焼ならし型高張力鋼のフェライト細粒化におよぼす窒素, バナジウムの効果

概要

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The effect of grain refinement of steel is well known as a metallurgical method to make both strength and toughness improve. In this study, in order to use VN precipitates for α-grain refinement in normalized steel, the effect of V and N content on γ-grain size at reheating stage and α-grain size after air cooling and the mechanism of grain refinement have been investigated. The results obtained are as follows, 1) The α-grain refinement in high N-V added steel is due to the degree of γ-grain refinement by VN precipitates and high γ/α transformation ratio. 2) The more the VN precipitates in γ-grain, the finer the α-grain becomes. Its effect becomes distinguished in the range of 30∿50ppm N as VN and is saturated with 100ppm N as VN. 3) High γ/α transformation ratio is due to the increase of α nucleation site at γ-grain boundary. It is considered that the contribution of VN is not in lowering of transformation temperature and increasing of transformation time, but in playing role as a α-nucleation site or suppressing of α grain growth through precipitation in front of α phase.
社団法人日本鉄鋼協会の論文
1990-08-01