Assessment of Measured Mixing Time in a Water Model of Eccentric Gas-Stirred Ladles with a Low Gas Flow Rate Part III: Performance in Different Geometric Scale Ratios of the Ladles

Secondary refining is a critical stage that determines steel properties. Its effectiveness is directly governed by the flow and mixing behavior of molten steel. At present, water model experiments are widely employed to investigate flow and mixing behavior during ladle refining. However, the effects of tracer volume and the geometric scale ratio are often neglected. In this study, a 130 t industrial ladle was taken as the prototype, and two water models with geometric scale ratios of 1:5.6 and 1:3 were established. Six tracer volumes were designed to systematically investigate the flow and mixing behavior under different geometric scale ratios. The results show that, with increasing tracer volume, the transport pattern in the small ladle transitions from a top-to-bottom to a center-to-side, whereas in the large ladle, the transport pattern consistently remains top-to-bottom. In both ladles, the mixing time at all monitoring points exhibited a trend of first decreasing and then increasing with increasing tracer volume, although the inflection points differed between the two ladles. For the small ladle, the turning point occurred at Dimensionless tracer amount (Dta) = 0.39 × 10−3, whereas for the large ladle, it occurred at Dta = 0.26 × 10−3. Further analysis indicates that when Dta > 0.51 × 10−3, tracer injection in the small ladle significantly disturbs the original flow field structure. Therefore, the optimal tracer volume for the small ladle is Dta = 0.39 × 10−3. In contrast, the large ladle maintains a relatively stable flow field even at higher tracer volumes. This study clarifies the volume of tracers and the selection of geometric scale ratios. The research results can effectively reduce measurement errors and enhance the reliability of experimental results.