ON UNDERWATER GRAVITY PULSED ARC WELDING.

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: When cycle time t//p//s is appproximately equal to duration of metal droplet transfer in steady current and average current I//a//v equal to steady welding current I//d, one pulse-one droplet transfer and stable arc can be obtained. In case peak time t//p is equal to base time t//b, when I//b greater than 125A and I//b/I//p greater than 0. 5, stable arc and sound weld can be obtained. In case t//p/t//p//s less than 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. Even if the average current I//a//v is kept constant, depth of penetration and fused area increase with an increase I//p and with an decreasing t//p//s. Mechanical properties of butt welded joints obtained by pulsed current are equal to those by steady current.