A study on the relief of residual stresses in weldments without post weld heat treatment

Post weld heat treatment (PWHT) is the most common technique employed for relieving residual stresses after general repair welding. Besides, the primary purpose of reducing the effect of stresses induced by welding, PWHT is also intended to temper the metallurgicalstructure of the heat affected zone (HAZ). Unfortunately, there are significant difficulties in carrying out post weld heat treatment such as; the complexity of weld geometry, the possibility of distortion in the case of any mechanical loads, difficulty in heating symmetrically, and also PWHT may cause degradation of the material properties (especially creep and tensile strength in the case of multi PWHT cycles).The paper also examines different heat input ratio between the first tempering bead layer and the weld beads deposited against the base metal and studies their effects on the residual stress using finite element method. The results show that Pre-heat had significanteffect on the reduction of transverse and longitudinal residual stresses values but it didn’t have remarkable effect on through thickness stresses.

Keywords:

Welding , Hole Drilling , thermal mechanical analysis , Residual Stress (RS)