High Temperature Resistant Bolts And Nuts

1. Material Selection: The Cornerstone of High-Temperature Performance and Durability
Chromium-Molybdenum-Vanadium Steel: Suitable for temperatures below 540°C, such as 21CrMoV5-7. Through a quenching and tempering heat treatment process, it exhibits excellent mechanical properties and is widely used in fastener manufacturing for high-temperature and high-pressure environments.
Nickel-Based Alloys: Suitable for temperatures up to 650°C, such as A286 (GH2132). These alloys exhibit high yield strength, long-lasting strength, and creep strength below 650°C, along with good processing ductility and satisfactory weldability.
Austenitic Stainless Steel: Resistant to temperatures up to 1150°C (310S), it offers strong oxidation and corrosion resistance and is suitable for applications such as chemical and boiler applications.
2. Processing Technology:
Cold Heading/Hot Forging: Cold heading is suitable for mass production of standard bolts (e.g., M3-M12) and is highly efficient. Hot forging improves metal density and is suitable for large or complex-shaped parts.
Turning/Milling/Grinding: CNC machining achieves high-precision external and internal diameters. Grinding improves dimensional accuracy and surface quality. Thread Processing: Tap tapping or thread milling, with gauges used to verify thread tightness. rolled threads enhance surface strength.
Heat Treatment: Solution treatment (950-1050°C) + aging (720°C) strengthens nickel-based alloys. quenching and tempering (quenching + high-temperature tempering) balances the strength and toughness of alloy steels. annealing relieves stress, normalizing improves microstructure, and tempering enhances toughness.
Surface Treatment: Copper plating and other surface treatments enhance high-temperature sintering resistance.
3. Quality Control:
Product precision testing is ensured using vernier calipers, micrometers, projectors, and profilometers.
Mechanical Properties: Hardness testing, tensile strength, and fatigue life testing. high-temperature creep resistance and corrosion resistance testing.
Installation and Maintenance: Preload control (avoid overtightening/undertightening) and regular inspection for loosening, wear, and corrosion. In high-temperature environments, bolts and nuts with similar thermal expansion coefficients should be used to minimize deformation discrepancies.
4. Design Optimization:
Structural Optimization: Bolts utilize rolled threads and anti-loosening features. Process Optimization: Precision machining combined with online inspection ensures dimensional consistency.
5. Customization Considerations for Special Scenarios
Automotive Industry: Exhaust manifold bolts must withstand temperatures of 500-700°C. Heat-resistant steel such as A286 is used, and the surface is plated with copper or molybdenum disulfide to prevent sintering.