How to get high quality forged flanges?

What is a forged flange?

The mechanical properties of forged flange is a flange in the product the best products, its raw materials are generally billet, then after cutting and then continue to beat, to eliminate the ingot segregation, porosity and other defects. Both the price and the mechanical properties are one grade higher than the common cast flange. Flanges are parts that connect pipes to pipes and valves. They are connected to the ends of pipes. They are also used for flanges on the inlet and outlet of equipment. The connection between two devices is a part that connects the pipes to pipes and is connected to the ends of pipes. It is a subsidiary accessory product of the pipe. Forged flanges are mainly made of carbon steel, alloy steel, and stainless steel. The main standard of GB, American Standard, German standard, Japanese standard etc.. The main anticorrosive treatment is oiling and galvanizing. The forged steel flange has good pressure resistance, good temperature resistance, and is generally suitable for high pressure and high temperature working environment.

asme b16 5 a182 f316l wnrf flange 1 12 inch sch40s pn16 - How to get high quality forged flanges?

Production process
The production process is mainly divided into two kinds: forging and casting.
Production process of cast flanges
First of all we need to know how the production of centrifugal flange, centrifugal casting process for making flange and products, which is characterized in that the products through the following process steps and processing:
The selected raw material steel is melted in medium frequency electric furnace to make the temperature of molten steel reach 1600-1700.
The metal mold pre heated to 800-900 DEG C remain constant;
Starting the centrifuge, the step 1 of the steel water is injected into the step 2, the metal mold is preheated.
The casting of natural cooling to 800-900 DEG C for 1-10 minutes;
The water is cooled to near the normal temperature, and the casting is removed.
Production process of the forged flanges
The forging process is usually made up of the following procedures, that is, to select high quality billet blanking, heating, forming, and forging after cooling. The forging process includes free forging, die forging and fetal membrane forging. In production, different forging methods are selected according to the quality of the forgings and the number of production batches.
Free forging has many advantages such as low productivity, large machining allowance, but simple tool and versatility. So it is widely used for forging single piece and small batch forgings with simpler shape. Free forging equipment has air hammer, steam air hammer and hydraulic press and so on. It is suitable for small, large and large forgings. The die forging has high productivity, simple operation, and easy to realize mechanization and automation. The dimension precision of the die forgings is high, the machining allowance is small, and the distribution of the forgings is more reasonable, which can further improve the service life of the parts.
One. Free forging
Basic process: when free forging, the shape of the forgings is gradually forged by some basic deformation processes. The basic working procedures of free forging are upsetting, drawing long, punching, bending and cutting.

  • 1. upsetting and upsetting is the operation process that the original blank is forged along the axial direction, so that the height of the upsetting is reduced and the cross section increases. This process is often used for forging gear billets and other disc shaped forgings. The upsetting is divided into two kinds of upsetting and local forgings.
  • 2. drawing length is the forging process that makes the length of the blank increase and the cross section decreases. It is usually used to produce shaft parts, such as the spindle of the lathe and the connecting rod.
  • 3. punching punch forging processes out through holes or blind holes in the blank.
  • 4. a forging process that bending the blank to a certain angle or shape.
  • 5. a forging process that turns a part of the blank to a certain angle relative to the other.
  • 6. cutting head segmentation or the removal of blank forging process.

Two. Die forging
The die forging is called the model forging, and the heated blank is placed in the forging die fixed on the forging equipment.

  • 1. die forging: blanking, heating, preforging, finishing, flushing, cutting, tempering and shot peening. The common processes are upsetting, pulling, bending, punching and forming.
  • 2. common forging equipment commonly used equipment, forging die forging hot forging press, forging and friction press etc..

Generally speaking, the quality of forged flanges is better. Generally, it is produced by forging. The crystal structure is fine and the strength is high. Of course, the price is also expensive.
Whether casting flange or forged flange is a common manufacturing method of flange, see the strength requirement of components needed, if request is not high, you can also choose turning flange.
Three. Cut flanges
The plate is cut out of the flange directly on the medium plate with the internal and external diameter and thickness of the processing quantity, and then the bolt hole and the water line are processed. The flanges produced in this way are called cut flanges. The maximum diameter of such flanges is limited to the width of the medium plate.
Four. Coil flanges
The process of cutting a strip with a medium plate and then making a circle is called a roll, which is used for the production of some large flanges. After the success of the roll system, it is welded, then pressed, and then the process of water line and bolt hole.

Comparison of cast flanges and forged flanges

The shape and size of the casting blank flange accurately, small processing quantity and low cost, but the casting defects (pores. Cracks. Inclusion of casting structure); streamlined poor (if it is cut, streamlined worse) than the general casting flange forged flange; low carbon is not easy to rust, forging streamlined dense tissue. The mechanical properties, superior casting flange; forging process will also appear improper or uneven grain, grain hardening phenomenon, the cost is higher than the casting forged flange. The forgings can bear higher shear and tensile forces than the castings. The advantages of casting could have complicated shape, the cost is relatively low; forging has the advantages of uniform internal organization, there is no porosity in castings, inclusions and other harmful defects; from the production process of casting and forged flange flange between different, such as a centrifugal casting flange to flange. The centrifugal flange is a flange produced by precision casting. The casting is much thinner than the ordinary sand casting, and the quality is improved a lot. It is not easy to get loose porosity, trachoma and so on.

