Equal amounts of a liquid metal at the same temperature are poured into three moulds made of steel, copper and aluminum. The shape of the cavity is a cylinder with $$15$$ $$mm$$ diameter. The size of the moulds are such that the outside temper-ature of the moulds do not increase appreciably beyond the atmospheric temperature during solidification. The sequence of solidification in the mould from the fastest to slowest is

(Thermal conductivities of steel, copper and aluminum are $$60.5, 401$$ and $$237$$ $$W/m$$-$$K,$$ respectively. Specific heats of steel, copper and aluminum are $$434, 385$$ and $$903$$ $$J/kg$$-$$K,$$ respectively. Densities of steel, copper and aluminum are $$7854, 8933$$ and $$2700$$ $$kg/{m^3},$$ respectively.)

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

In full mould (cavity-less) casting process, the Pattern is made of

The hot tearing in a metal casting is due to