酸化鉄の還元と浸炭の相関に関する研究

抄録

The relationship between reduction and carburization has been investigated, by way of the reduction experiments of highly pure chemical hematite (Fe₂O₃) at high temperatures in CO gas as well as in solidcarbon-N₂ atmosphere, followed by the microscopic examination on various samples of reduced iron oxide. The results are summarized as follows;
1) In the CO gas atmosphere the rate of reduction becomes rather slow at the temperature higher than about 1100°C, whereas in the solid-carbon-N₂ atmosphere the reduction proceeds with a notably high speed in the same region of the temperature. Namely a contrast effect on the rate of reduction is shown between these two atmospheres.
2) In either CO gas atmosphere and solid-carbon-N₂ atmosphere at higher temperature, the carburization does not begin to proceed unless the reduction degree exceeds 90% (for the sample of φ10mm×10mm).
3) The lattice constant of α-Fe (110) yielded by reduction varies with the progress of reduction.
The lattice constant has a comparatively larger value at the beginning of reduction than the usual one, and tends gradually with the progress of reduction to a constant value slightly larger than the usual one. This gradual change of the lattice constant seems to stop when the process of carburization which follows up reduction begins.
4) The process of carburization is analyzed by means of the following diffusion model:
1/D·∂C/∂t=1/r·∂C/∂r+∂₂C/∂r₂+∂₂C/∂Z₂
The result shows that the coincidence between the calculated values and experimental ones satis factory.
5) As a consequence of the above theoretical analysis for the process of carburization, it has been shown that the diffusion coefficient D has the nearly same value 0.79×10^-4 (cm/sec) in either case of 1200°C and 1300°C, on the other hand, the (equivalent) rate constant k is computed 2.61×10^-4 (cm/sec) for the case of 1200°C and 3.15×10^-4 (cm/sec) for the case of 1300°C.