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Type 309 and 309S Stainless Steels
Description
 Type 309 (UNS S 30900) and 309S (UNS S 30908) are austenitic chromium-nickel stainless steels widely used for elevated temperature service. They have a good combination of oxidation resistance and corrosion-resisting properties. They are essentially nonmagnetic when annealed and become slightly magnetic when cold worked.

Product Forms
Ingots, Slabs, Hot bands, Sheet, Strip

Typical Applications

  • Aircraft heaters
  • Annealing boxes
  • Chemical processing equipment
  • Conveyor parts
  • Dryers
  • Dyehouse equipment
  • Furnace parts
  • Heat exchangers
  • Heat treating equipment
  • Oil burner parts
  • Paper mill equipment
  • Recuperators
  • Skid rails
Chemical Composition
Carbon Manganese Silicon Chromium Nickel
T309 0.20 max.
T309S 0.08 max.		 2.00
max.		 1.00
max.		 24.00/
26.00		 19.00/
22.00

Typical Mechanical Properties
Finish/
Condition		 Yield
Strength
psi		 Tensile
Strength
psi		 Elongation
in 2 in.,
%		 Hardness
Rockwell
B
No. 1/2D Finish,
annealed		 44,000 85,000 46 81
No. 2/2B Finish,
skin passed		 47,000 88,000 46 85

Processing

  • Annealing
    Cool rapidly from 1900-2050°F. Air cooling from annealing temperatures may be employed for light sections, otherwise water quenching is necessary.
  • Hardening
    These grades can be hardened ony by cold work. See table of Typical Mechanical Properties.
  • Stress Relieving
     The recommended temperature range for stress relieving is 400-750°F.

Hot Working

  • Initial forging and pressing temperature--2050-2250°F.
  • Finishing temperature--1700°F.

Forming
 These grades can be formed into most desired shapes. However, since they work harden, an anneal should precede and follow each severe cold forming operation.

Physical Properties
Density
lb./cu. in.		 Modulus of
Elasticity
in Tension
x 10^6, psi		 Specific
Heat
Btu/°F/lb		 Thermal
Conductivity
Btu/hr/ft^2/ft/		 Mean Coefficient
of Thermal Expansion
per °F(x 10^-6)		 Melting
Point
Range		 Electrical
Resistivity
microohn-cm
32-212 °F °F °F °F @ 70 °F
0.29 29.0 0.12 212 932 32-212 32-600 32-1000 32-1200 2550/
2650		 78
9.0 10.8 8.3 9.3 9.6 10.0

Welding
These grades are usually welded by the electric arc or gas fusion processes. Type 309 or Type 309Cb filler metal or electrodes are used.

Corrosion
Types 309 and 309S have good general corrosion resistance. Type 309S (0.08 max. C) is generally used when corrosion resistance in the as-welded condition is important. Type 309 has superior corrosion resistance to Types 302 and 304 in various chemical media.

Oxidation
For continuous service, the maximum recommended temperature is 2000°F, and for intermittent service, 1800°F.
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