Grade dossier
347 Stainless Steel for Stabilized Welded Components
A niobium-stabilized 18Cr-10Ni grade used for welded components and intermittent elevated-temperature exposure where resistance to sensitization is important.
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 | 0.08 max |
|---|---|
| Mn | 2.00 max |
| Si | 0.75 max |
| P | 0.045 max |
| S | 0.030 max |
| Cr | 17.00-19.00 |
| Ni | 9.00-13.00 |
| N | 0.10 max |
| Nb+Ta | 10×C min; 1.00 max |
Properties with context
Minimums, typical indicators and delivered condition
Specified annealed flat-product values
| Tensile strength | 515 MPa min |
|---|---|
| 0.2% yield strength | 205 MPa min |
| Elongation | 40% min |
| Hardness | 95 HRBW max |
Selection indicators
| Density | about 7.9 g/cm3 |
|---|---|
| Stabilization | Niobium limits chromium-carbide sensitization |
| Temperature role | Useful for intermittent heating after code review |
| Heat treatment | Not hardened by thermal treatment |
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 347 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
Expansion joints and exhaust manifolds
High-temperature gaskets and collector rings
Welded chemical equipment
Flanges and valves with stabilized-grade requirements
Reasons to stop and review
Treating 347 as a universal substitute for 304L
Using ambient properties for creep design
Ignoring chloride exposure because it is stabilized
Confusing 347 with 347H
Fabrication route
Protect properties through cutting, forming and welding
Specify S34700 and the exact product standard.
Qualify filler and heat input for the service.
Review stabilization treatment when required.
Remove heat tint and fabrication contamination.
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- and hot-rolled coil, sheet and plate
Quarto plate
Bar and long products
Tube, pipe, fittings and forgings under applicable standards
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 347 against the controlling question
Procurement FAQ
Questions to close before placing the order
Is 347 stainless steel magnetic?
Magnetic response depends on microstructure and delivered condition.
Can 347 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?
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 347 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 S34700 flat product
Outokumpu Core 347/4550 official grade guidance
ASTM A959 harmonized wrought-grade composition
Applicable product-form standard and design code