About residual magnetism

After having come into contact with a magnetic field (typically lifting magnets, induction processes, etc ..., or just following the sole contact between steel bodies), steel materials may keep some of the magnetism within their structure, called "residual magnetism".

The intensity of the residual magnetism will depend upon various factors among which the most important are:

The presence of residual magnetism may cause disturbances to further machining processes, thus calling for its removal.

 

Solution for its removal

Three different SGM solutions to remove residual magnetism from steel products:

1. Demagnetizing Tunnels
2. Control panel demagnetizing cycle
3. Electro-permanent magnets

Depending on the nature and intensity of the residual magnetism, SGM disposes of demagnetizing tunnels (made of one, two or three tunnels).

  • Advantage: solution that manages to pratically nullify any residual magnetism however high (B, magnetic induction) and strong (H, magnetic field) it may be.

  • Disadvantages: after processing steel through demagnetizing tunnels, any contact with magnets should be avoided, requesting mechanical systems for further handling; it cannot be used on bundled material.

When handling ferrous loads with electro-magnets, the magnet control panel will carry out a special demagnetizing cycle after the de-energize operation. The electro-magnets used for this demagnetization cycle purpose must be of specific design.

  • Advantage: being built inside the magnet lifting device, magnets can remain in use for all the load transportation phases;

  • Disadvantage: the magnet de-energizing cycle will require an extra 3 to 8 seconds.

  • residual magnetism in the load will be significantly reduced, however it may not be nullified completely, depending on the steel grade of the load.

  • demagnetizing cycle will mainly act on the residual magnetism left in the material by the electro-magnet. It will have a limited impact on the other possible sources of residual magnetism.

Electro- permanent magnets, as a resalt of their shallow magnetic field and the specific way they are de-activated, leave significantly less residual magnetism in the steel loads they have been in contact with compared to electro-magnets.

  • Advantage: same as for the above demagnetizing cycle with, in addition, a significantly shorter demagnetization time;