Products
/ Stainless Steel Grade 304 |
Chemical
Formula
Fe, <0.08% C, 17.5-20%
Cr, 8-11% Ni, <2% Mn, <1% Si, <0.045% P,
<0.03% S |
Background |
Grade
304 is the standard "18/8" stainless; it is
the most versatile and most widely used stainless steel,
available in a wider range of products, forms and finishes
than any other. It has excellent forming and welding
characteristics. The balanced austenitic structure of
Grade 304 enables it to be severely deep drawn without
intermediate annealing, which has made this grade dominant
in the manufacture of drawn stainless parts such as
sinks, hollow-ware and saucepans. For these applications
it is common to use special "304DDQ" (Deep
Drawing Quality) variants. Grade 304 is readily brake
or roll formed into a variety of components for applications
in the industrial, architectural, and transportation
fields. Grade 304 also has outstanding welding characteristics.
Post-weld annealing is not required when welding thin
sections.
Grade
304L, the low carbon version of 304, does not require
post-weld annealing and so is extensively used in heavy
gauge components (over about 6mm). Grade 304H with its
higher carbon content finds application at elevated
temperatures. The austenitic structure also gives these
grades excellent toughness, even down to cryogenic temperatures. |
Key
Properties |
These
properties are specified for flat rolled product (plate,
sheet and coil) in ASTM A240/A240M. Similar but not
necessarily identical properties are specified for other
products such as pipe and bar in their respective specifications.
Composition
Typical
compositional ranges for grade 304 stainless steels
are given in table 1.
Table
1. Composition ranges for 304 grade stainless steel
Grade |
C |
Mn
|
Si |
P |
S |
Cr |
Mo |
Ni |
N |
304 |
min.
max.
|
-
0.08
|
-
2.0
|
-
0.75
|
-
0.045
|
-
0.030
|
18.0
20.0
|
- |
8.0
10.5
|
-
0.10
|
304L |
min.
max.
|
-
0.030
|
-
2.0
|
-
0.75
|
-
0.045
|
-
0.030
|
18.0
20.0
|
- |
8.0
12.0
|
-
0.10
|
304H |
min.
max.
|
0.04
0.10
|
-
2.0
|
-
0.75
|
-0.045 |
-
0.030
|
18.0
20.0
|
- |
8.0
10.5
|
- |
Mechanical
Properties
Typical
mechanical properties for grade 304 stainless steels
are given in table 2.
Table
2. Mechanical properties of 304 grade stainless steel
Grade |
Tensile Strength (MPa) min |
Yield Strength 0.2% Proof (MPa) min |
Elongation (% in 50mm) min |
Hardness |
Rockwell B (HR B) max |
Brinell (HB) max |
304 |
515 |
205 |
40 |
92 |
201 |
304L |
485 |
170 |
40 |
92 |
201 |
304H |
515 |
205 |
40 |
92 |
201 |
304H also has a requirement for a grain size of
ASTM No 7 or coarser. |
Physical
Properties
Typical
physical properties for annealed grade 304 stainless
steels are given in table 3.
Table
3. Physical properties of 304 grade stainless steel
in the annealed condition
Grade |
Density (kg/m3) |
Elastic Modulus (GPa) |
Mean Coefficient of Thermal Expansion (mm/m/°C)
|
Thermal Conductivity (W/m.K) |
Specific Heat 0-100°C (J/kg.K)
|
Electrical Resistivity (nW.m)
|
0-100°C |
0-315°C |
0-538°C |
at 100°C |
at 500°C |
304/L/H |
8000 |
193 |
17.2 |
17.8 |
18.4 |
16.2 |
21.5 |
500 |
720 |
Grade
Specification Comparison
Approximate
grade comparisons for 304 stainless steels are given
in table 4.
