Decarburization is a well known phenomenon in sintering. In addition to the effect of agents from the atmosphere, also the natural oxygen content of the starting powders causes loss of carbon, C being the dominant reducing agent at least at higher temperatures. In both cases, CO/CO2 are the reaction products. Formation of CH4 is less common, although it has been reported in older references. Here it is shown that methane formation during sintering in hydrogen atmosphere occurs to a low degree in plain carbon steels, more pronouncedly in Cr alloyed ones and still more in case of Mn alloying. In all cases, the critical temperature range is the transition temperature range 600
800°C; methane formation can be observed not only during heating but also during cooling. For these types of sintered steels, therefore, fairly fast heating and cooling within the critical temperature range is recommended to avoid carbon loss.