Hangbo Alloy Group
Shanghai · Est. 2012
N08026 technical guide: nominal chemical composition, mechanical and physical properties, corrosion resistance, welding, product forms and ASTM standards...
Alloy 20Mo-6 (UNS N08026) is a nickel-iron-chromium-molybdenum-copper alloy. Highest-Mo 20-family grade (5–6.5 % Mo). Strongest pitting/acid resistance of the family. This guide covers its nominal chemical composition, typical mechanical and physical properties, corrosion behaviour, welding, common applications, available product forms and the ASTM standards that apply — everything a specifier needs to evaluate Alloy 20Mo-6 for a project.
Alloy 20Mo-6 belongs to the nickel-iron-chromium-molybdenum-copper alloy class of materials. It is highest-mo 20-family grade (5–6.5 % mo). It is strongest pitting/acid resistance of the family. It is nb-stabilised welds.
Nominal (wt%) composition of Alloy 20Mo-6 (UNS N08026):
| Element | Composition (wt%) |
|---|---|
| Nickel (Ni) | 33.0 – 37.0 |
| Chromium (Cr) | 22.0 – 26.0 |
| Iron (Fe) | Balance |
| Molybdenum (Mo) | 5.0 – 6.5 |
| Copper (Cu) | 2.0 – 4.0 |
| Niobium (Nb) | 0.10 – 0.40 |
| Carbon (C) | ≤ 0.03 |
| Manganese (Mn) | ≤ 1.0 |
| Silicon (Si) | ≤ 0.75 |
| Sulphur (S) | ≤ 0.035 |
| Phosphorus (P) | ≤ 0.045 |
Typical physical properties:
| Property | Value |
|---|---|
| Density | 8.10 g/cm³ |
| Melting Range | 1300 – 1400 °C |
| Thermal Expansion (20–1000 °C) | 15.0 µm/m·K |
| Thermal Conductivity (100 °C) | 12.0 W/m·K |
| Modulus of Elasticity | 195 GPa |
Typical room-temperature mechanical properties (annealed / specified condition unless noted):
| Property | Typical Value |
|---|---|
| Tensile Strength (Rm) | 580 MPa (84 ksi) |
| Yield Strength, 0.2% (Rp0.2) | 260 MPa (38 ksi) |
| Elongation in 50 mm | 40% |
| Hardness (Rockwell B) | 75 – 92 HRB |
| Property | Value |
|---|---|
| Service temperature | Cryogenic to ≈ 500 °C |
Its pitting resistance equivalent number (PREN) is approximately ≈ 34, placing it among the more locally-corrosion-resistant grades for chloride service. 20Mo-6 is the highest-molybdenum of the 20-family alloys (5–6.5 % Mo), giving it the strongest resistance to pitting, crevice corrosion and reducing acids such as hot sulphuric and phosphoric acid. Copper and niobium further aid acid resistance and weld stability.
Welded with matching or 20-type/625-type fillers; low carbon and niobium prevent sensitisation. Qualified procedures and minimal dilution keep corrosion resistance intact.
The grade is supplied to the following common specifications:
| Standard | Product Form / Scope |
|---|---|
| ASTM B463 | Plate, sheet & strip |
| ASTM B464 | Welded pipe |
| ASTM B468 | Welded tube |
| ASTM B366 | Fittings |
Standards & References. Specifications cited on this page; confirm current revisions with the issuing body.
General references: Nickel Institute · AMPP (corrosion) · SAE International · ASTM International
20Mo-6 is the highest-molybdenum member of the 20 family, with 5–6.5 % molybdenum for the strongest resistance to pitting, crevice corrosion and reducing acids such as hot sulphuric and phosphoric acid, plus copper and niobium for acid resistance and weld stability.
Annealed: ≈ 580 MPa tensile, ≈ 260 MPa yield, 40 % elongation, 75–92 HRB.
Pick 20Mo-6 for the most aggressive acid/pitting duty (highest Mo); choose 20Mo-4 when the service is less severe and cost matters.
Yes, with matching or 20/625-type fillers; low carbon and niobium prevent sensitisation in the weld.
Hot sulphuric/phosphoric acid plant, sulphate-pulp digesters, acid-service heat exchangers, pharmaceutical vessels and acid-transfer piping.
Plate/sheet/strip ASTM B463, welded pipe B464, welded tube B468, fittings B366.
As a dedicated nickel alloy manufacturer serving chemical processing, marine sectors, Hangbo Alloy Group supplies the grades discussed here across all standard product forms with full ASTM/ASME documentation and EN 10204 3.1 certification. Our material is specified for applications where corrosion resistance, high-temperature strength, and traceable quality are non-negotiable. See our production & testing facilities for more on how every heat is verified.