RAYCHIN LIMITED

Monel Hex Cap Screws – Design & Configurations

Critical Applications of Monel Hex Cap Screws

International Standards & Global Designations – Monel Hex Cap Screws

RAYCHIN LIMITED manufactures Monel hex cap screws from vacuum induction melted (VIM) material conforming to the most widely used national and international specifications. All material is traceable to the mill.

Chemical Composition (Weight %) – Monel Alloys for Hex Cap Screws

Our Monel hex cap screws are produced from vacuum induction melted (VIM) material conforming to the following limits per ASTM, AMS, and industry standards.

Monel 400 (UNS N04400) Composition

Monel K-500 (UNS N05500) Composition

Metallurgical note: Monel 400 is a solid-solution nickel-copper alloy that is hardened only through cold working. It remains ductile even at subzero temperatures and does not require heat treatment for high strength properties. Monel K-500 adds aluminum and titanium to enable precipitation hardening (aging), achieving yield strengths above 690 MPa (100 ksi) while maintaining excellent corrosion resistance. Both alloys are essentially non-magnetic (K-500 is non-magnetic; Monel 400 is slightly magnetic at room temperature but loses magnetism at elevated temperatures). The high nickel content provides exceptional resistance to stress corrosion cracking, while copper enhances resistance to reducing environments such as hydrofluoric and sulfuric acids. Hex cap screws are manufactured with precision washer facing under the head for enhanced bearing surface and clamping pressure.

Complete Mechanical & Physical Properties – Monel Hex Cap Screws (MPa / ksi)

Monel hex cap screws are supplied in various conditions per ASTM and AMS specifications. Data represent typical values based on industry standards. ksi values (kilopound per square inch) are provided alongside MPa.

Mechanical Properties – Monel 400 Hex Cap Screws

Mechanical Properties – Monel K-500 Hex Cap Screws (Age Hardened)

Physical Properties – Monel 400 & K-500

High‑Temperature Performance of Monel Hex Cap Screws

Monel alloys retain useful mechanical properties at elevated temperatures up to 540°C (1000°F) and can operate in moderately elevated environments. The alloys maintain excellent ductility and toughness from cryogenic temperatures up to 500°F (260°C) continuously, with good oxidation resistance up to 1000°F. Monel K-500 is typically limited to 480°C (900°F) to prevent over-aging of the precipitation-hardened structure. In high-temperature steam, corrosion rates are less than 0.026 mm/year.

Elevated Temperature Capabilities – Monel 400

High-Temperature Comparison – Monel vs. Stainless Steel

Note: Monel excels in applications requiring maximum corrosion resistance at moderate to high temperatures, particularly in reducing environments where stainless steels may fail. Above 480°C, Monel K-500 may experience over-aging and loss of strength.

Exceptional Corrosion Resistance of Monel Hex Cap Screws

Monel alloys offer outstanding corrosion resistance across a wide range of aggressive environments, making them suitable for the most demanding applications including marine, chemical processing, oil & gas, and power generation.

• Seawater Corrosion: Excellent resistance to flowing and stagnant seawater, with corrosion rates below 0.025 mm/year. Virtually immune to pitting and crevice corrosion in marine environments.
• Hydrofluoric Acid (HF): Monel 400 is the standard material for HF alkylation unit piping and equipment. No other commercially available alloy offers the same combination of HF resistance and mechanical strength at reasonable cost. Excellent resistance to fluorine gas and hydrofluoric acid.
• Sulfuric Acid: Good resistance to sulfuric acid concentrations above 80% at moderate temperatures.
• Hydrochloric Acid: Resistant to deaerated hydrochloric acid at low concentrations.
• Alkalis: Excellent resistance to caustic soda and potash at all concentrations and temperatures up to boiling.
• Stress Corrosion Cracking (SCC): Exceptional resistance to chloride-induced stress corrosion cracking. Excellent stress corrosion cracking resistance due to chlorine ions. Generally does not generate stress corrosion cracking in most environments.
• Hydrogen Embrittlement: Good resistance to hydrogen embrittlement when properly processed.
• High Temperature Corrosion: In high-temperature steam, corrosion rate less than 0.026 mm/year. Resistant to ammonia and aminate conditions below 585°C.
• Freshwater: Excellent corrosion resistance with minimal pitting or stress corrosion.
• Bimetallic Corrosion: Galvanic corrosion can occur when certain metals, including aluminum, zinc, and iron, are in direct contact with Monel. Using these metals as fasteners or connectors with Monel is generally not advisable.

Manufacturing Standards – Monel Hex Cap Screws

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

We offer surface finishes: passivation (ASTM A967), silver plating (AMS 2410 for anti‑seize), PTFE coating, electropolish, zinc nickel coating, and Xylan coated options. Full traceability and destructive/non‑destructive testing available (UT, MPI, PMI). ISO 13485 certified for medical applications with cleanroom packaging available. Meets ANSI, ASME, ASTM, QS, SAE and AS standards. RoHS and REACH compliant.