It is an effective measure to prevent shrinkage and porosity by setting risers at the thick wall and hot spot (i.e. the parts with concentrated heat on the casting and larger diameter of inner circle). The size of riser should ensure that the riser solidifies later than the parts to be compensated by it, and there is enough liquid metal supply. A "sequential solidification principle" is adopted to establish a riser on the casting. The temperature gradient gradually increases from the part far from the riser to the riser, thus realizing the sequential solidification from the part far from the riser to the riser, that is, the part far from the riser first solidifies, the part near the riser then solidifies, and the riser itself finally solidifies.
No. Chilled iron is a metal chill placed in the mould to increase the cooling speed of a part of the casting.