Induction welding and heat treatment of steel pipes: evolution of crystallographic texture detrimental to toughness

Steel welding using induction heating to produce pipelines is found to have lower toughness at the weld junction than the base material, even after a heat treatment which reaustenitises the weld zone. Detailed crystallographic characterisation indicates that the poor toughness is due to the crystallographically coarse grains present after welding; the coarse scale is not visible using just optical microscopy. The post-weld heat treatment does not improve the situation at the weld junction, because the detrimental crystallographic characteristics are reproduced on cooling.