Electromagnetic Soft-contact Characteristics Of Continuous Casting Mould With Different Structure Patterns

The technology of electromagnetic soft-contanct continuous casting (EMCC) can improve the surface quality of the billets through applying high frequency magntic field to control the process of initial stage of solidification. The distribution of magnetic flux density and the characteristic of meniscus are important aspects to estimate the results of EMCC. The structures of EMCC mold are important not only to the effects of the technology of EMCC, but also to its industrialization. It is the foundation for the technology of EMCC industrialization to know the distribution of magnetic flux density, the characteristic of meniscus, and the characteristic of heat transfer in EMCC mold under the condition different structure patterns (billet, round billet and rectangular billet). The electromagnetic soft-contact and heat transfer characteristics continuous casting mould with different structure patterns have been discussed in this thesis.Regarding toΦ178mm industrial round billet EMCC mold, the distribution of magnetic field in the mold under different slit parameters have been discussed through 3 dimension finite element method (3D FEM) numerical simulation method and experimental method. The effect of slit parameters on the distortion of meniscus has been investigated through the experimental method by using low melting point alloy. The results show that the upper flange of industrial EMCC mold has some effect on the distribution of magnetic flux density. When the input power is over 90kW, the shield effect will come out. The magnetic flux density and the height of meniscus will become larger with the slit number; slit width and siit length increasing. When the slit number was changed from 24 to 32, the maximum value of magnetic flux density increased 32%, the height of meniscus increased 110%. When the slit length was changed from 100mm to 130mm, the maximum value of magnetic flux density increased 28%, the height of meniscus increased 155%. When the width of the slit was changed from 0.3mm to 0.5mm, the maximum value of magnetic flux density increased 15%. All these results can give great support to the design ofΦ178mm industrial round billet EMCC mold.Two kinds of asymmetry slit rectangular soft-contact EMCC mold with the same inner size of 213mm×85mm were developed. The distribution of the magnetic flux density and the characteristics of meniscus in the molds have been discussed through experiments. The results show that:the magnetic flux density and the height of meniscus increase with the input power increasing. But the input power did not change the distribution of the magnetic field. The maximum magnetic flux density will move to the same direction as the induction coil. The free surface of the liquid metal should be controlled near the center of the coil.The positions of the slits in EMCC mold are important to the magnetic field and distortion of the liquid metal. It has been found that in the rectangular EMCC mold which has slits at one narrow side, the magnetic field is not zero at the other narrow side where there are no slits when the input power is not zero. At the input power of 52kW, the maximum magnetic flux density on the narrow side which no slits is about 60% of that on the other side with slits. For the improved structure rectangular mold which is added slits at four conners, the magnetic field and the height of the meniscus in the mold are also enhanced. The magnetic field is also uniformed at the same time. It can be proved that using this kind of asymmetry slit structure EMCC mold can apply the technology of EMCC to the rectangular billet continusou casting.A billet soft-contact EMCC mold with the size of 100 mm×100 mm with non-uniformity segment was developed. By using low melting point alloy, experiments had been done. The results show that compared with symmetry slits EMCC mold the magnetic flux density and the height of meniscus are almost the same with the input power increases. The free surface of the low melting point alloy will fluctuate heavily; the temperature of liquid metel will increases, the initial solidification point moves downwards, and the solidification shell become thinner. The joule heat in the mold will increase at the same time. The temperature and the heat flux of the EMCC mold will increase. The mold oscillation also can increase the temperature of the mold and the selections of electric parameters should be adapted with the technical parameters. The resulets can give great support to the EMCC industical experiment.Through the research of electromangneitic soft-contact characteristics of continuous casting mold with different structure patterns, it has been found the structures of the EMCC mold will not change the electromagnetic soft-contact characteristics which are detemined by the relative positon between the coil and the mold, the relative positon between liquid free surface and the mold, and the input power.