低合金鋼の過熱脆化と硫黄の挙動の関係

抄録

The Gleeble tensile test, Auger electron spectroscopy and electron microscopy techniques were used to investigate the relationship between the over-heating embrittlement (the loss in ductility on cooling below 1300°C) and the behavior of sulphur at grain boundaries in 0.55%C-1%Ni-3%Cr steel.
The Fe-side sectional diagram of this steel bearing sulphur was obtained by means of a metallographic examination, and it shows that sulphide particles are melted as droplets at about 1100°C and dissolved in γ-Fe at about 1300°C. The number and size of sulphide particles at grain boundaries were measured, and it was found that the short time interruption of cooling at about 1100°C during cooling from 1300 to 900°C introduced the fine dispersion of grain boundary sulphide. The fine dispersion of grain boundary sulphide is certainly one of the most important factors affecting the over-heating embrittlement, and also supersaturated sulphur or its grain boundary adsorption may be concerned.