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Summary
SX 304 is the most versatile and the most widely used
of all stainless steels. Its chemical
composition, mechanical properties, weldability and
corrosion/oxidation resistance provide the best
all-round performance stainless steel at relatively
low cost. It also has excellent low temperature
properties and responds well to hardening by cold
working. If intergranular corrosion in the heat
affected zone may occur, it is suggested that SX 304L
be used.
Typical
Applications
SX 304 is used in all industrial, commercial and
domestic fields because of its good corrosion and heat
resisting properties. Some applications include:
-
Tanks
and containers for a large variety of liquids and
solids.
-
Process
equipment in the mining, chemical, cryogenic,
food, dairy and pharmaceutical industries.
Chemical
Composition (ASTM A240)
|
SX
|
oC
|
Mn
|
P
|
S
|
Si
|
Cr
|
Ni
|
|
304
304L
|
0.08
max
0.03 max
|
2.0
max
|
0.045
max
|
0.030
max
|
1.0
max
|
18.0
to
20.0
|
8.0
to 10.50
8.0 - 12.0
|
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
|
|
304
|
304L
|
|
Typical
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Minimum
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Typical
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Minimum
|
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Tensile
Strength, MPa
|
600
|
515
|
590
|
485
|
|
Proof
Strength, (Offset 0.2 %),
MPa
|
310
|
205
|
310
|
170
|
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Elongation
(Percent in 50mm)
|
60
|
40
|
60
|
40
|
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Hardness
(Brinell)
|
170
|
-
|
170
|
-
|
|
Endurance
(fatigue) limit,
MPa
|
240
|
-
|
240
|
-
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2. Properties at elevated
temperatures
All these values refer to 304 only.
304L values are not given because its strength
decreases markedly above 425oC.
Time Elevated Temperature
Tensile Strength
|
Temperature,
oC
|
600
|
700
|
800
|
900
|
1000
|
|
Tensile
Strength, MPa
|
380
|
270
|
170
|
90
|
50
|
Creep data Stress
for a creep rate of 1% in 10 000 h.
|
Temperature,
oC
|
550
|
600
|
650
|
700
|
800
|
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Stress,
MPa
|
120
|
80
|
50
|
30
|
10
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Maximum Recommended Service
Temperature
(Oxidising Conditions)
Continuous
Service
925oC
Intermittent Service
850oC
3.
Properties at Sub-Zero Temperatures
(SX304/304L)
|
Temperature
|
oC
|
-78
|
-161
|
-196
|
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Tensile
Strength
|
MPa
|
1100/950
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1450/1200
|
1600/1350
|
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Proof
Stress (Offset 0.2%)
|
MPa
|
300/180
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380/220
|
400/220
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Impact
Strength (Charpy V-Notch)
|
J
|
180/175
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160/160
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155/150
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4. Corrosion Resistance
Aqueous
As a rough guide the following examples are given for
certain pure acid-water mixtures-
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Temperature
oC
|
20
|
80
|
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Concentration,
% by mass
|
10
20 40
60 80
100
|
10
20 40
60 80
100
|
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Sulphuric
Acid
|
2
2 2
2
1
0
|
2
2 2
2 2
2
|
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Nitric
Acid
|
0
0 0
0
2
0
|
0
0 0
0 1
2
|
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Phosphoric
Acid
|
0
0 0
0
0
2
|
0
0 0
0 1
2
|
|
Formic
Acid
|
0
0 0
0
0
0
|
0
1 2
2 1
0
|
Key:
0 = resistant -
corrosion rate less than 100 mm/year
1 = partly resistant -
corrosion rate 100m to 1000 mm/year
2 = non resistant - corrosion rate
more than 1000 mm/year
4.2 Atmospheric
The performance of SX 304 compared with other metals
in various environments is shown in the following
table. The corrosion rates are based on a 10 year
exposure.
|
Environment
|
Corrosion
Rate (mm/year)
|
|
SX
304
|
Aluminium-3S
|
Mild
Steel
|
|
Rural
|
0.0025
|
0.025
|
5.8
|
|
Marine
|
0.0076
|
0.432
|
34.0
|
|
Marine
Industrial
|
0.0076
|
0.686
|
46.2
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Thermal
Processing
-
Annealing.
Heat from 1010oC
to 1120oC and cool rapidly in air or
water. The best corrosion resistance is
obtained when the final annealing is above 1070oC
and cooling is rapid.
-
Stress
relieving. SX304L
can be stress relieved at 450-600oC for
one hour with little danger of sensitisation.
A lower stress relieving temperature of 400oC
maximum must be used.
-
Hot
working
Initial
forging and pressing:- 1150 to 1260oC
Finishing temperature:- 900 to 925oC
All
hotworking operations should be followed by annealing.
Note:
Soaking times to ensure uniformity of temperature are
longer for stainless steels than for carbon steels -
approximately 12 times.
Cold
Working
SX 304 / 304L being extremely tough and ductile, are
readily fabricated by old working. Typical
operations include bending, forming, deep drawing and
upsetting.
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