First, what is casting
Casting is the production method of casting melted liquid metal into a mold cavity which is suitable for the shape and size of a part and obtaining a blank or a part after cooling and solidifying.
II. Development of Foundry Industry
Casting is an ancient manufacturing method, which can be traced back to 6,000 years ago in our country, especially in the bronze age 1,000 years ago. Foundry occupies an important position in the machinery manufacturing industry and is also the most important cornerstone of social development and progress.
III. Casting Process
The overall casting process is as follows:
Mold production-mold molding and boxing-metal smelting and casting-sand cleaning-annealing-polishing-checking and warehousing.
According to different casting processes, there are differences.
Four, casting process types
Common casting methods are as follows:
1. Sand casting: Sand casting is a method of forming a casting by mixing raw sand, binder and auxiliary materials according to a certain proportion, then forming a sand shape with a model and pouring liquid metal. Sand casting is the most widely used casting method. Sand casting has a wide range of adaptability. Small, large, simple and complex pieces can be used in single piece or in large batch. Formerly, molds used for sand casting were made of wood, commonly known as wood molds. The disadvantages of wood molds are easy to deform and damage. In addition to sand castings produced in single piece, aluminum alloy molds or resin molds with larger size, higher precision and longer service life can be used. Sand mold has higher refractoriness than metal mold, so materials with higher melting points, such as copper alloy and ferrous metal, also use this process. However, sand mold casting also has some disadvantages, because each sand mold can only be cast once, the mold is damaged after obtaining the casting, and must be reshaped, so the production efficiency of sand mold casting is low, and because the overall properties of sand are soft and porous, the size precision of sand mold casting castings is low, and the surface is rough.
2. Investment casting: Investment casting is also called "lost wax casting". It is usually a method of obtaining castings by coating several layers of refractory material on the surface of wax mold, melting the wax mold to form a mold shell after it is hardened and dried, roasting, and then casting. The obtained castings are also called "investment precision casting" because they have high dimensional accuracy and surface roughness. Film-containing casting is not only suitable for casting of various types and alloys, but also can produce castings with higher dimensional accuracy and surface quality than other casting methods, and even those castings that are difficult to obtain by other casting methods and are complicated, high temperature resistant and difficult to process can be cast by investment casting.
3. Metal mold casting: Metal mold casting is also called hard mold casting. It is a casting method in which liquid metal is poured into a metal mold by gravity casting and castings are also obtained. Therefore, it is also called "gravity casting". Metal mold molds can be repeatedly used for many times. Each time molten metal is poured, a casting is obtained with long service life and high production efficiency. Metal mold castings not only have good dimensional accuracy and smooth surface, but also can be cast with the same molten metal. Its casting strength is higher than that of sand mold, and it is less likely to be damaged. Therefore, in mass production of small and medium-sized non-ferrous metal castings, as long as the melting point of the casting material is not too high, metal mold casting is generally preferred. However, metal mold casting also has some disadvantages. Because heat-resistant alloy steel and the processing of hollow cavity made on it are relatively expensive, the metal mold is expensive, and because the metal mold is limited by the size of the mold material and the capacity of cavity processing equipment and casting equipment, it is powerless for large castings.
4. Low-pressure casting: Low-pressure casting is a method in which liquid metal fills the cavity from bottom to top under the action of pressure and has formed a casting. Because the pressure used is relatively low, it is called low-pressure casting.
5. pressure casting: pressure casting is called die casting for short. it is a method to make liquid or semi-liquid metal fill the die casting cavity at a higher speed under the action of high pressure and solidify under the action of pressure to obtain the casting.
6. Centrifugal casting: Centrifugal casting is a casting method in which liquid metal is added into a rotating casting shape to fill the casting mold and solidify the casting mold under the action of centrifugal force.
7. Lost Foam Casting: Lost Foam Casting is a casting method that uses a foam vaporizing mold to mold. Before casting, the mold is not taken out and molten metal is poured directly onto the mold. The mold vaporizes at high temperature to make room for filling and molding of molten metal. It is also called solid mold casting. Due to its low cost, high precision, flexible design, cleanness, environmental protection and suitability for complex castings, EPC technology conforms to the general trend of casting technology development in the new century and has broad development prospects.
Summary: Foundry industry promotes the development of social industry. With the improvement of requirements for casting quality, casting precision, casting cost and casting automation, casting technology is developing towards precision, large-scale, high-quality, automation and clean environmental protection. In recent years, China has achieved rapid development in precision casting technology, continuous casting technology, special casting technology, casting automation and casting simulation technology.
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