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Sintered 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
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.

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 material.

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 specification.

                              

                                                                  

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