Table
4. Grade specifications for 304 grade stainless steel
Grade |
UNS No |
Old British |
Euronorm |
Swedish SS |
Japanese JIS |
BS |
En |
No |
Name |
304 |
S30400 |
304S31 |
58E |
1.4301 |
X5CrNi18-10 |
2332 |
SUS 304 |
304L |
S30403 |
304S11 |
- |
1.4306 |
X2CrNi19-11 |
2352 |
SUS 304L |
304H |
S30409 |
304S51 |
- |
1.4948 |
X6CrNi18-11 |
- |
- |
These comparisons are approximate only. The list
is intended as a comparison of functionally similar
materials not as a schedule of contractual
equivalents. If exact equivalents are needed original
specifications must be consulted. |
Possible
Alternative Grades
Possible
alternative grades to grade 304 stainless steels are
given in table 5.
Table
5. Possible alternative grades to 304 grade stainless
steel
Grade |
Why it might be chosen instead of 304 |
301L |
A higher work hardening rate grade is required
for certain roll formed or stretch formed components.
|
302HQ |
Lower work hardening rate is needed for cold forging
of screws, bolts and rivets. |
303 |
Higher machinability needed, and the lower corrosion
resistance, formability and weldability are acceptable.
|
316 |
Higher resistance to pitting and crevice corrosion
is required, in chloride environments |
321 |
Better resistance to temperatures of around 600-900°C
is needed…321 has higher hot strength.
|
3CR12 |
A lower cost is required, and the reduced corrosion
resistance and resulting discolouration are acceptable.
|
430 |
A lower cost is required, and the reduced corrosion
resistance and fabrication characteristics are
acceptable. |
Corrosion
Resistance
Excellent
in a wide range of atmospheric environments and many
corrosive media. Subject to pitting and crevice corrosion
in warm chloride environments, and to stress corrosion
cracking above about 60°C. Considered resistant to potable
water with up to about 200mg/L chlorides at ambient
temperatures, reducing to about 150mg/L at 60°C.
Heat
Resistance
Good
oxidation resistance in intermittent service to 870°C
and in continuous service to 925°C. Continuous use of
304 in the 425-860°C range is not recommended if subsequent
aqueous corrosion resistance is important. Grade 304L
is more resistant to carbide precipitation and can be
heated into the above temperature range.
Grade
304H has higher strength at elevated temperatures so
is often used for structural and pressure-containing
applications at temperatures above about 500°C and up
to about 800°C. 304H will become sensitised in the temperature
range of 425-860°C; this is not a problem for high temperature
applications, but will result in reduced aqueous corrosion
resistance.
Heat
Treatment
Solution
Treatment (Annealing) - Heat to 1010-1120°C and cool
rapidly. These grades cannot be hardened by thermal
treatment.
Welding
Excellent
weldability by all standard fusion methods, both with
and without filler metals. AS 1554.6 pre-qualifies welding
of 304 with Grade 308 and 304L with 308L rods or electrodes
(and with their high silicon equivalents). Heavy welded
sections in Grade 304 may require post-weld annealing
for maximum corrosion resistance. This is not required
for Grade 304L. Grade 321 may also be used as an alternative
to 304 if heavy section welding is required and post-weld
heat treatment is not possible.
Machining
A
"Ugima" improved machinability version of
grade 304 is available in bar products. "Ugima"
machines significantly better than standard 304 or 304L,
giving higher machining rates and lower tool wear in
many operations.
Dual
Certification
It
is common for 304 and 304L to be stocked in "Dual
Certified" form, particularly in plate and pipe.
These items have chemical and mechanical properties
complying with both 304 and 304L specifications. Such
dual certified product does not meet 304H specifications
and may be unacceptable for high temperature applications. |
Applications
- Typical
applications include:
- Food
processing equipment, particularly in beer brewing,
milk processing & wine making.
- Kitchen
benches, sinks, troughs, equipment and appliances
- Architectural
panelling, railings & trim
-
Chemical containers, including for transport
- Heat
Exchangers
-
Woven or welded screens for mining, quarrying &
water filtration
- Threaded
fasteners
-
Springs
|
|
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