Simulation of flow, solidification and strip forming during the production of broad strip using the two-roll casting process
Flow, macroscopic solidification and strip forming were investigated for strip casting by physical and numerical simulation. Laser-optical flow measurement techniques (DPIV, LDA) were applied to the physical water model of the melt pool. Here the basic flow and turbulence structures were determined. The validated CFD simulation of the water flow was used to simulate the flow and macroscopic solidification of the steel melt on the casting rollers. The main influence on the flow field in the melt pool is exerted by the immersion tube concept. The free jets entering the pool generate areas of high fluid velocities and high turbulence. Due to mixing, this leads to low subcooling of the steel melt and causes slower strip shell growth. In calm areas, the strip shell grows faster. This leads to an uneven surface temperature of the cast strip. Here a fundamental agreement is found between the results of the CFD simulation and the measurement of the surface temperature. The increase of the pool height leads to an even solidification on the casting rolls in spite of the increased mass flow, independent of the immersion tube concept. The influence of the flow decreases.
The CFD simulation of the transient pool flow was carried out for both water and steel melt with consideration of solidification. The shape of the free surface is reproduced by numerical simulation. While a stationary flow field is found in the simulation of the water flow, cyclical fluctuations are found in the simulation of the steel melt.
The understanding of the relationships between flow and solidification and the effect on strip formation was considerably extended.
The project was funded by the Deutsche Forschungsgemeinschaft (DFG) under the reference number PF 394/3-1.