The most well-known legend of the discovery of magnets dates back to 4,000 years ago in Northern Greece. According to the legend, a shepherd named Magnes was herding his sheep when suddenly the nails in his shoes and the metal on his staff stuck to the large black rock he was standing on. The curious shepherd dug into the earth and uncovered lodestones, which contain a natural magnetic material we know as magnetite. Lodestones were later named magnetite after Magnes himself.
Fast forward to present day, magnetic materials have become indispensable to modern culture. More than just a refrigerator decoration, they are used in a large array of industrial and medical equipment, exist as components in almost all electronic devices, and have even become their own form of health therapy.
Most metals with magnetic properties are ferrous: metals and alloys that contain iron. These ferrous metals include mild steel, carbon steel, stainless steel, cast iron, and wrought iron. Their high carbon content leads to being prone to rust (with the exception of stainless steel and wrought iron), but their tensile strength and durability make ferrous metals popular in large-scale construction projects, transportation, and many industrial applications. Likewise, their magnetic property is widely used in the creation of electrical appliances and motors.
Galvanizing is the process of applying a protective zinc coating to steel in order to it prevent rusting. Even though zinc is a nonmagnetic metal, the coating is so thin that the magnetic properties of the steel are not hindered. Since ferrous metals are prone to rusting, galvanized steel is an excellent selection for projects that require magnetic properties in moist and corrosive environments.
Hot Rolled Steel
Hot rolled steel has been roll-pressed at extreme temperatures, making the steel easier to form, and also results in products that are easier to work with. After the process of hot rolling, the steel shrinks slightly as it cools, giving less control over the shape and resulting in scaled surfaces, slightly round edges, and small distortions. Because of this, hot rolled steel is ideal for magnetic projects where precise shapes and tolerances are not as important as hardness and strength.
Cold Rolled Steel
Cold rolled steel is hot rolled steel that is further processed for more precise dimensions, closer tolerances, and a better surface finish. Cold finished steel is distinctive by its aesthetic appearance, having well defined corners, more uniformity, and a smooth surface. Because of this cold rolled steel is best suited for magnetic projects that require accurate precision or where visual appeal is important. However, because cold roll steel requires more processing than hot rolled steel, it also comes with a larger price tag.
Ferritic & Martensitic Stainless Steel
Stainless steels are prized for their excellent corrosion resistance as a result of their high chromium concentration. There are various classifications of stainless, and not all of them have magnetic properties. Out of the various types, ferritic and martensitic stainless steels (the 400 series) possess magnetism due to their high iron concentration and atomic arrangement. Similar to galvanized steel, ferritic and martensitic stainless steels are best suited for projects that require magnetic properties in corrosive environments such as high-temperature, chemical, and outdoor use.
Wrought iron is an iron alloy with very low carbon content. Its purity makes it more resistant to rusting than other ferrous metals. It is soft and ductile while still possessing tensile strength. Wrought iron is easily welded, can be reheated, and can be worked into various shapes–becoming stronger the more it is worked. Its malleability makes wrought iron a choice material for magnetic projects that require repeated fabrication and resistance to corrosive environments.