Abstract

The power engineering, chemical, and oil and gas industries increasingly use dissimilar metal welds (DMWs) in various installations. Radiographic and ultrasonic testing are commonly used to inspect DMWs; however, both methods have limitations, including strong dependence on flaw geometry and microstructural inhomogeneity. Moreover, conventional flaw detection, focused on identifying discontinuities (macrodefects) in welded joints, cannot reliably assess quality in the early stages of crack development. In this regard, metal magnetic memory (MMM) testing offers practical potential for comprehensive DMW inspection, including both flaw detection and stress-state assessment. The MMM technique (ISO 24497) is based on analysis of the self-magnetic stray field (SMSF) distribution formed during welding and operation. Results of comprehensive DMW inspection using the MMM technique are presented in this study. Areas of abnormal SMSF variation correspond to degraded microstructure and mechanical properties, leading to stress concentrations. Cracks subsequently form and propagate in these stress concentration zones (SCZs). Detecting SCZs helps to prevent impending DMW failures at earlier stages.

Keywords: defect, metal magnetic memory, nondestructive testing, stress analysis, weld

Materials Evaluation 84 (5): 37–43 | https://doi.org/10.32548/2026.me-04568 | ©2026 American Society for Nondestructive Testing

Introduction