Forgings and castings

Castings: are formed by pouring molten metal into a pre-made mold cavity and then allowing it to cool； It is suitable for large-scale production to reduce the cost of molds. Forgings are produced by direct forging of the raw material, resulting in a finer microstructure; compared to castings, they possess superior overall mechanical properties. Castings have good compressive strength and are mainly used for box-type components. Forgings are used for shafts, sleeves, etc.; compared to castings, forgings are more expensive. Casting has its drawbacks; during the casting process, defects such as sand holes and pores are likely to form. Forges generally have better quality. In terms of mechanical properties, forgings exhibit superior mechanical characteristics compared to castings, and shafts that are subject to stress are usually forged ； Casting can produce large and complex parts, which forging cannot match; forging dies are much more expensive! The advantage of casting is that it enables the production of parts with complex shapes that are difficult to achieve using other methods ； Low casting cost ； Precision castings can be produced using special processes, achieving an ideal surface finish without any further processing ； Castings are easy to shape and cheaper than forged products ； However, castings are prone to defects and non-dense areas, and domestic technology generally cannot ensure quality in environments with high corrosion and pressure. Forged parts are produced by using forging equipment to shape rod materials; it is usually not possible to forge very complex components, and a significant amount of processing is required. Yet, forged parts have a denser structural organization and are less likely to develop internal defects, which is why they are widely used in the production of components with high performance requirements, such as valve seats, valve cores, and valve stems. In alloy valves that operate under high pressure and in highly corrosive environments, forged valve bodies are also extensively utilized. Method of differentiation: Forged parts produce a clear sound when struck, while cast parts emit a somewhat muffled sound. Forged parts usually refer to steel components; wrought iron can also be used in forging, but this is rare. The grain structure in forged parts is continuous, whereas it is not so in cast parts. The surface of cast parts is rough, with patterns typical of metal machining on their processed surfaces, and pores may sometimes be present. The surface of forged parts is smooth, with a uniform texture and well-defined edges, giving them a three-dimensional appearance. In terms of cost, parts that do not have an internal structure are generally not manufactured using casting methods.

It was clearly explained on the second floor: this is why, when selecting conventional equipment, owners always require that valves be made of forged steel.