Duplex Stainless Steel UNS 31803 (F51), UNS 32205 (F60)

Deriving the Duplex name from the presence of both Austenite and Ferrite in similar proportions, Duplex Stainless Steels combine excellent corrosion resistance with high strength. The typical mechanical properties would be double that of a single phase austenitic grade such as 316, while, for example, offering superior stress corrosion cracking resistance in chloride solutions.

Standard Duplex Stainless Steels typically have a 22% Chromium and 5% Nickel and in the 1960's Langley Alloys developed the first 25% Chromium Duplex alloy, Ferralium 255, and coined the phrase Super Duplex.

Duplex Stainless Steel is at the heart of the Langley Alloys business, with Langley Alloys being the ONLY supplier today offering its customer the complete choice on Duplex, and Super Duplex grades, with stock in the following grades:

22Cr Duplex:  UNS S31803 (F51) and UNS S32205 (F60)  Duplex 2205. 

Duplex 2205
Specification:
• EN 10088-3 1.4462
• ASTM A182 UNS S31803 Forgings Grade F51
• ASTM A182 UNS S32205 Forgings Grade F60
• ASTM A240 UNS S31803 Sheet and Plate
• ASTM A479 UNS S31803 Bar
• ASTM A479 UNS S32205 Bar
• ASTM A276 UNS S31803 Bar
• ASTM A76 UNS S32205 Bar
• Duplex 2205 Plate/Sheet
• Duplex 2205 Seamless & Welded Tube
• Duplex 2205 Seamless & Welded Pipe
• Duplex 2205 Round Bar
• Duplex 2205 Flanges F51
• Duplex 2205 Specialty Forgings
• Duplex 2205 Seamless & Welded BW Fittings

Trade Name	UNS	Duplex Stainless Steel Industry Specifications	Chemical Composition	Min.Tensile (KSI)	Min.Yield  (KSI)	Elongation  %
2205 22Cr	UNS S31803	ASME SA-182 (F51), SA-240, SA-798, SA-790, SA-815 ASTM A182 (F51),A240, A276, A479, A789, A790, A815, A928, A988 SAE J405	C 0.30 max  Cr 21.0-23.0 Mn 2.00 max Mo 2.50-3.50 N 0.08-0.20 Ni 4.50-6.50 P 0.030 max S 0.020 max Si 1.00 max	90	65	25
2205 22Cr	UNS S32205	ASME SA-182 (F60), SA-240, SA-798, SA-790, SA-815 ASTM A182 (F60), A240, A276, A479, A480, A798, A790, A815, A928, A988 SAE J405	C 0.30 max Cr 22.0-23.0 Mn 2.00 max Mo 3.00-3.50 N 0.14-0.20 Ni 4.50-6.50 P 0.030 max S 0.020 max Si 1.00 max	95	65	25

General Duplex stainless steel information

Duplex 2205 is the most widely used duplex (ferritic/austenitic) stainless steel grade. It finds applications due to both excellent corrosion resistance and high strength. The standard duplex S31803 composition has over the years been refined by many steel suppliers, and the resulting restricted composition range was endorsed as UNS S32205 in 1996. Duplex S32205 gives better guaranteed corrosion resistance, but for much of the Duplex S31803 currently produced also complies with Duplex S32205. 2205 is not generally suitable for use at temperatures above 300ºC as it suffers from precipitation of brittle micro-constituents, nor below -50ºC because of its ductile-to-brittle-transition.

Duplex Applications

Chemical processing, transport and storage,
Oil and Gas exploration and processing equipment,
Marine and other high chloride environments,
Pulp and paper digesters, liquor tanks and paper machines.

Duplex Corrosion Resistance

Excellent general corrosion resistance; superior to Grade 316 in most environments. Excellent resistance to localized corrosion including intergranular, pitting and crevice corrosion; the CPT of Duplex 2205 is generally at least 35ºC. The grade is also resistant to chloride stress corrosion cracking (SCC) 

at temperatures of up to about 150ºC. Grade Duplex 2205 will often perform well in environments which cause premature failure of austenitic grades. It has better resistance to sea water then Grade 316.

Duplex Heat Resistance

Although Duplex 2205 has good high temperature oxidation resistance, this grade - like other duplex stainless steels - suffers from embrittlement if held for even short times at temperatures above 300ºC. If embrittled, this can only be rectified by a full solution annealing treatment. Duplex stainless steels are almost never used above 300ºC.

Duplex Heat Treatment

Solution treatment (annealing) - heat to 1020ºC-1100ºC and cool rapidly. This grade cannot be hardened by thermal treatment, but does work harden.

Source: Yaang Pipe Industry Co., Limited (www.yaang.com)

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