The Influence of the Mould Cooling Temperature on the Surface Appearance and the Internal Quality of ESR Ingots

One of the main benefits of the ESR process is to obtain an ingot surface which is smooth and allows a subsequent forging operation without any surface dressing. The main influencing factor on surface quality is the precise controlling of the process such as melt rate and electrode immersion depth. However, the relatively strong cooling effect of water as a cooling medium can result in the solidification of the meniscus of the liquid steel on the boundary liquid steel and slag which is most likely the origin of surface defects. The usage of different cooling media like ionic liquids, a salt solution which can be heated up to 250 °C operating temperature, might diminish the meniscus solidification phenomenon. This paper shows the first results of the usage of an ionic liquid as a mould cooling medium. In doing so, 210 mm dia. ESR ingots were produced with the laboratory scale ESR furnace at the University of Applied Sciences Upper Austria using an ionic liquid cooling device developed by the company METTOP. For each trial melt, different inlet and outlet temperatures of the ionic liquid were chosen and the impact on the surface appearance and internal quality were analyzed. Ultimately, an effect of the usage of ionic liquids as a cooling medium could be determined and these results will be described in detail within the scope of this paper.