Investigations on the Interaction Behavior between Direct Reduced Iron and Various Melts

Area of Science:

• Metallurgical Engineering
• Materials Science
• Sustainable Manufacturing

Background:

• The European Union's CO2 emission targets necessitate low-carbon steelmaking alternatives to the traditional blast furnace (BF)-basic oxygen furnace (BOF) route.
• Direct reduction (DR) using natural gas is an established low-carbon steelmaking technology, producing direct reduced iron (DRI) as an intermediate.
• Understanding the melting behavior of DRI in electric arc furnaces (EAF) and submerged arc furnaces (SAF) is crucial for optimizing these alternative processes.

Purpose of the Study:

• To experimentally investigate the initial melting and dissolution behavior of direct reduced iron (DRI) and hot briquetted iron (HBI) under simulated EAF and SAF conditions.
• To evaluate the influence of carbon content in DRI/HBI and the surrounding melt/slag on the dissolution kinetics.
• To analyze the microstructural changes and reactions occurring during the early stages of DRI melting.

Main Methods:

• Experimental simulation of the first few seconds after charging DRI into molten baths.
• Immersion of DRI samples with varying carbon content and HBI into high- and low-carbon melts and high- and low-iron oxide slags.
• Rapid quenching of reacted samples in liquid nitrogen for subsequent surface and cross-sectional analysis.

Main Results:

• Carbon-free DRI dissolution is primarily heat-transfer driven and relatively slow.
• The presence of carbon, either within the DRI or in the melt, significantly accelerates the dissolution rate.
• Carbon also actively reacts with residual iron oxides present in the DRI or slag, influencing the overall process chemistry.

Conclusions:

• Carbon plays a critical role in enhancing the melting efficiency of DRI in EAF and SAF processes.
• Understanding carbon's interaction with DRI and slag is key to optimizing direct reduction-based steelmaking for reduced emissions.
• The findings support the development of more efficient low-carbon steel production pathways.