The optimum pouring time for a casting depends on several factors. One important factor among them is

Low permeability molds and low pouring temperature of the molten metal causes ......................... defect in castings.

The problem of shrinkage cavity is more likely to occur while casting ......... A ............ B.......... a chill block

(A.) metal / plastic , (B.) with / without.

For casting of turbine blades made of high temp and high strength alloys, the most suitable process is