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How are Neodymium Magnets Made?

Posted on April 14, 2017

Armstrong Neodymium Magnets

As neodymium magnets provider, not only do we stock large selection in different sizes, shapes and grades, we also manufacture custom magnets to meet customers’ design criteria. So, what kind of process steps are involved in making these permanent magnets?

1. Neodymium magnets are Nd2Fe14B compounds. Thus, we need to source all the rare-earth ingredients like neodymium, iron and boron extracted through metallurgical process. For different grades, different proportions are combined and small portions of other elements are inserted. For instance, add cobalt to achieve higher temperature property or dysprosium to increase intrinsic coercivity.

2. The rare-earth elements are melted with electric currents in a vacuum induction furnace to form alloy ingots which are then crushed, milled, pulverized or ground into a fine powder (3-7 microns in diameter) and mixed. This is an important step as the composition and mixture of the alloys critically determine the magnet’s strength, grade and other characteristics.

3. The well-mixed powder is pressed tightly into block shapes in dies at 725oC and the magnetization orientation is assigned in the same direction as the pressing direction. It is noted that this step does not activate their magnetism or provide them with attractive or repelling capabilities.

4. The pressed magnetic particles then go through a sintering process which locks up the alloy mixture by heating them at 1080oC to be strong enough for adherence yet not liquified. Under such elevated process temperature, the magnet would shrink from their pressed form.

5. The sintered magnets then undergo through machining which defines the magnets to the sizes and shapes specified by our customers. Due to their brittle natures, there are limitations to the complexity of the magnet shapes and thin magnets are generally not achievable. For large volumes, it is generally more economical and error-free to make the exact shaped dies, and would minimize the material waste from machine grinding.

6. To prevent corrosion through oxidation and losing magnetic properties in moist environment, individual neodymium magnets are electro-plated. The most commonly requested plating is nickel-copper-nickel.

7. Use a magnetizer with a wire coil to activate their magnetism by creating a large voltage supplied by a set of capacitors. It sends a quick yet powerful current to create a strong magnetic field.

8. Last but not least, we carefully inspect the final products for their key properties. We randomly select a set of magnets and use a digital measuring projector to verify their dimensions, use hysteresigraph to measure and plot out the B-H Curve, which confirms the magnets’ remanence, coercive force and many more magnetic property values.

Every single step must be strictly followed one after another and cannot be skipped or swapped. They must be precisely carried out with professional details which can be time consuming and cannot be shortened. Our production team runs 7 days a week to provide the fastest lead time (6-8 weeks) in the industry.