Atmosphere Control during Low-Pressure Carburizing

Abstract

　Atmosphere control during low-pressure carburizing is important from a quality assurance viewpoint. We have developed a low-pressure carburizing furnace that can be used for mass production, which has an atmosphere control system comprising a thermal conductivity hydrogen sensor and an oxygen sensor.
　The hydrogen sensor is used for providing an atmosphere control necessary for carrying out both low-pressure carburizing and carbonitriding processes. The oxygen sensor detects air leaks and sooting in the furnace. In this paper, we demonstrate that when the atmosphere during the low-pressure carburizing and carbonitriding processes is controlled using the hydrogen sensor, the amount of carbon and nitrogen infiltrated into the steel parts can be controlled, even if the parameters such as the flow rate of gases, temperature, and the surface area of the parts change.