It is difficult to remove oxygen from iron by a dry H₂ treatment in a temperature region of α-iron. In the present study, however, it is found that oxygen as well as carbon and nitrogen in iron can be reduced to less than 1 wt ppm by the dry H₂ treatment in a temperature region of δ-iron.
The results obtained are summarized as follows:
(1) The purification described above can be attained by the dry H₂ treatment at 1500°C for only 3 h even though the initial oxygen content and the size of rod specimens are as large as 730 wt ppm and 10 mmφ, respectively.
(2) The present purification method can be applied by the use of a less sophisticated apparatus.
(3) When impurity contents are far exceeding the solubility limit, the corresponding diffusion equation can be approximately solved under a quasi-stationary condition. The approximate solution describes very well the present experimental results.