Stainless Steel, Duplex
2205 Stainless Steel (S32205)
A duplex austenitic-ferritic chromium-nickel-molybdenum stainless steel.
Duplex stainless steels are extremely corrosion resistant, work hardenable alloys. Their microstructures consist of a mixture of austenite and ferrite phases. As a result, duplex stainless steels display properties characteristic of both austenitic and ferritic stainless steels. This combination of properties can mean some compromise when compared with pure austenitic and pure ferritic grades.
Duplex stainless steels are in most cases, tougher than ferritic stainless steels. Strengths of duplex stainless steels can in some cases be double that for austenitic stainless steels.Whilst duplex stainless steels are considered resistant to stress corrosion cracking, they are not as resistant to this form of attack as ferritic stainless steels. However, the corrosion resistance of the least resistant duplex stainless steels is greater than that for the most commonly used grades of stainless steels, i.e. 304 and 316.
Duplex steels are also magnetic, a property that can be used to easily differentiate them from common austenitic grades of stainless.
Property data given in this document is typical for bar products covered by EN standards. ASTM, EN or other standards may cover products sold. It is reasonable to expect specifications in these standards to be similar but not necessarily identical to those given in this datasheet.
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Range
| Product Form | Imperial Sizes | Metric Sizes |
| Round Bar Peeled K12 | 4" | 100mm |
PLEASE NOTE
If you do not see what you are looking for, please contact your local service centre with your specific requirements.
S32205 Stainless Steel Related Specifications
| System / Standard | Country / Region | Grade / Designation |
| UNS | International | S32205 |
| UNS | International | S31803 |
| EN / W.Nr. | Europe | 1.4462 |
| EN / ISO Name | Europe / ISO | X2CrNiMoN22-5-3 |
| ASTM A240 | USA | 2205 (UNS S32205/S31803) |
| ASTM A276 | USA | 2205 (bars, S32205/S31803) |
| ASTM A182 | USA | F51 (UNS S31803) |
| ASTM A182 | USA | F60 (UNS S32205) |
| ASTM A789/A790 | USA | S32205 / S31803 |
| GB | China | 022Cr22Ni5Mo3N |
| GB | China | S22053 |
| JIS G4303/G4304 | Japan | SUS329J3L |
| BS | UK | 318S13 |
| AFNOR | France | Z3CND22-05Az |
| GOST | Russia | 02Ch22N5M3 (02Х22Н5АМ3) |
| Trade name | International | SAF 2205 |
| Trade name | International | UR 45N / URANUS 45N |
Properties
Chemical Composition
2205 Steel
| Chemical Element | % Present |
| Carbon (C) | 0.00 - 0.03 |
| Chromium (Cr) | 21.00 - 23.00 |
| Manganese (Mn) | 0.00 - 2.00 |
| Silicon (Si) | 0.00 - 1.00 |
| Phosphorous (P) | 0.00 - 0.03 |
| Sulphur (S) | 0.00 - 0.02 |
| Nickel (Ni) | 4.50 - 6.50 |
| Nitrogen (N) | 0.10 - 0.22 |
| Molybdenum (Mo) | 2.50 - 3.50 |
| Iron (Fe) | Balance |
Mechanical Properties
Bar Up to 160mm Dia/Thickness
| Mechanical Property | Value |
| Proof Stress | 450 Min MPa |
| Tensile Strength | 650 to 880 MPa |
| Elongation A50 mm | 25 Min % |
| Hardness Brinell | 270 Max HB |
General Physical Properties
| Physical Property | Value |
| Density | 7.805 g/cm³ |
| Thermal Expansion | 13.7 x10-6/K |
| Modulus of Elasticity | 200 GPa |
| Thermal Conductivity | 19.0 W/m.K |
| Electrical Resistivity | 0.85 x10-6 Ω .m |
Applications of 2205 Stainless Steel
2205 duplex stainless steel (UNS S32205 / S31803, EN 1.4462) combines high yield strength (≈2× 304/316) with excellent resistance to pitting, crevice corrosion and chloride stress-corrosion cracking, so it’s widely used anywhere 304/316 are “not quite enough” in chlorides or where higher strength is needed.
