Hoyoung Kim

Effects of High Frequency Electromagnetic Field on Improving Macro/Micro Structure and Reducing Segregation for Aluminium Alloy Billets

By imposing a high frequency magnetic field, the surface quality and macro/micro structure of the direct chill cast billets are improved. The casting speed can also be improved by simultaneous applying mold and electromagnetic coil, especially for the alloys with a wide freezing range such as Al-Cu-Mg alloy. The extent of macrosegregation in the Al-Cu-Mg alloy is reduced by application of the magnetic field. Moreover, the inverse segregation layer usually observed in the direct chill cast billet is eliminated by the effect of the electromagnetic field. The microstructure of the hot-rolled and heat treated billets cast under the high frequency field also show better characteristics.

Solidification characteristics of continuously cast aluminum alloy by imposing the higher frequency electromagnetic field

In order to increase the casting speed of semi-continuous casting of aluminum billet, a mold with slits and external cooling water channels was designed. This cooling system can supply enough cooling strength and keep the cooling rate readily. By imposing a high frequency magnetic field, the surface quality and microstructure of the billets are improved, especially at a higher casting speed. The magnetic field has ideal profile inside the mold via the slits, which results in an easier controlling of meniscus level during the casting process and supports a possibility of higher casting speed with the effect of the external cooling water. Besides bringing the good surface quality, uniform structure, and fine grain, the casting defects such as segregation and porosity etc. also could be reduced or eliminated by imposing an electromagnetic field.

Numerical simulation of solidification process in the electromagnetic casting of aluminum and testing against a pilot-scale caster

A three dimensional model for simulating the semi-continuous solidification process accompanying mass-transfer in electromagnetic casting (EMC) of aluminum alloys was described in this paper. The electromagnetic skin-effect and the Joule heating were incorporated into the computation equation by a proposed formula. Numerical and experimental results describing the solidification process of an aluminum ingot cast on a pilot-scale caster were presented in order to show the efficiency of the model. And the effects of casting speed and pouring temperature on the solidification front were also analyzed.