Article ID: MT-M2025025
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=4.04×10−11e(1.20×10-2・T), 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 Dc(T, C)=4.53×10−7{1+yc(1-yc)8339.9/T}・e{-(1/T-2.221・10-4)(17767-yc・26436)}, 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.
This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 87 (2023) 179–185. Reference [3] was added as the English translation edition of Ref. [2]. In Ref. [14], book title was corrected.
