MuShield Magnetic Shielding
MuShield Magnetic Shielding MuShield Magnetic Shielding
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Useful Information for Designing Your Own Magnetic Shielding

MuShield high permeability magnetic shielding material is a non-oriented 80% nickel-iron-molybdenum alloy which offers extremely high initial permeability and maximum permeability with minimum hysteresis loss.

It meets military specification MIL-N-14411 and ASTM A-753 standard specification.
DC MAGNETIC PROPERTIES
Coercive force from H=1.0 Oe, Oersted 0.008 to 0.02
Hysteresis loss from H=1.0 Oe, erg/cm3 per cycle 18 to 24
DC MAGNETIC PROPERTIES
Form µ at B = 40 G µ max Ho from H=1 Oersted
Bar, Wire 50,000 200,000 0.02 max.
DC hysteresis loss from
  H = 1 Oe, erg/cm3 per cycle . . . 16
Induction, gauss . . . . . . . . . . . . 7,300
Residual Induction, gauss . . . . 3,500
  (Split strip or split rod specimens)


AC MAGNETIC PROPERTIES, 60 Hz
Minimum Limits
Thickness
in.          mm
µ 40 G µ 200 G µ 2000 G
0.0251 0.635 35,000 40,000 55,000
0.0141 0.356 55,000 65,000 95,000
0.0061 0.152 65,000 85,000 135,000
0.0022 0.051 70,000 90,000 220,000
1 Ring laminations 1 1/2" (38.1 mm)
   OD x 1" (25.4 mm) ID specimens
2 Tape toroid specimen
PHYSICAL PROPERTIES:
Specific gravity 8.74
Density -- lb/in3 0.316
                kg/m3 8747
Thermal conductivity  
    Btu-in/ft2/hr/°F 240
    W/m· K 34.6
MuShield Magnetic Shielding Material
Type analysis:
Carbon 0.02%      Nickel 80.00%
Manganese 0.50% Molybdenum 4.20%
Silicon 0.35% Iron Balance
Electrical Resistivity
    ohm-cir mil/ft 349
    microhm-mm 580
Temperature coefficient of electrical resistivity
    per °F from 0/930°F 0.0006
    per °C from -17.8/499°C 0.0011
Curie temperature 860°F (460°C)
Melting point 2650°F (1454°C)
Specific heat, Btu/lb · °F 0.118
                          kJ/kg · K 0.494
COEFFICIENT OF THERMAL EXPANSION
Temperature   Coefficient
°F °C 10 -6 /°F 10 -6 /°C
-103 to 77 -75 to 25 6.00 10.80
-58 to 77 -50 to 25 5.94 10.70
-11 to 77 -25 to 25 5.78 10.40
77 to 122 25 to 50 6.83 12.30
77 to 212 25 to 100 6.89 12.40
77 to 392 25 to 200 7.09 12.76
77 to 572 25 to 300 7.22 13.00
77 to 752 25 to 400 7.39 13.30

Heat Treatment

Hydrogen anneal: For optimum magnetic and electrical properties, MuShield anneals finished parts in an oxygen-free dry hydrogen atmosphere with a dew point below -40° F (-40° C) for two to four hours at 2050° F (1121° C) to 2150° F (1177° C). Furnace cool to 1100° F (593° C) from 1100/700° F (593/371° C), cool at a rate between 350° F (194° C) and 600° F (334° C) per hour. Oil, grease, and all other contaminants must be removed before annealing. If required, individual parts may be separated by an inert insulating powder such as magnesium or aluminum oxide during the hydrogen annealing process.

Shielding Properties

MuShield Magnetic Shielding Materials. Because of its very high permeability and very low coercive force, MuShield's materials are particularly well suited for magnetic shielding applications. "Annealed, Deep Drawn Quality" strip can be fabricated into shields by bending, drawing or spinning: where joining is required, spot welding or tungsten inert gas welding "TIG" welding -- with or without a base metal filler rod -- can be used. To achieve the best shielding characteristics, components must be annealed at 2050° F or higher as described under Heat Treatment. This is performed after all fabricating operations have been completed. In general, higher annealing temperatures yield higher permeability and better shielding characteristics.

Workability

Machining: High Perm Material machines somewhat like austenitic stainless alloys and develops gummy chips, but it does not work harden as rapidly as the stainless alloys. Work hardened bars (Rockwell B 90 minimum) offer the best machining characteristics. Lard oil should be used for drilling and machining operations which must be done at slow speeds. If sulfur-bearing and water-soluble cutting compounds are used, the parts should be thoroughly cleaned within 48 hours and heat treated. High-speed steel or carbide tools are suggested for cutting operations.

Cold Forming: For best blanking characteristics, strips should be purchased in the cold rolled condition Rockwell B 90 minimum. For best forming characteristics, strips should be purchased as cold rolled annealed. For best drawing characteristics, strips should be purchased as annealed, Deep Drawn Quality.

Welding: High permeability materials are readily welded by following the usual practices for ferrous alloys.

If a filler material is required, use the same analysis. Finish annealed parts can be soft or hard soldered.

Do not Braze or solder prior to final heat treatment.
REFERENCES FOR MACHINING
Operation Speed* Feed Tool
  sf/m m/s i/r mm/r Materials
Turning 50 0.254 0.0007/
0.002
0.018/
0.051
M42
Drilling 35 0.18 0.001/
0.004
0.025/
0.102
M42
Milling 40 0.20 0.002/
0.005
0.051/
0.127
M2
Tapping 10/15 0.05/
0.08
- - - - M1 or M2
*For carbide tools, double the sf/m

MECHANICAL PROPERTIES
BAR
  As Cold Drawn As Hydrogen Annealed at 2050° F
(1121° C)
After Process Anneal at 1600° F
(871° C)
Tensile Strength, ksi 97 79 90
   MPa 669 545 620
Yield point, ksi 69 22 33
   MPa 414 152 228
Proportional limit, ksi 19 19 28
   MPa 131 131 193
Elongation % 37 64 57
Reduction of area, % 71 70 74
Modulus of elasticity in tension
   103 ksi
33.7 33.3 31.4
   106 MPa 232 230 217
Rockwell B hardness 97 62 85
Izod impact, ft-lbs 120 85 85
   J 163 115 115
STRIP
  Cold Rolled As Hydrogen Annealed at 2050° F
(1121° C)
After Process Anneal at 1600° F
(871° C)
Tensile strength, ksi 135 77 98
   MPa 931 531 676
Yield point, ksi   21 38
   MPa   145 262
Proportional limit, ksi   15 35
   MPa   103 241
Elongation % 4 38 38
Rockwell B hardness 100 58 85


CORROSION RESISTANCE:
High Perm Material is moderately resistant to moisture and atmospheric corrosion.