During the tapping of molten steel from ladle to tundish, vortices may develop which take down undesired slag in their core. The driving force of the vortex formation is the tangential flow of the melt in ladle. As increasing the tangential velocity, the vortex formation is promoted. Therefore, it is necessary to suppress the tangential flow in the ladle to control the vortex formation.
To predict the vortex formation height, water model experiments were conducted with three different nozzle diameters (13.7, 28,3 and 56.7mm). Two different inlet modes (tangential inlet and axial inlet) and various waiting times were adopted to make various initial conditions. The vortex formation height was measured by sight with a video camera during the flow discharge of water. The vortex formation height was divided by orifice inner diameter and expressed in dimensionless number.
Drainage experiments with wood metal were made to investigate the effect of traveling or static magnetic field on the vortex formation height. Stainless steel ladle was used the bottom nozzle of which can be replaced with different diameters, 9.8 or 12.3 mm. The vortex formation height was measured by weight measurement method with load cell during the flow discharge of wood metal. The travelling magnetic field was applied with a linear induction motor or a device with 3 rotating permanent magnets and the static magnetic field was applied with a set of permanent magnets or an electromagnet. The dimensionless vortex formation height was decreased from 1.2 down to 0.4 by the application of the travelling magnetic field with both devices. The magnetic field around the set of permanent magnets and the electromagnet were calculated by ANSYS and compared with the each experimental result. There were good agreements between experiments and calculations. Drainage experiments with wood metal using the electromagnet were also conducted. The dimensionless vortex formation height decreases from 1.7 down to 0.85 in both cases of the permanent magnet device and the electromagnet device as the static magnetic field increases up to 0.17 Tesla.
The effects of a nozzle eccentricity and static magnetic field on the vortex formation were calculated with a commercial FDM package, CFX-F3D. Flow field and free surface shape during the drainage of melt were calculated numerically. The results showed the vortex could be suppressed by increasing the nozzle eccentricity or by the application of the static magnetic field. This calculation method can be applied to the industrial size ladle in steel making process to design a proper magnet size and to estimate its effects.
Measurement of flow velocities in liquid metal systems is very important in the design and control of high temperature processes. A novel method of a non-contacting measurement of the melt velocity in ladle was developed on the basis of the electromagnetic principles. Three sensors were designed to measure the velocity of the melt without direct contact. One consists of two permanent magnets (PMVS: Permanent Magnets Velocity Sensor) and a magnetic probe, another (EMVS: Electromagnetic Velocity Sensor) consists of an electromagnet and a magnetic probe, and the third (RPMVS: Ring Permanent Magnet Velocity Senor) consists of a ring-shaped permanent magnet and a magnetic probe. These velocity sensors were tested first with a solid aluminum cylinder and then a wood metal melt. Because the magnetic probe and the permanent magnet have a temperature dependency, the permanent magnet as well as the probe must be kept at a constant temperature by a cooling system. The magnetic flux densities obtained by the EMVS and RPMVS were proportional to the rotating speed of the aluminum cylinder up to 1.5 m/sec and the stirring speed of the wood metal melt up to 0.8 m/sec. The calculated magnetic flux density near the velocity sensor was in a good agreement with the measured one. The distribution of the magnetic field of the EMVS was more effective to obtain a larger signal than the RPMVS. The magnetic field measured by the sensor was also calculated with the calculated magnetic field of the magnets and the velocity field with some assumption. The effects of design factors such as inner radius, length, width of a coil or a ring permanent magnet were investigated by this calculation.
