Innovative refractory and induction melting systems for titanium and titanium alloys

真空感应熔炼（Vim）是一种强大的技术，可以有效地进行高温冶金生产，回收以及钛材料的铸造。钛材料的真空感应熔炼的主要限制是所用耐火材料的腐蚀，因为钛基熔体由于其高氧亲和力而极具侵蚀性。此外，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。基于DFG研究单位1372的第一阶段的合作，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，以便转移到铸造行业的工业实践中。此外，振动和自流浇注料的大型Vim炉结合冶金工艺适应的发展将允许高温冶金回收和钛材料的初级生产。为此，应用合作伙伴提供铸造技术（Indutherm）、振动和自流浇注料的生产和应用（Refratechnik）以及在大型Vim炉中熔炼活性和难熔金属（VACUUMSCHMELZE）方面的专业知识和服务。在实验室熔化实验（0.5 - 1升）的条件和工艺窗口将进行研究，特别是要尽量减少熔体的氧污染，并达到标准的钛质量。因此，一个特别的焦点是Ti6 Al 4V和合金元素，如铝，钒和锡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。第一次将施加过量的惰性气体压力以减少钙从耐火材料和熔体中的蒸发，因为已知含钙耐火材料倾向于蒸发，导致快速的氧吸收并因此污染熔体。这些冶金研究对于钛材料的铸造和回收都具有很高的意义。通过真空感应熔炼回收钛材料的工艺的技术可行性的重要要求是熔炼炉的足够大的尺寸。到目前为止，所有有前途的替代方法，以生产钛材料，如电化学还原（FFC过程）失败的大规模生产。因此，在14升坩埚中的放大实验将最终研究在耐火坩埚中熔化钛材料而不超过相关污染水平的条件。

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.