パルスMIG溶接における溶滴移行とビード形成に及ぼす電流波形の効果

パルスアーク溶接に関する研究(第1報)

抄録

Pulsed MIG welding phenomena are studied fundamentally in order to make clear the effects of welding current, supplied from the transistor power source. Correlation between current waveform and metal droplet transfer is investigated with the optical metal droplet detector, which is consisted of He-Ne laser, optical lens and filters, and photo-transistor.
Results obtained are summarized as follows;
(1) In pulsed MIG welding, it is found out that there exists critical frequency f_cr. At the frequency of f_cr, metal droplet transfers synchronously with respect to each pulse current.
(2) In the frequencies lower than f_cr, if pulse peak current is set enough higher than the level for spray transfer, metal transfer mode becomes spray transfer mode in the duration of peak current.
(3) In the frequencies higher than f_cr, if the average current level is lower than critical current, metal transfer is carried out in irregular drop transfer mode.
(4) Critical pulse frequency f_cr, sustaining one pulse-one droplet transfer, varies with respect to the pulsive peak current level and the size of wire used.
(5) In the case that average current is lower than critical current, metal transfer mode and bead formation mechanism vary in accordance with pulse frequency.
(6) In extremely low pulse frequency range, pulsed MIG welding is effective to improve the shape of welds in a repeating sequence of melt and solidification of pool.
(7) Even if the average current is kept constant, weld bead penetration becomes deeper as the level of peak current becomes higher.