1986 Volume 4 Issue 4 Pages 691-696
Characteristics and behavior of tungsten arc and feasibility of arc welding of mild steels were investigated in the pressure range from 0 to 5 MPa (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. However, VA+VK decreases a little with increasing pressure from 0 MPa to 0.5 MPa. It shows about 7.3 V constantly over 0.5 MPa.
(2) Diameter and half width of arc decreases and the current density in centre of arc increases considerably with increasing pressure.
(3) The area of cathode spot decreases and therefore it concentrates at the tip of tungsten with increasing pressure. As the result, the erosion of tungsten tips increases.
(4) In constant welding current, the depth of penetration of mild steel increases with increasing pressure. Therefore, the optimum current for penetration welding of thin mild steel plate decreases with pressure.
(5) Relatively sound penetration welds of mild steel plates of 2 and 3.2 mm in thickness can be obtained under pressure range up to 5 MPa. However, the meandering bead was often obtained by the fluctuated arc over 2 MPa.
(6) Welded joints obtained under pressure range of up to 5 MPa have sufficient tensile strength and Charpy impact value.