Carbon steel Weld Neck Flange

Common outer diameters: 1/2”, 2”, 3”, 4”, 6”, 8”, 10”, 12” to 24”.
Special made outer diameters: up to 60”.
Class range: Class 150, 300, 400, 600, 900, 1500, 2500(# or LB). PN 2.5 to PN 250.
Flange face type: RF (Raised Face), RTJ (Ring Type Joint)

The most frequently requested flange, the Weld Neck Flange, features a neck extension and weld bevel. Provides a natural form connection ideal for larger, high-pressure applications.

Weld neck flanges, also known as WN flange, tapered hub flange or high-hub flange,s a kind of flange that can relocate stress to the pipes, ensuring a decrease in high-stress concentration at the bottom of the flange.

Welding Neck Flanges are easy to recognize as the long tapered hub, which gradually over to the wall thickness from a pipe or fitting. The long tapered hub provides an important reinforcement for use in several applications involving high pressure, sub-zero, and/or elevated temperatures. The smooth transition from flange thickness to pipe or fitting wall thickness effected by the taper is extremely beneficial, under conditions of repeated bending, caused by line expansion or other variable forces.

These WN flanges are bored to match the inside diameter of the mating pipe or fitting so there will be no restriction of product flow. This prevents turbulence at the joint and reduces erosion. They also provide excellent stress distribution through the tapered hub. The Weld neck flanges are attached by butt-welding to the pipes. These are used mainly for critical services where all the weld joints need a radiographic inspection.

While specifying these WN flanges, the thickness of the welding end also should be specified along with flange specification.

ASTM A105 for carbon steel welding neck flanges.
ASTM A182 for alloy and stainless welding neck flange.
ASME B16.5
ASME B16.47
BS 3293
DIN 2630 PN 1 and PN 2.5, 2631 PN 6, 2632 PN 10, 2634 PN 16, 2634 PN 25, 2635 PN 40

Before ordering the weld neck flange, the companies shall need to confirm the material standard, outer diameter, pressure class, face type and thickness schedule.

A standard description for a welding neck flange is: “Flange, 10” Weld Neck, Class 150, RF, Schedule 40, ASTM A105 ASME B 16.5.”

Carbon Steel (ASTM A105, A350 LF2) – General industrial use
Stainless Steel (ASTM A182 F304/F316) – For corrosive or high-purity applications
Alloy Steel (ASTM A694 F42-F70) – High-pressure & low-temperature performance
Duplex & Super Duplex (ASTM A182 F51/F53/F55)– For extreme environments
Nickel Alloys (Inconel, Monel, Hastelloy) –  Specialized industries like petrochemicals

Weld neck flanges are used in situations where conditions are tough. Some common scenarios include:

• High-pressure systems
• Wide temperature and pressure fluctuations
• High-temperature environments
• Handling volatile and hazardous fluids
• Working in very cold conditions

The WN flanges are built to handle such challenging conditions, thanks to their strong construction and excellent stress distribution capabilities.

The forging process generally consists of the following steps:

• Selecting high-quality billet blanking
• Heating
• Forming
• Forging
• Cooling