Stainless Steel

Stainless Steel - Grade 309

CS 309 Technical Data

CS 309 is a highly alloyed austenitic stainless steel used for its excellent oxidation resistance, high temperature strength and creep resistance. The lower nickel content of CS309 improves resistance to sulphur attack at high temperatures. It is tough and ductile, and can be readily fabricated and machined. CS 309S is the low-carbon version of CS 309, and is recommended for applications where sensitisation, and subsequent corrosion by high temperature gases or condensates during shutdown may pose a problem.
CS 309 is manufactured to ASTM A 167 and CS 309S to ASTM A240 specifications.

Typical Applications
CS 309 / 309S is used exclusively for its high temperature oxidation resistance. It is common for CS 309, 310 and 321 to be used in the same piece of equipment in the various temperature regions.

Chemical Composition (ASTM A240)

  • SX
  • 309
    309S
  • C
  • 0.20 max
    0.08 max
  • Mn
  • 2.00
    max
  • P
  • 0.045
    max
  • S
  • 0.030
    max
  • Si
  • 1.00
    max
  • Cr
  • 22.0 -
    24.0
  • Ni
  • 12.0 -
    15.0


Typical Properties in the Annealed Condition
The properties quoted in this publication are typical of mill production and unless indicated should not be regarded as guaranteed minimum values for specification purposes.

1. Mechanical Properties at Room Temperature

  • Tensile Strength MPa
  • Proof Stress(0.2% Offset) MPa
  • Elongation (Percent in 50mm)
  • Hardness (Brinell)
  • Endurance (fatigue) limit, MPa
  • SX 309
  • TypicalMinimum
  • 560515
  • 285205
  • 5440
  • 164-
  • 260-
  • SX 309S
  • TypicalMinimum
  • 540515
  • 280205
  • 5440
  • 159-
  • 260-

2. Properties at Elevated Temperatures
The values quoted are those for CS 309
Short Time Elevated Temperature Tensile Stress

  • Temperature
  • Tensile Stress
  • °C
  • MPa
  • 550
  • 440
  • 650
  • 360
  • 750
  • 240
  • 850
  • 150
  • 950
  • 70
  • 1 050
  • 30

Creep Data
Stress to develop a creep rate of 1% in the time indicated at the temperature indicated.

  • Time
  • 10 000 h
  • 100 000h
  • Temperature °C
  • Stress MPa
  • Stress MPa
  • 550
  • 100
  • 75
  • 600
  • 80
  • 50
  • 650
  • 60
  • 30
  • 700
  • 30
  • 20
  • 750
  • 25
  • 10
  • 800
  • 10
  • 5

Creep Rupture Stress

  • Time
  • 1 000 h
  • 10 000 h
  • 100 000h
  • Temperature °C
  • Stress MPa
  • Stress MPa
  • Stress MPa
  • 600
  • 180
  • 150
  • 100
  • 700
  • 90
  • 50
  • 40
  • 800
  • 35
  • 35
  • 20
  • 900
  • 20
  • 10
  • 5
  • 1 000
  • 5
  • 2
  • -

Maximum Recommended Service
Temperature
(Oxidising Conditions)

Continuous 1 100oC
Intermittent 980oC

Thermal Processing
1. Annealing. Heat between 1 050oC and 1 150oC and water quench. This treatment ensures that all carbides are in solution.
2. Stress Relieving 250-400oC for 1 hour.
3. Hot Working
Initial forging and pressure 1 150-1 200oC
Finishing temperature 1 000oC

Note: Soaking times to ensure uniformity of temperature are up to 12times that required for mild and carbon steels.

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