Difference between gravity casting and sand casting and die casting

Sand casting, as its name implies, uses sand mold as the basic mold to form the required castings after pouring metal solution. At present, iron, steel, and many non-ferrous metals can be obtained by this method. Its advantages are the low material price, easy access, strong adaptability, and wide range of use. It can be realized either in a single piece or in mass production.

Metal die casting, is also known as hard mold casting. Different from sand casting, it uses metal mold, which can be used hundreds of times. However, it has some limitations, such as casting weight, shape, and thickness.

The following are the specific advantages and disadvantages of a metal die casting and sand casting

1. Advantages:

(1) The mechanical properties of castings produced by metal mold are higher than those of sand mold castings. In the same alloy, the average tensile strength can be increased by 25%, the average yield strength can be increased by about 20%, and its corrosion resistance and hardness can also be significantly improved;

(2) The precision and surface finish of castings are higher than those of sand castings, and the quality and size are stable;

(3) The process yield of castings is high, and the consumption of the liquid metal is reduced, which can generally save 15 ~ 30%;

(4) No sand or less sand can generally save 80 ~ 100% of molding materials; In addition, the production efficiency of metal mold casting is high; Reduce the causes of casting defects; The process is simple and easy to realize mechanization and automation.

2. Insufficient:

(1) High manufacturing cost of metal mold;

(2) The metal mold is airtight and has no concession, which is easy to cause defects such as insufficient washing, cracking, or daylighting of cast iron castings;

(3) In metal mold casting, the working temperature of the mold, the pouring temperature and pouring speed of the alloy, the residence time of the casting in the mold, and the coating used are very sensitive to the quality of the casting and need to be strictly controlled.

Gravity casting refers to the process of injecting molten metal into the 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 mold 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 commonly used process.

2. The molten metal is injected into the hollow mold made of high-temperature resistant materials, and the product with the expected shape is obtained after condensation, which is casting. The resulting product is casting.

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

4. Casting can be divided into sand mold casting and metal mold casting according to the materials of mold. Precision casting factories are skilled in these two kinds of casting processes, and design and manufacture these two kinds of casting molds by themselves.

5. Casting can also be divided into gravity casting and die casting according to the pouring process of liquid metal. Gravity casting refers to the process of injecting molten metal into the mold under the action of the earth's gravity, also known as casting. In a broad sense, gravity casting includes sand mold casting, metal mold casting, investment casting, lost foam casting, mud mold casting, etc; Gravity casting in a narrow sense refers to metal mold casting. Pressure casting refers to the process of injecting molten metal into the mold under the action of other external forces (excluding gravity).

Pressure casting in a broad sense includes pressure casting, vacuum casting, low-pressure casting, centrifugal casting, etc; Narrow sense of pressure casting refers to the metal mold pressure casting of pressure casting machines, which is referred to as die casting for short. Precision casting factory has long been engaged in gravity casting of sand mold and metal mold. These casting processes are the most commonly used and the lowest relative price in nonferrous metal casting.

6. Sand casting is a traditional casting process that takes sand as the main molding material to make a mold. Gravity casting is generally adopted for sand mold, and low-pressure casting, centrifugal casting, and other processes can also be adopted when there are special requirements. Sand casting has a wide range of adaptability, including small and large parts, simple and complex parts, single parts, and large quantities. The mold used for sand casting was usually made of wood, which is commonly known as wood mold. In order to change the disadvantages of easy deformation and damage of wood molds, the Xudong precision casting factory has changed all-aluminum alloy molds or resin molds with high dimensional accuracy and long service life, except the sand castings produced by a single piece. Although the price has increased, it is still much cheaper than the mold used for metal mold casting. The price advantage is particularly prominent in small-batch and large-scale production. In addition, sand mold has higher fire resistance than metal mold, so this process is also used for materials with high melting points, such as copper alloy and ferrous metal.

However, sand casting also has some shortcomings: because each sand mold can only be poured once, the mold is damaged after obtaining the casting and must be reshaped, so the production efficiency of sand casting is low; Because the overall nature of sand is soft and porous, the dimensional accuracy of sand casting is low and the surface is rough. However, with years of technical accumulation, the precision casting factory has greatly improved the surface condition of sand castings, and its effect after shot blasting is comparable to that of metal castings.

7. Metal mold casting is a modern technology of making the hollow mold for casting with heat-resistant alloy steel. The metal mold can be either gravity casting or die casting. The mold of metal mold can be used repeatedly. Each time the liquid metal is poured, a casting can be obtained. The service life is very long and the production efficiency is very high. The casting of metal mold not only has good dimensional accuracy and smooth surface but also has higher strength and less damage than that of sand mold when pouring the same liquid metal.

Therefore, in the mass production of medium and small castings of non-ferrous metals, metal mold casting is generally preferred as long as the melting point of the casting material is not too high. However, metal mold casting also has some shortcomings: because the processing of heat-resistant alloy steel and hollow cavity on it is more expensive, the cost of metal mold is not cheap, but it is much cheaper compared with the cost of the die-casting mold. 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 mold of metal mold is limited by the size of mold material and the capacity of cavity processing equipment and casting equipment, it is powerless to do anything for particularly large castings.

Therefore, metal mold casting is rarely used in small batch and large piece production. In addition, although the metal mold adopts heat-resistant alloy steel, its heat-resistant ability is still limited. It is generally used for the casting of aluminum alloy, zinc alloy, and magnesium alloy. It has been less used in copper alloy casting, and less used in ferrous metal casting. The metal mold of the Xudong precision casting factory is designed and manufactured by ourselves, so it can provide customers with cheap and applicable high-quality molds in a more timely manner.

8. Die casting is the metal mold pressure carried out on the die casting machine. It is the casting process with the highest production efficiency at present. 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, restricted by the heat resistance of the parts, it can only be used for the casting production of low melting point materials such as zinc alloy and magnesium alloy.

Nowadays, aluminum alloy dies castings widely used can only be produced on cold chamber die casting machines because of their high melting point. The main feature of die-casting is that the liquid metal fills the cavity under high pressure and high speed, and forms and solidifies under high pressure. The disadvantage of die-casting parts is that during the process of filling the cavity under high pressure and high speed, the air in the cavity is inevitably clamped inside the casting to form subcutaneous pores, so aluminum alloy die-casting parts are not suitable for heat treatment, The surface of zinc alloy die castings should not be sprayed with plastic (but can be painted). Otherwise, when the pores inside the casting are heated by the above treatment, they will encounter thermal expansion and cause deformation or bubbling of the casting. In addition, the machining allowance of die-casting parts should also be small, generally, about 0.5mm, which can not only reduce the weight of castings and cutting amount to reduce costs but also avoid penetrating the dense layer on the surface and exposing subcutaneous pores, resulting in scrapping of workpieces.

ZheJiang Dongrun Casting Industry Co, Ltd was built in 1995, We have been in the casting industry for more than 25 years. No matter what type of molding you need to be done, we are the right supplier for your jobs. Unlike other of our competition, we offer 4 types of castings.

❖Sand casting
❖Gravity Die Casting
❖High pressure Die casting
❖Low-pressure casting