调幅高频电磁场下的无弯月面电磁连铸技术基础研究

The meniscus-free electromagnetic continuous casting (EMCC) with amplitude-modulated magnetic field (AM-MF) has been proposed. Its main principle is to apply the AM-MF with its varied force on the triple point of molten metal-mold-hot top in the continuous casting, so that several technique problems may be overcame. The AM-MF's characterization is to cause vibration, sometimes even ultrasonic wave in the steel billets and molten-steel. Just like the mold oscillation, this kind of vibration may be advantaged to take off the billets from the mold and then reduce the withdraw resistance. Repulsion force towards inner molten steel due to AM-MF reduce the friction force between the billets and mold, so the possibility of breakout and crack formation is reduced, and solidification of the triple point is improved. The induction heat of magnetic field can improve the solidification of the triple point too, which is benefit to the billets surface quality.7 papers were published during the study work, in them 4 were recorded by SCI, EI and ISTP. Intensive and systemic study have done on AM-MF generator equipment design, the influence of magnetic field on the dynamic pressure in the mold flux channel at different moment in the mold oscillation cycle, the distribution of electromagnetic force in cylinder shape liquid metal under continuous and amplitude modulated alternating magnetic field, the withdraw resistance and the temperature fluctuation of early solidification point during continuous casting. So far, the main progress and results in this study are:.(1).The conception of amplitude-modulated magnetic field has been proposed first time based on the intermittent magnetic field. A circuit to modulate the amplitude of magnetic field in high frequency magnetic field generator has been invented, then an equipment can produce 9 kinds AM-MF was realized. Measurement results show that amplitude modulated characterized magnetic field can be got in the induct coil by the equipment, which is meaningful for developing of EMCC..(2).The dynamic pressure in the mold flux channel at different stage in the mold oscillation cycle is calculated under EMCC. The result shows that electromagnetic force widening the exit width of mold flux channel is a key factor of why the technology improves the surface quality of billets..(3).The distribution of electromagnetic force along with radius in cylinder shape liquid metal under continuous and amplitude modulated alternating magnetic field are deduced and calculated by series method. The calculation gave a reference to design the best type of amplitude-modulated magnetic field in EMCC.(4).As a beginning point, the mechanism problem of how electromagnetic field improve the surface quality in EMCC leaded the systemic measurements of the temperature fluctuation of the meniscus in continuous casting by model experiments. Based on the results, a new mechanism about the formation of the oscillation mark was proposed that the "temperature fluctuation" of meniscus is a key factor for the surface defect formation of continuous casting billets.(5).Friction force in continuous casting mould was measured by newly designed strain-gauged cantilever. It showed that friction force increase with increasing cast speed, and mold flux can decrease friction force obviously. The measurement device has obvious response to stick type breakout during continuous casting, so it can be developed to a potential breakout prediction technology. The study provided foundation for systemic measurements of friction force in continuous casting and analysis magnetic field influence on EMCC..

无弯月面电磁连铸技术是生产无缺陷铸坯的新技术，将在高速连铸和连铸连轧中发挥重要作用，本课题提出采用调幅高频电磁场减少铸坯与结晶器壁摩擦和控制凝固的方法，研究此种电磁场特性和在铸坯中的激振效应，考察三重点凝固过程和铸坯与结晶器壁的摩擦行为，掌握电磁参数、结晶器结构和连铸工艺参数与连铸坯质量的关系，为该技术的应用奠定基础。