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Duplex 2507 Stainless Steel for Pipe and Tube

Penn Stainless can provide Duplex  2507, a super duplex stainless steel with 25% chromium, 4% molybdenum, and 7% nickel. 2507 is intended for applications that necessitate exceptional strength and corrosion resistance. Sample applications include chemical processing, petrochemical, and seawater equipment. Duplex 2507 has great resistance to chloride stress corrosion cracking, high thermal conductivity and a low coefficient of thermal expansion. This grade also possesses outstanding resistance to pitting, crevice and general corrosion, thanks to its high chromium, molybdenum, and nitrogen levels.

General Properties

Duplex 2507 (UNS S32750) is a super duplex stainless steel with 25% chromium, 4% molybdenum, and 7% nickel designed for demanding applications which require exceptional strength and corrosion resistance, such as chemical process, petrochemical, and seawater equipment. This grade has outstanding resistance to chloride stress corrosion cracking, high thermal conductivity, and a low coefficient of thermal expansion. Duplex 2507 also has great resistance to pitting, crevice, and general corrosion thanks to its high chromium, molybdenum, and nitrogen levels.

Applications

  • Oil and gas industry equipment
  • Offshore platforms, heat exchangers, process and service water systems, fire-fighting systems, injection and ballast water systems
  • Chemical process industries, heat exchangers, vessels, and piping
  • Desalination plants, high pressure RO-plant and seawater piping
  • Mechanical and structural components, high strength, corrosion-resistant parts
  • Power industry FGD systems, utility and industrial scrubber systems, absorber towers, ducting, and piping

Standards
ASTM/ASME ………. A240 – UNS S32750
EURONORM………… 1.4410 – X2 Cr Ni MoN 25.7.4
AFNOR……………….. Z3 CN 25.06 Az

General Corrosion

  • high chromium and molybdenum content of 2507 makes it extremely resistant to uniform corrosion by organic acids like formic and acetic acid.
  • provides excellent resistance to inorganic acids, especially those containing chlorides.
  •  can be used in dilute hydrochloric acid.
  • Pitting need not be a risk in the zone below the borderline in this figure, but crevices must be avoided.

Intergranural Corrosion

  • Low carbon content minimizes the risk of carbide precipitation at the grain boundaries during heat treatment.
  • Very resistant to carbide-related intergranular corrosion.

Stress Corrosion Cracking

  • Duplex structure of 2507 provides excellent resistance to chloride stress corrosion cracking (SCC).
  • Superior to 2205 in corrosion resistance and strength.
  • 2507 is especially useful in offshore oil and gas applications and in wells with either naturally high brine levels or where brine has been injected to enhance recovery.

Pitting Corrosion

  • Different testing methods can be used to establish the pitting resistance of steels in chloride-containing solutions.

Crevice Corrosion

  • Highly resistant to crevice corrosion.

 

Hot forming
2507 should be hot worked between 1875°F and 2250°F, followed immediately by a solution anneal at 1925°F minimum and a rapid air or water quench.

Cold Forming
Many of the usual stainless steel forming methods can be used for cold working Duplex 2507. This grade has higher yield strength and lower ductility than the austenitic steels, so fabricators often find that higher forming forces, increased radius of bending, and increased allowance for springback are necessary. Deep drawing, stretch forming, and similar processes are more difficult to perform on 2507 than on an austenitic stainless steel. When forming requires more than 10% cold deformation, a solution anneal and quench are advised.

Heat Treatment
Duplex 2507 should be solution annealed and quenched after either hot or cold forming. Solution annealing should be done at a minimum of 1925°F. Annealing should be followed immediately by a rapid air or water quench. To achieve maximum corrosion resistance, heat treated products should be pickled and rinsed.

Welding
2507 possesses good weldability, and can be joined to itself or other materials by shielded metal arc welding (SMAW), gas tungsten arc welding (GTAW), plasma arc welding (PAW), flux cored wire (FCW), or submerged arc welding (SAW). 2507/P100 filler metal is suggested when welding 2507 because it will produce the appropriate duplex weld structure.

Preheating of 2507 is unnecessary except to mitigate condensation on cold metal. The interpass weld temperature should not exceed 300°F or the weld integrity may be adversely affected. The root should be shielded with argon or 90% N2/10% H2 purging gas for maximum corrosion resistance. The latter provides better corrosion resistance.

 

Chemical Properties

Typical values (Weight %)

C Cr Ni Mo N Others
0.020 25 7 4.0 .27 S=0.001

Mechanical Properties:

Ultimate Tensile Strength, ksi 116 min.
0.2% Offset Yield Strength 0.2%, ksi 80 min.
0.1% Offset Yield Strength 0.2%, ksi 91 min.
Elongation in 2 inches, % 15 min.
Hardness Rockwell C 32 max.
Impact Energy, ft.-lbs. 74 min.

Physical Propertries

Density lb/in3 0.28
Modulus of Elasticity psi x 106 29
Coefficient of Thermal Expansion
68-212°F/°F
x10-6/°F 7.2
Thermal Conductivity Btu/h ft °F 8.7
Heat Capacity Btu/lb/°F 0.12
Electrical Resistivity W-in x 10-6 31.5

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