In the last article, we introduced the development history of precision casting and its technological process. Today, we will talk about the classification of precision casting.
1. Ceramic type precision casting:
It is a precision casting method that uses ceramic slurry to make a casting mold to produce castings. Ceramic slurry is mixed with ethyl silicate hydrolyzate and fine refractory sand with relatively pure texture and high thermal stability, such as fused quartz, zircon, corundum, etc. In order to make the ceramic slurry gel in a short time, calcium hydroxide or magnesium oxide is often added as a catalyst. Because the composition of the refractory used and its appearance are similar to those of ceramics, it is called ceramic type. Ceramic type precision casting is a new process developed on the basis of ordinary sand casting.
Ceramic type precision casting is also divided into two types:
①The ceramic type is all made of ceramic slurry poured. The production process is to first fix the pattern on the mold plate, coat the sand box, and then pour the adjusted ceramic slurry into the sand box. ②Using a bushing, pouring ceramic slurry in the gap between the bushing and the pattern to make a mold. The bushing can be sand type or metal type. Pouring the ceramic shell with a bushing can save a lot of ceramic slurry and is widely used in production. The surface roughness of ceramic mold castings can reach Ra10-1.25 microns, and the dimensional accuracy is as high as 3-5 grades, which can achieve the purpose of less machining.
Ceramic type precision casting has short production cycle and high metal utilization rate. The largest casting can reach more than ten tons, which is mainly used for casting large-scale thick-walled precision castings and casting single-piece and small-batch punching dies, forging dies, plastic dies, metal dies, die-casting dies, glass dies and other molds. The service life of ceramic type precision casting molds is comparable to that of molds made by machining methods, and the manufacturing cost is lower than that of molds made by machining methods.
2. Sand type precision casting:
Among the total casting production, 60-70% of the castings are produced with sand molds, and about 70% of them are produced with clay sand molds. The main reason is that compared with other casting methods, sand casting has low cost, simple production process and short production cycle. Therefore, castings such as engine cylinder blocks, cylinder heads, crankshafts, etc. of automobiles are produced by the clay green sand process. When the wet type cannot meet the requirements, consider using the clay sand surface dry sand type, dry sand type or other sand type. The weight of precision castings produced by clay wet sand casting can range from a few kilograms to tens of kilograms, while the castings produced by clay dry casting can weigh dozens of tons.
Generally speaking, for medium and large castings, cast irons can be produced with resin no-bake sand molds, and steel castings can be produced with water glass sand molds, which can obtain castings with precise dimensions and smooth surfaces, but the cost is high.
Of course, the precision, surface finish, material density, metallographic structure, and mechanical properties of castings produced by sand casting are often poor. Therefore, when these performance requirements of castings are higher, other casting methods should be used, such as investment ( Lost wax) casting, die casting, low pressure casting, etc.
The above is the classification of precision casting organized by edit for you. If you want to get more industry information, please continue to pay attention to PARFECT STEEL.
