On Underwater Gravity Pulsed Arc Welding

Abstract

Underwater welding by gravity pulsed arc welding process and welding phenomena were investigated by using coated electrodes of three types.
Main results obtained are summarized as follows:
(1) When cycle time t_ps is approximately equal to duration of metal droplet transfer in steady current and average current I_av equal to steady welding current I_d, one pulse-one droplet transfer and stable arc can be obtained.
(2) In case peak time t_p is equal to base time t_b, when I_b, >125A and I_b/I_p>0.5, stable arc and sound weld can be obtained.
(3) In case t_p/t_ps<0.5, an extremely stable arc can be obtained, because base current I_b can be selected to a proper current in steady welding current and besides one pulse-one droplet transfer is sustained.
(4) Even if the average current I_av is kept constant, depth of penetration and fused area increase with an increasing I_p and with an decreasing t_ps.
(5) Mechanical properties of butt welded joints obtained by pulsed current are equal to those by steady current.