Fracture Toughness of Explosive Stainless-Clad HT80 High Strength Steel

Abstract

Fracture toughness of explosive clad composed of SUS 304 stainless steel and HT80 high strength steel is investigated. To clarify the effect of metallurgical properties and composite structures on the fracture toughness, both V-notch Charpy test and bending COD test are carried out by using homogeneous and heterogenous specimens which are cut from various portions in thickness direction of the clad plate and have notch root or precrack leading edge parallel to the plate surface. The energy absorbed for fracturing the specimens and its component energy for crack initiation from notch root in V-notch Charpy test are affected by the material involving notch root and by the thickness ratio of two different steels in net section of specimen.
In static bending test of the heterogeneous specimens with pre-crack tip in stainless steel, fracture occurs in the high strength steel adjacent to weld interface before the pre-crack extends although ductile fracture occurs at pre-crack tip over all temperature range. In relation to crack initiation, the critical COD, if the first fracture initiation in interface zone can be measured, and the stretched zone width, if fracture firstly occurs at pre-crack tip, can be a parameter of fracture toughness respectively.
In the heterogeneous specimens with pre-crack tip in high strength steel, both the critical COD at low temperature where ductile fracture has not yet initiated and the stretched zone width over all tem-perature range can be fracture toughness parameters since the fracture toughness values depend largely on the material involving pre-crack tip, namely, high strength stecl.