Abstract
This study aimed at he experimental and finite element analytic investigation of the effect of preheating on he residual stress of weldment. In this study, an autogenous arc welding was used on type 304 stainless steel and MARC as F.E.M. common code was utilized in analysis The analyses include transient and moving heat source and thermal properties as function of temperature. During welding, the thermal cycles of four locations in the weldment were recorded to investigate of the behavior of thermal stress and residual stress. The experimental and analytic results had good coincidence and show that there are two factors influencing the formation of welding residual stress in preheat process. One is the elevation of welding equilibrium temperature and the other is the increase of amount of heat input. The former decrease welding residual stress and the latter increase welding residual stress. Therefore, the cumulative effects result in the welding residual stress not being improved significantly with preheating in 304 stainless steel.