Alloy core wire: a functional material morphology achieved through precise metallurgical control and efficient modification

I. Core Definition of Alloy Core Wire Alloy core wire is a composite functional metallurgical material consisting of a core material and an outer sheath. It uses various ferroalloys (such as ferrotitanium, calcium silicon, ferrosilicon barium, ferrosilicon nitride, etc.), pure metals, or composite powders as the core material, and low-carbon steel strip as the outer sheath. It is a continuous wire typically 10-16mm in diameter, produced through coating and drawing processes. Its core value lies in the precise feeding method, which allows for the deep insertion of alloying elements into molten steel/iron, achieving efficient utilization of alloying elements and precise control of the metallurgical process. It boasts four major advantages: precise composition control, reduced losses, convenient operation, and environmental friendliness. Suitable for high-end steel smelting, precision casting, and other applications, it has become a key processing method connecting ferroalloy raw materials and end materials. II. Development History The industrial application of alloy core wire began in the 1980s. With the popularization of continuous casting technology and the increasing requirements for compositional uniformity in high-end steel, Germany and Japan took the lead in developing wire feeding processes and alloy core wire products. Initially, these were mainly used for precise control of alloying in military special steels, solving the pain points of traditional block alloy addition, such as "large element loss, large compositional fluctuations, and difficulty in floating inclusions." In the 1990s, China's steel industry developed rapidly, and the localization of alloy core wire accelerated. A series of products, such as titanium-iron core wire, silicon-calcium core wire, and rare earth silicon-magnesium core wire, were successively developed. The production process was upgraded from manual coating to automated continuous production lines, significantly improving production capacity and product stability. Since the beginning of the 21st century, the "dual carbon" strategy and the upgrading of high-end manufacturing have driven the transformation of the industry. The research and development of ultra-fine core wire, composite core wire and high-purity core wire has accelerated, and their application in fields such as nuclear power steel and high-strength steel for new energy equipment has continued to expand. At the same time, the intelligent upgrading of wire feeding equipment (such as online flow control and real-time composition monitoring) has made alloy core wire the core carrier for greening and precision in the metallurgical process. III. Core Characteristics Analysis

(I) Metallurgical Core Characteristics

The core advantage of alloy core wire lies in precise control and efficient utilization: the core wire is fed into the deep part of the molten liquid (1~3m from the liquid surface) by a wire feeder. After the outer sheath melts, the core material slowly dissolves, avoiding element oxidation and burning at the liquid surface. The element recovery rate is 30%~50% higher than that of traditional block addition (e.g., the titanium recovery rate of titanium-iron core wire reaches 85%~95%, far exceeding the 60%~70% of block addition); the core material composition can be precisely customized, and single-element or multi-element synergistic addition can be achieved (e.g., silicon-calcium-barium composite core wire), meeting the multiple requirements of steel for "deoxidation - desulfurization - grain refinement - inclusion modification"; at the same time, the core material dissolves uniformly, which can avoid local component segregation and reduce the fluctuation range of steel mechanical properties by more than 40%. (II) Physical and Structural Characteristics The alloy core wire appears as a continuous wire covered with a silver-gray steel strip. It has a smooth, crack-free surface, a core material density ≥95%, and excellent bending performance (bending radius ≥500mm without breakage), facilitating reel storage and automated feeding. Depending on the core material morphology, it can be divided into powdered core wire (e.g., calcium silicate powdered core wire), granular core wire (e.g., silicon nitride iron granular core wire), and filamentous core wire (e.g., pure titanium wire). The density varies between 6.0 and 7.8 g/cm³ depending on the core material, adapting to different melt depths and reaction requirements. It exhibits good chemical stability. At room temperature, the core material is sealed by the steel strip, preventing oxidation and moisture absorption, extending the shelf life by 3-5 times compared to exposed iron alloys. (III) Process Adaptability Characteristics Alloy core wires are compatible with various metallurgical equipment such as converters, electric furnaces, and continuous casting machines. Multi-element alloying can be achieved through single-feed or multi-feed combinations. The feeding speed (1~10m/s) and feeding depth can be precisely controlled to meet the production needs of different steel grades (such as stainless steel, bearing steel, and high-strength steel) and castings (such as automobile cylinder blocks and machine tool beds). Different core material combinations are precisely matched to various scenarios: titanium-iron core wires are used for carbon fixation and corrosion protection of stainless steel; silicon-calcium core wires are used for deep deoxidation of special steels; rare earth magnesium core wires are used for spheroidizing treatment of ductile iron; and composite core wires (such as silicon-calcium-barium-titanium core wires) are used for one-stop metallurgical modification. IV. Mainstream Production Process

