Surface hardening treatment is used to have strength to mechanical parts, and carburizing and quenching are the most widely used. There are
reports on various carburizing efforts to deal with recent environmental issues. The authors have proposed an ultra rapid carburizing above the eutectic
temperature, due to realize in–line carburizing. Since this is an unprecedented carburizing treatment method, setting the carburizing conditions that are
suitable for efficiency has been the future challenge.
In this paper, we investigated a method for predicting the carbon concentration profile in the steel based on the known carburizing reaction mechanism of ultra rapid carburization. In order to predict
the carbon concentration profile in the steel, it was calculated by the finite difference method using the carbon penetration rate F, the use of F ¼ 4:04 1011eð1:20102TÞ which penetrates from the surface, and
the carbon diffusion in the steel based on Fick’s law. In addition, among various carbon diffusion coefficients Dc, the use of DcðT;CÞ ¼ 4:53 107f1 þ 1 T2:221104 Þð17767yc g 26436Þ ð ycð1 ycÞ which takes
into consideration the dependence of carbon concentration, gave a good agreement with the actual measurement results by EPMA. Furthermore, as a result of investigating efficient carburizing conditions
using a prediction method, we could minimize the time required to obtain an effective case depth of 0.8 mm. In addition, the amount of carburizing gas used was also reduced. In other words, it suggests that the accumulation of a huge amount of
condition data and the condition setting skills are no longer necessary.