I. Product Definition and Core Components
    Definition:

     Calcium-iron cored wire (CaFe Cored Wire) is a specialized wire feeding material for steel refining in the metallurgical industry. It is a cylindrical wire produced by mixing metallic calcium granules and iron powder in a specific ratio as the core material, with cold-rolled low-carbon steel strip as the outer sheath, through a cladding rolling process. Its core applications include deoxidation, desulfurization, and inclusion modification in steelmaking and ladle refining processes. It is the preferred material for calcium treatment of pure steel grades such as low-carbon steel, ultra-low-carbon steel, and low-silicon steel.

    Core Components:

    Core Material: Composed of 25%-35% calcium granules and 65%-75% iron powder (common grades include Ca30 and Ca40, corresponding to approximately 30% and 40% calcium content, respectively). Calcium granules ensure deoxidation and desulfurization activity, while iron powder increases weight, slows calcium evaporation, and improves calcium utilization.

Outer Sheath: Cold-rolled low-carbon steel strip, 0.4±0.2mm thick, providing good coverage to prevent oxidation and moisture absorption of the core material, ensuring stable cracking and core material release during molten steel feeding.

Mixing Characteristics: The ratio of iron powder to calcium granules in the core material is precisely designed to avoid high-temperature vaporization and loss of pure calcium due to its low density (1.55g/cm³) and low melting point (839℃), while also allowing for more uniform dispersion of calcium in the molten steel through the matrix effect of iron powder.

    II. Core Specifications

    III. Core Advantages
    Calcium Utilization and Cost Balance Advantage:Compared to pure calcium wire (calcium yield of only 5%-8%), iron powder in calcium-iron cored wire slows down calcium evaporation and burn-off, increasing calcium yield to 8%-15%. Simultaneously, iron powder replaces some metallic calcium, reducing the consumption of precious calcium resources and lowering refining costs by 10%-15%, balancing efficiency and economy.

    Smelting Stability and Safety Advantage: Avoids the violent splashing of molten steel caused by calcium vapor during pure calcium wire feeding, reducing electrode wear and refining furnace lining erosion, extending equipment life by over 30%. Furthermore, the wire feeding process is stable, with molten steel temperature drop ≤8℃/min, far lower than the powder injection method (15-20℃/min), ensuring stable smelting processes.

    Advantages in composition control and yield: Precise control of the feeding speed (typically 2-5 m/s) and feed rate via the wire feeder allows for fine-tuning of the steel composition, increasing the recovery rate of metals and rare earth elements by 5%-10%, and reducing the composition fluctuation range to ±0.02%, meeting the stringent requirements for composition precision in high-end steel grades.

    Environmental and operational advantages: The wire feeding process is well-sealed, with no dust emission or harmful gas emissions, meeting green metallurgy requirements; equipment investment is only 60% of that of the powder injection method, and operation is simple, requiring only 1-2 people per station, reducing labor costs.

    IV. Core Metallurgical Functions
    High-Efficiency Deoxidation: Calcium has a much higher affinity for oxygen than aluminum and manganese (at 25℃, the free energy of formation of Ca-O is -604kJ/mol, and that of Al-O is -1582kJ/mol), rapidly reacting in molten steel to form CaO. It can also combine with Al₂O₃ to form low-melting-point (1200-1400℃) calcium aluminates, which easily float and are discharged. According to industry data, when the oxygen content of the molten steel is controlled to ≤80×10⁻⁶ before wire feeding, the deoxidation rate can reach 31.1%-60%, and the final oxygen content of the molten steel can be reduced to below 20×10⁻⁶.

    Deep desulfurization: Calcium has a strong affinity for sulfur, forming high-melting-point (2450℃) CaS. The solubility of CaS in molten steel at 1500℃ is only 0.0015%, achieving a desulfurization efficiency of 30%-50%. Especially in the smelting of ultra-low sulfur steel, combined with top slag treatment, the sulfur content in the steel can be stably controlled below 5×10⁻⁶, and sulfur reversion is less likely.

    Inclusion modification: By increasing the effective calcium content in the steel, long, brittle MnS inclusions are transformed into fine (≤5μm) uniformly dispersed CaS or CaS-MnS composite phases. Simultaneously, Al₂O₃ cluster inclusions are modified into spherical calcium aluminates, improving the anisotropy of the steel, increasing impact toughness by 20%-30%, and extending fatigue life by more than 30%.

    Improved casting playability: Modified inclusions are easier to float and remove, reducing the probability of nozzle blockage (from 30% in the powder injection method to below 5%), increasing continuous casting speed by 10%-15%, avoiding casting interruption accidents caused by nozzle nodules, and improving production efficiency.

    V. Application Scenarios

    Main application steel grades: Low-carbon steel, ultra-low-carbon steel (such as IF steel), low-silicon steel, high-strength rebar (HRB400 and above), bearing steel, pipeline steel, etc., especially suitable for the production of pure steel with strict requirements on the morphology, quantity, and compositional precision of inclusions.

    Key smelting processes: Ladle refining (LF furnace, RH furnace), calcium treatment before continuous casting; can be used in conjunction with calcium-silicon cored wire and aluminum cored wire to achieve a complete refining process of "deoxidation-desulfurization-inclusion modification"; it can also be used for the pretreatment of molten iron and ductile iron to improve casting performance.

    Industry application trends: As the steel industry develops towards high-end and green technologies, the proportion of low-sulfur steel and clean steel production will increase from 35% in 2020 to 50% in 2025. The market demand for calcium-iron cored wire is expected to grow at an average annual rate of 8%-10%, becoming a key auxiliary material for steel mills to enhance product competitiveness.

    VI. Precautions for Use

    Wire Feeding Process Control: Argon gas stirring is required (stirring intensity 0.5-1.0 m³/(min・t)) to ensure sufficient contact and reaction between the core material and molten steel. The wire feeding depth should reach at least 2/3 of the molten steel height to prevent premature melting of the core material in the slag layer, which would affect calcium utilization.

    Calcium Addition Control: The amount of wire fed should be calculated based on the initial sulfur content ([S]₀) of the molten steel. Typically, the calcium addition per ton of steel is 0.2-0.5 kg. Excessive calcium addition can easily generate large-sized CaO inclusions, negatively impacting steel quality. Real-time adjustments via online composition monitoring are necessary.

    Storage and Transportation: Store in a dry, well-ventilated warehouse to prevent moisture absorption and oxidation of the core material (calcium readily reacts with water to form Ca(OH)₂, reducing its activity). Avoid violent collisions during transportation to prevent damage to the steel strip and leakage of core powder.