Of Liquid Metal In The Casting Process Of The Electromagnetic Control

With the development of electromagnetic processing of materials, the applied range and paths of electromagnetic field has been expanding in the last ten years. A new technology, that can manufacture clad metal materials with electromagnetic brake, was put forward; In order to analyze the feasibility and choose reasonable technological parameters, the effects of electromagnetic field on molten metal flow in the mould are discussed by use of self-programming software SIMPLE. Another new technology, the nozzle electromagnetic stirring (N-EMS), was brought forward; the effects of electromagnetic stirring on flow field and temperature field in the nozzle are studied using analytic software ANSYS; the experiments of continuous casting were performed with Sn-3. 5%Pb alloy.Based on MHD theory, mathematical model of fluid flow in the mould installed electromagnetic field was established; SIMPLE code for computing fluid field was programmed using Visual C++6.0 software, adopting interleaving mesh and iterative routine of line-by-line with block amendment; the effects of level magnetic field (LMF) on metal fluid flow were researched. The results show that by imposing LMF, discharge velocity from the nozzle is suppressed, jet length is decreased, back flow zone in the center of the mould is reduced; that control effectiveness is obvious when magnetic flux density is more than 0. 2T; that it is necessary to set dam board of about 20mm-30mm high in the upper port of the mould in order to avoid lateral flow of liquid-level due to applying EMBR; homogeneous velocity distribution results in uniform temperature distribution; when the casting speed is faster, the effectiveness of EMBR is better, so EMBR is suitable for quick-speed continuous casting.The cast metals that have different performance on two sides can cast continuously by pouring two molten metals, of different chemical composition, because electromagnetic force can suppress the mixing of molten metals in the molten pool.Solidification structure of continuous casting billets is improved obviously by N-EMS. The experimental results show that after applying N-EMS, crystal grains are finer, zone of equiaxial crystals enlarges, zone of dendrite crystals reduces correspondingly; continuous casting can be conducted at the lower pouring temperature and the nozzle can' tbe jammed with N-EMS.To discuss the mechanism of grain refining by N-EMS, flow field and temperature field in the nozzle are computed with the software ANSYS. The results are as following: axial velocity distribution is almost the same with or without N-EMS, and circumferential velocity distribution has remarkable difference, in other words, after applying N-EMS, the electromagnetic force makes the molten metal in the nozzle swirling; under the same condition of pouring temperature, temperature distribution of molten metal in the nozzle is more uniform with N-EMS. The mechanism of improving solidification structure of billets is that electromagnetic force changes the flow of molten metal in the nozzle, and molten metal in the mould is stirred by rotation motion of metal flow; that temperature distribution in the nozzle is uniform, and cold pouring is implemented for lower pouring temperature.