Bringing back high-quality steel components
UHSS is an obvious choice for optimised crash performance when used in structural components of the automotive industry. However, the extreme temperature and pressure (thermomechanical) conditions required during forming significantly reduce tool lifetime and increase product cost. The material thus faces intense competition from lightweight composites that are easy to process and often imported from countries outside the EU. A large consortium of industrial and research partners addressed this challenge with EU funding of the project 'Development of new tool materials with tailored thermomechanical properties' (TAILORTOOL). Researchers intended to enhance tool performance by developing novel functionally graded materials (FGMs). These FGMs would be capable of demonstrating a gradual variation in either thermal conductivity or in microstructure, depending on the application. Scientists were also able to customise the products themselves by implementing novel materials in the machining tools. Scientists focused on four different materials and processes covering hot stamping, hot forging, high-pressure die casting and cold forming. Processed materials consisted of UHSS, hardened Grade B steel sheets and light alloys. Information regarding thermomechanical effects on industrial tools in service is not readily available. Scientists therefore developed specialised sensors with fast response times to accurately measure, for the first time, heat flux and local temperature at the contact zone. Data were fed into finite element (FE) simulations to optimise tool materials and properties. Researchers developed three different families of materials and tools for the given manufacturing processes. These were specially tailored to enhance tool performance, process efficiency and product quality. Thermal properties were selected to enhance resistance to thermal fatigue or to enable hot stamping to produce components with functionally graded properties. Mechanical properties were optimised through enhanced microstructure and the use of hard particles to increase resistance to mechanical damage. The TAILORTOOL project delivered novel materials for machining tools capable of withstanding the extreme thermochemical conditions required to form UHSS. Developments are expected to have major positive impact on the steel industry and on manufacturers, and even on the crash performance of future cars.
