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321 Stainless Steel Pipe Fittings for High-Temperature Service and Creep Resistance

Tags : Bimetallic Wear Resistant Pipes , 310S heat exchanger tube , Duplex Stainless Tubes

High-Performance 321 Stabilized Stainless Steel Pipe Fittings for Superheaters, Reformer Piping, and High-Temperature Process Lines

Womic Steel manufactures premium 321 Stainless Steel Pipe Fittings, covering a full range of products including elbows, tees, reducers, caps, and stub ends. Our titanium-stabilized austenitic stainless steel fittings provide excellent resistance to intergranular corrosion at elevated temperatures, superior creep strength, and outstanding oxidation resistance. They are the ideal choice for superheater connections, reformer piping, exhaust systems, high-temperature chemical reactors, and boiler components.

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Key Features of 321 Stainless Steel Pipe Fittings

Intergranular Corrosion Resistance: Titanium stabilization (Ti ≥ 5×C) prevents chromium carbide precipitation during welding or high-temperature service (up to 800°C).

High-Temperature Strength: Maintains mechanical properties up to 800°C (1472°F) with good creep resistance.

Full Range of Types: Elbows (45°/90°/180°), tees, reducers, caps, stub ends, crosses, nipples – butt-weld, socket-weld, threaded.

Weldability: Excellent weldability without need for post-weld heat treatment.

International Certifications: ABS, BV, DNV, LR, GL, RINA, CCS, KR, NK, and NORSOK compliant.

International Standards and Corresponding Grades

Standard	Application	321 Grade
ASME B16.9 / B16.11	Butt-weld / SW & threaded	WP321 / 321
EN 10253-2	European butt-weld	1.4541 (X6CrNiTi18-10)
JIS B2311/B2312	Japanese standard	SUS321
GB/T 12459	Chinese standard	06Cr18Ni11Ti

Chemical Composition of 321 Stainless Steel Fittings

Element	C	Mn	P	S	Si	Cr	Ni	Ti
321	≤0.08	≤2.00	≤0.045	≤0.030	≤1.00	17.0–19.0	9.0–12.0	≥5×C

Mechanical Properties and Heat Treatment

Property	Unit	321
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 (per ASME B16.11)

Class	100°F (psig)	500°F (psig)	750°F (psig)
2000 LB	1390	1115	930
3000 LB	2085	1670	1390
6000 LB	4170	3340	2785

Types and Production Range

Fitting Type	Main Forms	Manufacturing Method
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
Nipple	Threaded	Machined

Dimensions and Manufacturing Range

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

Manufacturing Process (Seamless)

Raw 321 billets from certified mills.

Heating, piercing, hot rolling.

Cold drawing / pilgering.

Solution annealing at 1050–1100°C + water quench.

Pickling, passivation, end finishing.

100% PMI, PT, dimensional check.

Surface Finishes

Annealed & Pickled (standard)

Mechanically Polished

Mirror Polished (8K)

Electropolished (upon request)

Quality Control and Inspection

PMI 100% for titanium verification.

Tensile, yield, elongation, hardness.

100% Penetrant Testing.

Intergranular corrosion test (ASTM A262 Practice E).

Hydrostatic test upon request.

Applications

Petrochemical: Reformer piping, superheater headers.

Power Generation: Boiler connections, HRSG.

Heat Exchangers: High-temperature service.

Aerospace: Exhaust ducting.

Packaging and Shipping

Same as 304/304L: cartons for small sizes, wooden crates for large sizes.

Plastic caps / thread protectors.

Ready stock for common sizes (1/2″–12″ Sch10S/Sch40S).

FAQ

1. Why choose 321 instead of 304L for high temperature?
321 contains titanium to prevent sensitization at elevated temperatures (450–850°C), making it suitable for welding without PWHT.

2. Can 321 fittings be used in sour service?
Limited – for severe sour service, consider duplex or Alloy 825.