What’s the Facts of Tungsten ?（II）
Chapter 14 Production and Application of Ferrotungsten
This chapter focuses on the production process and application of ferrotungsten (FeW), and comprehensively explains its preparation method, physical and chemical properties, and its wide range of uses in the steel industry, casting, military industry, etc. The content includes an overview of ferrotungsten, production process, production conditions in various countries, specific application scenarios and quality standards, and especially lists the ferrotungsten standards of China and other countries in detail.
14.1 Overview of Ferrotungsten
Ferrotungsten is an iron alloy with tungsten and iron as the main components, usually prepared by smelting tungsten ore or tungsten compounds and iron raw materials. As an important alloying additive in the steel industry, ferrotungsten is widely used due to its high density, high melting point and excellent mechanical properties. Its tungsten content is usually between 70% and 85% (in terms of WO ₃ ), and the rest is iron and a small amount of impurities (such as carbon, silicon, phosphorus, etc.).
Physical and chemical properties of tungsten iron
Appearance: Gray-black metal block or granular material, the surface gloss varies with processing conditions.
Melting point: about 1650°C-2100°C (increases with increasing tungsten content, the melting point of FeW80 is close to 2100°C).
Density: 14.5-17.5 g/cm³ ( FeW70 is about 15 g/ cm³ , FeW80 is close to 17 g/cm³ ) .
Hardness: Mohs hardness 6.5-7.5, compressive strength 1000-1500 MPa, tensile strength about 600-800 MPa.
Thermal conductivity: About 50-70 W/(m·K), between pure tungsten (173 W/(m·K)) and ordinary steel (~45 W/(m·K)).
Electrical conductivity: About 5-8×10 ⁶ S/m, lower than pure tungsten but higher than ordinary iron-based alloys.
Crystal structure: body-centered cubic structure (bcc), solid solution or compound phase composed of tungsten phase (W) and iron phase (Fe) (such as Fe₃W₂ ) .
Chemical stability: Insoluble in water, resistant to acid and alkali corrosion (except strong oxidizing acids such as concentrated nitric acid), oxidized to form WO ₃ and Fe ₂ O ₃ in high temperature (>800°C) air .
Characteristics of tungsten iron
High density and high melting point make it suitable for high temperature and high load environments.
Excellent wear resistance, corrosion resistance and oxidation resistance, suitable for harsh working conditions.
It has good compatibility with iron-based materials and can significantly improve the performance of steel as an additive.
14.2 Production Process of Ferrotungsten
The production of ferrotungsten mainly adopts pyrometallurgical process, which uses tungsten concentrate (such as wolframite or scheelite) as raw material and combines it with iron raw material (such as scrap steel or iron powder) to smelt it at high temperature. The following is a detailed description of the main production methods:
14.2.1 Thermite Process
Process principle
WO₃ in the tungsten concentrate is reduced to metallic tungsten through a strong exothermic reaction and fused with iron to form tungsten-iron alloy. The reaction equation is as follows:
3WO3 +2Al+Fe→FeW+Al2O3+ heat 3WO₃ + 2Al + Fe → FeW + Al₂O₃ + heat 3WO3 + 2Al+Fe→FeW+Al2 O3 + heat
Process
Raw material preparation: Tungsten concentrate (WO₃ content >65%) is mixed with iron powder and aluminum powder in proportion (usually W:Al:Fe=1:0.5:0.3), and flux (such as CaF₂, about 5%-10%) is added to lower the melting point and promote slag-liquid separation.
Charging and ignition: The mixture is loaded into a refractory crucible (such as magnesium oxide or graphite crucible) and ignited with a magnesium rod to initiate the reaction, with the temperature rising instantly to over 2500°C.
Smelting and separation: The reaction takes about 5-10 minutes to complete. The molten ferrotungsten (high density) sinks to the bottom, and the slag layer (Al ₂ O ₃ , density about 3.9 g/cm ³ ) floats on the top. After cooling, it is broken and separated.
Refining and molding: Remove residual slag and cast into 10-100 mm blocks or crush into particles.
Advantages: Simple equipment, fast response speed, low energy consumption, suitable for small and medium-scale production.
Disadvantages: Impurities (such as Si, Mn) are difficult to control accurately, the tungsten recovery rate is low (85%-90%), and the product quality fluctuates greatly.
