Comparative investigation of scale formation on various steel grades during reheating under air-fuel combustion with hydrogen and natural gas in a semi-industrial experimental design

The steel industry must undergo significant transformation to align with the Paris Climate Agreement. One potential measure is replacing natural gas with hydrogen as fuel in reheating furnaces. While scale formation during reheating under conventional natural gas/air combustion has been well studied, research on hydrogen/air combustion remains limited. This work investigates the scale formation of fifteen steel grades with varying chemical compositions and applications. The steels were heat-treated in a semi-industrial setup under industry-relevant conditions. As a measure of scale formation, the specific mass gain was determined for three holding times using four samples per condition. For seven steels, the difference in scale formation between the two combustion atmospheres was within 5 %, and only two steels exhibited a moderate increase of over 15 % (hydrogen/air compared to natural gas/air). These results indicate that the examined steel grades are largely suitable for hydrogen-based reheating processes. • Examination of samples cut from blooms or billets retaining their as-cast surfaces. • Comparison of the scale formation in hydrogen/air to natural gas/air. • Investigation of 15 steel grades with varying composition, max. 1 wt% C. • Linear relation between increasing specific mass gain and decreasing C content.