904L stainless steel is a high-alloy (nickel, molybdenum, copper), low-carbon austenitic stainless steel designed for:
• Excellent corrosion resistance in aggressive environments.
• High resistance to reducing acids, particularly sulfuric acid.
• High resistance to stress corrosion cracking and chloride corrosion.
Non-magnetic under all conditions, 904L maintains excellent toughness even at cryogenic temperatures and excellent weldability and formability.
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Chemical composition (%)

Element Min (%) Max (%)
Carbon (C) – 0.020
Manganese (Mn) – 2.00
Silicon (Si) – 1.00
Phosphorus (P) – 0.045
Sulfur (S) – 0.035
Chromium (Cr) 19.0 23.0
Molybdenum (Mo) 4.0 5.0
Nickel (Ni) 23.0 28.0
Copper (Cu) 1.0 2.0
Nitrogen (N) – 0.10
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Mechanical properties

Property Value
Tensile Strength (UTS) ≥490 MPa
Proof Strength 0.2% ≥220 MPa
Elongation (on 50 mm) ≥35%
Rockwell Hardness B (HRB) ≤90
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Physical properties

(annealed state)
Property Value
Density 8000 kg/m³
Modulus of elasticity 200 GPa
Coefficient of thermal expansion (0–100°C) 15.0 µm/m/°C
Thermal conductivity 13.0 W/m K
Specific heat (0–100°C) 500 J/kg K
Electrical resistivity 850 nΩ m
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Corrosion resistance

• Very high resistance to corrosion from reducing acids (e.g. sulfuric acid).
• Excellent resistance to chloride corrosion (pitting and cracking).
• Intermediate strength between 316L and super austenitic steels such as 6Mo.
• Improved resistance to stress corrosion cracking compared to traditional austenitic stainless steels.
• Not recommended for aggressive nitric acid.
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Heat resistance

• Good oxidation resistance up to approximately 550°C.
• Above this temperature there is a risk of the formation of fragile phases such as the sigma phase.
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Heat treatments

• Solution annealing: 1090–1175°C, rapid cooling.
• Not hardenable by heat treatment.
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Weldability

• Weldable by all standard methods.
• Sensitive to hot cracking, especially in forced welds.
• No preheating required.
• Post-welding generally not required except in extreme environmental conditions.
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Industrial applications

Ideal for:
• Chemical industry: Treatment of sulfuric, phosphoric, and acetic acids.
• Desalination plants: Heat exchangers, cooling systems.
• Pulp & Paper: Components for paper production.
• Petrochemical and gas plants: Condensers, distillation columns.
• Gas treatment plants: Components resistant to aggressive agents.