Abstract
The effects of precipitates formed by the addition of vanadium, nitrogen, and aluminium on the ferrite grain size of 0·15% C steels have been studied by cooling suitable steels at four rates ranging from 120 to 3·6 K min−l from temperatures giving a constant austenite grain size of 35 μm. The undissolved particles present during austenitising have no role in determining the ferrite grain size. The precipitating particles of vanadium carbide (VC) and particularly vanadium carbonitride (V(C,N)) are excellent ferrite grain size refiners, while aluminium nitride (AlN) has little or no effect on ferrite grain size refinement. The presence of aluminium enhances the ferrite grain size refining effect of V(C,N). The volume fraction of precipitates and their size or distribution are responsible for ferrite grain size refinement.
MST/773
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