The thermal and electrical conductivities of metals and alloys: Part 2, some heat-resistant alloys from 0 C. to 800 C.

Abstract

A comparative longitudinal-flow method has been used to determine the thermal conductivities, up to temperatures approaching 800°C., of F.N.C.T., F.H. stainless, Staybrite and Era A.T.V. steels, and of monel metal and an alloy composed of approximately 80 per cent of nickel and 20 per cent of chromium. The values are derived in terms of the thermal conductivity of a specimen of nickel-plated iron which had been previously tested over the full temperature-range. Determinations of the electrical resistivity are made in the course of the same experiment, and values of the Lorenz function are derived. Whereas at atmospheric temperature the values of the Lorenz function for these metals are abnormally high, and vary from 0.76 × 10-8 for the F.N.C.T. steel to 1.18 × 10-8 for the F.H. stainless steel, they decrease towards a common value with increase in temperature, and at 800°C. all lie between 0.62 × 10-8 and 0.68 × 10-8. An examination of values obtained for the Lorenz function of metals by other workers reveals that the extreme values so far published for this function over the temperature-range 400° to 1000°C. are 0.56 × 10-8 and 0.80 × 10-8. It is concluded that the thermal conductivity of a metal can be predicted with a fair degree of approximation over this range of temperature from a knowledge of the electrical resistivity, and that in general the probable error involved decreases as the temperature increases.