Demagnetization (2) Flashcards Preview

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Flashcards in Demagnetization (2) Deck (15)
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1
Q

Step Down Demagnetization

A

Place the part in the coil or between the clamp heads and decay current values going from maximum to minimum to effectively demagnetize the part.

2
Q

AC Tunnel Coil

A
  • one of the more common means of demagnetizing

- coil is energized with a rapidly reversing, constantly diminishing AC.

3
Q

Manual Demagnetization

A

Using a portable coil, simultaneously energize the coil while moving the part through and away from the coil (about 3-5ft)
- repeat until remnant fields are acceptable

4
Q

To demagnetize a part, the current value must be ____ to or ____ than the current value that was used to test the part.

A

equal to or less than

5
Q

For complex geometric parts, demagnetization is often more successful if the part is ______ and ______.

A

rotated and turned

6
Q

Demagnetization via heat treatment

A

heat treatment temperatures often exceed the curie point causing the material to lose and ferromagnetic properties, cooling it regains them but will not retain the magnetic field.

7
Q

Demagnetization using DC

A

current is slightly reduced then completely reversed in direction (1 to 1.5 seconds per step)

8
Q

Contact yoke demagnetization methods

A
  • energized in contact and pulled up and away
  • energized and twisted
  • energized and dragged away
9
Q

Non-contact yoke demagnetization method

A

parts are passed between the poles and withdrawn while the yoke is energized

10
Q

Special demagnetization techniques (3)

A
  • rubber mallet
  • positioning
  • transient
11
Q

Rubber Mallet Demagnetization

A
  • not recommended

- striking a part with a rubber mallet during the demagnetization operation.

12
Q

Positioning Demagnetization

A

Longer parts can be magnetized by earths poles, this is why it is recommended that demagnetizing coils/coils should be positioned so that the part has its long axis positioned in an east-west direction.

13
Q

Transient Demagnetization

A
  • for large, strong fielded parts
  • place part in demagnetizing coil, current turned on and off 5-10x, reinitiate the current and pull the part out of the coil with current on.
14
Q

Small cylinder demagnetization

A

in an AC coil when the L/D ration is 1 or less, rotating the part 180° motions while withdrawing from energized coil.

or use two pole pieces to assist in increasing the L/D ratio for demagnetization

15
Q

Circular field demagnetization

A

convert field into longitudinal and the demagnetize as, field will exhibit poles.