Ferrosilicon: A ternary functional material for metallurgical purification and alloy strengthening

I. Core Definition of Ferrosilicon Magnesium (Fe) Ferrosilicon magnesium (Fe) is a ternary composite alloy formed by silicon (Si), magnesium (Mg), and iron (Fe). Silicon and magnesium are the main functional elements, with iron as the matrix component. Typical compositions include 40%–70% silicon, 5%–15% magnesium, and 10%–30% iron. It is a highly efficient composite deoxidizer, desulfurizer, and grain refiner in the metallurgical industry. Its core value lies in the synergistic effect of the stability of silicon and the strong reactivity of magnesium. This allows for the deep purification of steel materials and enhances their mechanical properties through alloying. Furthermore, its lightweight characteristics enable diverse applications in high-end casting, new energy, and other fields, making it a key material connecting traditional metallurgy and lightweight manufacturing. II. Development History The industrial production of ferrosilicon (Mg) began in the 1960s. With breakthroughs in the silicothermic magnesium metallurgical technology (95% of the world's primary magnesium is produced via this process), Europe and the United States achieved large-scale smelting of ternary alloys for the first time. Initially, it was mainly used for quality optimization of special military castings, solving the problem of single alloying agents being unable to simultaneously achieve purification and strengthening. In the 1980s and 1990s, the global automotive industry's demand for lightweighting surged, leading to the rapid expansion of Mg's application in aluminum alloys and ductile iron. Production processes were upgraded from open electric furnaces to closed submerged arc furnaces, significantly improving capacity and product stability. China, leveraging its dolomite resource advantage (accounting for 80% of global primary magnesium production), gradually became a major producer. Since the 21st century, the "dual-carbon" strategy and high-end manufacturing upgrades have driven industry transformation, accelerating the research and development of high-purity Mg and low-impurity products. The silicothermic high-purity magnesium production technology developed by the Xi'an Jiaotong University team has propelled Mg's application into high-end fields such as new energy hydrogen storage and aerospace, continuously enhancing its strategic importance. III. Core Characteristics Analysis

(I) Metallurgical Core Characteristics

The core advantage of ferrosilicon lies in the synergistic effect of the three elements: Magnesium has extremely strong deoxidation ability (superior to silicon and aluminum), and can form low-melting-point (1107℃) magnesium oxide (MgO) with oxygen in molten steel, which is easy to float and separate, and the deoxidation efficiency is more than 30% higher than that of ferrosilicon alone; Silicon can work with magnesium to desulfurize, forming stable magnesium sulfide (MgS), with a desulfurization rate of 75%~85%, effectively avoiding hot brittleness defects; At the same time, the iron phase, as the matrix, can refine the alloy grains and improve the morphology of inclusions. In Al-Mg-Si alloys, an appropriate amount of iron-rich phase can increase the yield strength by more than 20% while ensuring that the elongation remains unchanged, achieving the triple effect of "purification-strengthening-refinement". (II) Physical and Chemical Properties Ferro-SiMn appears as a silvery-gray metallic block. Its surface is easily oxidized to form a light gray, dense oxide film. Its density varies with composition, ranging from 3.8 to 4.5 g/cm³, and its melting point ranges from 1200 to 1380℃ (the higher the magnesium content, the lower the melting point). It is chemically reactive, easily absorbing moisture and oxidizing at room temperature, requiring sealed storage. Magnesium evaporates significantly at high temperatures, necessitating temperature and pressure control during smelting to manage losses. It exhibits good compatibility with molten steel, does not react harmfully with beneficial elements such as manganese and chromium, and has wide applicability. (III) Process Adaptability Ferro-SiMn dissolves uniformly in molten steel and can be added through various methods such as in-flow addition, injection, and wire feeding, making it suitable for various smelting processes including converters, electric furnaces, and continuous casting. Precise matching of different component ratios to meet specific needs: High-magnesium ferrosilicon (Mg≥12%) is suitable for deep purification of special steels; medium-magnesium ferrosilicon (Mg8%~12%) is widely used in the production of automotive steels; and low-magnesium ferrosilicon (Mg5%~8%) is suitable for the modification needs arising in the casting field. IV. Mainstream Production Processes

(I) Electric Arc Furnace Silicon Thermal Reduction Method (Mainstream Process)

