Abstract: The method is proposed to control temperature distribution of arc in ultra narrow gap welding process with combined regulation of sheet tungsten electrode and insulating solid wall, and then the lack of fusion on the corner of square groove in ultra narrow gap can be avoided. For understanding the regulating mechanism of temperature distribution of constricted arc in sheet slanting tungsten electrode with insulating solid wall, the differential analysis of electrostatic probe is applied to diagnose the constricted arc current-carrying region. The results show that the peak temperature of arc current-carrying region in sheet slanting tungsten electrode could be enhanced by constricted effect of insulating solid wall, and then the temperature distribution range would shrink in thickness direction of sheet slanting tungsten electrode; the gap width of arc discharge could be changed by the sheet slanting tungsten electrode to lead the current density concentrate on the location with smaller gap width, which cause the global shift of higher temperature in arc, and the greater constricted effect would give rise to shift further; meanwhile the degree of shift would be reduced along the direction of arc length from anode to cathode under the influence of arc electric field; the excessive constricted effect could result in the arc current density concentrating on sheet slanting tungsten electrode locally to take electrode melting, moreover the temperature of arc current-carrying region in sheet slanting tungsten electrode could not be controlled effectively with insufficient constricted effect.

Key words: electrostatic probe, narrow gap welding, temperature distribution of current-carrying region, welding arc