904L steel is a highly alloyed austenitic stainless steel (nickel, molybdenum, copper) with low carbon content, designed for:
• Excellent corrosion resistance in aggressive environments.
• High resistance to reducing acids, particularly sulfuric acid.
• High resistance to stress corrosion and chloride corrosion.
Non-magnetic in 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
0.2% Proof Strength ≥220 MPa
Elongation (on 50 mm) ≥35%
Rockwell B Hardness (HRB) ≤90
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Physical Properties

(annealed condition)
Property Value
Density 8000 kg/m³
Modulus of elasticity 200 GPa
Thermal Expansion Coefficient (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 resistance between 316L and super austenitic 6Mo types.
• Improved stress corrosion resistance compared to conventional 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 formation of brittle phases such as 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 with all standard methods.
• Susceptible to hot cracking, especially in constrained welds.
• No preheating required.
• Post-weld treatment generally not required, except under extreme environmental conditions.
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Industrial Applications

Ideal for:
• Chemical industry: Processing 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.