Comparison of the Temperature Gradients Found in Inert-Gas and High-Vacuum Furnaces

In a resistance-heated furnace with automatic temperature controls, the programmed heating cycle ensures a certain constancy and uniformity of the work temperatures. If the heat is transmitted by radiation only, that is if we are in a high-vacuum environment, the system is more “symmetric” than if the heat transmission by convection exists, because the presence of air or inert gas alters the temperature distribution. These measurements were carried out in the interval 600–1000°C, in an experimental furnace having a particular geometrical arrangement in order to facilitate the interpretation or extrapolation of results. Basically the same automatic cycles were followed which have been adopted for industrial processes such as hardening or brazing. Temperature data are reported, for both cases of high vacuum and inert gas. A discussion will follow upon the effects of different arrays of thermocouples and the attainable precision.