Type
Analysis
|
Element
|
Min
|
Max
|
|
Carbon
|
--
|
0.02
|
|
Nickel
|
80.0
|
|
Molybdenum
|
--
|
4.20
|
|
Iron
|
Balance
|
|
Silicon
|
--
|
0.35
|
|
Manganese
|
--
|
0.50
|
Description
HyMu 80 alloy is an unoriented, 80%
nickel-iron-molybdenum alloy which offers extremely high initial
permeability as well as maximum permeability with minimum hysteresis
loss.
Applications
HyMu 80 alloy has been used primarily
in transformer cores, tape wound toroids and laminations where
compactness and weight factors are important. It has also been used
for shielding to protect electrical components from stray magnetic
fields.
Corrosion
Resistance
This alloy is moderately resistant to
moisture and atmospheric corrosion.
Physical
Properties
|
Specific gravity ............................ 8.74
Density
lb/cu in ......................................... 0.316
kg/cu m ......................................... 8747
Thermal conductivity
Btu-in/ft²/hr/°F ................................. 240
W/m þ K ......................................... 34.6
|
Electrical resistivity
ohm c/mft ..................................... 349
microhm-mm ................................ 580
Temperature coefficient of
electrical resistivity
per °F (0 to 930°F) ................... 0.0006
per °C (-17.8 to 449°C) .............. 0.0011
|
Mean Coefficient of
Thermal Expansion
|
Test
Temparature
|
Coefficient
|
|
°F
|
°C
|
10(-6)/°F
|
10(-6)/°C
|
|
-103 to 77
-58 to
77
-11 to 77
77 to 122
77 to 212
77 to 392
77 to
572
77 to 752
|
-75 to 25
-50 to
25
-25 to 25
25 to 50
25 to 100
25 to 200
25 to
300
25 to 400
|
6.0
5.94
5.78
6.83
6.89
7.09
7.22
7.39
|
10.8
10.7
10.4
12.30
12.40
12.76
13.00
13.30
|
|
Curie temperature
°F ............................................. 860
°C ............................................ 460
Melting Point
°F............................................. 2650
°C............................................ 1454
|
Specific Heat
Btu/lb-°F ........................................... 0.118
kJ/kg-K ............................................. 0.494
|
Magnetic
Properties
|
Coercive Force
from H = 1.0 Oe,
Oersted.................... 0.008 to 0.02
|
Hysteresis loss
from H = 1.0 Oe, erg/cubic cm
per cycle................................ 18 to 24
|
DC Magnetic Properties
|
Form
|
Mu
at B = 40 G
|
Mu
max
|
Hc
from H = 1 Oersted
|
|
Bar, Wire
|
50,000
|
200,000
|
0.02 max
|
|
DC Hysteresis loss
from H = 1.0 Oe, erg/cubic cm
per cycle .................................. 16
Induction, gauss .................. 7300
|
Residual Induction, gauss
(Split strip or split
rod specimens) ................................. 3500
|
AC Magnetic Properties,
60 Hz
Minimum limits
|
Thickness
|
Mu
40 G
|
Mu
200 G
|
Mu
2000 G
|
|
Inches
|
Millimeters
|
|
0.025(1)
0.014(1)
0.006(1)
0.002(2)
|
0.635
0.356
0.152
0.051
|
35,000
55,000
65,000
70,000
|
40,000
65,000
85,000
90,000
|
55,000
95,000
135,000
220,000
|
Heat
Treatment
In-process anneal
To
relieve all strains and restore the alloy to a soft condition
suitable for drawing, spinning, forming, bending or similar
operations, anneal at 1450/1850°F (788/1010°C) for not more
than 1 hour. Since the high nickel, high permeability alloys readily
absorb carbon, sulfur, oxygen and other contaminants from combustion
furnace gasses, in-process annealing should be conducted in
dissociated ammonia, hydrogen, vacuum or inert gas atmospheres.
Hydrogen anneal
For
maximum softness and optimum magnetic and electrical properties, HyMu
80 alloy should be annealed in an oxygen-free, dry hydrogen
atmosphere with a dew point below -40°F at 2050/2150°F for 2
to 4 hours. Furnace cool to 1100°F. From 1100 to 700°F, cool
at rate between 350 to 600°F per hour.
Oil, grease, lacquer
and all other contaminants must be removed before annealing. The
individual parts should be seperated by an inert insulating powder
such as magnesium and aluminum oxide during hydrogen
annealing.
Vacuum heat treating can be employed. Generally, there
is some small sacrifice in magnetic properties compared to heat
treating in a dry hydrogen atmosphere.
