This project aims to generate a new class of affordable martensitic stainless steels for the automotive sector. In detail, there are two main objectives. First, to develop new martensitic stainless steel grades containing retained austenite, using a combination of novel heat treatments (quenching and partitioning -QP) and steel chemistry optimisation, to give unique combinations of strength and ductility, suitable for lightweight automotive applications. The second main objective is to facilitate the industrial implementation (manufacture and use) of these new grades. The first objective will be achieved by alloy and heat treatment design, first using models, and second via experiments, gradually scaling up from small heats with dilatometer heat treatment on small samples, to large heats followed by Gleeble heat treatment on larger hot rolled strips, and finally to lab pilot scale fully processed sheet production. At each iteration, the microstructure and mechanical properties will be assessed, in order to assist in optimization of properties in the final fully processed sheets. The second objective will be met by detailed experimental studies on critical automotive properties i.e. weldability, formability, fatigue, and corrosion. In addition, life cycle cost studies, component forming simulations, assessment of industrial processing windows, will be carried out with appropriate benchmarking to other steels, in order to assist in the industrial implementation of the developed steels. The project results are expected to benefit European stainless steel producers through the realisation of new and affordable martensitic stainless steel grades suitable for breakthrough into the lightweight automotive sector. In addition, the new grades are expected to offer attractive properties for other typical martensitic stainless steel applications such as those requiring improved corrosion and strength combinations.
The main objectives of the QPINOX proposal are:
- To develop new martensitic stainless steel grades containing retained austenite, using a combination of novel heat treatments (quenching and partitioning -QP) and steel chemistry optimisation, to give unique combinations of strength and ductility suitable for lightweight automotive applications.
- To gain unique knowledge on the QP mechanisms and austenite stability (chemical, thermal, mechanical) in the designed stainless steels.
- To establish the microstructure-property relations highlighting the critical microstructural parameters.
- To characterise important automotive application related properties i.e. weldability, corrosion, fatigue and formability.
- To facilitate the industrial implementation (manufacture and use) of these new grades considering critical application properties, industrial processing windows, low-cost and flexible chemistries, automotive component design, life cycle costs and appropriate benchmarking to AHSS carbon steels and austenitic stainless steel solutions.