alnico magnets are manufactured by a powder
metallurgy process, which utilises controlled
atmosphere high temperature sintering to produce
near net shape parts. These may range in size
from as little as 0.05g up to 150g.
The careful control of the raw materials and
the semi-automated production process guarantees
that a narrow spread of magnetic performance and
physical dimensions can be assured. This control
enables adjustment of materials and processing
to produce both a standard range of magnetic
properties or individually tailored alloys to
meet customer specific requirements.
In comparison with other permanent magnet
materials, the alnico magnets produced by this
route are characterised by:
- near full density
- fine crystalline metallic structure
- very high temperature stability
- good corrosion resistance
- high mechanical strength.
Processing begins with the controlled blending
of fine metal powders consisting primarily of
aluminium, 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 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 specialised 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 stabilises the
To achieve very high dimensional control
specific surfaces can be machined to very close
tolerances using high volume grinding machines.
Final inspection before despatch or
subsequent assembly, ensures that all parts
conform both physically and magnetically to