Electromagnetic inspection of a two-phase GaInSn/Argon flow

Adequate control of steel flow through the submerged entry nozzle during continuous casting is essential for maintaining steel cleanliness and ensuring good surface quality in downstream processing. Monitoring the flow in the nozzle presents a challenge for the instrumentation system because of the high temperature environment and the limited access to the nozzle in between the tundish and the mould. We study the distribution of two-phase liquid metal/gas flows by using a laboratory model of an industrial steel caster and an inductive sensor array. The experiments were performed with GaInSn as an analogue for liquid steel, which has similar conductive properties as molten steel and allows the measurements at the room temperature. A scaled (approx. 10:1) experimental rig consisting of a tundish, stopper rod, nozzle and mould was used. Argon gas was injected through the centre of the stopper rod and the behavior of two phase GaInSn/Argon flows was studied. The electromagnetic system used in our experiments to monitor the behavior of two phase GaInSn/Argon flows consisted of an array of 8 equally spaced inductive coils arranged around the object, a data acquisition system and a host computer. The present system operates at 10 kHz and has a capture rate of 10 frames per second. The results showed clearly that the injection of the Argon gas was distinguishable from the continuous flow by observing the appearance of oscillation patterns in the raw signals. These oscillations become more dominant with the increase of the Argon flow. In some cases two main oscillation patterns were present in the raw signals and our results suggested that those patterns are highly correlated with the level height in the mould and with the pressure in the nozzle.