Sandvik 2RK65™ ('904L') is a high-alloy austenitic stainless steel intended for use under severe corrosion conditions within the process industry. The material is characterized by:
- Very good resistance to attack in acidic environments, e.g. sulphuric, phosphoric and acetic acid
- Very good resistance to pitting in neutral chloride-bearing solutions
- Much better resistance to crevice corrosion than steels of the ASTM 304 and ASTM 316 types
- Very good resistance to stress corrosion cracking
- Good weldability
: X1 NiCrMoCu25 20 5
Suitable for the production of flanges etc. according to ASTM A182 Grade F904L.
Status according to EN 10 204 3.1
Chemical composition (nominal) %
Sandvik 2RK65™ is a multi-purpose material for use under severe corrosion conditions. This has been proven both by laboratory tests and by extensive operational experience with the steel.
Typical applications for Sandvik 2RK65™ are found in oil refineries and within the chemical and petrochemical industry.
Sandvik 2RK65™ is also used within the pulp and paper, mineral and metallurgical and food industries, in seawater cooling and in many other fields.
The grade is an excellent alternative to standard austenitic stainless steels in heat exchangers using high temperature water with chloride contamination.
|Industrial categories||Typical applications|
|Pulp and paper industry||Couplings|
|Metallurgical industry||Bolts and nuts|
|Pigtails and headers|
Because of the high contents of nickel, chromium and molybdenum the resistance to general corrosion is above that of AISI 316L.
Pitting and crevice corrosion
The high chromium and molybdenum contents of this steel make its resistance to pitting and crevice corrosion superior to AISI 316L.
Stress corrosion cracking
Ordinary austenitic steels of the AISI 304 and AISI 316 types are susceptible to stress corrosion cracking in chloride-bearing solutions at temperatures above about 60°C (140oF). At high temperatures, above about 100oC, chloride contents as low as in the ppm-range (10-4 %) are sufficient to cause stress corrosion cracking in these steels. A nickel content of 25%, as is the case for Sandvik 2RK65™, is sufficient to provide very good resistance under working conditions.
For further information regarding corrosion resistance of Sandvik 2RK65™, please see the data sheet - Seamless tube and pipe - Sandvik 2RK65™. The data should be considered in the knowledge that it may not be applicable for thick sections, such as forgings.
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|
- Welded tube and pipe
- Seamless tube and pipe
- Strip, annealed or cold-rolled to different degrees of hardness
Billets are delivered in the hot worked condition. The following heat treatment is recommended.
1050-1150°C (1920-2100°F), followed by quenching in water.
Testing is performed on separately solution annealed and quenched test pieces.
The following figures apply to material in the solution annealed condition.
At 20°C (68°F)
|Proof strength||Tensile strength||Elong||Hardness|
|Proof strength||Tensile strength||Elong||Hardness|
1 MPa = 1 N/mm2
a) Rp0.2 and Rp1.0 correspond to 0.2% offset and 1.0% offset yield strengths, respectively.
b) Based on L0 = 5.65 √S0 where L0 is the original gauge length and S0 the original cross-section area.
Due to its austenitic microstructure, Sandvik 2RK65™ has very good impact strength both at room temperature and at cryogenic temperatures. Tests have demonstrated that the steel fulfils the requirements (60 J (44 ft-lb) at -196 oC (-320 oF)) according to the European standards EN 13445-2 (UFPV-2) and EN 10216-5.
At high temperatures
The steel should not be exposed to temperatures above about 550 °C (1020 °F) for prolonged periods, since this leads to precipitation of intermetallic phases, which can have an adverse effect on both the mechanical properties and the corrosion resistance of the steel. Minimum proof strength properties at high temperatures are based on datasheets seamless tubes and pipe. Since the tubes have thin walls the values should only be used as indicative values for billets.
Density: 8.0 g/cm3, 0.29 lb/in3
|Temperature, °C||W/(m °C)||Temperature, °F||Btu/(ft h °F)|
|Temperature, °C||J/(kg °C)||Temperature, °F||Btu/(lb °F)|
|Temperature, °C||Per °C||Temperature, °F||Per °F|
|Temperature, °C||μΩm||Temperature, °F||μΩin.|
|Temperature, °C||MPa||Temperature, °F||ksi|
Hot working should be carried out at a material temperature of 900-1200°C (1650-2190°F). Hot working of Sandvik 2RK65™ should be followed by rapid cooling in air or water. Subsequent heat treatment should be carried out in accordance with the recommendations given for heat treatment.
The weldability of Sandvik 2RK65TM is good. Welding must be carried out without preheating, and normally there is no need for any subsequent heat treatment. 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.
For Sandvik 2RK65TM, 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 20 25 5 Cu L/ AWS A5.9 ER385 (e.g. Exaton 20.25.5.LCu)
ISO 3581 E 20 25 5 Cu N L R/ AWS A5.4 E385-16 (e.g. Exaton 20.25.5.LCuR)
The machining of Sandvik 2RK65™, 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 40-45%, when turning Sandvik 2RK65™ 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.