What Is The Difference Between Gravity Casting And Sand Casting And Die Casting?

1. There are many technological methods to make metal materials into required products, such as casting, forging, extrusion, rolling, drawing, stamping, cutting, powder metallurgy, and so on. Among them, casting is the most basic and most commonly used process.

2. The molten metal is poured into a hollow mold made of high-temperature resistant materials, and the casting product with the desired shape is obtained after condensation. This is casting. The resulting product is a casting.

3. Casting can be divided into ferrous metal casting (including cast iron, cast steel) and non-ferrous metal casting (including aluminum alloy, copper alloy, zinc alloy, magnesium alloy, etc.) according to the material of the casting. Yifei Casting Foundry specializes in non-ferrous metal casting, focusing on aluminum and zinc alloy casting.

4. Casting can be divided into sand casting and metal casting according to the material of the casting mold. Yifei Precision Casting Factory is very comfortable with these two casting processes and can design and manufacture these two types of casting molds according to customer requirements.

5. Casting can also be divided into gravity casting and die 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 called pouring casting. The generalized gravity casting includes sand casting, metal casting, investment casting, lost foam casting, mud casting, and so on. The narrow meaning of gravity casting specifically refers 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). In a broad sense, pressure casting includes pressure casting and vacuum casting of die casting machines, low-pressure casting, centrifugal casting, etc. The narrow meaning of pressure casting specifically refers to the metal mold pressure casting of the die casting machine, referred to as die casting. Yifei Precision Casting Factory has long been engaged in sand casting and metal casting gravity casting. These casting processes are currently the most commonly used in non-ferrous metal casting and the lowest relative price.

6. Sand casting is a traditional casting process that uses sand as the main modeling material to make sand casting molds. Sand mold casting generally adopts gravity casting, 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, such as small parts, large parts, simple parts, complex parts, single-piece, large-scale castings, etc. The casting molds used for sand casting were mostly made of wood in the past, and are commonly called wooden molds. 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 castings have higher refractoriness than metal castings, 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 sand casting 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 and porous, the dimensional accuracy of sand casting parts is low and the surface is rough. However, Yifei precision casting factory has accumulated many years of technology, which has greatly improved the surface condition of sand castings, and the effect after shot blasting is comparable to that of metal castings.

7. Metal mold casting is a modern technology that uses heat-resistant alloy steel to make hollow casting molds for casting. Metal mold casting can be either gravity casting or die casting. The metal casting mold can be used repeatedly. Every time the molten metal is poured, a casting is obtained. The service life is very long and the production efficiency is high. Metal casting parts 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. 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 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 casting mold uses heat-resistant alloy steel, the heat-resistant ability is still limited. Metal casting is generally used in the casting of aluminum alloys, zinc alloys, and magnesium alloys. It has been seldom used in copper alloy casting, and even less used in ferrous metal casting.

8. Die casting is a metal mold pressure 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 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 alloy and magnesium alloy.  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 castings 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 die casting to form subcutaneous pores, so aluminum alloy die castings are not suitable for heat treatment. Zinc alloy die castings are not suitable for surface spraying (but painting can be done). Otherwise, when the pores inside the casting are heated for the above-mentioned treatment, they will expand due to heat and cause the casting to deform or bubbling. In addition, the machining allowance of die castings should also be smaller, generally around 0.5mm. It can not only reduce the weight of castings, reduce the amount of cutting processing to reduce costs, but also avoid penetrating the surface dense layer, exposing the subcutaneous pores, and causing the workpiece to be scrapped.