Material Family

Nickel-Molybdenum Alloy (Low Iron, Low Carbon)

The premier alloy bar for severe, non-oxidizing reducing acid service.

Common Forms (Bar)

Hot Rolled, Forged, or Cold Finished Rounds. Also as Forging Billet.

Typically supplied as round bar for machining into corrosion-resistant components.

Chemical Composition (Typical wt.%)

Ni: ≥ 69.0 (Balance)
Mo: 26.0 - 30.0
Fe: 2.0 max
Cr: 1.0 max
C: ≤ 0.010
Si: ≤ 0.08

Extremely High Molybdenum (Mo) provides resistance to reducing acids. Very Low Chromium (Cr) and Iron (Fe) are critical to prevent catastrophic attack by even trace oxidants.

Mechanical Properties (Annealed, Room Temp)

Tensile Strength (Rm): 760 - 965 MPa
Yield Strength (Rp0.2): 350 - 550 MPa
Elongation (A): 40 - 60%

High strength and excellent ductility in the annealed condition, suitable for machining.

Physical Properties

Density: 9.22 g/cm³
Melting Range: 1330 - 1380 °C

One of the densest common nickel alloy bars due to high molybdenum content.

Key Corrosion Resistance (and Limitation)

• Unparalleled resistance to hydrochloric acid (HCl) at all concentrations and temperatures up to the boiling point.

• Excellent resistance to sulfuric (H₂SO₄), phosphoric (H₃PO₄), and acetic acids under strictly reducing, oxygen-free conditions.

•  CRITICAL LIMITATION: Very poor resistance to oxidizing agents (e.g., Fe³⁺, Cu²⁺ ions, HNO₃, oxygen, chlorine). Presence of even ppm-level oxidants can cause severe, rapid corrosion.

A specialist alloy bar with an extremely specific application window. Must be used in strictly oxygen-free, reducing environments.

Key Standards (Bar)

ASTM B335 / ASME SB-335 (Standard Specification for Nickel-Molybdenum Alloy Rod), DIN 2.4617

ASTM B335 is the primary specification for bar (rod) products.

⚠️ Critical Fabrication Warning

Severe Thermal Sensitivity: Prolonged exposure in the 550-1050°C range (during slow cooling from annealing, welding, or brazing) can cause precipitation of brittle intermetallic phases (mu, P), drastically reducing ductility and corrosion resistance. Fabrication requires rapid cooling after any thermal cycle.

This is the major drawback of B-2. It makes welding and complex fabrication high-risk without extreme control.

Machinability

Machinability Rating: ~40%. It is somewhat easier to machine than many nickel alloys due to its higher hardness in the annealed state, but still requires care to avoid work hardening.

Use sharp tools, positive rakes, and adequate coolant.

Typical Bar Applications

• HCl Service: Pump shafts, valve stems, stirrers, fasteners for dedicated hydrochloric acid production, pickling, and handling systems.
• Reducing Acid Process Components: Machined internals for strictly controlled sulfuric/acetic acid processes.

Used almost exclusively for machined parts in highly controlled, strictly reducing chemical processes.