Z2CND22.05AZ Forgings (AFNOR Duplex 2205 / UNS S31803 / EN 1.4462)

Z2CND22.05AZ is the French AFNOR designation for 22% chromium duplex stainless steel, the alloy sold elsewhere as duplex 2205, UNS S31803 and EN 1.4462. Jiangyin Jiangnan Metal Co., Ltd. melts and open-die forges this grade at Jiangyin, Jiangsu. Forms include rolled rings, flanges, shafts, round bars, discs, tube sheets, sleeves, bushings and valve parts, supplied solution annealed with EN 10204 3.1 or 3.2 certification.

Composition and property data cross-checked against AFNOR, EN 10088-3 and ASTM A182 equivalents. Updated 11 October 2026.

What Z2CND22.05AZ is

Z2CND22.05AZ is the French notation for a duplex stainless steel of about 22% chromium, 4.5-6.5% nickel and 2.5-3.5% molybdenum, with 0.08-0.20% nitrogen added on purpose. The code breaks down element by element. Z marks a high-alloy steel. 2 is the carbon content in hundredths of a percent. C, N and D are the French symbols for chrome, nickel and molybdène. 22.05 gives the approximate chromium and nickel levels. AZ marks the low-carbon, nitrogen-alloyed variant.

The structure is roughly half ferrite and half austenite. Proof strength is about double that of austenitic 316 at a similar or lower nickel content, and resistance to chloride stress corrosion cracking and pitting is far better. Virgamet's comparison table lists AFNOR Z3CND22-05AZ next to EN 1.4462, UNS S31803, ISO CrNiMo22-5-3, BS 318S13, GOST 02Ch22N5M3 and SAF 2205 as one alloy under different national systems.

Equivalent grades and cross-references

These grades are equivalent, not identical. Silicon, phosphorus and sulphur limits differ between the AFNOR, EN, BS and JIS versions, and S32205 is a tighter specification than S31803. State on the purchase order which standard governs and the heat will be aimed to satisfy it. Material often passes dual certification to S32205 and S31803; the reverse does not hold.

Chemical composition

Some mill datasheets for S31803 bar quote nitrogen as 0.10-0.22% rather than 0.08-0.20%, and buyers ordering to S32205 should expect 0.14-0.20%. Nitrogen raises pitting resistance and stabilises the austenite phase, so a specified minimum nitrogen or minimum PREN has to be known at enquiry stage and built into the melt aim.

Pitting resistance equivalent

PREN is usually calculated as Cr% + 3.3 × Mo% + 16 × N%. A typical 2205 chemistry gives 33 to 36 on that formula. Published tables list UNS S31803 at about 36, and suppliers who guarantee a floor commonly offer PREN above 34 by agreement. The 30 × N variant of the formula returns a higher figure, near 38, so confirm which version your specification intends before treating a PREN number as a pass or a failure. Super duplex grades such as A182 F55 exceed 40.

Mechanical properties

The EN 10088-3 figures above apply to solution-treated bar up to 160 mm diameter. Heavier sections cool more slowly through the core, so properties on thick rings and tube sheets are verified on a test piece representing the delivered thickness rather than taken from the bar table.

Behaviour at temperature

Modulus and proof strength fall as temperature rises, to roughly 194 GPa and 360 MPa proof at 100 °C and 186 GPa and 315 MPa at 200 °C. The real ceiling is metallurgical rather than mechanical. European practice generally caps continuous service at 200-250 °C, while ASTM-oriented guidance for F51 cites about 315 °C (600 °F). Long exposure in that range precipitates sigma and other embrittling phases and toughness collapses. For hotter duty, ask about austenitic or nickel grades such as Incoloy 825 or Inconel 625.

Corrosion resistance

Z2CND22.05AZ resists intergranular corrosion, pitting and crevice attack. Its main advantage over 304 and 316 is resistance to chloride stress corrosion cracking. Published data for 1.4462 shows it holding up in concentrated chloride media, including calcium chloride, lithium chloride and sodium chloride solutions at raised temperature, where standard austenitic grades crack. The low carbon keeps the grade resistant to intergranular attack after welding without any stabilising addition.

Set against 316, the practical comparison is roughly double the proof strength, a PREN near 35 against about 26, and much better chloride SCC performance. The higher strength often allows a thinner section, which recovers part of the higher price per kilogram. It is not a super duplex: for warm seawater or severely sour service, move up to F53 or F55.

Forging, heat treatment and machining

Forging and solution annealing

Parts are hot forged as near to finished shape as the geometry allows, cooled below about 540 °C, then solution annealed at 1020-1100 °C and water quenched. The quench has to be fast enough to suppress sigma phase and other intermetallics, so section thickness, furnace-to-tank transfer time and quench tank capacity all matter on heavy duplex rings, tube sheets and shafts. Fourteen heat-treatment furnaces serve the forge line.

Melting route

Duplex grades are melted in the electric arc furnace, refined in the ladle furnace and decarburised under vacuum, which is the route that delivers both the low carbon and the controlled nitrogen this alloy depends on. Heats run to 60 tonnes. Electroslag remelting is available where tighter cleanliness or a specified remelt route is called for. Melting happens on site, so the certificate traces the part back to its melt number instead of stopping at a purchased billet.

Machining notes

The grade work hardens quickly and is harder on tooling than 316 or 316L, so austenitic settings cannot simply be reused. Use coated cemented carbide, rigid setups, well-reduced cutting speed and plenty of coolant. Cut the feed only slightly and with care, because too light a feed glazes the surface, work hardens the layer ahead of the tool and shortens tool life. Parts can be supplied as forged with allowance, proof-machined for ultrasonic inspection, or finish-machined to drawing.

Product forms in Z2CND22.05AZ

Where the grade is used

Specifiers reach for it where chlorides, moderate H₂S or aggressive process chemistry rule out 304 and 316, and where the higher yield strength buys a thinner section. Forged parts in this alloy go into offshore and subsea oil and gas hardware such as wellheads, Christmas trees, manifolds, spools and downhole components for moderately sour wells. They go into seawater and desalination service, including firewater and cooling systems, high-pressure reverse osmosis connections, separator and heat exchanger parts. Chemical and petrochemical plant uses them for brine and chloride-bearing acid duty, crystalliser equipment and reactor nozzles. Pulp and paper mills use them in digesters, liquor tanks, machine rolls and shafts. Power and rotating equipment applications cover turbine and gas compressor parts, gearbox components, industrial air compressors and nitrogen generators. Marine and heavy machinery work includes shipbuilding components, forged rolls, wheels and pressure vessel sections.

Testing, inspection and certification

The works holds CCS, BV, DNV, LR and NK approvals. Corrosion and phase-balance testing on duplex material is booked with an outside accredited laboratory, so flag any ASTM A923 or G48 requirement at enquiry stage and it goes into the quoted delivery date rather than on top of it.

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