Forged valves are forged. Generally used for high-end pipelines with small diameters, typically below DN50. Of course, there are also large calibers for special purposes. Cast valves are cast valves. The pressure rating of general cast valves is relatively low, such as PN16, PN25, PN40, but there are also high-pressure valves that can reach 1500lb, 2500lb, mostly above DN50.
forging
Forging: It is a processing method that applies pressure to a metal blank through a forging press to produce plastic deformation, in order to obtain forgings with certain mechanical properties, shapes, and sizes.
One of the two major components of forging. Through forging, it is possible to eliminate metal pores and welding holes as castings, and the mechanical properties of forgings are generally better than those of castings of the same material. For important parts with heavy loads and harsh working conditions in machinery, forgings are often used in addition to rolled plates, profiles, or simply shaped welded parts.
Forging can be divided into: ※ Open forging [free forging]. There are mainly two types of forging: manual forging and mechanical forging, which use impact force or pressure to deform the metal between the upper and lower iron blocks [anvil blocks] to obtain the desired forging Closed die forging. The metal blank is deformed under pressure in the forging die hole to obtain a forging with a certain shape, which 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 steel billet metal), warm forging (below the recrystallization temperature), and cold forging (at room temperature).
The forging materials are mainly carbon steel and alloy steel with various compositions, followed by aluminum, magnesium, titanium, copper and their alloys. The original state of materials includes rods, ingots, metal powders, and liquid metals. The ratio of the cross-sectional area of the metal before deformation to the cross-sectional area of the mold after deformation is called the forging ratio. The correct selection of forging ratio is closely related to improving product quality and reducing costs.
casting
Casting: refers to the process of melting metal into a liquid that meets certain requirements and pouring it into a mold. After cooling, solidification, and cleaning, castings [parts or blanks] with predetermined shapes, sizes, and properties can be obtained. The fundamental technology of modern mechanical manufacturing industry.
The cost of raw materials produced by casting is low, and for parts with complex shapes, especially those with complex internal cavities, it can better reflect their economy; Simultaneously possessing broad adaptability and excellent comprehensive mechanical properties.
But there are many 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 it will generate dust, harmful gases, and noise, polluting the environment.
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. From the 13th century BC to the 10th century BC, China entered the heyday of bronze casting, with technology reaching a considerable level. Representative products of ancient casting include the 875kg Simu Five sided Cauldron from the Shang Dynasty, the Zunpan of Zeng Hou from the Warring States Period, and the Mingjing from the Western Han Dynasty. Early casting was heavily influenced by pottery. Castings are mostly tools or vessels for agricultural production, religion, daily life, etc., with a strong artistic color. In 513 BC, China cast the world's earliest recorded iron casting, and the Jin Dynasty cast a tripod weighing about 270 kilograms. Around the 8th century, Europe began producing cast iron parts. After the Industrial Revolution in the 18th century, castings entered a new era of serving large industries. In the 20th century, the development of casting was very rapid. Casting metal materials such as ductile iron, malleable iron, ultra-low carbon stainless steel, aluminum copper, aluminum silicon, aluminum magnesium alloy, titanium based, nickel based alloys, etc. have been successively developed, and a new process for inoculation treatment of gray cast iron has been invented. After the 1950s, new technologies such as wet sand high-pressure molding, chemical hardening sand molding, core making, negative pressure molding, and shot blasting emerged.
There are many types of casting, traditionally divided into: ※ Ordinary sand casting, including wet sand casting, dry sand casting, and chemically hardened sand casting. ※ According to the molding materials, special castings can be divided into two types: special castings with natural mineral sand and stone as the main molding materials [such as investment casting, mud casting, casting workshop shell casting, negative pressure casting, full mold casting, ceramic mold casting, etc.], and special castings with metal as the main molding material [such as metal mold casting, pressure casting, continuous casting, low-pressure casting, centrifugal casting, etc.].
The casting process generally includes: preparing a mold [a container for making solid castings from liquid metal]. Casting molds can be divided into sand molds, metal molds, ceramic molds, clay molds, graphite molds, etc. according to the materials used, and can be divided into disposable molds, semi * molds, and * molds according to the number of times they are used. The quality of mold preparation is the main factor affecting the quality of castings The melting and pouring of cast metals and cast alloys mainly include cast iron, cast steel, and cast non-ferrous alloys Casting treatment and inspection: Casting treatment includes removing foreign objects from the core and surface of the casting, removing sprues and risers, scraping burrs and burrs, as well as heat treatment, shaping, rust prevention treatment, and rough processing. The low-pressure valves used in conventional water systems are mainly cast valves, commonly known as butterfly valves and gate valves, also known as cast iron butterfly valves, cast iron gate valves, etc. Forged valves are commonly used as high-pressure ball valves and gate valves.