What are the factors related to the strength of heat-resistant steel precision castings?

The performance of heat-resistant steel precision castings will change, especially after the influence of some specific factors, the performance changes will be more obvious. So in terms of the strength of heat-resistant steel precision castings, what are the influencing factors?

On the one hand, it must be the influence of temperature. Temperature fluctuations have a great influence on any material, including heat-resistant steel. Due to factors such as multiple starts, shutdowns or overloads, the operating temperature will fluctuate, and temperature fluctuations will accelerate the creep process of the material, thereby reducing the endurance strength.

Another aspect is the effect of stress. Under the influence of factors such as test temperature, notch geometry, steel’s lasting plasticity, heat treatment process and steel composition, the amount of stress existing in heat-resistant steel precision castings will also be different. This in turn affects the brittleness of the material, so this factor must be given enough attention in the design.

Heat-resistant Steel Heat-resistant Steel
What are the factors that affect the accuracy of heat-resistant steel precision castings?
Influence of casting structure:
  • The casting wall is thick and the shrinkage rate is large, and the casting wall is thin and the shrinkage rate is small.
  • The free shrinkage rate is large, and the hindered shrinkage rate is small.
The influence of casting material:
  • The higher the carbon content in the material, the smaller the linear shrinkage rate and the lower the carbon content, the greater the linear shrinkage rate.
The influence of mould making on the linear shrinkage rate of castings:
  • The influence of wax injection temperature, wax injection pressure, and pressure holding time on the size of the investment mold is obvious from the wax injection temperature, followed by the wax injection pressure. The pressure holding time has little effect on the final size of the investment mold after the investment is formed.
  • The linear shrinkage rate of wax is about 0.9-1.1%.
  • When the investment mold is stored, there will be further shrinkage, 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 rate of the wax mold is only 30-40% of the lengthwise shrinkage rate. The influence of the wax injection temperature on the free shrinkage rate is far greater than the influence on the hindered shrinkage rate.

Heat-resistant Steel Heat-resistant Steel

The influence of shell-making materials:
  • Zircon sand, zircon powder, Shangdian sand, and Shangdian powder are used. Because of their small expansion coefficient, they can be ignored.
The effect of shell baking:
  • Because the expansion coefficient of the shell is small, when the temperature of the shell is 1150℃, it is only 0.053%, so it can be ignored.
The influence of casting temperature:
  • The higher the casting temperature, the greater the shrinkage rate, and the lower the casting temperature, the smaller the shrinkage rate, so the casting temperature should be appropriate.

 

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