A water model with linear scale 1 ; 3. 27 for a 70 t ladle RH unit has been established by using flow rale methed to measure RH circulation rate. RH circulation rate of liquid steel in real process condition and effect of parameters such as blow rate in up-gas tube
inner diameter of orifice T blowing up-gas traveling path and dipping depth of leg on RH circulation rate were analyzed to get optimizing process parameters. The commercial test of a 70 t ladle RH degassing refining showed that with blow rate 1 200 L/min in up-gas tube and inner diameter 3 mm of orifice
average [0
]
of bearing steel decreased by 3 X 10
-6
as compared that with original process ; carbon content of extra-low carbon steel might decrease to less than 0. 002% and decarburization time obviously decreased as compared with that before optimization.