This is currently the core process for global ferrosilicon production. It uses silica (quartz sand), dolomite (providing the magnesium source), and iron scale as raw materials, and ferrosilicon and coke as reducing agents. These are mixed in proportion and then charged into a 25000~33000kVA closed submerged arc furnace. High temperatures (furnace temperature 1800~2000℃) are generated by an electric arc, causing the magnesium oxide in the dolomite to be reduced to magnesium by silicon, while simultaneously combining with silicon and iron to form an alloy. The molten alloy is discharged through the taphole, cast into ingots, cooled, and then crushed and screened to a target particle size of 10~50mm. This process has concentrated production capacity and mature technology, but the traditional process consumes approximately 8800~9800 kWh of electricity per ton of product, and the magnesium volatilization loss rate reaches 15%~20%. (II) Process Technology Upgrade Direction With the upgrading of environmental protection and "dual carbon" requirements, the industry is accelerating process innovation: First, green electricity coupled smelting, enterprises in Inner Mongolia, Liaoning and other places have introduced wind and solar green electricity, saving 600~700 yuan in electricity costs per ton of product and reducing carbon emissions by more than 70%; Second, purification technology optimization, adopting "heat-resistant gradient condensation, temperature and pressure dual control" technology to reduce impurity content and produce high-purity silicon magnesium iron (total impurities < 0.5%); Third, intelligent equipment transformation, equipped with intelligent batching and waste heat recovery systems, improving energy efficiency by 12%~18%; Fourth, new reduction processes, the carbothermic reduction-vacuum refining composite process is in the pilot stage, which can reduce the magnesium loss rate to below 10%. (III) Product Form Optimization To improve efficiency, the industry has introduced specialized product forms: ferrosilicon magnesium powder (particle size < 1mm) is adapted to the blowing process, allowing for precise control of the addition amount; ferrosilicon magnesium wire (diameter 12~14mm) is used for continuous casting wire feeding to reduce magnesium volatilization; composite alloys such as ferrosilicon barium and ferrosilicon manganese further expand functional scenarios and meet diverse smelting needs. V. Core Application Areas (I) Steel Industry (Traditional Core Area) Globally, over 70% of ferrosilicon magnesium is used in steel production, serving as a key modifier for special steels and high-strength steels. In the production of high-strength steel for automobiles and steel for engineering machinery, adding 0.3%~0.6% ferrosilicon can reduce the oxygen content in the steel to below 25ppm and the sulfur content to below 15ppm, increasing the yield strength by 20%~30%. In stainless steel production, its desulfurization effect can prevent hot brittleness during high-temperature processing, increasing the pass rate by 10%~15%. In bearing steel and spring steel, its grain refinement effect can extend the fatigue life of the material. (II) Casting Field (Important Application Scenarios) Ferrosilicon is a high-quality inoculant and modifier for ductile iron and gray cast iron. After addition, it can refine the graphite structure, reduce the tendency of white cast iron, and improve the mechanical strength and wear resistance of castings. It is widely used in the production of castings such as automobile engine cylinder blocks, crankshafts, and machine tool beds, especially suitable for high-strength lightweight castings, which can reduce the scrap rate by 12%~18%. Casting enterprises in magnesium-rich areas such as Chaoyang, Liaoning Province, have already achieved large-scale application. In aluminum alloy casting, the iron-rich phase can optimize the alloy microstructure and improve impact resistance. (III) Emerging High-end Fields (Growth Pole) In the new energy field, high-purity silicon-magnesium-iron can be used for the preparation of hydrogen storage materials (magnesium is a high-quality hydrogen storage carrier) and the performance adjustment of vanadium redox flow battery electrode materials; in the aerospace field, it is adapted to the smelting needs of ultra-high strength aluminum alloys and used to manufacture aircraft parts to achieve structural lightweighting; in the chemical field, as a catalyst carrier for organic synthesis reactions, its high specific surface area and chemical stability can be used to improve catalytic efficiency; in the medical materials field, the biocompatibility of magnesium-based alloys makes them show application potential in implant materials. VI. Market Development Trends (I) Steady Growth in Demand, with a Shift Towards High-end Development In 2024, China's silicon-magnesium-iron production capacity was approximately 900,000 tons, with a market size exceeding 8 billion yuan. It is expected that the average annual compound growth rate will remain at 5.5%~6.8% over the next five years. Among them, the demand for high-purity silicon-magnesium iron (Si≥65%, Mg≥10%, total impurities <0.5%) is growing the fastest, with its share increasing from 9.2% in 2024 to over 20% in 2029. Currently, the domestic supply-demand gap is 12,000 tons, with an import dependency of about 22%, mainly relying on imports from Russia and Germany. New energy hydrogen storage and automotive lightweighting are becoming the core driving forces for demand. (II) Optimization of production capacity structure, and intensified regional and enterprise differentiation Global silicon-magnesium iron production capacity is mainly concentrated in China (accounting for over 60%), Russia, the United States, and other countries. Domestic production capacity is mainly distributed in Liaoning (rich in dolomite resources), Inner Mongolia, and Ningxia. Affected by the dual control policies of ecological red lines and energy consumption, the production capacity share of traditional production areas will decrease from 68% to 50% in 2029. Xinjiang, Qinghai, and other regions will take over the incremental production capacity by virtue of their green electricity advantages, forming a layout of "smelting moving westward and deep processing moving eastward". Industry concentration continues to increase, with the top ten companies accounting for 48.3% of the total capacity. Leading companies such as Liaoning Chaoyang Xinmei and Baogang Group have built competitive barriers through resource integration and high-purity technology upgrades, while small and medium-sized enterprises are focusing on niche casting fields or transforming into composite alloy production. (III) Green and low-carbon driven, technological innovation becomes key. The "dual-carbon" strategy promotes the industry's low-carbon transformation, with green electricity smelting and energy efficiency improvement becoming the core directions. The policy requires that all production capacity that does not meet the energy efficiency benchmark (electricity consumption per ton of product ≤ 8500 kWh) be phased out by 2025, forcing companies to increase investment in technological transformation. The adoption rate of intelligent batching and waste heat recovery technologies is expected to increase from 32% in 2024 to 55% in 2027. In the medium to long term, the promotion of high-purity technologies such as "impurity-containing gasification and gradient condensation" by Xi'an Jiaotong University, as well as the research and development of hydrogen-based carbon-free reduction processes, will reshape the industry landscape, and the research and development of high-purity, low-loss products will become the core competitiveness of enterprises. (IV) Price Fluctuations and Strategic Layout The price of ferromagnesia is affected by multiple factors: fluctuations in the prices of upstream raw materials such as silica (average price of RMB 385/ton in 2024), dolomite (average price of RMB 260/ton, an increase of 9.8%), and coke directly affect production costs; downstream factors such as the operating rate of the automotive industry, demand for high-end casting, and new energy policy guidance influence the demand side; while green electricity policies and environmental standards affect supply elasticity. Due to its key role in lightweight manufacturing and the new energy industry chain, ferromagnesia has been included in the key mineral supply chain management of many countries, and enterprises are strengthening their reserves of dolomite and silica resources and aligning with green electricity to ensure the security of the industry chain.