On Underwater Gravity Arc Welding (The 1st Report)

Abstract

Underwater welding by gravity arc welding process is investigated by using coated electrodes of six types and SM41 steel plate of 6 mm thickness as base metal. And it is ascertained that this process may be put to practical use.
Main results are summarized as follows:
(1) Sound weld can be obtained easily by any unskilled welding operator using any type electrode except low hydrogen one, due to stable arc. Especially appearances of beads obtaind using high titanium oxide type and lime titania type electrode are good.
(2) The proper range of combinations of welding current and diameter of electrode for the high titanium oxide type is relatively wider than that for the ilmenite and the iron powder iron oxide type.
(3) Weld metal has the same tensile strength as base metal.
(4) Weld metal has an impact value of 40 - 50% of that of base metal.
(5) Cooling rate at 500°C at bond is about 140°C/sec in water and 18°C/sec in air, the former being about 8 times higher than the latter.