Studies on the Porosity in Welding Joints (3rd Report)

Results of Experimental Welding

Abstract

The welding conditions have complicated influence on the porosity in aluminium alloy welds. The authors reported in their first report that the heat input in welds influences considerably the gas content in welds and further in their second report that several different inspection methods presently available of welding porosity have respective merits and demerits.
In this report (the third report) an attempt is made to simplify and analyse the welding conditions in the case of experimental welding which influence the porosity in aluminium alloy welds. The apparatus prepared for the purpose is schematically shown in Fig. 1.
The following results were obtained :
1) The increase of heat input in welds decreases the percentage voids of porosity in spot deposit (Fig. 6) ; the same result was also obtained in practical welding. Since the increase of heat input decreases the cooling rate of molten pool, it is clear that the cooling rate has remarkable influence on the welding porosity.
2) Heat input of welds, however, is a complicated factor for welding porosity. It is therefore considered necessary to divide the factor into two minor ones, i.e., the cooling rate and the temperature of molten pool, and then investigate both, As the result of temperature measurement in molten pool during welding, it was found that the temperature and the porosity in weld deposits simultaneously increased linearly with the welding current.