Casting, as one of the basic processes of the modern device manufacturing industry, can produce parts with arbitrarily complex shapes, especially parts with complex inner cavity shapes, and has strong adaptability and a wide range of material sources, which can be used to produce different types of products in various industries. Components.
Castings with different uses also have certain differences in manufacturing cost, complexity, performance, surface finish, size, precision, etc. Therefore, a variety of casting processes have also been produced.
In this article, we’ll take you through the 3 most common casting processes: sand casting for lower cost, fusion casting for higher precision, and die casting for higher efficiency.
sand casting
Sand casting is a manufacturing process that uses sand to create mold cavities. Sand is used as a refractory material that can resist molten metal. Green sand is usually implied because it has good binding properties such as sand, clay, silica and a small amount of water. Patterns made of wood or metal are used to create a good replica or model of the item to be produced, leaving the same shape in the mold cavity. The pattern is created slightly larger than the original item to shrink the molten metal as it cools.
Sand casting is often used when larger parts need to be produced, which is relatively inexpensive to produce, especially in small batches. The sand casting process provides low cost for the mold after casting, and both ferrous and non-ferrous metals can be used for casting. However, sand casting produces a rougher surface and therefore requires finishing. It also yields a lower degree of accuracy. The sand casting process is slow because the mold must be broken when the casting is removed.
advantage:
1. It is suitable for making blanks with complex shapes, especially with complex inner cavities;
2. Wide adaptability and low cost;
3. For some materials with poor plasticity, such as cast iron, sand casting is the only forming process for making their parts or blanks.
shortcoming:
1. Low strength and dimensional accuracy. Castings produced by sand casting have low strength and poor dimensional accuracy because of high porosity;
2. Poor surface finish. In sand casting, foundry sand and molding sand binder are mainly used. If the sand mold is improperly selected, it is easy to cause obvious surface texture of the internal sand mold wall, which seriously affects the surface appearance of the casting.
Investment casting
Investment casting is another metal casting process that provides a high degree of precision and dimensional results, as well as a relatively high-quality surface finish. It is capable of creating thin-walled parts with complex geometries. Like sand casting, investment casting also has the ability to cast ferrous and non-ferrous metals.
The metal casting process uses disposable wax, usually beeswax, to create a pattern or model of the casting. Put the pattern (wax) into the mold. The wax is pre-coated with a liquid refractory and dried in the sun, or heated before being placed in the mold, helping the pattern resist molten metal for a short period of time.
After the coating wax is injected into the mold, the molten metal is poured and takes place in the pattern. The pattern melts and the metal solidifies into the shape of melted wax. Investment casting is widely used in the manufacture of aerospace, automotive and military parts.
advantage:
1. High dimensional accuracy and geometric accuracy;
2. High surface roughness;
3. It can cast complex castings, and the alloys to be cast are not limited.
shortcoming:
1. complicated process and high cost
die casting
Die cast metals typically involve non-ferrous metals and alloys such as tin, zinc, aluminum and copper. Its final product offers better surface finish and good dimensional accuracy. This metal casting process is carried out by pressing molten metal into a mold under high pressure. The mold is lubricated for easy injection of molten metal. And adjust the temperature of the mold.
Molten metal is rapidly injected into the mold under high pressure. Quick insertion helps prevent part of the casting from hardening before the rest of it. After the molten metal solidifies, the casting is removed from the mold and the scrap is cut.
The die cost of die casting is relatively high, so it is more cost-effective in mass production. Blowhole defects are common in die castings when producing large items. This is because air is trapped, and because the molten metal solidifies before reaching the mold cavity.
advantage:
1.The metal liquid is subjected to high pressure and fast flow rate during die casting
2.Good product quality, stable size and good interchangeability;
3.The production efficiency is high, and the die-casting mold is used many times;
4. It is suitable for mass production and has good economic benefits.
shortcoming:
1. Castings are prone to small pores and shrinkage.
2. The plasticity of die castings is low, and it is not suitable to work under impact load and vibration;
3. When the high melting point alloy is die-casting, the life of the mold is low, which affects the expansion of die-casting production.
