This standard specifies the types and codes, key dimensions, surface contours, end bevels, tolerances, materials, manufacturing and heat treatment, quality requirements, inspection rules, marking, packaging, storage, Quality certificate. This standard specifies the types and codes, dimensions and tolerances, materials, and manufacturing of factory-made duplex stainless steel butt welded pipe fittings (elbows, tees and crosses, reducers, and caps) from DN50 to DN1200 (NPS2 to NPS48). , inspection and testing, marking, protection and packaging requirements. This standard applies to non-welded pipe fittings (seamless pipe fittings) made of duplex stainless steel seamless pipes and straight seam welded steel pipes and welded pipe fittings made of duplex stainless steel plates.