Abstract
A mathematic model considering the bubble coalescence and breakup using the Euler-Lagrange approach has been developed to study the effect of the initial bubble size on the distribution of bubbles captured by the solidification shell. A hard sphere model was applied for dealing with the bubble collision. Advanced bubble coalescence and breakup models suitable for the continuous casting system and an advanced bubble captured criteria have been identified established with the help of user-defined functions of FLUENT. The predictions of bubble behavior and captured bubble distribution agree with the water model and plant measurements well respectively. The results show that the number of small bubbles captured by solidification shell is much higher than that of large bubbles. What is more, the number of captured bubbles at the sidewalls decreases with the distance from the meniscus. For the case of large gas flow rate (gas flow fraction of 8.2%), the initial size of bubbles has little effect on bubble captured distribution under various casting speeds. When the gas flow rate is small (gas flow fraction of 4.1%), the number density of captured bubbles increases as the initial bubble size increases, and the effect of initial bubbles size on captured bubble number density is amplified when the casting speed decreases. The average captured bubble diameter is about 0.12–0.14 mm. Additionally, for all cases, the initial bubble size hardly affects the average size of captured bubbles.
Highlights
The bubbles captured by the solidifying steel shell during the continuous casting process are the main cause of defects of blisters and slivers in the slab
The Euler-Lagrange model was used to simulate the bubble transport in the continuous casting mold and bubble captured by the solidification shell
The bubble coalescence and breakup were considered in the model, and an advanced bubble captured model was established
Summary
The bubbles captured by the solidifying steel shell during the continuous casting process are the main cause of defects of blisters and slivers in the slab. Argon gas is usually injected from the submerged entry nozzle (SEN) to withstand nozzle clogging [1,2]. The transport of argon bubbles has a great effect on the product quality. The bubbles escaping at the slag layer, while not casting the slag entrapment, are helpful for removing the inclusions by attaching them to the slag, which is good for the slab quality. Argon gas is injected through the porous refractory at the upper part of the SEN wall. The initial size of argon bubble is affected by the refractory properties, gas flow rate and fluid velocity [4]
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