1. Chemical and Petrochemical Process Equipment
Process piping and manifolds handling chloride-containing or mildly acidic media
Reactors, columns, scrubbers and absorbers where 304/316 risk pitting or SCC
Heat-exchanger shells, channels and tube sheets in chemical plants
Agitated vessels and mixers where corrosion-fatigue resistance is important
2. Oil & Gas, Offshore and Subsea Applications
Topside and subsea process piping, manifolds and riser components
Separation vessels, scrubbers and produced-water handling systems
Pump bodies, shafts, valves and fittings exposed to chlorides, CO₂ and H₂S (within the grade’s sour-service limits)
Structural parts and hardware on offshore platforms and FPSOs subject to seawater spray and cyclic loading
3. Pulp, Paper and Bleaching Systems
Digesters, bleaching towers and washers in sulfate and sulfite pulping
White, green and black liquor handling equipment and piping
Evaporators, heat exchangers and condensers in aggressive pulp liquors
Components needing both high strength and strong resistance to stress-corrosion and corrosion-fatigue in hot alkaline / chloride environments
4. Desalination, Water and Wastewater Treatment
High-pressure piping and vessels in RO desalination plants (feed, brine and permeate lines)
Evaporator shells, brine heaters and flash chambers in thermal desalination units
Large water storage tanks, clarifiers and structural hardware in water and wastewater plants
Sluice gates, penstocks, pump housings and other hydraulic structures exposed to brackish or seawater
5. Marine, Structural and Bridge Components
Shipbuilding structures, decks, ramps and cargo-handling hardware in splash and tidal zones
Cargo tanks and piping in chemical tankers for chlorides and mildly corrosive chemicals
Bridge components, pedestrian bridges and structural members exposed to marine atmosphere or de-icing salts
Reinforcing bars (stainless rebar) in coastal or chloride-contaminated concrete structures
6. General Mechanical Components, Heat Exchangers and Fabrications
High-strength flanges, fittings, fasteners and shafts in corrosive industrial environments
Plate-and-frame or shell-and-tube heat exchangers in seawater or process-water service
Tank roofs, bottoms and stiffeners where 304/316 lack strength or corrosion margin
Agitator shafts, couplings, supports and frames that need both strength and chloride resistance
Summary
2205 duplex stainless steel is widely used in chemical and petrochemical plant, oil & gas (onshore/offshore), pulp and paper, desalination and water treatment, marine structures, bridges and high-strength mechanical components, wherever designers need significantly higher strength than 304/316 together with much better resistance to pitting, crevice attack and chloride stress-corrosion cracking, especially in seawater, brackish water and chloride-rich industrial environments.
Characteristics of 2205 Stainless Steel
2205 duplex stainless steel (UNS S32205 / S31803, EN 1.4462) is a duplex (austenite + ferrite) grade that combines high strength, excellent resistance to localized corrosion in chlorides, and very good resistance to stress-corrosion cracking, making it one of the most widely used duplex alloys.
1. Duplex (Austenite + Ferrite) Microstructure
Roughly 50% ferrite / 50% austenite in the solution-annealed condition.
Duplex structure gives a balance of high strength, good toughness and strong SCC resistance.
Microstructure is more stable than straight austenitic grades in warm chloride service, which helps prevent cracking and corrosion-fatigue.
2. High Yield Strength and Structural Efficiency
Yield strength is typically about twice that of 304L / 316L.
Allows designers to use thinner walls and lighter sections for the same design load.
Particularly advantageous for tanks, pressure piping, structural members and marine hardware where both strength and corrosion resistance are critical.
3. Excellent Resistance to Pitting and Crevice Corrosion
High chromium and molybdenum plus nitrogen give a high pitting resistance equivalent number (PREN), significantly higher than 304L and 316L.
Very good resistance to pitting and crevice attack in seawater, brackish water and chloride-bearing process streams.
Suitable for desalination, offshore, pulp & paper liquors and many chemical process environments where 316L would be borderline.
4. Very Good Resistance to Chloride Stress-Corrosion Cracking
Duplex structure makes 2205 far less susceptible to chloride SCC than austenitic 304/316, especially at elevated temperatures and under tensile stress.
Widely used in services where 304/316 have a history of SCC failures (warm chlorinated waters, coastal structures, hot process waters).
This SCC resistance is a major reason for its popularity in oil & gas, desalination, cooling-water and marine systems.
5. Good General Corrosion and Erosion-Corrosion Behaviour
Provides good resistance to uniform corrosion in many acids, alkalis and industrial environments at moderate concentrations and temperatures.
Performs well under flowing, turbulent and erosive conditions, such as pump casings, piping, and agitator components in corrosive media.
In many real-world applications it offers a clear corrosion margin over 316L, extending service life.
6. Toughness and Low-Temperature Performance
Toughness is lower than austenitic grades but still good for most structural and pressure applications.
Maintains useful impact toughness down to quite low temperatures when correctly produced and fabricated.
Toughness can be reduced if intermetallic phases form (e.g. from over-heating or improper heat treatment), so temperature control in fabrication is important.
7. Weldability with Duplex-Specific Procedures
2205 is readily weldable, but welding must follow duplex-specific guidelines:
Controlled heat input and interpass temperature to maintain the ferrite–austenite balance.
Duplex or over-alloyed austenitic filler metals to match or exceed base-metal corrosion resistance.
Correct procedures yield welds with good toughness and corrosion resistance close to the parent metal; poor procedures can lead to intermetallics and property loss.
8. Mechanical and Physical Property Balance
Higher modulus and lower thermal expansion than 304/316 improve dimensional stability in structural and temperature-cycling applications.
Magnetic in all conditions due to the ferrite phase (unlike annealed austenitics, which are essentially non-magnetic).