The characteristics of casting flange is easy to obtain the workpiece other methods is not easy to obtain complicated shape; casting flange low cost can be obtained; precision casting flange with special process, the surface without processing has ideal finish; casting steel flange forming is simple, the price is cheaper than the forged flange; but casting flange prone to defects and non dense area, ensure the quality of forged flange in strong corrosion and high pressure situations of domestic technology cannot in general.
Forged flanges are forged and shaped by forging equipment. They are generally unable to forge more complicated workpieces, requiring larger processing capacity. But the forged flange has dense structure and is not easy to appear internal defects.
Although the casting technology has made tremendous development, and the use of computer aided geometric design of fluid structure optimization design and casting process, but to achieve the 1 class or 2 class X ray /MT or PT quality acceptance standard is still extremely difficult, which are nuclear power plants, thermal power stations or in petrochemical industries the harsh environment of the required standard. Therefore, it is necessary to improve the welding. However, after welding, the overall quality and reliability of the cast flange becomes difficult to guarantee.
Some other defects in the casting flange are clear cracks and thermal tears during the solidification process due to the stress concentration caused by uneven shrinkage and the low strength of metals near melting point temperature. Low casting temperatures can cause cold scars, and the accumulation of sand grains or slag from molten metals will lead to stains. Low grade casting may also cause other defects.
The improvement of the cast flange to meet the requirements of X ray quality depends on the grinding, repair, heat treatment and repeated testing and testing of the defective parts. Even in this case, the flange seat and washer face or bump welding end may display fine line cracks that require heavy welding and machining.
The casting flange process built a fine particle structure and improved the physical properties of the metal. In the practical use of parts, a correct design can make the particle flow in the direction of the main pressure.

The flange produced by casting is accurate in shape and size, small in processing volume and low in cost, but with casting defects (pores, cracks, inclusions). The internal flow pattern of the casting is poor (if the cutting parts are of poor streamline type).
Forged steel flanges are generally less rust than cast steel flanges with low carbon content. Forging parts are streamlined, microstructure is more compact and mechanical properties are better than cast flanges.
If the forging process is unsuitable, there will be large or uneven grain, hardened cracks, and the cost of forging is higher than that of the cast flange.
The forgings can bear higher shear and tensile forces than the castings.
The advantage of the casting is that it can make a more complex shape, and the cost is low.
The advantages of the forgings are that the internal organization is uniform, and there are no harmful defects such as the pores and inclusions in the castings.
The difference between the casting flanges and the forged flanges is distinguished from the production process, such as the centrifugal flange is one of the cast flanges.
The centrifugal flange is a flange produced by precision casting. The casting is much thinner than the ordinary sand casting, and the quality is improved a lot. It is not easy to get loose porosity, trachoma and so on.
The advantages of forged flanges:
Forged flanges are less prone to rusting than the low carbon content of cast flanges. Forged flanges have a good streamline shape, a denser structure, and better mechanical properties than casting flanges. Improper forging processes can also result in large or uneven grain sizes and hard cracking. Forged flanges cost more than foundry flanges. Forged flanges can withstand higher shear and tensile forces than cast flanges. The advantage of the cast flange is that it can come up with a more complex shape, the cost is relatively low; the advantage of the forged flange is that the internal organization is uniform, there are no harmful defects such as pores, inclusions in the casting.
Why do you choose forged flanges? 
Compared with cast flange, forged flange has more uniform structure, better density, better strength integrity, better dimensional characteristics and smaller size error. The directional structure (pipeline) has a higher performance than the cast flange in the whole strength and stress.
(1) High strength
Hot forging promotes crystallization and grain refinement, allowing the material to achieve maximum possible strength and consistency, and the minimum variation between parts and parts. The flow of the particle flow is precisely along the body profile, and these continuous streamlines help to reduce the incidence of fatigue or common failures.
(2) Reliability
Forged flanges that meet the requirements of the design structure have always been one of the most important advantages of forged flanges, to some extent at the top of the above characteristics.
(3) Structural integrity
Forging eliminates internal defects and produces a coherent and consistent metallographic organization that ensures excellent performance. In places where stress and internal corrosion are serious, forged flanges can guarantee long service life and failure free service.
(4) Consistency
The dimensional consistency of closed die forging results in the complete control of the key wall thickness, avoiding the defects caused by the shifting of the core in the casting process. Through the impact of high quality, no separation steel ingot and 10 thousand to 30 thousand ton presses, it ensures the consistent metallographic structure without internal defects.

Source: China Forged Flanges Manufacturer – Yaang Pipe Industry (www.metallicsteel.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@metallicsteel.com

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References:

  • https://www.yaang.com/forged-flange-manufacturing-technology-and-requirements.html
  • https://www.yaang.com/comparison-of-forging-flange-and-casting-flange.html

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