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The following six factors affect the dimensional accuracy of precision castings

November 02, 2019

The following six factors affect the dimensional accuracy of precision castings

In general, the dimensional accuracy of stainless steel casting is affected by the cast structure, the cast material, the mold making, and the casting process. Unreasonable operations can cause changes in the casting shrinkage rate, resulting in variations in the dimensional accuracy of the casting.

  • (1) Influence of casting structure: a. The casting has thick wall, large shrinkage, thin wall and small shrinkage. b.. Free shrinkage enhances and impedes shrinkage.
  • (2) Influence of castable: The higher the carbon content in the raw material, the smaller the line shrinkage, and the lower the carbon content, the larger the line shrinkage.
  • (3) The influence of mold making on the shrinkage rate of the casting line: a. The temperature of the injection wax, the pressure of the injection wax, and the pressure holding time have the most obvious influence on the mold size, followed by the injection wax pressure. After the mold is formed, the dwell time has little effect on the final size of the mold. The linear shrinkage of the wax (mold) material is about 0.8-1.2%. The weld mold is further contracted after deposition, and the shrinkage value is about 11% of the total shrinkage. However, after 16 hours of storage, the size of the weld mold was basically stable. The radial shrinkage of the wax model is only 35-40% of the longitudinal shrinkage, and the effect of the shot wax temperature on the free shrinkage is much greater than the shrinkage (the optimum temperature is around 58 °C).

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  • (4) Influence of shell material: Zircon sand and zircon powder, because of its small expansion coefficient, can be ignored.
  • (5) Effect of shell roasting: Due to the shell with a small expansion coefficient, when the shell temperature reaches 1120 ° C, it is only 0.073%, so it can be ignored.
  • (6) Effect of pouring temperature: The higher the pouring temperature, the higher the shrinkage rate, and the lower the pouring temperature, the smaller the shrinkage rate. Therefore, the pouring temperature should be appropriate.
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Edward Yue