Abstract: An apparatus for the treatment of components by means of a gas mixture, comprising mainly a first light gas and minor amounts of a second gas being heavier than the first gas, has a treatment chamber (10) in which the treatment occurs and a concentration, and purification device (19, 29, 30) in which the gas mixture is concentrated and purified to increase the concentration of the first gas. The treatment chamber (10) comprises an outlet member (19) provided in an upper part of the treatment chamber (10) and means (14, 15) being arranged to move the gas mixture upwardly and out through the outlet member (19). Said means may comprise an inlet member (14) provided in a lower part of the treatment chamber (10) and arranged to supply additional gas and to admit a laminar inward flow of said additional gas.

Abstract: Steel is carburized at a temperature within the austenitic range and in an atmosphere which comprises nitrogen, hydrogen and carbon monoxide, by lowering the hydrogen concentration in the treatment atmosphere prior to cooling steel in oil, salt or water, so as to reduce the hydrogen concentration in the carburization layer of the steel, by outward diffusion of hydrogen from the carburization layer.