Good fatigue and corrosion-fatigue performance in many aqueous and marine environments.
Summary
2205 duplex stainless steel combines a duplex microstructure, high yield strength, excellent pitting/crevice resistance, very good resistance to chloride stress-corrosion cracking, decent toughness and good weldability (with proper procedures), making it a workhorse material for demanding chloride-containing and high-load applications where 304/316 are not strong or corrosion-resistant enough.
Additional Information
Weldability
Weldability of 2205 Stainless Steel
2205 duplex stainless steel (UNS S32205 / S31803, EN 1.4462) has good weldability, but—like all duplex grades—welding must follow duplex-specific procedures to preserve the correct ferrite–austenite balance and maintain toughness and corrosion resistance.
1. General Weldability Characteristics
2205 can be welded with all common stainless-steel welding processes.
Compared with 304/316, it is less tolerant of poor procedures because:
Too much ferrite → reduced toughness and corrosion resistance.
Intermetallic phase formation (from too much heat / slow cooling) → embrittlement and pitting susceptibility.
When heat input, filler metal and interpass temperature are controlled, welds can match the strength and corrosion resistance of the base metal very closely.
2. Suitable Welding Processes
Commonly used processes include:
GTAW (TIG) – for root passes and thin sections, excellent control.
GMAW (MIG/MAG) – for production welding of plate, piping and structural work.
SMAW (MMA) – for site and repair welding with duplex-coated electrodes.
FCAW – for higher deposition rates in fabrication shops using duplex flux-cored wire.
Autogenous welding (no filler) is generally not recommended except for very thin gauges, because filler composition is important to restore the desired phase balance and corrosion resistance.
3. Filler Metal Selection
Filler metals are typically duplex or slightly over-alloyed austenitic grades designed for 2205.
Requirements for filler:
Achieve a weld metal pitting resistance at least equal to the base metal.
Produce an appropriate ferrite–austenite balance in weld metal after cooling.
In practice:
Duplex fillers specifically rated for 2205 (or with slightly higher alloy content) are preferred for most services.
Over-alloyed austenitic fillers may be used for special joints where maximum weld toughness is required, but base-metal strength and service conditions must be considered.
4. Heat Input, Interpass Temperature and Cooling
Moderate heat input is essential:
Too low → excessive ferrite, low toughness, poorer corrosion resistance.
Too high / too slow cooling → risk of sigma and other intermetallic phases, especially in heat-affected zones.
Typical practice (conceptually):
Use a controlled heat-input window recommended for duplex steels.
Limit interpass temperature (often in a relatively low range) to prevent overheating and phase imbalance.
Allow welds to cool in still air; quenching is not used.
Correct control ensures weld metal and HAZ keep a balanced duplex microstructure with good mechanical and corrosion properties.
5. Weld Microstructure, Properties and Corrosion Behaviour
Properly welded 2205 joints show:
Duplex weld metal and HAZ with a suitable ferrite–austenite ratio.
High strength, often close to or slightly above base metal, depending on filler and procedure.
Good impact toughness, including in the transverse direction for structural and pressure applications.
Corrosion resistance (pitting, crevice, SCC) comparable to the base metal in chloride-containing environments.
Poor welding practice can cause:
Ferrite-rich welds with reduced toughness and lower resistance to localized corrosion.
Formation of intermetallic phases → embrittlement and poor pitting resistance, especially in the HAZ.
6. Joint Design, Preparation and Post-Weld Cleaning
Joint design:
Avoid excessive restraint and severe notch-like geometries at weld toes.
Provide good access for torch, wire and subsequent cleaning/pickling.
Preparation:
Clean joint faces thoroughly (remove oil, paint, rust, zinc and other contaminants).
Use proper back-gouging and backing gas on root passes (especially for pipe and tank welding) to avoid heavy oxidation on the root.
Post-weld:
Remove slag, spatter and heat tint by grinding or pickling.
Use proper pickling/passivation to restore a clean, chromium-rich passive film and full corrosion resistance.
7. Post-Weld Heat Treatment (PWHT)
In most applications, no PWHT is required for 2205 if welding is done correctly.
Standard post-weld tempering cycles used for carbon steel are not suitable and can harm duplex properties.
If a specification calls for any heat treatment, it must follow duplex-specific guidance, as inappropriate temperatures/time can form intermetallic phases and drastically reduce toughness and corrosion resistance.
Summary
2205 duplex stainless steel has good weldability but must be welded using duplex-focused procedures: controlled heat input and interpass temperature, correct duplex or over-alloyed austenitic fillers, proper joint design, good root shielding and thorough post-weld cleaning are all essential to maintain a balanced duplex microstructure, high strength, good toughness and the excellent localized-corrosion and SCC resistance that make 2205 so valuable in demanding chloride-containing and high-load applications.
Fabrication
Fabrication of 2205 Stainless Steel
2205 duplex stainless steel (UNS S32205 / S31803, EN 1.4462) is a high-strength, corrosion-resistant alloy that can be fabricated successfully using standard stainless-steel shop practices, as long as duplex-specific rules for forming, welding and heat input are followed.
