A New Series of Mo-free 21.5Cr-3.5Ni-xW-0.2N Economical Duplex Stainless Steels

A new series of economical Mo-free duplex stainless steels 21.5Cr-3.5Ni-xW-0.2N (x = 1.8-3.0, mass%) have been developed. The effects of W on mechanical properties and corrosion resistance were investigated, and the microstructures were analyzed by optical microscopy, X-ray diffraction, transmission...

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Published inJournal of iron and steel research, international Vol. 21; no. 1; pp. 69 - 75
Main Authors ZHANG, Zi-xing, RAN, Qing-xuan, XU, Yu-lai, YU, Xiao-jiang, JIANG, Da-wei, XIAO, Xue-shan
Format Journal Article
LanguageEnglish
Published 01.01.2014
Subjects
Austenite
Corrosion resistance
Duplex stainless steels
Ferrite
Iron and steel industry
Molybdenum
Pitting (corrosion)
Solution heat treatment
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Summary:A new series of economical Mo-free duplex stainless steels 21.5Cr-3.5Ni-xW-0.2N (x = 1.8-3.0, mass%) have been developed. The effects of W on mechanical properties and corrosion resistance were investigated, and the microstructures were analyzed by optical microscopy, X-ray diffraction, transmission electron microscopy and electron backscatter diffraction. The designed steels have a balanced ferrite-austenite relation and are free of sigma phase after solution treatment at 750-1300 [degrees]C for 30 min followed by water-quenching, whereas a small number of Cr sub(23)C sub(6) precipitates were found after solution treatment at 750 [degrees]C. After solution treatment at 1050 [degrees]C, the steel with 1.8% (mass percent) W exhibits the highest room temperature tensile strength due to the strongest work hardening effect, while the steel with 3.0% (mass percent) W exhibits the highest fracture elongation owing to the transformation-induced plasticity (TRIP) effect. The ductile-brittle transition (DBT) and martensite transformation are respectively found in the ferrite and austenite, which deteriorates the impact properties of the steels with the increase of W content. The corrosion resistance of the designed steels is improved with the increase of W content. The pitting resistance of austenite is obviously better than that of ferrite for the designed alloys. Among the designed steels, the steel with 1.8% (mass percent) W is found to be an optimum steel with excellent comprehensive properties and lowest production cost.
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ISSN:1006-706X