Workshop Technology
During hot working of metals

Porosity of the metal is largely eliminated
Mechanical properties are improved due to refinement of grains
Grain structure of the metal is refined
All of the listed here

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Workshop Technology
The purpose of a riser is to

Act as a reservoir for the molten metal
Deliver the molten metal from pouring basin to gate
Deliver molten metal into the mould cavity
Feed the molten metal to the casting in order to compensate for the shrinkage

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