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Summary
SX 321 is a titanium-stabilised version of SX 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 SX 304 will become sensitized, or where SX 304L
has insufficient hot strength. It is not subject
to weld decay (intergranular corrosion) when exposed
to mildly corrosive environments. However,
welded SX 321 must never be used in highly oxidising
environments as it is liable to 'Knife-line' attack.
Typical
Applications
SX 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In welded ambient temperature applications it has been
replaced by SX 304L. Some typical areas of
application are:
Furnace components.
Superheater and afterburner parts.
Compensators and expansion bellows.
Chemical
Composition (ASTM A240)
|
|
C
|
Mn
|
P
|
S
|
Si
|
Cr
|
Ni
|
Ti
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|
SX
Analysis
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0.08
max
|
2.0
max
|
0.045
max
|
0.030
max
|
1.0
max
|
17.0
- 19.0
|
9.0
- 12.0
|
5X%C
min
0.5 max
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|
Typical
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0.06
|
1.2
|
0.020
|
0.020
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0.5
|
17.5
|
9.4
|
0.48
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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
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|
Typical
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Minimum
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|
Tensile
Strength, MPa
|
580
|
515
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Proof
Stress (0.2 % offset), MPa
|
280
|
205
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|
Elongation
(Percent in Lo = 5.65 So)
|
60
|
40
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|
Hardness
(Brinell)
|
163
|
-
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|
Endurance
(fatigue) limit, MPa
|
260
|
-
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2.
Properties at Elevated Temperatures
Short Time Elevated Temperature Tensile Strength
|
Temperature,
oC
|
600
|
650
|
700
|
750
|
800
|
850
|
|
Tensile
Strength, MPa
|
390
|
329
|
280
|
230
|
190
|
140
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Creep
data
Stress to develop a creep rate of 1% in the indicated
time at the indicated temperature.
|
Time
|
Temperature
oC
|
550
|
600
|
650
|
700
|
800
|
|
10
000 h
|
Stress
MPa
|
180
|
100
|
70
|
40
|
10
|
|
100
000 h
|
Stress
MPa
|
120
|
80
|
50
|
25
|
5
|
Creep
Rupture Stress
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Time
|
Temperature
oC
|
500
|
600
|
650
|
700
|
800
|
|
1
000 h
|
Stress
MPa
|
270
|
180
|
140
|
70
|
30
|
|
10
000 h
|
Stress
MPa
|
240
|
130
|
90
|
50
|
10
|
|
100
000 h
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Stress
MPa
|
200
|
90
|
50
|
15
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5
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Recommended
Maximum Service Temperature
(Oxidising Conditions)
Continuous
Service
950oC
Intermittent
Service
870oC
Thermal
Processing
-
Annealing
Heat from 1050 to 1150oC and
cool in air. This ensures maximum ductility
of the steel.
-
Stress
Relieving SX 321 can be stress-relief annealed
within the sensitization temperature range 450-800oC
without carbide precipitation occurring, thus
avoiding the possibility of intergranular
corrosion.
-
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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