14.2.2 Electric Furnace Process
Process principle
In an electric arc furnace or induction furnace, electric energy is used to heat the tungsten concentrate and iron raw materials for smelting and reduction. Carbon (such as coke) or silicon (such as ferrosilicon) is often used as a reducing agent. Reaction example:
WO3+3C+Fe→FeW+3CO↑WO ₃ + 3C + Fe → FeW + 3CO↑ WO3 + 3C+Fe→FeW+3CO↑
Process
Raw material preparation: Tungsten concentrate (WO₃ content >60%) is mixed with scrap steel, coke (C content>85%) or ferrosilicon (Si content>70%) in proportion (W:Fe:C=1:0.2:0.15) to ensure that the tungsten content meets the standard.
Electric furnace smelting: Melting at 2000°C-2200°C, the electric arc furnace power is usually 5-10 MW, continuous stirring (mechanical or electromagnetic) to homogenize the composition, reaction time 2-4 hours.
Furnace-out and casting: The molten ferrotungsten is taken out of the furnace and cast into ingots (50-200 kg/block) or blocks, and then crushed to the required particle size after cooling.
Refining: It can be further purified by blowing oxygen (reducing the C content to <0.2%) or vacuum degassing (removing S and P).
Advantages: Stable product quality, precise control of tungsten content (70%-85%), high recovery rate (>95%), suitable for large-scale production.
Disadvantages: High energy consumption (about 5000-7000 kWh per ton), high equipment investment and maintenance costs.
14.2.3 Other methods
Carbothermal reduction
Using carbon to reduce tungsten concentrate under vacuum or inert atmosphere (such as Ar) at a temperature of 1800°C-2000°C is suitable for high-purity ferrotungsten (C<0.1%), but the process is complicated and costly.
Silicon thermal method
Using ferrosilicon as the reducing agent, the reaction temperature is about 1800°C, and low-carbon ferrotungsten (C<0.3%) is produced. The reaction is mild but the silicon content needs to be strictly controlled (Si<0.8%).
Production precautions
Impurity control: Sulfur (S<0.1%), phosphorus (P<0.05%), and carbon (C<0.5%) need to be controlled through raw material selection and refining to avoid affecting the quality of steel.
Particle size specification: usually 10-50 mm or 50-100 mm, which is convenient for transportation and smelting.
protection measures: Waste gases (such as CO, SO₂ ) need to be equipped with bag filters and desulfurization devices, and waste slag (Al₂O₃ or SiO₂ ) can be recycled for building materials.
14.3 Production of Ferrotungsten in Various Countries
The following is the production of ferrotungsten in major countries (based on 2023-2025 data estimates):
China:
Production: Annual output is expected to reach 30,000 tons in 2025, accounting for 70% of the world’s total, mainly concentrated in Zhuzhou, Hunan, Ganzhou, Jiangxi and Luoyang, Henan, utilizing the local abundant wolframite and scheelite resources.
Russia:
Production: About 4,000 tons per year, using tungsten mines in Siberia and the Far East, mainly exported to European and Asian markets.
EU (Austria, Germany):
Production: About 2,000 tons per year. The Mittersill mine in Austria provides tungsten concentrate, and Germany is responsible for processing.
USA:
Production: About 1,000 tons per year, relying on imports of tungsten concentrate from China and Vietnam, with production concentrated in Pennsylvania.
Vietnam:
Production: About 800 tons per year, using the Nui Phao mine resources, mainly exported to Japan, South Korea and China.
14.4 Application of Ferrotungsten
As a key alloy additive, ferrotungsten is widely used in the steel industry, casting, military industry and other fields. The following is a detailed classification and specific application scenarios:
Steel Industry
High-Speed Steel (HSS):
Application: Add tungsten iron (W content 5%-18%) to prepare high-speed steel for manufacturing cutting tools (such as drills, milling cutters, turning tools).
Performance improvement: Hardness increased to HRC 62-67, wear resistance increased by 2 times, red hardness strong (HRC>60 at 600°C), cutting speed increased by 50%-100%.
Examples:
Automobile engine cylinder block machining tools (annual demand is about 10,000 tons, with a service life of 500 hours).
Aviation titanium alloy processing tools (such as Boeing 737 wing parts, cutting accuracy ± 0.01 mm).
Tool Steel:
Application: Used for manufacturing stamping dies, cold heading dies and forging dies. Tungsten content is 3%-10%.