1. General Fabrication Approach
Supplied mainly in the solution-annealed and pickled condition (plate, pipe, tube, bar).
Most forming, machining and welding should be done in this condition.
Yield strength ≈ 2× 304/316, so:
Higher forming and cutting forces
Potential for more spring-back in bending and rolling
Fabrication planning should integrate:
Forming sequence
Welding sequence and access
Final tolerances and distortion control
2. Forming and Cold Working
2205 has good formability, but lower ductility than austenitic 304/316.
Practical guidance:
Use larger bend radii than for 304/316 to avoid edge cracking.
Apply forming in gradual steps with good lubrication and smooth tooling.
Expect increased spring-back; allow for it in tooling and angles.
For severe forming (deep drawing, tight radii in thicker plate):
Use trial pieces to verify radii and spring-back.
If very heavy cold work is applied, consider solution annealing to restore toughness and corrosion resistance for critical service.
3. Hot Working and Heat Treatment in the Route
Hot working (forging, hot bending/rolling) is similar to other duplex grades:
Work in an appropriate high-temperature range with sufficient reductions.
Avoid long holds at peak temperature to limit grain growth and intermetallic formation.
After significant hot work, a solution anneal + rapid cooling is typically used to:
Re-establish a balanced duplex (ferrite + austenite) microstructure
Maximise toughness and corrosion resistance
Final components are generally used in the solution-annealed condition, with no further PWHT after proper welding.
4. Machining
Machinability is moderate, more demanding than 304/316 due to higher strength and work hardening.
Good practice:
Use carbide tooling and rigid setups.
Run moderate speeds with adequate feed to avoid rubbing.
Provide plenty of coolant for heat and chip control.
Process route:
Do rough machining before final welding/straightening if possible.
After all welding and solution anneal (if used), finish with light machining or grinding to bring parts to final size and surface finish.
5. Welding Within the Fabrication Process
2205 is readily weldable, but must follow duplex procedures:
Controlled heat input and interpass temperature.
Duplex or over-alloyed austenitic fillers to match or exceed base-metal corrosion resistance.
Proper backing gas and shielding for root quality in pipe and tank welding.
Normal route:
Form and fit in the solution-annealed condition.
Weld with qualified duplex WPS/PQR.
No PWHT in most cases; focus on thorough post-weld cleaning instead.
6. Surface Cleaning, Pickling and Passivation
To achieve full corrosion performance, 2205 surfaces and welds must be properly cleaned:
Remove slag, spatter and heat tint by grinding, brushing or blasting.
Apply pickling (or suitable mechanical cleaning) and passivation as required.
Aim for smooth, defect-free surfaces, especially in chloride or crevice-sensitive service.
Clean, well-finished surfaces significantly improve pitting, crevice and SCC resistance in service.
7. Distortion, Residual Stresses and Dimensional Control
Higher strength and lower thermal expansion than austenitics give good dimensional stability, but:
Welding still introduces residual stresses.
Cold work (forming, straightening) can store significant strain.
Practical controls:
Use balanced welding sequences and adequate fixturing.
Avoid excessive local cold straightening in highly stressed or corrosive regions.
For critical parts, plan:
Form → Weld → Straighten (light) → Finish machine / grind
to lock in dimensions after major distortion sources.
Summary
2205 duplex stainless steel is straightforward to fabricate when treated as a high-strength duplex alloy: do most forming and machining in the solution-annealed condition, use duplex-specific welding procedures, and always finish with proper cleaning, pickling/passivation and light final machining or grinding to deliver a balanced duplex microstructure, high strength, excellent corrosion resistance and reliable dimensional accuracy in demanding service.
Hot Working
Hot Working of 2205 Stainless Steel
2205 duplex stainless steel (UNS S32205 / S31803, 1.4462) can be hot worked successfully, but temperature control and cooling are critical to preserve a good ferrite–austenite balance and avoid intermetallic phases.
1. Recommended Hot Working Temperature Range
Typical hot-working / forging range: about 950–1,150°C.
Start deformation toward the upper end of the range for best plasticity.
Finish hot working above ~900°C to reduce the risk of cracking as ductility drops at lower temperatures.
Always follow the specific mill datasheet for the product you are using (plate, bar, forging stock).
2. Heating and Forging Practice
Heat material slowly and uniformly through the full section before heavy deformation.
Use substantial reductions per pass rather than light tapping to refine grains and avoid banding.
Reheat when the workpiece temperature approaches the lower limit of the working range.
Avoid overheating or long soaking at the maximum temperature to limit grain growth and excessive scaling.
3. Cooling and Subsequent Heat Treatment
After hot working, cool components in still air or controlled conditions.
For heavily hot-worked sections, perform a full solution anneal + rapid cooling to restore optimum properties:
Heat to the recommended solution-annealing range for 2205 (per supplier spec).
Soak for full through-heating.
