ASTM A790 UNS S32205 Duplex Seamless Pipe for Oil and Gas

What Is ASTM A790 UNS S32205

ASTM A790 UNS S32205 is a duplex stainless steel seamless pipe that combines ferritic and austenitic microstructures, offering excellent corrosion resistance, particularly against chloride stress corrosion cracking, while maintaining high strength. Known commercially as duplex 2205, it is highly suitable for marine environments, chemical processing, and pulp and paper industries, with a service temperature limit below 300 degrees C because of embrittlement risk.

Chemical Composition

Limits per ASTM A790 are carbon 0.030 percent maximum, manganese 2.0 percent, phosphorus 0.030 percent, sulfur 0.020 percent, silicon 1.0 percent, chromium 22.0 to 23.0 percent, nickel 4.5 to 6.5 percent, molybdenum 3.0 to 3.5 percent, and nitrogen 0.14 to 0.20 percent. The balanced composition maintains the approximately 50-50 ferrite-austenite structure that gives the grade its properties.

Mechanical Properties

UNS S32205 pipe has a minimum tensile strength of 655 MPa, a minimum yield strength of 485 MPa, and a minimum elongation of 25 percent, with maximum hardness of 293 HB or 31 HRC. The high strength allows thinner walls than austenitic grades for the same design pressure.

Heat Treatment

Duplex pipes are annealed at 1020 to 1100 degrees C followed by rapid cooling in air or water to restore the phase balance and corrosion resistance. Proper annealing is essential because slow cooling precipitates intermetallic phases that embrittle the material.

Applications

S32205 pipe is used in chemical processing, transportation and storage, oil and gas exploration and processing equipment, marine and other high-chlorine environments, pulp and paper digesters, wine tanks, and paper machines. It resists pitting, crevice corrosion, and stress corrosion cracking in chloride service.

Frequently Asked Questions

Q: What is the yield strength of S32205 pipe?

A: 485 MPa minimum.

Q: What is the maximum service temperature?

A: Below 300 degrees C to avoid embrittlement.

Q: What are the equivalents of S32205?

A: EN 1.4462, X2CrNiMoN22-5-3, and JIS SUS 329J3L.

Q: What applications use A790 S32205?

A: Oil and gas, chemical, marine, and pulp and paper service.

Q: Why choose duplex over austenitic?

A: Higher strength and resistance to chloride stress corrosion cracking.

Q: What sizes are available?

A: Seamless and welded pipes from 6 mm diameter up to large diameters on request.

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