DUPLEX SS 32205
Full of a combination of strong properties like austenitic and ferritic grains which can be achieved with cold work, duplex stainless steel alloys are a great option for steel working. Developed in 1996, UNS S31803 has gone through many changes which led to the endorsement of the S32205.
The UNS S32205 offers more choices choice, making it a popular handy option. The difference between UNS S31803 and S32205s is that S32205 has larger amounts of nitrogen content, which gives it better corrosion resistance. The other alternative for SAF 2205 is a popular 904L Stainless Steel.
S31803 S32205 chemical composition
| GRADE | Ni | Cr | Mo | C | Mn | Si | P | S | N | |
|---|---|---|---|---|---|---|---|---|---|---|
| S31803 | MIN | 4.5 | 21 | 2.5 | – | – | – | – | – | 0.08 |
| MAX | 6.5 | 23 | 3.5 | 0.03 | 2 | 1 | 0.03 | 0.02 | 0.2 | |
| S32205 | MIN | 4.5 | 22 | 3 | – | – | – | – | – | 0.14 |
| MAX | 6.5 | 23 | 3.5 | 0.03 | 2 | 1 | 0.03 | 0.02 | 0.2 |
Corrosion Resistance of Duplex stainless steel
The microstructure of the duplex stainless steel 2205 has fairly higher amounts of the elements like chromium, molybdenum, and nickel. These elements greatly improve pitting, and when in contact with the chloride it can resist crevice corrosion. This strength is twice of austenitic stainless steel, hence it is useful in multiple applications, storage tanks, and many more.
Physical properties
| Grade | Density (g/cm3) | Elastic Modulus (GPa) | Mean Co-eff of Thermal Expansion (μm/m/°C) | Thermal Conductivity (W/m.K) | Specific Heat (J/Kg.K) | Electrical Resistivity (μΩ.m) | |||
|---|---|---|---|---|---|---|---|---|---|
| Duplex 2205/31803 | 7.82 | 190 | 0-100°C | 0-315°C | 0-538°C | at 100°C | at 500°C | 0-100°C | 850 |
| 13.7 | 14.2 | – | 20 | – | 418 | ||||
When properly treated with heat, UNS S31803 has fair amounts of austenite and ferrite. This microstructure of the duplex stainless steel2205makes it more resistant to stress corrosion cracking, as compared to stainless steel 304 and 316L. Particularly, they are twice as strong as austenitic or ferritic stainless steels, with better toughness and ductility.
SPECIFICATION
| GRADE | UNS | OLD BRITISH | EURONORM | SWEDISH SS | JAPANESE JJ | ASTM | ||
|---|---|---|---|---|---|---|---|---|
| Duplex 2205/31803 | S32205/S31803 | BS | EN | NO | NAME | 2377 | SUS 329J3L | A240, A276, A182, A815, A789, A790 |
| 318S13 | – | 1.4462 | X2CrNiMoN 22.5.3 | |||||
The engineering performance of duplex stainless steel has gifted it with multiple applications, mainly in a corrosive environment. Such examples are gas pipelines and chemical reaction vessels, or manufacturing of a seawater heat exchanger and chemical container to be used in high-concentration chloride conditions; the usages are versatile.
Heat Resistance of Duplex stainless steel
Alloy duplex stainless steel 2205is equipped with good high-temperature oxidation resistance, but, this grade (just like any otherduplex stainless steel) is not resistant to embrittlement if held for more than 300°C. When done so, the brittle micro constituent of UNS S31803 undergoes precipitation. With temperatures below -50°C, a transition may occur, one where the micro constituent experience a shift from ductile-to-brittle.
Hot Forming of Duplex Stainless Steel
Duplex stainless steel 2205 shows better hot formability with considerably low forming loads up to a minimum of 1230°C (2250°F). But, in hot forming at too low temperatures, it may deform in the weaker but less ductile ferrite, where it may crack of the ferrite in the deformed region.
In duplex Stainless steel, the typical hot forming temperature can be between 1100°C (2000°F) and 1150°C (2100°F).
Heat treatment of Duplex stainless steel
Post hot forming, it is important to perform a full solution anneal with a rapid quench to completely restore the mechanical properties and improve its corrosion resistance. There is no effect of heat treatment on the hardening of the duplex stainless steel. But in some cases, they can be work-hardened.Solution treatment as an option or annealing can be performed by rapid cooling after heating toa temperature of around 1100°C.
Weldability of Duplex stainless steel
While the duplex stainless steelis being welded, the microstructure and the characteristics of welding material are controlled at some levels by altering the filler material composition. However, the microstructure and the heat-affected zone (HAZ) are characterized only by thermal cycles. This is extra-ordinarily sensitive to welding conditions.
Duplex stainless steelis good weldability. All the popular welding processes can be applied while welding. They cannot be welded goodas the austenitic grades but low thermal expansion in duplex stainless steel grades reduces distortion and post welding residual stresses. The recommended filler material for duplex stainless steel 2205 is 2209.
Applications of duplex stainless steel
- Pressure vessels, tanks, piping,and heat exchanger in the chemical processing industry
- Piping, tubing, and heat exchangers used in handling of gas and oil
- Effluent scrubbing system
- Pulp and paper industry digesters, bleaching equipment, and stock-handling system
- Rotors, fan, shafts, and press rolls requiring combined strength and corrosion resistance
- Cargo tanks for ship and trucks
- Food processing equipment
- Biofuels plants