(I) Core Production Flow (Mainstream Process)
The core process of alloy core wire production is "core material preparation - steel strip coating - continuous drawing - finished product inspection": 1) Core material pretreatment: The ferroalloy is crushed to a specific particle size (powder ≤ 0.15 mm, granular 1~3 mm), dried and cleaned (moisture ≤ 0.5%), and the composite core material needs to be uniformly mixed in proportion; 2) Steel strip coating: 0.3~0.8 mm thick low carbon steel strip (C ≤ 0.1%) is used, rolled into a U-shaped groove by a forming machine, filled with core material, and then rolled into a circular cross section by closed rollers; 3) Continuous drawing: The coated thick wire is drawn to the target diameter (10~16 mm) by a multi-pass drawing machine, while improving the core material density and wire roundness; 4) Finished product processing: The diameter deviation (±0.3 mm) and core material filling uniformity are detected online, and qualified products are packaged in coils (weight per coil). (500~1000kg). This process is highly automated, and a single production line can reach a capacity of 5000~15000 tons/year. (II) Process Technology Upgrade Direction With the upgrading of high-end manufacturing and environmental protection requirements, the industry is accelerating process innovation: First, core material precision, developing high-purity core materials (total impurities < 0.3%) and ultra-fine composite core materials (particle size ≤ 0.075mm) to meet the needs of aerospace steel; Second, coating technology optimization, using laser welding sealing instead of mechanical pressing to avoid core material oxidation and extend shelf life; Third, intelligent production, introducing online weighing, X-ray flaw detection and other detection technologies, controlling the core material filling uniformity error within ±2%; Fourth, green transformation, using green electric drive drawing equipment, increasing the steel strip waste heat recovery utilization rate to 60%, and reducing energy consumption per ton of product by 15%~20%. (III) Typical Product Classification and Specifications Based on core material function, products are divided into four main categories: 1) Deoxidation and desulfurization (silicon-calcium core wire, silicon-barium core wire, aluminum-calcium core wire), primarily used for deep purification of molten steel; 2) Alloying (titanium-iron core wire, vanadium-iron core wire, niobium-iron core wire), used for precise control of alloy element content in steel; 3) Spheroidizing and inoculating (rare earth magnesium core wire, silicon-magnesium-calcium core wire), suitable for ductile iron production in the casting industry; 4) Inclusion modification (silicon-calcium-barium-titanium composite core wire, silicon-nitride iron core wire), used for optimizing inclusion morphology in high-end steel. In terms of specifications, in addition to conventional 13-16mm diameter wires, ultra-fine core wires (6-8mm diameter) are developed for small casting production, and large-diameter core wires (18-20mm diameter) are used for large electric arc furnace steelmaking. V. Core Application Areas

(I) Steel Industry (Traditional Core Area)
Over 85% of alloy core wires worldwide are used in steel production, making them a key material for high-end steel smelting. In stainless steel production, titanium-iron core wire and niobium-iron core wire allow for precise control of titanium and niobium content, preventing intergranular corrosion and improving corrosion resistance by over 30%, making them widely used in chemical equipment, medical devices, and other applications. In high-strength structural steel (such as bridge steel and wind power steel) production, silicon-calcium-barium composite core wire achieves a one-stop process of "deoxidation-desulfurization-inclusion modification," increasing the steel's yield strength to over 690MPa and optimizing welding performance by 40%. In bearing steel and spring steel production, vanadium-iron core wire and silicon nitride-iron core wire precisely add alloying elements, extending material fatigue life by 50%~80%. In continuous casting billet production, the wire feeding process reduces subcutaneous porosity and inclusion defects, increasing the billet qualification rate by 10%~15%. (II) Casting Field (Important Application Scenarios) Alloy core wire is a high-quality modified material for precision casting, especially suitable for the production of ductile iron and vermicular graphite cast iron. In the production of castings such as automobile engine blocks and crankshafts, rare earth magnesium core wire and silicon-calcium-magnesium core wire are used as spheroidizing agents and inoculants, increasing the spheroidization rate to over 95%, improving the mechanical strength of castings by 25%, and reducing the scrap rate by 20%~28%. In the production of engineering machinery castings (such as excavator bucket teeth and hydraulic pump bodies), silicon-barium iron core wire and titanium-iron core wire improve the morphology of inclusions in castings and enhance wear resistance and impact resistance. In the production of large castings (such as machine tool beds and wind turbine hubs), composite core wire can precisely control the uniformity of composition, avoiding casting deformation and cracking. (III) Emerging High-End Fields (Growth Engines) In the aerospace field, high-purity titanium iron core wire and niobium iron core wire are used in the smelting of ultra-high strength steel (such as 300M steel) and titanium alloys, precisely controlling the content of alloying elements to achieve a balance between lightweight and high strength, suitable for the production of aircraft landing gear and rocket engine casings; in the nuclear power field, boron iron core wire and zirconium iron core wire are used in the alloying treatment of steel for nuclear reactors to improve the radiation resistance and high-temperature stability of materials; in the new energy field, vanadium iron core wire and silicon-calcium core wire are used in the production of steel for vanadium redox flow batteries and high-strength steel for wind power flanges to ensure the long-term service stability of equipment; in the 3D printing field, ultra-fine alloy core wire (diameter ≤0.8mm) can be used as a supplementary form of metal powder raw materials, suitable for additive manufacturing of large components. VI. Market Development Trends

