Alloy 20 / Carpenter 20
2.4660Austenitic Ni-Fe-Cr alloy specifically developed for sulfuric acid resistance. Nb-stabilized against sensitization. Cu addition gives outstanding resistance to H2SO4 at all concentrations up to 80%. Used for sulfuric acid piping, heat exchangers, mixing tanks, pickling equipment, and pharmaceutical processing.
International equivalents
| Flag | Standard | Country | Grade | Number | Match |
|---|---|---|---|---|---|
| 🇺🇸 | ASTM | USA | UNS N08020 | N08020 | REF |
| 🇪🇺 | EN | Europe | NiCr20CuMo | 2.4660 | 100% |
Sources: ASTM B463, DIN 17744
Chemical composition comparison (wt%)
Side-by-side: Alloy 20 / Carpenter 20 (ASTM) (ASTM B463) vs NiCr20CuMo (EN)
| Element | Alloy 20 / Carpenter 20 (ASTM) | NiCr20CuMo (EN) | Overlap |
|---|---|---|---|
| C | 0–0.07% | — | — |
| Si | 0–1% | — | — |
| Mn | 0–2% | — | — |
| P | 0–0.035% | — | — |
| S | 0–0.035% | — | — |
| Cr | 19–21% | — | — |
| Mo | 2–3% | — | — |
| Ni | 32–38% | — | — |
| Cu | 3–4% | — | — |
| Nb | 0–1% | — | — |
| Fe | — | — | — |
Mechanical properties
Stabilize Annealed
| Property | Value | Unit |
|---|---|---|
| Tensile Strength | ≥ 551 | MPa |
| Yield Strength | ≥ 241 | MPa |
| Elongation | ≥ 30 | % |
| Elastic Modulus | ≥ 193 | GPa |
| Density | ≥ 8.08 | g/cm3 |
Heat treatment
| Process | Temperature | Medium | Holding Time | Notes |
|---|---|---|---|---|
| stabilize_annealing | 982–1010 °C | water | 30-60 min | Stabilize anneal: Nb forms NbC to prevent sensitization |
Compatibility verdict
Alloy 20 / Carpenter 20 and NiCr20CuMo: 100% composition match
Close equivalents but NOT identical.
Related materials
Hastelloy C-22
2.4602Improved version of Hastelloy C-276 with better resistance to oxidizing media and higher chromium. Considered the most versatile Ni-Cr-Mo alloy for chemical processing. Resists both oxidizing and reducing acids, chlorides, and mixed media. Used for flue gas desulfurization, pharmaceutical, and universal chemical processing.
Nimonic 80A
2.4952Nickel-chromium age-hardenable alloy with Ti + Al for gamma-prime strengthening. Developed originally for gas turbine blades. Good creep resistance to ~700°C. Used for exhaust valves, springs at elevated temperatures, nuclear engineering fasteners, and gas turbine components. ≈ UNS N07080.
Haynes 230
2.4733Nickel-chromium-tungsten alloy — THE combustor can material for gas turbines. Outstanding oxidation resistance to 1149°C for prolonged exposure. Excellent long-term thermal stability (no sigma/mu phase after 16000h at 649-870°C). Lower thermal expansion than most high-temp alloys. Lanthanum addition improves oxide scale adherence. Used for gas turbine combustion cans, transition ducts, furnace retorts, and catalyst grids in nitric acid production.
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