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The difference between casting process and die casting process
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 mold under the action of the earth's gravity, also known as casting. The generalized gravity casting includes sand casting, metal casting, investment casting, lost foam casting, mud casting, etc. The narrow gravity casting refers specifically to metal casting.
Pressure casting refers to the process of injecting molten metal into the mold under the action of other external forces (excluding gravity). Die 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 refers specifically to metal die casting of die casting machines, referred to as die casting. The precision casting factory has long been engaged in the gravity casting of sand and metal molds. These casting processes are currently the most commonly used in non-ferrous metal casting and the lowest relative price.
Die casting is a metal mold die 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 the cold chamber die casting machine. 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 forms and solidifies under high pressure. The disadvantage of die casting is: because the molten metal fills the cavity under high pressure and high speed, The air in the cavity is inevitably wrapped in the inside of the casting to form subcutaneous pores. Therefore, aluminum alloy die castings are not suitable for heat treatment, and zinc alloy die castings are not suitable for surface spraying (but paint can be sprayed). Otherwise, when the pores inside the casting are heated for the above treatment, they will expand when exposed to heat and cause the casting to be deformed or bubbling. 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. It can also avoid penetrating the dense layer of the surface and exposing the subcutaneous pores. The artifact is scrapped.