Manufacturer of Duplex Steel S31803 Fasteners in India. ASTM A479 UNS S31803 bolts are commonly used for flanges in industries. Duplex UNS S31803 nuts also have excellent forming and welding properties. Steel 1.4462 duplex fasteners with 150LB and 300LB ratings are kept in slip-on, blind, threaded, and weld neck forms.