PRECIPITATION OF NbC IN FERRITE AND ITS EFFECT ON PRECIPITATION-STRENGTHENING OF MICROALLOY STEELS
YONG Qilong; ZHENG Lu (Central Iron and Steer Research Institute; Ministry of MetaZlurgical Industry; Beijing) (Manuscript received 20 September; 1982; revised manuscript 4 June; 1983)
Cite this article:
YONG Qilong; ZHENG Lu (Central Iron and Steer Research Institute; Ministry of MetaZlurgical Industry; Beijing) (Manuscript received 20 September; 1982; revised manuscript 4 June; 1983). PRECIPITATION OF NbC IN FERRITE AND ITS EFFECT ON PRECIPITATION-STRENGTHENING OF MICROALLOY STEELS. Acta Metall Sin, 1984, 20(1): 9-16.
Abstract The precipitation of NbC in ferrite and its effect on the precipitation-strengthening of the microalloy steels containing 3 different percentages of Nb, i.e. 0.24, 0.15 and 0.08%, have been studied. The critical NbC nucleus size, the rate of homogeneous nucleation, the temperature of the maximum rate of homogeneous nucleation and the time for complete precipitation were estimated in agreement between the calculated and experimental results. The precipitation-strengtheningseems to have optimum effect on the steels by isothermal precipitation for 1 h at about 600℃. Moreover, an improvement of the formula for the yield strength increment by the platelike NbC precipitates was also made. It is shown that, even the size of NbC precipitates down to 2.6nm, the mechanism of the precipitation-strengthening is still that of the Orowan's.