Grade dossier
348 Stainless Steel for Controlled Tantalum and Cobalt Service
A stabilized 18Cr-10Ni grade related to 347 but with tighter tantalum and cobalt controls for applications where residual elements matter.
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
Type 348 adds controlled tantalum and cobalt to a niobium-stabilized 18Cr-10Ni composition. The exact Nb+Ta formula and analytical limits must be taken from the purchase-order edition and product specification.
| C | 0.08 max |
|---|---|
| Mn | 2.00 max |
| Si | 1.00 max |
| P | 0.045 max |
| S | 0.030 max |
| Cr | 17.00-19.00 |
| Ni | 9.00-13.00 |
| Nb+Ta | product-standard controlled |
| Ta | 0.10 max |
| Co | 0.20 max |
Properties with context
Minimums, typical indicators and delivered condition
Specified annealed flat-product values
| Tensile strength | 515 MPa min reference |
|---|---|
| 0.2% yield strength | 205 MPa min reference |
| Elongation | 40% min reference |
| Condition | Solution-annealed wrought product |
Selection indicators
| Density | about 7.9 g/cm3 |
|---|---|
| Stabilization | Niobium-bearing |
| Special control | Low tantalum and cobalt limits |
| Availability | Verify mill capability before design freeze |
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 348 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
Nuclear and controlled-residual applications when specified
Components requiring S34800 certification
High-temperature stabilized assemblies
Projects with explicit tantalum and cobalt limits
Reasons to stop and review
Substituting 347 without purchaser approval
Assuming every mill routinely supplies 348
Using generic chemistry without the current standard
Omitting analytical and certification requirements
Fabrication route
Protect properties through cutting, forming and welding
Name S34800 and the exact standard edition.
State analytical limits and certificate requirements.
Qualify welding consumables for the project restrictions.
Confirm availability, heat treatment and testing early.
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.
Plate, sheet and strip under ASTM A240/A240M
Boiler and heat-exchanger tube under applicable standards
Bar, forgings and fittings when available
Special-order controlled-residual products
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.
IMAGE PLACEHOLDER
IMAGE PLACEHOLDER
IMAGE PLACEHOLDER
Interactive selection check
Test 348 against the controlling question
Procurement FAQ
Questions to close before placing the order
Is 348 stainless steel magnetic?
Magnetic response depends on microstructure and delivered condition.
Can 348 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 every product form?
No. 348 adds controlled tantalum and cobalt limits; acceptance depends on the exact product standard and certificate.
What should a 348 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 identity for UNS S34800 flat product
ASTM A213/A213M controlled cobalt and tantalum limits for Type 348 tube
ASTM A358/A358M material cross-reference
Project-specific nuclear or controlled-residual procurement specification