Performance characteristics of duplex stainless steel

Due to the characteristics of the two-phase structure, through the correct control of the chemical composition and heat treatment process, the duplex stainless steel has the advantages of ferritic stainless steel and austenitic stainless steel, which combines the excellent toughness and weldability of austenitic stainless steel with the high strength and resistance of ferritic stainless steel
Combined with chloride stress corrosion properties, it is these superior properties that make duplex stainless steel develop rapidly as a weldable structural material, and since the 1980s has become a steel class alongside martensitic, Austenitic and ferritic stainless steel. Duplex stainless steel has the following performance characteristics:
(1) Molybdenum containing duplex stainless steel has good resistance to chloride stress corrosion under low stress. Generally, 18-8 austenitic stainless steel is prone to stress corrosion fracture in neutral chloride solution above 60°C, and heat exchangers, evaporators and other equipment made of this kind of stainless steel in trace chloride and hydrogen sulfide industrial media have a tendency to produce stress corrosion fracture, while duplex stainless steel has good resistance.
(2) Molybdenum containing duplex stainless steel has good pitting resistance. With the same pitting resistance value (PRE=Cr%+3.3Mo%+16N%), the critical pitting potential of duplex stainless steel is similar to that of austenitic stainless steel. The pitting resistance of duplex stainless steel and austenitic stainless steel is equivalent to AISI 316L. The resistance to pitting and crevice corrosion of 25%Cr, especially high chromium duplex stainless steels containing nitrogen, exceeds that of AISI 316L.
(3) It has good corrosion resistance to fatigue and wear corrosion. Under the conditions of some corrosive media, it is suitable for making power equipment such as pumps and valves.
(4) Good comprehensive mechanical properties. It has high strength and fatigue strength, and the yield strength is twice that of 18-8 type austenitic stainless steel. The elongation of the solid solution state reaches 25%, and the toughness value AK (V-notch) is more than 100J.
(5) Good weldability, small hot crack tendency, generally do not need to preheat before welding, no heat treatment after welding, can be welded with 18-8 type austenitic stainless steel or carbon steel and other dissimilar.
(6) Dual-phase stainless steel with low chromium (18%Cr) hot working temperature range is wider than 18-8 austenitic stainless steel, resistance is small, without forging, direct rolling production of steel plates. Duplex stainless steel with high chromium (25%Cr) is slightly more difficult to process than austenitic stainless steel, and can produce products such as plates, tubes and wires.