Alloy 20
Data verifiedAlloy 20 is a niobium-stabilized nickel-iron-chromium alloy with molybdenum and copper, developed specifically for hot sulfuric acid. It bridges stainless steels and nickel alloys: far better in reducing acids than 316L, at well below the cost of the high-nickel grades.
Chemical composition
| Element | Content (%) |
|---|---|
| C | ≤0.07 |
| Si | ≤1.00 |
| Mn | ≤2.00 |
| P | ≤0.045 |
| S | ≤0.035 |
| Cr | 19.00–21.00 |
| Ni | 32.00–38.00 |
| Mo | 2.00–3.00 |
| Cu | 3.00–4.00 |
| Nb | 8×C–1.00 |
Weight percent, per the governing standard ranges. Actual values per heat are on the mill certificate.
Properties
| Delivery condition | Stabilization annealed |
| Tensile strength | ≥550 MPa |
| Yield strength | ≥240 MPa |
| Density | 8.08 g/cm³ |
Heat treatment
Supplied stabilization-annealed (about 900–950 °C, water quench or rapid cool); niobium stabilization protects the weld zones against intergranular attack. Not hardenable.
Equivalent grades
| Standard | Designation |
|---|---|
| din | 2.4660 |
| aisi | UNS N08020 (Alloy 20) |
Compare side by side: Alloy 20 vs 904L · Alloy 20 vs 254 SMO
Equivalents overlap in chemistry and use but are not always identical — see our equivalents guide before substituting in certified designs.
Applications & Processing
Applications: Sulfuric acid production and handling, chemical and pharmaceutical reactors, pickling equipment, heat exchangers for mixed-acid service.
Processing: Welds with matching (320LR-type) or nickel-base fillers; good formability for a high-alloy grade; machining similar to 316 with work-hardening care.
FAQ
- Alloy 20 or 316L for sulfuric acid?
- 316L has only narrow safe windows in sulfuric acid (very dilute or very concentrated, cold). Alloy 20 was designed for the hot, mid-concentration range and is the default specification there.
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Ask for a quotationVisit NasteelSource: ASTM B463 published ranges (UNS N08020) · Last updated 2026-11-03. Data is indicative — verify critical values against the governing standard and mill certificate before use.