0.8%C鋼の炭化物の球状化におよぼすクロム, モリブデンおよびバナジウムの影響

抄録

Effect of Cr, Mo or V on spheroidization of carbides in 0.8%C steel by slow cooling annealing has been investigated.
An addition of Cr remarkably accelerates spheroidization of carbides, while additions of Mo and V do a little. X-ray and analysis of carbides has indicated that M₃C and M₇C₃ are only carbides observed throughout the annealing process in 2% and 5%Cr steels, respectively. In Mo and V steels, however, carbides formed by eutectoid reaction proved to differ from those surviving in austenite on annealing, that is M₂₃C₆ and M₃C are eutectoid carbides in Mo and V steels respectively, while Mo₂C and VC survive in austenite in Mo and V steels respectively. Although the addition of any of these elements results in increasing amounts of undissolved carbides in austenite, the fact that Cr has a marked effect on spheroidization of carbides strongly suggests that an undissolved particle of carbides in austenite in Cr steels should act as a center for the precipitation of eutectoid carbides since undissolved carbides are identical with eutectoid carbides. Thus it is concluded that identity of carbide precipitating during eutectoid reaction with that surviving in austenite will be of a primary importance in spheroidization of eutectoid carbides by slow cooling annealing.