When you think of common uses for copper, what’s the first thing that comes to mind? Pipes, certainly. Wiring, maybe. But magnets? Probably not. Interestingly enough, however, copper does play a significant role in magnets. And the reason for this has to do with the high conductivity of the metal.
Just how well does copper conduct? According to the Copper Development Association Inc., electrical conductivity is the primary driver that differentiates copper from other metals. In fact, only silver outperforms it in this regard. And in terms of commercially available metals, copper is the clear cut winner. What’s more, copper offers a high level of thermal conductivity as well. Add to this its excellent strength, its ductility, its machinability, its durability, and its oxidation, corrosion, creep and fatigue resistance and it becomes clear why copper is a preferred metal in magnetic applications.
All of these aforementioned advantages, of course, apply to pure copper. It is important to keep in mind that the actual conductivity of copper alloys will depend on the other materials that make up the specific alloy. The Copper Development Association warns, “There are hundreds of copper alloy strip metals from which to choose and some of them have conductivity as low as that of iron.”
For that reason, it is important to choose a copper alloy that is designed specifically for magnetic uses. Copper alloy 110 is one such choice. Also known as Electrolytic Tough Pitch (ETP) Copper, alloy 110 is, fortunately, the marketplace’s most common copper so it is readily available. What makes it so superior for magnet applications is that it is composed of at least 99.9 percent copper. That purity level renders it an electrical conductivity rating of 100+ percent IACS, among the very highest to be found in a copper alloy.
The tough pitch aspect of the alloy’s name means that it is an oxygen bearing copper. At the same time, the copper in the alloy has been electrolytically refined to lower the impurity levels to total less than 0.03 percent. As the Copper Alliance explains, “Commercial electrolytic tough pitch copper (Cu-ETP) has the high conductivity typical of pure copper because it contains enough oxygen to ensure that residual impurities are present as oxides rather than in solution. If dissolved in the copper they would have a much more adverse effect than they do on conductivity.”
Universal for electrical applications, ETP possesses, at a minimum, a conductivity rating of 100 percent IACS but most of the product that is sold today contains 101 percent IACS or more. In addition, its typical oxygen content is 0.02 percent to 0.04 percent. At the same time, the Copper Alliance lists ETP copper’s thermal conductivity at 20 degrees Celsius as 397 versus 230 for aluminum.
All of this adds up to ETP copper being amenable to high current applications. Indeed, alloy 110’s high conductivity contributes to it being used exclusively in transformers, switch gear, magnets and a variety of other electrical applications. Moreover, it is the material of choice for most conductors and fabricated electrical components.