(1) Sand casting process: it is a casting system composed of molding, core making, drying, mold closing, pouring, sand dropping, cleaning and other processes. The difference between the products cast by sand casting process is that sand casting is worthy of the name. These product models and other process equipment are used to make “sand molds” Then the molten liquid metal is filled into the sand mold and cooled to obtain the required casting; Sand casting is not limited by quantity, and is suitable for casting of various castings. There are many processes, so sand casting is more complex.
(2) Characteristics of sand casting process: its advantages are that the working temperature of sand mold made by sand casting process is no more than 300 ℃ and the working pressure is no more than 1.5MPa compared with other molds. Its mold materials have a wide selection range, long service life and low mold cost. Its disadvantages include three aspects: the first is the problem of unstable dimensional accuracy, because the casting is made according to the mold 。 Without exception, the size of the die will be affected by the casting. Especially for some complex castings, due to the use of multiple molds, the accumulated error has seriously affected the casting size. Therefore, it is unrealistic to pursue zero error in sand casting.
Secondly, the casting surface is rough, and there are inevitably some rough places in the sand mold, so it is difficult to get a bright and clean casting. Thirdly, the casting has defects. Most of the casting defects come from poor mold quality, such as uneven bending or inclination of the mold surface. The model will be poor, and the damaged model surface will cause defects in the product; During installation, the installation deviation will lead to box squeezing and sand holes; The non-standard or random installation of the gating system leads to the flow of liquid metal deviating from the process requirements, resulting in shrinkage and porosity. These factors lead to the instability of sand casting products.
(3) Prospect of sand casting process: with the development of social economy and the continuous progress of casting industry, the high compaction molding method of sand casting process (including high-pressure molding, injection molding and air impact molding) will be widely used. It is characterized by less damage and deformation in the process of transporting, closing and pouring. The castings produced by it have high dimensional accuracy, greatly improved surface quality and less waste products. Since the advent of high-pressure molding method, the sharp rebound of sand mold has attracted the attention of some scholars and sand mold casting researchers, The senior engineer of sand casting of hy casting pointed out that the rebound will increase with the increase of compaction specific pressure, and large rebound will cause the change of mold cavity and affect the dimensional accuracy of castings. However, the rebound problem of sand mold at home and abroad is in static measurement, which is lack of strong basis. We still need to deepen its discussion. Nowadays, high compactness sand mold is good, but high compactness sand mold restricts the improvement of process casting to a higher level. Compared with foreign countries, the level of sand mold casting industry in China has made rapid progress. At the same time, we also need to change our thinking and mechanism, constantly explore and learn to expand the sand casting industry in our country.