Journal of Pure and Applied Ultrasonics

A. Joseph ¹, Govind K. Sharma ¹, B. Purnachandra Rao ¹, K. Nataraj ²

Affiliations
1 Nondestructive Evaluation Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102, IN
2 Department of Physics, National Institute of Technology, Trichy-620015, IN

Abstract

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.

Keywords

Residual Stress, Ultrasonic Technique, Carbon Steel, Sequential Welding Passes.

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A. Joseph ¹, Govind K. Sharma ¹, T. Jayakumar ¹

Affiliations
1 Non-Destructive Evaluation Division, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102, Tamil Nadu, IN

Abstract

Ultrasonic Internal Rotary Inspection System (IRIS) is used for inspection of tubes of heat exchangers and steam generators. The system displays circumferential cross section of tubes (wall thickness of tubes) at any given axial position and reveals both uniform and localised (pitting) corrosion. In this paper, the operating principle of IRIS and comparison of wall thickness measurements by physical and IRIS methods are briefly explained. Details of studies carried out on the resolution capabilities of IRIS in stainless steel and brass tubes having artificial defects (holes) are discussed. The results obtained from a study carried out on a carbon steel tube with artificial defects under baffle plate are also discussed in this paper.

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