The dimensional accuracy of Carbon Steel Hollow Ball castings is generally influenced by the structure, material, molding, shelling, roasting, casting, etc. of the castings, specifically:
(1) Casting structure
Mainly due to the wall thickness and shrinkage of the casting, the two are proportional to each other. That is to say, if the wall thickness of the casting is large, then the shrinkage rate will be large, and vice versa.
Mainly refers to the carbon content of the material. Generally speaking, the higher the carbon content, the smaller the linear shrinkage rate, and vice versa.
In this regard, we mainly need to understand the following points:
a. The wax temperature, which has a much greater effect on the free shrinkage than on the resisted shrinkage.
b. The investment mold will shrink further during storage, generally 10%. But after 12 hours of storage, the size will not change.
c. The pressure of the wax and the time of holding the pressure will also have an effect, but none of the effects of the temperature of the wax are large.
The materials used in shell making are mainly zircon sand, zircon powder, Shangdian sand, etc., but this aspect is negligible because of its small expansion coefficient.
Since the coefficient of expansion of the shell is small, this aspect is also negligible.