SAF™ 2507 Strip steel

Datasheet updated

2022-07-14 12:35
(supersedes all previous editions)

SAF™ 2507 is a super-duplex (austenitic-ferritic) stainless steel for service in highly corrosive conditions. The grade is characterized by:

  • 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

Standards

  • UNS: S32750
  • EN Number: 1.4410
  • EN Name: X 2 CrNiMoN 25-7-4

Chemical composition (nominal)

Chemical composition (nominal) %
C Si Mn P S Cr Ni Mo
≤0.030 ≤0.8 ≤1.2 ≤0.035 ≤0.015 25 7 4

Others: N=0.3

Applications

SAF™ 2507 strip can be used in general strip applications where a good corrosion resistance is required. It is especially suitable for

  • Seawater applications
  • Chloride-containing bleaching environments in the pulp and paper industry
  • Chemical industry

In the cold-rolled condition SAF™ 2507 is a very good spring material for corrosive environments.

In the annealed condition the combination of high yield strength and good corrosion resistance is inviting to a new design approach for a variety of applications. Especially allowing for non-corrosion protected light weight constructions with a low life cycle cost.

Corrosion resistance

General corrosion

SAF™ 2507 is highly resistant to corrosion by organic acids, e.g. formic and acetic acid. Also in chloride contaminated acid the grade remains resistant.
SAF™ 2507 in the annealed, cold-rolled as well as cold-rolled and aged condition has passed salt spray tests during 500 h according to ISO 9227:2006 without any attack.

Pitting corrosion

The pitting corrosion resistance was assessed electrochemically by the method ASTM G150. The Critical Pitting Temperature (CPT) was measured with results according to the below table.

Condition Tensile strength, Rm, MPa CPT, oC CPT, oF
Annealed 900 >80 >176
Cold-rolled 1600 >80 >176
Cold-rolled and aged (480oC/3h) 2000 >80 >176

Bending

The values given below have been obtained by bending according to Swedish standard SS 11 26 26 method 3 (in a 90° V-block with a 25 mm die opening, a sample of 35 mm width, turned so that the burrs of the blanked edges face into the bend). They can be used as guidance for the smallest recommended bending radius.

Tensile strength Thickness Min bending radius, mm
MPa ksi mm in. //
900  131  1.1  0.043  0.4t 0.4t
1550  225  0.50  0.020  0.8t 13t
1650  239  0.28  0.011  1.4t 9t

// Parallel to the rolling direction
⊥ Transverse to the rolling direction
t is short for thickness

Forms of supply

The strip steel can be supplied in coils, bundles, on plastic spools or in lengths. The edges can be either slit, deburred or smoothly rounded.

Conditions and dimensions

SAF™ 2507 is supplied in the solution annealed (bright annealed or annealed
and pickled) or cold rolled condition.

Width

2-300 mm (0.078-12 in.)

Thickness

0.015-3.5 mm (0.0006-0.14 in.)

Heat treatment

Solution annealing

The recommended annealing cycle is 1050-1125°C (1920-2060°F) for 1-5 minutes, followed by rapid cooling in air or water.

Aging

The strength of cold-rolled SAF™ 2507 can be increased by a heat treatment operation at 480oC (900oF) for 3 h. An increase in tensile strength of 200-300 MPa and in proof strength of 400-500 MPa can be expected. Aging also increases the modulus of elasticity.
Aging is normally carried out after forming. If the aging is performed in an open-air furnace, a brownish oxide is formed on the surface. To avoid discoloration, parts should be carefully cleaned before heat treatment.

Mechanical properties

Static strength, nominal values at 20°C (68°F)
ConditionTensile strength, RmProof strength, Rp0,2a)Elongation, A11,3
MPaksiMPaksi%
A 900 131 600 87 30
C 1150 167 1100 160 14
C 1350 196 1250 181 6
C 1550 225 1400 203 4
CT 1850 268 1800 261 3
C 1800 261 1550 225 3

a) Rp0,2 corresponds to 0.2% offset yield strength.
1 MPa = N/mm2
A = Annealed
C = Cold rolled
CT = Cold rolled and aged, 480°C (896°F)/3 h (see further under section "Heat treatment".)

Fatigue strength

Nominal values at 20°C (68°F) in a normal dry atmosphere. The fatigue limit is defined as the stress at which 50% of the specimens withstand a minimum of 2 million load cycles.

Reversed bending stress

Average stress = 0
Bending transversal to rolling direction.

Tensile strength, RmFatigue limit, MPaTensile strength, RmFatigue limit, ksi
Thickness, mm Thickness, inch
MPa0,50ksi0.020
1850 ± 540 268 ± 78

Physical properties

The physical properties of a steel are related to a number of factors, including alloying elements, heat treatment and manufacturing process, but the following data can generally be used for rough calculations. The values refer to testing in the annealed condition at 20°C (68°F), where nothing else is mentioned.

Density: 7.8 g/cm3, 0.28 lb/in3

Thermal conductivity

Temperature, °C W/m °C Temperature, °F Btu/ft h°F
20 16 68 9
100 17 200 9.5
200 19 400 11
300 20 600 11.5
400 21 750 12.5

Metric units, W/(m °C)

Temperature, °C 20 100 200 300 400
SAF™ 2507 14 15 16 18 20
ASTM 316L 14 15 17 18 20

Imperial units, Btu/(ft h °F)

Temperature, °F 68 200 400 600 800
SAF™ 2507 8 9 9 10 12
ASTM 316L 8 9 10 10 12

Specific heat capacity

Temperature, °C J/(Kg °C) Temperature, °F Btu/(lb °F)
20 480 68 0.12
100 500 200 0.12
200 530 400 0.13
300 550 600 0.13
400 580 800 0.14

Thermal expansion

SAF™ 2507 has a coefficient of thermal expansion close to that of carbon steel. This gives SAF™ 2507 definite design advantages over austenitic stainless steels in equipment comprising of both carbon steel and stainless steel. The values given below are average values in the temperature ranges.

Metric units 1)

Temperature, °C
30-100 30-200 30-300 30-400
SAF™ 2507
13 13.5 14 14.5
Carbon steel (0.2%C)
12.5 13 13.5 14
ASTM 304L
16.5 17.5 18 18

1) (x10-6/°C)

Imperial units 1)

Temperature, °F
86-200 86-400 86-600 86-750
SAF™ 2507
7 7.5 7.8 8
Carbon steel (0.2%C)
7 7 7.5 7.5
ASTM 304L
9.5 9.5 10 10

1) (x10-6/°F)

Modulus of elasticity, E 1)
Condition Tensile strength, Rm, MPa E, MPa Tensile strength, Rm, ksi E, ksi
Cold rolled 1550 180 225 26.1
Cold rolled and aged 1850 210 268 30.5

1) (x103)

Welding

The weldability of SAF™ 2507 is good. Suitable welding methods are manual metal-arc welding with covered electrodes or gas shielded arc welding. Welding should be undertaken within the heat input range of 0.2-1.5 kJ/mm and with an interpass temperature of maximum 150°C (300°F).

Preheating or post-weld heat treatment is not necessary.

Matching filler metals are recommended in order to obtain a weld metal with optimum corrosion resistance and mechanical properties.

Disclaimer: Recommendations are for guidance only, and the suitability of a material for a specific application can be confirmed only when we know the actual service conditions. Continuous development may necessitate changes in technical data without notice. This datasheet is only valid for Alleima materials.