Investigation of the distribution of residual stresses in dissimilar thickness girth welds

Abstract

Investigation of the distribution of residual stresses in girth welds of pipes is a rather laborious process. It is not always possible to predict how residual stress fields will be formed after welding. The result depends on steel grade, technological process of welding (heat input welding, welding speeds), temperature of environment, geometrical parameters of pipes. Distribution of residual stresses in a dissimilar thickness girth butt weld of pipes with a diameter of 530 mm of low alloyed (0.9%C-2%Mn-1%Si) steel was studied. Residual stresses were measured by the X-ray method based on measurement of microdeformation of a crystal lattice of a material under its influence. The research results showed that tensile residual stresses in the girth weld were formed at the inner side of the pipe after welding. It was revealed that the magnitude and distribution of residual stresses depend on the wall thickness of the pipes. In a thinner pipe, the level of tensile residual stresses is 40-50% higher than that of a thicker pipe. Investigation of the distribution of residual stresses in welded joints can be useful for developing methods to reduce the high residual stresses that occur after welding and also at deciding of constructive and technological task in the process of welding works.