Development of liquid metal process using local imposition of electromagnetic vibration

采用电磁法对锡铅合金进行了固化，通过同时施加静磁场和交流电流来局部施加振荡以控制固化结构。在只施加静磁场的情况下，由于没有振动，得到了粗糙的晶粒，而在同时施加电流和磁场的情况下，整个观察区域的结构完全细化。因此，该方法具有细化凝固组织的作用。并对该工艺的精制机理进行了实验研究。通过改变电磁振动对试样施加的时间，考察了组织的细化期，确定了细化期为凝固的初始阶段。精炼区域与电极的插入位置无关，通过在样品中插入不锈钢丝网来指定电极周围的精炼区域。电磁振动一经激发，试样内部温差就急剧减小，从而引起对流。根据这些实验结果，估计这一过程的机制是在凝固初期，电极周围的枝晶尖端被电磁振动切断，并通过电磁振动引起的对流扩散到整个样品区域。此外，强烈的电磁振动诱导成核。

A Sn-Pb alloy has been solidified by using an electromagnetic method in which oscillation was locally imposed by a simultaneous imposition of a static magnetic field and an alternating current to control the solidified structures. In the case that only the static magnetic field was imposed, coarse grains were obtained due to no vibration, while in the case of the simultaneous imposition of the electrical current and the magnetic field, the structure was completely refined in the whole observed area. Then, this method has a refining function of the solidified structure.Furthermore, refining mechanism of this process has been experimentally examined. The refining period of the structure was examined by changing the imposing period of the electromagnetic vibration on the sample and it was confirmed as the initial stage of solidification. The refining region was specified to be around the electrodes by inserting a stainless steel wire net in the sample while it was independent of the inserting position of the electrodes. Convection was induced by the electromagnetic vibration because temperature difference in the sample drastically decreased as soon as the vibration was excited in the sample. From these experimental results, the estimated mechanism in this process is that dendrite tips around the electrodes are cut off by the electromagnetic vibration in the initial stage of the solidification and it spread to the whole area of the sample by the convection induced by the electromagnetic vibration. In addition, nucleation is induced by an intense electromagnetic vibration.