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Technical Data Stainless
Steel
Chromium-Nickel Types 302 (S30200), 304
(S30400), 304L (S30403), 305 (S30500)
GENERAL PROPERTIES
Allegheny Ludlum Types 302 (S30200), 304 (S30400),
304L (S30403), and 305 (S30500) stainless steels are
variations of the 18 percent chromium – 8 percent
nickel austenitic alloy, the most familiar and most
frequently used alloy in the
stainless steel family.
These alloys may be considered for a wide variety of
applications where one or more of the following
properties are important:
1. Resistance to corrosion
2. Prevention of product contamination
3. Resistance to oxidation
4. Ease of fabrication
5. Excellent formability
6. Beauty of appearance
7. Ease of cleaning
8. High strength with low weight
9. Good strength and toughness at cryogenic
temperatures
10. Ready availability of a wide range of product forms
Each alloy represents an excellent combination of
corrosion resistance and fabricability. This combination of
properties is the reason for the extensive use of these
alloys which represent nearly one half of the total U.S.
stainless steel production.
Type 304 represents the largest
volume followed by Type 304L. Types 302 and 305 are used in
smaller quantities. The 18-8 stainless steels, principally
Types 304 and 304L, are available in a wide range of product
forms including sheet, strip, foil and plate from Allegheny
Ludlum. The alloys are covered by a variety of
specifications and codes relating to, or regulating,
construction or use of equipment manufactured from these
alloys for specific conditions. Food and beverage,
sanitary,
cryogenic, and pressure-containing applications are
examples. Past users of Type 302 are generally now using
Type 304 since AOD technology has made lower carbon levels
more easily attainable and economical. There are instances,
such as in temper rolled products, when Type 302 is
preferred over Type 304 since the higher carbon permits
meeting of yield and tensile strength requirements while
maintaining a higher level of ductility (elongation) versus
that of the lower carbon T304. Type 304L is used for welded
products which might be exposed to conditions which could
cause intergranular corrosion in service. Type 305 is used
for applications requiring a low rate of work hardening
during severe cold forming operations such as deep drawing.
Other less frequently specified 18-8 stainless steel grades,
such as Type 304N (S30451) and Type 304LN (S30453)
CHEMICAL COMPOSITION Chemistries per ASTM A240 and
ASME SA-240: Percentage by Weight Maximum Unless Range is
Specified 302 304 304L 305 Carbon 0.15 0.08 0.030 0.12
Manganese 2.00 2.00 2.00 2.00 Phosphorus 0.045 0.045 0.045
0.045 Sulfur 0.030 0.030 0.030 0.030 Silicon 0.75 0.75 0.75
0.75 Chromium 17.00 18.00 18.00 17.00 19.00 20.00 20.00
19.00 Nickel 8.00 8.00 8.00 10.50 10.00 10.50 12.00 13.00
Nitrogen 0.10 0.10 0.10 -- Element Data are typical and
should not be construed as maximum or minimum values for
specification or for final design. Data on any particular
piece of material may vary from those shown herein.
RESISTANCE TO CORROSION
General Corrosion
The Types 302, 304, 304L and 305 austenitic stainless
steels provide useful resistance to corrosion on a wide
range of moderately oxidizing to moderately reducing
environments. The alloys are used widely in equipment
and utensils for processing and handling of food,
beverages and dairy products. Heat exchangers,
piping, tanks and other process
equipment in contact
with fresh water also utilize these alloys. Building
facades and other architectural and structural applications
exposed to non-marine atmospheres also heavily
utilize the 18-8 alloys. In addition, a large variety of
applications involve household and industrial chemicals.
The 18 to 19 percent of chromium which these alloys
contain provides resistance to oxidizing environments
such as dilute nitric acid, as illustrated by data for Type
304 below.
Other laboratory data for Types 304 and 304L in the
table below illustrate that these alloys are also resistant
to moderately aggressive organic acids such as
acetic, and reducing acids such as phosphoric. The 9
to 11 percent of nickel contained by these 18-8 alloys
assists in providing resistance to moderately reducing
environments. The more highly reducing environments
such as boiling dilute hydrochloric and sulfuric
acids are shown to be too aggressive for these
materials. Boiling 50 percent caustic is likewise too
aggressive.
*Autogenous weld on base metal sample.
