Direct and Sustainable Stainless Steelmaking from Nickel and Chromite Ores by Hydrogen Plasma Smelting Reduction Process  

Stainless steel, known for its exceptional properties and diverse applications, conventionally requires a multi-stage process that generates significant CO₂ emissions due to the use of fossil-based carbon reductants. This study investigates hydrogen plasma smelting reduction as a novel, sustainable, and efficient method for producing stainless steel directly from lateritic nickel ores and chromite ores. The research aimed to examine the effect of ore proportion on AISI 300 series stainless steel production and assess the reduction process over time through thermochemical calculations and experimental studies. Increasing the proportion of chromite ore in the feed raises Cr content and reduces Ni content in the metal while also increasing Cr₂O₃ and Al₂O₃ content in the oxide. A briquette comprising 30% chromite ore and 70% calcined nickel ore yields better results for AISI 300 stainless steel, with Fe, Cr, Ni, and Si contents of 62.95%, 19.37%, 11.83%, and 0.72% after 180 seconds of hydrogen plasma exposure. The evaluation of reduction time shows that nearly all NiO is converted into Ni after 60 seconds of smelting reduction, while FeO is almost fully converted into Fe after 120 seconds of smelting reduction. AISI 300 series stainless steel was successfully produced after 120 seconds of reduction, achieving Fe, Cr, Ni, and Si contents of 64.36%, 21.92%, 10.08%, and 0.61%, respectively. Process optimization remains promising, as the Cr₂O₃ content in the slag is still relatively high at 15.52%. This ultra-fast and direct production method holds significant potential to transform stainless steel production by reducing environmental impact and enhancing process efficiency, including the elimination of an AOD (argon oxygen decarburization) converter and/or a VOD (vacuum oxygen decarburization) in stainless steelmaking.