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How to Demagnetize Steel

by Samuel Markings

The periodic table contains three room-temperature ferromagnetic elements: nickel, cobalt and iron. These ferromagnetic elements possess a spontaneous internal magnetic field known as magnetization. Magnetization is responsible for the well-known attraction and repulsion seen in everyday permanent magnets. Steel is a general term for alloys composed primarily of iron but with additional elements such as carbon, silicon or chromium. Depending upon the specific composition, steel can be magnetic. The magnetization of steel can be reduced to zero by using a commercial demagnetizer.

Move all pieces of metal at least 30cm (11.8 inches) away from the demagnetizer (Ref 3, page 2). Switch on the demagnetizer and put on heat-proof gloves.

Place the item of steel onto the demagnetization plate that is located between the pole pieces of the electromagnet (Ref 3, page 2).

Starting on the side of the demagnetization plate closest to you, slowly move the piece of steel across the demagnetization plate. The steel part should be moved in a direction away from you and should reach the opposite end of the demagnetization plate in approximately 5 seconds.

To finish the demagnetization process, continue to move the piece of steel away from the demagnetization plate. The demagnetization process is complete once the steel piece reaches a distance of 20 cm away from the demagnetization plate.

Use a compass to ensure that the piece of steel has been demagnetized. Place the compass on a flat surface and rotate it until the needle is pointing in the north direction. Bring the piece of demagnetized steel to within a centimeter (0.4 inches) of the compass. Since a compass needle is a very thin freely suspended bar magnet, it will be deflected if a magnet is placed nearby. Therefore, the compass needle should not be deflected if the demagnetization process has been successful.

Items you will need
  • Commercial demagnetizer
  • Heat-proof gloves
  • Magnetized steel object
  • Compass

Warning

  • The surface of the demagnetizer is likely to have a raised temperature due to inductive heating. Ensure heat-proof gloves are worn in order to eliminate the possibility of burns.

About the Author

Samuel Markings has been writing for scientific publications for more than 10 years, and has published articles in journals such as "Nature." He is an expert in solid-state physics, and during the day is a researcher at a Russell Group U.K. university.

Photo Credits

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