1988 Volume 6 Issue 1 Pages 86-91
Characteristics and behavior of tungsten arc and feasibility of arc welding of mild steels were investigated in the pressure range from 0 to 5MPa (gauge). As the cathode, 2% thoriated tungsten of 4 mm in diameter and of 30° in vertex angle was used.
Results obtained are summarized as follows:
(1) Arc voltage increases with increasing pressure. VA+VK is 11.5V in OMPa and it decreases with increasing pressure. It shows about 9.3V constantly over 0.5MPa.
(2) Arc column concentrates and the diameter of arc decreases with increasing pressure. As the result, current density in centre of arc increases considerably.
(3) The area of cathode spot decreases and therefore cathode mode of arc changes from normal mode to cathode spot mode with increasing pressure. As the result, the erosion of tungsten tips increases. Especially, the erosion in He atmosphere is much greater than that in Ar atmosphere.
(4) The depth of penetration of mild steel plate increases with increasing pressure. Therefore, the optimum welding current for penetration welding of thin mild steel plate decreases considerably with pressure.
(5) Sound penetration welds of mild steel plates of 3.2 mm in thickness can be obtained under pressure range up to 3MPa.