Carbon steel castings

The so-called investment casting process is simply to use fusible materials (such as wax or plastic) to make a fusible model (investment mold or model for short), apply several layers of special refractory coating on it, dry and harden it to form a whole mold shell, then melt the model from the mold shell with steam or hot water, then place the mold shell in the sand box, and fill the surrounding with dry sand for molding, Finally, the mold is put into the baking furnace and baked at high temperature (for example, when using high-strength shell, the mold shell after demoulding can be directly baked without molding). After the mold or shell is baked, molten metal is poured into it to obtain the casting.
The dimensional accuracy of investment castings is relatively high, generally up to CT4-6 (CT10~13 for sand casting and CT5~7 for die casting). Of course, due to the complexity of the investment casting process, there are many factors that affect the dimensional accuracy of castings, such as the shrinkage of the mold material, the deformation of the investment mold, the linear change of the mold shell during heating and cooling, the shrinkage of the alloy, and the deformation of the castings during solidification, the dimensional accuracy of ordinary investment castings is relatively high, However, its consistency still needs to be improved (the dimensional consistency of castings using medium and high temperature wax should be improved a lot).
When pressing the investment mold, the mold with high surface finish of the cavity is used, so the surface finish of the investment mold is also high. In addition, the mold shell is made by coating the refractory coating prepared by the special high temperature resistant binder and refractory materials on the investment mold, and the surface of the mold cavity directly in contact with the molten metal is smooth. Therefore, the surface finish of investment castings is higher than that of ordinary castings, generally reaching Ra.1.6~3.2 μ m。