Machining
The
following chart reports data compiled from various machining
operations performed on HyMu 80 alloy using the high-speed tool
materials indicated. When using carbide tools, double the sf/m shown
in the chart.
|
Operation
|
Speed
|
Feed
|
Tool
Material
|
|
sf/m
|
m/s
|
l/r
|
mm/r
|
|
Turning
Drilling
Milling
Tapping
|
50
35
40
10/15
|
0.254
0.18
0.20
0.05/0.08
|
0.0007/0.002
0.001/0.004
0.002/0.005
--------
|
0.018/0.051
0.025/0.102
0.051/0.127
--------
|
M42
M42
M2
M1
or M2
|
Figures used for all metal removal
operations covered are average. On certain work, the nature of the
part may require adjustment of the speeds and feeds. Each job has to
be developed for best production results with optimum tool life.
Speeds and feeds should be increased or decreased in small
steps.
HyMu 80 alloy machines somewhat like the austenitic
stainless alloys but doesn't work harden as rapidly. Gummy chips
develop in most machining operations. 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, then heat treated. High speed steel or carbide tools are
suggested for cutting operations.
Cold forming
For best
blanking characteristics, HyMu 80 alloy strip should be ordered in
the cold rolled condition (Rockwell B 90 minimum). For best forming
characteristics, strip should be ordered in the cold rolled and
annealed condition. For best drawing characteristics, strip orders
should be endorsed "annealed, deep draw quality".
Welding
HyMu 80 alloy is
readily welded by following the usual pracitices for ferrous alloys.
If a filler metal 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.
Shielding
Properties
Because of its very high permeability
and very low coercive force, HyMu 80 alloy is particularly well
suited for magnetic shielding applications.
Annealed, deep draw
quality strip can be fabricated into shields by bending, drawing and
spinning. Where joining is required, spot welding or tungsten
inert-gas welding can be used, with or without a base metal filler
rod.
To develop the best shielding characteristics, shields must
be annealed at 1900°F or higher (as described in the heat
treatment section) after all fabricating operations have been
completed. In general, higher annealing temperatures yield higher
permeability and better shielding characteristics.
To determine
its relative shielding capability, a material is evaluated as an
open-ended cylindrical shield in a uniform magnetic field, such as
that produced by a Helmholtz coil. When a pickup unit is centered in
the field of the coil, the attenuation (A) is the ratio of the
reading with no shield (E1)to that obtained when
a shield is positioned over the pickup (E2), with
its axis perpendicular to the field (A=E1/E2).
This
is a measure of the shielding effectiveness under the particular test
conditions, and for a given material depends upon the shield
thickness, its length-to-diameter ratio and the diameter of the
Helmholzt coil.
Typical
Mechanical Properties
Bar
|
Tensile
Strength
|
Yield
Strength
|
Proportional
limit
|
%
Elongation
|
%
Reduction
in
Area
|
Hardness
Rb
|
|
ksi
|
MPa
|
ksi
|
MPa
|
ksi
|
MPa
|
|
---------------------------------As
Cold Drawn----------------------------------
|
|
97
|
669
|
69
|
414
|
19
|
131
|
37
|
71
|
97
|
|
----------------As
Hydrogen Annealed at 2050°F(1121°C)-----------------
|
|
79
|
545
|
22
|
152
|
19
|
131
|
64
|
70
|
62
|
|
------------------After
Process Anneal at 1600°F(871°C)-------------------
|
|
90
|
620
|
33
|
228
|
28
|
193
|
57
|
74
|
85
|
|
Modulus
of Elasticity
(in tension)
|
Izod
Impact
|
|
10(3)ksi
|
10(6)MPa
|
ft-lb
|
J
|
|
---------------------------------As
Cold Drawn----------------------------------
|
|
33.7
|
232
|
120
|
163
|
|
----------------As
Hydrogen Annealed at 2050°F(1121°C)-----------------
|
|
33.3
|
230
|
85
|
115
|
|
------------------After
Process Anneal at 1600°F(871°C)-------------------
|
|
31.4
|
217
|
85
|
115
|
Strip
|
Tensile
Strength
|
Yield
Strength
|
Proportional
limit
|
%
Elongation
|
Hardness
Rb
|
|
ksi
|
MPa
|
ksi
|
MPa
|
ksi
|
MPa
|
|
---------------------------------As
Cold Rolled----------------------------------
|
|
135
|
931
|
--
|
--
|
--
|
--
|
4
|
100
|
|
----------------As
Hydrogen Annealed at 2050°F(1121°C)-----------------
|
|
77
|
531
|
21
|
145
|
15
|
103
|
38
|
58
|
|
------------------After
Process Anneal at 1600°F(871°C)-------------------
|
|
98
|
676
|
38
|
262
|
35
|
241
|
38
|
85
|
Application
Specifications
HyMu 80 alloy meets military
specification Mil-N-14411 B and ASTM-A-753-78 standard specification.
|
