Soft Magnetic Alloys and Their Properties

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NiFe (Nickel Iron) alloys Magnetic & Chemical Properties:

Magnetic & Chemical Properties
No. Properties Measurement Unit 80% NiFe7 Mumetal7 48% NiFe8 Si Steel Fe-49%
Co-2%V
1 DC Magnetic Properties Bs Tesla 0.751 0.761 1.53 1.739 2.25(11)
Br Tesla 0.42 0.52 1.13 - 1.3
B at 100 A/m Tesla - - 1.2 - -
Hc 2 A/m 0.35 0.6 2.8 -  40 to
160(12)
µ4 4 - 550000 120000 - - -
µ max - 570000 350000 190000 - 18000
2 60Hz AC Magnetic Properties µ4z5 - 70000 50000 10400 >2500 1200
µz86 - - - 54000 - -
µ max - 95000 95000 - - 12000
Core loss W/Kg 0.015 0.015 0.4 3.910 2.3 to 3.0(13),
3.8 to 5(14)
3 Chemical Composition Ni % 78-81 78-81 47-48 Nil -
Mo % 4.5-6 4.5-6 Nil Nil -
Si % 0.05-0.4 0.05-0.4 0.1 1.6 - 2.1 -
Mn % 0-0.5 0-0.5 0.50 0.5 -
C % 0.01 0.01 0.005 0.01 -
Co % - - - - 49
V % - - - - 2
Fe % Balance Balance Balance Balance Balance

Physical Properties:

Physical Properties
No. Properties Measurement Unit 80% NiFe7 Mumetal7 48% NiFe8 Si Steel Fe-49%
Co-2%V
4 Physical Properties Density g.cm-3 8.7 8.7 8.2 7.75 8.12
specific Heat J.Kg-1.˚C-1 460 460 500 - 460
Thermal conductivity W.m-1.˚C-1 19 19 13 - 33
Mean CTE between -50 & +200˚C ˚C-1 12.10-6 12.10-6 8 x 10-6 - 9.7 x 10-6
Electrical resistivity µΩ.cm 60 60 45 - 40
Curie Point ᵒC 420 420 450 - 950
Coefficient of magnetostriction at Saturation ∆l / l - 1-3 x 10-6 1-3 x 10-6 24 x 10-6 - 70 x 10-6
Melting temperature ᵒC 1450 1450 1425 - 1480
Hardness(Cold Worked) Hv 325 325 250 - 400
UTS(Cold Worked) MPa 1050 1050 850 - 1200
0.2% PS(Cold Worked) MPa 1030 1030 820 - 1150
Elongation(Cold Worked) % 3 3 3 - 2
Hardness(Annealed) Hv 160 160 140 155 220
UTS(Annealed) MPa 650 650 500 380 480
0.2% PS(Annealed) MPa 280 280 250 250 300
Elongation(Annealed) % 35 35 40 min 30 4.5
Grain Size(Annealed) - 8 8 9 - -
Hardness(Finished Part) Hv 110 110 100 - -
UTS(Finished Part) MPa 530 530 450 - -
0.2% PS(Finished Part) MPa 160 160 200 - -
Elongation(Finished Part) % 45 45 35 - -
Grain Size(Finished Part) - 0-3 0-3 0 - -

Key:

  1. Practical saturation Bs measured for H = 800 A/m.
  2. Remanent induction Br and coercive field Hc measured from H = 80 A/m.
  3. Practical saturation Bs and Remanent induction Br measured for H = 800 A/m.
  4. Measured for H = 4 mA/cm (peak value).
  5. Sinusoidal excitation field H = 4 mA/cm (peak value).
  6. Impedance permeability for B = 0.8 T.
  7. Measurements made on 35X26X0.34 mm ring specimens after annealing in Pure
    & Dry Hydrogen for 4h at 1170°C followed by cooling at 200°C/h.
  8. Measurements made on 36X25X0.34 mm ring specimens after annealing in Pure
    & Dry Hydrogen for 4h at 1150°C.
  9. Practical saturation Bs measured for H=5000A/m.
  10. Core loss W/kg at 1.5T at 50Hz=3.90 max.
  11. Practical saturation Bs measured for H=8000A/m.
  12. Depends on annealing cycle (Optimizing magnetic or mechanical property)
  13. AT B=1.5T & 50Hz
  14. AT B=2.0T & 50Hz

FAQ for Materials

Q.1. What effect does heating the magnetic material have?
  • Ans. Magnetic materials properties are temperature dependent. When temperature rises the magnetic interaction in the materials reduces due to thermal energy enhancement. When thermal energy overcomes the magnetic energy , magnetic property will reduce drastically or become zero.
Q.2. What is MuMetal? Where can it be used?
  • Ans. MuMETAL®, Co-NETIC® AA and other shielding alloys, offer important electromagnetic field shielding characteristics, including very high magnetic permeability - its ability to absorb magnetic energy. The unique properties of this family of alloys results in the highest possible attenuation, making these shielding alloys the materials of choice for reducing low-frequency electromagnetic interference (EMI).
Q.3. Why is Mu Metal offered?
  • Ans. MuMETAL® is an industry reference material, with different characteristics than proprietary alloys. MuMETAL® meets specs 1J79, MIL-N-14411C Composition 1 and ASTM A-753 Alloy 4. When the specification or the application calls for a magnetically soft or high permeability material, MuMETAL® can frequently be successfully applied.
Q.4. Why must MuMetal® alloy be final annealed to develop magnetic shielding performance?
  • Ans. To obtain optimum magnetic properties, annealing MuMetal® alloy following fabrication is essential. This should be done in a furnace that allows for careful control of the annealing temperature and cooling rate. Optimum properties are reached in a pure hydrogen atmosphere.
Q.5. Why does MuMetal or Co-Netic not be used at cryogenic temperature?
  • Ans. High permeability MuMETAL® and Co-NETIC® alloys have an optimal temperature range in which the permeability peaks. The permeability of these alloys begins to drop below -40°C, making it unsuitable in low temperature applications.
Q.6. What are the limitations on using Cobalt Iron material?
  • Ans. The main limitation of the material is its high core loss at 50 Hz when compared with other soft magnetic materials.
Q.7. Why is coating required for parts made from SiFe material?
  • Ans. SiFe materials are more prone to corrosion hence, to avoid corrosion, rusting or oxidation, coating is highly recommended for SiFe materials based components

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