The change influence of 6.9% and 13.6% two austenite contents and 0 ~ 20% pre-strain process on mechanical properties of medium manganese steel 5 mm plate is analyzed by the test method of 610℃ 5 h furnace cooling and 800℃ 20 min W. C. +625 ℃ 12 h A. C. two heat treatment and 0 ~20% pre-strain process. The amount of retained austenite in the steel is determined by X-ray diffraction analysis and its mechanical properties are measured by tensile test. Research results show that at the same pre-strain level

compared to the sample with 6.9% austenite volume fraction

the sample with 13.6% austenite volume fraction has lower yield strength by about 30 MPa

higher tensile strength about 40 MPa

lower yield strength ratio by about 0.1

higher total elongation by about 7 percentage point

and more obvious work hardening behavior. At the same austenite content

with the increasing of pre-strain

the yield strength

tensile strength and yield-strength ratio increase

the total elongation decreases. With the increasing of true strain

the work hardening behavior can be divided into four stages:decreasing (stage I) increasing (stage II)

almost unchanged (stage III) and decreasing (stage IV).