Effect of single quenching on the microstructure and properties of large thickness marine steel FH790
The mechanical properties and microstructure of large thickness marine steel FH790 at different thickness positions after single quenching and tempering heat treatment were studied and analyzed by ad-vanced methods,including mechanical testing equipment,optical microscopy(OM),scanning electron mi-croscopy(SEM),and transmission electron microscopy(TEM).The results showed that the yield strength and tensile strength at different thickness positions of large thickness marine steel FH790 after only single quenching and tempering heat treatment had little difference,which could meet the classifica-tion society rules.However,the average impact energy at the 1/4 thickness(T/4)position was 58 J,and the average impact energy at the 1/2 thickness(T/2)core position was 26 J,which could hardly meet the classification society rules.The main reason was that there was a large amount of tempered granular bain-ite structures in the core of marine steel FH790 with a thickness of T/2.And the effective grain size of this microstructure was relatively large,which resulted in relatively poor impact toughness of the steel plate.
large thickness marine steel FH790microstructureimpact toughnessmartensite structurebainite structure
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