低合金鋼における凝固・冷却中のオーステナイト粒成長に及ぼす合金元素と冷却速度の影響

概要

論文の詳細を見る
Effects of alloying elements and cooling rate on γ grain growth behavior in the solidification and subsequent cooling processes of low alloy steels have been studied in relation to surface cracking of continuously east (CC) slabs. Grain growth of γ phase occurs rapidly below a completion temperature of transformation into γ phase (T_γ), since strong pinning effect of the second phase such as δ-ferrite and/or liquid phase on γ grain boundary migration disappears. Thus γ grain size of as-cast steels can mainly be determined by T_γ, i.e., the maximum grain size is obtained at a peritectic composition, as expected from Fe-C phase diagram. The carbon concentration at the peritectic point is significantly shifted by the addition of alloying elements. The coefficient K_x on the shifting was determined separately for Mn, Ni, Si, Cr and S. Using the K_x for element X, carbon equivalent (C_p) for perifectic reaction of low alloy steels can be written additively as C_p=C+Σ__iK_<xi>・X_i In the same composition, the γ grains are largely refined by increasing the cooling rate because of the effects of decrease in T_γ and of the suppress of γ grain boundary migration below T_γ.
1987-10-01