On the Age-Hardening of Mn-Cr Austenite Non-Magnetic Steels Containing Vanadium

An investigation was made of the changes in hardness and microstructures of 17Mn-12Cr austenite steel containing up to 0∼2.7%V when aged or tempered after solution treatment. The result are as follows: (1) The hardening responses of Mn-Cr austenite steels containing vanadium (0∼2.7%) occur by aging or tempering after solution treatment, and the hardening increases with vanadium content. (2) The temper hardening of 17Mn-12Cr austenite steel containing no vanadium takes place from the tempering temperature of 800°C and the hardness peak is obtained at the tempering temperature of 1000°C. This hardening has some relation with the precipitation of the MC type carbides. (3) The temper hardening of 17Mn-12Cr austenite steels containing vanadium results in the hardness peak at the tempering temperature of 800°C, and is chiefly concerned with the precipitation of very fine VC carbides. (4) The temper hardening of the steel containing 0.6% vanadium takes place with two hardness peaks, i.e., the first peak at 800°C, and the second at 1000°C. The first peak takes part in the precipitation of VC carbides, and the second peak has relation with the precipitation of carbides of the MC type. (5) The tempering age hardening responses of 17Mn-12Cr austenitic steel containing 2.1% vanadium corresponds to the continuous transition of the precipitate from the intermediate phase coherent with the austenite matrix to the equilibrium phase of VC carbide. The precipitates can not be observed at the early stage of the hardening. At the stage of the hardening peak, considerably fine particles of the precipitates are observed to be distributed uniformuly in the austenite grains.