2205 Duplex Stainless Steel Plate

Most 2205 Duplex Stainless Steel Plate data sheets tell you the same six things: chromium 22–23%, molybdenum 3%, yield 450 MPa, density 7.8 g/cm³, ASTM A240. That's the spec sheet. What it does not tell you is why a 14 mm 2205 plate costs less in a pressure vessel than a 20 mm 316L plate, why your fabricator cannot use the same welding procedure as 316L, and why "ASME BPVC Section VIII allowable stress" is a different number from "ASME B31.3 allowable stress" even though both say 2205.

What the Spec Sheet Says vs What It Means

ASTM A240 / ASME SA-240 covers chromium and chromium-nickel stainless steel plate for pressure vessels and general applications. For UNS S32205 (2205), the spec sheet numbers are:

Element / Property	ASTM A240 Limit (UNS S32205)	Typical Mill Heat	What the Difference Means
Chromium	22.0 – 23.0%	22.5%	Above 22% - the threshold for chloride SCC resistance
Nickel	4.5 – 6.5%	5.5%	Balances ferrite phase; too low = brittle
Molybdenum	3.0 – 3.5%	3.2%	Pitting resistance in chlorides
Nitrogen	0.14 – 0.20%	0.17%	Boosts PREN; stabilizes austenite
Carbon	≤ 0.030%	0.020%	Low carbon to prevent sensitization
PREN (calculated)	≥ 35	~36.7	Threshold for "duplex" performance
Yield strength, min	450 MPa (65 ksi)	460–480 MPa	~2.6× the yield of 316L (170 MPa)
Tensile strength, min	620 MPa (90 ksi)	650–700 MPa	~1.3× the tensile of 316L
Elongation, min	25%	30%	Ductility for forming and rolling
Hardness, max	31 HRC (293 HBW)	28 HRC	For sour service, ≤ 28 HRC per NACE MR0175
Density	7.8 g/cm³ (0.285 lb/in³)	-	Lighter than carbon steel by ~3%
Melting range	1420 – 1465 °C	-	Welding window above 1000 °C

The single most important number for the spec sheet is the 22% chromium floor. Below that, you do not have a duplex stainless - you have a lean duplex with compromised chloride resistance. Several mills produce S31803 (the older 2205 designation with 21% Cr minimum) at a small cost savings; if your spec says "S32205" you get the higher chromium chemistry and the PREN value that goes with it.

 

Why Buy 2205 Plate Instead of 316L Plate

For most buyers, the comparison is not 2205 vs 2507. It is 2205 vs 316L. The answer comes down to two things: weight (and therefore cost) and chloride resistance.

Vessel / Service	Material Comparison	Weight / Cost Implication
Pressure vessel, ambient seawater, 25 °C	14 mm 2205 vs 20 mm 316L	2205 plate weighs 30% less; material cost saves 25–35% even at 1.8× the 316L price
Desalination evaporator shell	12 mm 2205 vs 18 mm 316L	2205 saves 33% on plate weight; reduces skid weight, foundation cost, lifting cost
Offshore topside equipment frame	8 mm 2205 vs 12 mm 316L	2205 saves 33% weight; less coating area, easier installation
Tubesheet (heat exchanger)	2205 plate (vs titanium for seawater)	2205 saves 50%+ vs titanium; ASME BPVC VIII qualified
Storage tank, dilute acid	2205 plate (vs 316L)	2205 lasts 2–3× longer in chloride-bearing acid

 

Thickness, Sizes and Forms Available

We supply 2205 plate to ASTM A240 / ASME SA-240 in the following range. Other thicknesses and cut-to-size available on request.

Form	Thickness Range	Width Range	Length Range	Finish
Hot rolled plate (HRAP)	3.0 – 100 mm	1000 – 2500 mm (up to 3000 mm)	2000 – 12000 mm	No.1 (HR, annealed, pickled)
Cold rolled sheet	0.5 – 6.4 mm	1000 – 1500 mm	2000 – 6000 mm	2B, BA, No.4, mirror
Plasma / laser cut plate	As above	Custom	Custom	As-rolled or pickled
Plate for tubesheet (heavy)	50 – 150 mm	up to 2500 mm	up to 6000 mm	No.1, machined faces

The standard plate thickness range we keep in stock is 6 mm to 50 mm, which covers most pressure vessel and structural applications. Below 6 mm becomes "sheet" territory (cold rolled, 2B finish). Above 50 mm we order to size for the specific project; lead time is typically 6–10 weeks because heavy plate requires special rolling and solution annealing.