(I) Rapid Demand Growth and Significant Gap in High-End Products
In 2024, China's alloy core wire production capacity was approximately 3.2 million tons, with a market size exceeding 28 billion yuan. The compound annual growth rate is projected to remain between 8.2% and 9.8% over the next five years, exceeding the overall growth rate of the ferroalloy industry. High-purity composite core wire (total impurities in the core material < 0.3%, compositional uniformity error ±1%) is expected to see the fastest demand growth, increasing its share from 16.8% in 2024 to over 30% in 2029. Currently, the domestic supply-demand gap is 85,000 tons, with an import dependency of approximately 28%, primarily relying on imports from Germany and Japan. High-end stainless steel, aerospace, and new energy equipment are the core drivers of demand. (II) Optimized Production Capacity Structure and Coordinated Regional Layout Global alloy core wire production capacity is mainly concentrated in China (accounting for over 72%), Germany, Japan, Russia, and other countries. Domestic production capacity is mainly distributed in Hebei (supporting steel industry clusters), Shandong, Jiangsu, and Sichuan (coordinated titanium ore and ferroalloy production capacity). Influenced by environmental policies and the demand for supply chain coordination, production capacity is gradually concentrating in steel bases and ferroalloy production areas, forming an integrated layout of "ferroalloy raw materials - core wire processing - steel production". Industry concentration continues to increase, with the top ten companies accounting for 62.5% of the production capacity. Leading companies such as Hebei Jinxi, Shandong Jiuyang, and Sichuan Panzhihua Iron and Steel have built competitive barriers through supply chain integration and high-end product R&D, while small and medium-sized enterprises focus on single-function core wires or regional markets. (III) Green and Low-Carbon Driven, Technological Innovation Becomes the Core Barrier The "dual-carbon" strategy promotes the industry's low-carbon transformation, with green electricity production and energy-saving processes becoming the core directions. The policy requires all production capacity that fails to meet energy efficiency benchmarks (comprehensive energy consumption per ton of product ≤ 0.3 tons of standard coal) to be phased out by 2025, forcing companies to increase investment in technological upgrades. The adoption rate of intelligent testing and waste heat recovery technologies is expected to increase from 42% in 2024 to 65% in 2027. In the medium to long term, the research and application of high-purity core material preparation technology, precise proportioning technology for composite core wires, and intelligent wire feeding coordination technology will reshape the industry landscape, and "one-stop metallurgical solutions" (core wire + wire feeding equipment + process services) will become the core of corporate competitiveness. (IV) Price Fluctuations and Strategic Layout Alloy core wire prices are influenced by multiple factors: fluctuations in upstream core material prices (such as titanium ore, ferrovanadium, and low-carbon steel strip) directly affect costs (core materials account for 70%~80% of total costs). In 2024, the average price of low-carbon steel strip increased by 12.3%, and the average price of ferrovanadium increased by 16.4%, driving synchronous fluctuations in core wire prices. Downstream factors such as the operating rate of the steel industry, demand for high-end casting, and policy guidance for new energy equipment influence demand. Environmental standards and green electricity policies affect supply elasticity. Due to its irreplaceable role in high-end metallurgical processes, alloy core wire has become a key link in the upgrading of the steel industry chain. Enterprises are strengthening their core material resource binding (such as jointly building production capacity with ferroalloy enterprises), green electricity layout, and high-end product research and development to narrow the quality gap with imported products and ensure the security of the industry chain.