含 Ti オキサイド鋼における粒内フェライト変態におよぼす B の効果

概要

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The effect of B on microstructure and toughness at the heat affected zone after welding thermal cycle simulations, has been investigated in steels containing titanium oxide particles. The titanium oxide is identified as Ti_2O_3 with cation vacanies, which contribute to preferential nucleation of MnS and TiN precipitates on Ti_2O_3. The Mn-depleted zone is formed around Ti_2O_3 after the MnS precipitation. The Ti_2O_3 particles with TiN and Mn-depleted zone act as preferential nucleation sites for intra-granular ferrite. The segragation of B at austenite grain boundaries suppresses effectively the nucleation of grain boundary ferrite. While ferrite nucleation at the interface between Ti_2O_3 and austenite matrix, is not affected by B addition because of B-depleted zone arisen from the diffusion of segregated B into Ti_2O_3, via cation vacancies. Consequently the B addition to steels with Ti_2O_3 promotes the formation of fine intragranular ferrite grains so that the heat affected zone toughness is improved even after large heat input welding.
社団法人日本鉄鋼協会の論文
1993-10-01