Alnico2022-02-18T06:57:02+00:00

Temperature resistant, medium strength magnets

Alnico magnets are extremely resistant to elevated temperatures, and have relatively high energy products. They are made primarily from alloys of aluminum, nickel, and cobalt, and may be either cast or sintered. Standard grades are Alnico 5 and Alnico 8.

Cast alnico is melted and then poured and cooled in a mold to produce the desired shape. Once cooled, the magnet is then ground and heat treated. This process can be done in the presence of a magnetic field, which creates a stronger, anisotropic magnet which is oriented in a specific direction.

Sintered alnico magnets, while slightly weaker than cast material, exhibit superior mechanical characteristics.

Sintered alnico magnets are manufactured using a powder metallurgy process which uses controlled atmosphere, high temperature sintering to produce near net shape parts. Semi-automated production enables adjustment of materials, and processing allows either a standard range of magnetic properties or individually tailored alloys to meet customer specifications.

Alnico magnets have recently been replaced with sintered neodymium or injection molded magnets in many applications.

  • Very resistant to high temperatures

  • Working temps over 1000° F

  • Higher energy product than ceramic magnets

  • Lower coercive strength – easier to demagnetize than ceramic and rare earth

  • Available cast or sintered

PROCESS FLOW DIAGRAM
Cast Alnico

RAW MATERIAL
Goods Inwards Inspection
ALLOY MIXING
MELT ALLOYS
POUR-SHAKE-SNAG-GRIND
SOLUTION TREATMENT
Homegenization
FIELD
ALIGNMENT
TEMPERING
GRINDING
INSPECTION
ASSEMBLY
MAGNETIZING
packing and dispatch

ALNICO Magnetic Material Characteristics

Sintered Alnico Magnets

Download this data in PDF format: EAM-Sintered-Alnico-Properties.pdf – 66kb

Material & Grade Max. Energy Product Remanence Coercive Force Rev. Temp. Coefficient Curie Temp. Density
(BH) max Br Hc Hci % / °C Tc D
MGOe kJ/m3 kG mT Oe kA/m Oe kA/m % / °K °C g/cm3
Alnico 2 1.5 12.0 7.1 710 550 44 570 45 -0.014 810 7.0
Alnico 5 3.9 31.2 10.5 1050 590 47 600 48 -0.016 810 6.9
Alnico 6 3.0 23.8 10.0 1000 700 56 710 57 -0.020 860 7.3
Alnico 8 4.0 32.0 8.0 800 1550 123 1600 128 -0.020 860 7.3
Alnico 8HC 4.5 36.0 6.5 650 1700 136 1880 150 -0.020 860 7.3

Cast Alnico Magnets

Download this data in PDF format: EAM-Cast-Alnico-Material-Properties.pdf – 67kb

Material & Grade Max. Energy Product Remanence Coercive Force Rev. Temp. Coefficient Curie Temp. Working Temp. Density
(BH) max Br Hc Hci Br Hci Tc Tw D
MGOe kJ/m3 kG mT Oe kA/m Oe kA/m % / °C °C g/cm3
Alnico 2 1.6 12.8 7.0 700 580 47 600 48 -0.03 -0.02 810 450 7.0
Alnico 3 1.2 10.0 6.0 600 480 38 500 40 -0.03 -0.02 810 450 6.9
Alnico 5 5.0 40.0 12.5 1250 640 51 640 51 -0.02 -0.02 860 525 7.3
Alnico 5DG 6.5 52.0 13.0 1300 680 55 700 56 -0.02 -0.02 860 525 7.3
Alnico 5-7 7.5 60.0 13.5 1350 740 59 740 59 -0.02 -0.02 860 525 7.3
Alnico 6 3.5 28.0 10.0 1000 720 58 720 58 -0.02 -0.02 860 525 7.3
Alnico 8 5.0 40.0 8.0 800 1480 119 1500 120 -0.025 -0.02 860 550 7.3
Alnico 8B 5.5 44.0 8.5 850 1550 124 1550 124 -0.025 -0.02 860 550 7.3
Alnico 8HE 6.0 48.0 9.0 900 1500 120 1500 120 -0.025 -0.02 860 550 7.3
Alnico 8HC 4.5 36.0 7.0 700 1880 151 1900 152 -0.025 -0.02 860 550 7.3
Alnico 9 9.0 72.0 10.5 1050 1400 112 1400 112 -0.025 -0.02 860 550 7.3

CAST ALNICO – 2 & 3 DEMAGNETIZATION CURVES

CAST ALNICO – 5 & 6 DEMAGNETIZATION CURVES

CAST ALNICO – 8 & 9 DEMAGNETIZATION CURVES

SINTERED ALNICO-8 DEMAGNETIZATION CURVE

SINTERED ALNICO-2, 5 & 6 DEMAGNETIZATION CURVES

PROCESS FLOW DIAGRAM
Cast Alnico

RAW MATERIAL
Goods Inwards Inspection
ALLOY MIXING
MELT ALLOYS
POUR-SHAKE-SNAG-GRIND
SOLUTION TREATMENT
Homegenization
FIELD
ALIGNMENT
TEMPERING
GRINDING
INSPECTION
ASSEMBLY
MAGNETIZING
packing and dispatch

PROCESSING SINTERED ALNICO

Processing begins with the controlled blending of fine metal powders consisting primarily of aluminum, nickel, cobalt and iron.

A wax lubricant is added at this stage to aid the subsequent pressing process.

The mixed powder is then compacted to form the required shape using varied press technology. Close dimensional control is maintained by statistical process control (SPC), both at this stage and after sintering.

De-waxing through a low temperature furnace removes the pressing lubricant prior to sintering.

Sintering is undertaken at high temperature under a protective atmosphere of hydrogen. An homogeneous fully dense alloy results.

Further heat treatment is required for most alloys to introduce improved magnetic properties. Anisotropic properties can be induced by additional specialized heat treatment. For those materials that have been heat treated, the final part of the process is multi-stage tempering which reduces brittleness but more importantly, further enhances the magnetic performance and stabilizes the material.

To achieve very high dimensional control specific surfaces can be machined to very close tolerances using high volume grinding machines.

Final inspection before dispatch or subsequent assembly, ensures that all parts conform both physically and magnetically to specification.

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