The first type is a low alloy type, representing the grade UNS S32304 (23Cr-4Ni-0.1N). The steel does not contain molybdenum, and the PREN value is 24-25. It can be used instead of AISI304 or 316 in terms of stress corrosion resistance.
The second type is a medium alloy type, the representative grade is UNS S31803 (22Cr-5Ni-3Mo-0.15N), the PREN value is 32-33, and its corrosion resistance is between AISI 316L and 6% Mo + N austenitic stainless steel. between.
The third type is a high alloy type, generally containing 25% Cr, also containing molybdenum and nitrogen, and some also contains copper and tungsten. The standard grade is UNSS32550 (25Cr-6Ni-3Mo-2Cu-0.2N), and the PREN value is 38-39 The corrosion resistance of this type of steel is higher than that of 22% Cr duplex stainless steel.
The fourth type is a super duplex stainless steel type, which contains high molybdenum and nitrogen. The standard grade is UNS S32750 (25Cr-7Ni-3.7Mo-0.3N), and some also contain tungsten and copper. The PREN value is greater than 40, which can be used for harsh Medium conditions, with good comprehensive corrosion resistance and mechanical properties, comparable to super austenitic stainless steel.