Abstract
The feasibility of underwater overhead welding by gravity arc welding process is investigated. The 4 mm dia. coated electrodes of five types and SM41 steel base metal of 6 mm thickness are used. 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, if only proper welding conditions are selected. Especially high titanium oxide type, ilmenite type and lime titania type electrodes have relatively good weldability for overhead welding.(2) The range of proper welding conditions using the high titanium oxide type electrode seems to be relatively wide. For example the proper range of electrode angle is 45°-80° and the proper welding current 135-180 Amp.(3) Fillet welded joints got by high titanium oxide type, ilmenite type and lime titania type electrodes have sufficient tensile strength.(4) The maximum hardness of the weld got by overhead welding is lower than that by flat and vertical welding.(5) Cooling rate in overhead welding is lower than that in flat and vertical welding. For example, cooling rate at bond at 500°C is about 135°C/sec in overhead welding, 140°C/sec in flat and 205°C/sec in vertical.
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