Stainless steel 321 is a heat-resistant variation of stainless steel, primarily known for its excellent resistance to high temperatures. It belongs to the austenitic class of stainless steels, which are non-magnetic and characterized by their high ductility and corrosion resistance.

The composition of stainless steel 321 includes around 17-19% chromium, 9-12% nickel, and 0.08% carbon, with the addition of titanium. The titanium addition helps to stabilize the material and prevent sensitization during welding, which can lead to intergranular corrosion. This makes stainless steel 321 suitable for applications involving elevated temperatures and welding operations.

Stainless steel 321 offers excellent resistance to oxidation and scaling at temperatures up to 900-1500°C (1652-2732°F), making it ideal for use in high-temperature environments such as aircraft exhaust systems, furnace components, and automotive applications. It also exhibits good corrosion resistance in moderately corrosive environments.

The mechanical properties of stainless steel 321 are similar to those of other austenitic stainless steels, including good formability, weldability, and high toughness. It is widely used in industries such as aerospace, automotive, chemical processing, and power generation.

It's important to note that while stainless steel 321 provides exceptional high-temperature performance, it may not be as corrosion-resistant as other stainless steel grades, such as 304 or 316, in certain aggressive environments.