904L is a high-alloy austenitic stainless steel with low carbon content. The grade is intended for use under severe corrosive conditions. It has been application proved over many years and was originally developed to resist corrosion in dilute sulfuric acid. It is standardized and approved for pressure vessel use in several countries. Structurally, 904L is fully austenitic and is less sensitive to precipitation ferrite and sigma phases than conventional austenitic grades with high molybdenum content. Characteristically, due to the combination of relatively high contents of chromium, nickel, molybdenum and copper 904L has good resistance to general corrosion, particularly in sulfuric and phosphoric conditions.
DESIGN FEATURES
Good resistance to pitting and crevice corrosion.
Very good resistance to stress corrosion cracking.
Good resistance to intergranular corrosion.
Good formability and weldability.
Maximum service temperatures of
450 deg.C. (824 deg.F).
TYPICAL APPLICATIONS
Production and transport of sulfuric acid
Metal pickling in sulfuric acid
Production and concentration of phosphoric acid
Use in seawater, brackish water, condensers, heat exchangers and pipe work in general
Paper and allied industries
Gas washing
Chemical and pharmaceutical industries
| Physical Properties of Super Austenitic 904L Alloys in the Annealed Condition at -20°F to +100°F |
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Tensile Strength |
Yield Strength |
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| Alloy |
UNS Designation |
Spec. |
psi |
MPa |
ksi |
psi |
MPa |
ksi |
Elongation in 2 in. (min.) % |
Grain Size Req. |
Max. Hardness |
Modulus of Elasticity (x106 psi) |
Mean Coefficient of Thermal Expansion (IN./IN./°F x 10-6) |
Thermal Conductivity (BTU-in/ ft2-h-°F) |
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| 904L |
N08904 |
A249, A312 |
71,000 |
490 |
71 |
31,000 |
215 |
31 |
35 |
— |
90 Rb |
28 |
8.5 |
79 |
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| 904L |
N08904 |
B673, B674 |
71,000 |
490 |
71 |
31,000 |
215 |
31 |
35 |
— |
— |
— |
8.5 |
79 |
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| Composition of Super Austenitic 904L tubing and pipe |
| Nickel (Ni) |
Chromium (Cr) |
Iron (Fe) |
Carbon (C) Max. |
Nitrogen (N) Max. |
Silicon (Si) Max. |
Sulphur (S) Max. |
Phosphorous (P) Max. |
Molybdenum (Mo) |
Titanium (Ti) Max. |
Aluminum (Al) Max. |
Cobalt (Co) Max. |
Tungsten (W) |
Vanadium (V) Max. |
Copper (Cu) Max. |
Manganese (Mn) Max. |
Niobium (Nb) plus Tantalum |
Other Elements |
| 23.0 – 28.0 |
19.0 – 23.0 |
Bal. |
0.02 |
0.1 |
1 |
0.035 |
0.045 |
4.0 – 5.0 |
— |
— |
— |
— |
— |
1.00 – 2.00 |
2 |
— |
— |
