Duplex Steel Tube

Duplex stainless steel offers excellent resistance to corrosion and very high mechanical strength. The high corrosion resistance of duplex stainless steel ensures significantly more uptime than carbon steel and conventional stainless steel, while the mechanical strength allows for lighter constructions, a more compact system design, and less welding.

Duplex stainless steels are extremely corrosion resistant, and work hardenable alloys. Duplex stainless steel plate contains relatively high levels of chromium (between 18% and 28%) and low to moderate amounts of nickel (between 1.5% and 8%). The high corrosion resistance and excellent mechanical properties of duplex stainless steels can be attributed to their chemical composition and balanced (duplex) microstructure of approximately equal volume percentages of ferrite and austenite. Because of this duplex nature, it will display properties characteristic of both austenitic and ferritic stainless steels. Duplex stainless steels are in most cases, tougher than ferritic stainless steels. The strengths of duplex stainless steels can in some cases be double that of austenitic stainless steels.

Due to their high strength and corrosion resistance properties, Duplex Stainless Steels are used in a variety of applications such as:

? Pressure vessels, reactor tanks, and heat exchangers

? Desalination plants and seawater systems

? Water transmission pipes

? Rotors, impellers, and shafts in industrial equipment

? Stock washers and other equipment for the pulp and paper industry

? Absorber towers, and FGD systems for air pollution control

? Phosphoric acid production

? Food, oil and gas, mining, and architectural applications

? Biofuels plants

Duplex Stainless Steel combines many of the beneficial properties of ferritic and austenitic materials to provide both high strength and good corrosion resistance. Due to their high chromium, molybdenum, and nitrogen contents and duplex structure, these steels offer many benefits in comparison to 300 series austenitic grades:

? High Strength – Approximately twice the level of austenitic

? Good resistance to pitting and crevice corrosion

? Excellent resistance to stress- corrosion cracking

? Good erosion and fatigue resistance

? Good weldability and increased heat transfer

? More stable pricing due to lower Ni levels than austenitic stainless grades

The microstructures inside duplex stainless steels are approximately 50 percent austenite and 50 percent ferrite, and consequently, duplex products share the physical properties of both ferritic and austenitic grades. Duplex stainless steels are resistant to the cracking caused by chloride stress corrosion in austenitic grades, and have improved resistance to localized corrosion. This family of stainless steels has roughly twice the yield strength of their counterpart austenitic grades which means we can use it to design thinner gauge tubing. Higher hardness values provide better wear resistance for high-precision tubes.

Duplex steels are easily welded and formed, similar to austenitic grades. Depending on chromium, nickel, and molybdenum content, duplex stainless steels are divided into four main categories: lean duplex, duplex, super duplex, and hyper duplex. This family of alloys has great advantages in both material and engineered fabrication costs.

Typical applications for this alloy group include heat exchanger tubes, umbilicals, structural tanks, pulp and paper-making equipment, pipes and fittings, and seawater handling systems.

We manufacture duplex stainless steel tubes in the following alloys:

Duplex      S31803     1.4462

Super Duplex   S32750     1.4410

Duplex Stainless Stee Pipe Seamless and welded manufacturer suppliers.

Duplex stainless steel pipe (manufacturer suppliers) has good welding performance, compared with ferritic stainless steel and austenitic stainless steel, it is neither like ferritic stainless steel weld heat affected zone, as grain coarsening and makes the plastic toughness sharply lower, and also doesn't like austenitic stainless steel, the welding thermal crack is more sensitive.

Specifications：

- ASTM A789 Standard Specification for Seamless and Welded Ferritic/Austenitic Stainless Steel Tubing for General Service

- ASTM A790 (ASME SA790) Standard Specification for Seamless and Welded Ferritic/Austenitic Stainless Steel Pipe

- ASTM A928 (ASME SA928) Standard Specification for Ferritic/Austenitic (Duplex) Stainless Steel Pipe Electric Fusion Welded with Addition of Filler Metal

- GB/T 21832-2008 Austenitic--Ferritic(duplex) grade stainless steel welded tubes and pipes

- GB/T 21833-2008 Austenitic-Ferritic (duplex) grade stainless steel seamless tubes and pipes        

Features：

- Superior resistance to general and local corrosion, especially to stress corrosion, pitting corrosion, crevice corrosion, corrosion fatigue, and abrasion & corrosion.

- Good weldability

- Good mechanical properties

- Excellent intergranular corrosion resistance

- High cost-effectiveness, long lifetime

Duplex stainless steel was developed to combat common corrosion problems encountered with the 300 series

stainless steel. “ Duplex ” describes a family of stainless steels that are neither fully austenitic, like 304 stainless, nor purely ferritic, like 430 stainless. The advantage of a duplex structure is that it combines the favorable qualities of a ferritic alloy ( stress corrosion cracking resistance and high strength ) with those of an austenitic alloy ( ease of fabrication and corrosion resistance ).

Application

- Petroleum

- Chemical industry

- Instrument

- Industrial transportation

- Mechanical structure industry

- Need high corrosion ability pipe's industry, such as offshore industry, etc

Advantages

- Superior surface finish,

- Better mechanical property

- More precise dimension

- Perfect inspection method and inspection equipment

We also deal with super duplex pipes. 

Our stainless steel seamless pipe was widely used in Mining, Energy, Petrochemical, Chemical Industries, Food plant, Paper plant, Gas, and Fluid Industries, etc.

- Standard: ASTM A790/A789 PICKLED AND ANEANLED

- Material: S31803/S31500/S32750 etc

- OD: 6MM-710MM  

- Thickness: 2.5mm-50mm

- Certificate: PED, ISO, GB, GOST

- Producing method: cold drawn and cold rolled

Stainless Steel Pipe:

- Material: S31803/S31500/S32750 ETC

- O.D: 6mm-710mm

- Thickness: 2.5mm-50mm

- A999/A999M: Each pipe shall be subjected to the nondestructive electric test or the hydrostatic test, the type of test to be used shall be at the option of the mfg unless otherwise specified in the PO.

- The Pipe lengths: Unless otherwise agreed upon, all sizes from NPS 1/8” TO AND INCLUDING NPS 8 are available in a length up to 24ft with the permitted range of 15 to 24 ft. Short lengths are acceptable and the number and min, length shall be agreed upon between mfg and purchaser.

- The finished pipe shall be reasonably straight and shall have a workmanlike finish, Removal of imperfections by grinding is permitted, provided the W.T are not decreased to the lens than the permitted in Section 9 of Specification A999/A999M

- Butt Weld End:  According to ANSI B 16.25

- Pipe Marking: Specified in A999/999M, include “Logo+Standard+SIZE+Heat No.+Lot No.+H.T/E.T/U.T”

- Packing: Each Pipe end is protected by a Plastic cap. Then packed by an Anti-rust steel strip, The outside of the bundle is a plastic woven bag or Plastic film.

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