Cast AlNiCo Magnets

AlNiCo, an abbreviation for Aluminum-Nickel-Cobalt, is a non-rare earth metallic permanent magnet material composed primarily of Aluminum, Nickel, Cobalt, and Iron. AlNiCo magnets dominated the permanent magnet industry until the emergence of rare earth permanent magnets. The production of AlNiCo magnets employs two main methods: sintered AlNiCo magnets and, more prevalently, cast AlNiCo magnets, each suited to particular applications.

Cast AlNiCo magnets are produced by pouring molten AlNiCo alloy into a resin-bonded sand mold, followed by processing through various heat treatment cycles. The finished product features a dark gray or black exterior with a rough texture, though machined surfaces exhibit a smooth, bright metallic appearance.

Notably, cast AlNiCo magnets can deliver significantly higher magnetic performance compared to their sintered counterparts. Cast AlNiCo 5, the most commonly used grade among AlNiCo magnets, can typically provide energy to a magnetic circuit more economically than any other grades.

AlNiCo magnets feature various trade names for designating their grades, such as Columax, Alcomax, Hycomax, Ticonal, and others.

Most individuals are familiar with AlNiCo magnets through MMPA class designations, including Alnico 2, Alnico 3, Alnico 5, Alnico 5DG, Alnico 8, Alnico 8HC, and Alnico 9. AlNiCo grades differ in cobalt content, ranging from zero (Alnico 3) to 40% (Alnico 8). Lower grades (2, 3, and 4) are unoriented, exhibiting isotropic magnetic properties and thus relatively low magnetic output. In contrast, anisotropic grades (5, 6, 8, and 9) are engineered to deliver high magnetic output in a designated direction.

The Chinese nomenclature system assigns cast AlNiCo magnets with the prefixes LNG or LNGT, followed by a number. These letters LNGT represent the Chinese phonetic abbreviations for Aluminum, Nickel, Cobalt, and Titanium, respectively. The subsequent number denotes the minimum value of the maximum energy product (BH)max in the SI unit of kJ/m³. A letter J added at the end indicates high coercivity.