铝板坯热顶—电磁铸造工艺研究

【作者】 何文庆；

【导师】 张兴国；

【作者基本信息】 大连理工大学 ， 材料加工工程， 2004， 硕士

【摘要】 电磁铸造过程中金属液柱在自由表面状态下凝固，是真正的无模铸造，极大地改善了铸锭的表面质量。但是，由于电磁铸造中的电磁搅拌作用以及浇注冲击使液柱表面氧化膜被破坏并不断形成新的氧化膜，导致电磁铸造铸锭表面和内部产生氧化夹杂，并增加了铸锭的含气量。本文在铝板坯电磁铸造中应用热顶电磁铸造思想，进行了实验和模拟研究，得到具有一定指导意义的研究结果： 1．设计了一整套铝板坯热顶—电磁铸造装置，设计了多种屏蔽罩结构，测量了相关条件下的磁感应强度分布，研究了磁场的分布规律，确定了实验所需的电源功率以及实验的凝固界面位置； 2．实验表明，对开式屏蔽罩与整体式屏蔽罩相比，既有效地抑制了液柱顶部磁场，保证液柱的稳定，又不明显削弱液—固界面区域的磁感应强度，有利于实现半悬浮成型条件； 3．进行了大量的拉坯实验，确定了浇注温度、液柱高度和冷却水量等相关工艺参数，铸造出光滑的铸锭，发现夹杂均被热顶滞留在铸锭的顶面，被阻止进入铸锭内部和表面，证明热顶确实有效消除了铸锭的夹杂缺陷； 4．对热顶—电磁铸造铸锭试样进行含气量分析，发现试样的含气量比普通连续铸造、电磁铸造和电磁连铸的试样的含气量均低，从另一方面证明了热顶增强了系统的稳定性，起到了截留夹杂的效果； 5．对铝圆锭热顶—电磁连铸技术进行了相关实验研究，确定了合理的工艺参数，制作出表面优于电磁连铸的铝圆锭； 6．利用有限元软件，对铝扁锭热顶—电磁铸造系统磁场进行了数值模拟计算。更多还原

【Abstract】 Molten metal solidifies in free surface state during electromagnetic casting (EMC) process. EMC is real non-mold foundry which improves surface quality of ingot greatly. But the continuously newborn oxide film in the surface of liquid column is damaged by the electromagnetic stirring in EMC and the pouring-in liquid metal, which results in the generation of inclusion in the inner and surface of ingots. And air content of ingots increases too. In this paper, the thought of hot-top EMC is used in aluminum slab EMC, and a lot of experimental and simulant researches are proceeded, based on which, some results with guiding meaning have been obtained.A whole set of hot-top EMC devices of aluminum slab and some types of screen structures were designed. The distribution of magnetic field under correlated conditions was measured. And the distribution rule of it was researched, based on which, the needed power supply and the position of freezing interface were determined.It is indicated by experimental result that, compared with integral screen, split screen can not only depresses magnetic field in the top of liquid column, which ensures the stabilization of liquid column, but also does not weaken magnetic field in the region of liquid-solid boundary obviously, which is favorable for meeting the half-suspending condition of molding.The rational technique parameters such as the position of the freezing interface, pouring temperature, cooling water strength and the height of liquid column were obtained by lots of experiments. Ingots with smooth surface were gained. It is found that the inclusion is retained in the top of ingot, and it is prevented of entering the inner and surface of ingots, which means that hot-top eliminates inclusion flaw of ingot efficiently.Air content test of test samples founded by hot-top EMC, DC, EMC and electromagnetic continuous casting are analyzed. It is found that air content of the first one is lower than others’, which proves that hot-top does strengthen system stability and has the effect of removing inclusion.Experimental researches on hot-top electromagnetic continuous casting of Al round ingots are made. Rational technological parameters are confirmed, and Al round ingots whose surface quality is better than which of electromagnetic continuous casting ingots are casted.In this paper the calculation of numerical simulation for the magnetic field of hot-top EMC system was set up by using software of finite element software.更多还原