Basic knowledge of casting
Casting is a processing method in which molten metal is poured into a mold, cooled and hardened. It can be finished in the shape of a mold without applying force to the metal. It is a processing method suitable for mass production, and there are many products around us made by casting. In this series, eight times, we will explain the basic knowledge of casting that is necessary for engineers.
Casting is a processing method in which metal melted at a temperature higher than the melting point is poured into a mold that has a cavity with the same shape as the one you want to make, and then cooled and hardened. This mold is called a mold, and there are various types such as sand molds made of hardened sand, molds made of metal, and gypsum molds made of gypsum. In addition, products made by casting are called castings.
Casting and forging are often compared in terms of forming metal. In products made by forging, the cast structure of the material is destroyed by plastic deformation, and a metal flow (a state in which metal particles are aligned) is formed. It has a dense structure, no internal defects, and is stronger than castings. However, due to the large number of processing man-hours, the cost is higher than that of castings, and it is difficult to form complicated shapes. On the other hand, the biggest feature of casting is that it uses molten metal, so it has a high degree of freedom in shape. Even products with complicated shapes can be easily molded. It can also be applied to any meltable metal and can form any large casting as long as it can be molded. Mass production is also one of the features. Depending on the type of mold, one mold can produce tens of thousands of castings.
The drawback of casting is that the molten metal cools and hardens. If the volume shrinks to create cavities inside the mold, or if the molten metal hardens before pouring the molten metal into the mold, defective products may occur. Therefore, it is necessary to thoroughly control the quality of the product for defects.