Effects of the carbon addition and heat treatment on physical and mechanical properties were studied. The results obtained were as follows :
(1) The addition of carbon to iron-manganese alloys lowers the density and increases the porosity, but has a goot effect of improving the sintering between iron and manganese.
(2) Sintered manganese steel with the austenitic structure has good mechanical properties, particularly high impact energy, though the porosity of sintered compacts is higher than 150.
(3) In order to obtain homogeneous austenitic microstructure it is necessary to add high manganese and high carbon, for example C 2.0% for Mn 100 or C 1.2% for Mn 20% with sintering at 1200°C. (4) Mechanical properties are little affected by solution-treatment, but injured by heating at above about 400°C after solution-treatment. The hardness has the maximum value at a temperature of 500-600°C, since the platelet carbide precipitates at these temperatures.