Improved performance: Impact resistance increased by 20%, wear resistance increased by 30%, suitable for high-intensity hot and cold processing.
Examples:
Automobile steel plate stamping dies (annual demand is about 5,000 tons, and the number of stamping times reaches 2 million times).
Bolt cold heading dies (diameter accuracy ±0.01 mm, annual demand is about 1,000 tons).
Wear Resistant Steel:
Application: Used in mining machinery (such as crusher lining) and engineering machinery (such as excavator bucket teeth), tungsten content 5%-15%.
Improved performance: Wear resistance is increased by 2-3 times, service life is extended to 2000 hours, and corrosion resistance is enhanced by 10%.
Examples:
Mining ball mill lining (annual demand is about 3,000 tons, and the wear-resistant life is up to 1 year).
Wear-resistant parts for port loading and unloading equipment (such as grab buckets, with an annual demand of about 800 tons).
Heat-resistant steel:
Application: manufacturing high temperature furnace parts and gas turbine blades, tungsten content 5%-15%.
Improved performance: High temperature oxidation resistance increased by 30%, creep resistance enhanced, and operating temperature up to 1200°C.
Examples:
Aircraft engine turbine blades (such as GE aircraft engines, with an annual demand of approximately 2,000 tons).
Steelmaking furnace lining (temperature resistance 1500°C, service life extended to 6 months).
Foundry Industry
Cast iron modification:
Application: Adding a small amount of ferrotungsten (0.5%-2%) to improve the performance of cast iron and to produce wear-resistant castings.
Improved performance: Hardness increased to HB 300-350, tensile strength increased by 15% (to 500 MPa), corrosion resistance increased by 20%.
Examples:
Pump body and valve castings (annual demand is about 1,000 tons, used under acid and alkali resistant conditions).
Wear-resistant pipe lining (chemical pipeline, annual demand is about 500 tons).
High density castings:
Application: To prepare high-density counterweights, such as crane counterweights and ship ballast.
Improved performance: Density of 15-17 g/cm³ , 20% volume reduction while maintaining high strength (compressive strength > 1000 MPa).
Examples:
Port crane counterweights (annual demand is about 500 tons, and the weight of a single piece is up to 5 tons).
Ship ballast blocks (ocean cargo ships, annual demand is about 300 tons).
Military Industry
Armor-piercing material:
Application: Tungsten iron is used as a substitute material for armor-piercing projectile core (W content 70%-80%), and is used in small-caliber ammunition or low-cost armor-piercing projectile design.
Improved performance: High density (15-17 g/cm³ ) provides excellent penetration, with penetration increased by 15%-20%, and the cost is about 30% lower than pure tungsten alloy.
Examples:
30mm cannon armor-piercing projectile (GAU-8/A, used for A-10 attack aircraft, with a penetration depth of about 70 mm steel plate, and an annual demand of about 1,000 tons).
Armor Protection:
Application: Add tungsten iron to prepare composite armor or armor steel to enhance impact resistance and penetration resistance.
Performance improvement: Penetration resistance increased by 25%, weight reduced by 10%, suitable for lightweight armor design.
Examples:
Light armored vehicle protection layer (such as some components of the Russian BTR-90, with an annual demand of about 800 tons).
Other applications
Welding materials:
Application: Tungsten iron powder is used for plasma spraying or surfacing to prepare wear-resistant coating.
Improved performance: The coating hardness reaches HRC 60, the wear resistance is increased by 2 times, and the adhesion is enhanced to 50 MPa.
Examples:
Surface strengthening of oil drill pipes (annual demand is about 300 tons, and the wear life is up to 5,000 hours).
Valve sealing surface (chemical equipment, annual demand is about 200 tons).
Scientific research purposes:
Application: Ferrotungsten is used as experimental material to study the tungsten-iron phase diagram, alloy properties and high temperature behavior.
Examples:
High temperature alloy development (testing oxidation resistance, simulating 1300°C conditions).
Research on magnetic materials (analysis of paramagnetic properties).
Global Trends: By 2030, the demand for ferrotungsten is expected to grow by 10%, driven by steel industry upgrades (annual demand to 20,000 tons), military demand (EU and US military spending drives annual demand to 3,000 tons) and infrastructure construction (demand for wear-resistant parts to grow by 15%).
READ MORE:
What’s the Facts of Tungsten (I)
What’s the Facts of Tungsten ?（II）
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