DUPLEX STAINLESS STEELS
Duplex stainless steels are the two-phase group of stainless steels whose structure contains roughly equal proportions of austenite and ferrite. This mixed structure combines the corrosion resistance of the austenitic grades with the strength of the ferritic grades.
Their yield strength is markedly above that of the austenitic stainless steels, which makes it possible to carry the same load in a thinner section and so to build lighter and more economical structures. Their resistance to stress corrosion cracking in chloride-bearing environments is high, and their low nickel content is an advantage against price fluctuation.
In return, their use at high temperature is limited: long exposure to high temperature leads to embrittlement of the ferrite phase. Heat input and phase balance must be controlled during welding. Chemical and petrochemical plants, pressure vessels, seawater lines and the paper industry are the main applications.
Choosing a grade. The most common grade in the duplex family is AISI 318 (1.4462), the standard choice in chemical, petrochemical and marine applications. AISI 329 (1.4460), with its higher chromium content, is used in particular for heat exchanger tubes and in abrasive environments. For seawater and offshore applications with a heavier chloride load, the super duplex grades should be considered.
OUR DUPLEX STAINLESS STEEL GRADES
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