The shrinkage of the wear resistant casting will be hindered by different types. Some resistance comes from the mold or core, while others are caused by the casting structure itself. The casting shrinkage will vary depending on the size of the wear resistant casting or the thickness of the wall and the complexity of the structure, and will appear difference in all directions of the casting.
Wear resistant castings are difficult to process. The deviation of casting size or the error of flatness will affect the assembly use. Only because of the size deviation or casting hole size deviation will also make the casting scrap.
It is precisely because of this, how to get the wear resistant castings which meet the size deviation, accurately controlling the shrinkage of the casting is a more important problem. In view of this, the study of the law of size shrinkage, with process parameters as the basis for the formulation of production process.
The casting shrinkage of wear resistant casting under sand casting conditions is 2.6% ~1.7%. However, there will be changes in the size and thickness of the casting. The thicker the wall is, the stronger the heat of the metal for the mold will be. When the mold material is heated, the strength will be lost, the resistance to the shrinkage of the casting will be reduced, and the casting will have a greater shrinkage in the mold, and the shrinkage is very high. Conversely, the contraction value is very low.
The larger the size of the wear resistant casting is, the greater the hindrance of the mold and the casting will be, and the shrinkage will be less. On the contrary, the shrinkage rate of small parts with simple shape is very high. Summing up the production experience data, the relationship between the wall thickness, the wear resistance casting overall size and the casting shrinkage rate is obtained, and the data of medium carbon steel (0.2% - 0.5% C) and low alloy steel are obtained.