Besides casting materials, what causes the casting dimensional accuracy?

Precision casting is widely used in jet engines, gas turbines, steam turbines, aircraft parts, internal combustion engines, vehicles, food machinery, printing machinery, paper machinery, compressors, valves, pumps, meters, sewing machines, weapons, business machines, and other machine parts.

Generally speaking, the dimensional accuracy of precision casting is affected by many factors, such as casting structure, casting material, mould making, shell making, roasting, pouring, etc. Any unreasonable link setting and operation will change the shrinkage rate of casting, resulting in deviation of the dimensional accuracy and requirements of casting. The following factors can cause defects in dimensional accuracy of precision castings:

1. The higher the pouring temperature, the greater the shrinkage during cooling. The lower the temperature, the smaller the shrinkage.

2. The larger the wall thickness is, the larger the shrinkage rate is, and the thickness of the wax increases when the wall thickness increases. Wax / casting shrinkage is large, hindering shrinkage.

3. Zirconium sand and zirconium powder are little affected by temperature, but the change of shell thickness will hinder the shrinkage of castings. The thicker the shell is, the smaller the shrinkage is, the thinner the shell is, and the larger the shrinkage rate is.

4. The size change caused by shell roasting can be neglected, but the shell deformation during shell roasting, the shell swelling caused by dewaxing and the floating core produced during pouring process will seriously reduce the size tolerance grade of castings.

5. The higher the carbon content is, the smaller the linear shrinkage is, the lower the carbon content is, and the larger the shrinkage is. At the same time, different alloying elements also affect the linear shrinkage of castings when alloying elements are added.