UNS S32750 is a high-alloy super duplex stainless steel for service under extremely corrosive conditions. It is developed mainly for chloride containing environments like seawater and, therefore, it contains high amounts of chromium, molybdenum and nitrogen.
USN S31803 is a medium-alloy duplex stailess steel with high corrosion resistance. This steel is the most widely used of the three. Continual development work for many yeares has lead to increased nitrogen and molybdenum contests, thus further improving the weldability and corrsion resistance.
USN S32304 s al low-alloy duplex stainless steel. It contains no molybdenum and has lower nikel cotent then the other two. It is the developed as a high strength and low-cost alternative to the standard austenitic grades 304L and 316L.