/or granular substances. At least the top layer of the core in the tube is composed of powdery and/or granular substances having low enough magnetic susceptibility to remain unattracted to the magnetized tube edges that is determined based on the welding heat input.

Abstract: A method of manufacturing tubes filled with powdery and/or granular substances, such as flux-cored welding wires. A tube filled with a powdery and/or granular substance is continuously manufactured by forming a metal strip being fed in its longitudinal direction into an unwelded tube (1a) using forming rolls (2), feeding a powdery and/or granular substance (F) into the unwelded tube (1a) being formed through its opening, butt-welding together fringing edges of the opening, and reducing the diameter of the welded tube (1b). An allowable minimum heat input below which cold cracking occurs and a maximum allowable heat input above which spatters whose diameter is not smaller than 0.83 times the inside diameter of the finished tube are generated are determined in advance, and the butt welding is performed with a heat input larger than the allowable minimum heat input and smaller than the allowable maximum heat input.