 

Standards, Certification and Documentation

For pressure vessel and structural applications, 2205 plate is supplied to the following standards:

Standard	Scope	Typical Use
ASTM A240 / ASME SA-240	Chromium / Cr-Ni stainless steel plate for pressure vessels	Most common; default
ASTM A480 / ASME SA-480	General requirements for flat-rolled stainless	Companion to A240
EN 10028-7	Stainless steel flat products for pressure purposes	European pressure vessel
EN 10088-3	Stainless steels for general purposes	European general
Werkstoff 1.4462	German material number	European designation
NACE MR0175 / ISO 15156-3	Sour service (H2S) compliance	Oil & gas, 28 HRC max
ASTM A923	Detecting detrimental intermetallic phases in duplex	Weld procedure qualification

 

Documentation shipped with every plate order:

Document	Standard	Typical For
Mill Test Certificate (MTC)	EN 10204 3.1 or 3.2	All shipments
Chemistry check (Cr 22–23%, Mo 3.0–3.5%, N 0.14–0.20%)	ASTM A240	All shipments
Mechanical test report (yield, tensile, elongation, hardness)	ASTM A370	All shipments
Solution annealing record (1020–1100 °C + rapid water quench)	Mill process record	All shipments
Ferrite content (35–65% per ASTM E562)	ASTM E562	Duplex welds
Intermetallic phase test	ASTM A923 Method A	Welds for sour service
Charpy impact at –46 °C (≥ 150 J average, 3 specimens)	ASTM A370	Cold-service / subsea
Country of origin / mill location	Customs	GCC and EU imports
PED conformity (for EU pressure equipment)	PED 2014/68/EU	European delivery

For GCC delivery, the documentation list expands to include dual-tagging (heat number on plate AND certificate), AVL registration, and Saudi Arabia SASO conformity. Ask for a document transmittal list at RFQ stage so you know what arrives with the shipment.

 

Where 2205 Plate Is Used

Pressure vessel, structural, and fabrication applications:

Industry	Where 2205 Plate Goes
Oil & gas	Separator vessels, scrubber shells, production manifold bodies, flare stack linings, hydrocarbon storage
Desalination	SWRO high-pressure pump housings, evaporator shells, brine heater shells, intake piping supports
Chemical / petrochemical	Reactor vessels, acid storage tanks, heat exchanger tubesheets and shells
Pulp & paper	Digesters, blow tanks, black liquor heaters
Marine / offshore	Topside equipment frames, firewater pump housings, structural support plates
Power generation	FGD absorber shells (2205 qualified to ~300 °C; above that, upgrade to Inconel 625), cooling water systems
Mining	Slurry pipelines, leaching vessels, thickener shells

The decision rule for upgrading from 2205 plate to 2507 super duplex plate is the same as the pipe decision: chloride concentration above ~5,000 ppm, H2S partial pressure above 0.05 psi, or seawater service temperature above ~50 °C. For 2205 plate at temperatures above 300 °C (continuous service), upgrade to Inconel 625 plate.

 

Welding Notes (Plate vs Pipe)

Plate welds behave differently from pipe welds, and the fabricator's WPS must reflect this.

Difference	Pipe Welding	Plate Welding
Position	All positions (6G qualified)	Mostly flat (1G) and horizontal (2G)
Joint type	Butt weld, branch connection	Butt weld, fillet weld, lap joint, tubesheet-to-shell
Heat input	0.5 – 2.5 kJ/mm (duplex)	Same window - heat input matters just as much
Filler	ER2209 (most common)	ER2209 (same)
PWHT	Never (sigma phase risk)	Never (sigma phase risk)
Ferrite check	Weld + HAZ per ASTM E562	Same - weld + HAZ per ASTM E562
Intermetallic phase test	ASTM A923 Method A (welds)	Same - ASTM A923 Method A

The plate-specific risks to watch for: thick-plate welds (above ~25 mm) may require multiple passes with controlled interpass temperature (≤ 150 °C) because heat builds up in the joint; tubesheet-to-shell welds are deep grooves with high restraint and risk of root cracking if the WPS is not qualified for the actual joint geometry; clad plate (2205 plate with a stainless or nickel alloy cladding layer) requires separate welding procedures for the base 2205 and the cladding layer.

 

What to put in your RFQ: "plate to be welded per ASME Section IX qualified WPS using ER2209 filler, heat input 0.5–2.0 kJ/mm, interpass temperature ≤ 150 °C, ferrite content 35–65% per ASTM E562 in weld and HAZ, ASTM A923 Method A corrosion test on PQR coupon, no PWHT."

 

 

 

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