Flange manufacturers use four processes to produce flanges

Thread Content

　Cast flanges and forged flanges: Flanges produced by casting have accurate dimensions of the blank, require less machining, and are cost-effective; however, they have casting defects such as pores, cracks, and inclusions； The internal microstructure of the casting has poor streamlining (and it is even worse for machined parts) ； 　　Forged flanges generally have a lower carbon content than cast flanges, which makes them less prone to rusting. They possess a better streamlined shape, a more dense microstructure, and superior mechanical properties compared to cast flanges ； 　　Improper forging processes can also result in large or uneven grains, as well as hardening cracks; furthermore, the forging cost is higher than that of cast flanges. 　　Forgings can withstand higher shear and tensile forces than castings. 　　The advantage of castings is that they allow for the creation of relatively complex shapes at a lower cost ； 　　The advantage of forgings is their uniform internal structure, free from harmful defects such as pores and inclusions found in castings ； 　　Casting flanges and forged flanges differ in terms of their production processes; for example, centrifugal flanges are a type of casting flange. 　　Centrifugal flanges are flanges produced using the precision casting method; the microstructure resulting from this casting process is much finer than that of conventional sand casting, leading to improved quality, and it is less prone to problems such as loose structure, pores, and sand inclusions. 　　First, we need to understand how centrifugal flanges are produced. The process used for manufacturing flat-weld flanges through centrifugal casting, as well as the characteristics of these products, involve the following steps: ① The selected raw material, steel, is melted in an intermediate-frequency electric furnace, until the temperature of the molten steel reaches 1600–1700℃ ； 　　②Preheat the metal mold to 800–900°C and maintain that temperature ； 　　③Start the centrifuge and pour the molten steel from step ① into the preheated metal mold in step ② ； 　　④The casting is allowed to cool naturally to 800–900°C and held at that temperature for 1–10 minutes ； 　　⑤Cool with water to near room temperature, then demold the casting. 　　Let’s take a look at the production process flow for forged flanges: The forging process generally consists of the following steps, namely selecting high-quality steel billets, heating them, shaping them, and cooling them after forging. The forging process methods include free forging, die forging, and die-casting. During production, different forging methods are selected based on the size of the forging’s mass and the volume of the production batch. 　　Free forging has low productivity and requires large machining allowances, but it uses simple tools and offers high versatility; therefore, it is widely used for forging single pieces or small batches of components with relatively simple shapes. Free forging equipment includes air hammers, steam-air hammers, and hydraulic presses, which are suitable for the production of small, medium, and large forgings respectively. Die forging has high productivity, is simple to operate, and is easy to mechanize and automate. Die-forged parts have high dimensional accuracy, require less machining allowance, and have a more rational fiber structure, which can further extend the service life of the components. 　　Basic processes of free forging: During free forging, the shape of the forged piece is achieved by gradually shaping the billet through various basic deformation processes. The basic processes of free forging include upsetting, drawing, punching, bending, and cutting. 　　1. Upsetting: Upsetting is the process of forging the original blank axially, thereby reducing its height and increasing its cross-sectional area. This process is commonly used for forging gear blanks and other disc-shaped forgings. Upsetting is divided into full upsetting and partial forging. 　　2. Lengthening: Lengthening is a forging process that increases the length of the blank while reducing its cross-section; it is typically used to produce blanks for shaft-type components, such as lathe spindles and connecting rods. 　　3. Punching: A forging process in which holes, either through-hole or blind holes, are created in the blank using a punch. 　　4. Bending: A forging process in which the blank is bent into a certain angle or shape. 　　5. Torsion: A forging process in which a part of the blank is rotated by a certain angle relative to another part. 　　6. Cutting: The forging process of splitting the blank or removing the end portion of the material. 　　Die forging Die forging, also known as model forging, involves shaping a heated billet by placing it within a die fixed to the forging equipment. 　　Basic processes of die forging: Die forging process steps include blanking, heating, pre-forging, final forging, skin punching, trimming, quenching and tempering, and shot blasting. Common processes include upsetting, drawing, bending, punching, and forming. 　　Common die forging equipment includes die forging hammers, hot die forging presses, flat forging machines, and friction presses. 　　Put simply, forged flanges have better quality; they are generally produced by die forging, resulting in a fine crystal structure and high strength, though they are also more expensive. 　　Both cast flanges and forged flanges are common manufacturing methods for flanges. Depending on the strength requirements of the component to be used, turned flanges can also be an option if the requirements are not high. 　　III. Flange Cutting A disc with the inner and outer diameters as well as the thickness required for further processing is cut directly from the middle plate; thereafter, bolt holes and water lines are fabricated. Flanges produced in this way are called cut flanges, and the maximum diameter of such flanges is limited by the width of the middle plate. 　　IV. Rolled Flanges The process of cutting strips from medium-grade steel and then rolling them into circular shapes is known as rolling; it is commonly used in the production of large flanges. After successful rolling, welding is carried out, followed by flattening, and then the processes for the waterline and bolt holes are performed.