Steel production is increasingly shifting into a circular, recycling-based process, which will lead to a change in chemical compositions in the near future. On the one hand, this is by contaminated scrap fractions, which contain impurities such as copper and on the other hand, the environmental impact of the individual raw materials is increasingly being taken into account. For enhanced circularity, the degree to which different varieties of iron (produced by conventional production, direct reduction or recycling) and alloying are mixed, are crucial for recyclability and reusability. 

When developing an alloy concept, the focus is no longer just on costs and desired material properties. By considering the environmental impact a holistic optimization concept must therefore be applied. The environmental impact is not only caused by the individual raw materials of the alloy, but also by the production processes used to manufacture products from these raw materials. The alloy composition can vary production parameters or change entire production steps. This is the case with i.e. air-hardening steels, which achieve a martensitic structure through air cooling alone. Due to i.e. the avoidance of downstream heat treatment, the shortened process chain can save large amounts of energy and emissions.

Life cycle assessment (LCA) in accordance with the DIN EN ISO 14040/14044 standard is used for the ecological assessment of individual steel grades, taking into account the alloy composition and production process. The focus is on the “cradle to gate” scope of analysis and therefore up to the finished product. Aspects such as CO2 footprint, toxicity, energy and water consumption are considered and compared with the material properties and costs.

Based on this approach a holistic optimization concept was designed and performed. For this matter, the various aspects were analysed and compared. This analysis was made for individual steels up to the industrial semi-finished product by ecologically assessing the melting and forging processes. Together with the costs and properties, a comprehensive evaluation was performed, enabling a data-based sustainable decision process for alloy design.

Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany ́ s Excellence Strategy – EXC-2023 Internet of Production – 390621612