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Four production processes for flanges

Four kinds of flanges

The production process of flanges is generally divided into four main types.

Relatively speaking, forged flanges are the best quality and highest price flanges with different production processes. The second is cast flanges, as well as cut flanges and coiled flanges.

Cast flange

From the production process, the difference between cast flange and forged flange is different. For example, centrifugal flange is a kind of cast flange.

Centrifugal flanges belong to the casting method to produce flanges. Compared with ordinary sand casting, the structure of this type of casting is much finer, and the quality is improved a lot. It is not easy to have problems such as loose structure, pores, and trachoma.

How to make a cast flange

First of all, we need to understand how centrifugal flanges are produced, the process method and products of centrifugal casting to make flat welded flanges, which are characterized in that the product is processed through the following process steps:

  1. Put the selected raw material steel into an intermediate frequency electric furnace for smelting, so that the molten steel temperature reaches 1600-1700°C;
  2. Preheat the metal mold to 800-900℃ to maintain a constant temperature;
  3. Start the centrifuge, and pour the molten steel in step ① into the preheated metal mold in step ②;
  4. The casting is naturally cooled to 800-900℃ and kept for 1-10 minutes;
  5. Cool with water to near normal temperature, demould and take out the casting

Forged flange

Let us understand the production process of forged flanges:

The forging process generally consists of the following procedures, namely, selecting the blank, heating, forming, and cooling after forging.

The forging process methods include free forging, die forging and membrane forging.

During production, choose different forging methods according to the quality of forgings and the number of production batches.

Free forging has low productivity and large machining allowance, but the tools are simple and versatile, so it is widely used for forging single-piece and small-batch forgings with simpler shapes.
Free forging equipment includes air hammer, steam-air hammer and hydraulic press, etc., which are respectively suitable for the production of small, medium and large forgings.

Die forging has high productivity, simple operation, and easy realization of mechanization and automation.
The die forgings have high dimensional accuracy, small machining allowances, and more reasonable fiber structure distribution of the forgings, which can further improve the service life of the parts.

Free forging

The basic process of free forging: In free forging, the shape of the forging is gradually forged from the blank through some basic deformation processes.
The basic processes of free forging include upsetting, drawing, punching, bending and cutting.


Upsetting is the process of forging the original blank in the axial direction to reduce its height and increase its cross-section. This process is often used for forging gear blanks and other disc-shaped forgings. Upsetting is divided into two types: total upsetting and partial upsetting.

Stretch out

Pulling is a forging process that increases the length of the blank and reduces the cross-section. It is usually used to produce blanks for shafts, such as lathe spindles and connecting rods.


A forging process in which through holes or non-through holes are punched out on the blank with a punch.


A forging process in which a blank is bent into a certain angle or shape.


A forging process in which one part of the blank is rotated by a certain angle relative to the other part.


The forging process of splitting the blank or cutting off the material head.

Die forging

The full name of die forging is model forging, which is formed by placing the heated blank in a forging die fixed on the die forging equipment.

The basic process of die forging: die forging process: blanking, heating, pre-forging, final forging, punching and connecting, trimming, quenching and tempering, shot peening. Commonly used processes include upsetting, drawing, bending, punching, and forming.

Commonly used die forging equipment Commonly used die forging equipment includes die forging hammers, hot die forging presses, flat forging machines and friction presses.


In layman’s terms, forged flanges are of better quality and are generally produced by die forging, with fine crystal structure and high strength, and of course the price is more expensive.

Both cast flanges and forged flanges are commonly used manufacturing methods for flanges, depending on the strength requirements of the parts to be used. If the requirements are not high, you can also use turned flanges.

Forged flange VS cast flange

  • The cast flange has accurate shape and size, small processing volume and low cost, but has casting defects (pores, cracks, inclusions); the internal structure of the casting is poor in streamline (if it is a cutting part, the streamline is worse);
  • Forged flanges generally have lower carbon content than cast flanges and are not easy to rust. Forgings are streamlined, have a denser structure, and have better mechanical properties than cast flanges;
  • Improper forging process will also cause large or uneven crystal grains, hardening cracks, and forging costs higher than cast flanges.
  • Forgings can withstand higher shear and tensile forces than castings.
  • The advantage of castings is that they can produce more complex shapes and lower costs;
  • The advantage of forgings is that the internal structure is uniform, and there are no harmful defects such as pores and inclusions in the casting;

Cut flange

Directly cut the flange with the inner and outer diameter and thickness of the flange on the middle plate, and then process the bolt holes and waterline. The flange produced in this way is called a cut flange, and the large diameter of this type of flange is limited by the width of the middle plate.

Rolled flange

Rolled flanges are all rolled large-diameter flanges.

The process of dividing the middle plate and then rolling it into a circle is called rolling, which is mostly used in the production of some large flanges. After the rolling is successful, welding is performed, then flattened, and then horizontal lines and bolt holes are processed.

(The flange rolled by the BIT profile bending machine is very flat and hardly needs to be flattened)

Manufacturing method of rolled flange

  • Rolled flanges are cut from medium-sized steel plates into steel strips, then rolled into circular welded joints and then processed by flattening. There are cold rolling and hot rolling.
  • After processing into a circle, the water line, bolt hole, spigot and other processes are processed.
  • This is generally a large flange, which can be up to 7 meters in one molding.
  • Plate-type flat welding flanges are mostly used, and the connection method is welding.
  • If the production process of segmented production is used, the specifications of 12 meters to 15 meters or larger can be achieved.
  • This kind of flange has good quality assurance because the raw material is medium-sized steel plate with good density.

Points to note for rolled flanges

  • The welding process at the interface of the rolled flange is the most important thing, and X-ray or ultrasonic film inspection should be done. After the interface is completed, the material of the entire flange is no problem.
  • Relatively speaking, the price of processed products with thin thickness, light weight, narrow one side of the product, and some sealing grooves is higher, while the price of some thick, heavy, and no very cumbersome processing technology rolled flanges. It should be lower.
  • When processing the bolt holes, it is not allowed to drill the bolt holes to the place where there are welds. The materials of this kind of flanges are carbon steel, stainless steel, alloy steel and so on.

Photos of flange bending machine