Temper brittleness of 0·3C–Cr–Mn–Si–2Ni steel with various initial microstructures

Impact toughness, microstructure, and internal friction were examined for 0·3C–Cr–Mn–Si–2Ni steel with quenched, austempered, normalized, and annealed initial microstructures. It was found that the steel has appreciable susceptibility to temper brittleness with all these microstructures. The mechanism of temper brittleness in this steel was proved to be the result of an aging process of the α solid solution with precipitation of Fe₃C(N) particles causing ‘dead pinning’ of dislocations.