Fe-C 2元系混合圧粉体の焼結について

抄録

The sintering characteristics of the Fe-C binary mixed powder compacts containing up to 3.0 wt%C were investigated by the dilatometric method. Three kinds of Fe-1.0 wt%C binary mixed powder compacts; each containing electrolytic, atomized and reduced iron powder with different H₂ loss, were used in order to examine the process of the carbon diffusion into iron and the decarburization, by means of the dilatometric method, measurement of the degree of vacuum and the carbon analysis.
The results obtained are summarized as follows:
(1) After the α→γ transformation during heating in vacuum of 10⁻⁵ mmHg for the Fe-C binary mixed powder compacts, the expansion was observed, the amount of which was nearly in proportion to the amount of additional graphite, and the expansion curve in dilatation and the combined carbon concentration curve well agreed. This means that the carburization was done mainly by the carbon diffusion through the contacting surface of graphite and iron powder rather than through the medium CH₄ or CO gas.
(2) From the vacuum measurement, it was apparent that the amount of gas discharge from the specimen with the reduced iron powder was by far larger than that from the other specimens. On the contrary, its dilatational expansion was minimum, indicating that the specimen was not swelled by the gas pressure.
(3) Carbon diffusion into α-Fe was scarcely observed in H₂ gas sintering, while in vacuum sintering carbon diffusion into α-Fe was about 0.1 wt%. However, the carbon diffused into γ-Fe more rapidly in H₂ sintering than in vacuum. Consequently the dilatational expansion in the former was larger than in the latter. A similar relationship between the dilatational expansion curve and the curve of carbon concentration in vacuum sintering was also applicable to the case of sintering in H₂ gas.