On Underwater Gravity Arc Welding (The 4th Report)

Effect of Water Pressure on Welding Results and Welding Phenomena

Abstract

The feasibility of gravity arc welding (DCSP) and welding phenomena under water pressures from 0.03 to 6 Kg/cm² (guage pressure) are investigated. The 4 mm diameter coated electrodes of five types and the SM41 steel base metals of 6 and 9 mm thickness are used.
Main experimental results are summerized as follows:
(1) Welding arc can be generated easily and kept in stable under water pressures from 0.03 to 6 Kg/cm2, if only proper welding conditions are selected. Especially the high titanium oxide type electrode waterproofed by laquar has relatively good weldability.
(2) The porosity in weld metal increase with an increasing water pressure.
(3) The butt welded joints obtained under 0.03, 3 and 6 Kg/cm² pressures have sufficient tensile strength in as-welded condition. However, the tensile strength of weld metal decreases with increase of water pressure.
(4) Carbon content of weld metal is raised to some extent with increase of water pressure and manganese and silicon contents are reduced. And hardness distribution in weld metal lowers as water pressure increases.
(5) The thermal pinch effect on arc column is enhanced by increase of water pressure and constriction of arc column becomes stronger.
(6) The anode spot on base metal and cathode spot at tip of core wire fluctuate more violently as water pressure increases.
(7) Water pressure decreases melting rate of electrode.