Type 321 Stainless Steel

Type 321 is a standard austenitic 18/8 chromium nickel alloy with the addition of Titanium making it an excellent choice in elevated temperature environments.

The titanium stabilises the material removing its susceptibility to the effects of intergranular corrosion. 321 is therefore the stainless steel material of choice for applications in working environments up to 900° C.

A drawback of Type 321 is that the titanium does not transfer well across a high temperature arc, so it is not recommended as a welding consumable.

In such instances, 347 is the preferred choice as the Niobium performs the same function as Titanium but can be still transferred across a high temperature arc. Type 347 is therefore the consumable of choice for welding Grade 321.

The steel has excellent forming and welding qualities and excellent toughness even at cryogenic temperatures. If you are looking for a stainless steel to provide resistance to intergranular corrosion, 304L is the normal choice as it is a more commonly used and supplied steel.

However, 321 is a much better option in operating temperature environments in excess of 500° C and therefore has its own merits.

Note that Type 321 does not polish well so it is not practical to use this material as cosmetic architectural feature.

Mechanical Properties of Type 321

Description Type 321
Proof Stress 0.2% (MPa) 205
Tensile strength (MPa) 515
Elongation A5 (%) 40
Hardness HB: 217
HRB: 95

Chemical Composition of Type 321

UNS No S32100
EN 1.4541
AISI 321
Carbon (C) 0.08
Silicon (Si) 0.75
Manganese (Mn) 2.00
Phosphorus (P) 0.045
Sulphur (S) 0.030
Chromium (Cr) 17.00 – 19.00
Molybdenum (Mo)
Nickel (Ni) 9.00 – 12.00
Nitrogen (N)
Other Ti:5x(C+N)/0.70