Due to the characteristics of the two-phase structure, through the correct control of chemical composition and heat treatment process, the duplex stainless steel has the advantages of both ferritic stainless steel and austenitic stainless steel. It combines the excellent toughness and weldability of austenitic stainless steel with iron. The high strength and resistance of solid stainless steel
The chloride stress corrosion properties are combined together. It is these superior properties that make duplex stainless steel develop rapidly as a weldable structural material. Since the 1980s, it has become one of the martensitic, austenitic and ferritic stainless steels. 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 type austenitic stainless steel is prone to stress corrosion cracking in neutral chloride solution above 60°C. Heat exchangers, evaporators and other equipment made of this type of stainless steel are used in trace chloride and hydrogen sulfide industrial media. There is a tendency to produce stress corrosion cracking, while duplex stainless steel has good resistance.
(2) Molybdenum-containing duplex stainless steel has good pitting corrosion resistance. At the same pitting resistance equivalent value (PRE=Cr%+3.3Mo%+16N%), the critical pitting corrosion potential of duplex stainless steel and austenitic stainless steel is similar. The pitting corrosion resistance of duplex stainless steel and austenitic stainless steel is comparable to AISI 316L. The pitting and crevice corrosion resistance of high-chromium duplex stainless steel containing 25% Cr, especially nitrogen, exceeds AISI 316L.
(3) It has good corrosion fatigue resistance and wear corrosion resistance. Under certain corrosive medium conditions, it is suitable for making power equipment such as pumps and valves.
