Flange manufacturing processes are mainly divided into four types: forging, casting, cutting, and rolling. I. Cast flanges and forged flanges Cast flanges have accurate blank shape and size, small machining volume, and low cost, but they have casting defects (pores, cracks, inclusions); the internal structure of the casting has poor streamline (if it is a cutting part, the streamline is even worse);
　　Forged flanges generally have lower carbon content than cast flanges and are less prone to rust. Forgings have good streamline and dense structure, and their mechanical properties are superior to cast flanges; improper forging processes can also cause large or uneven grains and hardening cracks. The cost of forging is higher than that of casting. Forgings can withstand higher shear and tensile forces than castings. The advantage of castings is that they can produce more complex shapes at a lower cost; the advantage of forgings is that the internal structure is uniform, and there are no pores, inclusions, and other harmful defects found in castings; From the difference in the production process flow, cast flanges and forged flanges are distinguished. For example, centrifugal flanges belong to a type of cast flange. Centrifugal flanges are produced by precision casting. This type of casting has a much finer structure than ordinary sand casting, and the quality is significantly improved, and problems such as loose structure, pores, and sand holes are less likely to occur. First, we need to understand how centrifugal flanges are produced and manufactured. The process and product of centrifugal casting for producing flat welding flanges are characterized by the following process steps: ① Put the selected raw material steel into a medium-frequency induction furnace for melting, and the steel temperature reaches 1600-1700℃; ② Preheat the metal mold to 800-900℃ and keep it at a constant temperature; ③ Start the centrifuge and inject the molten steel from 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 room temperature, demold and remove the casting.
　　Let's learn about the production process of forged flanges: The forging process generally consists of the following steps: selecting high-quality steel billets, cutting, heating, forming, and post-forging cooling. Forging methods include free forging, die forging, and ring rolling. During production, different forging methods are selected according to the size of the forging mass and the number of batches.
Free forging has low productivity and large machining allowance, but the tools are simple and versatile, so it is widely used in forging simple single-piece and small-batch forgings. Free forging equipment includes air hammers, steam-air hammers, and hydraulic presses, which are suitable for small, medium, and large forgings, respectively.

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

Basic procedures of free forging: In free forging, the shape of the forging is gradually formed by some basic deformation procedures. The basic procedures of free forging include upsetting, drawing, punching, bending, and cutting. 1. Upsetting Upsetting is the process of forging the original billet along the axial direction to reduce its height and increase its cross-sectional area. This process is often used to forge gear blanks and other disc-shaped forgings. Upsetting is divided into full upsetting and partial upsetting. 2. Drawing Drawing is a forging process that increases the length of the billet and reduces the cross-sectional area. It is usually used to produce shaft-type blanks, such as lathe spindles and connecting rods. 3. Punching A forging process that punches through holes or blind holes in the billet. 4. Bending A forging process that bends the billet to a certain angle or shape. 5. Twisting A forging process that rotates part of the billet relative to another part by a certain angle. 6. Cutting A forging process that divides the billet or cuts off the head.

Die forging, also known as model forging, is the process of forging a heated billet into shape in a die fixed on die forging equipment. 1. Basic procedures of die forging Die forging process: cutting, heating, pre-forging, final forging, trimming, cutting edges, tempering, shot peening. Common processes include upsetting, drawing, bending, punching, and forming. 2. Common die forging equipment Common die forging equipment includes die forging hammers, hot die forging presses, flat forging machines, and friction presses. In simple terms, forged flanges are of better quality, generally produced by die forging, with fine crystal structure and high strength, but of course, the price is also higher.

Both cast flanges and forged flanges are common manufacturing methods for flanges. Depending on the strength requirements of the parts to be used, if the requirements are not high, turning flanges can also be selected.

Cut flanges. A disc with the inner and outer diameters and thickness of the flange with machining allowance is directly cut from the plate, and then the bolt holes and water lines are processed. The flange produced in this way is called a cut flange, and the diameter of this type of flange is limited by the width of the plate.

Rolled flanges. The process of cutting strips from a plate and then rolling them into a circle is called rolling, which is often used in the production of some large flanges. After successful rolling, welding is performed, then flattened, and then the water line and bolt hole processing are performed.