Type 309S (UNS S30908/1.4833)

  • Machinability is similar to SS 304
  • High heat resistance.
  • Good corrosion resistance.
  • Welding is not recommended.
  • Non-responsive to heat treatments.
  • No oxyacetylene welding.
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The SS 309S is another high-alloy steel with heavy chromium and nickel content. Due to these characteristics, the steel alloy becomes highly resistive to corrosion and rust, and it also becomes heatproof.

The steel alloy exhibits good strength at high as well as room temperature. 309S is slightly different from the 309 SS just because it has low carbon content and forms less carbide precipitation. Therefore, it is an excellent choice for welding.

Common Names:

Other names of stainless steel 309S are UNS S30908, and 2.4660.

Executive Standards:

  • UNS S30900/S30908
  • FeMi35Cr20Cu4Mo2
  • DIN: 2.4660
  • AMS 5650
  • AMS 5574
  • AMS 5523
  • ASTM A240
  • ASTM A167
  • ASTM A213
  • ASTM A312
  • ASTM A249
  • ASTM A276
  • ASTM A314
  • ASTM A511
  • ASTM A554
  • ASTM A580
  • ASTM A473
  • ASTM A813
  • ASTM A814
  • ASTM A479
  • ASTM/ASME: UNS S30900/S30908
  • EURONORM: FeMi35Cr20Cu4Mo2
  • DIN: 2.4660

Chemical Properties:


Mechanical Properties:

Ultimate tensile strength620 MPa (89900 psi)
Yield tensile strength (0.2%)310 MPa (45000 psi)
Izod impact120 – 165 J( 88.5 – 122 ft-lb)
Modulus of elasticity200 GPa (29000 Ksi)
Shear modulus77 GPa (11200 Ksi)
Poisson’s ratio0.3
Elongation at break (in 50 mm)45%
Hardness Brinell (Knoop) (RB) (Vickers)147 (164) (85) (186)

Physical Properties:

The density of SS Type 309S is 8.00 g/cm3 (0.289 lb/in3).

Key Features:

  • Its melting range is 2500F to 2590F.
  • Thermal conductivity is between 0C to 100C (32F to 212F) is 15.6 W/m-K (108 BTU-in/hr-ft2-F).
  • Thermal expansion coefficient: At 20C to 815C is 14.4µm/mC
  • Lower content of alloy than Grade 2205 stainless steel
  • Solutions annealing necessary at 1020C to 1100C

Product Forms Available:

  • Coils.
  • Pickled coils.
  • Strips
  • Plates
  • Sheets


  • Salt pots.
  • Baffle plates and salt pots.
  • Thermo wells.
  • Furnace equipment.
  • Annealing boxes.
  • Energy conversion plants.
  • Engineering industry.
  • Non-ferrous industries including Iron, and steel.
  • Cement industry.

Possible Alternative Grades:

  • Type 2205 – Need for high-temperature strength, not interannual corrosion.
  • Type 316L – A mid-high temperature (@ 600C) environment is present only.
  • Type 904L – A mid-high temperature (@ 800C) environment is present only.


  • Is the SS 309S weldable?

This steel has very good weldability, and gas shielded welding produces the best results

  • What is the machinability of SS 309S?

The SS 309S is very similar to SS 304/L, and it is very high like most austenitic steels.

  • How to heat-treat the SS 309S?

Like most of the austenitic steels, the SS 309S is unresponsive to heat treatments. Therefore, you need to do cold work to reduce its internal stress.

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