Method of joining metal parts by fusion welding

Abstract

A method of joining metal parts by fusion arc welding in a weld of small volume includes the steps of providing the metal parts to be joined having a first side which accessible to a welding operation and a second side opposite the first side. The metal parts have welding surfaces shaped to have a first flank adjacent the first side and a second flank adjacent the second side, a step joining the flanks. Each part has a relief bulge formed in the second side adjacent the second flank, and a centering offset at the second flank to position the metal parts relative to one another for welding. The relief bulge is provided to ensure that the centering offsets melt during welding, and is shaped to have a sufficient size so that a predetermined melt-through point develops for melting of the centering offset during welding. The metal parts are positioned for welding by abutting the second flanks at the centering offset, the parts being positioned so that the first flanks define therebetween a first gap and the second flanks define therebetween a second gap, the second gap being narrower than the first gap. In a first welding step, the metal parts are joined at the second flanks by one of a fully automatic tungsten inert-gas welding process (GTAW) or gas metal-arc welding process (GMAW) to form multi-pass welding beads which extend over the entire width of the second gap, and thereafter, the first flanks are joined with a submerged-arc welding process by forming a plurality of welding beads bearing alternately against one and an opposite flank.