Duplex stainless steels are normally not used at elevated temperatures but when this grade is pushed at an increased temperature, it does not lose much yield strength. At a temperature of about 250°C, the yield strength of the grade remains about 400 MPa and UTS remains about 650 MPa. A high-pitting resistance is guaranteed by the grade in delivered condition. Pitting resistance number (PREN) of the grade is normally greater than 40, which is better than other austenitic and duplex grades. It also provides superior resistance to overall localized corrosion.
Tungsten is normally an impurity, but the addition of tungsten in the grade certainly enhances the pitting resistance and has its value in the PREN formula. A small addition of copper in 32760 makes sure that resistance to variable non-oxidizing and mineral acids is provided. The 25% chromium in the grade along with other alloying elements, gives the grade superior corrosion, oxidation resistance, better strength and better stress corrosion resistance to other 300 series alloys and many 22% Cr alloys. The grade has fine forming characteristics and can be appropriately forged around 1100-1250°C. Reheat might be required for complete forging, followed by cooling in air. The grade has significant impact strength and is used in many applications for the same purposes. Very less decrease in impact strength is obtained with a decrease in temperature.
The lost impact strength is retained post-welding. No ductile to brittle transition is obtained at lower temperatures, hence excellent ductility is one of its prime properties. Even at sub-zero temperatures, down to -50°C, ductility and mechanical properties are preserved.
