Sanicro® 32Cu, commonly known as Alloy 20, is an austenitic nickel-iron-chromium alloy, in the same alloy category as Sanicro 41. It is characterized by:
-
Excellent corrosion resistance in environments containing sulphuric acid, chlorides, nitric and phosphoric acid
-
Very good resistance in oxidizing environments
-
Sufficient resistance to stress corrosion cracking (SCC) in chloride-bearing environments
Standards
- UNS: N08020
- W.Nr.: 2.4660
Product standards
Suitable for the production of flanges etc. according to ASTM A182 and B462
Certificates
Status according to EN 10 204 3.1
Chemical composition (nominal) %
| C | Si | Mn | P | S | Cr | Ni | Mo | Other |
|---|---|---|---|---|---|---|---|---|
| ≤0.025 | 0.5 | 1.8 | ≤0.025 | ≤0.010 | 19.5 | 32.5 | 2.2 | Cu=3.3 Nb>8xC |
Applications
Sanicro® 32Cu has excellent resistance in chemical environments containing sulphuric acid, chlorides, nitric and phosphoric acid.
The combination of high strength with good corrosion resistance in acidic environments makes Sanicro® 32Cu a suitable grade for the production of gases, solvents, organic and inorganic chemicals.
| Industrial categories | Typical applications |
|---|---|
| Chemical industry | Flanges |
| Food industry | Valves and discs |
| Petrochemical industry | Fittings |
| Pulp and paper industry | Couplings |
| Oil & Gas industry | Rings and seals |
| Bolts and nuts | |
| Shafts | |
| Forgings | |
| Piping | |
| Pumps | |
| Tanks |
Corrosion resistance
General corrosion
Sanicro® 32Cu possesses excellent resistance to corrosion. The material is clearly superior to molybdenum-alloyed steels, such as AISI 316L, particularly when exposed to non-oxidizing media, such as sulphuric acid.
Pitting and crevice corrosion
The resistance of Sanicro® 32Cu to pitting and crevice corrosion is superior to that of AISI 316 - a result of the higher chromium and molybdenum contents in the material.
Stress corrosion cracking
The high nickel content of the material promotes excellent resistance to stress corrosion cracking induced by both chlorides and alkalis. The resistance to stress corrosion cracking in sour environment is good.
Intergranular corrosion
Since the material is Nb-stabilized, there is less risk of intergranular corrosion.
Forms of supply
Sizes and tolerances
Round-cornered square, as well as round billets, are produced in a wide range of sizes according to the following tables. Larger sizes offered on request.
Surface conditions
Square billets
Unground, spot ground or fully ground condition.
Round billets
Peel turned or black condition.
| Size | Tolerance | Length |
|---|---|---|
| mm | mm | m |
| 80 | +/-2 | 4 - 6.3 |
| 100, 114, 126, 140, 150 | +/-3 | 4 - 6.3 |
| 160, 180, 195, 200 | +/-4 | 4 - 6.3 |
| >200 - 350 | +/-5 | 3 - 5.3 |
Sizes and tolerances apply to the rolled/forged condition.
| Size | Tolerance | Length |
|---|---|---|
| mm | mm | m |
| 75 - 200 (5 mm interval) | +/-1 | max 10 |
| >200 - 450 | +/-3 | 3 - 8 |
| Size | Tolerance | Length |
|---|---|---|
| mm | mm | m |
| 77 - 112 (5 mm interval) | +/-2 | max 10 |
| 124, 134 | +/-2 | max 10 |
| 127, 147, 157 | +/-2 | max 10 |
| 142, 152, 163 | +/-2 | max 10 |
| 168, 178, 188 | +/-2 | max 10 |
| 183, 193 | +/-2 | max 10 |
Other products
- Seamless tube and pipe
- Hollow bar
Heat treatment
Billets are delivered in the hot worked condition. The following heat treatment is recommended for finished products.
Stabilization annealing
930-1010°C (1700-1850°F), followed by quenching in water.
Mechanical properties
Sanicro® 32Cu conforms to the mechanical properties according to specification ASTM B462. Testing is performed on separately solution annealed and quenched test pieces.
At 20°C (68°F)
|
Proof strength
|
Tensile strength
|
Elongation
|
|---|---|---|
| Rp0.21) | Rm | A |
| MPa | MPa | % |
|
≥241
|
≥551
|
≥30
|
At 68 oF
|
Proof strength
|
Tensile strength
|
Elongation
|
|---|---|---|
| Rp0.21) | Rm | A |
| ksi | ksi | % |
|
≥35
|
≥80
|
≥30
|
1) Corresponds to 0.2 % offset yield strength
At high temperatures
The mechanical properties are stable up to 550°C.
Physical properties
Density: 7.9 g/cm3
Hot working
The hot forming range for Sanicro® 32Cu is 900-1175°C (1740-2150°F), followed by quenching in water. Subsequent heat treatment should be carried out in accordance with the recommendations given for heat treatment.
Welding
The weldability of Sanicro® 32CU is good. Suitable methods of fusion welding are manual metal-arc welding (MMA/SMAW) and gas-shielded arc welding, with the TIG/GTAW method as first choice. Preheating and post-weld heat treatment are not necessary.
The welding of fully austenitic steels often entails the risk of hot cracking, particularly if the weldment is under constraint. To reduce the cracking risk, the welding should be carried out with a low heat input.
For Sanicro® 32CU, heat input of <1.0 kJ/mm and interpass temperature of <100°C (210°F) are recommended. A string bead welding technique should be used.
Recommended filler metals
TIG/GTAW or MIG/GMAW welding
ISO 14343 S 27 31 4 Cu L/AWS A5.9 ER383 (e.g. Exaton 27.31.4.LCu)
MMA/SMAW welding
ISO 3581 E 27 31 4 Cu L R/AWS A5.4 E383-16 (e.g. Exaton 27.31.4.LCuR)
Machining
Machining Sanicro® 32Cu, as with other stainless steels, requires an adjustment to tooling data and machining method, in order to achieve satisfactory results. Compared to Sanmac® 316/316L, the cutting speed must be reduced by approximately 50-55%, when turning Sanicro® 32Cu with coated, cemented carbide tools. Much the same applies to other operations. Feeds should only be reduced slightly and with care.
Detailed recommendations for the choice of tools and cutting data are provided in the data sheet for Sanmac® 316/316L.
Disclaimer: Recommendations are for guidance only, and the suitability of a material for a specific application can be confirmed only when we know the actual service conditions. Continuous development may necessitate changes in technical data without notice. This datasheet is only valid for Alleima materials.