NXF UNS S20910 XM-19 Diameter DN15-1200 Pressure 150-2500lb Special Stainless Steel Forged Welding Neck Flanges

1. Raw Material PreparationMaterial Selection: Round or square steel billets are typically used. The material depends on the working conditions, commonly including carbon steel (A105), stainless steel (304/316L), or alloy steel.Blanking: Based on the weight (including losses) of the target flange, the steel is cut into billets using a saw.Physical and Chemical Testing: The materials provided by the steel mill must be accompanied by a Material Quality Report (MTR). The manufacturer will conduct spectral analysis to verify the chemical composition and ensure that the strength meets the standards.

2. Heating & Forging – The Most Critical StepHeating: The steel billet is placed in an industrial furnace (such as an induction furnace or gas furnace) for heating. Carbon steel is typically heated to 1000°C - 1200°C to achieve a plastic state.Die Forging/Free Forging:Die Forging: The red-hot steel billet is placed in a special die and subjected to intense impact through a forging press. Metal flows within the mold cavity, forming the flange and raised conical neck in a single process. Flanges produced using this method exhibit good grain flow and the highest strength.Rolling: For large-diameter weld neck flanges, holes are punched first, then the diameter is enlarged and the shape is pressed out using a rolling mill.Trimming and Punching: The flash generated during forging is removed, and a center hole is punched.

3. Heat TreatmentNormalizing/Annealing: Forging generates internal stress. By reheating the flange to a specific temperature and slowly cooling it, internal stress can be eliminated, internal grains refined, and the toughness and hardness uniformity of the metal improved.Solution Treatment: For stainless steel flanges, solution treatment is necessary to restore corrosion resistance.

4. MachiningRough Machining: Using a large vertical or horizontal CNC lathe, the oxide scale on the forging surface is removed, and the outer diameter and thickness of the flange are roughly machined.Fine Machining of the Conical Neck (Hub): This is the hallmark of a weld neck flange. A smooth, long, tapered bevel is machined for pipe connections.Facing: The flange is machined into a raised face (RF), flat face (FF), or ring face (RTJ) as required.For RF faces, tiny serrated lines (water lines) are cut to enhance the gasket's sealing effect.Drilling Bolt Holes: Using a dividing head or CNC drilling machine, evenly distributed bolt holes are precisely drilled on the flange.

5. BevelingA welding bevel is machined at the end of the tapered neck.This facilitates deep, full-penetration welding by creating a V-groove between the flange and the pipe during on-site installation.

6. Surface Treatment & InspectionCleaning and Rust Prevention: Carbon steel flanges are sandblasted to remove rust, then coated with rust-preventive oil, painted (yellow/black), or hot-dip galvanized. Stainless steel flanges undergo pickling and passivation.Flaw Detection: For flanges used in high-pressure environments, ultrasonic (UT) or magnetic particle (MT) testing is performed to ensure there are no forging cracks or porosity inside.Marking: The specifications, pressure rating, standard, material, and heat number are stamped on the flange edge using steel stamps.

7. PackagingThe flange sealing surfaces and bevels are very delicate and are fitted with plastic protective caps, finally packed into wooden crates to prevent damage during transportation.Do you need tolerance requirements for a specific standard (such as ASME B16.5), or do you want to see welding alignment techniques?