Mechanism of formation of nucleus gaseous bubbles during fusion welding of active metals

The conditions of formation of closed gas cavities (bubble nuclei). during fusion welding of the whole group of active metals (Ti, Zr, Hf, V, Nb, Ta) on the basis of regularities of different processes on welded detail butt edges are considered. It is shown that formation on the base of defects of welded edge faces of closed cavities filled with gas is the main reason of appearance of bubbles in the weldpool and pores in active metal welds, the thermomechanical conditions of closed gas cavities formation during the vanadium subgroup welding being more favourable than during the titanium subgroup metal welding. The formation of closed cavities from which the gas outflow is hampered and they can become bubble nuclei is still possible long before metal heating in the welding process up to the temperatures contributing to diffusion metal adhesion and is determined for the specified active metal by the character of thermomechanical and chemicometallurgical processes flow on face surfaces of welded edges