What Is Duplex?
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The word duplex means different things depending on the context for example a duplex is a kind of apartment in the US.
In the context of building materials it means something that is composed of two parts. Many pipes and tubes are composed of two materials. If they are duplex pipes they are made of equal amounts of ferrite and austenite. This makes them resistant to corrosion and gives them a great deal of extra strength.
The Properties of Duplex Pipes
Duplex pipes are resistant to corrosion and cracking. They can withstand temperatures of up to 300 degrees and as low as -50 degrees. Normally Duplex stainless steel pipes are made of a 50/50 mix of ferrite and austenite. In some cases the mix is 60/40. They contain high levels of chromium (19-28%) and molybdenum, usually 5%. It is the high chromium content that stops the metal from corroding even in salt water. The technical term for this resistance to corrosion is passivity. Chromium, which does not rust, forms almost a protective film on the pipe and does so spontaneously during the production process.
Super duplex stainless steel normally contains 25% chromium and 7% nickel. It is called super because it has a far higher resistance to corrosion. Hyper duplex stainless steels are slowly being rolled out to the commercial market, which has even more strength and resistance to corrosion than super duplex stainless steel.
Compared to many other alloys with similar properties duplex stainless steels are relatively cheap. The fact it is so strong means that the walls of pipes made from it can be thinner.
Where Duplex Pipes Are Used
Duplex pipes are used extensively offshore. Both the oil and gas industries use them extensively. Salt water is highly corrosive, but duplex can resist this and be depended upon, which for these two industries is critical. The tensile strength of the material and the fact it does not corrode means that pipes made from duplex stainless steel can have far thinner walls. This makes them easier and cheaper to transport and to manoeuvre into place. |
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Author Resource:-
SPM sells all kinds of duplex pipes. SPM stands for special piping materials and SPM has decades of experience within the industry.
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By :
Gareth Hoyle
Submitted
2011-10-24 04:40:41 |
Article From Article Mayhem
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