Rapidly cool (usually water quench or very fast air) to lock in the correct duplex microstructure.
Avoid very slow cooling through the 600–1,000°C region, which can promote intermetallic phase formation and embrittlement.
4. Surface Scale, Machining Allowance and Cleaning
At hot-working temperatures, 2205 will form oxide scale and some surface roughness.
Leave adequate machining or grinding allowance to remove scale and any decarburised / damaged surface layer.
After hot working and any solution anneal, use pickling and/or mechanical cleaning plus passivation to restore a clean, metallic, chromium-rich surface for best corrosion resistance.
5. Effect on Microstructure and Properties
Correct hot working in the proper temperature range followed by solution annealing produces a fine, balanced ferrite–austenite structure.
Benefits include:
Good toughness and ductility
High and consistent yield strength
Excellent pitting, crevice and SCC resistance in service
Poor control (working too cold, overheating, slow cooling) can cause:
Coarse grains and reduced toughness
Formation of sigma and other intermetallic phases, which seriously degrade impact toughness and localized-corrosion resistance.
6. Design, Distortion and Cracking Control
Design preforms and forgings with smooth transitions, generous radii and uniform section thickness to reduce internal stresses.
Avoid sharp corners, heavy local reductions and abrupt thickness changes that can cause cracking during forging or cooling.
For long shafts, rings or complex shapes, ensure proper support and handling during hot working and cooling to minimise bending and distortion.
Inspect forgings for laps, folds and surface cracks before committing to final heat treatment and machining.
Summary
Hot working of 2205 stainless steel should be carried out in the 950–1,150°C range with uniform heating, substantial reductions and controlled air cooling, followed where necessary by solution annealing and rapid cooling; careful control of temperature, deformation, cooling and surface cleanup is essential to maintain a fine, balanced duplex microstructure and to achieve the high strength, toughness and excellent corrosion resistance expected from 2205 in demanding chloride-containing and high-load applications.
Heat Resistance
Heat Resistance of 2205 Stainless Steel
2205 duplex stainless steel (UNS S32205 / S31803, EN 1.4462) is designed mainly for ambient to moderately elevated temperature service in corrosive, chloride-bearing environments. It keeps its strength and corrosion resistance well at moderate temperatures, but it is not a high-temperature / creep-resistant alloy.
1. Recommended Service Temperature Range
2205 is typically used from sub-zero temperatures up to about 250–300°C in continuous service.
Within this range it maintains:
High yield strength (still well above 304L/316L at the same temperature)
Good toughness and corrosion resistance
For long-term exposure above this range, especially in corrosive service, duplex steels can suffer:
Loss of toughness
Reduced pitting and crevice-corrosion resistance
Formation of embrittling intermetallic phases
2. Strength and Toughness at Elevated Temperatures
As temperature increases, 2205 behaves like other steels:
Yield and tensile strength decrease, but remain higher than 304L/316L at the same temperature.
Fatigue strength drops with temperature and cyclic loading.
In the recommended range it offers:
Very good strength-to-weight ratio for tanks, piping and structural members
Adequate impact toughness for most pressure and structural services
At temperatures held for long periods in the mid to high range, toughness can decline sharply if the microstructure is damaged by precipitates.
3. Hot Chloride Environments and SCC Behaviour
A key advantage of 2205 is its excellent resistance to chloride stress-corrosion cracking (SCC) compared with 304/316, especially at elevated temperatures.
In warm seawater, brackish waters and hot process waters:
304/316 can crack under tensile stress and chlorides
2205 usually remains resistant within its normal temperature and stress limits
This makes 2205 especially valuable in:
Desalination plants
Cooling-water and heat-exchanger systems
Offshore and marine piping and structural components
4. Oxidation and Scaling Resistance
Chromium content gives 2205 good oxidation resistance in air and flue-gas-type atmospheres at moderate temperatures.
It will tolerate short-term excursions to much higher temperatures (for example during fabrication, heat-up/slow-down cycles, or cleaning operations), but:
Mechanical properties and corrosion resistance in service are not guaranteed for continuous operation at those higher temperatures.
For sustained high-temperature, dry-gas or furnace service, dedicated heat-resistant austenitic or nickel alloys are normally preferred.
5. Microstructural Stability and Intermetallic Phases
Duplex steels, including 2205, can form intermetallic phases (e.g. sigma phase) and experience 475°C-type embrittlement if held too long in intermediate/high temperature ranges.
These phases:
Severely reduce impact toughness
Impair pitting and crevice-corrosion resistance
Can make the steel more sensitive to cracking under load
Because of this, continuous long-term service at intermediate to high temperatures is limited; fabrication heat treatments and welding procedures are carefully controlled to minimise time in these temperature bands.
6. Design Considerations for Elevated-Temperature Service
Treat 2205 as a high-strength, corrosion-resistant structural alloy for moderate temperatures, not as a creep-resistant high-temperature material.
In design you should:
Keep continuous operating temperatures within the recommended band (typically ≤250–300°C).
