Stainless Steel

Stainless Steel - Grade 321

CS 321 Technical Data

CS 321 is a titanium-stabilised version of CS 304, used in particular applications within the sensitizing temperature range. Its resistance to sensitization, coupled with its higher strength at high temperature makes it suitable in application where CS 304 will become sensitized, or where CS 304L has insufficient hot strength. It is not subject to weld decay (intergranular corrosion) when exposed to mildly corrosive environments. However, welded CS 321 must never be used in highly oxidising environments as it is liable to 'Knife-line' attack.

Typical Applications

CS 321 is today used almost exclusively for service within the sensitizing temperature range (450-850oC). In welded ambient temperature applications it has been replaced by CS 304L. Some typical areas of application are:
Furnace components.
Superheater and afterburner parts.
Compensators and expansion bellows.

Chemical Composition (ASTM A240)

  • SX Analysis
  • Typical
  • C
  • 0.08
    max
  • 0.06
  • Mn
  • 2.0
    max
  • 1.2
  • P
  • 0.045
    max
  • 0.020
  • S
  • 0.030
    max
  • 0.020
  • Si
  • 1.0
    max
  • 0.5
  • Cr
  • 17.0 -
    19.0
  • 17.5
  • Ni
  • 9.0-
    12.0
  • 9.4
  • Ti
  • 5X%C min
    0.5 max
  • 0.48

Typical Properties in the Annealed Condition

The properties quoted in this publication are typical of mill products. Unless otherwise indicated they should not be regarded as guaranteed minimum values for specification purposes.

1. Mechanical Properties at Room Temperature

  • Tensile Strength, MPa
  • Proof Strength, 02%, MPa
  • Elongation (Percent in L0=5.65 S0
  • Hardnees (Brinell)
  • Endurance (Fatigue) limit, MPa
  • Typical
  • 580
  • 280
  • 60
  • 163
  • 260
  • Minimum
  • 515
  • 205
  • 40
  • -
  • -

2. Properties at Elevated Temperatures
Short Time Elevated Temperature Tensile Strength

  • Temperature, °C
  • Tensile Strength, MPa
  • 600
  • 390
  • 650
  • 329
  • 700
  • 280
  • 750
  • 230
  • 800
  • 190
  • 850
  • 140

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

  • Time
  • 10 000 h
  • 100 000h
  • Temperature °C
  • Stress MPa
  • Stress MPa
  • 550
  • 180
  • 120
  • 600
  • 100
  • 80
  • 650
  • 70
  • 50
  • 700
  • 40
  • 25
  • 800
  • 10
  • 5

Creep Rupture Stress

  • Time
  • 1 000 h
  • 10 000 h
  • 100 000h
  • Temperature °C
  • Stress MPa
  • Stress MPa
  • Stress MPa
  • 500
  • 270
  • 240
  • 200
  • 600
  • 180
  • 130
  • 90
  • 650
  • 140
  • 90
  • 50
  • 700
  • 70
  • 50
  • 15
  • 800
  • 30
  • 10
  • 5

Recommended Maximum Service Temperature
(Oxidising Conditions)

Continuous Service 950oC
Intermittent Service 870oC

Thermal Processing
1. Annealing Heat from 1050 to 1150oC and cool in air. This ensures maximum ductility of the steel.
2. Stress Relieving CS 321 can be stress-relief annealed within the sensitization temperature range
450-800oC without carbide precipitation occurring, thus avoiding the possibility of intergranular corrosion.
3. Hot working
Initial forging and pressing temperature: 1150 - 1250oC
Finishing temperature: 950oC

Note: Soaking times to ensure uniformity of temperature are up to 12 times that required for carbon steel. Care must be exercised with this grade, and long soaking times to ensure even distribution of carbides should be employed. The initial reductions must be light to allow dispersion of carbides in the flow pattern during forging.

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