Abstract
A commercial 1Cr-1 Mn steel has been investigated in the temper-embrittled condition in relation to sensitivity to hydrogen stress cracking. The work involved delayed brittle failure tests on smooth steel specimens which were stressed in tension under constant load, while being charged with cathodic hydrogen at a constant current density. Both the relative range of stresses for susceptibility to hydrogen stress crack ing and the overall rate of delayed failure were found to be maximal for specimens which had been tempered at 500 - 550 C, i.e. where grain-boundary impurity segregation and temper embrittlement were also at a maximum. While the intergranular weakness induced by impurity segregation appears to be responsible for lowering the time required to propagate a crack to the critical point for delayed failure, some interaction between hydrogen and impurity elements appears to cause the increase in susceptibility to hydrogen stress cracking.
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