Use appropriate allowable stresses that reflect the loss of strength with temperature.
Avoid designs that create local heat traps or long exposures in intermetallic-forming temperature regimes.
Combine correct material choice with good surface finish, weld procedures and inspection intervals in hot, chloride-bearing environments.
Summary
2205 duplex stainless steel offers reliable heat resistance for structural and process equipment operating at moderate temperatures, retaining much higher strength than 304/316 and excellent resistance to chloride SCC in warm, corrosive environments; however, it is not intended for long-term, high-temperature or creep-critical service, where prolonged exposure can promote intermetallic phases and property loss, and more highly alloyed heat-resistant stainless or nickel alloys should be selected instead.
Machinability
Machinability of 2205 Stainless Steel
2205 duplex stainless steel (UNS S32205 / S31803, 1.4462) has moderate machinability: clearly more demanding than 304/316 because of its higher strength and work hardening, but perfectly workable with the right tooling, parameters and setup
l:
Use rigid fixturing and minimise vibration.
Where possible, remove material symmetrically from both sides of plates/rings to reduce distortion.
Avoid overheating during heavy cuts or grinding to prevent local tempering or residual tensile stresses.
Summary
2205 duplex stainless steel has moderate but manageable machinability: it machines well in the solution-annealed condition when you use rigid setups, duplex-appropriate carbide tooling, moderate speeds with adequate feed, plenty of coolant and effective chip breaking, followed by light finishing cuts or grinding to deliver accurate dimensions and high-quality surfaces on high-strength, corrosion-resistant components.
Corrosion Resistance
Corrosion Resistance of 2205 Stainless Steel
2205 duplex stainless steel (UNS S32205 / S31803, EN 1.4462) offers much better corrosion resistance than 304/316, especially in chlorides, thanks to its high Cr + Mo + N content and duplex (ferrite + austenite) microstructure.
1. General Corrosion Behaviour
Very good resistance to uniform / general corrosion in many industrial, marine and process environments.
Clearly superior to 304L and generally better than 316L in most chloride-bearing waters.
Widely used where 316L is at the limit for pitting, crevice attack or stress-corrosion cracking.
2. Pitting and Crevice Corrosion in Chloride Media
High chromium, molybdenum and nitrogen give 2205 a high pitting resistance (PREN) compared with 304/316.
Excellent resistance to pitting and crevice corrosion in:
Seawater and brackish water
Chloride-containing cooling and process waters
Many chloride-bearing chemical streams
Still needs good design: avoid tight crevices, stagnant pockets and deposits, which can become attack sites for any stainless steel.
3. Chloride Stress-Corrosion Cracking (SCC)
A major advantage of 2205 is its very high resistance to chloride SCC compared with austenitic 304/316.
In warm chlorinated waters, seawater and hot process waters where 304/316 can crack under stress, 2205 typically remains sound within its normal temperature/stress limits.
This SCC resistance is one of the key reasons 2205 is widely used in:
Desalination plants
Cooling-water and heat-exchanger systems
Offshore and marine piping and structures
4. Behaviour in Chemical and Process Environments
Good resistance to many acids, alkalis and salt solutions at moderate concentrations and temperatures.
Performs well in:
Pulp and paper liquors (white, green, black liquors)
Many refinery and petrochemical environments
CO₂ / chloride-containing oil & gas service (within the grade’s limits)
For very strong acids, highly reducing media or extremely aggressive brines, more highly alloyed stainless steels or nickel alloys may still be required.
5. Welds, Heat-Affected Zones and Intermetallic Phases
With proper duplex welding procedures (controlled heat input, suitable filler, correct interpass temperature), welds can have corrosion resistance close to the base metal.
Poor welding practice can:
Produce ferrite-rich welds with lower toughness and pitting resistance.
Form sigma or other intermetallic phases in welds/HAZ if overheated or held too long at intermediate temperatures.
These phases drastically reduce both impact toughness and localized corrosion resistance, so duplex-specific WPS/PQR and good quality control are essential.
6. Surface Finish, Cleaning and Design Effects
As with all stainless steels, corrosion performance is strongly influenced by surface condition:
Smooth, ground or brushed surfaces resist pitting and fouling better than rough, damaged or heavily heat-tinted surfaces.
Weld scale, heat tint, slag, spatter and iron contamination must be removed by pickling or mechanical cleaning + passivation.
Good design further improves resistance:
Avoid crevices, lap joints and dirt traps.
Ensure good drainage and ease of cleaning.
Use compatible fasteners to minimise galvanic effects in wet service.
Summary
2205 duplex stainless steel provides excellent corrosion resistance in chloride-containing and industrial environments, with far better pitting/crevice resistance and much higher chloride SCC resistance than 304/316, provided it is correctly welded, properly cleaned and sensibly designed; this makes it a first-choice material for demanding seawater, brackish-water, pulp & paper, chemical, oil & gas and marine-structural applications.
