304L Stainless Steel: Composition and Key Characteristics
304L stainless steel, also known as AISI 304L, 1.4307, or X2CrNi18-9, belongs to the austenitic stainless steel family. While similar to standard 304 stainless steel (1.4301), its lower carbon content provides superior performance, particularly in welded applications where resistance to intergranular corrosion is crucial.
Key Properties:
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Corrosion Resistance:
Excellent corrosion resistance (PREN value between 17.5-21.1) with maintained intergranular corrosion resistance in welded conditions. Not suitable for seawater or chloride-rich environments.
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Mechanical Properties:
Moderate mechanical strength with tensile strength ranging 500-700 N/mm², hardness ≤ 215 HB, and density of 7.9 kg/dm³ (at 20°C).
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Temperature Performance:
Suitable for cryogenic applications and stable operation up to 550°C.
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Weldability:
Excellent welding characteristics compatible with most common methods.
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Magnetic Properties:
Essentially non-magnetic (μr ≤ 1.3).
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Machinability:
Good polishability with moderate machinability, suitable for cold forming processes.
International Designations:
|
Standard
|
Designation
|
|
EN
|
1.4307
|
|
EN Short Name
|
X2CrNi18-9
|
|
AISI
|
304L
|
|
JIS
|
SUS304L
|
|
UNS
|
S30403
|
|
BS
|
304S11
|
Chemical Composition (DIN EN 10088-3 Standard):
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Element
|
Content (%)
|
|
Carbon (C)
|
≤ 0.03
|
|
Chromium (Cr)
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17.5-19.5
|
|
Nickel (Ni)
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8.0-10.5
|
|
Manganese (Mn)
|
≤ 2.00
|
|
Silicon (Si)
|
≤ 1.00
|
|
Phosphorus (P)
|
≤ 0.045
|
|
Sulfur (S)
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≤ 0.03
|
|
Nitrogen (N)
|
≤ 0.10
|
Physical and Mechanical Properties
Physical Characteristics:
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Magnetism: Weakly magnetic
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Density: 7.9 kg/dm³
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Thermal Conductivity (20°C): 15 W/(m·K)
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Electrical Resistivity: 0.73 Ω·mm²/m (room temperature)
Mechanical Properties:
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Hardness: ≤ 215 HB
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Yield Strength (Rp0.2): ≥ 175 MPa
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Tensile Strength (Rm): 500-700 MPa
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Elongation (A): ≥ 45% (longitudinal, ≤ 160 mm)
High-Temperature Performance:
|
Temperature (°C)
|
Rp1.0 (MPa)
|
Rp0.2 (MPa)
|
|
100
|
180
|
145
|
|
200
|
145
|
118
|
|
300
|
127
|
100
|
|
400
|
116
|
89
|
|
500
|
109
|
81
|
|
550
|
108
|
80
|
Processing and Fabrication
Welding:
304L demonstrates excellent weldability using common methods like arc or TIG welding, though gas welding and submerged arc welding are not recommended. While filler material isn't typically required, AISI 308L (1.4316) can be used when necessary. Welding doesn't compromise its intergranular corrosion resistance.
Forging:
The material shows good forgeability for both open-die and closed-die forging. Recommended procedure:
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Heat to 1150-1180°C
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Forge between 950-1180°C
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Rapid cool in air or water
Heat Treatment:
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Solution Annealing:
Heat to 1000-1100°C followed by air or water cooling
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Hot Forming:
Process between 1200-900°C with subsequent air cooling
Cold Working:
304L accommodates cold forming processes including cold heading (per DIN 10263-5 standard), making it suitable for fastener production.
Corrosion Resistance Analysis
304L offers high natural corrosion resistance (PREN 17.5-21.1) with its low carbon content preventing chromium carbide formation and subsequent chromium depletion. This grants immunity to intergranular corrosion in non-saline and steam environments. It resists:
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Up to 10% formic acid at room temperature
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Up to 1% sulfuric acid
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Up to 7% nitric acid
However, chloride-containing environments (seawater, swimming pools) may induce pitting corrosion.
Application Spectrum
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Automotive:
Exhaust systems, structural components
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Chemical Processing:
Storage tanks, piping, reactors
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Construction:
Structural elements, architectural features
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Food Processing:
Equipment, storage vessels
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Aerospace:
Aircraft components, engine parts
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General Engineering:
Mechanical components, fasteners
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