The difference between gravity casting and sand casting and die casting

Gravity casting refers to a process in which molten metal is injected 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, lost foam casting, mud casting, etc.; gravity casting in a narrow sense refers to metal casting.

There are many process methods for making metal materials into desired 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.

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

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. The precision casting factory specializes in non-ferrous metal casting, with an emphasis on aluminum and zinc alloy casting.

Casting can be divided into sand casting and metal casting according to the material of the casting mold. The precision casting factory is handy with both casting processes, and designs and manufactures these two types of casting molds by themselves.

Casting can also be divided into gravity casting and die casting according to the casting process of molten metal. Gravity casting refers to a process in which molten metal is injected 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, lost foam casting, mud casting, etc.; gravity casting in a narrow sense refers to metal casting. Die casting refers to a process in which molten metal is injected into a 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 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 are also the cheapest in relative price.

Sand casting is a traditional casting process that uses sand as the main molding material to make molds. Sand molds generally use 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, small parts, large parts, simple parts, complex parts, single parts and large batches can be used. The molds for sand casting were mostly made of wood in the past, commonly known as wood molds. In order to change the disadvantages of wood molds, such as easy deformation and damage, Xudong Precision Casting Factory changed all the sand mold castings produced by a single piece to aluminum alloy molds or resin molds with high dimensional accuracy and long service life. Although the price has increased, it is still much cheaper than the mold used for metal mold casting. In the production of small batches and large pieces, the price advantage is particularly prominent. In addition, sand molds are more refractory than metal molds, so materials with higher melting points such as copper alloys and ferrous metals are also mostly used in this process. However, sand casting also has some disadvantages: because each sand casting can only be poured once, the casting 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 the sand is soft And porous, so sand casting castings have lower dimensional accuracy and rougher surfaces. However, the precision casting factory has accumulated many years of technology accumulation, which has greatly improved the surface condition of sand castings, and the effect after shot blasting is comparable to that of metal castings.

Metal mold casting is a modern process of making hollow casting molds from heat-resistant alloy steel. Metal molds can be either gravity casting or die casting. The casting mold of the metal mold can be used repeatedly. Every time the molten metal is poured, a casting is obtained, with a long service life and high production efficiency. The casting of the metal mold not only has good dimensional accuracy and smooth surface, but also has a higher strength than the sand mold under the condition of pouring the same molten metal, and is less likely to be damaged. Therefore, in the mass production of medium and small castings of non-ferrous metals, as long as the melting point of the casting material is not too high, metal mold casting is generally preferred. However, metal mold casting also has some disadvantages: because the heat-resistant alloy steel and the processing of hollow cavities on it are relatively expensive, the mold cost of the metal mold is high, but the overall cost of the die-casting molding is lower than that of the die-casting mold. too much. For small batch production, the mold cost allocated to each product is obviously too high, which is generally not acceptable. And because the mold of 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 powerless for particularly large castings. Therefore, in the production of small batches and large pieces, metal mold casting is rarely used. In addition, although the metal mold adopts heat-resistant alloy steel, its heat resistance is still limited. Generally, it is mostly used in the casting of aluminum alloys, zinc alloys, and magnesium alloys. even less. All the metal molds of Xudong Precision Casting Factory are designed and manufactured by themselves, so they can provide customers with cheap and suitable high-quality molds in a timely manner.

Die casting is the metal mold pressure carried out on the die casting machine, and it is the casting process with the highest production efficiency at present. Die-casting machines are divided into two categories: 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 restriction of the heat resistance of the parts, it can only be used for the production of low melting point materials such as zinc alloy and magnesium alloy. . The aluminum alloy die castings that 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 air in the cavity is wrapped inside the casting to form subcutaneous pores, so the die casting alloys hould not be heat treated, and the zinc alloy die casting should not be sprayed on the surface (but it can be painted). Otherwise, the internal pores of the casting will expand due to thermal expansion and cause the casting to deform or bubble when the above-mentioned treatment is performed. In addition, the machining allowance of die castings should also be smaller, generally around 0.5mm, which can not only reduce the weight of castings, reduce the amount of cutting to reduce costs, but also avoid penetrating the surface dense layer and exposing subcutaneous pores, causing The workpiece is scrapped.