REDUCTION OF RESIDUAL-STRESS BY PARALLEL HEAT WELDING IN SMALL SPECIMENS OF TYPE-304 STAINLESS-STEEL

Abstract

A new method designated 'parallel heat welding' has been developed for the reduction of residual stress in small specimens. It is carried out using a pair of parallel heating torches attached one either side to a welding torch as a movable heat source during welding. Six different welding conditions were applied to an autogenous gas tungsten arc welded Type 304 stainless steel. During welding, the thermal cycles of four locations in the weldment were recorded to investigate the action of thermal stress and to evaluate the effect of the parallel heat sources on sensitisation. In addition, an optical microscope was used to observe the degree of sensitisation. The experimental results show that the maximum principal residual stress and parallel welding direction stress can be reduced by 21-32% when the conventional welding process is replaced by parallel heat welding. The equilibrium temperature of the welded plate can be increased from 45 to 240-degrees-C. Also, based on the exposure time recorded at temperatures in the range 600-850-degrees-C, and metallographical observations, it was found that parallel heat welding has no influence on the degree of sensitisation of austenitic stainless steel weldments.