Nesterenkov V. Theory and practice of stable welds formation in electron beam welding of thick metal

The thesis is devoted to studying the physical processes in keyholes at EBW of thick metal, determination of the conditions of stable formation of deep welds and development of technological processes of welding a number critical items. Theoretical and experimental investigations have been conducted of natural oscillations of molten metal of the weld pool. It is shown that in welding of metals by a steadily moving electron beam, the impact of the reaction force of recoil pressure, resulting from the electron beam interaction with the channel front wall, generates capillary waves on the melt surface, which have a discrete spectrum of natural frequencies, where the density rises with increase of penetration depth. Application of scanning in two planes with parallel transfer of the electron beam, selection of the required ranges of beam oscillation frequency and welding speeds, change of spatial orientation of the butt enables sound welded joints to be made on metals of 150 mm and greater thickness.Theoretical investigations were the basis to develop parameters of the processes of EBW of circumferential butt joints in steam generator cases, high-pressure stop valves, T-joints for oil and gas pipelines of low-alloyed steels up to 150 mm thick, as well as parameters of EBW of a number of high-strength aluminium alloys to join wing structures up to 120 mm thick.