The linear shrinkage of the bridge shell has a great influence on the accuracy of the size of the bridge shell. The shrinkage of metal in liquid state is shown as the drop of liquid level, which can only be expressed by the reduction of volume. The volume shrinkage can be supplemented by the riser. He does not affect the final size of the bridge shell. And the line contraction is irreparable. The size of the mold can only be pre amplified by considering the shrinkage value accurately. The formula of shrinkage rate of casting is:
LM – working face size of die (mm);
LJ – bridge shell size (mm).
The shrinkage of casting is affected by many factors. The shrinkage rate of cast steel bridge shell was found by consulting the literature.
The correct selection of casting shrinkage is very important, which will directly affect the size accuracy of the bridge shell. The material of tractor broken bridge shell is zg40mn. According to the solidification theory of casting, the shrinkage rate of metal liquid during solidification is no more than its free shrinkage rate. Considering the blocking and the structure of parts, the casting shrinkage rate is 2%.