Steel Tube

Duplex Steel Tube

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


Duplex stainless steels are extremely corrosion resistant, 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. Strengths of duplex stainless steels can in some cases be double that for 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, FGD systems for air pollution control

• Phosphoric acid production

• Food, oil and gas, mining and architectural applications

• Biofuels plants

Duplex Stainless Steels combine 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 austenitics

• 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 per cent austenite and 50 per cent 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 localised 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 manufactures 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 the ferritic stainless steel and austenitic stainless steel, it is neither like ferritic stainless steel weld heat affected zone, as grain coarsening and make the plastic toughness sharply lower, also don't like austenitic stainless steel, the welding thermal crack is more sensitive.


Duplex stainless steel pipe manufacturer suppliers safety use restrictions and requirements

1. The need to control the phase ratio, the most appropriate proportion is ferrite and austenite meet each half, including a number of not more than 65%, so as to ensure the best comprehensive performance. If two phase imbalance, such as too many ferrite phase, it is easy to form in welding HAZ, single-phase ferrite in some medium is sensitive to stress corrosion cracking.

2. Need to master organization change law of duplex stainless steel tube, and familiar with each steel grade TTT CCT curve, this is the correct guidance for duplex stainless steel heat treatment, hot forming technology is the key, such as precipitation of duplex stainless steel brittle phase are much more sensitive than austenitic stainless steel.

3. Continuous use of duplex stainless steel pipe manufacturer suppliers- 50 ~ 250 ℃ temperature range, the lower limit depends on the brittle transition temperature, steel cap is limited by 475 ℃ brittleness, the maximum temperature should not exceed 300 ℃.

4. The duplex stainless steel pipe manufacturer suppliers after solid solution treatment need to be fast, slow cooling leads to the precipitation of brittle phase, which can lead to the toughness of the steel, especially the local corrosion resistance.

5. High chrome molybdenum hot working of duplex stainless steel tube and the lower limit of thermoforming temperature not lower than 950 ℃, super duplex stainless steel is not less than 980 ℃ low chromium molybdenum duplex stainless steel is not less than 900 ℃, avoid caused by brittle phase separation in the process of surface crack

6. You can't use of austenitic stainless steel commonly used 650-800 ℃ eliminating stress processing, generally USES solid solution annealing treatment. For surfacing duplex stainless steel in low alloy steel, the need for 600-650 ℃ the overall elimination should be processing, must be considered due to the precipitation of brittle phase of toughness and corrosion resistance, especially the resistance to local corrosion performance degradation, as far as possible, shorten the heating time in this temperature range. Heat treatment of low alloy steel and duplex stainless steel clad plate problems also want the same consideration. [1]

7. Need to be familiar with understand the laws of duplex stainless steel pipe welding

Duplex stainless steel (DSS) is featured with structure of two phases (α and γ) and has characteristics of both ferritic and austenitic stainless steel. It has good corrosion resistance and high strength. It is alloyed with 18%-28% Cr and 3%-10% Ni in the condition of low C. Some steels also contain the alloy elements such as Mo, Cu, Nb, Ti and N, etc.

Comparing with ferritic stainless, duplex stainless steel has higher plasticity, ductility and better intergranular corrosion resistance and weldability. It keeps same 475℃ brittleness with ferritic stainless and high thermal conductivity. Duplex has improved yield strength, resistance to intergranular corrosion, stress corrosion, corrosion fatigue and abrasion & corrosion compared with austenitic stainless steel.

Grades:S31803/S32205, S32750, S32760, S31500, 32001, S32003, S32304



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 stainlee steel seamless tubes and pipes        


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

2.Good weldability

3.Good mechanical properties

4.Excellent intergranular corrosion resistance

5.High cost-effectiveness, long life time


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

stainless steels . “ 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 ) .


a) Petroleum

b) Chemical industry

c) Instrument

d) Industrial transportation

e) Mechanical structure industry

f) Need high corrision ability pipe's industry, such as offshore industry etc


a) Superior surface finish,

b) Better mechanical property

c) More precise dimension

d) Perfect inspection method and inspection equipment


We also deal with super duplex pipes. 

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


2 Material: S31803/S31500/S32750 etc

3 OD: 6MM---710MM  Thickness: 2.5mm---50mm

4 Certificate: PED, ISO, GB, GOST

5 Producing method: cold drawn and cold rolled

Stainless Steel Pipe:

1. Material: S31803/S31500/S32750 ETC

2. O.D: 6mm-710mm , Thickness:2.5-50mm

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

4. The Pipe lengths : Unless otherwise agreed upon, all size 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 length are acceptable and the number and min, length shall be agreed upon between mfg and purchaser.

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

6. Butt Weld End:  According to ANSI B 16.25

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

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

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