**Types 302 and 305 exhibit similar performance.
20% Acetic Acid, Base Metal 0.1 (<0.01) 0.1 (<0.01)
Welded* 1.0 (0.03) 0.1 (<0.01)
45% Formic Acid, Base Metal 55 (1.4) 15 (0.4)
Welded* 52 (1.3) 19 (0.5)
10% Sulfamic Acid, Base Metal 144 (3.7) 50 (1.3)
Welded* 144 (3.7) 57 (1.4)
1% Hydrochloric, Base Metal 98 (2.5) 85 (2.2)
Welded 112 (2.8) 143 (3.6)
20% Phosphoric Acid, Base Metal <1.0 (<0.03) -- --
Welded <1.0 (<0.03) -- --
65% Nitric Acid, Base Metal 9.2 (0.2) 8.9 (0.2)
Welded 9.4 (0.2) 7.4 (0.2)
10% Sulfuric Acid, Base Metal 445 (11.3) 662 (16.8)
Welded 494 (12.5) 879 (22.3)
50% Sodium Hydroxide, Base Metal 118 (3.0) 71 (1.8)
Welded 130 (3.3) 87 (2.2)
General Corrosion in Boiling Chemicals
Corrosion Rate, Mils/Yr (mm/a)
Boiling
Environment
Type 304** Type 304L
% Nitric Acid
Temperature
°F (°C)
Corrosion Rate
Mils/Yr (mm/a)
10 300 (149) 5.0 (0.13)
20 300 (149) 10.1 (0.25)
30 300 (149) 17.0 (0.43)
Technical Data BLUE SHEET
Data are typical and should not be construed as maximum or minimum values
for specification or for final design. Data on any particular piece of material may
vary from those shown herein.
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In some cases, the low carbon Type 304L alloy may
show a lower corrosion rate than the higher carbon
Type 304 alloy. The data for formic acid, sulfamic acid
and sodium hydroxide illustrate this. Otherwise, the
Types 302, 304, 304L and 305 alloys may be considered
to perform equally in most corrosive environments.
A notable exception is in environments sufficiently
corrosive to cause intergranular corrosion of
welds and heat-affected zones on susceptible alloys.
The Type 304L alloy is preferred for use in such media
in the welded condition since the low carbon level
enhances resistance to intergranular corrosion.
Intergranular Corrosion
Exposure of the 18-8 austenitic stainless steels to
temperatures in the 800°F to 1500°F (427°C to 816°C)
range may cause precipitation of chromium carbides
in grain boundaries. Such steels are “sensitized” and
subject to intergranular corrosion when exposed to
aggressive environments. The carbon content of
Types 302, 304, and 305 may allow sensitization to
occur from thermal conditions experienced by autogenous
welds and heat-affected zones of welds. For
this reason, the low carbon Type 304L alloy is preferred
for applications in which the material is put into
service in the as-welded condition. Low carbon
content extends the time necessary to precipitate a
harmful level of chromium carbides, but does not
eliminate the precipitation reaction for material held for
long times in the precipitation temperature range.
Stress Corrosion Cracking
The Type 302, 304, 304L and 305 alloys are the most
susceptible of the austenitic stainless steels to stress
corrosion cracking (SCC) in halides because of their
relatively low nickel content. Conditions which cause
SCC are: (1) presence of halide ions (generally
chloride), (2) residual tensile stresses, and (3) temperatures
in excess of about 120°F (49°C). Stresses
may result from cold deformation of the alloy during
forming, or by roller expanding tubes into tubesheets,
or by welding operations which produce stresses from
the thermal cycles used. Stress levels may be
reduced by annealing or stress relieving heat treatments
following cold deformation, thereby reducing
sensitivity to halide SCC. The low carbon Type 304L
material is the better choice for service in the stress
relieved condition in environments which might cause
intergranular corrosion.
42% Magnesium Base Metal Cracked,
1 to 20 hours
Chloride, Boiling Welded Cracked,
½ to 21 hours
33% Lithium Base Metal Cracked,
24 to 96 hours
Chloride, Boiling Welded Cracked,
18 to 90 hours
26% Sodium Base Metal Cracked,
142 to 1004 hours
Chloride, Boiling Welded Cracked,
300 to 500 hours
40% Calcium Base Metal Cracked,
144 Hours
Chloride, Boiling --
Ambient Base Metal No Cracking
Temperature
Seacoast
Exposure Welded No Cracking
U-Bend (Highly Stressed)
Samples
Halide (Chloride) Stress Corrosion Tests
Test
302, 304, 304L, 305
Intergranular Corrosion Tests
Corrosion Rate, Mils/Yr (mm/a)
302, 304, 305 304L
ASTM A 262
Evaluation Test
Practice B
Base Metal
Welded
Practice E
Base Metal
Welded
Practice A
Base Metal
Welded
20 (0.5)
23 (0.6)
No Fissures on Bend
Some Fissures on
Weld
(unacceptable)
Step Structure
Ditched
(unacceptable)
20 (0.5)
20 (0.5)
No Fissures
No Fissures
Step Structure
Step Structure
Intergranular
Corrosion
Data are typical and should not be construed as maximum or minimum values
for specification or for final design. Data on any particular piece of material may
vary from those shown herein.
