W. Grafen, Ipsen International GmbH, Kleve, Germany

Summary: Since some years, the low-pressure carburising process is used in the automotive and aircraft industry, especially for the treatment of injection bodies and the transmission components. Next to the main advantage of a structure without internal oxidation, the low-pressure carburizing process yields additional benefits like low distortion values, no post-washing, low consumption costs and positive environmental aspects by utilizing high-pressure gas quenching. In today’s industry the low-pressure carburizing process is carried out with the hydrocarbon gases propane, ethylene and acetylene. Because of the various carbon contents and different crack reactions, the carbon transfer properties vary and show the possibilities and the limits of the hydrocarbon gases. This paper describes new aspects of the carbon transfer of acetylene as a function of pressure, gas flow, temperature and durations. With the right combination of these parameters the process can be controlled easily, the results of heat treatments are optimised and the production of tar and soot is prevented. With some industrial applications these positive effects of the technology are shown.