F65/UNS S32906 Stainless Steel

UNS S32906/F65 is a high-alloy duplex (austenitic-ferritic) stainless steel with excellent corrosion resistance in caustic environments and environments with chlorides. In addition, it has somewhat characteristics below:

  • Outstanding resistance to caustic environments, also in the presence of contaminants such as chlorides
  • Good resistance to intergranular corrosion
  • Excellent resistance to pitting and crevice corrosion
  • High resistance to stress corrosion cracking (SCC)
  • Good weldability
  • Very high strength. The proof strength is about three times as high as for conventional austenitic stainless steel.

Chemical Composition:

C Si Mn P S Cr Ni Mo Cu N
≤0.030 0.3 1.0 ≤0.030 ≤0.015 29 7 2.3 ≤0.80 0.35

Mechanical Properties:

  1. At 20°C (68°F):

Wall thickness

 Proof strength Tensile strength Elongation

Rp0.2

 Rm

A

mm

MPa

 ksi MPa ksi

%

min

 min. min. min.

min.

<10

650

 94 800 116

25
≥10 550 80 750 109

25

1 MPa = 1 N/mm2
a) Rp0.2 corresponds to 0.2% offset yield strength.
b) Based on L0 = 5.65 √S0 where L0 is the original gauge length and S0 is the original cross-section area.

     2. At high temperatures:

Temperature Wall thickness Proof strength Tensile strength, Elongation

°C

 mm Rp0.2 Rm A

MPa

 MPa %

min.

 min.

min

100

<10

 550 750

25

≥10

 500 730

25
200 <10 470 720

25

≥10

 430 700

25

300

<10

 450 710

25
≥10 410 690

25

General Corrosion and Microstructure
UNS S32906 demonstrates excellent corrosion resistance properties owing to the high content of alloying elements, low impurity content and control of heat treatment during the production process to ensure the absence of detrimental precipitates and intermetallic phases.

At the same time, its duplex (austenitic-ferritic) structure with a ferrite content in the range of 40-60% determines its microstructure is free of detrimental intermetallic phases.

Intergranular Corrosion
F65/UNS S32906 shows excellent resistance to intergranular corrosion and exceeds compliance with typical norms of either the Huey test (ASTM A262 practice C, 5 x 48h in boiling HNO3) or Streicher testing (ASTM A262 practice B, 120h in boiling H2SO4 + FeSO4).

Available products forms:

Pipe, Tube: ASTM A268, ASTM A789, ASTM A790, ASTM A511, ASME SA268

Plate, Sheet, Coil: ASTM A240

Bar: ASTM A479

Applications:

  • Caustic soda production: the material is suitable for use in piping systems from the cells up to the evaporation plant.
  • It is also an excellent choice for very aggressive conditions, such as the evaporator tubes, in both diaphragm and membrane processes.
  • Alumina production: heat exchanger tubes and piping in the digestion of alumina
  • Environments where high resistance to pitting and crevice corrosion is required