HyMu® 80

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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.

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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
Operation	sf/m	m/s	l/r	mm/r	Tool Material
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	% Elongation	% Reduction in Area	Hardness Rb
---------------------------------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	% Elongation	Hardness Rb
---------------------------------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.