On Underwater Gravity Arc Welding (The 2nd Report)

Application to Vertical Welding

Abstract

The feasibility of underwater vertical welding by gravity arc welding process is investigated by using 4 mm dia. coated electrodes of five types. SM41 steel plate of 6 mm thickness is used as base metal. And it is ascertained that this process may be put to practical use.
Main results are summerized as follows:
(1) Sound weld can be got easily without skillness of welder, if only proper welding conditions are selected. Especially both high titanium oxide type electrode and high cellulose type electrode have good weldability for vertical welding.
(2) The proper range of combinations of electrode angle and ratio of bead length to electrode length for the high titanium oxide type electrode seems to be relatively wide. For example the proper range of electrode angle is 45°-80° and that of ratio of bead length to electrode length is 0.8-1.2.
(3) Fillet welded joints got by high titanium oxide type electrode and high cellulose type electrode have sufficient tensile strength.
(4) The maximum hardness of weld got by vertical welding is higher than that by flat welding.
(5) As the base metal angle increases, the cooling rate of weld becomes higher. For example, cooling rate at bond at 500°C is about 230°C/sec in vertical welding and 145°C/sec in flat welding, and the former is about 1.6 times higher than the latter.