The Embrittlement of Low-Carbon Steel

The paper deals with those changes in the mechanical properties of steel having a low carbon content, which occur as a result of quenching from temperatures up to 900 deg. C. Attention is directed mainly to brittleness, especially to that resulting from ageing at atmospheric temperature, which the authors term “age embrittlement.” The range of temperature in which this occurs appears to include those temperatures used in the carburizing treatment of steel as well as lower temperatures. It is suggested that case-hardened steels should be subjected to a final tempering treatment after quenching to avoid the possibility of core brittleness. Theories are briefly discussed, but at present no direct explanation of the phenomenon is forthcoming, as X-ray and microscopic examination reveal no abnormalities in the age-embrittled steel. Ageing at 100 deg. C., after quenching, shows distinct age hardening, but this is found to be dissociated from age embrittlement.