STRENGTH PROPERTIES AND MICROSTRUCTURE OF HIGH MN-CR AUSTENITIC STEELS AS POTENTIAL HIGH-TEMPERATURE MATERIALS

The present authors have investigated the high temperature strength, t oughness and microstructural phase instability of 12%Cr-15%Mn steels, for the development of high Mn-Cr austenitic steels as heat resisting materials. While high content of carbon and nitrogen (0.1 to 0.2 mass% C and N) and combined addition of vanadium and titanium were effectiv e to increase the creep-rupture strength considerably compared with th at of the regular type 316 steel or Tenelon, such addition of the elem ents deteriorated the toughness of the materials because of the large amounts of coarse precipitates of type M(23)C(6) carbide and also fine precipitates of TiN. It was clarified that the reducing of carbon con tent to 0.02 mass% C improved much the toughness of the 12%Cr-15%Mn st eel and also produced the creep-rupture strength which is comparable w ith that of the 316 steel.