45.4 OTHER TOPICS

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45.4.1 Furnaces

Some of the types include,

- coreless induction - magnetic fields induce eddy currents throughout the entire furnace, resulting in melting

- core induction - magnetic fields induce eddy currents in a small section of the furnace, resulting in melting

- gas fired crucible - uses ignited gas and air to heat crucible in enclosed oven

- electric arc - arcs are used to heat metals

- cupolas - layers of metal and ore are placed in this refractory lined vessel, and ignited to produce large volumes of metal.

45.4.2 Inspection of Casting

General problems with castings are,

- cavities

- projections

- discontinuities

- defective surfaces

- incomplete

- incorrect dimensions

- inclusions

Typical inspection methods are,

- polishers & microscopes to look at microscopic structures

- metal analyzer to determine chemical composition

- X-rays are used to examine hidden cracks and blowholes