Abstract: Based on the similarity principle，RTD curves of different testing schemes were investigated in 20 t three strand T shape tundish by using water model test. By analyzing of the scheme of RTD curves and the mixed model calculation results, the best optimization solution was concluded for the tundish retaining wall. After the flow optimization, mixing evenly time of liquid steel decreased from nearly 250 s to about 100 s, mean residence time increased from 500 s to 1 000 s, package dead volume decreased from nearly 60 % to about 20 %, every flow liquid steel temperature difference decreased from 5.33 ℃ to 1.17 ℃. The large inclusions (more than 50 μm) was not more than 6.5 mg/10 kg in slab, the small diameter inclusion size was less than 6 μm in steel. The production practice shows that the new tundish retaining wall is beneficial to the uniform temperature of molten steel and the probability of collision removal rate of inclusions.

Key words: tundish, water model experiment, molten steel flow field, optimization