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Types 302, 304, 304L, 305 The above data illustrate that various hot chloride
solutions may cause failure after differing lengths of
time. The important thing to note is that failure eventually
occurs under these conditions of chloride presence,
high stresses and elevated temperatures.
Pitting/Crevice Corrosion
The 18-8 alloys have been used very successfully in
fresh waters containing low levels of chloride ion.
Although Type 304 tubing has been used in power
plant surface condenser cooling water with as much
as 1000 ppm chloride, this performance can only
result from careful cleaning of the tubes during use
and care to avoid stagnant waters from remaining in
contact with the tube. Generally, 100 ppm chloride is
considered to be the limit for the 18-8 alloys, particularly
if crevices are present. Higher levels of chloride
might cause crevice corrosion and pitting. For the
more severe conditions of higher chloride levels, lower
pH and/or higher temperatures, alloys with higher
molybdenum content such as Type 316 or AL-6XN®
alloy should be considered. Interestingly, Types 304
and 304L stainless steels pass the 100 hour, 5 percent
neutral salt spray test (ASTM B117) with no rusting or
staining of samples. However, Type 304 building
exteriors exposed to salt mists from the ocean are
prone to pitting and crevice corrosion accompanied by
severe discoloration. The 18-8 alloys are not recommended
for exposure to marine environments.
The reader is invited to consult the Allegheny Ludlum
Technical Center with questions concerning the
suitability of the 18-8 alloys for specific environments.
PHYSICAL PROPERTIES
Density:
0.285 lb/in3 (7.90 g/cm3)
Modulus of Elasticity in Tension:
29 x 106 psi (200 GPa)
Linear Coefficient of Thermal Expansion:
Temperature Range Coefficients
°F °C in/in/°F cm/cm/°C
68 - 212 20 - 100 9.2 x 10-6 16.6 x 10-6
68 - 1600 20 - 870 11.0 x 10-6 19.8 x 10-6
Thermal Conductivity:
The overall heat transfer coefficient of metals is
determined by factors in addition to the thermal
conductivity of the metal. The ability of the 18-8
stainless grades to maintain clean surfaces often
allows better heat transfer than other metals having
higher thermal conductivity. Consult the Allegheny
Ludlum Technical Center (724-226-6300) for further
information.
Specific Heat:
Magnetic Permeability
The 18-8 alloys are generally non-magnetic in the
annealed condition with magnetic permeability values
typically less than 1.02 at 200H. As illustrated below,
permeability values will vary with composition and will
increase with cold work. Type 305 with the highest
nickel content is the most stable of these austenitic
alloys and will have the lowest permeability when cold
worked. The following data are illustrative:
0 1.004 1.005 1.015 1.002
10 1.039 1.009 1.064 1.003
30 1.414 1.163 3.235 1.004
50 3.214 2.291 8.480 1.008
Magnetic Permeability
302 304 304L 305
Percent
Cold Work
Temperature Range
°F °C
Btu/hr·ft·°F W/m·K
212 100 9.4 16.3
932 500 12.4 21.4
°F °C Btu/lb/°F J/kg·K
32 - 212 0 - 100 0.12 500
®Registered Trademark of Allegheny Ludlum Corporation
Technical Data BLUE SHEET
Data are typical and should not be construed as maximum or minimum values
for specification or for final design. Data on any particular piece of material may
vary from those shown herein.
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Electrical Resistivity
68 20 28.3 72
212 100 30.7 78
392 200 33.8 86
752 400 39.4 100
1112 600 43.7 111
1472 800 47.6 121
1652 900 49.6 126
°F °C
Temperature
Microhm-in Microhm-cm
Melting Range
°F °C
2,550 - 2,590 1,399 - 1,421
MECHANICAL PROPERTIES
Room Temperature Mechanical Properties
Minimum mechanical properties for annealed Types
302, 304, 304L and 305 austenitic stainless steel
plate, sheet and strip as required by ASTM specifications
A 240 and ASME specification SA-240 are shown
below.
