S31803 Stainless Steel
Stainless Steel S31803 is a widely recognized duplex stainless steel grade that combines the benefits of austenitic and ferritic stainless steels, offering an exceptional balance of high strength, superior corrosion resistance, and good weldability. This duplex alloy is part of the 2205 series, characterized by its approximately 50/50 austenitic-ferritic microstructure, which delivers enhanced performance in aggressive environments compared to many standard austenitic grades.
Chemical Composition
|
C |
Si |
Mn |
P |
S |
Cr |
Ni |
Mo |
N |
|
|
Min |
- |
- |
- |
- |
- |
21 |
4.5 |
2.5 |
0.08 |
|
Max |
0.03 |
1 |
2 |
0.03 |
0.02 |
23 |
6.5 |
3.5 |
0.2 |
Material Properties
|
Density |
Melting Point |
Minimum Mechanical Properties at Room Temperature |
||
|
Tensile Strength |
Yield Strength |
Elongation |
||
|
g/cm3 |
℃ |
Rm N/mm2 |
Rp0.2 N/mm2 |
A5% |
|
7.82 |
1420~1470 |
620 |
450 |
25% |
Feature
S31803, a dual-phase stainless steel, owes its structure and properties to a precisely designed chemical composition. Chromium (21-23%) forms a protective oxide layer for corrosion resistance, nickel (4.5-6.5%) stabilizes the austenitic phase, and molybdenum (2.5-3.5%) enhances resistance to pitting and crevice corrosion, especially in chloride-rich conditions. Nitrogen (0.08-0.20%) strengthens the austenitic phase, while carbon, manganese, silicon, phosphorus, and sulfur are controlled to maintain microstructural balance.
Mechanically, S31803 excels with a minimum tensile strength of 620 MPa and yield strength of 450 MPa, nearly double that of 304 or 316, yet retains 25% elongation for fabrication. Its high strength-to-weight ratio suits weight-sensitive applications.
Corrosion resistance is S31803's forte. With a PREN of 32-36, it resists general, pitting, and crevice corrosion in seawater, brines, and industrial chemicals better than 316.
Applications
Marine Engineering: Seawater desalination equipment, marine pumps/valves, offshore platform structures
Petrochemical Equipment: Oil refinery pipelines, storage tanks, heat exchangers (resistant to H₂S/CO₂ corrosion)
Environmental Protection: Wastewater treatment systems, flue gas desulfurization units
Chemical Industry: High-chloride ion medium containers (e.g., bleaching equipment)
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