S31803 plate is a duplex stainless steel grade defined under UNS S31803, corresponding to EN 1.4462 and commonly known as Duplex 2205. It features a balanced austenitic-ferritic microstructure (approximately 50% austenite / 50% ferrite), delivering approximately twice the yield strength of standard austenitic grades like 304L or 316L, combined with excellent resistance to chloride stress corrosion cracking (SCC), pitting, and crevice corrosion.

S31803 is one of the original duplex stainless steel specifications and remains widely used in chemical processing, oil & gas, marine, and desalination applications where both high strength and superior corrosion resistance are required.

Key Features

Equivalent Designations

Note: UNS S32205 is a newer specification with tighter composition ranges. S31803 remains acceptable for many applications but may have slightly broader allowable ranges for chromium (21.0-23.0% vs 22.0-23.0%) and molybdenum (2.5-3.5% vs 3.0-3.5%).

Specifications & Size Range

Surface Finishes

S31803 vs. S32205 Comparison

S32205 offers tighter composition control and more consistent properties. However, S31803 remains widely accepted and readily available in the market.

Corrosion Resistance Highlights

Processing Guidelines

Hot Working

Temperature range: 1750 – 2050°F (950 – 1120°C), followed by rapid cooling (water quenching). Avoid working below 1700°F (925°C).

Cold Working

Requires approximately 30-50% higher forming force compared to 316L. Intermediate annealing may be required for severe deformation.

Heat Treatment

• Solution Annealing: 1870 – 2010°F (1020 – 1100°C)

• Cooling: Water quench or rapid air cool

• Hardening: Not hardenable by heat treatment; only through cold working

Welding

• Suitable with standard methods (SMAW, GTAW, GMAW, SAW, FCAW)

• Recommended filler metal: 2209 (E2209 or ER2209)

• Control heat input (0.5 – 2.5 kJ/mm) to maintain phase balance

• Preheat is generally not required

• Post-weld heat treatment is not typically needed

• Avoid overheating to prevent intermetallic phase precipitation

Machining

Requires rigid tooling and lower cutting speeds due to higher strength and work hardening tendency.

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