RAYCHIN LIMITED

Tungsten Shoulder Bolts – Complete Product Range

Critical Applications of Tungsten Shoulder Bolts

International Standards & Global Designations – Tungsten Shoulder Bolt Materials

RAYCHIN LIMITED manufactures Tungsten shoulder bolts from material conforming to the most widely used national and international specifications. All material is traceable to the mill.

Chemical Composition (Weight %) – Tungsten Alloys for Shoulder Bolts

Our Tungsten shoulder bolts are produced from material conforming to the limits of applicable ASTM, AMS, and customer specifications.

Pure Tungsten – ASTM B760 / AMS 7725

Tungsten Heavy Alloys – ASTM B777 / AMS-T-21014

Metallurgical note: Tungsten heavy alloys (WHA) are produced via powder metallurgy – cold isostatic pressing, liquid phase sintering at 1450-1550°C, and subsequent heat treatment. The microstructure consists of nearly spherical tungsten grains (90-97%) embedded in a ductile Ni-Fe or Ni-Cu matrix. This composite structure combines the high density and strength of tungsten with improved ductility and machinability. Mechanical properties can be further enhanced by thermomechanical processing (swaging, rolling) which elongates tungsten grains, increasing strength along the deformation direction. For shoulder bolts, the precision ground shoulder is typically machined after heat treatment to achieve tight dimensional tolerances (h6/h7) and superior surface finish (Ra ≤ 0.8 µm).

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

Tungsten shoulder bolts are supplied in appropriate conditions (sintered, heat treated, or forged) per ASTM B777, AMS-T-21014, and customer specifications. Data represent typical values based on industry standards.

Pure Tungsten – Mechanical Properties

Tungsten Heavy Alloys (NiFe Binder) – Mechanical Properties (minimum values)

Tungsten Heavy Alloys (NiCu Binder) – Mechanical Properties (minimum values)

High‑Temperature Mechanical Properties – Pure Tungsten (representative)

Note: Tungsten maintains useful strength at temperatures exceeding 2000°C in vacuum or inert atmospheres. Above 500°C in air, tungsten oxidizes rapidly (WO₃ formation). Protective coatings required for air service above 500°C.

Physical Properties – Tungsten

High‑Temperature Performance of Tungsten Shoulder Bolts

Tungsten is the most refractory metal with the highest melting point of all elements (3410°C). This exceptional high‑temperature capability makes tungsten shoulder bolts ideal for extreme thermal environments. Tungsten maintains useful mechanical properties at temperatures exceeding 2000°C in vacuum or inert atmospheres. It exhibits excellent creep resistance and thermal stability at high temperatures. Tungsten heavy alloys (WHA) retain significant strength up to 900°C, with the nickel-iron matrix providing good ductility up to moderate temperatures. For applications above 1000°C, pure tungsten or tungsten alloys with solid solution strengthening (W-Re, W-Mo) are recommended. Tungsten's low vapor pressure ensures no contamination of vacuum environments, making it essential for vacuum furnace hot zones and semiconductor processing equipment. The coefficient of thermal expansion (4.5 × 10⁻⁶/K) is low and matches well with many ceramic and refractory materials, reducing thermal stress in high‑temperature assemblies.

Elevated Temperature Capabilities

*WHAs are limited by the melting point of the NiFe matrix (~1450°C). **Tungsten oxidizes rapidly in air above 400°C forming volatile WO₃. Protective coatings required for air service above 500°C.

Corrosion Resistance of Tungsten Shoulder Bolts

Tungsten exhibits good corrosion resistance in many environments, though its behavior differs significantly from common metals. The protective WO₃ oxide film is stable in oxidizing media but volatilizes at high temperatures. Tungsten heavy alloys (WNiFe) offer enhanced corrosion resistance in many industrial environments.

• Atmospheric Corrosion: Tungsten is highly resistant to atmospheric corrosion at room temperature, forming a stable oxide layer. Suitable for outdoor applications in clean environments.
• Acid Resistance: Tungsten is resistant to hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid at room temperature. Attack occurs in oxidizing acids at elevated temperatures. WNiFe alloys show good resistance in most non-oxidizing acids.
• Alkali Resistance: Good resistance to most alkalis at room temperature. Attacked by molten alkalis and oxidizing alkaline solutions.
• Molten Metals: Excellent resistance to molten metals including Li, Na, K, Mg, Zn, and Bi up to high temperatures. Used in liquid metal handling systems.
• Liquid Metals: Good compatibility with liquid metals (Li, Na, K, Bi, Pb) at elevated temperatures, used in nuclear reactor coolant systems.
• Halogens: Resistant to dry halogens at room temperature; attacked by moist halogens and at elevated temperatures.
• High‑Temperature Oxidation: Tungsten oxidizes rapidly above 400°C in air forming volatile WO₃. For high‑temperature air service, protective coatings (MoSi₂, ZrO₂) or inert atmospheres are required.
• Galvanic Corrosion: Tungsten is noble relative to most structural metals; can accelerate corrosion of active metals (steel, aluminum) in contact. Isolation or coating recommended.
• Radiation Resistance: Tungsten maintains excellent corrosion resistance under radiation, making it ideal for nuclear applications.
• Radiopacity: Tungsten's high density provides exceptional X‑ray and gamma radiation attenuation, making shoulder bolts ideal for imaging fixtures and shielding components.

Manufacturing Standards – Tungsten Shoulder Bolts

All Tungsten shoulder bolts are manufactured and tested to meet the following standards:

We offer surface finishes: plain (as‑machined), ground, polished. The shoulder is precision ground to tolerances of ±0.0005" (inch) or h6/h7 (metric) with surface finish Ra ≤ 0.8 µm. Tungsten shoulder bolts can be supplied with certified material traceability, dimensional inspection reports, and mechanical test certificates. Our manufacturing processes include CNC machining from sintered bar stock, precision cylindrical grinding, thread rolling, and heat treatment. We specialize in custom configurations including non‑standard shoulder diameters, extra‑long shoulders, special head markings, and proprietary thread forms. Cleanroom packaging available for medical and semiconductor applications. All bolts supplied with EN 10204 Type 3.1 or 3.2 certification. ISO 9001:2015 and AS9100D certified quality management system.