2507 Super Duplex Stainless Steel

┃ Material

S32750, 1.4410, X2CrNiMoN2574, 022Cr25Ni7Mo4N

S32760, 1.4501, X2CrNiMoCuWN2574, 022Cr25Ni7Mo4WCuN

┃ Overview

2507 super duplex stainless steel contains 25% chromium, 4% molybdenum, and 7% nickel are designed for demanding applications which require exceptional strength and corrosion resistance, such as chemical process, petrochemical, and seawater equipment. The steel has excellent resistance to chloride stress corrosion cracking, high thermal conductivity, and a low coefficient of thermal expansion. The high chromium, molybdenum, and nickel levels provide excellent resistance to pitting, crevice, and general corrosion.

2507 SDSS like S32750 and S32760, is a mixed microstructure of austenite and ferrite (50/50) which has improved strength over ferritic and austenitic steel grades. The main difference is that Super Duplex has a higher molybdenum and chromium content which gives the material greater corrosion resistance than standard duplex grades.

┃ Characteristics

◇ Excellent resistance to stress corrosion cracking (SCC) in chloride-bearing environments

◇ Excellent resistance to pitting and crevice corrosion

◇ High resistance to general corrosion

◇ Very high mechanical strength

◇ Physical properties that offer design advantages

◇ High resistance to erosion corrosion and corrosion fatigue

◇ Good weldability

┃ Application

2507 SDSS are widely used in following industries

Oil-gas

Chemical processing

Subsea control line

Heat exchangers

Offshore plateforms

Fire-fighting system

Injection & ballast water systems

Vessels

Desalination plants

Energy industry FGD system, industrial scrubbing system, absorption tower

┃ Chemical composition (wt% as per ASTM A789 / A790)

Material	C	Si	Mn	P	S	Cr
S32750	≤0.03	≤0.80	≤1.20	≤0.030	≤0.020	24.0~26.0
S32760	≤0.03	≤1.0	≤1.0	≤0.030	≤0.020	24.0~26.0
Material	Ni	Mo	N	Cu	W
S32750	6.0~8.0	3.0~5.0	0.24~0.32	≤0.50
S32760	6.0~8.0	3.0~4.0	0.20~0.30	0.50~1.00	0.50~1.00

S32750: PREN ≥ 41, S32760: PREN ≥ 40.

┃ Corrosion resistance

Pitting corrosion resistance

Pitting and crevice corrosion resistance is generally a function of an alloy’s chromium, molybdenum and nitrogen contents. Calculated indexes have been devised to roughly predict and rank alloys for pitting resistance based on these elements (in weight-%). The higher the index the higher the predicted pitting corrosion resistance.

Stress corrosion cracking resistance

To achieve resistance to stress corrosion cracking in stainless steels, the nickel content must either be low as in the ferritic group of steels, or very high making them correctly nickel base alloys. The ferritic stainless steels are nearly immune to SCC, but are difficult to fabricate and are subject to brittle behavior at low temperatures. Nickel, and high nickel alloys also possess excellent SCC resistance but are costly due to their high nickel content. The low nickel austenitic stainless steels (304, 316, 317) have poor SCC resistance compared to ferritic stainless and high nickel alloys.

┃ Mechanical property

Material	Tensile strength ksi (MPa)	Yield strength ksi (MPa)	Elongation in 2” % min.	Hardness HBW /HV max.
S32750	116 (800)	80 (550)	15	300 / 300
S32760	109 (750)	80 (550)	25	310 / 310

┃ Heat treatment

S32750: 1880-2060 (1025-1125), rapid cooling in water or air.

S32760: 1960-2085 (1070-1140), rapid cooling in water or air.

┃ Available Process

(1) Hot formed, solution annealed, descaled

(2) Cold worked and bright annealed

(3) Cold worked, annealed and descaled

(4) Cold worked, polished (MP, EP etc.)

(5) Cold worked, bright annealed, polished (MP, EP etc.)

┃ Common Tests

Chemical composition

Tension

Hardness

Flaring

Flange

Flattening

Micro structure

Hydrostatic

NDT

Intergranular Corrosion

Surface condition

Shape and dimension

Positive Material Identification