制御圧延鋼における変態集合組織の形成

抄録

The formation of the transformation textures has been studied in low C-Mn-Nb-V and low C-Mn-Mo-Nb steels which were subjected to deformation in unrecrystallized austenite region. Using the method of crystallite orientation distribution function analysis, textures were quantitatively determined in as-rolled and as-quenched steels with polygonal ferrite-pearlite or acicular ferrite or martensite which were produced by an experimentally controlled rolling process. Transformation textures develop markedly by deforming austenite phase in unrecrystallized austenite region. The textures consist of two preferred orientations; {113} <110> and {332} <113>. The density of these orientations, especially {332} <113> in both acicular ferrite and martensite steels are greater than that in polygonal ferrite-pearlite steel. The orientation density of {332} <113> in both steels increases with decreasing prior austenitic grain size. Crystallite orientation distributions after transformation of austenite having (110) [112], (641) [112], (321) [214], and (211) [111] were calculated for polygonal ferrite-pearlite and martensite steels. It was as sumed that the austenite to polygonal ferrite transformation followed the Kurdjumov-Sachs lattice orientation relationship and that all the variants were operative during the transformation. While, in the case of the austenite to martensite transformation, such variants were assumed to operate that corresponded to the slip systems with the largest resolved shear stress in the slip deformation of anstenite phase. These calculated crystallite orientation distributions are in good agreement with observed results. The formation of the transformation texture of acicular ferrite steel seems to be similar to that of martensite steel.