Grade dossier
347H Stainless Steel for Creep-Resistant Hot Service
The controlled higher-carbon 347 variant developed for creep-rated elevated-temperature service, while maintaining niobium stabilization.
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 | 0.04-0.10 |
|---|---|
| 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 | 8×C min; 1.10 max |
Properties with context
Minimums, typical indicators and delivered condition
Specified annealed flat-product values
| Room-temperature tensile strength | 515 MPa min |
|---|---|
| Room-temperature 0.2% yield | 205 MPa min |
| Elongation | 40% min |
| Hardness | 95 HRBW max |
Selection indicators
| Density | about 7.9 g/cm3 |
|---|---|
| Producer air-temperature guidance | about 850°C / 1560°F; guidance only |
| Creep role | Controlled carbon supports elevated-temperature strength |
| Design basis | Code allowables, creep, time and temperature |
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 347H 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
Refinery fired-heater and boiler components
Pressure and reactor vessels under an approved code
Welded tubes and high-temperature fittings
Thermal-storage and furnace components
Reasons to stop and review
Substituting 347 without carbon review
Using oxidation guidance as a design allowable
Ignoring wet shutdown conditions
Claiming an EN grade is automatically identical
Fabrication route
Protect properties through cutting, forming and welding
State S34709 and the governing code.
Qualify filler, heat input, stabilization and NDE.
Use creep and allowable-stress data at temperature.
Review grain size and supplementary requirements.
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 to ASTM A240/A240M
High-temperature pipe and tube
Forgings, fittings and valves
Code-approved pressure components
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.
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Interactive selection check
Test 347H against the controlling question
Procurement FAQ
Questions to close before placing the order
Is 347H stainless steel magnetic?
Magnetic response depends on microstructure and delivered condition.
Can 347H 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 347H 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 S34709 flat product
Outokumpu Therma 347H official datasheet
ASTM A213/A213M high-temperature tube chemistry framework
Applicable ASME allowable-stress tables