A Ni-Cu alloy with high strength and good corrosion resistance
- Excellent resistance to hydrofluoric acid
- Excellent resistance to sea water for marine applications
- High strength metal with good toughness at high temperatures
- Monel Grades: Alloy 400 and K500
- Weld neck flange features and benefits
Monel® weld neck flanges, like Monel 400 and K500, are made from a nickel-copper alloy and exhibit high strength, toughness and good corrosion resistance over a wide temperature range. An outstanding characteristic of Monel weld neck flanges is that they offer exceptional resistance to hydrofluoric acid, a particularly tough acid to deal with, in all concentrations up to the boiling point. For hydrofluoric acid applications Monel weld neck flanges are perhaps the most resistant of all commonly used specialty alloys.
Monel alloy 400 & K500 weld neck flanges also exhibit excellent corrosion resistance in marine applications and have reasonable corrosion resistance to sulfuric and hydrochloric acids under reducing conditions. Monel K500 weld neck flanges are over 2x as strong as Monel 400 weld neck flanges.
Because of these characteristics, Monel weld neck flanges are often found in marine and chemical processing applications.
The most common grades of Monel nickel alloy flanges are Monel 400 and Monel K500 . Gain more insight on these two grades by accessing our Monel 400 and K500 overviews or by contacting our engineering experts.
Monel 400, UNS N04400 (QQ-N-281), is a nickel-copper alloy with high strength and excellent corrosion resistance in a range of media including sea water, hydrofluoric acid, sulfuric acid, and alkalies. Monel 400 is commonly in marine engineering, chemical and hydrocarbon processing applications.
Monel 400 Specifications: BS3075NA13 (Wire), BS3076NA13 (Bar), ASTM B 164 (Rod, Bar, and Wire), ASTM B 564 (Forgings), ASME SB 164 (Rod, Bar, and Wire), ASME SB 564 (Forgings), AECMA PrEN 2305 (Wire for Rivets), SAE AMS 4675 (Bars and Forgings), SAE AMS 4730 (Wire), SAE AMS 4731 (Wire and Ribbon), DIN 17752 (Rod and Bar), DIN 17753 (Wire), DIN 17754 (Forgings), VdTÜV 263 (Sheet, Plate, Bar, and Tubing), QQ-N-281 (Plate, Sheet, Strip, Bar, Rod, Wire, and Forgings), Werkstoff 2.4360
Monel K500, UNS N05500 (QQ-N-286), is a precipitation-hardenable nickel-copper alloy that combines the corrosion resistance of Monel alloy 400 with greater strength (over 2x as strong) and hardness. It also has low permeability and is nonmagnetic to temperatures as low as -150°F (-101°C).
Monel K500 Specifications: BS3075NA18 (Wire), BS3076NA18 (Rod and Bar), ASTM B 865 (Rod and Bar), DIN 17752 (Rod and Bar), DIN 17753 (Wire), DIN 17754 (Forgings), QQ-N-286 (Rod, Bar, Wire, and Forgings), SAE AMS 4676 (Rod and Bar), ASME Code Case 1192 (Rod and Bar), ISO 9723 (Bar), ISO 9724 (Wire), ISO 9725 (Forgings), Werkstoff 2.4375
Monel weld neck flanges are best for hazardous, high pressure applications. Weld neck flanges are easily identified by their long tapered neck. The inside of the flange is bored to match the inside diameter of the pipe in order to ensure there is no restriction in flow and also to prevent turbulence at the joint. The tapered neck provides thicker metal at the flange joint, while the neck narrows down gradually to meet the pipe where it is butt welded to the pipe. This design helps to transfer stress from the flange to the pipe, as well as diminish stress concentration at the base of the flange connection.
Monel weld neck flanges are ideal for critical applications involving high pressure, sub-zero and elevated temperatures, as well as in conditions where fluctuations cause pipe expansion/contraction.
Key Feature: Ideal for high presure applications.
Weld Neck Flange Advantages
- Ability to withstand high pressure – since pipe is welded to the neck of the flange, stress is transferred to the pipe.
- The beveled end that, when connected to a pipe, creates a trough for a strong weld.
- Most versatile flange in the ASME stable of flanges.
Weld Neck Flange Disadvantages
- More advanced welding skill is needed for installation. The inside weld must be smooth to reduce friction and the outside weld must meet code criteria.
- Severe conditions that include high-pressure, high-cyclic and hazardous fluid applications.
- Fitting-to-fitting fabrication where the flange is welded directly to a fitting, such as an elbow, without the need for a short piece of pipe, as would be required with a slip-on flange.