Sandvik 3R12: High-Performance Austenitic Stainless Steel

Sandvik 3R12 is used for a wide range of industrial applications. Typical examples are: heat exchangers, condensers, pipelines, cooling and heating coils in the chemical, petrochemical, fertilizer, pulp and paper and nuclear power industries, as well as in the production of pharmaceuticals, foods and beverages.

Approvals: JIS Approval for Stainless Steel Tubes

Annealing after cold bending is not normally necessary, but this point must be decided with regard to the degree of bending and the operating conditions. Heat treatment, if any, should take the form of stress relieving or solution annealing, see under 'Heat treatment'.

General corrosion: Sandvik 3R12 has good resistance in

Sandvik 3R12 has better resistance than normal type ASTM TP304 to oxidizing agents, such as nitric acid. The Figure on the right side of the datasheet shows isocorrosion in nitric acid for Sandvik 3R12.

Intergranular corrosion: Sandvik 3R12 has a low carbon content and therefore better resistance to intergranular corrosion than steels of type ASTM TP304.

The TTC-diagram, attached on the right side of the datasheet, which shows the result of testing for 24 h in boiling Strauss solution (12% sulfuric acid, 6% copper sulfate) confirms the superior resistance of Sandvik 3R12. This is an advantage in complicated welding operations.

The good resistance against intergranular attack of Sandvik 3R12 is also demonstrated in the Huey test (boiling in 65% nitric acid for 5x48 h). A maximum corrosion rate of 0.40 mm/year in the annealed condition and 0.60 mm/year in the sensitized (675°C (1275ᵒF)) condition can be met.

Sandvik 3R12 with its controlled and low impurity level, shows better results than ordinary ASTM TP304L or TP321.

Pitting and crevice corrosion: The steel may be sensitive to pitting and crevice corrosion even in solutions of relatively low chloride content. Molybdenum-alloyed steels have better resistance improves with increasing molybdenum content.

Stress corrosion cracking: Austenitic steels are susceptible to stress corrosion cracking (SCC). This may occur at temperatures above about 60°C (140°F) if the steel is subjected to tensile stresses and at the same time comes into contact with certain solutions, particularly those containing chlorides. Such service conditions should therefore be avoided. Conditions when plants are shut down must also be considered, as the condensates which are then formed can develop conditions that leads to both stress corrosion cracking (SCC) and pitting.

In applications demanding high resistance to stress corrosion cracking (SCC) we recommend the duplex (austenitic-ferritic) steel Sandvik SAF 2304.

Gas corrosion: Sandvik 3R12 can be used in

Creep behavior should also be taken into account when using the Sandvik 3R12 in the creep range.

In flue gases containing sulfur, the corrosion resistance is reduced. In such environments the steel can be used at temperatures up to 600-750°C (1110-1380°F) depending on service conditions. Factors to consider are whether the atmosphere is oxidizing or reducing, i.e. the oxygen content, and whether impurities such as sodium and vanadium are present.

Tubes in Sandvik 3R12 are normally delivered in heat treated condition. If additional heat treatment is needed after further processing the following is recommended.

Stress relieving: 850-950°C (1560-1740°F), cooling in air.

Solution annealing: 1000-1100°C (1830-2010°F), rapid cooling in air or water.

Hot bending is carried out at 1100-850°C (2010-1560°F) and should be followed by solution annealing.

Forms of supply:

Seamless tube and pipe in Sandvik 3R12 is supplied in dimensions up to 260 mm (10.2 in.) outside diameter in the solution-annealed and white-pickled condition or solution annealed by a bright-annealing process. U-bent tubes can be supplied on request.

The weldability of Sandvik 3R12 is good. Welding must be carried out without preheating and subsequent heat treatment is normally not required. 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 3R12, heat input of <2.0 kJ/mm and interpass temperature of <150°C (300°F) are recommended.

Recommended filler metals

• TIG/GTAW or MIG/GMAW welding
  • ISO 14343 S 19 9 L / AWS A5.9 ER308L (e.g. Exaton 19.9.L)
• MMA/SMAW welding
  • ISO 3581 E 19 9 L R / AWS A5.4 E308L-17(e.g. Exaton 19.9.LR)
  • ISO 14343 S 19 9 L / AWS A5.9 ER308L (e.g. Exaton 19.9.L) wire or strip electrodes are recommended for overlay welding of tube sheets and high-pressure vessels in cases where corrosion resistance, equal to that of Sandvik 3R12, is required.