低合金肌焼鋼の焼入性と変態挙動へおよぼすAlとNの影響
1983 年 69 巻 3 号 p. 452-461
詳細
1983 年 69 巻 3 号 p. 452-461
The influences of Al and N on the hardenability and the transformation characteristics have been investigated for low alloy case hardening steels (JIS SCM420). Since the contents of Al and N in austenite in solution vary with the Al+N_??_AlN reaction, the amounts of Alγ and Nγ (concentration of Al and N existing as solutes in austenite, respectively) are calculated from solubility product of AlN in austenite given by the following equation:
log[Alγ]·[Nγ]=-6700/T(K)+1.528
It is revealed that these two elements have potent influence on hardenability, and that the multiplying factor of Al is quite large and is about 1.8 around 400 ppm of Alγ. In high Alγ steels, the γ→α proeutectoid ferrite reaction is retarded through the increase in the incubation period of nucleation and through the decrease in the nucleation rate of ferrite and in the diffusion coefficient of C in austenite.
