Mu Metal specifications


Specifications : ASTM A-753 Alloy 4, MIL N-14411C Composition.

Mu metal is a 80 % Nickel, 4.5 % Molybdenum, balance Iron, soft ferromagnetic alloy which means that it does not retain a field after the removal of an external magnetizing force.

Mu-metal ® offers exceptionally high initial and maximum permeability with minimum hysteresis loss. It also has very low coercive force, very low core losses and a low remanence.

To reach the required magnetic performance mumetal needs to undergo a full final heat treatment in a dry hydrogen atmosphere furnace with a dewpoint of <-40 Deg C at 1100-1180 Deg C for 2-4 hours.This heat treatment increases the magnetic permeability by about 40 times.

The annealing process increases the mumetal ® grain size and hence the magnetic domains. However these enlarged grains are susceptible to severe shocks or further mechanical working and the permeability will decrease in these areas. This can be rectified by a re-anneal.

The high permeability of mumetal ® provides a low reluctance path for magnetic flux leading to its use in magnetic shields against DC and AC fields.

Typical Final Annealed Properties
Hardness : 120 Hv
Tensile Strength : 530 MPa
0.2 % Yield Strength : 160 MPa
Elongation : 45 %
Typical Magnetic Properties(DC) after final heat treatment
Permeability Mumax : 350000-500000
Saturation Induction : 0.76 T
Coercive Force : 0.6 A/m

These high levels of mumetal ® permeability compare to several thousand for ordinary steel


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