2000 Volume 86 Issue 5 Pages 323-328
In the production of cast slab for high grade sheet steel, the powder in continuous casting mold is entrained into the molten steel and caused the surface defects in the products. The typical example is the white spot defect for tin plate steel. For preventing the white spot defect, new continuous casting powders are developed. Those powders are consist of CaO-SiO2-Al2O3-MgO-CaF2-AlF3 system and less Na content.
The results of study in laboratory and casting in plant are summarized as follows.
(1) By replacing Na materials with the fluorides of alkali-earth metal, the improved powder can be produced.
(2) When Na in powder is less than 1 mass percent, the occurrence of white spot defect of the tin plate steel produced by high-speed casting is remarkably decreased.
(3) Characteristics of the improved powder are as follows.
(1) The powder is designed of higher viscosity and surface tension.
(2) The crystallization temperature is lower.
(3) The variation in viscosity due to Al2O3 pick up during casting is less.
