Stainless steel welded pipe, referred to as welded pipe, is a steel pipe made of commonly used steel or steel strips after being curled and formed by a unit and a mold.

Duplex stainless steel is a kind of stainless steel composed of any two phases of austenite, ferrite, and martensite in a ratio of about half. But it usually refers to austenitic-ferritic duplex stainless steel.