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
Suitable for the production of flanges etc. according to ASTM A182 and B462
Status according to EN 10 204 3.1
Chemical composition (nominal) %
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|
|Food industry||Valves and discs|
|Pulp and paper industry||Couplings|
|Oil & Gas industry||Rings and seals|
|Bolts and nuts|
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.
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.
Unground, spot ground or fully ground condition.
Peel turned or black condition.
|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.
|75 - 200 (5 mm interval)||+/-1||max 10|
|>200 - 450||+/-3||3 - 8|
|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|
- Seamless tube and pipe
- Hollow bar
Billets are delivered in the hot worked condition. The following heat treatment is recommended for finished products.
930-1010°C (1700-1850°F), followed by quenching in water.
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)
At 68 oF
1) Corresponds to 0.2 % offset yield strength
At high temperatures
The mechanical properties are stable up to 550°C.
Density: 7.9 g/cm3
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.
The weldability of Sanicro® 32Cu is good. Suitable methods of fusion welding are manual metal-arc (MMA), tungsten inert gas (TIG) and metal inert gas (MIG). Preheating and post-weld heat treatment are normally not necessary.
The standard of cleanliness required when welding fully austenitic stainless steels is particularly strict. Joint surfaces and filler metals must be free from grease, paint and other contaminants. The weld zone should be cleaned, as required, using a suitable solvent, such as acetone or alcohol.
Sanicro® 32Cu, like other austenitic materials, has a high coefficient of thermal expansion. Welding should, therefore, be carried out with a low heat input, using well prepared welding procedures, to control distortion of the welded construction.
As fully austenitic materials are rather sensitive to hot cracking, welding should be carried out with the lowest practical heat input, <1.0kJ/mm and an interpass temperature of < 100°C (210 oF).
The recommended filler metal for TIG and MIG welding is Sandvik 27.31.4.LCu. For both TIG and MIG/MAG welding, pure argon should be used as a shielding gas and for MIG/MAG welding, a pulsed current is suggested. For manual metal-arc welding (MMA), Sandvik 27.31.4.LCuR is the recommended choice. In severe, corrosive environments, when copper is an essential alloying element, a filler metal with a higher copper content should be used.
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.