Abstract
Scale defects, called "red-scale", frequently form in Si-added hot-rolled steel sheets because of poor hydraulic-descaling-ability in hot-rolling process. In this work, effect of P on the hydraulic-descaling-ability in Si-added hot-rolled steel sheets and the mechanism of descaling are investigated by red-scale reproduction test and the analysis of Fe-Si-P oxide.
(1) Addition of P to Si-added steel improves the hydraulic-descaling-ability.
(2) Because the addition of P lowers binary eutectic temperature of FeO/Fe2SiO4 oxides formed during slab soaking. Therefore the liquid eutectic compound in the scale/steel interface during the descaling improves the hydraulic-descaling-ability.
(3) Furthermore high slab soaking temperature in addition to increase of P is more effective to improve the hydraulic-descaling-ability because of high descaling temperature.
(4) The Fe-Si-P scales were synthesized from mixtures of the reagents of Fe, Fe3O4, SiO2 and P2O5. Decrease in the binary eutectic temperature of FeO/Fe2SiO4 with P2O5 is clarified by thermal analysis of them.
