Cast Alnico Permanent Magnet

General Information


Excellent temperature stability,high residual induction,and
relatively high energies characterize Alnico materials,composed
primarily of alloys of Aluminum,Nickel,and Cobalt.They are
manufactured through either a casting or sintering process.


Cast magnets may be manufactured in complex shapes,such as horseshoes,not possible with other magnet materials.Sintered Alnicos offer
slightly lower magnetic properties but better mechanical characteristics
than cast Alnicos.Cast Alnico 5 is the most commonly used of all the
cast Alnicos.This material is used extensively in rotating machinery,meters,instruments,sensing devices,and holding applications,to name a
few.


Alnico is hard and brittle.Machining or drilling can not therefore be
accomplished by ordinary methods.Holes are usually cored in at the
foundry,and magnets are cast close to final size and then finish
machined to closer tolerances.


Alnico has a low coercive force,and is easily demagnetized if not
handled with care.For optimum performance of Alnico 5,the magnetic
length should be approximately 5 times the pole diameter or equivalent
diameter.For example,a 0.250" diameter magnet should be about 1.250"
long.


Because of its higher coercivity,Alnico 8 may be used in shorter lengths and in disc shapes.


Manufacturing Methods


Alnico magnets are manufactured through either casting or sintering processes.


Cast magnets are manufactured by pouring a molten metal alloy into a mold and then
further processing it through various heat-treat cycles.The resulting
magnet has a dark gray exterior appearance,and may have a rough
surface.Machined surfaces have a shiny appearance similar to steel.


Sintered magnets are manufactured by compacting fine Alnico powder in a press,and then sintering the compacted powder into a solid magnet.


Assemblies


We are able to manufacture metal and other components of finished sub assemblies using our CNC machining facilities.


Assemblies can be fabricated by adhering magnets with adhesives to suit
a range of environments,by mechanically fastening magnets,or by a
combination of these methods.Due to the relatively brittle nature of
these magnet materials,press fits are not recommended.


Surface Treatments


The corrosion resistance of Alnico is considered excellent ,and no
surface treatments are required.However,Alnico magnets are easily
plated for cosmetic reasons if required.


Machining


Alnico is hard and brittle,and prone to chipping and cracking.Special
machining techniques must be used to machine this material.Holes must
be made by EDM methods.We are fully equipped to machine these materials
to your blueprint specifications.


Magnetizing and Handling


Alnico magnets require magnetizing fields of about 3 kOe.Because of
their relatively low coercivities,special care should be taken to
assure that these magnets are not subjected to adverse repelling fields,since these could partially demagnetize the magnets.Magnetized magnets
should be stored with eepers? to reduce the possibility of partial
demagnetization.If Alnicos are partially demagnetized,they may be
easily remagnetized.


Temperature Effects


Up to about 1,000 F,changes in magnetization are largely reversible
and re-magnetizable,while changes above this are largely structural and
not fully reversible or re-magnetizable.Approximately 90% of room
temperature magnetization is retained at temperatures of up to 1,000 F.


Magnetic Properties of Cast AlNiCo:

Grade	Remanence Br		Normal Coercivity Hcb		Intrinsic Coercivity Hcj		Max.Energy Product (BH)max		Density ρ
	mT	Gs	KA/m	Oe	KA/m	Oe	KJ/m3	MGOe	g/cm3
	Nominal
CLN9	680	6800	30	380	32	400	9.0	1.13	6.9
CLNG10	600	6000	40	500	43	540	9.6	1.02	6.9
CLNG12	700	7000	40	500	43	540	12.0	1.50	7.0
CLNG16	780	7800	52	650	54	680	16.0	2.00	7.0
CLNG34	1200	12000	44	550	45	560	34.0	4.30	7.3
CLNG37	1200	12000	48	600	49	610	37.0	4.63	7.3
CLNG40	1250	12500	48	600	49	610	40.0	5.00	7.3
CLNG44	1250	12500	52	650	53	660	44.0	5.50	7.3
CLNG52	1300	13000	56	700	57	710	52.0	6.50	7.3
CLNGT28	1300	13000	58	720	59	740	28.0	3.50	7.3
CLNGT32	1000	10000	100	1250	102	1280	32.0	4.00	7.3
CLNGT38	800	8000	110	1380	112	1400	38.0	4.75	7.3
CLNGT60	900	9000	110	1380	112	1400	60.0	7.50	7.3
CLNGT72	1050	10500	112	1400	114	1430	72.0	9.00	7.3
CLNGT36J	700	7000	140	1750	148	1850	36.0	4.50	7.3

Physical Properties of Cast AlNiCo:

Curie Temperature Tc	860℃
Max Operating Temperature	525-550℃
Specific Resistance	47-54Ω-cm
Hardness	520-630
Recoil Permeability	1.70-4.70 Gs/Oe
Tem.Coefficient	-0.025 ~ -0.02%/C
Tem.Coefficient of Inturensic Coerrice Induction	+0.01 ~ +0.03/℃

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