Introduction
2205 is a duplex (austenitic-ferritic) stainless steel composed of approximately 22% chromium, 2.5% molybdenum, and 4.5% nickel-nitrogen. It is one of the most widely used duplex stainless steel grades, governed primarily by ASTM A240/A240M (UNS S32205).
The defining advantage of 2205 over conventional austenitic grades such as SUS304, SUS316, and 317L is its yield strength more than twice as high, combined with superior resistance to pitting, crevice corrosion, and stress corrosion cracking (SCC). This allows designers to reduce wall thickness and component weight while maintaining structural integrity — delivering a significant cost advantage in pressure vessels, pipelines, and structural applications.
2205 is suitable for service in the temperature range of −50°F to +600°F (−46°C to +316°C). In strictly controlled conditions (particularly for welded structures), it may also be used at lower temperatures.
Content authorized for publication by FULLERKREG.
Chemical Composition
Reference standard: ASTM A240/A240M
| Element | C (%) | Si (%) | Mn (%) | P (%) | S (%) | Cr (%) | Ni (%) | Mo (%) | N (%) |
|---|---|---|---|---|---|---|---|---|---|
| 2205 (S32205) | ≤ 0.03 | ≤ 1.00 | ≤ 2.00 | ≤ 0.03 | ≤ 0.02 | 22.0–23.0 | 4.5–6.5 | 3.0–3.5 | 0.14–0.20 |
Mechanical Properties
Reference standard: ASTM A240/A240M
| UNS | Grade | Tensile Strength Min (MPa) | Yield Strength Min (MPa) | Elongation (2 in., %) | Hardness Max (HB) | Hardness Max (HRB) |
|---|---|---|---|---|---|---|
| S32205 | 2205 | 655 | 450 | 25 | 293 | 31 |
Key comparison: The yield strength of 2205 (450 MPa min) is more than double that of SUS316L (175 MPa min) and SUS304 (205 MPa min), enabling significant weight and cost savings in structural designs.
Global Grade Equivalents
| Standard / Region | Designation |
|---|---|
| ASTM (USA) | 2205 / S32205 (UNS) / S22053 (ISC) |
| GB (China) | 022Cr22Ni5Mo3N / 022Cr23Ni5Mo3N (GB/T 39033) |
| JIS (Japan) | SUS329J3L |
| EN / DIN (Europe) | X2CrNiMoN 22-5-3 / 1.4462 |
| ISO | X2CrNiMoN 22-5-3 (ISO 15510) |
| NF EN (France) | X2CrNiMoN 22-5-3 |
Microstructure
2205 achieves its optimal microstructure of approximately 50% austenite (γ) / 50% ferrite (α) after solution annealing at 1040–1080°C (1900–1922°F) followed by rapid water quenching.
Important microstructural considerations:
- Annealing above 1093°C (2000°F) may increase the ferrite fraction.
- Like all duplex stainless steels, 2205 is susceptible to intermetallic phase precipitation between 704°C and 982°C (1300°F–1800°F), with the fastest precipitation rate at approximately 871°C (1600°F).
- Components should be tested for intermetallic phases per ASTM A923 when required.
Applications
2205's combination of high strength, excellent corrosion resistance, and good weldability makes it the preferred material in demanding environments:
- Oil & Gas — pipelines, heat exchanger tubing, subsea components
- Chemical Processing — pressure vessels, high-pressure storage tanks, reactors, heat exchangers
- Pulp & Paper — digesters, bleaching equipment, classifiers, storage and handling systems
- Water & Wastewater Treatment — sewage treatment systems, desalination equipment
- Marine & Cargo — ship and truck cargo containers, offshore structural components
- Rotating Equipment — shafts, press rolls, impellers, and blades in corrosive, high-load environments
- Food Processing — processing equipment requiring both hygiene and structural strength
- Fasteners — high-strength bolts and nuts for corrosive structural applications
Browse our marine-grade stainless steel fasteners: Marine Carriage Bolts (DIN 603), Marine Eye Bolts (DIN 444), and Marine Nylon Locking Nuts (DIN 982).
Fabrication Characteristics
Hot Forming
Hot forming should be performed in the temperature range of 954–1232°C (1750–2250°F), where 2205 is very soft and workable. Key guidelines:
- The entire workpiece must be uniformly heated.
- Temperatures above the upper limit risk hot tearing; temperatures below the lower limit risk austenite fracture.
- Below 927°C (1700°F), intermetallic phases form rapidly due to combined temperature and deformation effects.
- Immediately after hot forming, solution anneal at a minimum of 1038°C (1900°F) and water quench to restore phase balance, toughness, and corrosion resistance.
- Cold forming below 316°C (600°F) is recommended where possible.
Cold Forming
2205 can be cut and cold-formed. Due to its high strength and hardness compared to austenitic steels, greater forming forces are required and springback must be accounted for in tooling design.
Heat Treatment
Anneal at a minimum of 1038°C (1900°F) followed by rapid water quenching. This applies to both solution annealing and stress relief. Stress relief below 1038°C risks precipitation of harmful metallic or non-metallic phases and is not recommended.
Machinability
On high-speed machine tools, 2205 has similar feed rates and cutting speeds to 316L. When using carbide tooling, cutting speeds are approximately 20% lower than 316L. Machine rigidity and tooling quality are critical factors.
Weldability
2205 has good weldability. The welding procedure must be designed to maintain proper phase balance in the weld metal and heat-affected zone (HAZ), and to avoid precipitation of harmful intermetallic or non-metallic phases. Weld metal and HAZ should match the base metal in corrosion resistance, strength, and toughness. No post-weld heat treatment is required if proper procedures are followed.
Standards reference: ASTM A240/A240M | ASTM A959 | GB/T 39033 | JIS G4303 (SUS329J3L) | EN 10088 (1.4462) | ISO 15510
Content authorized for publication by FULLERKREG.