Steel Without Coal Still Needs Carbon

Hydrogen-based direct reduced iron (H2-DRI) eliminates coal from steelmaking but produces iron sponge with no inherent carbon content. Steel requires precisely controlled carbon levels (0.02–2.1% by mass) to achieve desired mechanical properties. Without a fossil carbon source, steelmakers must find alternative carburization methods while managing a new metallurgical challenge: residual hydrogen in the DRI interacts with dissolved carbon, triggering hydrogen-enhanced localized plasticity (embrittlement) that worsens at higher carbon content — creating a fundamental tension.

Steel production accounts for ~7% of global CO2 emissions. H2-DRI is the leading decarbonization pathway, with HYBRIT (Sweden) producing the first fossil-free steel in 2021 and H2 Green Steel building commercial capacity. But if carbon control and embrittlement issues are not solved, H2-DRI steel cannot meet existing grade specifications — blocking substitution for the 1.9 Gt of steel produced annually.

HYBRIT demonstrated the overall H2-DRI-EAF pathway. Biochar, synthetic methane, and direct carbon injection into the electric arc furnace (EAF) are being tested as fossil-free carbon sources. However, controlling carbon distribution uniformly in DRI pellets without natural gas is metallurgically difficult. Biochar introduces variability in carbon quality and ash composition that affects final steel properties. Hydrogen remaining in the DRI interacts with carbon in solution during subsequent processing, activating embrittlement — and this worsens at exactly the carbon levels needed for structural steel grades. Quality control systems designed for blast-furnace steelmaking do not transfer to the H2-DRI-EAF process.

Reliable carburization methods producing consistent carbon content in H2-DRI without fossil inputs — validated across multiple steel grades. Better metallurgical understanding of hydrogen-carbon interaction in DRI-EAF processing to predict and manage embrittlement. Quality control systems validated for H2-DRI steel meeting existing structural steel grade specifications.

A team could characterize hydrogen-carbon interactions in DRI pellets processed with different non-fossil carbon sources (biochar, synthetic methane) using mechanical testing and microstructural analysis. Alternatively, a process engineering team could design a lab-scale carburization protocol using biochar and measure carbon distribution uniformity. Materials science, metallurgy, and process engineering skills apply.