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Use of miniature magnetic sensors for real-time control of the induction heating process

United States Patent

September 24, 2002
View the Complete Patent at the US Patent & Trademark Office
Sandia National Laboratories - Visit the Intellectual Property Management and Licensing Website
A method of monitoring the process of induction heating a workpiece. A miniature magnetic sensor located near the outer surface of the workpiece measures changes in the surface magnetic field caused by changes in the magnetic properties of the workpiece as it heats up during induction heating (or cools down during quenching). A passive miniature magnetic sensor detects a distinct magnetic spike that appears when the saturation field, B.sub.sat, of the workpiece has been exceeded. This distinct magnetic spike disappears when the workpiece's surface temperature exceeds its Curie temperature, due to the sudden decrease in its magnetic permeability. Alternatively, an active magnetic sensor can also be used to measure changes in the resonance response of the monitor coil when the excitation coil is linearly swept over 0-10 MHz, due to changes in the magnetic permeability and electrical resistivity of the workpiece as its temperature increases (or decreases).
Bentley; Anthony E. (Tijeras, NM), Kelley; John Bruce (Albuquerque, NM), Zutavern; Fred J. (Albuquerque, NM)
Sandia Corporation (Albuquerque, NM)
09/ 718,289
November 21, 2000
FEDERALLY SPONSORED RESEARCH The United States Government has rights in this invention pursuant to Department of Energy Contract No. DE-AC04-94AL85000 with Sandia Corporation.