Slab subsurface defects caused by mold powder entrapment tend to occur at high speed castig. Behavior of molten steel flow in continuous casting mold of steel slab was investigated with water model experiments and casting tests at actual continuous caster.
The results obtained are as follows:
(1) the level fluctuation of molten steel in a mold has various frequency waves and long period waves (0.1 to 0.2 Hz) are related to surface velocity of molten steel.
(2) water model experiments reveal that the level fluctuation of molten steel is able to be controlled by the optimization of submerged nozzle desigh and other casting parameters.
(3) a parameter expressing the level fluctuation of molten steel near the narrow side mold (F value), which was derived from various casting conditions, was found and a method to select casting parameters optimizing the range of the F value was devised.
These findings have been contributing to the clean steel production at a high speed casting in Fukuyama No.5 continuous casting machine.
