Effect of Dissolved Oxygen on the Rates of Evaporation of Molten Iron and Copper

Abstract

The evaporation rates of liquid iron and copper under reduced pressure of 0.001-600mmHg Ar were measured at several temperatures by using a micro balance.In the pressure range of less than 0.1mmHg Ar, rates of evaporation are independent of argon pressure, although evaporation rates under argon atmosphere of more than 0.1mmHg decrease with increasing pressure of argon, probably because of the collision between the evaporated metal atoms and argon molecules as described already by previous investigators.It is also found that evaporation rates for both metals decrease with increasing oxygen concentration in molten metals. Considering that oxygen dissolved in liquid metal is a surface active element, it seems reasonable to consider that rates are controlled by the evaporation reaction at metal surface where oxygen adsorbs. Namely, the present results suggest that most of metal atoms vaporize at oxygen free sites.Moreover, it is found that the values of surface tensions of molten metals estimated from the present work agree well with those in literatures.