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Precision casting

  • Author:Michelle
  • Source:www.xy-global.com
  • Release on:2018-07-12
  Precision castingRefers to the general term for the process of obtaining precision-sized castings. Compared with the traditional sand casting process, the castings obtained by precision casting have more precise dimensions and better surface finish. It includes: investment casting, ceramic casting, metal casting, pressure casting, lost foam casting.
  Precision casting is also called lost wax casting. Its products are precise, complex and close to the final shape of the parts. They can be used directly without machining or processing. It is an advanced process of near net formation.

basic concept

  It includes: investment casting, ceramic casting, metal casting, pressure casting, lost foam casting.
  The most commonly used is investment casting, also known as lost wax casting: the selection of suitable investment materials (such as paraffin) to make the investment mold; repeated refractory coating and refractory sand process on the investment mold, hardened shell and dry; Dissolving the internal melting mold to obtain a cavity; calcining the shell to obtain sufficient strength, and burning off the residual investment material; pouring the required metal material; solidifying and cooling, removing sand after shelling, thereby obtaining high Precision finished product. Heat treatment and cold working and surface treatment according to product requirements.


  A casting method for producing a casting by using a ceramic slurry. The ceramic slurry is composed of a mixture of ethyl silicate hydrolyzate and fine refractory sand with relatively pure texture and high thermal stability such as fused silica, zircon, corundum and the like. In order to gel the ceramic slurry in a short time, calcium hydroxide or magnesium oxide is often added as a catalyst. Since the refractory composition used and its appearance are similar to those of ceramics, it is called a ceramic type. Ceramic casting is a new process developed on the basis of ordinary sand casting. There are two types of ceramic types: 1 ceramic type is all made of ceramic slurry. The manufacturing process is to first fix the pattern on the stencil, coat the sand box, and then pour the tuned ceramic slurry into the sand box, and then mold the mold after hardening, and then become a mold after high temperature roasting. 2 Using a bushing, a ceramic slurry is poured into the gap between the bushing and the pattern to make a mold. The bushing can be of sand type or metal type. Watering the ceramic shell with a bushing can save a lot of ceramic slurry and is used more in production. The surface roughness of ceramic castings can reach Ra10 ~ 1.25 microns, the dimensional accuracy is up to 3 ~ 5, can achieve the purpose of no cutting. Ceramic casting has a short production cycle and high metal utilization rate. The largest casting can reach more than ten tons. It is mainly used for casting large thick-walled precision castings and casting single-piece small batches of die, forging die, plastic die, metal die, die-casting die, glass die and other molds. The life of a ceramic casting mold is comparable to that of a mold made by a mechanical method, and the manufacturing cost is lower than that of a mold made by a machining method.

  Of all the casting yields, 60 to 70% of the castings are produced in sand form, and about 70% of them are produced in clay sand. The main reason is that sand casting has lower cost, simple production process and shorter production cycle than other casting methods. Therefore, castings such as the engine cylinder block, cylinder head and crankshaft of the automobile are produced by the clay wet sand molding process. When the wet type does not meet the requirements, consider using a clay sand table dry sand type, dry sand type or other sand type. Clay wet sand castings can weigh from a few kilograms up to tens of kilograms, while clay dry castings can weigh up to tens of tons.
Generally speaking, for medium and large castings, cast iron parts can be made of resin self-hardening sand type, and steel castings can be produced with water glass sand type, and castings with precise dimensions and smooth surface can be obtained, but the cost is high.
Of course, casting precision, surface finish, material density, metallographic structure, and mechanical properties of sand casting are often poor, so when these performance requirements of castings are higher, other casting methods should be used, such as investment casting. Wax) casting, die casting, low pressure casting, etc.

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