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，允许有效的热法冶金生产，回收以及钛材料的铸造。钛材料真空感应熔炼的主要限制是对所用耐火材料的腐蚀，因为钛基熔体由于其高氧亲和力而具有极强的腐蚀性。此外，气体气氛、热机械应力和合金成分对耐火材料的磨损有重要影响。基于DFG研究单位1372第一阶段的合作，该项目的目的是研究锆酸钙基耐火材料中钛和钛合金的熔化，以便将其转移到铸造工业的工业实践中。此外，为大型VIM炉开发振动和自流动浇注料，结合冶金工艺的调整，将使钛材料的火法冶金回收和初级生产成为可能。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（Refratechnik）的生产和应用以及在大型VIM炉（VACUUMSCHMELZE）中熔炼活性和难熔金属的专业知识和服务。在实验室熔化实验（0.5 - 1l）中，将研究条件和工艺窗口，特别是为了尽量减少熔体的氧污染并达到标准钛质量。因此，特别关注Ti6Al4V和合金元素如铝、钒和锡对耐火材料腐蚀的影响。为此，研究了熔炼温度、熔炼时间以及添加剂的过热温度和脱氧效果。这是第一次使用过量的惰性气体压力来减少从耐火材料和熔体中蒸发的钙，因为已知含有钙的耐火材料往往会蒸发，导致氧气快速吸收，从而污染熔体。这些冶金学研究对铸造和钛材料的回收都有很高的兴趣。真空感应熔炼回收钛材料工艺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，所有有希望的替代方法生产钛材料，如电化学还原（FFC工艺）在大规模生产中失败。因此，在14l坩埚中进行大规模实验将最终研究在不超过相关污染水平的情况下在耐火坩埚中熔化钛材料的条件。

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.