Duplex Steel Tube, Duplex Stainless Steel Seamless Tube, ASTM A790 Duplex Seamless Tubing Max Stainless Steel offers range of Duplex Steel Pipe and Tubes. It is called as Duplex because of its grouping of microstructure with equivalent amount of ferrite and austenite. Duplex stainless steel grades are superior to standard austenitics with regard to stress corrosion cracking resistance, and duplex grades are also good in a number of acidic and alkaline environments.