Heat Transport in a Stainless Steel at Very Low Temperatures

Abstract

THE thermal conductivity K was determined for two stainless steel tubes at several temperatures in the range 1 < T < 4° absolute. The identical specimens were of 5.50 and 6.00 ± 0.01 mm internal and external diameters, respectively, and length 7 cm. Electrically introduced heat fluxes pass along the tubes (except for negligible losses by conduction, convection and radiation through the surrounding gas, which is at a pressure of less than 10⁻⁵ torr). Steady-state temperature gradients were attained eventually, and measured using carbon resistance thermometry with a vernier potentiometer¹. Corrections (≲ 1 per cent) to the apparent thermal conductivities were applied for the ‘by-pass’ effect of the thermometry leads. The stainless steel was F.D.P. quality (Accles and Pollock), fully annealed, of composition: iron ∼ 73 per cent, chromium > 17 per cent, nickel > 8 per cent, manganese < 2 per cent, silicon > 0.2 per cent, carbon < 0.15 per cent, sulphur < 0.04 per cent, and phosphorus < 0.04 per cent.