How SMCO Magnet And Neo Magnets Are Made

Update:15-03-2021
Summary:

  SmCo Magnet and Neo magnets-suitable raw materials ar […]

  SmCo Magnet and Neo magnets-suitable raw materials are melted in an induction melting furnace in a vacuum or inert gas. The molten alloy is either poured into a mold, on a cooling plate, or processed in a continuous strip caster-a device that forms a thin, continuous metal strip. These solidified metal "lumps" are crushed and pulverized into fine powders of 3 to 7 microns in diameter. This very fine powder is chemically reactive and can ignite spontaneously in the air, so exposure to oxygen must be avoided.

 

  There are several methods of compacting powder, all of which involve aligning the particles so that all magnetic areas in the final part point in a prescribed direction. The first method is called axial or lateral compression. Here the powder is placed in a cavity in the tool in the press, and the punch enters the tool to compress the powder. Immediately before compaction, the alignment field will be applied. Compaction "freezes" this alignment. In axial (parallel) compaction, the alignment field is parallel to the compaction direction. In lateral (vertical) compression, the field is perpendicular to the compaction pressure. Because the small powder particles are elongated in the magnetic alignment direction, lateral extrusion produces better alignment and therefore a higher energy product. Compacting the powder in a hydraulic or mechanical press limits the shape to a simple cross section that can be pushed out of the mold cavity.

 

  The second compression method is called isostatic pressing, in which a flexible container is filled with powder, the container is sealed, an alignment field is applied, and then the container is placed in an isostatic press. Use hydraulic fluid or a fluid such as water to apply pressure to the outside of the sealed container, compacting it evenly on all sides. The main advantage of making magnet blocks by isostatic pressing is that very large blocks can be made-often up to 100 x 100 x 250 mm, and because the pressure is applied equally on all surfaces, the powder maintains a good arrangement, resulting in a maximum The energy product.

 

  The pressed parts are packed in "boats" to be loaded into a vacuum sintering furnace. The specific temperature and the presence of vacuum or inert gas depend on the type and grade of magnets produced. Both rare earth materials are heated to the sintering temperature and densified. Another requirement of SmCo is to perform a "solid solution" treatment after sintering. After reaching room temperature, both materials undergo low temperature tempering heat treatment. During the sintering process, the magnet linearly shrinks by about 15-20%. The complete magnet has a rough surface and only approximate dimensions. They also have no external magnetic field.

 

  Finishing

 

  Sintered magnets are processed to a certain extent, and the range can range from smooth, parallel grinding, OD or ID grinding, or cutting of block magnets into smaller parts. The magnet material is brittle and hard (Rockwell C 57 to 61), it needs to be sliced ​​with a diamond grinding wheel and ground with diamond or a special grinding wheel. Slicing can be carried out very accurately, usually without subsequent grinding. All these processes must be carried out very carefully to minimize chipping and cracking.

 

  In some cases, the final magnet shape facilitates the use of formed diamond grinding wheels (such as arcs and loaves) for processing. Feed products with similar final shapes into the grinding wheel to provide precise dimensions. For small batch production of these complex shapes, HSMAG processing is usually used. Simple two-dimensional contours, EDM is faster, while more complex shapes using 3-5 axis machine tools run slower.

 

  Cylindrical parts can usually be formed by pressing axially, or they can be drilled and formed with block blanks. These longer cylinders (solid or cylinders with ID) can later be cut into thin washer-shaped magnets.

 

  For high-volume manufacturing (usually 5,000 pieces or more), manufacturing tools and producing shaped parts are usually more economical. For short-term operation or specific performance, it is best to machine magnets from blocks. When press-forming, material waste such as cutting chips is minimized. Order quantity, part shape, size and complexity will all determine which manufacturing method is preferable. Delivery time will also affect the decision, because manufacturing a limited number of products from stock blocks may be faster than ordering tools for moldable parts. Costing these options is not always straightforward. It is recommended to contact us to discuss options.

 

  Although these alloys can be used to make complex magnet shapes, these materials are most suitable for simpler shapes. Holes, large chamfers or slots are more expensive to produce. Tolerances are more difficult to maintain on more complex shapes, which may result in flux field changes and potential physical stress on parts in the power loss assembly.

 

  The processed magnet will have sharp edges and will easily break. Coating around sharp edges is also problematic. The most common way to reduce sharpness is a vibratory whetstone, commonly called vibratory tumbling, which is done in an abrasive medium. The required edge roundness depends on subsequent processing and processing requirements, but the most common radius is 0.005 inches to 0.015 inches (0.127 to 0.38 mm).

 

  New magnets that are prone to rust or chemical reactions are almost always coated. Mar cobalt is naturally more resistant to corrosion than new cobalt, but sometimes benefits from coatings. The most common protective coatings include dry spray epoxy, electronic coating (epoxy), electrolytic nickel, aluminum IVD, and combinations of these coatings. Magnets can also be coated with conversion coatings such as zinc, iron or manganese phosphates and chromates. The conversion film is usually sufficient for temporary protection, and can form a lower layer for epoxy coating or an upper layer for enhanced protection of aluminum IVD.

 

  Magnetizing

 

  After manufacturing, the magnet needs to be "charged" to generate an external magnetic field. This can be achieved in a solenoid (a hollow cylinder in which magnets of various sizes and shapes can be placed), or it can be achieved by a fixture designed with a unique magnetic pattern. It is also possible to magnetize large components to avoid handling and assembling these powerful magnets in a magnetized state. The magnetization field is very demanding. This is like many other aspects of magnet selection and should be discussed with our engineering and production teams.

 

  How to make m cobalt and new magnets

 

  Magnetic stability and calibration

 

  In some cases, the magnet will need to be stabilized or calibrated. Stabilization is the process of pre-processing the magnet (in or removed from the assembly) so that subsequent use will not cause additional loss of magnetic flux output. Perform calibration to narrow the performance output range of a set of magnets. These processes require high temperature treatment in an oven, or reverse pulse treatment in a magnetizer in a magnetic field lower than the full breakdown power. There are several factors that affect thermal stability, so it is important to control this process very carefully to ensure proper final product performance.

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