Probe for the determination of gas concentration in molten metal

Abstract

The invention provides a new immersion head probe for use in apparatus for the determination of the concentration of gas dissolved in a molten metal. Such determinations are needed to facilitate removal of the gas, which can cause bubbles in the solidified metal and subsequent processing difficulties. The apparatus circulates an inert carrier gas through the probe in gas exchange contact with the molten metal to entrain dissolved gas until an equilibrium mixture is obtained; the concentration of the dissolved gas in the mixture then is representative of its concentration in the molten metal. The head consists of a monolithic or integral body of a porous gas-permeable material of sufficient mechanical strength at the temperature of the molten metal and of sufficient porosity, pore size and permeability to permit the necessary gas diffusion in a reasonable period of time. The body of the probe preferably is thin in one direction to minimize the path length for the gas to diffuse therein, and is provided with a carrier gas inlet and outlet suitably spaced apart to ensure that the gas diffuses throughout the body. If the test is to be carried out in a stationary body of molten metal, the probe may be vibrated or the metal may be stirred to increase the probe/metal contact, both decreasing the time required for the gas mixture to reach sufficient equilibrium.