Manufacturers & Suppliers of ASTM A182 Duplex Steel S31803 SWRF Socket Weld Flange, 1/2\" ASME B16.5 Class 400# Socket Weld Flanges, ASME SA182 S31803 Duplex SWRF Socket Weld Flanges, ANSI B16.5 SWRF, DIN 1.4462 Socket Weld Flange, UNS S31803 SWRF Flange.