Heat Treatment
Heat Treatment of 2205 Stainless Steel
2205 duplex stainless steel (UNS S32205 / S31803, EN 1.4462) cannot be hardened by quenching like martensitic steels. Heat treatment is mainly used to obtain or restore the correct duplex microstructure, toughness and corrosion resistance, especially after heavy forming or hot working.
1. General Heat-Treatment Behaviour
Microstructure in the proper condition is roughly 50% ferrite / 50% austenite.
Strength comes from composition + duplex structure + any cold work, not from martensitic hardening or precipitation hardening.
The key treatment in practice is:
Solution annealing with rapid cooling.
Long holds in intermediate temperature ranges can form embrittling intermetallic phases (e.g. sigma) and must be avoided.
2. Solution Annealing (Softening / Resetting the Structure)
Purpose
Restore a balanced duplex microstructure after hot working or heavy cold work.
Dissolve harmful precipitates and recover toughness and corrosion resistance.
Typical practice (exact values depend on mill spec)
Heat into the solution-annealing range (≈ 1020–1100°C).
Hold long enough for full through-heating of the section.
Rapidly cool (usually water quench, or very fast air for thin sections).
Result
Fine, balanced ferrite–austenite structure.
High yield strength for a stainless steel, with good toughness.
Maximum available pitting, crevice and SCC resistance for 2205.
3. Stress Relief and Post-Weld Heat Treatment
Duplex steels, including 2205, normally do not require PWHT after welding if correct welding procedures are used.
Conventional low-temperature “tempering” treatments (like for carbon steels) are not suitable; dwelling duplex steels in the wrong mid-temperature ranges can:
Promote 475°C embrittlement
Encourage sigma / intermetallic phase formation
Reduce toughness and localized corrosion resistance
If a code insists on some stress relief:
It must be at a carefully controlled low temperature and short time, and
Follow specific duplex guidance from the steelmaker or standard.
For most pressure, piping and structural applications in 2205, the preferred route is:
Fabricate (form + weld) in the solution-annealed condition,
Use duplex-correct welding procedures,
Rely on thorough cleaning / pickling / passivation, not PWHT, to achieve final performance.
4. Effect of Heat Treatment on Microstructure and Properties
Correct solution annealing + rapid cooling gives:
Fine, balanced duplex structure
Good toughness (including transverse)
High and consistent yield strength
Excellent pitting/crevice resistance and SCC resistance for this grade
Incorrect heat treatment (overheating, slow cooling, repeated mid-temperature exposure) can:
Produce coarse grains
Form sigma or other intermetallic phases
Severely reduce impact toughness and localized corrosion resistance
2205 does not gain further strength from additional quench or temper steps; repeated uncontrolled heat cycles will generally damage properties rather than improve them.
5. Practical Heat-Treatment Guidelines for Fabricators
Treat 2205 as a duplex stainless, not as carbon steel or martensitic stainless:
No quench-hardening or high-temperature tempering cycles.
Avoid long holds in the 300–1000°C region unless following a qualified duplex procedure.
Typical route:
Mill supply in solution-annealed condition.
Form, machine and weld using duplex-specific procedures.
Apply solution anneal + rapid cooling only when:
Heavy hot work or very severe cold work has been done, and
Top-level toughness and corrosion resistance are required.
Always finish with proper pickling / mechanical cleaning + passivation to remove heat tint and contamination and restore a clean passive surface.
Summary
Heat treatment of 2205 stainless steel is centred on solution annealing at high temperature followed by rapid cooling to restore a fine, balanced duplex microstructure, toughness and corrosion resistance after heavy hot or cold work; routine welded and formed fabrications are normally used in the as-welded, solution-annealed condition with no PWHT, provided duplex-appropriate welding and thorough post-weld cleaning are correctly applied.
Cold Working
Heat Treatment of 2205 Stainless Steel
2205 duplex stainless steel (UNS S32205 / S31803, 1.4462) is a duplex (ferrite + austenite) alloy that is not hardened by quenching like martensitic steels. Heat treatment is mainly used to obtain the correct duplex microstructure, restore toughness and corrosion resistance after hot/heavy cold work, and avoid harmful intermetallic phases.
1. General Heat-Treatment Behaviour
Strength comes from composition + duplex structure + any cold work, not from martensite formation.
Main practical treatments are:
Solution annealing (the key treatment)
Very limited, carefully controlled stress relief (usually avoided unless required by a code).
Prolonged exposure in certain temperature ranges can form sigma and other intermetallic phases, which must be avoided.
2. Solution Annealing (Softening / Microstructure Reset)
Purpose:
Restore a balanced ferrite–austenite microstructure after heavy hot or cold work.
Dissolve any unwanted precipitates and recover toughness + corrosion resistance.
Typical practice (exact values follow mill/spec):
Heat to a solution-annealing range around ≈ 1020–1100°C.
Hold long enough for full through-heating of the section.
Rapidly cool, usually water quench (or very fast air for thin products).
Correct solution annealing + rapid cooling gives:
Fine, balanced duplex structure.
