The dimensional accuracy of stainless steel precision casting is influenced by factors such as casting structure, casting material, mold making, shell making, roasting, pouring, etc. Any unreasonable setting and operation of any link can cause changes in the shrinkage rate of the casting, leading to deviations in the dimensional accuracy and requirements of the casting.

The factors that cause dimensional accuracy defects in stainless steel precision casting castings are as follows:

1. The influence of casting structure

Casting wall thickness, high shrinkage rate, thin casting wall, low shrinkage rate

High free shrinkage rate, low hindrance shrinkage rate

2. The influence of casting material

The higher the carbon content in the material, the smaller the linear shrinkage rate. The lower the carbon content, the greater the linear shrinkage rate

The casting shrinkage rate of common materials is as follows: Casting shrinkage rate K=(LM-LJ)/LJ × 100%, LM is the cavity size, LJ is the casting size

3. The influence of mold making on the linear shrinkage rate of castings

The influence of wax injection temperature, wax injection pressure, and holding time on the size of the investment mold is most obvious with wax injection temperature, followed by wax injection pressure. Holding time has little effect on the final size of the investment mold after ensuring its formation

The linear shrinkage rate of wax (mold) material is about 0.9-1.1%

When the investment mold is stored, further shrinkage will occur, with a shrinkage value of about 10% of the total shrinkage. However, after 12 hours of storage, the size of the investment mold is basically stable

The radial shrinkage rate of wax molds is only 30-40% of the length direction shrinkage rate, and the effect of wax injection temperature on the free shrinkage rate is much greater than on the hindered shrinkage rate (the appropriate wax injection temperature is 57-59 ℃, the higher the temperature, the greater the shrinkage)

4. The influence of shell making materials

Using zircon sand, zircon powder, Shangdian sand, and Shangdian powder, due to their small coefficient of expansion, it is only 4.6 × 10-6/℃, negligible

5. The influence of casting temperature

The higher the pouring temperature, the greater the shrinkage rate. The lower the pouring temperature, the smaller the shrinkage rate. Therefore, 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 ℃, it is only 0.053%, so it can also be ignored