Super Duplex Stainless Steel 2507(UNS S32750 and UNS S32760)

wilsonpipeline Pipe Industry Co., Limited supplies super duplex stainless steel in bar, pipes, pipe fittings, flanges, tube and weld wire. Duplex Stainless Steels, also referred to as austenitic-ferritic stainless steels, are a family of grades having around equal proportions of austenite and ferrite.

These steels have a duplex microstructure which contributes to their high strength and high resistance to stress corrosion cracking. Duplex steels offer high resistance to uniform and local corrosion because of their high content of nitrogen, chromium and molybdenum. Duplex stainless steels have good weldability.

There are three groups of duplex stainless steels that include the following:

• Lean Duplex
• Standard Duplex
• Super Duplex.

The most widely used of the duplex grades is duplex 2205. However, the super duplex steels like 2507 are excellent for servicing severe corrosive environments, such as offshore and marine applications. Lean duplex 2101 is available as an economic alternative to 300 series stainless steels.

S32760 Super Duplex Stainless Steel

S32760 super duplex stainless steel is developed to be used in aggressive environments. Properties of S32760 include toughness, high strength, corrosion resistance in a large number of organic and inorganic acids. Finally it features high resistance to strong alkalis and resists corrosion in a number of non-oxidizing acids.

While involving extended exposure to temperatures more than 572F use of S32760 is not recommended. The chemical composition of S32750 and S32760 are similar; however, the latter contains slightly more copper and tungsten. The copper content (min. 0.5, max 1.0) permits excellent resistance to corrosion in many non-oxidizing and mineral acids like hydrochloric and sulfuric acid.

S32750 or Duplex 2507

Duplex 2507 is a super duplex stainless steel developed for applications that demand high strength and corrosion resistance. Alloy 2507 has 25% chromium, 4% molybdenum, and 7% nickel. This high molybdenum, chromium and nitrogen content causes high resistance to chloride pitting and crevice corrosion attack and the duplex structure provides 2507 with exceptional resistance to chloride stress corrosion cracking.

Using Duplex 2507 must be restricted to applications below 600° F (316° C). Extended elevated temperature exposure can reduce both the toughness and corrosion resistance of alloy 2507.

Duplex 2507 has good mechanical properties. Often a light gauge of 2507 material can be used to achieve the same design strength of a thicker nickel alloy. The resulting weight savings can considerably reduce the overall cost of fabrication.

                                                   

Figure 1. Forms of Super Duplex 2507 Available at wilsonpipeline Pipe Industry Co., Limited.

Chemical Composition

The chemical composition of S32760 is provided in the table below:

Cr	Ni	Mo	C	W	Cu
24.0-26.0	6.0-8.0	3.0-4.0	0.030 Max	0.5-1.0	0.50-1.0

N	Mn	Si	P	S	Fe
0.2-0.3	1.00 Max	1.0 Max	0.03 Max	0.01 Max	Balance

The chemical composition of S32750 or 2507 is provided in the table below:

Cr	Ni	Mo	C	N	Mn
24.0-26.0	6.0-8.0	3.0-5.0	0.030 Max	.24-.32	1.20 Max

Si	Cu	P	S	Fe
0.80 Max	0.50 Max	0.035 Max	0.020 Max	Balance

General Properties

Properties of Duplex Stainless Steels

The properties of duplex stainless steels are:

• High resistance to uniform corrosion.
• High to pitting and crevice corrosion.
• Good resistance to stress corrosion cracking and corrosion fatigue.
• High mechanical strength.
• Good sulfide stress corrosion resistance.
• Good abrasion and erosion resistance.
• Good fatigue resistance high energy absorption.
• Low thermal expansion.
• Good weldability.

Properties of Super Duplex Stainless Steel S32760

The properties of super duplex stainless steel S32760 are:

• Guaranteed corrosion performance (PREn ≥ 40).
• Excellent corrosion resistance in mineral acids such as hydrochloric and sulfuric acids.
• High resistance to pitting and crevice corrosion.
• Excellent resistance to stress corrosion cracking in both chloride and sour environments.
• High resistance to erosion, corrosion and corrosion fatigue.
• Excellent mechanical properties.
• Possibility for weight reduction over austenitic, standard duplex and nickel base alloys.
• Good weldability.

Mechanical Properties (Room Temperature, Solution Annealed Condition)

Tensile Strength, ksi	.2% Yield Strength, ksi	% Elongation in 50mm	Hardness Max.
109	80	25	28 HRC

Properties of Super Duplex Steel 2507 or S32750

• High resistance to chloride stress corrosion cracking.
• High Strength.
• Combination of properties given by austenitic and ferritic structure.
• Good weldability and workability.
• Superior resistance to chloride pitting and crevice corrosion.
• Good general corrosion resistance.
• Suggested for applications up to 600° F.
• Low rate of thermal expansion.

Mechanical Properties(Specified Tensile Properties, Plate ASTM A240)

Ultimate Tensile Strength, ksi Minimum	.2% Yield Strength, ksi Minimum	% Elongation Min.
116	80	15	310

Applications

Applications of Duplex Stainless Steels

The applications of duplex stainless steels are:

• Oil and gas equipment.
• Offshore technology.
• Pulp and paper industry.
• Cargo tanks and pipe systems in chemical tankers.
• Firewalls and blast walls on offshore platforms.
• Bridges.
• Storage tanks.
• Pressure vessels, reactor tanks, and heat exchangers.
• Rotors, impellers and shafts.
• Seawater desalination plants.
• Chemical industry, especially when handling chlorides.
• Flue-gas cleaning.
• Desalination plants and seawater systems.

Applications of Super Duplex Stainless Steel S32760

The applications of S32760 super duplex stainless steel are:

• Oil and gas industry applications.
• Pollution control.
• Pulp and paper.
• Desalination.
• Mining and mineral industries.
• Marine industries.
• Power generation.
• Flue-gas desulfurization.
• Chemical, pharmaceutical.

Applications of S32750 Super Duplex Stainless Steel

The applications of S32750 super duplex stainless steel are:

• Desalination Equipment.
• Chemical process pressure vessels, piping and heat exchangers.
• Marine Applications.
• Flue Gas Scrubbing Equipment.
• Pulp & Paper Mill Equipment.
• Offshore Oil production/technology.
• Oil and gas industry equipment.

This information has been sourced, reviewed and adapted from materials provided by wilsonpipeline Pipe Industry Co., Limited.

For more information on this source, please visit wilsonpipeline Pipe Industry.

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