Abstract
In order to control the surface carbon content of gas-carburized steels, the effects of alloying elements on equilibrium carbon content of low alloy steels based on JIS SCr420 grade were investigated. 1.0mm and 0.3mm thick specimens were carburized for 108ks or 288ks. As the carburizing time was long, the carbon content of the specimens deviated from the equilibrium value based only on the carbon potential in the atmosphere while excluding oxygen potential. The deviation was affected by Si, Cr, V content which are oxidized in the surface layer.
These results show that the equilibrium carbon content in gas carburizing atmosphere is also affected by oxygen potential in the atmosphere ; i.e. surface oxidaiton of alloying elements decrease the amount of the alloying elements in austenite, which changes the activity coefficient of carbon. Furthermore it is indicated that the growth of oxide results in re-carburization or decarburization. Therefore, oxygen potential in gas carburizing atmosphere is one of the important variables affecting the surface carbon content of gas-carburized steels.
