Permanent mold casting

Those in the foundry industry are very familiar with the term gravity casting, but what exactly is it? Today, Kuntai News will guide you through the field of gravity casting in an easy-to-understand way.   Before discussing gravity casting, we need to start with the classification of casting processes. As we all know, everything has its category, and technological processes are no exception. There are many processes for turning metal materials into desired products, such as casting, forging, extrusion, rolling, drawing, stamping, cutting, powder metallurgy, and so on. Among them, casting can be considered one of the most basic, commonly used, and widely applied processes. Casting can also be divided into gravity casting and pressure casting based on the pouring process of molten metal. This is what we will focus on today.   Since we're going to talk about gravity casting, we first need to know what gravity casting is. Baidu Baike defines gravity casting as: "The process of injecting molten metal into a mold under the influence of Earth's gravity." In simpler terms, from a narrow perspective, it means pouring molten metal into a mold of the desired shape, allowing it to cool and solidify, and the desired product is formed. Therefore, gravity casting is also called casting. The effect of gravity is similar to an apple falling from an apple tree. Due to gravity, the molten metal fills every corner of the mold. However, if the product's structure is complex and not simply a horizontal surface, the machine needs to be tilted to allow the liquid to flow fully. Understanding gravity casting makes pressure casting easier to explain: it's the process of injecting molten metal into a mold under the influence of other external forces (here, excluding gravity).   Next, let's discuss the characteristics of gravity casting. Because gravity casting relies on Earth's gravity, it has better mechanical properties, mature solution heat treatment, higher production efficiency than sand casting, and more perfect dimensional accuracy. At this point, you might be wondering what sand casting is. Sand casting, also known as sand mold casting, is a traditional casting process that uses sand as the primary molding material to create products. A single metal mold can be used for hundreds to tens of thousands of castings; hence, it's also called permanent mold casting. Because each sand mold can only be used once, the mold is damaged after the casting is obtained, requiring remolding, resulting in lower production efficiency. Furthermore, due to the soft and porous nature of sand, sand castings have lower dimensional accuracy and rougher surfaces. This explains why gravity casting is more efficient and dimensionally more accurate than sand casting. While gravity casting has lower production efficiency, less precise appearance and dimensions compared to die casting, and is more expensive, it allows for post-treatment heat treatment to meet certain mechanical requirements. Die casting, on the other hand, cannot undergo solution treatment because the molten metal is rapidly injected into the mold without time for gas to escape. Moreover, gravity casting molds are cheaper than die casting molds. The material of the gravity casting mold is the key to the gravity casting machine. The commonly used materials are 45# steel, P20 steel or H13 steel. The service life of each material is different, but they are all in the tens of thousands.