Ti含有フェライト系ステンレス鋼の凝固組織に及ぼす酸化物組成の影響
2001 年 87 巻 11 号 p. 707-712
詳細
2001 年 87 巻 11 号 p. 707-712
Effect of oxide composition on the solidification structure of 16mass%Cr-0.15mass%Ti-0.009%N ferritic stainless steel was investigated. As for the results, the oxides in steel ingots was observed to be covered by TiN and contained Al and Mg. When the Mg/Al mass ratio of oxides, determined by EDS analysis, ranged from 0.3 to 0.5, an equiaxed fine-grain structure was produced. According to Al2O3-MgO phase diagram, the oxide composition range corresponds with Spinel phase composition at molten steel temperature. And the disregistry between Spinel and TiN is very low. Therefore, it is presumed that the particles of Spinel accelerate the formation of TiN in molten steel and then an equiaxed fine-grain structure is produced. The mechanism of Spinel dispersion in molten steel is discussed on the information of phase diagram for Al2O3-MgO-TiO2 system and the nucleation theory. It is speculated that the spontaneous nucleation of liquid Al-Mg-Ti oxide occurs due to low interfacial energy with molten steel and then the oxide droplets grow into Spinel.
