COLTS

Casting of Large Ti Structures

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 Obiettivo del progetto (Objective)

'This proposal is in response to the call for EU and China collaboration on casting large Ti structures. The consortium consists of 7 EU and 7 Chinese partners. This proposal aims to make a step-change for casting of large Ti components by overcoming some key challenges in the casting process. Such a step-change is critical if the production of large Ti components is to meet the requirement in cost reduction by endusers, the requirement of CO2 reduction and raw material wastage reduction in every step of component manufacturing process by the endusers and by the society. This step change will involve the development of the centrifugal casting process by which the filling of thin sections of large Ti structures will be improved so that significantly fewer and smaller defects will be present in the component and a significantly higher production yield rate will be achieved. Further development will be carried to improve the gravity casting process which is important for casting asymmetrical components such as Ti airframes. Those developments will be closely coupled with the development of computer modelling in terms of better understanding and predicting liquid filling of the mould, defect formation and distribution, control of the dimensional accuracy of the cast component together with the development of a stronger wax and optimum ceramic mould material if required in order to meet the component dimension tolerance specified. The microstructure and mechanical properties including that of heat treated and welded castings must be optimised. If successful, this project will lead to significant cost reduction in producing large Ti components; removal the USA monopoly of supply of aeroengine Ti casings and significant reduction of CO2 and of Ti raw material wastage incurred in current manufacturing processes. It will also lead to more application of light Ti structures in aerospace and space, thus weight and fuel reduction by making Ti structure commercially viable.'

Introduzione (Teaser)

Reducing production costs and enhancing sustainability and performance are key goals of the aerospace sector. Novel casting technology developed with EU support will enable improved manufacture of titanium (Ti)-based components to address all three.

Descrizione progetto (Article)

Ti alloys are widely used in the aerospace industry given their excellent strength, low density, corrosion resistance and durability. Large Ti components are typically manufactured using thermochemical processing. Although it is expensive, it is currently preferable to more cost-effective casting due to superior quality and reliability of the product.

A Chinese and European consortium initiated the EU-funded 'Casting of large Ti structures' (http://www.colts-project.eu/ (COLTS)) project to improve the quality of cast products and reduce the cost even further. Casting is a process whereby molten metal is poured into a hollow mould and the material is cooled into a solidified shape. The Chinese team brought extensive experience in casting and in electron beam welding of Ti alloys. This was complemented by European group expertise in computer modelling of casting and welding and in assessment of materials' microstructures and properties. Selected demonstrators were a large cylinder, a cubic space frame, a doorframe and cross-connectors containing many thin-walled components.

Molten Ti alloys are highly reactive and must be melted under special conditions that limit their temperature. This in turn makes filling of mould cavities difficult, particularly for thin and/or large castings. Researchers applied metal-based coating to strong waxes developed by the consortium to make the final moulds for casting the parts with limited wax distortion. The coatings significantly inhibited reactivity with the molten alloy.

Welded and cast components showed promising ability to meet requirements of dimensions, surface finishes and mechanical properties. Subsequent modelling suggests that processes can be optimised to do so completely. Project components are now on display at the European Space Agency's museum in the Netherlands, attesting to the significance of outcomes.

COLTS Ti casting technology will soon result in lighter, lower-cost and high-performance components for the aerospace sector with lower environmental impact all along the product life cycle. Results will provide a boost to the EU aerospace sector and have important applications to numerous other fields in which Ti is being used.