Various practices and differences in the foundry industry

1. Casting can also be divided into gravity casting and pressure casting according to the pouring process of molten metal. Gravity casting refers to the process in which molten metal is poured into a mold under the influence of the earth's gravity, also called casting. Gravity casting in a broad sense includes sand casting, metal mold casting, investment casting, mud mold casting, etc. Gravity casting in a narrow sense refers specifically to metal mold casting. Pressure casting refers to a process in which molten metal is injected into a mold under the action of other external forces (excluding gravity). Pressure casting in a broad sense includes pressure casting and vacuum casting of die-casting machines, low-pressure casting, centrifugal casting, etc. Pressure casting in a narrow sense specifically refers to metal mold pressure casting of die-casting machines, referred to as die-casting. These casting processes are currently the most commonly used in non-ferrous metal casting and are also the cheapest.

2. Sand casting is a traditional casting process that uses sand as the main modeling material to make molds. Sand molds generally use gravity casting. When there are special requirements, low-pressure casting, centrifugal casting and other processes can also be used. Sand casting has a wide range of adaptability, and can be used for small parts, large parts, simple parts, complex parts, single parts, and large batches. The molds used for sand casting were mostly made of wood in the past, commonly known as wooden molds. In order to change the shortcomings of wooden molds such as easy deformation and damage, Xudong Precision Casting Factory changed all sand castings to aluminum alloy molds or resin molds with higher dimensional accuracy and longer service life, except for single-piece sand castings. Although the price has increased, it is still much cheaper than the molds used for metal mold casting. The price advantage is particularly prominent in the production of small batches and large parts. In addition, sand molds are more refractory than metal molds, so materials with higher melting points such as copper alloys and ferrous metals also often use this process. However, sand casting also has some shortcomings: because each sand mold can only be poured once, the mold will be damaged after the casting is obtained and must be reshaped, so the production efficiency of sand casting is low; and because the overall nature of sand is soft It is porous, so the dimensional accuracy of sand casting castings is low and the surface is rough. However, Xudong Precision Casting Factory has accumulated many years of technology accumulation and has greatly improved the surface condition of sand castings. Its shot blasting effect is comparable to that of metal castings.

3. Metal mold casting is a modern technology that uses heat-resistant alloy steel to make hollow casting molds for casting. Metal molds can be either gravity cast or pressure cast. The metal casting mold can be used repeatedly. Every time molten metal is poured, a casting is obtained. It has a long life and high production efficiency. Metal mold castings not only have good dimensional accuracy and smooth surfaces, but also have higher strength than sand mold castings and are less likely to be damaged when the same molten metal is poured. Therefore, when producing small and medium-sized non-ferrous metal castings in large quantities, metal mold casting is generally preferred as long as the melting point of the casting material is not too high. However, metal mold casting also has some shortcomings: because heat-resistant alloy steel and the processing of making hollow cavities on it are relatively expensive, the metal mold is expensive, but overall it is cheaper than the cost of die-casting molds. too much. For small batch production, the mold cost allocated to each product is obviously too high and generally not easy to accept. And because the metal mold is limited by the size of the mold material and the capabilities of the cavity processing equipment and casting equipment, it is unable to handle particularly large castings. Therefore, metal mold casting is rarely used in small batch and large-scale production. In addition, although the metal mold uses heat-resistant alloy steel, its heat resistance is still limited. It is generally used for the casting of aluminum alloy, zinc alloy, and magnesium alloy. It is less used in copper alloy casting and is used in ferrous metal casting. Even less. Xudong Precision Casting Factory's metal molds are all designed and manufactured by itself, so it can provide customers with cheap, suitable and high-quality molds in a more timely manner.

4. Die casting is metal mold pressure casting performed on a die-casting machine. It is currently the most productive casting process. Die casting machines are divided into two categories: hot chamber die casting machines and cold chamber die casting machines. Hot chamber die-casting machines have a high degree of automation, less material loss, and higher production efficiency than cold chamber die-casting machines. However, due to the heat resistance of the machine parts, they can currently only be used to produce castings of low-melting point materials such as zinc alloys and magnesium alloys. . Aluminum alloy die castings that are widely used today can only be produced on cold chamber die casting machines due to their high melting points. The main feature of die-casting is that the molten metal fills the mold cavity under high pressure and high speed, and is formed and solidified under high pressure. The disadvantage of die casting is that during the process of the molten metal filling the mold cavity under high pressure and high speed, it is inevitable that The air in the cavity is trapped inside the casting to form subcutaneous pores, so aluminum alloy die castings are not suitable for heat treatment, and zinc alloy die castings are not suitable for surface spraying (but they can be painted). Otherwise, when the pores inside the casting are heated during the above treatment, they will expand due to heat, causing the casting to deform or bubble. In addition, the mechanical cutting allowance of die castings should also be smaller, generally around 0.5mm, which can not only reduce the weight of the castings and reduce the amount of cutting processing to reduce costs, but also avoid penetrating the surface dense layer and exposing subcutaneous pores, causing The workpiece is scrapped. .How to distinguish these two blanks From the appearance, it is difficult for us to distinguish the blanks produced by these two processes. If you see a machined part, it's even harder to tell the difference. Therefore, we can only analyze and judge in reverse: First, die castings are generally "structural parts", while die forgings are "functional parts". "Structural parts" are opposite to "functional parts". The latter generally refers to the need to withstand impact, high temperature, pressure, strength (force), and the need for surface treatment (such as anodizing), heat treatment (solid solution strengthening), etc.