Minimum Mechanical Properties Required
Property by ASTM A 240, and ASME SA-240
302, 304 304L 305
0.2% Offset
Yield Strength,
psi
MPa
Ultimate Tensile
Strength,
psi
MPa
Percent Elongation in
2 in. or 51 mm
Hardness, Max.,
Brinell
RB
30,000 25,000 30,000
205 170 205
75,000 70,000 75,000
515 485 515
40.0 40.0 40.0
201 201 183
92 92 88
Data are typical and should not be construed as maximum or minimum values
for specification or for final design. Data on any particular piece of material may
vary from those shown herein.
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Types 302, 304, 304L, 305 Effect of Cold Work
Deformation of the 18-8 alloys at room or slightly
elevated temperatures produces an increase in
strength accompanied by a decrease in elongation
value. A portion of this increase in strength is caused
by partial transformation of austenite to martensite
during deformation. As shown by the permeability
data, the Type 302, 304 and 304L alloys are more
prone to martensite formation than the Type 305 alloy.
Strengthening during deformation is, therefore, more
pronounced in the leaner compositions. Among the
18-8 alloys, Type 305 alloy with highest nickel content
exhibits the least amount of work hardening. Typical
data are shown below.
Low and Elevated Temperature Properties
Typical short time tensile property data for low and
elevated temperatures are shown below. At temperatures
of 1000°F (538°C) or higher, creep and stress
rupture become considerations. Typical creep and
stress rupture data are also shown below.
-423 -253 100,000 690 250,000 1725 25
-320 -196 70,000 485 230,000 1585 35
-100 -79 50,000 345 150,000 1035 50
70 21 35,000 240 90,000 620 60
400 205 23,000 160 70,000 485 50
800 427 19,000 130 66,000 455 43
1200 650 15,500 105 48,000 330 34
1500 815 13,000 90 23,000 160 46
Test
Temperature
0.2% Yield
Strength
Tensile
Strength Elongation
°F °C psi psi
Percent
in 2" or
51 mm
(MPa) (MPa)
Technical Data BLUE SHEET
Data are typical and should not be construed as maximum or minimum values
for specification or for final design. Data on any particular piece of material may
vary from those shown herein.
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Impact Resistance
The annealed austenitic stainless steels maintain high
impact resistance even at cryogenic temperatures, a
property which, in combination with their low temperature
strength and fabricability, has led to their use in
handling liquified natural gas and other cryogenic
environments. Typical Charpy V-notch impact data
are shown below.
typically about 35 percent of the tensile strength.
Substantial variability in service results is experienced
since additional variables influence fatigue strength.
As examples – increased smoothness of surface
improves strength, increased corrosivity of service
environment decreases strength.
WELDING
The austenitic stainless steels are considered to be
the most weldable of the high-alloy steels and can be
welded by all fusion and resistance welding processes.
The Types 302, 304, 304L and 305 alloys are
typical of the austenitic stainless steels.
Two important considerations in producing weld joints
in the austenitic stainless steels are: 1) preservation of
corrosion resistance, and 2) avoidance of cracking.
A temperature gradient is produced in the material
being welded which ranges from above the melting
temperature in the molten pool to ambient temperature
at some distance from the weld. The higher the
carbon level of the material being welded, the greater
the likelihood that the welding thermal cycle will result
in the chromium carbide precipitation which is detrimental
to corrosion resistance. To provide material at
the best level of corrosion resistance, low carbon
material (Type 304L) should be used for material put in
service in the welded condition. Alternately, full
annealing dissolves the chromium carbide and restores
a high level of corrosion resistance to the
standard carbon content materials.
Weld metal with a fully austenitic structure is more
susceptible to cracking during the welding operation.
For this reason, Types 302, 304, and 304L alloys are
designed to resolidify with a small amount of ferrite to
minimize cracking susceptibility. Type 305, however,
contains virtually no ferrite on solidification and is more
sensitive to hot cracking upon welding than the other
alloys.
If filler metal is required, Type 308 (20% Cr-11% Ni) is
generally used. This enriched composition avoids
martensite which might otherwise form in multipass
welds. Chemistry is controlled to allow a small amount
of ferrite in the deposit to limit hot cracking tendency.
°F °C
Temperature Charpy V-Notch Energy Absorbed
Foot - pounds Joules
75 23 150 200
-320 -196 85 115
-425 -254 85 115
Fatigue Strength
The fatigue strength or endurance limit is the maximum
stress below which material is unlikely to fail in
10 million cycles in air environment. The fatigue
strength for austenitic stainless steels, as a group, is
Data are typical and should not be construed as maximum or minimum values
for specification or for final design. Data on any particular piece of material may
vary from those shown herein.
