Defects in sand casting process

Sand casting industry is an ancient and very important traditional industry. Whether in developed countries or developing countries, sand casting industry has an irreplaceable position. According to the structural characteristics, technical requirements, production batch and production conditions of sand casting parts, the process of determining the sand casting scheme and process parameters, drawing the sand casting process map, weaving the process card and other technical documents is the first casting process design that should be carried out before sand casting production. Sand casting process design is the basic component and key link of casting production. The quality of sand casting process design plays an important role in casting quality, productivity and cost.

At present, the sand casting industry basically adopts the traditional process design method. The process modification is frequent, which requires a lot of manpower and material resources, resulting in high development cost. Even if the product quality meets the user’s requirements, it is impossible to verify whether the process is the most reasonable.

It can be seen from the traditional flow chart that the traditional product development belongs to a judgment method of trial production first. When the process improvement is required, the process test shall be carried out again. In this way, the final mature and reasonable process can be obtained. The same is true for the process of quality improvement. Its characteristics of high consumption, high cost, low efficiency and low yield are extremely unfavorable to enterprises in the fierce market competition. The main defects caused by unreasonable process design include:

(1) Shrinkage cavity and shrinkage porosity of sand casting exceed the acceptable range of users.

(2) Surface defects such as slag inclusion and sand filling caused by unstable flow of molten iron exceed the allowable range of users.

(3) The material properties of sand casting can not meet the user’s requirements.

In view of the above situation, a stable and reliable process must be established in the product development stage to eliminate these defects, so as to ensure reliable product quality and low rejection rate after mass production. The research and development of sand casting CAE make the application of computer simulation of sand casting filling solidification process in engineering possible and realistic.