DEW POINT MEASUREMENT IN METAL HEAT TREATING

摘要

Metal heat treatments such as annealing, carburizing, and carbonitriding require furnace atmospheres that have controlled water vapor concentrations. Measurement of atmosphere dew point temperature is widely used to provide meaningful data to help heat treaters monitor water vapor concentration and optimize the process. Condensation (optical chilled mirror) hygrometers, metal oxide sensors, and thin-film polymer sensors are among the available technologies. Common heat treating terms are defined in the sidebar. Some of them describe processes in which atmosphere control is a distinct "science." Metallurgists have the knowledge and ability to change a process "recipe" to alter the characteristics of the material being heat treated, and the moisture parameters of the process are very important to final properties. Repeatability also is required: Every time the product is heated, the energy used must produce the desired result. Dew point monitoring of these processes is critical since expenditures for the gasses and energy needed to maintain their atmospheres are primary cost drivers. Reworking a product rejected due to an incorrect atmosphere analysis is often not an option.