Abstract
To make clear the major factor determining the critical strength for delayed fracture of high strength bolts exposed to moist atmosphere, the role of interdendritic microsegregation bands in hydrogen assisted delayed fracture of a quenched and tempered steel has been investigated.
In interdendritic segregation bands enriched in Mn which promotes the segregation of P at prior austenite grain bounderies, hydrogen makes it easy to produce intergranular cracking. From these observations, it may be concluded that delayed fracture of high strength bolts is controlled by intergranular cracking in a microsegregation band which exists in the triaxially stressed region.
