Decarbonisation of steelmaking: the challenge

Today, steel production accounts for about 7% of CO2 emissions. As the global demand for steel continues to grow, solutions for greener steel are urgently needed to fight climate change. ArcelorMittal intends to play a leading role in reshaping the steel-making industry, expressing strong commitments to limit CO2 emissions in the years to come. For Europe, ArcelorMittal is committed to reducing emissions by 35% by 2030 – on the journey to emission-free steelmaking in 2050.

One of the key factors in achieving this decarbonisation objective is to increase the use of recycled materials or scrap in the steel-making process. Unfortunately, increasing scrap levels will surely result in an increased level of residual elements in the final products. As conventional steel production has historically aimed at ‘purifying steel-making’ – and thus decreasing the amounts of (undesired) residuals – their effect at higher levels on processing and product properties is still to be explored. To tackle this, a wide range of knowledgebuilding activities is ongoing: numerical simulations and data-mining efforts, lab pilot scale studies and industrial trials focusing on determining whether an increase in residual elements would generate risks during processing or affect the quality of the final products. The knowledge built by these activities is expected to generate a clear view on the maximum levels of residuals that can be tolerated for all product families, including ideas for possible adjustments in the manufacturing process to enlarge product tolerance towards residuals. The new knowledge should also provide clear guidelines for internal adaptations and customer specifications for steel compositions in the future. In a first wave, the work is focused on using more scrap in existing steel-making processes. Another working axis is focused on the second wave of route modifications, which includes the implementation of ‘new’ technologies in the steel-making process, such as electric arc furnaces and direct reduced iron production, which further complicates the purity level of the steel obtained. The direct reduction process will start using natural gas – which will already reduce emissions by an order of magnitude of 3 compared to blast furnace routes. The final goal is to use green hydrogen in the direct reduced iron process, which makes production almost C-emission free, but

again adds additional constraints on steel product quality. Several major investments for the ‘new technology’ axis have been announced recently, but implementation will be rolled out in 2025 and beyond. Our current R&D role is mainly to anticipate the effects of technological choices on the manufacturability and performance of the steels produced using these new technologies. Without being restrictive at this early stage, some anticipated effects on steel quality currently being investigated are the effect of residual elements on strength, toughness and other in-use performances, their effect on the galvanising and pickling process, as well as surface quality issues such as hot shortness. Fascinating to realise that, just 5 years from now, we aimed to produce 50% of the order book via brand-new metallurgical routes implementing the new ‘green’ processes.

It is exciting to see how environmental commitments can transform steel production, and to be part of this revolution!

Ulrike Lorenz

The decarbonisation objectives of the steel industry are pushing us to think steelmaking from a completely new perspective.

Koenraad Theuwissen