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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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