Forged flanges are used in diversified oil and gas, petrochemical, power-generating, and construction industries. They maintain leak-tight piping because the piping components, valves, pumps, and other equipment are combined.
All the strength, durability, pressure and temperature, and corrosion resistances of the forged flanges depend on their manufacturing process. An understanding of what takes place during the fabrication of this kind of flange will be helpful in explaining why it is that forged flanges are better compared to the remaining applications.
It is through this article that the main stages which are involved in the manufacturing process of forged flanges, from the selection of material up to quality control, will be discussed.
1. Material Selection
Material selection forms the very first process for the manufacturing of forged flanges, and it primarily determines the mechanical property of the flange. In addition to carbon steel, stainless steel, and alloy steel, several other materials may find applications.
The most commonly used standards used here are ASTM A105 for carbon steel which predominately happens in high-temperature usage. Some of the standards prevailing in this industry include ASTM A182 for alloy and stainless steel, which are used under high-pressure and high-temperature conditions, and ASTM A350, which comprises carbon and low-alloy steel for low-temperature conditions.
All these standards are different, providing corrosion protection, tensile strength, and even temperature tolerance to ensure that the flange works as it is supposed to.
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2. Cutting the Raw Material
After selecting the raw material, billet cutting is performed in a forge. Massive metal billets or slabs are raw sources from which these kinds of forges originate. The great chunks are cut into smaller billets through saws or cutting torches.
The pieces of raw material shall depend on the type of flange that is being produced as well as its finished dimensions. The proper cutting assures the readiness of material in the forging process and reduces waste in production.
3. Heating
The cut pieces of steel billets are heated in the furnace to a very high temperature, usually between 2,200°F and 2,500°F (1,200°C to 1,370°C), to get the metal hot so it can be shaped under pressure without breaking or developing cracks. The process is one to ensure the quality of the forged product, so heating should be closely monitored.
4. Forging Process
The most significant forging process in the manufacture of forged flanges is applied since heated billets are exposed to extreme pressure through very powerful forging machines, hammers, or presses. As a result, a betterment and improvement of the grain structure of metal lead to mechanical properties that involve strength, toughness and wear resistance.
There are three choices: open-die forging, in which material is pressed between flat dies; closed-die forging, with material enclosed in shaped, dies to produce precision, smaller flanges; and ring-rolling, often used for slip-on or weld neck flanges, where a heated billet is punched out to create a circular shape.
Forging reduces internal porosity, voids, and inclusions that are characteristic of most castings to provide, therefore, stronger and more durable flanges.
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5. Trimming and Shaping
The flange is still in a very rough form after forging and, hence, needs further smoothening. The stage subsequent to this is trimming, after which excess material, referred to as “flash,” is removed from the flange using trimming tools or trimming machines. It will then make sure that the flange gets the size as well as the shape required.
At this point, the flange may also be further formed to complete its shape. The final dimensions are typically achieved through precise machining so that the flange mates and assembles correctly with other piping components.
6. Heat Treatment
The other major process in flange manufacturing through forging is heat treatment, which alters some of the mechanical properties of the flange to make it harder, stronger, and even more ductile.
The three major heat treatment processes applied to flanges during the production process are annealing, where the flange is heated at a high temperature and then slowly cooled in order to relieve the internal stresses and soften the metal; normalizing, which involves heating to above the critical temperature of the flange but air-cooled for a balance of its grain structure and further toughness; and quenching and tempering, in which the heated flange is cooled rapidly in its surface layers, then reheated to achieve the balance between hardness and ductility.
Each process of the heat treatment has a unique function of making the flange hard enough to meet intended application requirements while possessing suitable flexibility and toughness.
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7. Machining and Surface Finishing
Once the flange is forged and heat-treated, it is milled in for precise tolerances and surface finishes that are required. CNC machines facilitate this in a more precise manner to produce well-defined dimensions and surfaces critical for the performance of good flanges.
Machining operations cover turning off the flange’s outer diameter and face, drilling bolt holes to mount on other components, and facing a flat and smooth flange face to achieve an ideal seal by the gasket. Applied surface finishes improve the aesthetic look of the flange besides providing extra protection against corrosion and wear.
Apart from this, other coatings like zinc plating or powder coating may be applied to increase the durability according to the material and application.
8. Quality Control and Inspection
A forged flange is also subjected to quality control as part of its manufacturing process. After machining and application of surface finishes to the flanges, every flange has to be tested strictly to prove its adherence to specifications and industry standards.
Other common tests include dimensional inspection with the use of calipers and micrometers to determine whether the dimensions of the flange lie within the tolerance limits. There is non-destructive testing, like ultrasonic testing, radiography as well as magnetic particle inspection which can identify flaws within the flange without causing any damage.
Pressure testing, where the hydrostatic or pneumatic pressure tests the strength as well as the sealing ability of the flange is also included. Standards like ASME B16.5, ASME B16.47, ASTM A105, and ASTM A182 ensure the forged flanges are in accordance with industry standards for their mechanical and material requirements to perform safely and reliably in critical applications.
Also Read: A Comprehensive Guide to Forged Flanges Manufacturing
9. Final Assembly and Packaging
If the forged flanges pass all quality control checks, they are then ready for final assembly, which might include attaching parts such as gaskets or bolts as requested by the customer. The flanges are carefully packaged to prevent shipping damage, and extra care is taken to avoid all dirt, moisture, and other contaminants from contaminating the flanges and, therefore, their effectiveness.
Conclusion
Forging the flanges is a complex process comprising an extensive stage. Manufacturing involves choosing the raw materials, forging, heat treatment, and quality inspection.
These stages are crucial to ensure that the final product will meet the demands required for such an environment in high-pressure and high-temperature corrosion and exposure to all of these factors within industries such as oil and gas, petrochemicals, and power generation.
Knowing the manufacturing process in the forging of flanges leaves most people to wonder why these flanges are so strong and necessary for the safe and efficient operation of the industrial piping system.