Key Takeaways & Executive Findings
- •• Hydrogen plasma smelting reduction enables direct stainless steel production from lateritic nickel and chromite ores in a single step, eliminating the need for AOD and VOD converters. • Optimal feed composition of 30wt% chromite ore and 70wt% calcined nickel ore yields AISI 300 stainless steel with Fe, Cr, Ni, and Si contents of 62.95wt%, 19.37wt%, 11.83wt%, and 0.72wt% after 180 seconds. • NiO is fully reduced to Ni within 60 seconds, while FeO is nearly fully reduced to Fe within 120 seconds, demonstrating ultrafast kinetics. • The process significantly reduces CO2 emissions by replacing fossil-based carbon reductants with hydrogen, offering a sustainable alternative for stainless steelmaking.
Abstract
Stainless steel, known for its exceptional properties and diverse applications, conventionally requires a multistage process that generates considerable CO2 emissions by using fossil-based carbon reductants. This study investigated hydrogen plasma smelting reduction as a novel, sustainable, and efficient method for producing stainless steel directly from lateritic nickel 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. Results showed that increasing the proportion of chromite ore in the feed raises Cr content and reduces Ni content in metals while increasing Cr2O3 and Al2O3 content in oxides. A briquette comprising 30wt% chromite ore and 70wt% calcined nickel ore yields better results for AISI 300 stainless steel, with Fe, Cr, Ni, and Si content of 62.95wt%, 19.37wt%, 11.83wt%, and 0.72wt%, respectively, after 180 s of hydrogen plasma exposure. Nearly all NiO compounds are converted into Ni after 60 s of smelting reduction, whereas FeO compounds are almost fully converted into Fe after 120 s of smelting reduction. AISI 300 series stainless steel is successfully produced after 120 s of reduction, achieving Fe, Cr, Ni, and Si content of 64.36wt%, 21.92wt%, 10.08wt%, and 0.61wt%, respectively. Process optimization remains promising because the Cr2O3 content in the slag is still relatively high at 15.52wt%. This ultrafast and direct production method holds considerable potential to transform stainless steel production by reducing environmental impact and enhancing process efficiency. Specifically, the method eliminates the use of an argon oxygen decarburization converter and vacuum oxygen decarburization in stainless steelmaking.
1. Introduction
Stainless steel is one of the most remarkable materials ever discovered because of its exceptional properties and countless applications [1]. However, stainless steel production involves multiple stages with highly complex operating conditions and technologies that still rely on fossil-based carbon reductants, which generate CO2 emissions. To date, no research has successfully developed a single-stage process for producing green stainless steel directly from ores.
Stainless steel was discovered in the 20th century after the discovery of iron–chromium alloys (ferrochrome) in the 19th century. Early challenges in stainless steelmaking included significant chromium losses during carbon removal. The “rustless process” utilized electric arc furnace (EAF) to melt carbon steel scrap, burned lime, iron ore, and large amounts of expensive low-carbon ferrochrome (LC-FeCr) [2]. A more efficient process emerged in the late 1940s, involving the melting of stainless-steel scrap, high-carbon ferrochrome (HC-FeCr), nickel, and lime, followed by oxygen blowing at 1850–1950°C and the addition of silicon and aluminum for deoxidation. This method offered reduced LC-FeCr consumption and shorter processing times. However, the high-temperature operation leads to the destruction of EAF refractory bricks. Major breakthroughs occurred with vacuum oxygen decarburization (VOD) in the late 1950s [3] and argon–oxygen decarburization (AOD) in 1954 [4], both enabling decarburization with minimal chromium loss. These innovations laid the groundwork for advanced processes like KCB-S, K-BOP, and K-OBM-S [5].
The widely used technology for stainless steel production is EAF–AOD, which is also known as the duplex process. This method utilizes raw materials, such as ferronickel (FeNi), ferrochrome (FeCr), and Fe-scrap. Since 2006, nickel pig iron (NPI), which has a nickel content of 3wt%–12wt%, has been widely used [6]. Two main technologies produce FeNi and NPI from nickel saprolite ore: rotary kiln–electric furnace (RK–EF) and blast furnace. Currently, the RK–EF route dominates global FeNi and NPI production, accounting for up to 95% of worldwide output.
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Abrar Taimullah, Izzul Islam, Dale Tandersen, Ulil Amri Nizhamul, Taufiq Hidayat, Yerbolat Makhambetov, Yopi Hendrawan, Zulfiadi Zulhan (2025). Direct and sustainable stainless steelmaking from nickel and chromite ores by hydrogen plasma smelting reduction. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-024-3068-4
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Frequently Asked Questions
What is hydrogen plasma smelting reduction?
Hydrogen plasma smelting reduction is a novel single-step process that uses hydrogen plasma to reduce metal oxides directly from ores, producing metals without fossil-based carbon reductants, thereby minimizing CO2 emissions.
How does this method reduce CO2 emissions in stainless steel production?
By replacing carbon-based reductants with hydrogen, the process eliminates CO2 emissions from reduction reactions. Additionally, it bypasses energy-intensive steps like AOD and VOD converters, further reducing the carbon footprint.
What are the optimal ore proportions for producing AISI 300 stainless steel?
A briquette containing 30wt% chromite ore and 70wt% calcined nickel ore yields the best results, achieving Fe, Cr, Ni, and Si contents of 62.95wt%, 19.37wt%, 11.83wt%, and 0.72wt% after 180 seconds of hydrogen plasma exposure.
How fast is the reduction process?
The reduction is ultrafast: NiO is fully converted to Ni within 60 seconds, and FeO is nearly fully converted to Fe within 120 seconds, enabling stainless steel production in as little as 120 seconds.
What is the significance of eliminating AOD and VOD converters?
AOD and VOD converters are traditionally required for decarburization in stainless steelmaking. Eliminating them simplifies the process, reduces energy consumption, and lowers capital and operational costs, making production more sustainable and efficient.
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