Sandvik 3R64: Premium Austenitic Stainless Steel for Superior Corrosion Resistance

Sandvik 3R64 can be used for a wide range of industrial applications where steels of type ASTM 304 and 304L or even ASTM 316L have insufficient corrosion resistance. Typical examples are heat exchangers, condensers, pipelines, cooling and heating coils in the chemical, petrochemical, pulp and paper and food industries.

Owing to its high molybdenum content Sandvik 3R64 possesses improved resistance compared to ASTM 316/316L in a majority of chloride and acidic environments.

General corrosion, Sandvik 3R64 has good resistance in:

The following data illustrate the improved resistance of Sandvik 3R64 vs ASTM 316, although the corrosion rates at the majority of temperatures are unacceptably high for both grades.

Table 1. General corrosion resistance of Sandvik 3R64 and ASTM 316 in boiling formic acid.

Intergranular corrosion: Owing to its low carbon content Sandvik 3R64 possesses a low risk for intergranular corrosion after e.g. welding operations.

Pitting and crevice corrosion: The pitting corrosion resistance of stainless steels is primarily determined by the contents chromium, molybdenum and nitrogen. The Pitting Resistance Equivalent can be used for ranking different stainless steels with regard to their pitting resistance. The PRE number is defined as: PRE = % Cr + 3.3 x % Mo + 16 x % N

Table 2. PRE values for Sandvik 3R64 and some other alloys. Typical values unless otherwise stated

Thus Sandvik 3R64 is resistant against pitting corrosion at higher temperatures and/or higher chloride concentrations than is the case for ASTM 316L.

The same ranking of alloys can be applied for the crevice corrosion resistance. However, crevice corrosion is to be expected at significantly lower temperatures, than is the case for pitting corrosion. Figure 1 demonstrates the better crevice corrosion resistance of Sandvik 3R64 vs. 3R60 (ASTM 316L with 2.6% Mo, EN 1.4435) after 2 months exposure in chloride solutions.

Stress corrosion cracking: Austenitic steels are susceptible to stress corrosion cracking. 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 a chloride content that leads to both stress corrosion cracking and pitting.

In applications demanding high resistance to stress corrosion cracking, austenitic-ferritic steels, such as Sandvik SAF 2304 or Sandvik SAF 2205 are recommended. See data sheets S-1871-ENG or S-1874-ENG.

The tubes are 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), 10-15 min, cooling in air.

Solution annealing: 1000–1100°C (1830–2010°F), 10-30 min, cooling in air or water.

Forms of supply:

Seamless tube and pipe in 3R64 is supplied in dimensions up to 260 mm outside diameter in the solution annealed and white-pickled condition or solution annealed in a bright-annealing process.

Sandvik 3R64 is also supplied in forms of:

Further details concerning sizes and finishes are available on request.

The weldability of Sandvik 3R64 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 3R64, heat input of <1.5 kJ/mm and interpass temperature of <100°C (210°F) are recommended.

Recommended filler metals:

• TIG/GTAW or MIG/GMAW welding
  • ISO 14343 S 19 13 4 L / AWS A5.9 ER317L (e.g. Exaton 19.13.4.L)
• MMA/SMAW welding
  • ISO 3581 E 19 13 4 L R / AWS A5.4 E317L-16 (e.g. Exaton 19.13.4.LR)
  • ISO 14343 S 19 13 4 L / AWS A5.9 ER317L (e.g. Exaton 19.13.4.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 3R64, is required.