Overview
Seamless Stainless Steel 321 Pipe is a stabilized austenitic stainless steel product, distinguished by the addition of titanium (Ti) to prevent intergranular corrosion. Composed of 18% chromium, 10% nickel, and titanium (minimum 5x carbon content), this alloy meets standards such as ASTM A312 and ASME SA-312, offering a balance of high-temperature strength, corrosion resistance, and weldability. The seamless construction ensures uniform wall thickness and superior structural integrity, critical for applications involving cyclic loading or thermal stress.
TP321 is often specified where sensitization (grain boundary carbide precipitation) is a concern, such as in welded components exposed to temperatures between 425°C and 815°C. Its ability to maintain ductility and toughness across a broad temperature range makes it a versatile choice for both high and low-temperature services.
Features
Intergranular Corrosion Resistance: Titanium stabilizes the alloy, preventing chromium carbide formation at grain boundaries, which is particularly beneficial in welded structures used in corrosive environments.
High-Temperature Performance: Retains mechanical properties up to 800°C, making it suitable for applications requiring resistance to oxidation and carburization, such as furnace components and exhaust systems.
Good Formability & Weldability: Easily formed into complex shapes and weldable without excessive post-weld heat treatment, though low-carbon filler materials are recommended to maintain corrosion resistance.
Versatile Corrosion Resistance: Resistant to mild organic acids, alkalis, and aqueous solutions, including nitric acid and stress-corrosion cracking in chloride environments better than non-stabilized 304 stainless steel.
Chemical Composition
Grade | C | Mn | Si | P | S | Cr | Ni | N | Ti |
321 | ≤0.08 | ≤2.00 | ≤1.00 | ≤0.045 | ≤0.03 | 17.00-19.00 | 9.00-12.00 |
| - |
321H | 0.04-1.00 | ≤2.00 | ≤1.00 | ≤0.045 | ≤0.03 | 17.00-19.00 | 9.00-12.00 | ≤0.10 | 4(C+N)-0.7 |
Grade Specification Comparison
Grade | UNS No | EN | Gb | JIS |
No | Name |
321 | S32100 | 1.4541 | X6CrNiTi18-10 | 0Cr18Ni11Ti | SUS 321 |
321H | S32109 | 1.4878 | X10CrNiTi18-10 | 1Cr18Ni9Ti | SUS 321H |
Mechanical Properties
Grade | Tensile Strength ksi(MPa) | Yield Strength ksi(MPa) | Elongation (% in 50mm) |
|
321,t≤0.375in(9.5mm) | ≥75(515) | ≥30(205) | ≥35 |
| 321,t>0.375(9.2mm) | 70(485) | 25(170) | ≥35 |
| 321H,t≤0.375in(9.5mm) | ≥75(515) | ≥30(205) | ≥35 |
| 321H,t>0.375(9.2mm) | 70(485) | 25(170) | ≥35 |
Application
Petrochemical Industry: Used in catalytic crackers, reformers, and heat exchangers where high-temperature resistance and protection against sensitization are essential.
Aerospace: Employed in aircraft exhaust systems and engine components exposed to elevated temperatures and oxidizing atmospheres.
Power Plants: Suitable for superheater and reheater tubes in boilers, as well as steam pipelines operating at moderate temperatures.
Food & Pharmaceutical: Ideal for processing equipment due to its non-reactive surface and ease of cleaning, meeting strict hygiene standards.
