Abstract: Microstructure and mechanical properties of lowcarbon martensite steel obtained by different heat treatment conditions were studied. The results showed that the salt bath quenching heat treatment can achieve rapid and uniform heating. Compared to conventional heat treatment conditions， the austenite grain size has not grown up at the early stages of fully austenitic or nearly fully austenitic due to the fast heating speed and short heat preservation time， so the fine martensite microstructure was obtained by quenching and the martensite steel has excellent mechanical properties simultaneously. Through the heat treatment parameters optimization， the tensile strength and elongation increase more than 10%. Under the 930℃×20s salt bath quenching， the martensite steel’s tensile strength is 1488GPa and the elongation is 76%.

Key words: lowcarbon martensite steel, quenching heat treatment process, austenite, microstructure, mechanical properties