Temperature control in heat treating is of paramount importance in maintaining the quality and achieving the desired metallurgical results. This article provides a detailed account of the factors affecting temperature control in heat treating furnaces, with information on temperature control systems, including contact sensors, noncontact sensors, controllers, energy-flow regulators, measurement instruments, and set-point programmers. Common contact sensors include temperature scales, thermocouples, and resistance temperature detectors, whereas optical pyrometers and on-line radiation thermometers fall under the noncontact type. The article describes two types of instrumentation used in heat treating: field test instruments for temperature-uniformity surveys and system-accuracy tests; and controlling, monitoring, and recording instruments for digital instrumentation.

This article provides an overview of the basic theory of infrared (IR), including emissivity and E slope. It explains how the IR thermometer works, and provides guidance on choosing a thermometer, in particular, deciding between a two-color and a single-wavelength thermometer and installing and maintaining them. The article discusses typical applications of induction heating, and describes how the IR thermometer controls the temperature. While the majority of the article discusses spot thermometers, thermal imagers, which are fast and are used for both research and control of the induction process, are also addressed.