High yield strength with good toughness.
Maximum pitting, crevice and SCC resistance for 2205.
3. Stress Relief and PWHT
Conventional low-temperature stress-relief cycles used for carbon steels are not suitable for 2205 if they involve long holds in the mid-temperature range.
Duplex steels can suffer:
475°C embrittlement and
Formation of intermetallic phases
if exposed too long to intermediate temperatures.
In most pressure/structural applications:
2205 is used without post-weld heat treatment (no PWHT).
Residual stresses are managed by good welding sequence and design, not by high-temperature PWHT.
If a code or customer demands stress relief, it must follow duplex-specific guidance from the steelmaker or standard.
4. Effect of Heat Treatment on Properties
Correct solution annealing + rapid cooling:
Restores toughness and uniform duplex structure.
Ensures high localized-corrosion resistance (pitting/crevice/SCC).
Overheating, long soaking or slow cooling in the 600–1,000°C range can:
Form sigma phase and other intermetallics.
Sharply reduce impact toughness and pitting resistance.
Multiple uncontrolled heat cycles will not increase strength and may damage properties; 2205 does not respond to “quench hardening” like martensitic steels.
5. Practical Route in Fabrication
Typical production route for critical components:
Mill supply in solution-annealed condition.
Forming / machining / welding using duplex-appropriate procedures.
Solution anneal only if:
Very heavy hot work or cold work has been done, or
Code or service conditions demand full restoration of top-level toughness and corrosion resistance.
Finish with proper pickling / mechanical cleaning + passivation to restore a clean passive surface.
Summary
Heat treatment of 2205 stainless steel is built around solution annealing at high temperature followed by rapid cooling to obtain a fine, balanced duplex microstructure with high toughness and excellent corrosion resistance; routine stress relief or quench-hardening cycles are not used, and prolonged exposure in intermetallic-forming temperature ranges must be avoided to prevent embrittlement and loss of corrosion performance.
Cold Working of 2205 Stainless Steel
2205 duplex stainless steel has higher strength and lower ductility than 304/316, but still offers good cold formability for sensible bend radii and moderate forming operations when correct tooling and procedures are used.
1. General Cold Workability
Yield strength ≈ 2× 304/316, so forming loads are significantly higher.
Ductility is lower than austenitic grades, but adequate for:
Rolling and bending of plate and sheet
Forming channels, profiles, tanks, shells
Moderate flanging and edge forming
Not ideal for very severe deep drawing or tight-radius bending on thick sections without special precautions.
2. Bending, Rolling and Forming Practice
Use larger minimum bend radii than for 304/316 to avoid edge cracking.
Form in gradual steps rather than one severe hit, especially on thicker plate.
Use:
Smooth, well-finished tooling
Good lubrication to reduce friction and galling
Proper alignment and support to avoid local over-strain
Expect more spring-back than with austenitic steels and compensate in tooling and angles.
3. Work Hardening and Residual Stresses
2205 work hardens during deformation, though generally less aggressively than 304/316.
Heavy local cold work leads to:
Higher local strength and hardness
Reduced ductility and toughness in those zones
Significant residual stresses, influencing:
Distortion during/after welding
Fatigue and corrosion-fatigue behaviour
For critical components, avoid very high local strains in highly stressed or corrosive regions unless you plan corrective heat treatment.
4. Heavy Cold Work and Optional Solution Annealing
For normal forming (typical bends, rolling, shaping of tanks and piping):
Final solution annealing is often not required, provided forming strains are moderate and welding is done correctly.
For severe cold work, e.g.:
Very tight-radius bends on thick plate
Large-area high-strain stretching or deep drawing
Heavy cold reductions in thickness or diameter
a solution anneal + rapid cooling is advisable to:Restore full toughness
Rebalance the ferrite–austenite structure
Recover the best pitting / crevice / SCC resistance.
5. Interaction with Welding and Machining
Cold-worked zones:
Can distort more when welded because of residual stress.
May respond slightly differently in the HAZ than lightly worked base metal.
Practical sequence for high-accuracy parts:
Form → Weld (with duplex procedures) → Light straighten if needed → Finish machine / grind.
This route balances formability, weldability and final dimensional accuracy.
6. Design Recommendations for Cold-Worked 2205 Components
Assume high forming forces and ensure presses/rolls are sized accordingly.
Avoid:
Sharp corners and very tight radii in highly loaded or chloride-exposed areas.
Severe local thinning (necking) in critical regions.
For demanding structural, pressure or seawater service:
Keep cold strain moderate and well distributed.
Consider solution annealing after extreme forming if top-level toughness and corrosion resistance are required.
Summary
2205 duplex stainless steel can be cold worked successfully when treated as a high-strength duplex alloy: use larger bend radii, higher forming loads, good lubrication and gradual forming, keep cold strains moderate for most applications, and apply solution annealing after very heavy cold work if maximum toughness and corrosion resistance are needed for critical service in aggressive or highly stressed environments.
