CD4MCu Duplex Stainless Steel Casting

ASTM A890 / CD4MCu (Grade 1A). CD4MCu is a copper-bearing duplex (austenitic-ferritic) cast stainless with high strength and outstanding chloride and stress-corrosion resistance — for the most aggressive valve and pump service.

Chemical composition (nominal wt %)

Element	%
Carbon (C)	≤0.04
Chromium (Cr)	24.5–26.5
Nickel (Ni)	4.75–6.0
Molybdenum (Mo)	1.75–2.25
Copper (Cu)	2.75–3.25

Mechanical properties

Property	Value
Tensile strength	690 MPa (100 ksi) min
Yield strength	485 MPa (70 ksi) min
Elongation	16% min
PREN	≈ 34–40

Density: 7.8 g/cm³ · Heat treatment: Solution annealed and water quenched to balance the austenite-ferrite phases.

Cross-standard equivalents

Standard	Equivalent grade
EN	EN 1.4517 (GX2CrNiMoCuN25-6-3-3)
GB	—
Similar	≈ 2205 / UNS J93372

Equivalents by nominal class — confirm exact chemistry & spec for critical parts.

Typical applications

Seawater & brine pumps/valves
Desalination & FGD equipment
High-strength corrosion-resistant castings
Chloride stress-corrosion service

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FAQ

Why use duplex CD4MCu instead of CF8M?

CD4MCu's duplex (austenitic-ferritic) structure gives roughly double the yield strength of CF8M and a much higher PREN (~34–40 vs ~24–26), so it resists chloride pitting and stress-corrosion cracking in seawater, brine and other aggressive media far better.