Techniques for Melting-Point Determination on an Electrically Heated Refractory Metal

Abstract

THE measurement of the melting point of a material requires determination of temperature within allowable limits of accuracy at precisely the moment when the change of state occurs. At intermediate to high temperature, a disappearing filament optical pyrometer is the most convenient temperature measuring instrument. A method which has been used extensively is the direct observation of a test fragment within a black-body furnace in which the temperature can be increased gradually until visual evidence of melting is obtained, that is, the sudden rounding of a jagged edge or pinnacle. A severe drawback in this procedure is the fact that the test sample is difficult to discern since its temperature is essentially the same as that of its environment. Furthermore, it is difficult to melt the refractory metals in a black-body furnace.