メタンを用いた真空浸炭における鋼の浸炭挙動

抄録

Carburizing behavior is clarified by investigating the effects of carburizing conditions, i.e., temperature, time and methane pressure, on case depth, surface carbon content and rate of flow of carbon into the steel, namely, the flux of carbon. A steel, SNCM 815, was carburized at temperatures from 1193 to 1313 K for times up to 14.4 ks under methane pressures from 13.3 to 80.0 kPa. Carbon concentration-distance curves were determined by a succession of grindings and emission spectrochemical analyses of the ground surfaces. The chemical reaction controll brings about a constant flux of carbon until the surface carbon content reaches the solubility limit of carbon. The carburizing is thereafter controlled by carbon diffusion within the steel. A mathematical model is presented for describing the behavior mentioned above. Comparisons between the calculated and the experimental carbon concentration-distance curve reveal that the concentration dependence of diffusion coefficient of carbon plays an important role in the carburizing behavior.