Four production processes of flanges

Flange production process mainly includes forging, casting, cutting and rolling:
Casting is a method of casting liquid metal into a casting cavity which is suitable for the shape of the flange. After it is cooled and solidified, the blank of the flange can be obtained most of the cast materials are originally solid but heated to liquid metal (e.g. copper, iron, aluminum, tin, stainless steel, etc.), while the mold materials can be sand, metal or even ceramics.
Forged flange is one of the products with the best mechanical properties in flange products. Its raw material is generally tube blank, and then it is cut and hammered continuously to eliminate segregation, looseness and other defects in ingot. The price and mechanical properties are one grade higher than the common cast flange. Flange is the part that connects the pipe with the pipe and the valve, and is connected to the pipe end; it is also useful for the flange on the inlet and outlet of the equipment, and is used for the connection between the two equipment, which is the part that connects the pipe with the pipe, and is connected to the pipe end. It is a kind of accessory product of pipeline. The main materials of forged flange are carbon steel, alloy steel and stainless steel. The main standards are national standard, electric standard, American Standard, German standard, Japanese standard, etc. The main anti-corrosion treatment includes oiling and galvanizing. Forged flange has good pressure and temperature resistance, which is generally suitable for high pressure and high temperature working environment.
The inner and outer diameter and thickness of the flange are directly cut out on the steel plate, and then the bolt hole and water line are processed. The flange produced in this way is called cut flange. The maximum diameter of such flange is limited to the width of steel plate.
The rolling flange is made by cutting the middle plate into battens, then rolling it into circular welded joints, and then flattening it. Coiling can be divided into cold coiling and hot coiling. After machining into a circle, the water line, bolt hole, stop and other processes shall be processed. This is generally a large flange, one-time molding can be up to 7 meters. Plate type flat welding flange is the most common, and the connection mode is welding. If the production process of segmented production is used, the specification of 12m-15m or larger can be achieved. This kind of flange has good quality assurance. Because the raw material is medium plate with good density. The welding process at the joint of the rolling flange is the most important, and X-ray or ultrasonic film detection shall be carried out. If the joint is finished, there will be no problem with the material of the whole flange. Relatively speaking, the price of the products with thin thickness, light weight, narrow one side of the products, and some processing with sealing grooves is higher, while the price of some rolling flanges with thick, heavy weight and without very complicated processing technology is lower. When processing bolt holes, it is not allowed to drill the bolt holes to the places with welded joints. This kind of flange is made of carbon steel, stainless steel, alloy steel, etc.


(1) Production process of cast flange and forged flange

Production process of casting flange:

  • ① put the selected raw material steel into medium frequency electric furnace for smelting, so that the temperature of molten steel can reach 1600-1700 ℃;
  • ② preheat the metal mould to 800-900 ℃ and keep constant temperature;
  • ③ start the centrifuge, inject the steel water in step ① into the metal mold after preheating 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.

Let’s learn about the production process of forged flange:

The forging process is generally composed of the following processes: blanking, heating, forming and cooling after forging. The forging process includes free forging, die forging and die forging. In production, different forging methods are selected according to the forging quality and production batch.

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Free forging has low productivity and large machining allowance, but the tool is simple and versatile, so it is widely used to forge single piece and small batch forgings with simple shape. The free forging equipment includes air hammer, steam air hammer and hydraulic press, which are suitable for the production of small, medium and large forgings respectively. Die forging has the advantages of high productivity, simple operation, mechanization and automation. Die forgings have high dimensional accuracy, small machining allowance and more reasonable fiber structure distribution, which can further improve the service life of parts.
Basic process of free forging: during free forging, the shape of forgings is gradually forged into blanks through some basic deformation processes. The basic process of free forging includes upsetting, drawing, punching, bending and cutting.

  • 1. Upsetting and upsetting is the process of forging the original billet along the axial direction to reduce its height and increase its cross section. This process is often used to forge gear blanks and other disc forgings. Upsetting can be divided into full upsetting and partial upsetting.
  • 2. Drawing length is a forging process that increases the length of the blank and reduces the cross-section. It is usually used to produce shaft parts, such as lathe spindle, connecting rod, etc.
  • 3. Forging process of punching through hole or through hole on blank with punch.
  • 4. Forging process of bending the blank to a certain angle or shape.
  • 5. The forging process in which one part of the billet rotates at an angle to the other.
  • 6. Forging process of cutting split blank or cutting head.

(2) Die forging

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

  • 1. Basic process of die forging process: blanking, heating, pre forging, final forging, punching and connecting skin, trimming, tempering and shot peening. Common processes include upsetting, drawing, bending, punching and forming.
  • 2. Common die forging equipment: die forging hammer, hot die forging press, flat forging machine, friction press, etc.

Generally speaking, the quality of forged flange is better. Generally, it is produced by die forging, with fine crystal structure, high strength and high price.

  • Both cast flange and forged flange are common manufacturing methods of flange. According to the strength requirements of components to be used, if the requirements are not high, turning flange can also be selected.
  • The shape and size of the casting blank are accurate, the machining amount is small and the cost is low, but there are casting defects (porosity, crack and inclusion); the internal structure streamline of the casting is poor (if it is a cutting part, the streamline is worse);
  • Forged flange is generally lower carbon content than cast flange and is not easy to rust. The forging has good streamline, compact structure and better mechanical properties than cast flange;
  • If the forging process is not proper, there will be large or uneven grains, hardening cracks, and the forging cost is higher than that of casting flange.
  • Forgings can bear higher shear force and tensile force than castings.
  • The advantages of casting are that it can produce more complex shape and lower cost;
  • The forging has the advantages of uniform internal structure and no harmful defects such as pores and inclusions in the casting;
  • The density of forged flange is higher than that of cast flange. That is to say, the quality of forging is better than that of casting.

(3) Cutting flange

1574892593466806 - Four production processes of flanges

The inner and outer diameter and thickness of the flange are directly cut out on the middle plate, and then the bolt hole and water line are processed. The flange produced in this way is called cut flange. The maximum diameter of such flange is limited to the width of the middle plate.

(4) Rolled flange

The process of using the middle plate to cut the sliver and then roll it into a circle is called rolling, which is mostly used in the production of some large flanges. After coiling, welding, flattening and processing of waterline and bolt hole are carried out.

How to distinguish the advantages and disadvantages of forged flange?

Flange forging is a common method. As a common processing method, forging plays a very important role in our industrial production. Many people don’t know it very well, but forging products in our life are very common. Ring forging is widely used in people’s life. It is very important to distinguish the forging flange’s merits and demerits. Next, I will introduce the judgment method to you Experienced people can judge the quality and performance of forged flange only by observing it. For the observation of forged flange, generally speaking, if the first feeling of a forged flange product is that the surface of the product is very smooth, then such a product can basically be judged as a relatively qualified product In addition, in addition to feeling, it is also important to observe the bolts of forged flange. This is mainly to see the chamfering of the bolt and the position of the bolt hole from the flange edge. The quality of bolt chamfer is directly related to the responsibility of forging flange manufacturer. The location of the bolt hole from the edge of the forged flange also has certain attention. If the forging flange is relatively close, its forged flange products must be non-standard. For professional forging flange manufacturers, the product quality and reputation is very important for the enterprise, so for the better development of the enterprise, the quality and safety of forging flange will be strictly controlled. In fact, it is not difficult to distinguish the quality of forged flange. As long as you master the correct methods and learn some experience skills, you can easily identify and find forged flange products with good quality, excellent performance and low price.

Source: China Flange Manufacturer – Yaang Pipe Industry (

(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.)

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