Do grey cast iron expand from freezing point to room temperature (cooling process)?
The thermal expansion coefficient for grey cast iron is ~ 10.8 in/(in*degR) see: list of expansion coefficients.
This would indicate that expansion is expected from ambient temperature to melting temperature so the reverse would be to expect shrinkage while cooling to ambient temperature.
Slightly related note, I was taught that gray cast iron is more ductile than regular cast iron so it is less susceptible to shrinkage cracking while it is cooling, for whatever that may be worth.
No and yes; and no. Pearlitic grey freezes as austenite plus graphite. It shrinks as it cools until the austenite transforms to pearlite , this causes expansion over a very short temperature range . Then the pearlite and graphite continue to shrink. This is a higher strength grey iron. The other grey iron ( most common): Ferritic iron probably freezes as ferrite and graphite and shrinks all the way to room temperature ( no phase transformation).( There is a chance there is some austenite to ferrite transformation at high temperature like 1600 F if small amounts of austenite are formed during freezing). Nodular (ductile) iron is about the same . Malleable iron is a different story.White cast iron is very hard and brittle ,has few uses , mostly it is made into malleable iron by heat-treatment