1.Cast and Forged Flanges
For the cast flange, the shape and size of the blank are accurate, the processing amount is small, and the cost is low, but there are casting defects (pores, cracks, inclusions); the internal structure of the casting is poorly streamlined (if it is a cutting part, the streamlined form is even worse);
Forged flanges generally have lower carbon content than cast flanges and are not easy to rust. Forgings have better-streamlined shapes, denser structures, and better mechanical properties than cast flanges;
An improper forging process will also cause large or uneven crystal grains, and hardening cracks and the cost of forging is higher than that of casting flanges.
Forgings can withstand higher shear and tensile forces than castings.
The advantage of castings is that they can produce more complicated shapes and the cost is relatively low;
The advantage of forgings is that the internal structure is uniform, and there are no harmful defects such as air holes and inclusions in castings;
The difference between the cast flange and the forged flange is distinguished from the production process. For example, the centrifugal flange is a kind of cast flange.
Centrifugal flange belongs to the flange produced by the precision casting method. Compared with ordinary sand casting, the structure of this type of casting is much thinner, the quality is much improved, and problems such as loose structure, pores, and trachoma are not easy to occur.
First of all, we need to understand how centrifugal flanges are produced, the process and products of centrifugal casting flat welding flanges, which are characterized in that the products are processed through the following process steps:
①Put the selected raw material steel into an intermediate frequency electric furnace for smelting, so that the temperature of the molten steel reaches 1600-1700°C;
② Preheat the metal mold to 800-900°C to maintain a constant temperature;
③Start the centrifuge, inject the molten steel in step ① into the preheated metal mold in step ②;
④The casting is naturally cooled to 800-900°C for 1-10 minutes;
⑤ Cool with water to close to room temperature, demold and take out the casting.
Let’s understand the production process of forged flanges again:
The forging process generally consists of the following processes, namely, selecting high-quality billets for blanking, heating, forming, and cooling after forging. Forging methods include free forging, die forging and membrane forging. During production, different forging methods are selected according to the quality of forgings and the number of production batches.
Free forging has low productivity and a large machining allowance, but the tools are simple and versatile, so it is widely used for forging single-piece and small-batch forgings with relatively simple shapes. Free forging equipment includes air hammer, steam-air hammer and hydraulic press, etc., which are suitable for the production of small, medium and large forgings. Die forging has high productivity, simple operation, and easy mechanization and automation. Die forgings have high dimensional accuracy, small machining allowances, and more reasonable fiber structure distribution of forgings, which can further increase the service life of parts.
The basic process of free forging: during 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.
1. Upsetting Upsetting is the operation process of forging the original billet 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 forging.
2. Elongation Elongation 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.
3. Punching is the forging process of punching through holes or non-through holes on the blank with a punch.
4. Bending A forging process that bends the billet into a certain angle or shape.
5. Twisting A forging process in which one part of the blank is rotated at a certain angle relative to the other.
6. Cutting The forging process of dividing the billet or cutting off the head.
2.Die forging
The full name of die forging is model forging, which is formed by placing the heated blank in the forging die fixed on the die forging equipment.
The basic process of die forging process: blanking, heating, pre-forging, final forging, punching and skinning, edge trimming, quenching and tempering, shot peening. Common processes include upsetting, drawing, bending, punching and forming.
Commonly used die forging equipment includes die forging hammer, hot die forging press, flat forging machine and friction press, etc.
In layman’s terms, forged flanges are of better quality and are generally produced by die forging. They have a finer crystal structure and higher strength, but of course they are more expensive.
Both cast flanges and forged flanges are commonly used flange manufacturing methods, depending on the strength requirements of the parts to be used. If the requirements are not high, turning flanges can also be used.
3. Cutting the flange
On the middle plate, directly cut out the disc with the inner and outer diameter and thickness of the flange, and then process the bolt holes and waterline. The flange produced in this way is called a cut flange, and the maximum diameter of this type of flange is limited to the width of the middle plate.
4. Coiled flange
The process of cutting strips with middle plates and rolling them into circles is called rolling, and is mostly used in the production of some large flanges. After the rolling is successful, it is welded, then flattened, and then the waterline and bolt holes are processed.
