Demagnetizing

Why demagnetizing?

A lot of machined parts have to be absolutely free of magnetism because of their intended use.

If materials or tools are magnetized, there may be negative effects, e.g.:

• sticking steel chips or grinding dust

• assembly problems

• blow effects which complicate the welding process or lead to faulty weld seams

• sticking parts in collecting tanks or on machine parts

• premature wear of components due to sticking microparticles, e.g. in bearings and gears

Workpieces may become magnetized by:

• transport with lifting magnets or magnetic roller conveyors

• magnetic particle tests

• magnetic clamping fi xtures

• DC welding with high currents

• induction hardening

What happens during the demagnetizing process?

Physical process:

In magnetizable (ferromagnetic) materials extremely weak magnetic fi elds are available, also called molecular magnets. Without the infl uence of an external magnet fi eld these molecular magnets are arranged at random. When applying an external magnetic fi eld, the molecular magnets start arranging. As stronger the external magnetic fi eld, as stronger the arrangement of the molecular magnets until magnetic saturation is reached. After removing the external magnetic fi eld, this forced formation remains.

The parts are demagnetized by passing them through a strong alternating magnetic field which gradually becomes weaker. The alternating field causes a continuous change in magnetization of the molecular magnets. If the strength of the magnetic field is gradually reduced, less and less molecular magnets are arranged. The strength of the magnetic field is reduced by moving the part slowly and consistently out of the alternating field.

What does the degree of demagnetizing depend on?

The degree of demagnetizing depends on the following factors:

• size, shape and material of the parts to be demagnetized

• distance of the parts to the demagnetizing unit

• distance between the parts

• magnetic condition before demagnetizing and the permissible limit values after demagnetizing

• the speed of the workpiece while moving through the demagnetizing area

• the frequency of the alternating magnetic field

Best demagnetization results are obtained by optimal parameter settings. Belt speed, demagnetizing frequency and distance of demagnetizing unit to workpiece are manually adjustable. Therefore, Wagner demagnetizing units with conveyor ensure an extremely uniform demagnetizing of workpieces. The unit can be used as fully automated system or independent single workplace solution.