Metallurgical analysis of SA-106 Gr. B pipe failure during hot bending

• Root cause for the failure of SA-106 Gr. B pipe during operation was analyzed and reported.
• Results indicated that cracks developed due to higher inclusion content coupled with over-stress.
• Over-stress was caused due to sudden thermal expansion during induction heating process.
• Analysis and suggestions are helpful for similar components where this grade of material is used.

This investigation deals with failure analysis of SA-106 Gr. B pipe which is a Carbon-Manganese steel used for moderately high temperature applications in industries. A transverse/ circumferential crack was formed in SA-106 Gr. B steel pipe during hot-bending operation. Visual examination and stereo-microscopic analysis indicated the presence of globules on the intrados surface of the pipe and towards the inner section on the crack surface. The globules had dendritic morphology which indicated the melting of the metal caused by temperature hike. Detailed analysis of the microstructure clearly indicated the presence of groups of inclusions. These inclusions coupled with over-stress due to sudden increase in temperature during induction heating led to the formation of cracks and caused failure of the pipe.