On the Floating Zone Refining of Pure Iron

Samples of vacuum-melted re-electrolysed iron were zone-refined by the floating-zone melting method in hydrogen gas, with the zone passed seven times at the velocity of 1.1 mm/min. Low-temperature resistivity measurements, quantovac analysis, and gas analysis were performed for estimating the refining effect and impurity distribution. The highest purity was found in the middle portion. This floating-zone refining method was effective for C, P and S, but we did not observe the refining effect for Mn and Si. O, N and H were eliminated effectively. The growth rate of the re-crystallized grains was markedly greater in the highest-purity part, and the ratio of the mean grain sizes of the pure and impure parts was 9:1.