AlNiCo Ring Magnets

AlNiCo ring magnets can be made using either casting or sintering processes. The sintering process allows for the production of ring magnets that are near net-shape, requiring minimal additional machining. However, sintered AlNiCo magnets have limited dimensional applicability and are generally used for small-sized or thin-walled ring magnets.

Cast AlNiCo magnets are coarse-grained, hard, and brittle, making them unsuitable for ordinary machining techniques, especially drilling. Holes with lower precision are typically rough cast during the foundry stage, and the magnets are cast close to their final size. Further machining is done to achieve the necessary tolerances. For holes requiring high precision and for grain-oriented ring magnets (such as those with columnar or semi-columnar crystal growth), wire-cutting or grinding is used to meet the desired specifications.

Some AlNiCo magnets are isotropic, meaning they can be magnetized in any direction. However, most commercial AlNiCo magnets are anisotropic, meaning they are oriented with a preferred direction of magnetization. This orientation is developed during the heat treatment cycle of cast and sintered AlNiCo magnets, which occurs after the shape has been formed. During heat treatment, the magnets are heated to a target temperature and cooled in the presence of an alignment or orientation magnetic field.

Once magnetized, it is essentially impossible to magnetize the resulting anisotropic AlNiCo magnets in any direction other than the preferred orientation. However, various pole configurations can be achieved without conflicting with the magnet’s orientation.