鋼中の硫化物の形態および分布におよぼす硫黄含有量と凝固条件の影響について

抄録

The morphology and distribution of sulfide in steel ingot have a close connection with chemical composition of steel and solidification variables. Using steels containing 0.004, 0.01, 0.05, 0.10, and 0.63%S, the authors have investigated the effects of sulfur content and solidification variables on the morphology and distribution of sulfide.
The results obtained are summarized as follows: 1) Morphologies of sulfides are dependent on sulfur content. In the range of sulfur content up to 0.01%, type I sulfide is found and with more than 0.05% sulfur, type II sulfide is observed. The higher the sulfur content, the larger the area of type II sulfide.
2) Large dendritic sulfide (type D) as a primary phase is observed in the specimens containing 0.63% S and 2.88% Mn, and its size is dependent on the cooling rate.
3) From the observation of three dimensional morphology of sulfide using a scanning electron micro scope, it is found that type II sulfide is dendritic and type II and Type D sulfides are occasionally inter connected.
4) The size arid spacing are expressed as a function of the cooling rate, Vin°C /min.
i) Average size of type I sulfide, d in μm; d=13.9 V^-0.30ii) Average spacing of rod-like (type II) sulfide, λ in μm; λ=10.7 V^-0.30iii) Average size of rod-like (type II) sulfide, d′ in μm; d′=2.9 V^-0.22 The average size of rod-like (type II) sulfide is smaller than that of type I at the same cooling rate.
5) Type I and type II sulfides are located in interdendritic spaces, on the other hand, type D sulfides are distributed randomly.