A mid-ranged corrosion resistant alloy with good strength

pan head screw s

Originally developed to combat sea water corrosion, AL6XN has expanded its role as being good mid-range corrosion resistant alloy. AL-6XN pan head screws are a low carbon, high purity, nitrogen-bearing "super-austenitic" stainless alloy. With a higher nickel and molybdenum content than Duplex 2205 and Super Duplex 2507, it deliver better corrosion resistance while giving a more cost effective alternative to nickel super alloys like Inconel or Hastelloy in moderately corrosive conditions.

Corrosion Resistance
•  Moderate general corrosion resistance
•  Excellent chloride / salt water protection
•  Good performance in phosphoric acid
•  Moderate resistance to nitric acid

AL6XN Corrosion Comparison

 

Chemical Resistance
In chemical processes which utilize chlorides, such as paper mills and waste water, stress corrosion cracking (SCC) is a common culprit for 316L stainless failures. Duplex alloys will outlast environments that will cause SCC in 316 stainless, but for more severe low PH environments, pan head screws made from higher nickel content alloys like AL6XN will generally work better. For the most extreme situations, alloys with >45% nickel content like Hastelloy are often considered.

Outstanding Resistance to Salt Water
Seawater is where AL-6XN pan head screws outperform so many alloys providing protection to stress corrosion cracking, pitting and crevice corrosion in a broad range of marine applications. AL-6XN pan head screws contain a minimum of 6% molybdenum content and it is this addition of molybdenum that provides the greatest protection against pitting and crevice corrosion.

Mechanical Properties
Electrical Resistivity: 535 Ohm-circ mil/ft
Ultimate Tensile Strength: 108 ksi
0.2% Yield Strength: 53 ksi
Density: 0.291 lb/in 3

AL6XN strength Comparison v2

Chemistry
•  High molybdenum content provides enhanced corrosion protection in chloride environments.
•  Carbon helps to prevent sensitization during welding
•  Chromium enhances pitting and crevice corrosion resistance
•  The interstitial strengthening effect of nitrogen gives AL-6XN pan head screws good high strength properties

AL-6XN Applications
•  Desalination plants depend on AL-6XN pan head screws for the salt water corrosion protection
•  Pulp bleaching equipment and piping 
•  The power industry uses AL-6XN pan head screws where salt water and chlorides are present such as steam surface condensers, supercritical, high pressure, feed water heaters, steam surface condensers, flue-gas desulfurization equipment and in nuclear power water piping 
•  Offshore 
•  Chemical Processing - processing tanks, vessels and pipes as well as plate and frame heat exchangers.

Resources: Al-6XN Torque Specs

AL-6XN Screw Types: 12 Point ScrewsButton Head Cap ScrewsFlat Head ScrewsHex Cap ScrewsPan Head ScrewsSet ScrewsSocket Head Cap ScrewsTorx Screws


AL-6XN Pan Head Screw Features and Benefits

Pan head screws are flat on top and rounded on the sides. AL-6XN pan head screws are ideal for:

  • Small diameter fasteners – especially when the fastener size needed is too small for a wrench.
  • When phillips or slotted drivers are desired. For many high strength specialty alloys, only slotted drives are available.
  • Low torque applications because the drivers don’t offer as much force as a wrench.
  • Large diameter head provides more clamping area.

How Are They Different from Button Head Screws?
AL-6XN pan head and button head screws have very similar profiles however, button head screws allow for a hex socket driver whereas pan head screws do not.

 


AL6XN Chemical Composition & Specifications

AL-6XN Specifications: UNS N08367, ASTM A 240, ASTM B 688, ASME SA-240, ASME SB-688, ASTM B690, ASTM B691, ASTM A240, ASTM B688, ASME SA-240, ASME SB-688

AL6XN Chemistry 2


 AL-6XN Mechanical Data

 AL-6XN Tensile Data


Corrosion Curves for AL-6XN

HCL ISO CORROSION CURVE AL 6XN

 

Sulfuric Acid Iso CORROSION CURVE al-6xn

 

Phosphoric Acid Iso Corrosion Curve AL 6XN

 

Corrosion Chart AL6XN

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