On the Equilibrium Diagram of Manganese and Carbon Alloy

The equilibrium diagram of manganese and carbon system was studied with distilled manganese and sugar charcoal. In this alloy scries, seven kinds of solid solutions, α, β, γ, δ-manganese solid solutions, αC, βC and γC solid solutions, existed and their existing regions were clarified, On solidification, three kinds of peritectic reactions occurred at 1235°, 1260° and 1340℃, respectively, and in the solid state, two kinds of peritectoid reactions existed at 857℃ and 1010℃, respectively, and two kinds of eutectoid reactions at 820℃ and 950℃, respectively. α-Manganese dissolved about 0.3 per cent of carbon at room temperature, and 1.0 per cent of carbon at eutectoid temperature 820℃. Maximum solubility of carbon in β-manganese was 0.05 per cent at 857℃. γ-manganese dissolved a comparatively large amount of carbon, say, 2.95 per cent of carbon at 1260℃. Solubility of carbon in δ-manganese at 1235℃ was 0.12 per cent. αC solid solution was a new phase recognized first by the present writer. It contained more than 7.0 per cent of carbon, and was conceived to be manganese carbide Mn_2C (9.85%C) with dissolved manganese. Manganese carbide Mn_3C which had been supposed to exist, was not recognized \u27in the present reseach. βC solid solution was observed in the alloys containing more than 3.05 per cent of carbon at high temperatures. Quenched βC solid solution was comparatively stable at room temperature and the so-called weathering phenomenon scarcely occurred under this condition. The γC solid solution produced by the peritectoid reaction at 1010℃ was also found newly by the present writer, the composition of which seemed to be about Mn_4C (5.18%C). This phase existed at room temperature in the range from 4.3 to 4.6 per cent of carbon