Numerical Simulation of Coupled Electromagnetic Field, Flow and Heat Transfer in Bloom Continuous Casting with Electromagnetic Stirring
|Course||Iron and steel metallurgy|
|Keywords||Bloom continuous casting Mold electromagnetic stirring Electromagnetic Fields Flow field Temperature field Numerical Simulation|
Continuous casting mold electromagnetic stirring is becoming the the control slab solidification process to improve the solidification structure, improve slab quality of an effective means. Therefore, the continuous casting process, to carry out the process under mold electromagnetic stirring has a very important significance. In this paper, a factory bloom continuous casting mold electromagnetic stirring as the research object, using a numerical simulation method, establish the mathematical model for the description of the electromagnetic field, the flow field and temperature field distribution, and, respectively, using the finite element, finite volume method. The obtained mold electromagnetic stirring slab magnetic field, the flow field and temperature field distribution of the exciting current intensity, frequency, and casting speed impact. The study showed that: (1) the strength of the magnetic induction slab in the agitator center to the ends is gradually reduced, while in the horizontal cross-sectional view of the inner, relatively uniform magnetic field distribution. The electromagnetic force was circumferential distribution, and cut to the electromagnetic force and to the center proportional to the distance on the horizontal sectional view of slab. Along the casting direction tangential electromagnetic force is largest, and the agitator center in the crystallizer under the mouth there is one peak. Magnetic induction and electromagnetic force is increased with increasing excitation current intensity, the frequency of 4.0Hz, the excitation current for each additional 100A, the magnetic induction intensity of the stirrer center about 7.5mT, and the maximum tangential electromagnetic force by 200A 325N/m3, increased to 600A of 2890N/m3. Magnetic induction intensity decreases as the frequency increases, the mold, and the electromagnetic force first increases and then decreases, and the maximum when 8.0Hz. (2) not added during electromagnetic stirring, molten steel discharged from the immersion nozzle, down to invade the depths of the crater, and then along the side of the solidification surface upwardly reflux, to form a single circulation. Plus electromagnetic stirring, molten steel discharged from the immersion nozzle by a vertically downward shift in the effective area of ??the electromagnetic stirring to horizontal rotation, forming the mainstream area of ??the rotational flow; mainstream area above the molten steel is formed from the center down by the solidification surface lateral circulation; contrast to this, in the mainstream area below the downward and upward from the center of the circulation of the molten steel formed by the solidification surface side. Stirring parameters 400A, 4.0Hz maximum tangential velocity reaches 0.28m / s, the excitation current intensity for each additional 100A, the tangential velocity is increased from about 0.073m / s. The greater the electromagnetic force, the greater the stirring intensity, more shallow steel jetted intrusion and secondary flow phenomenon is more prominent. (3) when the electromagnetic stirring, overheating of molten steel discharged from the immersion nozzle, downward flow, superheat slowly disappear on a slab section, the core portion of high temperature, while the decreased sharply to one side of the solidification surface, the temperature distribution into a hump-shaped. After electromagnetic stirring, rotational stirring resulting in the direction of flow of the molten steel becomes horizontal by vertical downward rotation, blocking the outflow of superheat of molten steel from the immersion nozzle to invasion depth shallower, so that the axial temperature decreased rapidly, while the diameter to the temperature rise, resulting in the temperature gradient increases, the solidification surface forefront conducive to heat transfer. Stirring intensity is greater, the higher the position of the hot zone. (4) is derived by numerical simulation of the electromagnetic stirring parameter range of 400-700A ,4.0-8 .0 Hz, field trials show that the optimized parameters 600A, 4.0Hz. The maximum tangential electromagnetic force 2890N/m3 maximum tangential speed of 0.45m / s, the top surface of the maximum shear speed of 0.051m / s, and the phenomenon of secondary flow of the molten steel projecting the position of the hot zone has been improved.