【作者】 王辉；

【导师】 金俊泽；

【作者基本信息】 大连理工大学 ， 材料加工工程， 2004， 博士

【摘要】 电磁铸造技术是建立在电磁流体力学基础上,并与冶金工程相结合的先进材料加工方法。由于生产的铸锭具有表面光亮、缺陷少、组织致密、机械性能好等优点,电磁铸造技术已成为铝合金生产的主要方法。随着铝合金电磁铸造技术的日益完善,以及电磁铸造生产的铸锭的优越性,钢、铜及镁合金都已成为电磁铸造实验与研究的对象。电磁铸造的关键技术在于金属熔体在电磁场作用下的无接触立柱成型。由于不同金属具有不同的物性参数,因而电磁成型可行性及难易程度各不相同。本文以获得不同金属电磁铸造成型实验参数为着眼点,采用数值计算、数学分析以及实验研究相结合的方法对不同金属的电磁铸造成型可行性及难易程度进行了研究。论文主要包括以下内容:从电磁铸造基本原理出发,建立了圆锭电磁铸造电磁力数值计算模型,该计算模型在计算电磁力时考虑了磁场分布梯度对电磁力大小及分布的影响。采用互感耦合模型对不同金属熔体内磁场分布以及感应器倾角、感应器电流及频率对磁场分布的影响进行了数值计算研究;并在电磁场计算结果基础上,采用电磁力计算模型计算研究了不同条件下金属熔体内电磁力分布规律。通过研究不同条件下熔体内电磁压力与液柱静压力的平衡关系,对铝、铜、钢及镁铝合金电磁铸造成型的实验条件进行研究,计算得到了铝、铜、钢及镁铝合金实现电磁铸造成型所需的磁感应强度。以金属电磁铸造成型基本条件为依据,提出了判定不同金属电磁铸造成型可行性与难易程度的无量纲判据。利用该判据对不同条件下金属的电磁成型可行性进行分析,得到了不同金属电磁成型所需磁感应强度,所得结果与电磁力数值计算方法所得结果基本吻合。实验研究了铝、锡铅合金的电磁约束成型可行性,实验结果与计算结果基本吻合,从而验证了电磁成型无量纲判据的实用性。电磁成型无量纲判据及电磁力数值计算结果指出,不同金属电磁铸造成型时所需磁感应强度不同:以50mm高的液柱为标准,铝电磁成型所需磁感应强度为0. 045-0. 05T;而钢的约为0. 08-0. 085T,铜的约为0. 094-0. 099T;而镁铝合金则较小,约为0. 038-0. 043T;研究表明,金属电磁铸造所需感应器电流及磁感应强度大小取决于金属的密度,而金属的电导率的大小则决定了电源频率的选择。电磁铸造成型无量纲判据的建立及电磁力计算程序的编制,为不同金属电磁铸造感应器的设计及铸造工艺参数的选择提供了依据。更多还原

【Abstract】 Electromagnetic casting (EMC) is an original material processing technology and a comprehensive subject based on magneto-hydrodynamics (MHD) and combined with metallurgical engineering. Owing to the outstanding merits of EMC in its high smooth surface, good mechanical properties and high production efficiency, which has become an important method to produce high quality aluminum alloys. With the increasingly development of EMC in aluminum alloys and the merits of EMC, more and more research and experiments have been carried out in the EMC for copper, steel and magnesium alloy.The key technique to EMC is the shaping of liquid column of metal under the pressure of magnetic field. Due to the distinct electromagnetic and physical parameters, the feasibility of the electromagnetic shaping under magnetic field is distinct to different metals. For the purpose of analyzing the feasibility of electromagnetic shaping of different metals, the dissertation has studied the feasibility of electromagnetic shaping of Aluminum, steel, copper and magnesium alloy by means of numerical simulation combined with experiment research.The main work for this dissertation is as follows:Based on the principle of electromagnetic casting-the Maxwell’s equations, the electromagnetic force induced in molten metal of cylindrical ingot was analyzed and numerically simulated. Compared with the traditional expression of the electromagnetic forcePm=B2/2μ that simply considers the magnetic flux density in computed grids, themathematical model of electromagnetic force in this paper takes into account the effect of the grads of magnetic field on it. Based on the model of the coupled circuit model, the magnetic field in molten metal was numerically simulated; then the electromagnetic force and the electromagnetic pressure for aluminum, copper, steel and magnesium alloy were also numerically simulated. Meanwhile, the influence of the magnetic field under different inductor, current, frequency on the electromagnetic pressure was investigated. Considering the balance between the electromagnetic pressure on the surface of molten metal and the static pressure of liquid column, the experimental condition of EMC for aluminum, copper, steel and magnesium alloy was studied. As a result, the electric parameters and the minimum magnetic flux density for different metals were presented, which will contribute to the experiments of EMC of those metals.An Electromagnetic Dimensionless Number (EMDN), which can be used to analyze thefeasibility of different metal to achieve EMC, was presented in this paper. By the application of EMDN, the feasibility of electromagnetic shaping for some metals at different experimental conditions were analyzed, and the experimental parameters and the required magnetic flux density to achieve EMC were estimated. The validity of the EMDN was proved by the experiments of Aluminum and Sn-3%Pb alloy.As the results of the research for the feasibility of different meals by means of EMDN and the numerical simulation, the magnetic flux density for different metals is distinct: for aluminum the magnetic flux density required for EMC is about 0.04-0.045T, and for steel that is about 0.08~0.085T, and for copper that is 0.094~0.099T, and for magnesium alloy that is about 0.038~0.043T. Meanwhile, it can be concluded by the research that the magnetic flux density of EMC for some a metal lies on its density, and the conductivity of the metal confines the choice of the frequency in EMC.The establishment of EMDN and the programme of the electromagnetic force provide the guidance for the design of the inductor and the choice of experimental parameters of EMC for different metals.更多还原