ASTM A790 / ASME SA790 S31803 Duplex Stainless Steel Pipe

ASTM A790 / ASME SA790 S31803 Duplex Stainless Steel Pipe

ASTM A790/ASME SA790 standard is developed and published by the American Society for Testing and Materials, which comprehensively specifies the chemical composition, mechanical properties, dimensional tolerances, testing methods, inspection requirements, etc. of seamless and welded duplex stainless steel pipes. S31803 is a specific grade under the ASTM A790/ASME SA790 standard, representing a specific chemical composition range of duplex stainless steel. It is one of the most widely used duplex stainless steel grades.

Why is S31803 one of the most widely used duplex stainless steel grades?

• Excellent strength: The yield strength of S31803 duplex stainless steel (≥ 450 MPa/65 ksi) is more than twice that of standard austenitic stainless steel materials such as 304/316, and its tensile strength is also very high (≥ 620 MPa/90 ksi). This is why S31803 duplex stainless steel pipes can use thinner pipe walls under the same pressure requirements, thereby reducing the weight of the pipe itself, balancing material and production costs, and bringing higher economic benefits.
• Excellent corrosion resistance: Thanks to its high chromium, molybdenum, and nitrogen content, S31803 duplex stainless steel has excellent resistance to pitting and crevice corrosion, and performs much better than 316L in chloride containing environments such as seawater, chemical media, and bleaching agents. S31803's duplex structure provides excellent resistance to chloride stress corrosion cracking for pipes, which is superior to austenitic stainless steels such as 304 and 316, especially in the medium temperature range of about 60 ° C-150 ° C; S31803 duplex stainless steel has strong resistance to uniform corrosion and has good corrosion resistance in various acidic and alkaline media such as sulfuric acid, phosphoric acid, and organic acids.
• Good toughness: Although the toughness of S31803 duplex stainless steel is not as good as austenitic stainless steel, it is much higher than ferritic stainless steel and martensitic stainless steel. It can usually maintain sufficient toughness in low temperature environments as low as about -50 ℃.

• Good weldability: Dual phase steel usually has good weldability, but specific welding procedures and welding material selection need to be followed. Higher alloy welding materials are usually selected, and heat input and interlayer temperature are strictly controlled to maintain ideal phase balance between the weld and heat affected zone.

• Lower coefficient of thermal expansion: S31803 duplex stainless steel has a lower coefficient of thermal expansion, closer to carbon steel than austenitic stainless steel, which is beneficial for connecting with carbon steel components and effectively reduces thermal stress.

ASTM A790/ASME SA790 Duplex Stainless Steel Pipe Chemical Composition

ASTM A790/ASME SA790 Duplex Stainless Steel Pipe Application:

• Oil and natural gas: submarine pipelines, umbilical cables; Oil and gas production pipelines (especially in acidic environments containing H ₂ S/CO ₂); Gathering and transportation pipelines; Process pipeline; Heat exchanger bundle.
• Chemical and petrochemical industries: process pipelines (transporting corrosive media such as acids, alkalis, salts, solvents, etc.); Reactor pipeline; Heat exchanger tubes (tube side and shell side); Evaporator and condenser pipelines; Catalyst delivery pipe.
• Pulp and paper: bleaching workshop pipelines (such as ClO ₂, NaOH); Steaming liquid pipeline; Black liquor pipeline.

• Energy: flue gas desulfurization system pipelines; Geothermal fluid transport pipeline

• Environmental engineering: sewage treatment plant pipelines (especially chlorine containing disinfectants); Garbage leachate treatment pipeline

• Food and pharmaceuticals: require special process pipelines with high strength and corrosion resistance (ensuring compliance with hygiene standards)