Development of Roll Formable Ultra High Strength Steels for Energy Efficient Manufacture of Lightweight Crash Resistant Automotive Structures

This project is concerned with the development of Ultra High Strength Steels (UHSS - steels with a ultimate tensile strength greater than 1000 MPa) specifically designed to be formed by a novel low energy and flexible manufacturing process, known as 3D roll forming, to produce lightweight crash resistant structures for the automotive industry. The roll forming process is an incremental bending process that turns a flat sheet into a structural profile as compared to traditional stamping processes that involves severe stretching of the sheet to create the required part geometry. The 3D roll forming process is extremely flexible - leading developers of the technology claim a single set of tooling can be used to manufacture up to a quarter of the automotive structure, whereas the stamping process requires an expensive set of tools to be manufactured for each individual part. Furthermore a roll forming line only take 10 to 16 weeks to setup as compared to 18 months for a stamping line. Today ultra high strength automotive steels are usually formed using the energy intensive hot stamping as it is very difficult, and costly, to design steels that achieve the required high room temperature uniform ductility in combination with an ultimate tensile strength in excess of 1000 MPa. As roll forming only requires the material to be bendable, it is proposed that steels with low work hardening rates and a high yield ratio (yield strength /ultimate tensile strength) could be suitable for shaping using this process. The development of UHSS for roll forming allows simpler compositions that are leaner and have a lower alloy cost which reduces exposure to raw materials supply issues (scarcity), have better compatibility with existing capabilities and are more consistent (higher yield/lower scrap). This is potentially a disruptive technology that could revolutionise the manufacture of automotive structural members. It will: eliminate the need for energy intensive hot stamping currently used for shaping UHSS; dramatically reduce tooling requirements and the energy associated in their manufacture; increase material utilisation; avoid the need to use energy intensive materials for lightweighting such as Al, Mg and CFRP; all whilst producing a product that will yield significant CO2 savings during use. It is estimated that if roll formed steel replaced 50 kg of hot stamped components in a vehicle, then 40,000 tonnes of CO2 could be saved in the UK automotive manufacturing industry per annum.

Project partners: The primary beneficiaries of the project will be the industry partners who will benefit through exploitation of the research outcomes. Tata Steel will gain a competitive advantage in a key market by offering a considerable advantage over other steels and competitor materials such as aluminium and carbon fibre composites. Hadley Group will find a sustainable market for their process and upstream users, such as Jaguar LandRover, who will benefit from the availability of an ultra high strength steel that can be formed at low temperature in a simple process.
Wider Industrial Impact: Apart from the benefits to the industrial partners given above, Tata Steel works directly with numerous engine and car manufacturers (who cannot be named for commercial reasons), and these sectors will see their products improve as a result of this research through the use of UHSS, offering a competitive advantage over more expensive materials such as aluminium alloys and CFRP. More importantly, energy consumption will be reduced both in terms of the alloy production and the forming process. The research will also be directly disseminated via collaborations with the HVM Catapult centres, in particular the AFRC (a partner in the project). In addition, the project outcomes will provide scientific support for further development of 3D roll forming.
Societal: The wider public will benefit from the longer term benefits of lightweighting of passenger cars with improved safety. This research has direct impact on reducing the environmental impact of passenger vehicles by lowering the CO2 emissions generated from primary metal production, component manufacture and fuel consumption over the lifetime of the vehicle. The results will also be fed into the relevant topics of the school science curriculum (materials,CO2 usage) to ensure that teaching and students have access to cutting edge research.