The difference between forged and cast valves

The difference between forged and cast valves

2. Casting production of blanks at low cost, for the shape of complex parts, especially complex internal cavity is more economical; at the same time has a wide range of adaptability and good overall mechanical properties.

　　3. However, there are many materials (e.g., metal, wood, fuel, molding materials, etc.) and equipment (such as metallurgical furnace, sand mixer, molding machine, core making machine, sand falling machine, shot blasting machine, cast iron plate, etc.). Casting production required, will produce dust, harmful gases and noise pollution of the environment.

　　4. Casting is an early metal hot working process mastered by mankind, with a history of about 6,000 years. Copper frog castings appeared in Mesopotamia in 3200 BC. From the 13th century B.C. to the 10th century B.C., China entered the heyday of bronze casting, and the technology has reached a fairly high level. For example, the Simuwu square tripod of the Shang Dynasty, the Zenghouyi Zun disk of the Warring States period, and the transparent mirrors of the Western Han Dynasty are representative products of ancient casting. Early casting is influenced by pottery, casting most of the agricultural production, religion, life and other aspects of the tools or vessels, with a strong artistic color. In 513 BC, China cast the world's earliest recorded cast iron pieces, namely - gold tripod (about 270 kilograms). About the 8th century, Europe began to produce cast iron parts. 18th century after the industrial revolution, casting entered a new era for the service of big industry. 20th century, casting development is rapid, has developed ductile iron, malleable cast iron, ultra-low carbon stainless steel, aluminum-copper, aluminum-silicon, aluminum-magnesium alloy, titanium and nickel-based alloys, such as casting metal materials, the invention of the grey cast iron gestation treatment of the new technology. 20 century 50s, after the appearance of the After the 1950s, the emergence of wet sand high-pressure molding, chemical hardening sand molding core, negative pressure molding and other special casting and shot blasting cleaning and other new technologies.

　　5. There are many kinds of castings, customarily divided into: ordinary sand casting, including wet sand, dry sand and chemical hardening sand. According to the molding material, special casting can be divided into two categories: natural mineral sand as the main molding material for special casting (such as investment casting, mud casting, foundry shell casting, negative pressure casting, full mold casting, ceramic casting, etc.). And special castings with metal as the main molding material (such as metal type casting, pressure casting, continuous casting, low-pressure casting, centrifugal casting, etc.). .

　　6. Casting process usually includes: the preparation of casting (liquid metal into a solid casting container), can be divided into sand, metal type, ceramic type, mud type, graphite type. According to the number of uses can be divided into a one-time mold, semi-permanent molds and permanent molds, and the quality of casting preparation is the main factor affecting the quality of castings; casting metal melting and casting, casting metal (casting alloys), including cast iron, cast steel and casting non-ferrous alloys; casting treatment and inspection. Casting treatment includes the removal of foreign matter from the core and casting surface, cutting off the pouring riser, removing burrs and seams, heat treatment, molding, rust prevention and rough machining. Imported pump valve two, forging

　　1. Forging: forging machine is used to apply pressure to the metal blank, so that it undergoes plastic deformation, to obtain a certain mechanical properties, a certain shape and size of the forgings of the processing method.

　　2. One of the two main components of forging. Forging can eliminate the cast metal porosity and welding holes, the mechanical properties of forgings are generally better than the same material castings. In addition to simple rolled plates, profiles or weldments, forgings are mostly used in machinery for high loads, poor working conditions of important parts.

　　3. Forging can be divided into: open forging (free forging). Impact or pressure is used to deform the metal between the upper and lower counterweights (anvil seats) to obtain the desired forgings. There are two main types of forging: hand forging and mechanical forging. Closed die forging. Metal billet in a certain shape of the forging die chamber pressing deformation, get forging, can be divided into die forging, cold heading, rotary forging, extrusion, etc.. Forging according to the deformation temperature can be divided into hot forging (processing temperature higher than the recrystallization temperature of the blank metal), warm forging (lower than the recrystallization temperature) and cold forging (room temperature).

　　4. Forging material is mainly a variety of components of carbon and alloy steel, followed by aluminum, magnesium, titanium, copper and its alloys. The original state of the material includes bar, ingot, metal powder and liquid metal. The ratio of the cross-sectional area of the metal before deformation to the area of the broken mold after deformation is called the forging ratio. Correct choice of forging ratio and improve product quality, reduce costs have a great relationship.

　　Cast valves are valves made by casting. General casting valves are relatively low pressure level (such as PN16, PN25, PN40, but there are also high pressure, up to 1500Lb, 2500Lb), most of them are above DN50. Forged valves are forged and generally used for high grade pipelines with smaller diameter than, generally below DN50.