Influence of a rotating electrode on the droplet formation and the refining effect in the electroslag-remelting process

在电渣重熔过程（ESR）中，金属锭作为电极在渣层中逐渐熔化。在通过渣层后，熔融金属在水冷铜模具内的受控结构中凝固。在此过程中，通过化学和物理精炼机制提高金属的纯度。由于液态金属体积较小和感应搅拌，与铸锭相比，宏观偏析较少。此外，由于局部冷却速率相当低，微偏析也减少了。在炉渣和铜模之间的界面处，有一层1 ~ 3mm厚的炉渣皮凝固。这一层降低了铜模的热损失和金属池中的凝固速度。目前的研究重点是了解去除非金属夹杂物的基本机制，控制柱状凝固的演变和渣皮的形成。所获得的见解将应用于使用旋转金属电极的重熔工艺，这是一种有前途的工艺创新，迄今为止几乎没有研究过。由于电极表面旋转对液态金属产生离心力，金属液滴尺寸减小，液滴比表面积和在渣中的停留时间增加。通过实验和数值研究，了解精炼机理和非金属夹杂物分布是本研究的目的。这是通过以可重复的方式检查镍基718合金以提高清洁度和控制凝固来实现的。

During the electroslag remelting process (ESR) a metal ingot is used as an electrode which is gradually molten in a slag layer. After passing through the slag layer, the molten metal solidifies in a controlled structure within a water cooled copper mold. During this process the metals degree of purity is improved by chemical and physical refining mechanisms. Compared to ingot casting less macro segregation can be observed, due to the smaller volume of liquid metal and the inductive stirring. Furthermore micro segregation is reduced, as the local cooling rates are fairly low. At the interface between slag and the copper mold a 1 to 3 mm thick slag skin solidifies. This layer reduces both the heat loss at the copper mold and the solidification rate in the metal pool.The present research project is focused on understanding fundamental mechanisms of removing non­metallic inclusions, the evolution of controlled columnar solidification and the formation of the slag skin. The insights gained will then be applied to a remelting process using a rotating metal electrode, which is a promising process innovation that has barely been investigated so far. Due to the centrifugal force acting on the liquid metal due to the rotation at the electrode surface, the size of metal droplets is reduced while the droplets specific surface and the residence time in the slag are increased.By carrying out experimental and numerical investigations understanding the refining mechanisms and non-metallic inclusion distribution is the objective of this study. This is to be achieved by examining the nickel based Alloy 718 targeting an improved degree of cleanliness and controlled solidification in a reproducible manner.