低合金 2 相鋼の結晶粒成長

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The grain growth characteristics of dual-phase steels have been investigated using 3%Si-0.3%Cr-0.02∿0.13%C steels which are composed of α- and γ-phases at 900∿1300℃. The grain growth in single-phase region proceeds by grain boundary migration, and the relation between mean radius r^^- and annealing time t is described as follows, (r^^-)^2-(r^^-_0)^2=k_2・t……(1) In the case of dual-phase steels, the grain growth is in need of diffusion of alloying elements, because the chemical composition of α- and γ-phases differs each other. The grains of the minor phase grow slowly in a mode of Ostwald ripening, while the grain boundaries in the major phase migrate under a restriction of pinning by the minor phase grains. It follows as a consequence that the grains of both the phases grow slowly, obeying the following equations, (r^^-)^3-(r^^-_O)^3=k_3・t……(2) (r^^-)^4-(r^^-_O)^4=k_4・t……(3) In the α-rich dual-phase steels, the growth rate is controlled by volume-diffusion in the α-phase, and the growth law is expressed by eq. (2). In the γ-rich dual-phase steels, however, boundary-diffusion is predominant than volume-diffusion in the γ-phase, and the growth law is expressed by eq. (3).
社団法人日本鉄鋼協会の論文
1982-06-01