鎚打した高Mn鋼の熱膨張変化の原因

抄録

Hammered Hadfield steel first contracted in the temperature range 80∼180°C and then rapidly expanded at about 200°C in dilatation curves. These changes were observed similarly for steel hammered at room temperature as well as at liquid-air temperature. Hammered steel, isothermally heated at about 150°C, contracted with longer holding time, but it appeared that the steel has the tendency of expansion after the contraction was saturated, and to expand sharply by rise of temperature after isothermal heating. The activation energy of this contraction was about 35,700 cal/mol by isothermal dilatation method. Steel with higher manganese content than Hadfield steel only slightly contracted in thermal dilatation curve. Therefore, it is considered that this contraction is due to the movement of carbon atoms in austenite, and also the rapid increase of thermal expansion at about 200°C is certainly due to expansion by transformation of the ε phase formed by hammering to γ phase.