Abstract: The new method for welding of SUS304 austenitic stainless-steel is proposed to improve the heating characteristics of pulsed current sheet tungsten electrode arc constricted by insulating solid wall on groove in ultra-narrow gap. The bottom, side and corner in ultra-narrow gap groove could obtain good fusion in lower heat input by this method. Meanwhile the heating mechanisms of pulsed current sheet tungsten electrode arc constricted by insulating solid wall on ultra-narrow gap groove would be understood by comparative analysis of transverse weld morphology, geometric parameters with variation of pulse current frequency, duty cycle and average welding current, thermal cycle curve, peak pressure of pulsed arc and arc shape. The results show the synergistic effects of pulse current frequency, duty cycle, average welding current and constriction by insulating solid wall on sheet tungsten electrode arc would determinate the heating characteristics on groove in ultra-narrow gap; the raise of pulse current frequency would intensify the pulsed arc peak effect and self-induced magnetic compression, by which the heating effects on bottom in groove would be strengthened and on side in groove would be weakened; the variation of duty cycle would cause opposite tendency for thermal effect of pulsed arc and pulsed arc peak effect; when the duty cycle increased, the strengthened thermal effect of pulsed arc would enhance heating effect on groove, once the weakened pulsed arc peak effect could dominate, the heating effect on groove would be decimated; the couple effect of average welding current and constriction by insulating solid wall on sheet tungsten electrode arc could not only reinforce the heating effect on bottom in groove but also restrict the intensification of heating effect on side in groove.

Key words: pulsed current, ultra-narrow gap welding, heating characteristic