Innovative refractory and induction melting systems for titanium and titanium alloys

真空感应熔炼(VIM)是一项强大的技术，可以高效地火法生产、回收和铸造钛材料。真空感应熔炼钛材料的主要限制是对用过的耐火材料的腐蚀，因为钛基熔体具有很高的氧亲和力，具有极强的侵蚀性。此外，气体气氛、热机械应力和合金成分对耐火材料的磨损也有重要影响。在DFG研究单元1372第一阶段的合作下，该项目的目的是研究钛和钛合金在锆酸钙基耐火材料中的熔化，以便将其转化为铸造行业的工业实践。此外，大型真空熔炼炉振动和自流浇注料的开发与冶金工艺调整相结合，将使钛材料的火法冶金回收和一次生产成为可能。为此，应用合作伙伴提供有关铸造技术(Indutherm)、振动和自流浇注料的生产和应用(Refratechnik)以及大型真空熔炼炉(Vacuumschmelze)熔炼活性金属和难熔金属的专业知识和服务。在实验室熔化实验(L 05-1)中，将特别研究条件和工艺窗口，以最大限度地减少熔体中的氧污染，并达到标准的钛质量。因此，特别关注Ti6Al4V以及铝、钒、锡等合金元素对耐火材料腐蚀的影响。为此，将研究熔化温度和时间以及添加剂的过热温度和脱氧效果。首次应用过多的惰性气体压力来减少耐火材料和熔体中的钙蒸发，因为众所周知，含钙耐火材料往往会蒸发，导致氧气快速回升，从而污染熔体。这些冶金研究对铸造和钛材料的回收都具有很高的兴趣。真空感应熔炼回收钛材料的技术可行性的一个重要要求是熔炼炉的尺寸足够大。到目前为止，所有有前途的制备钛材料的替代方法，如电化学还原(FFC法)都未能大规模生产。因此，在14个L坩埚上进行的放大实验将最终探索在不超过相关污染水平的情况下熔化耐火坩埚中的钛材料的条件。

Vacuum induction melting (VIM) is a powerful technology allowing an efficient pyrometallurgical production, recycling as well as casting of titanium materials. The main limitation for vacuum induction melting of titanium materials is the corrosion of the used refractories, because due to their high oxygen affinity titanium based melts are extremely aggressive. Moreover, the gas atmosphere, thermomechanical stresses and the alloy composition have an important influence on the wear of the refractories. Based on the cooperation of the first phase of the DFG Research Unit 1372, the aim of this project is to investigate the melting of titanium and titanium alloys in calcium zirconate based refractories in order to allow a transfer into the industrial practice of the casting industry. Furthermore, the development of vibration and self flowing castables for large VIM furnaces combined with metallurgical process adaptions will allow the pyrometallurgical recycling and primary production of titanium materials. For that purpose the application partners provide their expertise and services regarding casting technology (Indutherm), the production and application of vibration and self flowing castables (Refratechnik) as well as the smelting of reactive and refractory metals in large VIM furnaces (VACUUMSCHMELZE). In laboratory melting experiments (0,5 - 1 l) conditions and process windows will be investigated especially to minimize the oxygen contamination of the melts and to achieve standard titanium qualities. Thereby, a special focus is Ti6Al4V and the influence of alloying elements such as aluminum, vanadium, and tin on the refractory corrosion. For that purpose the melting temperature and time as well as the super heating temperature and deoxidizing effect of additives will be investigated. For the first time an excess inert gas pressure will be applied to reduce the calcium evaporation from the refractories and from the melt, because it is known that calcium containing refractory materials tend to evaporate causing a fast oxygen pickup and hence contamination of the melt. These metallurgical investigations are of high interest for both casting as well as for the recycling of titanium materials. An important requirement for the technical feasibility of a recycling process of titanium materials by vacuum induction melting is a sufficient large size of the melting furnace. So far all promising alternative methods to produce titanium materials such as the electrochemical reduction (FFC process) failed on a large scale production. Therefore, scale up experiments in 14 l crucibles will finally investigate conditions to melt titanium materials in refractory crucibles without exceeding relevant contamination levels.