Alloy 20 is a nickel–chromium–molybdenum stainless steel alloy developed for applications involving sulfuric acid. Its corrosion resistance also finds other uses in the chemical, food, pharmaceutical, power generation, and plastics industries.
Alloy 20 resists pitting and chloride ion corrosion and its copper content protects it from sulfuric acid. Alloy 20 is often chosen to solve stress corrosion cracking problems, which may occur with 316L stainless steels.
Standards
- UNS: N08020
- W.Nr.: 2.4660
Chemical composition (nominal)
| C | Si | Mn | P | S | Cr | Ni | Mo | Cu | Nb |
|---|---|---|---|---|---|---|---|---|---|
| ≤0.06 | ≤1.0 | ≤2.0 | ≤0.035 | ≤0.001 | 19.0 - 21.0 | 32.5 - 35.0 | 2.0 - 3.0 | 3.0 - 4.0 | 8xC, max 1.0 |
Nb = 8 x C, max 1.0
Forms of supply
Alloy 20 is supplied as hot-rolled, annealed and pickled wire rod, in coils.
| Dimension, mm (in.) | Tolerance, mm (in.) | Ovality, mm (in.) |
|---|---|---|
| 5.5 (0.216) | +0.1/-0.25 (+0.004/-0.01) | 0.23 (0.009) |
Physical dimensions of delivered product
| Coil weight | 200 - 225 kg (440 - 495 lb) |
| Coil size, ID | ≥ 700 mm (27.6 in.) |
| Coil size, OD | ≤ 1100 mm (43.3 in.) |
Mechanical properties
| Proof strength, Rp0.2a | Tensile strength, Rm | Elongation, A100 | ||
|---|---|---|---|---|
| MPa | ksi | MPa | ksi | % |
| 310-370 | 45-54 | 610-650 | 88-94 | ≥ 30 |
1 MPa = 1 N/mm2
a) Rp0.2 corresponds to 0.2% offset yield strength.
Physical properties
| Density | 8.1 g/cm3 |
| Specific heat (RT‐1000°C) | 500 J/kgK |
| Electrical resistivity (RT‐1000°C) | 1.08 Ωmm²/m |
| Thermal conductivity (RT‐1000°C) | 12.3 W/mK |