Lost wax casting impact precision elements

Update:19 Apr 2019

Under normal circumstances, the precision of precision […]

Under normal circumstances, the precision of precision castings is affected by many factors such as the structure of the casting, the raw materials of the casting, the molding, the shell, the roasting, the casting, etc. The setting and operation of any one of the links will change the shortening rate of the casting. This leads to errors in the dimensional accuracy and requirements of castings.

(1) Influence of casting structure: a. The wall thickness of the casting is large, the shortening rate is large, the casting wall is thin, and the shortening rate is small. b. The rate of free shortening is large, which hinders the shortening rate.

(2) Influence of casting materials: a. The higher the carbon content in the material guess, the smaller the line shortening rate, and the lower the carbon content, the greater the line shortening rate. b. The casting shortening rate of common raw materials is as follows: casting shortening rate K=(LM-LJ)/LJ×100%, LM is the cavity scale, and LJ is the casting scale. K is affected by the following factors: wax mold K1, casting structure K2, alloy type K3, and pouring temperature K4.

(3) The influence of mold making on the shortening rate of casting line: the influence of waxing temperature, waxing pressure and dwell time on the scale of the investment is the most obvious temperature of the wax, followed by the pressure of the wax, and the pressure keeping time ensures the investment. The effect on the final dimensions of the investment after forming is small. The radial shortening rate of the wax mold is only 30-40% of the length shortening rate. The effect of the wax temperature on the free shortening rate is far greater than the resistance shortening rate (the optimum wax temperature is 57-59 ° C, the temperature is higher. The height is shortened more).

(4) Influence of shell material: Zircon sand, zircon powder, Shangdian sand and Shangdian powder are selected, because the expansion coefficient is small, only 4.6×10-6/°C, so it can be ignored.

(5) Influence of casting temperature: The higher the pouring temperature, the larger the shortening rate, the lower the casting temperature, and the smaller the shortening rate, so the pouring temperature should be appropriate.