Casting can be divided into gravity casting and pressur […]
Casting can be divided into gravity casting and pressure casting according to the pouring process of molten metal. Gravity casting refers to the process of injecting molten metal into a mould under the action of the earth's gravity, also called casting. The generalized gravity casting includes sand casting, metal casting, investment casting, lost foam casting, mud casting, etc.; gravity casting in a narrow sense refers to metal casting. Pressure casting refers to the process of injecting molten metal into the mould under the action of other external forces (excluding gravity). In a broad sense, pressure casting includes pressure casting of die casting machines, vacuum casting, low pressure casting, centrifugal casting, etc.; pressure casting in a narrow sense refers to metal die casting of die casting machines, referred to as die casting. Precision casting factory has long been engaged in the gravity casting of sand and metal moulds. These casting processes are currently the most commonly used in non-ferrous metal casting and are relatively inexpensive.
Die casting is a metal mould pressure casting performed on a die casting machine, which is currently the most efficient casting process. Die casting machines are divided into hot chamber die casting machines and cold chamber die casting machines. The hot chamber die casting machine has 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, it can only be used for the production of low melting point materials such as zinc alloys and magnesium alloys. . Aluminum alloy die castings, which are widely used today, can only be produced on cold chamber die casting machines due to their high melting point.
The main feature of die casting is that the molten metal fills the cavity under high pressure and high speed, and is formed and solidified under high pressure. The disadvantage of die casting is: because the molten metal fills the cavity under high pressure and high speed, it is inevitable The air in the cavity is wrapped in the inside of 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 painting). Otherwise, when the pores inside the casting are heated for the above treatment, they will expand due to heat and cause the casting to deform or bubble. In addition, the machining allowance of die casting parts should also be smaller, generally around 0.5mm, which can reduce the weight of the casting and reduce the amount of cutting to reduce the cost, and it can also avoid penetrating the dense layer of the surface and exposing the subcutaneous pores. The artifact is scrapped.