Annealing by short circuit

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Annealing by short circuit is a method of efficiently annealing copper wire which employs a controlled electrical short circuit. It can be advantageous because it does not require a temperature-regulated furnace like other methods of annealing.

Process

The process consists of two conductive pulleys (step pulleys) which the wire passes across after it is drawn. The two pulleys have an electrical potential across them, which causes the wire to form a short circuit. The Joule effect causes the temperature of the wire to rise to approximately 400 °C. This temperature is affected by the rotational speed of the pulleys, the ambient temperature, and the voltage applied. Where $t$ is the temperature of the wire, $K$ is a constant, $V$ is the voltage applied, $r$ is the number of rotations of the pulleys per minute, and $t_{a}$ is the ambient temperature:

t={\frac {KV^{2}}{r}}+t_{a}

The constant $K$ depends on the diameter of the pulleys and the resistivity of the copper.

Purely in terms of the temperature of the copper wire, an increase in the speed with which the wire passes through the pulley system has the same effect as a decrease in resistance. Therefore, the speed with which the wire can be drawn through varies quadratically as the voltage applied.

References

Thesis of Degree, Cable Manufacture and Tests of General Use and Energy. - Jorge Luis Pedraz (1994), UNI, Files, Peru.
Dynamic annealing of the Copper wire by using a Controlled Short circuit. = Jorge Luis Pedraz (1999), Peru: Lima, CONIMERA 1999, INTERCON 99,

Iron and steel production

Iron production
(Ironworks)

Smelting	Bloomery (produces sponge iron) Blast furnace (produces pig iron) Cold blast Hot blast Anthracite iron Direct reduced iron
Secondary	Wrought iron (via Finery forge or Reverberatory Puddling Furnace) Cast iron (via Cupola furnace or Induction furnace)

Steelmaking
(Steel mill)

Primary (Pre-1850)	Pattern welding Crucible steel (Damascus steel, Wootz steel) Tatara furnace Cementation process
Primary (Post-1850)	Bessemer process Open hearth furnace Electric arc furnace Basic oxygen process
Secondary	Electro-slag remelting Vacuum arc remelting Argon oxygen decarburization

Heat treatment methods

Annealing	Low hydrogen Short circuit
Hardening / Case-hardening	Ausforming Boriding Carbonitriding Carburizing Cryogenic Ferritic nitrocarburizing Induction Nitriding Precipitation Quench polish quench
Tempering	Austempering Martempering
Cryogenic treatment (Deburring Deflashing Hardening) Differential heat treatment Decarburization Forming gas Post weld heat treatment Quenching Superplastic forming

Production by country

Category:

Metal heat treatments

Process

See also

References