Abstract
Molybdenum was purified by arc-melting in Ar-H2 (H2: 0-30 vol%) gas mixture. The impurity content in the ingots was measured by chemical methods and Auger electron spectroscopy. The mechanical properties of the cast molybdenum was evaluated by a bend test and an impact compression test in the temperature ranges from 200 to 1223 K and from 473 to 780 K, respectively.
A molybdenum ingot with a purity of about 99.99 mass% was obtained by the arc-melting in gases containing hydrogen. However, when the hydrogen concentration in the atmosphere exceeded about 10 vol%, the DBTT of the ingot abruptly increased. This increase was considered to be caused by the excessively dissolved hydrogen during the melting. The ingot melted in the gas mixture of which hydrogen concentration was less than 5% nearly has the same DBTT as that by electron-beam melting. Such ingots could be worked without cracks along grain boundaries at 570 K.
