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347 Stainless Steel Pipe Fittings for High-Temperature Creep Service and Niobium Stabilization

Tags : N06625 Alloy Pipes , Stainless Steel Bars , U-bent Tubular Exchanger Tubes

High-Performance 347 Stabilized Stainless Steel Pipe Fittings for Reformer Piping, Superheater Connections, and Creep-Resistant Service

Womic Steel manufactures premium 347 Stainless Steel Pipe Fittings, including elbows, tees, reducers, caps, and stub ends. Our niobium-stabilized (columbium) austenitic stainless steel fittings provide exceptional resistance to intergranular corrosion at elevated temperatures and superior creep-rupture strength above 650°C (1200°F). They are the ideal choice for catalytic reformer piping, superheater headers, heavy-duty exhaust systems, and high-temperature chemical reactors where 321 grade has insufficient creep strength.

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Key Features of 347 Stainless Steel Pipe Fittings

Niobium Stabilization (Nb ≥ 10×C): Prevents carbide precipitation and sensitization at 425–870°C.

Superior Creep Strength: Better high-temperature creep resistance than 321, especially above 650°C.

Polythionic Acid SCC Resistance: Outstanding resistance to polythionic stress corrosion cracking in refinery service.

Full Range: Butt-weld (ASME B16.9), socket-weld (ASME B16.11), threaded (NPT) – 347H also available.

Certifications: ABS, BV, DNV, LR, NORSOK, ASME.

International Standards and Corresponding Grades

Standard	Application	347 Grade
ASME B16.9 / B16.11	Butt-weld / SW & threaded	WP347 / 347
EN 10253-2	European butt-weld	1.4550 (X6CrNiNb18-10)
JIS B2311/B2312	Japanese standard	SUS347
GB/T 12459	Chinese standard	06Cr18Ni11Nb

Chemical Composition of 347 Stainless Steel Fittings

Element	C	Mn	P	S	Si	Cr	Ni	Nb
347	≤0.08	≤2.00	≤0.045	≤0.030	≤1.00	17.0–19.0	9.0–13.0	≥10×C ≤1.10

Mechanical Properties and Heat Treatment

Property	Unit	347
Tensile Strength	MPa	≥515
Yield Strength	MPa	≥205
Elongation	%	≥35
Hardness (Brinell)	HBW	≤201
Density	g/cm³	7.93

Heat Treatment: Solution annealed at 1050–1100°C followed by water quenching.

Pressure-Temperature Ratings (ASME B16.11)

Class	100°F	500°F	750°F	1000°F (de-rated)
3000 LB	2085	1670	1390	870

Types and Production Range

Fitting Type	Main Forms	Manufacturing
Elbow	45°, 90°, 180° LR/SR	Seamless / Welded
Tee	Equal, Reducing	Seamless / Welded
Reducer	Concentric, Eccentric	Seamless / Welded
Cap	Flat, Elliptical	Seamless / Stamped
Stub End	Long/Short type	Seamless / Welded

Dimensions and Manufacturing Range

Parameter	Butt-Weld	Socket-Weld / Threaded
Size Range	1/2″ – 48″	1/8″ – 4″
Schedule	Sch5S – XXS	2000LB, 3000LB, 6000LB

Manufacturing Process

Raw 347 billets or seamless pipes.

Hot pushing or cold forging.

Solution annealing + water quenching.

Beveling or threading.

Pickling & passivation.

100% PMI (niobium verification), PT.

Surface Finishes

AP (standard)

Mechanically polished

Mirror polished (8K)

Electropolished (special order)

Quality Control and Inspection

PMI (XRF) for Nb content.

Tensile, yield, elongation, hardness.

Intergranular corrosion test per ASTM A262 Practice C (nitric acid test) or Practice E.

100% PT; optional UT for heavy-wall.

Radiographic testing for welded large fittings.

Applications

Petrochemical Refining: Catalytic reformer piping, hydrotreater heat exchanger connections.

Power Generation: Superheater headers, boiler connections above 650°C.

Chemical Processing: High-temperature organic acid and vinegar plants.

Aerospace: Exhaust ductwork and afterburner fuel lines.

Packaging, Shipping, and Logistics

Same as previous: cartons ≤2″, wooden crates for larger.

Thread protectors for NPT ends.

Ready stock: 1/2″–12″ Sch10S, Sch40S.

Full documentation including oxidation test reports.

FAQ

1. What is the difference between 347 and 321?
347 uses niobium (columbium) instead of titanium, providing higher creep strength at temperatures above 650°C and better resistance to polythionic acid SCC.

2. Do 347 fittings require post-weld heat treatment?
No, niobium stabilization eliminates the need for PWHT.

3. Are 347H fittings available?
Yes, 347H (higher carbon 0.04-0.10%) for even higher creep strength.

Why Choose Womic Steel for 347 Fittings?

True niobium-stabilized material, heat number traceable.

Experienced in high-temperature petrochemical projects.

Large stock range: 1/2″–24″ seamless butt-weld fittings.

Contact

Tel / WhatsApp:

Victor: +86 15575100681

Jack: +86 18390957568

E-mail: info@womicstainless.com

Website: www.womicsteel.com

Contact Womic Steel today for a competitive quote on 316/316L stainless steel pipe fittings. We offer certified quality, fast production lead times, and reliable global delivery to keep your pipeline projects running smoothly.

Appendix: Common Sizes & Related Keywords

Stock Examples:

347 Stainless Steel 90° LR Elbow 4″ Sch40S, 347 Equal Tee 6″×6″ Sch10S, 347 Concentric Reducer 8″×4″ Sch80S, 347 Lap Joint Stub End 3″ Sch10S.

Related Keywords:

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