ASTM A240 347 Stainless Steel Plate UNS S34700 with Niobium Stabilization and

ASTM A240 347 Stainless Steel Plate UNS S34700 with Niobium Stabilization and Creep Resistance

Shaanxi Shangyou Stainless Steel Co., Ltd. supplies ASTM A240 347 stainless steel plate for global distributors, fabricators, equipment manufacturers, and EPC contractors requiring high temperature stability with weld integrity. Produced to ASTM A240/A240M as UNS S34700 (also equivalent to EN 1.4550 and SUS 347), this niobium-stabilized austenitic stainless steel is specifically engineered to resist intergranular corrosion in elevated temperature service where unstabilized grades like 304 would sensitize.

The defining characteristic of 347 stainless steel is its niobium (columbium) addition—typically at least ten times the carbon content—which stabilizes the alloy against chromium carbide precipitation. When standard 304 is exposed to temperatures in the 800-1500°F (427-816°C) range (common during welding or high temperature service), carbon combines with chromium to form chromium carbides at grain boundaries, depleting local chromium and causing intergranular corrosion. In 347, niobium preferentially bonds with carbon, forming stable niobium carbides and preserving the material's corrosion resistance in the as-welded condition. The alloy also provides excellent oxidation resistance, even surpassing 321 in strong oxidizing conditions.

Custom Attributes

Core Specifications

Applications and Material Selection Guide

ASTM A240 347 stainless steel plate is specified for applications involving sustained elevated temperatures where niobium stabilization provides superior creep resistance.

Typical applications include:

• Heat exchangers and furnace components
• Aircraft exhaust systems and jet engine parts
• Chemical processing equipment and reactor tubes
• Nuclear power plant components
• Oil refinery equipment (polythionic acid service)
• Boiler casings and welded pressure vessels

Key selection considerations: Niobium has higher affinity for carbon than titanium, forming more stable NbC that remains intact up to 900°C, providing better creep resistance than 321 for long-term high-temperature service. For applications exceeding 900°C, 310S is recommended.

Processing, Packaging and After-Sales

Shangyou Stainless Steel provides value-added processing including cut-to-length, slitting, polishing, laser cutting, bending and forming, and protective film application.

All plates are packed with export-standard protection including protective paper between sheets, edge protection, steel strapping, waterproof wrapping, and wooden pallets or steel frames.

Quality documents include MTC 3.1, inspection reports, packing list, and heat number traceability. Third-party inspection (SGS, TUV, BV) can be arranged upon request.

Frequently Asked Questions

1. What is the difference between 347 and 321 stainless steel?

Both are stabilized grades, but 347 uses niobium while 321 uses titanium. 347 offers superior resistance to intergranular corrosion in strongly oxidizing environments and better creep strength at high temperatures. Niobium carbides (NbC) remain stable up to 900°C, while titanium carbides (TiC) may dissolve above 870°C.

2. What is the sensitization range and why does 347 resist it?

The sensitization range is 800-1500°F (427-816°C), where carbon combines with chromium at grain boundaries in unstabilized alloys. Niobium in 347 preferentially forms carbides with carbon, preventing chromium depletion and maintaining corrosion resistance.

3. What is the maximum service temperature for 347?

347 offers good oxidation resistance up to 1500°F (816°C) in continuous service, with short-term capability to 950°C. For service above 900°C, 310S is recommended.

4. Is 347 stainless steel magnetic?

347 is austenitic and non-magnetic in the annealed condition. Cold working may induce slight magnetism.

5. What thickness ranges are available for 347 plate?

Cold rolled 0.3-3.0mm; hot rolled 3.0-50.0mm. Heavier thicknesses available on request.

6. Can 347 be welded?

Yes. 347 offers excellent weldability. ER347 filler metal is recommended to match niobium content. No pre-heat or post-weld heat treatment is needed for most applications, and weld zone corrosion resistance is equivalent to the base metal.

7. What are the mechanical properties of 347?

Tensile strength ≥515 MPa (75 ksi), yield strength ≥205 MPa (30 ksi), elongation ≥40%, hardness ≤92 HRB or ≤201 HBW.

8. What documents are provided with delivery?

MTC 3.1, inspection reports, packing list, and heat number traceability.

9. Is third-party inspection available?

Yes, SGS, TUV, or BV upon request.

10. What are typical applications for 347?

Heat exchangers, aircraft exhaust systems, chemical processing equipment, nuclear reactor components, oil refinery equipment, boiler casings, and welded pressure vessels.

Request a Quote

Need ASTM A240 347 stainless steel plate for high temperature heat exchanger, aerospace, or chemical processing applications? Send requirements including grade, thickness/width/length, surface finish, quantity, and application.

Shangyou Stainless Steel provides custom sizes, processing, and export solutions for global B2B customers.