Abstract: This paper deals with the principle, the characteristics and the process results of the medium-frequency pulse MIG welding inverters. By means of 315A HOSFET inverter and 630A IGBT inverter for are welding, MIG welding tests of Al alloys used in space industry are conducted, in which the output pulses 80kHz and 40kHz of the inverters are modulated to medium-frequency pulses of less than 1kHz. The tests show that this MIG welding technology has the advantages over the current low frequency pulse welding and DC MIG welding in getting better penetration, stronger "etching effect", finer grain structure of weld, smaller tendency to the generation of micro-gas hole and greater strength of welding joint, and thus has a broad prospect.

Key words: Arc welding inverter, Medium-frequency pulse, MIG welding