Pipes and Tubes

Pipes and Tubes

Stainless steel 321 tube and pipe are made with austenitic stainless steel which is very similar to type 304 stainless steel, except for a higher level of titanium and carbon contents. SS 321 comes with characteristics that are suitable for metal fabricators as it has an outstanding corrosion and oxidation resistance, along with excellent toughness, even down to cryogenic levels of temperatures.

321 stainless steel physical properties

Grade Density (g/cm3) Elastic Modulus (GPa) Mean Co-eff of Thermal Expansion (μm/m/°C) Thermal Conductivity (W/m.K) Specific Heat
0-100°C
Electrical Resistivity (nΩ.m)
0-100°C 0-315°C 0-538°C at 100°C (J/Kg.K)
SS 321 8 190-210 16.6 17.2 18.6 16.1 500 720

Alloy 321H (UNS S 32109) pipes and tubes are made with stainless steel which is the higher carbon version of the alloy 321; it was developed for enhanced resistance to creep and for better strength at temperatures above 1000°F (537°C).

Production Process

Grade SS 310 or UNS S31009 is developed with processes such as ERW (Electric Resistance Welded), Seamless and EFW (Electric Fusion Welding) pipes and tubes have different forms such as round, square, rectangle, etc. have a specific end as plain, bevel, and threaded with normal thickness of different schedule which ranges from SCH 5 to SCH XXS.

General Specification
GRADE UNS OLD BRITISH EURONORM SWEDISH SS JAPANESE JJ
BS EN NO NAME
SS 321 S32100 321S21 58B, 58C 1.4541 X6CrNiTi 8-10 2337 SUS 321
SS 321H S32109 321S51 1.4878 X10CrNiTi 8-10 SUS 321H

The common processes used to manufacture these pipes and tubes are cold pilgering process, extrusion process, tube mill Process, and piercing process which need heat treatment and mechanical testing.

Fabrication and Heat Treatment

Stainless steel UNS S32100 pipes and tubes have good heat resistance, titanium stabilized, austenitic alloy which is commonly used for working in the 1000°F – 1600°F temperature range. 

Thermal treatment processes cannot be used to harden these stainless steel pipes and tubes.

In annealed conditions, stainless steel 321 tube and pipes remain non-magnetic, but with heavy cold working, they might become mildly magnetic. In annealing temperatures of 1750°F and 1850°F, stainless steel 321 pipe and tubes can achieve maximum stabilization. 

Properties

Typical recommended working temperatures for forging, upsetting and other processes are 2100°F–2300°F (1149°C–1260°C) for SS 321 pipes and tubes. Austenitic stainless steel grade 321 tubes are readily welded by all popular methods including the submerged arc process.

Mechanical Properties

Grade Tensile Strength Yield Strength Elongation Hardness, MAX
[MPA] [MPA] (% in 50mm) min HRB HRC
SS 321/H 515 205 40 95 217

321 stainless steel tubes are very similar to type SS 304 but with the addition of titanium of 5 times the carbon content, it reduces or prevents carbide precipitation in welding and in the 800°F – 1500°F service conditions. 

Here’s a detailed 321 Stainless steel chemical composition for your understanding.

GRADE Cr Ni C Mn P Si Ti Fe S N
SS 321 MIN % 17 9 5x(C+N)
MAX % 19 12 0.08 2 0.045 0.75 0.7 BALANCE 0.03 0.1

Applications

SS 321 Pipes and tubes are widely used in conditions where the soaring temperature is possible. These 321 tubes and pipes are commonly found used in high-temperature chemical process equipment, aircraft piston engine manifolds, exhaust stacks, thermal oxidizers, expansion joints, refinery equipment, and more.

Specifications

Stainless steel 321/H Seamless Pipe : ASTM/ASME SA 312/ A 312

Stainless steel 321/H Seamless tube : ASTM/ASME SA 213/A 213

Stainless steel 321/H ERW Pipe          : ASTM/ASME SA 312/ A 312

Stainless steel 321/H ERW Tube         : ASTM/ASME SA 249/ A 249