The Characterization And Evaluation Of Fluid Flows In The Tundish Of Steel Continuous Casting

The functions of pouring chamber and channel flow zone in tundish is different.In the pouring chamber we hope that the proportion of complete mixing flow is bigger in order to release the turbulent energy and promote the collision and the polymerization of the inclusions.In the channel flow zone we hope that the proportion of piston flow is bigger in order to maximize the flotation removal rate of the inclusions.At present,the analysis model of tundish’s flow characteristics often uses a single combined model,but it can only give the piston flow,complete mixing flow and dead zone of the whole tundish,not the concrete distribution of them.Thus,this study tries to use the segmented characterization to analyze the tundish.This study places conductivity probes in the outlet of the pouring chamber and the tundish to measure the residence time distribution curves(RTD curves).And then this study analyze the flow state characterizations of pouring chamber,channel flow zone and the whole tundish through the RTD curves.The ratio of pouring chamber and channel flow can be changed by changing the location of the weir.And the flow patterns of them can be changed by changing the height of dams and the flow control devices in the flow zone.By doing these,we can optimize the ratio of piston flow and complete mixing flow of the whole tundish.Drift beads are used to mimic the non-metallic inclusions in the experiments and the ratio of pouring chamber and channel flow,complete mixing flow and piston flow is evaluated with the removal ratio.By analyzing the data on the basis of the physical experiments,the following conclusions are obtained:(1)The combined model is composed by the series connection of pouring chamber and channel flow,which pouring chamber and channel flow are both characterized by single model(the series of mixed flow and plug flow which contains dead zone).And this model fits the tundish outlet’s RTD curves best.(2)With two weirs and one dam,both Vm1/Vp1 in pouring chamber and Vp2/Vm2 in channel flow zone vary as the location and height of the weir change.The variations of the two variables follow the same trend.Both the proportion of Vp2/Vm2 in channel flow zone and the inclusion removal ratio increase as the proportion of Vm1/Vp1 in pouring chamber increase.(3)With one weir and one dam,both Vm1/Vp1 in pouring chamber and Vp2/Vm2 in channel flow zone vary as the location and height of the weir change.The variations of the two variables follow the same trend.Both the proportion of Vp2/Vm2 in channel flow zone and the inclusion removal ratio increase as the proportion of Vm1/Vp1 in pouring chamber increase.(4)With one weir and one dam,both Vm1/Vp1 in pouring chamber and Vp2/Vm2 in channel flow zone vary as the location and height of the dam change.The variations of the two variables follow the same trend.Both the proportion of Vp2/Vm2 in channel flow zone and the inclusion removal ratio increase as the proportion of Vm1/Vp1 in pouring chamber increase.(5)There exists no obvious correlation between Vp/Vm in the whole tundish and the inclusion removal ratio.(6)When the flow control device is a weir and a dam,the removal rate of inclusions is the biggest of all.The optimum parameters of the weir and the dam are:290mm between the weir and the center of water entry,310mm in the height of the weir;320mm between the dam and outlet center,225mm in the height of the dam.Compared with the optimal scheme(A1)when the flow control device are two weir and a dam,the removal of 84-101 μm,60-84μm and 50-60μm inclusions increased from 92.03%,77.48%,60.07%to 97.89%,88.64%,70.3%respectively.