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Hardening Metals with Electric Fields
Name: Michael
Status: student
Grade: 9-12
Country: United Kingdom
Date: Summer 2009
Question:
Is it possible to greatly increase the
hardness of a metal through the application of
electromagnetic power or an electric current? I have
heard that ceramics can become harder this way but
have not been able to find out anything regarding
metallic solids. Does it have something to do with
the dielectric properties or electric polarization
of the substance?
Replies:
Hi Michael,
Some metals or alloys like high carbon steel are able to be hardened
using heat and subsequent rapid cooling, but it makes no difference
what creates the heat. Other metal alloys are able to be hardened by
what is called precipitation hardening with can involve moderate
heating for long periods. Still others are not able to be hardened at
all by heat.
But there are no metals or metal alloys that can have their hardness
increased simply by the application of an electric current or a
magnetic field. Many metals can be heated to red heat by the
application an alternating high frequency magnetic field, but it is
the heat that causes any changes in hardness, not the magnetic field.
Similarly, metals can be heated by a large electric current flowing
through them, often causing changes in hardness. Once again, however,
it is the presence of heat that affects hardness, not the fact that
the heat is generated by electrical current.
Regards,
Bob Wilson
Mike
I have not heard of electrical currents being used to harden metals
But I found a patent at the following URL:
http://www.patentstorm.us/patents/4215259.html
The patent says that if you bring electric conductors close to a metal
surface,
The surface of the metal close to the conductor "flash" heats to a
transformational
Temperature that produce lines of hardening in the metal.
Sincere regards,
Mike Stewart
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Update: June 2012
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