Material Family

Nickel-Copper Alloy (Free-Machining, Sulfur-Bearing)

Optimized for machinability while maintaining most corrosion properties.

Common Designations

UNS N04405, Monel R-405, W.Nr. 2.4362

The standard free-machining Monel grade. "Monel" is a trademark of Special Metals Corporation.

Distinguishing Feature

Enhanced Machinability for high-speed automatic screw machine operations.

This is the primary reason to specify R-405 over standard Monel 400.

Chemical Composition (Typical wt.%)

Ni: ≥ 63.0 (Balance)
Cu: 28.0 - 34.0
Fe: 2.5 max
Mn: 2.0 max
C: ≤ 0.30
Si: ≤ 0.50
S: 0.025 - 0.060

The key difference from Monel 400 is the intentional addition of Sulfur (S) to form manganese sulfide inclusions that act as chip breakers during machining.

Mechanical Properties (Annealed Plate, Room Temp)

Tensile Strength (Rm): 480 - 620 MPa
Yield Strength (Rp0.2): 170 - 345 MPa
Elongation (A): 35 - 50%

Mechanical properties are nearly identical to Monel 400 in the annealed condition.

Physical Properties

Density: 8.80 g/cm³
Melting Range: 1300 - 1350 °C

Identical to Monel 400.

Key Performance Attributes

• Excellent Free-Machining Characteristics, similar to free-machining brass or stainless steel (e.g., 303).
• Retains excellent resistance to seawater and fast-flowing brackish water.• Retains excellent resistance to hydrofluoric acid (HF) under reducing conditions.• Good resistance to sulfuric and hydrochloric acids, alkalis, and salts.

Machinability is the priority; corrosion resistance is slightly reduced compared to Monel 400 in specific media.

Corrosion Performance Note

The sulfur addition slightly reduces ductility and can marginally decrease corrosion resistance in certain severe, hot acid environments compared to low-sulfur Monel 400. Performance in seawater and most typical applications remains excellent.

For critical welded structures or the most severe HF service, Monel 400 is preferred. For machined parts, R-405 is standard.

Key Standards (Plate)

ASTM B164 / ASME SB-164 (Standard Specification for Nickel-Copper Alloy Rod, Bar, and Wire - includes R-405). Note: Plate may be supplied to this bar spec or to customer-specific agreements based on B127 chemistry with S control.

Often supplied as plate for machining into parts. The sulfur-controlled chemistry is the critical requirement.

Primary Applications

• Mass-produced Fasteners: Nuts, bolts, screws, studs for marine and chemical applications.
• Valve Components: Stems, trim, seats, bushings.
• Pump & Shaft Components requiring extensive turning and threading.
• Fittings and Machined Parts for seawater systems.

The dominant material for corrosion-resistant, free-machining components where Monel 400's properties are required.