What is the difference between forged valves and cast valves? Why should it be divided into two types of lectures? Next, this article will explain how to distinguish between forged valves and cast valves.

Forged valves

Forged valves are forged and usually used on high-grade pipelines, with a relatively small diameter, usually below DN50.

1. Forging: It is a processing method that uses forging machinery to apply pressure on metal billets, causing them to undergo plastic deformation, in order to obtain forgings with certain mechanical properties, shapes, and sizes.
2. One of the two major components of forging. Forging can eliminate casting porosity and welding holes in metals, and the mechanical properties of forgings are generally better than those of castings of the same material. In machinery, important parts with high loads and severe working conditions are mostly made of forgings, except for simple shapes that can be rolled into plates, profiles, or welded parts.
3. Forging can be divided into: ① open forging (free forging) according to the forming method. 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 anvil blocks to obtain the required forgings Closed mode forging. The metal billet undergoes compression deformation in a forging die chamber with a certain shape to obtain forgings, which can be divided into die forging, cold heading, rotary forging, extrusion, etc. According to the deformation temperature, forging can be further divided into hot forging (processing temperature higher than the recrystallization temperature of the billet metal), warm forging (lower than the recrystallization temperature), and cold forging (at room temperature).
4. The main materials used for forging are various components of carbon steel and alloy steel, by aluminum, magnesium, titanium, copper, and their alloys. The original state of materials includes bars, ingots, metal powders, and liquid metals. The ratio of the cross-sectional area of a 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 Valves

Cast valves are valves made by casting. Generally, the pressure rating of cast valves is relatively low (such as PN16, PN25, PN40, but there are also high-pressure ones, which can reach 1500Lb, 2500Lb), and most of the diameters are above DN50. The following will provide a detailed explanation
1. 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 treatment, a casting (part or blank) with predetermined shape, size, and performance is obtained. The basic technology of modern mechanical manufacturing industry.
2. The cost of casting produced blanks is low, and for parts with complex shapes, especially those with complex inner cavities, it can better demonstrate its economy; At the same time, it has a wide adaptability and good comprehensive mechanical performance.
3. However, there are many materials and equipment required for casting production (such as metals, wood, fuel, molding materials, etc.) and equipment (such as metallurgical furnaces, sand mixers, molding machines, core making machines, sand shakers, shot blasting machines, cast iron flat plates, etc.), which can produce dust, harmful gases, and noise, polluting the environment.
4. Casting is an early metal hot working process that humans have mastered, with a history of approximately 6000 years. In 3200 BC, copper frog castings appeared in Mesopotamia. Between the 13th and 10th centuries BC, China had entered the heyday of bronze casting, and its craftsmanship had reached a considerable level. Representative products of ancient casting, such as the 875 kilogram Simu Wu Fang Ding from the Shang Dynasty, the Zun Pan of Zeng Hou Yi from the Warring States period, and the translucent mirror from the Western Han Dynasty, were all representative products. Early casting was greatly influenced by pottery, with most of the castings being tools or utensils for agricultural production, religion, and daily life, with a strong artistic color. In 513 BC, China produced the world's earliest recorded cast iron piece - the Jin Dynasty Ding (weighing approximately 270 kilograms). Around the 8th century AD, Europe began producing iron castings. After the Industrial Revolution of the 18th century, castings entered a new era of service for large industries. In the 20th century, the development speed of casting was very fast, with the development of ductile iron, malleable iron, ultra-low carbon stainless steel, as well as cast metal materials such as aluminum copper, aluminum silicon, aluminum magnesium alloys, titanium based, nickel based alloys, and the invention of new processes for inoculation treatment of gray cast iron. After the 1950s, new technologies such as wet sand high-pressure molding, chemical hardening sand molding, core making, negative pressure molding, and other special casting and shot blasting cleaning emerged.
5. There are many types of casting, which are customarily divided into: ① ordinary sand mold casting, including wet sand mold, dry sand mold, and chemically hardened sand mold. ② Special casting can be divided into two types based on the molding materials: special casting with natural mineral sand and gravel as the main molding material (such as investment casting, mud casting, shell casting in casting workshops, negative pressure casting, full mold casting, ceramic mold casting, etc.) and special casting with metal as the main molding material (such as metal mold casting, pressure casting, continuous casting, low-pressure casting, centrifugal casting, etc.).
6. The casting process usually includes: ① preparation of a mold (a container that turns liquid metal into a solid casting), which can be divided into sand mold, metal mold, ceramic mold, mud mold, graphite mold, etc. according to the materials used, and can be divided into disposable mold, semi permanent mold, and permanent mold according to the number of uses. The quality of the mold preparation is the main factor affecting the quality of the casting; ② The melting and pouring of cast metals, including cast iron, cast steel, and cast non-ferrous alloys; ③ Casting treatment and inspection, including the removal of foreign objects on the core and surface of the casting, removal of casting and riser, scraping and grinding of burrs and burrs, as well as heat treatment, shaping, rust prevention treatment, and rough machining.