| As a connection of the converter process and continuous-casting process, ladle teeming system of the molten steel from the ladle to the tundish is extremely important in steelmaking. In order to improve the productivity, energy efficiency and environmental protection and to produce cleaner and high-quality steel, a new ladle teeming method (electromagnetic steel-teeming method) using electromagnetic induction heating in slide-gate was proposed. The basic idea of this new process is to melt part of or the whole of the new ladle well-packing materials (i.e. Fe-C alloy with similar composition of the molten steel), which substitute the traditional nozzle sand, and achieve smoothly molten steel-teeming.Electromagnetic steel-teeming method is regarded as an efficient way to reduce the inclusions in the molten steel and achieve100%automatic steel teeming. This new technology is one of the electromagnetic metallurgy methods and it shows great promise. The application of electromagnetic steel-teeming system can (1) significantly improve the clean degree of the molten steel;(2) significantly improve the ladle automatically open casting rate;(3) reduce blocking of the immersion nozzle, increase the continuous casting numbers;(4) avoid the environment pollution for using the nozzle sand and (5) avoid outsourcing nozzle sand and decrease costs.Whether the electromagnetic steel-teeming system can be successfully applied in industrial production depends not only on the melting of part of or the whole of the Fe-C alloy, but also on the safety of the ladle shell under the induction heating condition. The purpose of this research is to investigate the feasibility of the electromagnetic steel-teeming system, to find better coil structural parameters and electrical parameters and to develop a suitable electromagentic steel-teeming system, which could be used in the inductrial steelmaking process. In order to verify whether the electromagnetic steel-teeming system can meet the requirements of the ladle steel-teeming, the mixture of Fe particles and graphite powder was used to replace the traditional nozzle sand in the upper nozzle. Using ANSYS finite element analysis software, the temperature distribution of the upper nozzle in the bottom of the ladle is analyzed in steady and transient state, to examine the effects of the induction heating. It was found that a steady gradient temperature was formed in the upper nozzle. The Fe particles could be melted under the induction heating condition, which indicates that the electromagnetic steel-teeming is feasible. Furthermore, experimental method was employed to verify that the Fe-C alloy was suitable to be the substitutable material of the traditional nozzle sand.Electromagnetic steel-teeming hot-condition experimental facility was designed and produced. Base on the facility, the numerical simulation method was employed to investigate the effects of the induction parameters such as current intensity, frequency and diameter of the coil on teeming time, which was tested by calculating the surface temperature of the blocker which located in the bottom of the upper nozzle in the hot-condition experiment. The results showed that the teeming time was decreased with the increases of current intensity and frequency, and with the decrease of coil diameter. The suggested parameters were found under the conditions of this research. The sintering mechanism and sintering conditions were discussed with the Fe-C alloy replaced the traditional nozzle sand in the upper nozzle. It was confirmed that the Fe-C alloy in the upper nozzle could form five layers as following:liquid layer, solidified layer, liquid-sintering layer, solid-sintering layer and original layer. The solidified, liquid-sintering and solid-sintering layers could prevent the molten steel stream from corroding the sliding plate. The position of the liquid/solid interface and its morphology were investigated by means of the hot-condition experiment. It was shown that the position of the interface was decreased with the decrease of Fe-C alloy melting point, that is, the position of the liquid/solid interface could be adjusted by changing the melting point of the Fe-C alloy. Furthermore, the effects of Fe-C alloy with different composition on teeming time were investigated. The opening time of the sliding plate in the electromagnetic steel-teeming process was found according to online detecting the temperature on the external surface of the upper nozzle.The model of the electromagnetic steel-teeming system used in the industry was established by ANSYS finite element analysis software. Numerical simulation method based on the integration of both electromagnetic and thermal analysis modules of ANSYS was employed to investigate the surface temperature of the sintered Fe-C alloy which was used to prevent the molten steel from destroying the sliding plate. In addition, the effects of the coil structure parameters (such as distance of the molten steel and the coil, length and diameter of the coil) and electric current parameters (such as ampere turns, frequency) on teeming time were investigated. The optimal parameters were found according to the simulation, and the smoothly steel-teeming using induction heating was achieved in the optimal parameters’condition. How the ladle refractory met the technological requirements in the electromagnetic steel teeming process was also discussed. Additionally, the effects of molten steel temperature and melting point of Fe-C alloy on teeming time were studied. The safety of the steel shell under the action of electromagnetic induction heating with the optimal parameters was checked via the distribution of temperature field on the shell.On the basis of above mentioned investigation, the electromagnetic steel-teeming system which could be used in the industry was preliminarily designed. We proposed two kinds of restructuring proposals to meet the requirements of the use of electromagnetic steel-teeming system in the ladle bottom. The advantages and disadvantages of the two proposals were discussed. The selected principle and methods of power and structure of the coil in the electromagnetic steel-teeming system were discussed as well. Additionally, the concept of electromagnetic-function integration was proposed. On the basis of the above analysis, we discussed the particular problems that should be took into account in the industrial experiments. |
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