Abstract
The transition to hydrogen-based direct reduction of iron (DRI) represents a key pathway toward decarbonizing the steel industry. While the upstream reduction process has received significant attention, the downstream melting behavior of hydrogen-reduced DRI (H-DRI) remains less understood. This study explores the melting characteristics of H-DRI compared to conventional carbon-containing DRI, with a focus on slag reactions and operational implications in electric melting furnaces. Initial laboratory-scale melting trials were conducted using DRI samples with varying carbon contents, including H-DRI produced via hydrogen reduction. Observations revealed marked differences in slag behavior: carbonaceous DRI samples exhibited vigorous slag foaming, while H-DRI showed minimal gas evolution and no foaming. These differences suggest that carbon content plays a critical role in driving in-situ reduction reactions and gas generation during melting, which in turn influence slag dynamics. Additionally, energy measurements indicated a notable difference in melting requirements between H-DRI and carbonaceous DRI, further emphasizing the role of carbon in pellet heating. Complementary thermogravimetric analysis (TGA) with FTIR confirmed that carbon-containing DRI undergoes staged reduction of residual iron oxides, releasing CO and CO₂. In contrast, H-DRI showed negligible mass loss and gas evolution, indicating a fundamentally different reaction and melting pathway. These findings have important implications for slag design, energy efficiency, and furnace operation in hydrogen metallurgy. As interest moves toward large-scale adoption of H-DRI, understanding its melting behavior is essential for optimizing process conditions, minimizing refractory wear, and ensuring stable slag-metal interactions. This work contributes to the broader effort of adapting steelmaking practices to accommodate hydrogen-based feedstocks and supports the development of low-carbon metallurgical technologies.