Various Factors That Affect The Dimensional Accuracy Of Stainless Steel Precision Castings
Oct 20, 2023| The following factors cause dimensional accuracy defects in precision castings as follows:
1. The influence of the casting structure
The wall thickness of the casting is large, and the wall of the casting is thin, and the shrinkage is small. The free shrinkage rate is large, and the hindrance shrinkage rate is small.
2. The influence of casting material
The higher the carbon content in the material, the smaller the linear shrinkage, and the lower the carbon content, the greater the linear shrinkage.
The casting shrinkage of common materials is as follows: casting shrinkage K=(LM-LJ)/LJ×1, LM is the cavity size, LJ is the casting size.
3. The influence of mold making on the shrinkage rate of casting line
The effects of wax injection temperature, wax injection pressure and holding time on the investment size were obvious in wax injection temperature, followed by wax injection pressure, and the holding time had little influence on the investment size after investment molding. The linear shrinkage of wax (mold) material is about 0.9-1.1%.
When the investment mold is stored, further shrinkage will occur, and its shrinkage value is about 10% of the total shrinkage, but when stored for 12 hours, the investment mold size is basically stable. The radial shrinkage of the wax mold is only 30-40% of the shrinkage in the length direction, and the effect of wax injection temperature on the free shrinkage is much greater than that on the hindered shrinkage (the wax injection temperature is 57-59 °C, the higher the temperature, the greater the shrinkage).
4. The influence of shell materials
Zircon sand, zircon powder, Shangdian sand and Shangdian powder are used because of their small expansion coefficient, which is only 4.6×10-6/°C, which is negligible.
5. The influence of casting temperature
The higher the pouring temperature, the greater the shrinkage, and the lower the pouring temperature, the smaller the shrinkage, so the pouring temperature should be appropriate.
6. The influence of shell roasting
Due to the small expansion coefficient of the shell, when the shell temperature is 1150°C, it is only 0.053%, so it is also negligible.