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Types 302, 304, 304L, 305 Type 309 (23% Cr – 13.5% Ni) or nickel-base filler
metals are used in joining the 18-8 austenitic alloys to
carbon steel.
HEAT TREATMENT
The austenitic stainless steels are heat treated to
remove the effects of cold forming or to dissolve
precipitated chromium carbides. The surest heat
treatment to accomplish both requirements is the
solution anneal which is conducted in the 1850°F to
2050°F range (1010°C to 1121°C). Cooling from the
anneal temperature should be at sufficiently high rates
through 1500-800°F (816°C – 427°C) to avoid
reprecipitation of chromium carbides.
These materials cannot be hardened by heat treatment.
CLEANING
Despite their corrosion resistance, stainless steels
need care in fabrication and use to maintain their
surface appearance even under normal conditions of
service.
In welding, inert gas processes are used. Scale or
slag that forms from welding processes is removed
with a stainless steel wire brush. Normal carbon steel
wire brushes will leave carbon steel particles in the
surface which will eventually produce surface rusting.
For more severe applications, welded areas should be
treated with a descaling solution such as a mixture of
nitric and hydrofluoric acids and these should be
subsequently washed off.
For material exposed in inland, light industrial or milder
service, minimum maintenance is required. Only
sheltered areas need occasional washing with a
stream of pressurized water. In heavy industrial
areas, frequent washing is advisable to remove dirt
deposits which might eventually cause corrosion and
impair the surface appearance of the stainless steel.
Stubborn spots and deposits like burned-on food can
be removed by scrubbing with a nonabrasive cleaner
and fiber brush, a sponge or pad of stainless steel
wool. The stainless steel wool will leave a permanent
mark on smooth stainless steel surfaces.
Many of the uses of stainless steel involve cleaning or
sterilizing on a regular basis. Equipment is cleaned
with specially designed caustic soda, organic solvent
or acid solutions such as phosphoric or sulfamic acid
(strongly reducing acids such as hydrofluoric or
hydrochloric may be harmful to these stainless steels).
Cleaning solutions need to be drained and stainless
steel surfaces rinsed thoroughly with fresh water.
Design can aid cleanability. Equipment with rounded
corners, fillets and absence of crevices facilitates
cleaning as do smooth ground welds and polished
surfaces.
SURFACE FINISHES A range of surface finishes is
available. These are designated by a series of numbers.
Number 1 Finish – is hot rolled annealed and descaled. It is
available in plate and sheet and is used for functional
applications where a smooth decorative finish is not
important. Number 2D Finish – is a dull finish produced by
cold rolling, annealing and descaling. This finish is
favorable for the retention of lubricants in drawing or
forming operations and is preferred for deep drawn and
formed parts. Number 2B Finish – is a brighter finish than
2D. It is produced much like the 2D finish except that the
final cold rolling is done with smooth polished rolls. This
is a general purpose finish used for all but severe cold
forming. Because it is smoother as produced, it is more
readily polished than 1 or 2D finishes. Number 2BA Finish –
is a very smooth finish produced by cold rolling and bright
annealing. A light pass using highly polished rolls produces
a glossy finish. A 2BA finish may be used for lightly formed
applications where a glossy finish is desired in the as
formed part. Polished finishes – a variety of ground
finishes is available. Technical Data BLUE SHEET Data are
typical and should not be construed as maximum or minimum
values for specification or for final design. Data on any
particular piece of material may vary from those shown
herein. 9 Because special equipment or processes are used to
develop these finishes, not all finishes are available in
the range of products produced by Allegheny Ludlum. Surface
finish requirements should be discussed with Allegheny
Ludlum mill representatives.
SPECIFICATION COVERAGE Because of the extensive use
of these austenitic stainless steels, and their broad
specification coverage, the following list of specifications
is representative, but not complete. In Section II, Part D
of the ASME Boiler and Pressure Vessel Code, Type 304 is
assigned allowable stresses for a variety of product forms
to maximum use temperatures of 1500°F (816°C). Type 304L
coverage includes fewer product forms with lower allowable
stresses to maximum use temperature of 800°F (426°C) while
Types 302 and 305 have very limited coverage. All of the
grades are accepted for use in food preparation and storage
by the National Sanitation Foundation and for contact with
dairy products by the Dairy and Food Industries Supply
Association – Sanitary Standards Committee and are standard
materials used in each industry. Similarly, Types 304 and
304L are standard materials of construction in the brewery
industry.
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