Specialised Alloys Used In Pipe Fittings

November 18th, 2009

Although 304 chromium nickel, or austenitic, stainless steel pipe fittings are fine for low-spec applications, most high pressure and volatile chemical systems require a stronger, more resistant alloy.

At ChemiPetro we make alloy pipe flanges and fittings in titanium, molybdenum, duplex, super duplex and stainless steel. Each is graded according to the crystalline structure of the alloy, i.e. the percentage of other materials incorporated into the ferrite matrix.

Alloys are graded by the SAE or UNS system. The SAE 300 series (UNS ā€˜Sā€™ series) covers all nickel-chromium steel alloys. At ChemiPetro, we have a large range of pipe fittings in SAE 304 grade ā€“ the most common austenitic alloy produced.

The SAE 400/500 series covers Molybdenum steels, which are also classified under UNS S and N ratings. Titanium is one of a number of so-called exotic alloys, which does not have an SAE rating but is listed under UNS R ratings.

Where pipe flanges are used in corrosive environments or sea water, super austenitic alloys are used. Also called Moly 6 alloys (to differentiate from the 400 series molybdenum alloys) these come under SAE 600 ā€“ 665 categorisation. They offer great resistance to pitting and corrosion, due to their high molybdenum content (6% or higher) and addition of nitrogen during a secondary precipitation process. Additionally, higher nickel content provides great protection against cracking due to stress corrosion.

At ChemiPetro Ltd, we have high resistance pipe fittings in 4 grades of Moly 6 alloy. These are cheaper than titanium alloy pipe flanges, and offer tremendous longevity and protection in undersea pipelines, concentrated chemical plants and oil distillation columns.