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Mumetal alloy for magnetic shielding devices

Mu metal has been being used by metal producers, suppliers, engineers, scientists and others for many decades as an industrial standard product. Mumetal is used in a low frequency magnetic shielding design, calculation, assessment, production and supply. It is widely produced in stress annealed form that permits further production, stamping or welding. Subsequent to fabrication, grains structure is enhanced by perfection annealing to remove stress in the material hence providing bigger grain structure, softer temper and ultimate shielding properties.

The ultimate annealing is a crucial finishing procedure for the maximum attenuation of field lines. Heanjia Super-Metals gives perfection annealing in dry hydrogen conditions.

Properties of Annealed Mumetal

Yield strength, 49 ksi 33 Mpa
Density 0.316 lb/inch3 or 8.25 g/cm3
Tensile strength 99 ksi or 682 Mpa
Electrical resistivity 47 micro-ohm cm
Elongation 32% in 2 inch 51 mm
Grain size ASTM 7 or finer
Stress annealed hardness 15T 85

Magnetic properties of Mumetal

DC µ at 40 80,000 gauss
DC µ at 100 105,000 gauss
DC µ highest 350,000
DC Hc 0.005 Oe
DC br 4000 gauss
AC 60 Hz µ at 40 gauss 65,0000

Through composition and annealing, MuMetal receives essential electromagnetic shielding properties and extremely high magnetic permeability- absorbs magnetic energy. The exclusive characteristics of this alloy offer the maximum feasible attenuation, making it the best material for choosing to decrease low frequency electromagnetic interference.

MuMetal is called as an industrial reference material with nominally different properties than other alloys.

Mumetal puts off magnetic regions from approaching the areas where magnetic interference is not required, magnetic shielding is employed enclosing the source of interference to avoid electromagnetic radiation from leaving an apparatus or normally surrounding a sensitive apparatus, to avoid the electromagnetic interference (EMI) from disrupting normal operations.

There is not a common material to prevent magnetic fields without itself get attracted to magnetic force. Magnetic fields can be redirected. For this, the high permeability shielding alloys such as Mu Metal are employed. The magnetic lines are significantly attracted towards the shielding material.

Mumetal in Zero Gauss Chambers

Mumetal zero gauss chambers are extensively used by educational agencies, research bodies and laboratories to give an indication for military or consumer regulatory purposes. Zero gauss chambers are suitable for layering. When two or more concentrically spaced magnetic shields are employed in series, the external field is decreased by every layer by 25 to 40 times.

These chambers consist of triple layers of mumetal and are made to decrease the external fields by 15 x 10(3) to 60 x 10(3) times. Following the standard configuration, each three magnetic shield layers include a cylinder with a close and open end. The close fitting and removable cover are available on the access opening end. Among all geometrical shapes, a cylindrical shape is the best for reducing outer magnetic flux strength, hence producing a suitable magnetic shielded region.

Annealing Mumetal

Mumetal’s annealing is extremely necessary to receive the required magnetic properties. The furnace condition and temperature and annealing period are essential factors to consider. The suitable characteristics are received in a pure and arid hydrogen condition. Broken ammonia offers suitable outcomes in the regular furnaces, as provided by a vacuum condition in the batch operations. Suitable magnetic characteristics of MuMetal materials are received through annealing at 2050oF or 1121oC for 4 hours. Quenching at the rate of 400oF or 222oC per hour as long as approach to 1100oF or 600oC, subsequently cooling rate can be increased. MuMetal shields can be subjected to normal condition at 600oF or 315oC.  To prevent wide distortion of light gauge shields, annealing temperature up to 1950oF or 1065oC will give suitable magnetic characteristics. Apparently, magnetic analyses may show that an increasing quenching rate can be followed without poor effect.

The complete annealing procedure, necessary for suitable magnetic feature, may cause deformation of the formed components as the process stresses are removed. The resizing of components may be needed. However magnetic shields are in a dead soft condition after annealing,, the shields are normally to produce a stronger component in the group. Annealing almost doubles the attenuation.

 Mumetal has been employed for several years in many NASA satellite and aerospace operations, American Naval and other army operations, aviation and telecommunication systems.