For the liquid shrinkage of nodular cast iron, the macro performance is the decline of molten iron liquid level, and the micro performance is the volume shrinkage caused by the continuous reduction of atomic kinetic energy and atomic spacing in the ferroalloy system. The volume shrinkage can be described by the following formula.
Where:
△ VSL is the liquid shrinkage of volume V0 in the time step from t to t + △ t.
α SL is the liquid volume shrinkage coefficient of the alloy.
TT is the temperature of volume V0 at time t.
TT + △ t is the temperature of volume V0 at t + △ t.
V0 is the volume of v0.
It can be seen from the formula that the volume shrinkage is only related to the alloy material and temperature difference, and the shrinkage will be slightly different due to the different chemical composition of ferroalloy and external conditions. There is a formula to calculate the volume shrinkage of general nodular iron. The volume shrinkage is 1.5% per 100 ℃ temperature drop. The temperature range of liquid phase volume shrinkage of general nodular cast iron is from pouring temperature to crystallization temperature (1150 ℃).