Stainless

2205 Duplex

Stainless Steel – 2205 Duplex (UNS S31803/S32205)
  • a Duplex Austenitic/ Ferritic stainless steel
Typical Analysis
Fe Cr Mo Ni Si Mn C N P S
Bal 21-
23		 2.5-
3.5		 4.5-
6.5		 1.0
Max		 2.0
Max		 .03
Max		 .08-
.2		 .03
Max		 .02
Max
Characteristics
  • High Strength AND
  • Duplex UNS S31803/S32205 is a ferritic-austenitic stainless combining high mechanical strength, ductility and hardness with excellent resistance to corrosion and erosion.
Mechanical Properties
  • Mechanical Test Requirements:
    • Tensile - 90,000 psi min
    • Yield - 65,000 psi min
    • Elongation - 25 % min
    • Hardness - 293 HBN Max
  • Corrosion Resistance:
    • The corrosion resistance of S31803/S32205, under most conditions of service, is superior to that of the fully austenitic type 304, 316 and 317L stainless steels. It has excellent resistance to sulfuric, phosphoric, nitric, and many other acids and salts.
    • Duplex UNS S31803/S32205 is highly resistant to acetic, formic and other organic acids and compounds. It is particularly suitable for the higher concentrations and temperatures where pitting and preferential corrosion are common causes of failure with most conventional austenitic stainless steels in the presence of chlorides and other impurities. Like the austenitic stainless steels, S31803 is not generally suitable for handling hydrochloric acid and other severely reducing acids and chemicals.
  • Stress-Corrosion Resistance:
    • Resists Chloride Stress Corrosion Cracking
    • Duplex UNS S31803/S32205 has improved resistance to stress-corrosion cracking, crevice corrosion and pitting when compared to austenitic stainless steels such as types 304, 316, 317L and even the 20Cr-25Ni grades. It is highly resistant to stress-corrosion cracking in sodium chloride, seawater and many other environments.
Fabrication
  • Hot forming is carried out at 1150-950˚C. However, it should be borne in mind that the mechanical strength of the material is low at high temperatures. At temperatures below 950˚C embrittling can take place on account of the combination of strain and exposure in the sigma phase field. Quench annealing is normally required after hot forming.316, 317L and even the 20Cr-25Ni grades. It is highly resistant to stress-corrosion cracking in sodium chloride, seawater and many other environments.
  • Cold forming owing to the high yield strength of the steel, greater forces are normally required for the cold forming of S31803/ S32205 than for austenitic steels.
Machining
  • High alloy duplex steels, such as S31803/S32205, are generally more difficult to machine than conventional austenitic stainless steels such as 17-12-2.5. Duplex steels have a somewhat different property profile than highly alloyed austenitic stainless steels. The main difference is that duplex grades are relatively easier to machine with high speed steel tools than with cemented carbide tools, compared to austenitic stainless steels with a similar alloy content.
Welding
  • Duplex UNS S31803/ S32205 possesses good weldability. The following instructions should be followed:
    • The material should be welded without preheating.
    • The material should be allowed to cool between passes, preferably to below 150℃.
    • The recommended heat input in order to achieve a good balance between ferrite and austenite in the weld is 1.0-2.5 kJ/mm (aim at 30-60% ferrite). The energy input should be adjusted in proportion to the thickness of the material to be welded. A high energy input and slow cooling reduce the amount of ferrite.
  • Duplex UNS S31803/ S32205 can be welded using the following methods:
    • Welding with covered electrodes (SMAW)
    • Gas shielded arc welding such as GTAW (TIG), plasma, GMAW (MIG) and FCW.
    • Submerged-arc welding (SAW)
  • Post weld heat treatment is not normally necessary. In cases where heat treatment is considered, for example for stress relieving, this should be carried out at 1020-1070℃.
Applications
  • Because of its resistance to chloride pitting and stress-corrosion cracking, S31803/S32205 is finding wide use in place of austenitic stainless steels for handling solutions containing chlorides such as in marine scrubbers. As a result of its wear, erosion and corrosion resistance, S31803/S32205 is particularly suitable for pumps, agitators and other critical components handling hot corrosive slurries.
  • Special mention should be made of its performance in the production of fertilizer grade phosphoric acid by the "wet" process where the alloy finds extensive application.
  • Some of the areas or industries of present or potential use for S31803/S32205 products follow:
Chemical Process Industry: Equipment Handling Fatty Acids, Terephthalic Acid and Polytheonic Acid, Sulfuric Acid Protection, Tank Internals, Rakes, Fasteners in Uranium Extraction
Copper Smelting: Sulfuric Acid Production, Leaching Area, Precipitators, I.D. Fans, Wet Scrubbers, Tuyere Bars
Marine: Propeller Shaftings, Cutlass Bearings Seals, Rudders, Desalinization Equipment, Pump Parts, Feed Water Heaters, Fasteners for Off-Shore Platform Gauges
Oil & Gas: Injection Pumps, Processes for Treating Crude Oil i.e. Desalting, Desulfurization and Distillation, Mild Sour Gas Wells
Petrochemical: Styrene Monomer Wash Acid Equipment, PVC film Extrusion Dies, Solvent Recovery Absorbers, Low Density Polypropylene Dryer Baffles, Entrainment Separators, Handling Hot Organic Acids i.e. Acetic, Formic, Oxalic Acids With or Without Chlorides Present
Pollution Control: Centrifuges (Waste Water Clarification), Venturi Scrubbers for Sewage Incinerators, SO2 Scrubbers, Roast Gas Scrubbers (Fan and Vessels), Fans for Garbage Incinerators, Sodium Hypochlorite Scrubbers
Pulp & Paper Black Liquor Heater Tubes, Digester Blow Valves, Rotary Feed Valves, I.D. Fans, Brownstock Washers, Digester Strainer Plates, Agitator Assemblies (Bleach Plt Mixer), Cyclone Target Plates, Precipitators, Wet Scrubbers, Pump Parts, Recovery Furnace Boiler Tubes, Bleach Agitator Shafts
Wet Phosphoric Acid Production Digester Agitators, Mixing Tees, Vortex, Piping, Breakers, Centrifuge Parts, Pump Parts, Valves
Urea Porduction Decomposer Tubes, Pump Parts, Valves, Bolts
ASME Boiler & Pressure Vessel Code Case
  • Duplex UNS S31803/S32205 sheet, strip, plate, bar, pipe and tubing are covered in ASME Boiler and Pressure Vessel Code, Section VIII, Division I.
Specifications
  • Duplex UNS S31803/S32205 is covered by the following ASTM, ASME specifications:
  • ASTM A182/ASME SA-182: Forged or rolled alloy-steel pipe, flanges, forged fittings, and valves and parts for high temperature service
  • ASTM A240/ASME SA-240: Heat resisting Cr and CrNi stainless steel, plate, sheet, strip for fusion-welded unfired pressure vessels
  • ASTM A789: Seamless and welded ferritic/austenitic stainless steel tubing for general service
  • ASTM A790: Seamless and welded ferritic/austenitic stainless steel pipe

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