What is the difference between forged steel valves and cast steel valves ？
Which is better, CNLD forged steel valve or CNLD cast steel valve?
Cast steel valves are steel used to cast castings. A type of casting alloy. Cast steel is divided into three categories: cast carbon steel, cast low-alloy steel, and cast special steel. Cast steel refers to a type of steel casting produced using casting methods. Cast steel is mainly used to manufacture parts with complex shapes, difficult forging or cutting processes, and high requirements for strength and plasticity. Forged steel refers to various forgings and forgings produced by forging methods. Forged steel parts have higher quality than cast steel parts, can withstand large impact forces, and have higher plasticity, toughness, and other mechanical properties than cast steel parts. Therefore, forged steel parts should be used for all important machine parts.
The difference between CNLD forged steel valves and CNLD cast steel valves:
Forged steel valves have better quality than cast steel valves, can withstand large impact forces, and have higher plasticity, toughness, and other mechanical properties than cast steel parts. However, the nominal diameter is relatively small, generally below DN50. The pressure rating of cast valves is relatively low, with commonly used nominal pressures being PN16, PN25, PN40150LB-900LB. Forged steel valve grades: PN100, PN160, PN320, 1500LB-3500LB, etc. Cast steel is mainly used to manufacture parts with complex shapes, difficult forging or cutting processes, and high requirements for strength and plasticity. Casting is a liquid forming process, while forging is a plastic deformation process. Forged workpieces can improve the internal structure of the organization, have good mechanical properties, and uniform grain size. Important and difficult workpieces must be forged. Casting can cause tissue segregation and defects. Of course, casting has its advantages. Forging complex shaped workpieces is not easy to open molds, so casting has been adopted.
Valve casting process:
1. Casting: It is the process of melting metal into a liquid that meets certain requirements and pouring it into a mold. After cooling, solidification, and cleaning treatment, it obtains castings (parts or blanks) with predetermined shapes, sizes, and properties. The basic process of modern mechanical manufacturing industry.
2. The cost of raw materials produced by casting is low, which can better demonstrate its economy for parts with complex shapes, especially those with complex internal cavities; At the same time, it has a wide adaptability and good comprehensive mechanical performance.
3. However, casting production requires a large amount of materials (such as metal, wood, fuel, molding materials, etc.) and equipment (such as metallurgical furnaces, sand mixers, molding machines, core making machines, sand dropping machines, shot blasting machines, cast iron plates, etc.), and can generate dust, harmful gases, and noise that pollute the environment.
4. Casting is one of the earliest metal hot working processes mastered by humans, with a history of about 6000 years. In 3200 BC, copper frog castings appeared in Mesopotamia.
Valve forging process:
1. Forging: It is a processing method that uses forging machinery to apply pressure to metal billets, causing them to undergo plastic deformation to obtain forgings with certain mechanical properties, shapes, and sizes.
2. One of the two major components of forging. Forging can eliminate the casting porosity and welding holes of metals, and the mechanical properties of forgings are generally better than those of castings of the same material. For important parts with high loads and severe working conditions in machinery, forgings are often used, except for simple shaped plates, profiles, or welded parts that can be rolled.
3. Forging can be divided into: ① Open forging (free forging) according to the forming method. There are two main methods for obtaining the desired forging: manual forging and mechanical forging, which use impact force or pressure to deform the metal between the upper and lower anvil blocks. ② Closed mode forging. The forging of metal billets obtained by compression deformation in a forging die chamber with a certain shape can be divided into forging, cold heading, rotary forging, extrusion, etc. According to the deformation temperature, forging can be divided into hot forging (processing temperature higher than the recrystallization temperature of the billet metal), warm forging (below the recrystallization temperature), and cold forging (at room temperature).
4. The forging materials mainly consist of carbon steel and alloy steel with various compositions, followed by aluminum, magnesium, titanium, copper and their alloys. The original states of materials include bars, ingots, metal powders, and liquid metals. The ratio of the cross-sectional area of a metal before deformation to the die cross-sectional area after deformation is called the forging ratio. The correct selection of forging ratio is closely related to improving product quality and reducing costs.
