A mid-ranged corrosion resistant 6Mo alloy with good strength

• Good corrosion resistance to moderate acids & sea-water 
• 50% stronger than stainless steel
• Usable temperature limit of 1000°F
• AL6XN chemistry & specifications
• Slip on flange features and benefits
• AL6XN Datasheet

Originally developed to combat sea water corrosion, AL6XN has expanded its role as being good mid-range corrosion resistant alloy. AL6XN slip on flanges are a low carbon, high purity, nitrogen-bearing "super-austenitic" stainless alloy. Also considered a 6Moly alloy, AL6XN flanges are similar in chemistry to SMO 254 and Alloy 926.With a higher nickel and molybdenum content than Duplex 2205 and Super Duplex 2507, it delivers 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

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, slip on flanges 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 AL6XN slip on flanges outperform so many alloys providing protection to stress corrosion cracking, pitting and crevice corrosion in a broad range of marine applications. AL6XN slip on flanges 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

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 AL6XN slip on flanges good high strength properties

AL6XN Applications
•  Desalination plants depend on AL6XN slip on flanges for the salt water corrosion protection
•  Pulp bleaching equipment and piping 
•  The power industry uses AL6XN slip on flanges 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: AL6XN Torque Specs, Flange Dimensions, Flange Bolting Chart

Flange Types Available: Blind Flanges, Lap Joint Flanges, Slip On Flanges, Socket Weld Flanges, Threaded Flanges, Weld Neck Flanges

AL6XN Chemical Composition & Specifications

AL6XN 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 Mechanical Data

Corrosion Curves for AL6XN

AL6XN Slip on Flange Features & Benefits

AL6XN slip on flanges are similar to the socket weld flange but without the socket shoulder. When using a socket weld flange, the pipe rests against this internal shoulder. Since a slip on flange does not have shoulder, the pipe can slide completely through the flange hub and is free to spin. 

Advantages

• Typically lower in price than weld-neck flange, yet welding costs can be more.
• There is a reduced need to cut the pipe length accurately, making it easier to install.
• The slip on flange is free to spin on the pipe for easy bolt alignment.

Disadvantages

• They require two fillet welds: one fillet weld at the hub of the flange and a second weld at the inside diameter of the flange near the flange face.
• Though they can be used for high temperature and pressure applications, they typically are not as other flange types give a more secure joint.