Abstract
A process to prepare high purity iron with good reproducibility has been established. The purification process mainly consists of anion exchange in a medium of hydrochloric solution, reduction to the metallic state, floating zone melting in vacuum and wet hydrogen treatment. Several analytical methods: activation analysis, emission spectrum and atomic absorption are used to confirm the separation of main impurities in each process. Effective combination of several purification processes is selected by considering these analytical results along with the measured values of RRRH. The anion exchange method is known to be very effective and this process consists of two steps. The first step is performed in an eluant solution of ferrous chloride and the second one in that of ferric chloride. Since the ferric chloride solution is stable against oxidation, the separation in the ferric chloride solution can be easily repeated several times. The highest value of RRRH obtained for the purified iron is 9840 and the greater part (about 70%) of the purified iron gives a value of RRRH larger than 7000.
The recrystallization temperatures for the iron samples with various RRRH are measured by a isochronal annealing procedure. The sample with RRRH of 8700 recrystallizes at a temperature of 260°C. It is shown that the recrystallization temperature is closely related to the impurity content for the same kinds of remaining impurity elements.
