Consider sand casting of a cube of edge length a. A cylindrical riser is placed at the top of the casting. Assume solidification time, t_s ∝ V/A, where V is the volume and A is the total surface area dissipating heat. If the top of the riser is insulated, which of the following radius/radii of riser is/are acceptable?

Which of these processes involve(s) melting in metallic workpieces?

The welding process which uses a blanket of fusible granular flux is

The part of a gating system which regulates the rate of pouring of molten metal is