Sandvik 2RK65 (Billets)

Chemical composition (nominal) %

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.

Sizes and tolerances apply to the rolled/forged condition.

Other products

• Welded tube and pipe
• Seamless tube and pipe
• Wire electrodes and filler wire/rods
• Strip electrodes for surfacing
• Covered electrodes
• Strip, annealed or cold-rolled to different degrees of hardness
• Wire, drawn or ground

Mechanical properties

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)

1 MPa = 1 N/mm²
a) R_p0.2 and R_p1.0 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.

Impact strength

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.

Physical properties

Density: 8.0 g/cm³, 0.29 lb/in³

Corrosion resistance

General corrosion

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 (140^oF). At high temperatures, above about 100^oC, 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.

Hot working

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.

Heat treatment

Billets are delivered in the hot worked condition. The following heat treatment is recommended.

Solution annealing

1050-1150°C (1920-2100°F), followed by quenching in water.

Welding

Sandvik 2RK65 possesses good weldability. Welding should be undertaken without preheating. If welding is correctly performed, there is no need for subsequent heat treatment. The temperature between welding passes should not exceed 150°C (300°F). Suitable methods of fusion welding are manual metal-arc with covered electrodes and gas shielded arc welding, especially the TIG and MIG/MAG methods.

Since the material is intended for use under severely corrosive conditions, welding must be carried out with care and thorough cleaning carried out after welding, to ensure that the weld metal and the heat affected zone will have corrosion properties close to those of the parent metal. Cleaning the joint area with acetone or alcohol before welding is recommended, in order to avoid porosity and fissuring.

Welding should be undertaken with a low heat input, maximum 1.0 kJ/mm. Furthermore, the diameter of electrodes used in manual metal-arc welding should be 2.5 mm (3/32") max., for stock thicknesses up to 6 mm (1/4"), and 3.25 mm (1/8") max., for heavier stock gauges. A stringer bead welding technique is recommended.

Like all austenitic stainless steels, Sandvik 2RK65 has low thermal conductivity and high thermal expansion, which means that welding must be carefully planned in advance to ensure that distortion of the welded joint can be kept under control. If, despite such precautions, it is believed that residual stresses might impair the functioning of the structure, it is recommended that the entire structure is solution annealed. See under heat treatment.

Welding of fully austenitic steels often entails the risk of hot cracking in the weld metal, particularly if the weldment is under constraint. Sandvik 2RK65, however, possesses very high purity, which reduces the risk of such cracking.

We suggest Sandvik 20.25.5.LCu wire as a filler metal for gas shielded arc welding. Sandvik 20.25.5.LCuR covered electrodes are recommended for manual metal-arc welding. Sandvik 27.31.4.LCu or 27.31.4.LCuR can be used to advantage in applications where particularly good pitting resistance is required in the weld metal. When Sandvik 2RK65 is welded to carbon steel, nickel-base filler metals can also be used.

Machining

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.

Applications

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.