Material Family

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

The free-machining version of Monel 400, optimized for machinability.

Distinguishing Feature

Enhanced Machinability for high-speed automatic screw machine and CNC lathe operations.

This is the primary reason to specify R-405 over standard Monel 400 pipe for machined parts.

Common Forms

Seamless Pipe (SMLS) is the standard form, typically used as raw material for machining into components rather than as process piping.

Pipe is used as bar stock alternative for producing machined parts.

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, 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.

Machinability Rating

Excellent. Typically rated at 70% on the free-machining brass scale (where 100% is C36000 brass). Similar machinability to free-machining stainless steel 303.

Allows for high production speeds, excellent surface finish, and extended tool life compared to Monel 400.

Corrosion Performance Note

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

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

Key Standards (Pipe)

ASTM B165 / ASME SB-165 can apply, but procurement is often based on ASTM B164 (Standard Specification for Nickel-Copper Alloy Rod, Bar, and Wire) specifications with pipe dimensions.

The sulfur-controlled chemistry (UNS N04405) is the critical procurement requirement.

Typical Applications

• Machined Fittings: Nipples, couplings, unions, bushings for seawater and chemical systems.
• Valve Components: Stems, seats, trim parts, plugs.
• Pump & Shaft Components: Sleeves, shafts, impeller nuts, wear rings.
• Fasteners: Machined studs, bolts, nuts for marine environments.

Used almost exclusively as raw material for machining corrosion-resistant components, not as welded process piping.