Microstructure Characteristics and Melting Behaviors of Smelted Natural Gas-Based Direct Reduced Iron (DRI) with Different Amounts of Biocarbon Addition

Three natural gas-based direct reduced iron (DRI) alloys with varying biocarbon additions were investigated using electron microscopy, thermodynamic calculations, microhardness testing, and high-temperature confocal laser scanning microscope. Increasing carbon content from 2.91 to 5.25 wt pct reduced the complete melting temperature from 1231 to 1174 °C and transformed the microstructure from dendritic ferrite to graphite-rich structures. Oxide particles and impurities formed during remelting and solidification, revealing biocarbon-derived elemental redistribution and providing insights for biocarbon-assisted green steelmaking.