V-C-N鋼の初析粒界フェライト成長速度に及ぼすオーステナイト域等温保定処理の効果
1998 年 84 巻 8 号 p. 592-597
詳細
1998 年 84 巻 8 号 p. 592-597
The mechanism of retarded growth rate of intergranular proeutectoid ferrite in a V-C-N steel has been investigated by examining the effect of holding in austenite region during cooling from the solutioning prior to the isothermal transformation at 600°C. The growth rate increases and the transformation start time decreases by increasing the holding temperature, while a C-curve behaviors appears. The growth rate can be ascribed to the supersaturation of C at the transformation interface. THERMO-CALC calculation indicates that substantial precipitation of V(C, N) takes place in the V-C-N steel and the fraction of C in the precipitate decreases with the increasing holding temperature. Analysis of the transformation kinetics in terms of the Johnson-Mehl-Avrami equation shows a two-step process, suggesting decrease in the ferrite nucleation rate by the holding. It is concluded that absorption of C into the precipitate during the incubation period decreases the supersaturation of C at the transformation interface.
