DIFFERENCE BETWEEN CASTINGS AND FORGED VALVES
2024.08.06
1. Forging
1. Forging: It is a processing method that uses forging machinery to exert pressure on metal blanks to produce plastic deformation to obtain forgings with certain mechanical properties and certain shapes and sizes.
2. One of the two major components of forging. Through forging, the loose casting state of the metal can be eliminated, and the mechanical properties of the forgings are generally better than those of the same material. Forgings are mostly used for important parts with high load and severe working conditions in machinery, except for plates, profiles or weldments that can be rolled with simple shapes.
3. The forging materials are mainly carbon steel and alloy steel of various compositions, followed by aluminum, magnesium, titanium, copper, etc. and their alloys. The raw state of the material is bar stock, ingot, metal powder and liquid metal. The ratio of the cross-sectional area of the metal before deformation to the die-level area after deformation is called the forging ratio. The correct selection of forging ratio has a lot to do with improving product quality and reducing costs.
4. Forging can be divided into (1) open forging (open forging) according to the forming method. The impact force or pressure is used to deform the metal between the upper and lower two iron (anvils) to obtain the required forgings, which are mainly manual forging and mechanical forging. (2) Closed-mode forging. The metal billet is deformed under pressure in the 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 divided into hot forging (the processing temperature is higher than the recrystallization temperature of the billet metal), warm forging (lower than the recrystallization temperature) and cold forging (room temperature).
2. Casting
1. Casting: It is the process of smelting metal into a liquid that meets certain requirements and pouring it into the casting mold, and obtaining a casting (part or blank) with a predetermined shape, size and performance after cooling and solidification and cleaning treatment. The basic process of modern machine building industry.
2. The cost of the blank produced by casting is low, and it can show its economy more for parts with complex shapes, especially those with complex cavities; At the same time, it has a wide range of adaptability and good comprehensive mechanical properties.
3. However, 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 removal machines, shot blasting machines, cast iron plates, etc.) required for casting production, and dust, harmful gases and noise will be produced to pollute the environment.
4. Casting is an early metal thermal processing technology mastered by human beings, which has a history of about 6,000 years. In 3200 BC, copper frog castings appeared in Mesopotamia. Between the 13th and 10th centuries B.C., China had entered the heyday of bronze castings, and the craftsmanship had reached a fairly high level, such as the 875-kilogram Simu Wufang Ding of the Shang Dynasty, the Zeng Hou Yizun Pan of the Warring States Period and the translucent mirror of the Western Han Dynasty are all representative products of ancient casting. The early casting was greatly influenced by pottery, and most of the castings were tools or utensils for agricultural production, religion, life, etc., with strong artistic colors. In 513 B.C., China produced the world's first recorded iron casting, the Jin Dynasty Casting Ding (about 270 kilograms). Around the 8th century AD, iron castings began to be produced in Europe. After the Industrial Revolution of the 18th century, castings entered a new era in the service of large industries. In the 20th century, the development of casting was very fast, and it has successively developed ductile iron, malleable cast iron, ultra-low carbon stainless steel, aluminum-copper, aluminum-silicon, aluminum-magnesium alloy, titanium-based, nickel-based alloys and other cast metal materials, and invented a new process for the inoculation treatment of gray cast iron. After the 50s, there were new processes such as green sand high-pressure molding, chemically hardened sand molding, core building, negative pressure molding, and other special casting, shot blasting and cleaning.
5. There are many types of casting, which are customarily divided into: (1) ordinary sand casting, including three types: green sand mold, dry sand mold and chemical hardening sand mold. (2) Special casting, according to the molding material, can be divided into two categories: special casting with natural mineral sand and gravel as the main molding material (such as investment casting, mud casting, shell casting in foundry, negative pressure casting, solid casting, ceramic casting, etc.) and special casting with metal as the main casting material (such as metal mold casting, pressure casting, continuous casting, low-pressure casting, centrifugal casting, etc.).
6. The casting process usually includes: (1) casting mold (making liquid metal a container for solid castings) preparation, casting mold can be divided into sand mold, metal type, ceramic type, mud type, graphite type according to the materials used, and can be divided into disposable type, semi-permanent type and permanent type according to the number of uses, and the advantages and disadvantages of casting preparation are the main factors affecting the quality of castings; (2) Melting and pouring of cast metals, cast metals (cast alloys) mainly include cast iron, cast steel and cast non-ferrous alloys; (3) Casting treatment and inspection, casting treatment includes removing foreign bodies on the surface of cores and castings, cutting off sprue risers, shoveling and grinding burrs and seams and other protrusions, as well as heat treatment, shaping, anti-rust treatment and rough machining. Inlet pump valve
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