Grade dossier
904L Stainless Steel for Aggressive Corrosion Service
A high-nickel, molybdenum- and copper-alloyed austenitic grade developed for demanding process environments, especially where reducing acids and localized corrosion require more margin than 316L.
Identity before substitution
Define the grade, product and condition together
A familiar grade name is not a complete purchase specification. Product form, controlling standard, dimensions, condition, finish, certification and service environment determine whether the delivered material is suitable.
Composition control
ASTM A240/A240M flat-product chemistry
Limits are not heat analysis targets
The table summarizes grade limits commonly used for plate, sheet and strip. Pipe, tube, bar, forgings and cast products can be governed by different specifications. Always place the product standard and edition on the purchase order.
| C | 0.020 max |
|---|---|
| Mn | 2.00 max |
| Si | 1.00 max |
| P | 0.045 max |
| S | 0.035 max |
| Cr | 19.00-23.00 |
| Ni | 23.00-28.00 |
| Mo | 4.00-5.00 |
| Cu | 1.00-2.00 |
| N | 0.10 max |
Properties with context
Minimums, typical indicators and delivered condition
Specified annealed flat-product values
| Tensile strength | 490 MPa min |
|---|---|
| 0.2% yield strength | 220 MPa min |
| Elongation | 35% min |
| Condition | Solution annealed flat product |
Selection indicators
| Density | about 8.0 g/cm3 |
|---|---|
| PRE indicator | about 34-36; not a service limit |
| Corrosion focus | Reducing acids and localized corrosion |
| Cost driver | High nickel and molybdenum content |
Values depend on product form, thickness, test orientation, condition and governing edition. Use the mill test certificate and the purchase specification for acceptance, not a web table alone.
Selection boundary
Where 904L belongs and where to escalate
Grade selection is an environmental decision, not a popularity contest. Review the complete medium, temperature, geometry, fabrication, cleaning and inspection requirements.
Good reasons to evaluate it
Sulfuric and phosphoric acid process equipment after testing
Flue-gas and chemical-processing equipment
Tanks, piping and heat-transfer equipment under an approved specification
Applications requiring an N08904 certificate
Reasons to stop and review
Selection from PRE alone
Unqualified hydrochloric or hydrofluoric acid service
Substitution for nickel alloys without corrosion data
Assuming 904L is immune to chloride crevice corrosion
Fabrication route
Protect properties through cutting, forming and welding
Forming loads and springback require allowance for the high-alloy austenitic grade.
Use dedicated tools and contamination control.
Welding procedures and filler must preserve corrosion performance.
Post-weld cleaning and acceptance criteria should be specified.
Supply definition
Product form changes the applicable requirements
Do not send an RFQ that names only the grade. State form, governing standard, dimensions, tolerances, finish, edge or end condition, quantity, certification and inspection.
Cold-rolled sheet and coil
Hot-rolled coil and sheet
Quarto plate
Pipe, tube and fabricated equipment by specific standard
Certificate checkpoint
Request heat identity, chemical analysis, mechanical results and compliance to the exact product specification. Add PMI, corrosion testing or supplementary examination only when the application requires it.
Interactive selection check
Test 904L against the controlling question
Procurement FAQ
Questions to close before placing the order
Is 904L stainless steel magnetic?
Magnetic response depends on microstructure and delivered condition.
Can 904L replace another grade?
Only after checking the governing standard, composition, mechanical properties, corrosion exposure, fabrication route and certification. A commercial name is not a substitution approval.
Does the table apply to pipe, tube and bar?
Not automatically. The values shown use flat-product requirements as a reference. Other forms can use different product standards, dimensions and tests.
What should a 904L RFQ include?
Product form, standard and edition, UNS or EN designation, dimensions, tolerances, finish, quantity, service, fabrication, certificate and inspection requirements.
Sources, scope and RFQ
Use traceable grade data, then specify the actual product
ASTM A240/A240M requirements for UNS N08904 flat product
Outokumpu Ultra 904L range datasheet
Atlas Grade Datasheet: 904L
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