S31803 and S32205 are both types of duplex stainless steel, featuring very similar chemical compositions and mechanical properties. They are often considered interchangeable, but there are some subtle differences between them.
S31803 VS S32205 Key Differences
S32205 contains higher levels of Cr, Mo, and N, making it superior in pitting resistance (PREN value) and mechanical stability. Although their standard composition ranges overlap, S32205 tends to stay near the upper limits to ensure consistent performance.
| Aspect | S31803 | S32205 |
| Standard | Earlier duplex stainless steel standard | Optimized, later versions widely replacing S31803 |
| Nitrogen Content | Typically 0.14–0.20% | Slightly higher, typically 0.14–0.22%, near upper limit |
| Corrosion Resistance | Good | Better, especially in pitting and crevice corrosion |
| Strength & Toughness | Meets duplex standards | More consistent performance under stricter strength criteria |
| Usage Status | Gradually replaced by S32205 in supply chains | More common and recommended in modern industrial applications |
S31803 VS S32205 PREN (Pitting Resistance Equivalent Number) Comparison
PREN is used to evaluate a stainless steel’s resistance to pitting corrosion in chloride-containing environments.
PREN = %Cr + 3.3 × %Mo + 16 × %N
| Item | S31803 | S32205 | Note |
| PREN Range | Typically 32–35 | Typically 34–38 | Higher Mo and N in S32205 = Better pitting resistance |
A PREN ≥ 32 is generally suitable for chloride-rich environments like seawater and chemical plants.
Chemical Composition Comparison (Typical, % by weight)
| Element | S31803 | S32205 | Notes |
| C (Carbon) | ≤ 0.030 | ≤ 0.030 | Same; controls hot cracking during welding |
| Mn (Manganese) | ≤ 2.00 | ≤ 2.00 | Same; affects hot workability |
| P (Phosphorus) | ≤ 0.030 | ≤ 0.030 | Same; reduces brittleness |
| S (Sulfur) | ≤ 0.020 | ≤ 0.020 | Same; improves machinability |
| Si (Silicon) | ≤ 1.00 | ≤ 1.00 | Same; used as a deoxidizer |
| Cr (Chromium) | 21.0–23.0 | 22.0–23.0 | Higher in S32205 for better corrosion resistance |
| Ni (Nickel) | 4.5–6.5 | 4.5–6.5 | Same; stabilizes austenite phase |
| Mo (Molybdenum) | 2.5–3.5 | 3.0–3.5 | Higher in S32205 for better pitting resistance |
| N (Nitrogen) | 0.08–0.20 | 0.14–0.20 (near upper limit) | Higher in S32205 for better strength and corrosion resistance |
| Fe (Iron) | Balance | Balance | Base material |
Mechanical Properties (per ASTM A240 / ASME SA240 standards)
While mechanical properties are similar, S32205 typically performs more reliably in production, especially in welded zones and heat-affected areas, due to improved compositional consistency.
| Property | S31803 | S32205 | Unit |
| Tensile Strength | ≥ 620 | ≥ 620 | MPa |
| Yield Strength (0.2%) | ≥ 450 | ≥ 450 | MPa |
| Elongation | ≥ 25 | ≥ 25 | % |
| Brinell Hardness (HBW) | ≤ 290 | ≤ 290 | — |
Conclusion
S32205 is an improved version of S31803, offering better nitrogen control and more consistent performance.
They are interchangeable in many standards, but S32205 is preferred for demanding applications such as marine, chemical processing, or chloride exposure.
If design allows, S32205 can directly replace S31803 without significant cost difference.
S32205 is now the more widely available and used material in global supply.
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