Duplex stainless steel and Supper duplex stainless steel

Definitions

Duplex Stainless Steel
This refers to standard duplex stainless steel, a stainless steel with 22% chromium, with UNS S31803 and UNS S32205 (both known as Alloy 2205) being the most widely used. Common duplex stainless castings are UNS J92205 (ASTM A890 Grade 4A, CD3MN) and UNS J93372 (ASTM A890 Grade 1B, CD4MCuN). 

A 22%Cr duplex stainless steel a minimum 0.2% proof strength of some 450N/mm2 

Super Duplex Stainless Steel
A duplex stainless steel with a Pitting Resistance Equivalent Number (PREN) > 35-40, where PREN = % Cr + 3.3 × (% Mo + 0.5 % W) + 16 × % N. Usually, super duplex grades have 25 % chromium, or more. Some common examples are UNS S32760 (Zeron 100), UNS S32750 (Alloy 2507), and UNS S32550 (Ferralium 225). Common super duplex stainless steel castings are UNS J93380 (ASTM A890 Grade 6A, CD3MWCuN) and UNS J93404 (ASTM A890 Grade 5A, CE3MN).

A 25%Cr duplex stainless steel a minimum 0.2% proof strength of some 550N/mm2 .

Material inspection

Type of material may be marked by UNS designation or grade.

For forged fitting are almost identification by grade.

Example, for ASTM A182 Gr. F51/F55 as below photo are acceptable.

Size: 2" x Sch80S, Rate: 15000lbs, Production form: B16

Specification: ASTM A182 F51

Heat number: D20292, Manufacturer's logo: KMC, Complied with NACE MR0175

Example for piping fitting may be identified by grade or UNS designation

Example, for ASTM A815 UNS 31803 or Grade WPS31803 as below photo are acceptable.

Manufaturer: DAEKYUNG, Size: 2" 80S 90 LR, Specification: ASTM A815 UNS S31803 , Forming: S - Seamless pipe, Heat code: CFL0001, Complied with NACE MR0175

Pipe are also the same with pipe fitting which may be identified UNS designation.

UNS Designation: S32205

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Nguyen Duy Bien
 

Enjoy learning and researching, reading book. Knowledge welding inspection painting inspection.

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