Abstract: The formation of volumes of acicular ferrite in high strength low alloy steels is a principal mean to meet high strength and toughness. Several decisive factors affecting the volume fraction of acicular ferrite were reflected in different literatures, and the nucleation mechanism of acicular ferrite and inclusions characteristics conducive to nucleation were summarized by some review, but there was no systematic summary of the effect of variation on apiece factor. In this study, the influence of austenite grain size, cooling rate, inclusion composition, and inclusion size on the volume fraction of acicular ferrite has been summarized. It is concluded that austenite grain size of 100-200 μm, cooling rate of 5-10 ℃/s, inclusion size of 1-2 μm and composition of (Ti、Mg、Zr)O_x are beneficial to promote acicular ferrite nucleation. 

Key words: acicular ferrite, austenite grain size, cooling rate, inclusion composition, inclusion size