Difference between Duplex stainless steel 2205 and UNS S31803
When we talk about the Duplex Stainless Steel, Duplex 2205 and UNS S31803 are the most popular options in industries requiring excellent corrosion resistance and high strength. While the two grades are quite simliar, there are distinct differences worth understanding.
What is Duplex Stainless Steel 2205?
Duplex 2205 ,known as UNS S32205, is a versatile duplex stainless steel alloy that offers exceptional resistance to corrosion, particularly in chloride-rich environments. It boasts a balanced microstructure of austenite and ferrite, providing a unique combination of high strength and toughness. With a typical composition of 22% chromium, 5-6% nickel, and 3% molybdenum.
generally,for easy understanding,figure 22 is referring to 22%chromium,and 05 is referring to 5% nickel content.
2205 is engineered to handle demanding applications in industries like oil and gas, chemical processing, and marine environments.
What is UNS S31803?
UNS S31803 is a designation under the Unified Numbering System (UNS) for a similar duplex stainless steel. It shares much of its chemical composition and properties with Duplex 2205. However, UNS S31803 was originally developed as a lower-tolerance duplex grade before being refined into modern standards like 2205.
Chemical Composition Comparison (in % by weight)
| Element | Duplex 2205 | UNS S31803 | Purpose |
|---|---|---|---|
| Chromium (Cr) | 22.0 – 23.0 | 21.0 – 23.0 | Provides corrosion resistance, particularly against pitting and crevice corrosion. |
| Nickel (Ni) | 4.5 – 6.5 | 4.5 – 6.5 | Stabilizes the austenitic phase, improving toughness and ductility. |
| Molybdenum (Mo) | 3.0 – 3.5 | 2.5 – 3.5 | Enhances resistance to localized corrosion in chloride-rich environments. |
| Nitrogen (N) | 0.14 – 0.20 | 0.08 – 0.20 | Improves pitting resistance, yield strength, and toughness. |
| Manganese (Mn) | ≤ 2.0 | ≤ 2.0 | Aids in deoxidization during manufacturing and improves toughness. |
| Silicon (Si) | ≤ 1.0 | ≤ 1.0 | Enhances oxidation resistance and improves strength at elevated temperatures. |
| Carbon (C) | ≤ 0.03 | ≤ 0.03 | Low carbon minimizes carbide precipitation during welding and reduces intergranular corrosion. |
| Phosphorus (P) | ≤ 0.03 | ≤ 0.03 | Controlled to avoid brittleness and ensure toughness. |
| Sulfur (S) | ≤ 0.02 | ≤ 0.02 | Kept low to enhance weldability and avoid hot cracking. |
- Duplex 2205 has a tighter range (0.14 – 0.20%) for nitrogen compared to UNS S31803 (0.08 – 0.20%).
- Higher nitrogen content in 2205 improves pitting resistance and overall strength.
- Duplex 2205 has 22.0 – 23.0%Chromium and 3-3.5%Molybdenum (Mo) which is slightly higher than UNS S31803
Duplex stainless steels dominate the consumption landscape, constituting over 80% of duplex, super duplex, and hyper duplex grades. Renowned for their unparalleled anti-corrosion capacity and exceptional heat and energy absorption capabilities, they stand out in applications where materials with fewer attributes would succumb to pressure. In particular, S32205 is integral in tasks such as chemical treatment, material handling and processing projects, and paper production.
The duplex grade family, including S32205, boasts twice the strength and a substantial enhancement in corrosion resistance. The resistance to pitting corrosion can be further improved by increasing the chromium content. The development of the difference between S31803 and S32205 can be traced back to the Pitting Resistance Equivalent Number (PREN), which assesses an alloy’s pitting resistance by considering various elements in its formula.
