Different heat treatment cycles were designed in order to investigate the effect of microstructural changes on hydrogen induced cracking resistance (HIC) and mechanical properties of the electric resistance welded steel. The heat treating of the as-welded specimen improved the ductility and impact toughness. After heat treatment, the uniform hardness profile was obtained for the welded specimens. The removal of local hard zones reduced the risk of HIC. The chemical composition and clustering of inclusions have a deleterious effect on cracking resistance in the H2S environment. Aluminosilicate compounds and MnS inclusions were favorite sites for HIC. The most promising post weld heat treatment for improving mechanical properties and the resistance to HIC was the application of twocycle quenching followed by tempering.

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