Pages 247-248
A large 3.5 inch thick compact tension specimens (CT) were hydrogen pre-charged in an extra high capacity autoclave and crack growth tests were conducted on temper embrittled 2.25Cr-1Mo steels. The recent generation steel with high purity, less temper embrittlement susceptibility, showed sub-critical flaw growth over 10 days at room temperature. The crack growth rate observed was relatively constant rate at 5 to 8x(10)^<-5> mm/sec regardless of the slow increase or decrease in stress intensity factor at the crack tip. On the other hand, the temper embrittled 60's generation steel showed brittle, fast fracture at low stress intensity factor (K_1=45 MPa√<m>). Since the fracture toughness of this steel without hydrogen condition was higher than this, it is considered that the fast fracture was occured due to the presence of hydrogen. This fast fracture took place remarkably below 86℃.
