A method for measuring the composition of gas bubbles in metals

Abstract In solidified metal, microscopic gas filled cavities may be present. They can originate from either gas bubbles in the melt or gas that has separated from the metal during solidification. A method has been developed to identify and open the cavities under vacuum and to determine the gas composition quantitatively. Having localised the cavity by ultrasonic methods and by X-ray imaging the method consists of drilling a hole to the cavity by ‘vacuum drilling’ equipment, and, finally, the mass-spectrometric analysis of the released gas. An example is given of a 2.5 mm sized spherical cavity in cast steel, which contained 0.4 bar of a gas mixture of Ar, N 2 , and H 2 at room temperature.