Describe the characteristics and differences of various castings in detail
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 of injecting molten metal into a mold under the action of the earth’s gravity, also known as casting. Gravity casting in a broad sense includes sand casting, metal casting, investment casting, mud casting, etc.; gravity casting in a narrow sense 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 machine, low pressure casting, centrifugal casting, etc.; pressure casting in a narrow sense refers to metal die casting of die casting machine, referred to as die casting. Xudong 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.
2. Sand casting is a traditional casting process that uses sand as the main modeling material to make molds. Gravity casting is generally used for sand molds, and low-pressure casting, centrifugal casting and other processes can also be used when there are special requirements. Sand casting has a wide range of adaptability, small pieces, large pieces, simple pieces, complex pieces, single pieces, and large quantities can be used. The molds used for sand casting were mostly made of wood in the past, and they are commonly called wooden molds. In order to change the defects of wood molds such as easy deformation and easy damage, Xudong Precision Casting Factory changed all molds to aluminum alloy molds or resin molds with high dimensional accuracy and long service life, except for the single-piece sand castings. Although the price has increased, it is still much cheaper than the mold for metal casting. In the production of small batches and large parts, the price advantage is particularly prominent. In addition, sand molds have higher refractoriness than metal molds, so materials with higher melting points such as copper alloys and ferrous metals also use this process. However, sand casting also has some shortcomings: because each sand mold can only be poured once, the mold is 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 However, it is porous, so the dimensional accuracy of sand casting castings is lower, and the surface is rougher. However, Xudong Precision Casting Factory has accumulated many years of technology accumulation, and has greatly improved the surface condition of sand castings, and the effect after shot blasting is comparable to that of metal castings.
3. Metal mold casting is a modern technology for making hollow casting molds for casting with heat-resistant alloy steel. The metal mold can be either gravity casting or pressure casting. The metal mold can be used repeatedly. Every time the molten metal is poured, a casting is obtained. The life is very long and the production efficiency is very high. Metal castings not only have good dimensional accuracy and smooth surface, but also have higher strength than sand castings and are less likely to be damaged when the same molten metal is poured. Therefore, in the mass production of medium and small non-ferrous metal castings, as long as the melting point of the casting material is not too high, metal casting is generally preferred. 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 cost of metal molds is expensive, but the overall cost of die casting molds is cheaper. too much. For small batch production, the mold cost allocated to each product is obviously too high, which is generally not easy to accept. And because the metal mold is limited by the size of the mold material and the capacity of the cavity processing equipment and the casting equipment, it is also helpless for particularly large castings. Therefore, metal mold casting is rarely used in the production of small batches and large parts. In addition, although the metal mold adopts heat-resistant alloy steel, its heat-resistant ability is still limited. Generally, it is mostly used for casting of aluminum alloy, zinc alloy, and magnesium alloy. It has been less used in copper alloy casting, but is used for ferrous metal casting. It’s even less. The metal molds of Xudong Precision Casting Factory are all self-designed and self-manufactured, so it can provide customers with cheap and suitable high-quality molds in a more timely manner.
4. Die casting is a metal mold pressure casting performed on a die casting machine, and it 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 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, 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 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.