Technology Development and Tool Concepts for High-Temperature Forming of Titanium

Abstract

Due to its excellent material properties, titanium is an important structural material for several application fields in the aerospace industry, the chemical industry, medical engineering or marine technologies. Especially its excellent weight-strength ratio, high-temperature strength corrosion resistance and not least its biocompatibility enables a wide field of special applications. These properties can be improved by alloying of other chemical elements. Despite good availability of resources and moderate world market prices, there is only a limited application range for titanium. Main reasons comprise technological problems in manufacturing processes, particularly related to establish forming technologies such as deep drawing or hydroforming. The forming tool is of significant importance in forming technologies. Beside the function of shape storage the tool must provide the essential forming parameters such as mechanical functions (e.g. blank holder, sealing etc.), but also temperature and tribology. Especially the tribology, also related to forming temperatures, is very critical during titanium forming due to a distinctive tendency of adhesion. For this reason, a high number of titanium components are manufactured by milling. Parts made by forming of basically thin blank, show only low complexity. More complex components are made by welding of simple shaped parts. Thus, large-series manufacturing of titanium components is limited due to the extensive production cost. By describing three examples, this paper shows possibilities and challenges in manufacturing of titanium components based on sheet metals. Beside the process parameters, a special focus of the investigations lies on the coating of forming tools. Example one is cold forming of thin titanium blanks to speaker cones. The second example demonstrates superplastic forming of a medical application, and finally the third example consists of hot gas forming of a titanium exhaust manifold. The investigations have shown that based on optimized technological parameters in combination with new tool coatings, the manufacturing of complex sheet metal based titanium applications is applicable for large-series production.