Ultrasonic Lcr Wave Technique for Residual Stress Measurements in Carbon Steel Weld Joints Fabricated by Different Weld Pass Sequences

Low carbon steel is the most commonly used material for various applications because its cost is relatively low. Different methods are employed to reduce residual stresses in carbon steel weld joints. Post weld heat treatment (PWHT) is the most commonly used method to relieve/reduce the residual stresses. Use of different sequential weld passes during welding is one of the alternate methods used to get minimum residual stresses in higher thickness double 'V' carbon steel weld joints. A study was undertaken to nondestructively quantify the residual stresses present in carbon steel weld joints made using three different weld pass sequences. For this study, three sets of 20.0 mm thick low carbon steel double 'V' weld joints were fabricated with three different weld pass sequences using the Manual Metal Arc Welding (MMAW) process. Ultrasonic based residual stress measurements offer estimation of surface, sub-surface and bulk residual stresses. Details of critically refracted longitudinal (L_cr ) ultrasonic wave technique employed for residual stress measurements are discussed in this paper. The residual stress values of carbon steel weld joints obtained using the ultrasonic L_cr technique showed minimum longitudinal tensile residual stresses in the weld joints made by alternate weld pass sequence as compared to the other two weld pass sequences. The ultrasonic L_cr technique used is nondestructive, portable and low cost technique for residual stress measurements. This technique can also be used for in-situ measurement of residual stresses in operating components.