Abstract
The global steel industry accounts for approximately 7 % to 10 % of direct anthropogenic CO2 emissions, necessitating urgent decarbonization strategies. Lightweighting—the reduction of mass while maintaining functional performance—is widely promoted as a key lever for improving sustainability. This paper presents a critical analysis of the lightweighting potential for two distinct steel classes: (I) Fe-C-Si-Mn steels used in civil engineering, typically hot-rolled, and (ii) advanced engineering steels, alloyed with elements like Ni, Cr, and Mo, and routinely heat-treated. Through a life-cycle assessment (LCA) framework developed within the PAASTK project, we are proposing that the sustainability of steel lightweighting is not inherent but is a complex function of production pathways and application contexts. For Fe-C-Si-Mn steels, lightweighting via High-Strength Low-Alloy (HSLA) grades offers a direct and substantial reduction in embodied carbon, where Mn additions should be considered for a multiplicity of factors. For engineering higher alloyed steels, a paradox emerges for some special alloy additions, e.g. Al. The high-performance attributes enabling mass reduction are linked to energy-intensive production, creating a significant "carbon upfront cost" that we are pleased to discuss here. Their net sustainability is conditional on operational energy savings repaying this initial debt. The analysis concludes that a holistic LCA is indispensable, and the transition to Green(er) Steel production is the critical enabler to resolve this paradox and unlock the full sustainable potential of advanced lightweight steels.
The paper also offers a quick report on a demonstrative application of light steel frame (LSF) structures, resulting from the assembly of cold formed members made of high yielding/strength steels belonging to the classes described above. The design concerns a building top addition, which is currently a field of growing interest for LSF structures, especially in seismic areas.