ASTM A789 specification covers seamless tube and welded tube of duplex and super duplex (UNS S32205, UNS S31803, UNS S32760, UNS S32750) stainless steel. These duplex steel tubes are more prone to precipitation of sigma phase, nitrides and carbides than corresponding austenitic steels, causing embrittlement and reduced corrosion resistance. The formation of intermetallic phases such as sigma phase occurs in the temperature range 600-1000°C and decomposition of ferrite occurs in the range 350-500°C (475°C embrittlement). The high tensile strength of duplex steel tube also implies high fatigue strength. Due to their high chromium content, duplex steels offer excellent corrosion resistance in many media.
ASTM A789 Standard Specification for Seamless and Welded Ferritic/Austenitic Stainless Steel Tubing for General Service
2. Ordering Information
Quantity (feet, meters, or number of lengths),
Name of product (seamless or welded tubes)
Size (outside diameter and average wall thickness, unless minimum wall thickness is specified),
Length (specific or random)
Optional requirements (for product analysis; for hydrostatic or nondestructive electric test),
Test report required
3. Chemical Requirements
4. Tensile and Hardness Requirements
|Tensile and Hardness Requirements|
|UNS Designation||Tensile Strength, min, ksi (Mpa)||Yield Strength, min, ksi (Mpa)||Elongation in 2 in. or 50mm, min, %||Hardness, max.|
|S32750||116 (800)||80 (550)||15||300||32|
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