ASTM A790 UNS 31803

ASTM A790 UNS S31803

ASTM A790 UNS S31803 Stainless Steel Mechanical Polish Pipes are high-performance duplex stainless steel pipes manufactured with precision mechanical polishing to achieve a smooth, uniform, and aesthetically enhanced surface finish. Produced in accordance with ASTM A790 / ASME SA790 standards, these pipes are engineered for applications requiring high strength, superior corrosion resistance, and an attractive polished appearance.

UNS S31803 is a duplex stainless steel grade that offers a balanced microstructure of austenite and ferrite, providing improved mechanical strength and excellent resistance to pitting, crevice corrosion, and stress corrosion cracking. The addition of chromium, molybdenum, and nitrogen enhances performance in chloride-rich and aggressive environments. The mechanical polishing process further improves surface smoothness, making these pipes suitable for marine, chemical, oil & gas, and structural applications.

Specifications

Standard	ASTM A790 / ASME SA790
Grade	UNS S31803
Material Type	Duplex Stainless Steel
Manufacturing Process	Welded / ERW
Size Range	1/2" NB to 24" NB
Wall Thickness	Schedule 5S to Schedule 80S
Length	6 Meters Standard / Custom Cut Length
Surface Finish	Mechanical Polish (180 Grit, 240 Grit, 320 Grit, 400 Grit)
End Type	Plain End, Beveled End, Threaded

Key Features & Benefits

• High Mechanical Strength: Approximately twice the yield strength of austenitic stainless steels.
• Excellent Corrosion Resistance: Strong resistance to pitting, crevice corrosion, and stress corrosion cracking.
• Chloride & Marine Resistance: Suitable for offshore and coastal environments.
• Enhanced Surface Finish: Smooth mechanical polish ideal for hygienic and decorative applications.
• Cost-Effective Performance: Higher strength allows optimized wall thickness in some applications.
• Good Fabrication & Weldability: Suitable for demanding industrial fabrication projects.

Chemical Composition (Typical)

Element	Composition (%)
Carbon (C)	0.03 Max
Chromium (Cr)	21.0 – 23.0
Nickel (Ni)	4.5 – 6.5
Molybdenum (Mo)	2.5 – 3.5
Nitrogen (N)	0.08 – 0.20
Manganese (Mn)	2.00 Max
Silicon (Si)	1.00 Max

Applications

• Oil & Gas Processing Plants
• Offshore & Marine Installations
• Chemical Processing Industries
• Desalination & Water Treatment Plants
• Heat Exchangers & Pressure Vessels
• Structural & Architectural Applications

Testing & Inspection

• Hydrostatic Testing
• Ultrasonic Testing (UT)
• Eddy Current Testing
• Positive Material Identification (PMI)
• Dimensional & Visual Inspection

Conclusion

ASTM A790 UNS S31803 Stainless Steel Mechanical Polish Pipes offer an excellent balance of strength, corrosion resistance, and refined surface finish. Their duplex microstructure ensures dependable performance in aggressive, high-pressure, and marine environments, making them a reliable choice for industrial and offshore applications.