Experimental Research On Flow Field In Slab Continuous Casting Process Using Electromagnetic Swirling Flow

In continuous casting process of steel, occurrence of uneven outlet flow from submerged entry nozzle (SEN) is unavoidable because of lots of reasons, which leads to uneven distribution of the flow field and temperature field and to enlargement of meniscus fluctuation in slab mold and so on, and consequently to decrease of surface and internal quality of ingots, as well as casting speed. Research result shows that the swirling flow in SEN is effective to control the occurrence of the deviation of the bulk flow from the center line in SEN. In the preceding research a new process was proposed, in which a rotating electromagnetic field was set up around a SEN to induce swirling flow of molten steel in it by Lorentz force. And the experimental and simulating works on magnetic field, fluid flow and heat transfer in the nozzle and in the round and the square molds induced by different types of electromagnetic swirling flow generator (EMSFG) were carried out.In this paper, model experiment of slab continuous casting under electromagnetic swirling flow in SEN was conducted with low melting point alloy Pb-Sn-Bi. Firstly, the distribution of magnetic field in the bore of the EMSFG is measured. Then without the existence of mold, the swirling velocity from the outlet of the nozzle is measured for the investigation of the effect of nozzle diameter and length on the swirling velocity. Finally, ultrasonic Doppler velocimetry was used to measure the flow field distribution of molten Pb-Sn-Bi alloy in the slab mold under electromagnetic swirling.The following results are obtained:1. In the bore of the EMSFG:In vertical direction, the magnetic field distribution increases firstly, and then decreases along the height of EMSFG. The value reaches maximum in the center of the EMSFG in height, and the magnetic field is centrosymmetric about the center in height. In horizontal direction, the magnetic field distribution is smallest at the center point and increases from the centre to the edge along the radial direction.2. With the increase of nozzle length, the swirling velocity decreases. With the increase of nozzle diameter, the swirling velocity increases.3. In the case without electromagnetic swirling, the main flow from the outlet of the nozzle impinges the narrow face of the slab mold, and then forms the downward stream and upward stream. The distribution of flow velocity along the wide face at the nozzle outlet is largest in the vicinity of the nozzle, and decreases along the wide face. And there is almost no velocity component in the direction along the narrow face. In the case with electromagnetic swirling, the main flow direction changes corresponding to the swirling direction and impinges the wide face firstly. At1/4of the wide face, the distribution of flow velocity along the narrow face at the nozzle outlet decreases with the increase of the distance from the transducer (wall) and the distribution of flow velocity along the narrow face in the vicinity of meniscus increases with the increase of the distance from the transducer (wall). The direction of velocity along the narrow face at the nozzle outlet is opposite to that in the vicinity of meniscus.