RAYCHIN LIMITED

Tungsten Hex Cap Screws – Comprehensive Product Range

International Standards & Global Designations – Tungsten Hex Cap Screws

RAYCHIN LIMITED manufactures tungsten hex cap screws from vacuum arc melted (VAR) or powder metallurgy processed material conforming to the most widely used national and international specifications. All material is traceable to the mill with complete certifications.

Chemical Composition (Weight %) – Tungsten & Tungsten Alloys

Our tungsten hex cap screws are produced from vacuum arc melted (VAR) or powder metallurgy processed material conforming to the limits of applicable ASTM and AMS specifications.

Pure Tungsten (ASTM B760)

Tungsten Heavy Alloys (ASTM B777)

Metallurgical note: Tungsten is a refractory metal with the highest melting point of all metals (3422°C). Pure tungsten exhibits a body-centered cubic crystal structure and exceptional high-temperature strength, but is brittle at room temperature and difficult to machine. Tungsten heavy alloys are produced by liquid phase sintering of tungsten powder with nickel-iron or nickel-copper binders, creating a composite microstructure of tungsten grains embedded in a ductile matrix. This structure provides improved machinability and ductility while maintaining high density. The nickel-iron binder system offers higher strength and is magnetic, while nickel-copper binder provides non-magnetic properties – essential for certain medical and electronic applications. Higher tungsten content (Class 4 > Class 1) increases density but reduces ductility and machinability. All tungsten alloys are susceptible to oxidation above 500°C and require protective atmospheres or coatings for high-temperature service in air. Tungsten's radiopacity exceeds that of lead, making it ideal for radiation shielding applications.

Complete Mechanical & Physical Properties – Tungsten Alloys (MPa / ksi)

Tungsten hex cap screws are supplied in sintered, annealed, or stress-relieved condition per applicable ASTM specifications. Data represent typical values based on industry standards.

Mechanical Properties – Tungsten Heavy Alloys (ASTM B777)

Pure Tungsten – Mechanical Properties

High-Temperature Mechanical Properties – Class 3 (95% W) Alloy

High-temperature testing in vacuum or inert atmosphere. Mechanical properties degrade above 800°C due to microstructural changes in the binder phase. Pure tungsten maintains strength to much higher temperatures.

Physical Properties – Tungsten Alloys

High‑Temperature Performance of Tungsten Hex Cap Screws

Tungsten is the refractory metal with the highest melting point (3422°C) and exceptional high-temperature strength and stability in vacuum or inert atmospheres. Pure tungsten maintains useful mechanical properties up to 2800°C (5072°F) in non-oxidizing environments, making it suitable for extreme temperature applications in rocket engines, plasma-facing components, and high-temperature furnaces. Tungsten heavy alloys have lower maximum service temperatures (typically 800-1000°C) due to the presence of lower-melting binder phases (Ni-Fe, Ni-Cu) which begin to soften and weaken at elevated temperatures.

Elevated Temperature Capabilities

Note: Tungsten begins to oxidize rapidly above 500°C in air. All high-temperature applications require vacuum, inert atmosphere, or protective coatings.

Corrosion Resistance of Tungsten Hex Cap Screws

Tungsten has unique corrosion characteristics that vary significantly between pure tungsten and tungsten heavy alloys.

Oxidation Behavior

Tungsten begins to oxidize rapidly at temperatures above 500°C in air, forming volatile tungsten trioxide (WO₃). This leads to rapid material loss and catastrophic failure. Therefore, tungsten hex cap screws are not suitable for high-temperature applications in air without protective coatings (such as MoSi₂, SiC, or Ir). In vacuum or inert gas atmospheres (argon, helium, hydrogen), tungsten maintains its strength and integrity to very high temperatures.

Chemical Resistance

• Oxidation Resistance: Poor above 500°C in air – requires protective atmosphere or coating for high-temperature service.
• Acid Resistance: Tungsten is slowly attacked by most mineral acids at room temperature, and rapidly dissolved by a mixture of hydrofluoric and nitric acids. Tungsten heavy alloys may suffer galvanic corrosion between tungsten grains and the binder phase in aqueous electrolytes – not recommended for wet chemical environments without protective measures.
• Alkali Resistance: Good resistance to alkalis at room temperature.
• Liquid Metal Compatibility: Excellent resistance to attack by many molten metals (Li, Na, K, Mg, Zn, Ag) – valuable for nuclear and metallurgical applications.
• Hydrogen Compatibility: Fully compatible with hydrogen up to very high temperatures – used in hydrogen furnace applications.
• Radiopacity: Tungsten's high density makes it highly radiopaque – even better than lead. Tungsten hex cap screws block radiation effectively and show up clearly on X-rays, making them ideal for medical imaging markers and radiation shielding applications.
• Non-Toxicity: Tungsten is non-toxic and non-radioactive (in its natural isotopic composition), making it safe for medical and food processing applications.

Manufacturing Standards – Tungsten Hex Cap Screws

All tungsten hex cap screws are manufactured and tested to meet the following standards:

We offer surface finishes: as-sintered, ground, polished, or coated with oxidation-resistant coatings (MoSi₂, SiC, Ir) for high-temperature air service. Controlled sintering and heat treatment processes per ASTM specifications ensure consistent mechanical properties. Specialized CNC grinding and thread machining for accurate hex head geometry – tungsten alloys require diamond tooling and specialized techniques due to their extreme hardness and brittleness. Class 6g/2A thread fit. 100% inspection available including dimensional inspection, hardness testing, density verification, and non-destructive examination. Full traceability and material test reports (MTR) with mill certifications available. AS9100 and ISO 9001:2015 certified quality management. ISO 13485 certified for medical applications with cleanroom packaging available. Build-to-print specials to customer specifications are available.