On the Determinations of Gases in Iron and Steel by Vacuum Fusion Method Using Graphite Capsule

Abstract

In order to eliminate the disadvantages occured on vacuum fusion method using graphite crucible for determining the gases in iron and steel, the technique using graphite capsule was investigated in this report.
The content of gas in graphite capsule are minimized by previous de-gassing and the following storage in vacuum, so that the oxygen and nitrogen in iron are satisfactorily determined. On the other hand, numerous experiments have been carried out to estimate the effects of the elements dissolved in iron, and the following advantages are detected for the capsule method:
1. The getterings of oxygen and nitrogen by dissolved metals having high vapor pressure do not occur.
2. The gases such as CO₂, COS and SO₂, which are formed in carbon-saturated melt containing S or volatile oxide, are converted into CO.
3. As the formation of viscous melt due to the growth of precipitated graphite in flake form is disturbed, the extraction rate of gas is promoted.
In addition, as the increase in the solubility of gas in the melt does not concern with incomplete degassing of the gas in its melt on wide concentration range of steels, vacuum fusion method using graphite capsule is suitable for a routine analysis of oxygen in commercial steels.