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What Is Oxygen Free Copper?

Oxygen content is removed from copper to improve its conductivity.
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  • Written By: Patrick Roland
  • Edited By: A. Joseph
  • Last Modified Date: 23 June 2014
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Oxygen free copper is a type of copper that has had much of its oxygen content removed in an effort to improve its conductivity. The name actually is a misnomer, because trace amounts of oxygen are still found in this metal. Many audiophiles prefer this type of wire for stereo systems, claiming that it improves sound and volume quality. There are others within this community, however, who claim that the wiring provides no better results than traditional copper.

Any copper that has its oxygen levels lowered to anything below 0.001% is considered oxygen free. There are two types: oxygen free electronic and oxygen free. Standard copper is called electrolytic-tough-pitch and has an oxygen content of 0.02 to 0.04%. Oxygen free electronic is classified as having 0.0005% oxygen content and was forged in an oxygen free environment. Oxygen free is classified as having 0.001% oxygen content, and its conductivity rating is slightly lower than oxygen free electronic.

Oxygen free copper has a different forging process than pure copper. All copper has oxygen added during the forging process, but oxygen free adds less and is smelted differently. During this different process, hot metal is cast into a crucible, and the bottom is allowed to cool while the top remains hot. The entire crucible is cooled slowly, which allows for the oxygen content to be lower.

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This type of copper is found in many aspects of manufacturing, but its most common use is for electronics. Its higher conductivity rating has made it an extremely popular choice of stereo enthusiasts and their audio equipment. It is commonly found in high-end headphones, speakers, and video equipment. Its low oxygen content means there is little iron within the copper wire, and therefore the conductivity is good for low-frequency home listening devices.

Products made with this metal have a great deal of controversy attached, however. Some audio experts claim that the preference for such cables and equipment is misleading. Regular copper wires have the same conductivity specifications. This, skeptics claim, proves that there is no audiological advantage to the more expensive, oxygen free type of copper wire. A listener's preference between copper wire and oxygen free copper comes down to a matter of personal taste, because these claims conflict so greatly.

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Discuss this Article

Hawthorne
Post 6

@aishia - I can answer that one for you. It's ironic, but oxygen free copper being used for scientific stuff like the particle accelerators actually has nothing to do with whether it has oxygen in it or not.

See, part of the process of smelting oxygen free copper involves refining the copper in a solution made of copper sulfate and sulfuric acid. This plus the slower cooling process of smelting do result in much less oxygen, but they also take out a bunch of impurities.

Iron in particular is greatly reduced in oxygen free copper -- which makes it great for use in scientific equipment, as iron can cause interference that can affect the results of experiments.

Therefore, oxygen free copper is used for scientific experiments because it is iron free, or at least extremely low in iron. Fascinating stuff.

aishia
Post 5

@ahain - I don't know, the article says that oxygen free copper has found lots of different applications that have resulted in it being manufactured. it goes on to list that electronics are the most popular one by far, but one of the others might be for electronics.

And Mammmood, I looked up oxygen free copper a bit more and found something you'll be happy to hear: it's already used in large-scale scientific equipment, particle particle accelerators! I wonder why they use oxygen free copper instead of regular copper there if the conductivity isn't much different, though?

ahain
Post 4

@malmal - Very interesting question, there. I always forget that copper is considered a precious metal in England.

I think your educated guess is the best one -- they probably would leave the oxygen free copper alone and stick with the regular old copper they're used to. To answer your opinion question, I think the jeweler would agree with me and pick the original copper.

Why? Because removing the oxygen from copper to make oxygen free copper is only done to try and give it more conductive properties for electrical stuff (and it's up for debate whether it even does that). That means that for the intents and purposes of jewelry-making, oxygen free copper and regular copper are the same substance.

malmal
Post 3

Is oxygen free copper considered just as valuable as traditionally smelted copper? Copper is considered a precious metal in the United Kingdom, and I'm curious what jewelers think about this new kind of processing.

Does it "ruin" the metal as far as jewelry making is concerned? Does it make it even more usable, upping the value by getting rid of oxygen as a potential impurity? My best guess without getting any answers is that this oxygen-removing process is only done on copper reserved for electronics, and so copper jewelry is probably unaffected.

I'm just curious if the situation where oxygen free copper and regular copper were offered to a jeweler side by side ever happened would result in the jeweler picking the oxygen free stuff or the original recipe. Opinions, anyone?

Mammmood
Post 2

@Charred - Perhaps you already have oxygen free copper in your stereo system and you’re not aware of it?

Anyway, I do agree that there are several variables to consider. Amplification and additional speakers would certainly be one of them I suppose.

After reading the article, however, my first thought was not so much consumer applications of the technology but scientific applications. For example, I think that perhaps this is one way superconductors get built, by depleting oxygen from the metal.

I am sure that they have other processes as well. I’ve heard that temperature plays a role, for example, in creating superconductivity. That’s really where the action is, in my opinion; the ability to create powerful superconductors for large scale scientific applications.

Charred
Post 1

While I’ve never knowingly purchased oxygen free copper for my stereo system, I am not persuaded that this is the one feature that results in great sounding audio. I think the quality of your speaker system and the source audio have a greater influence than the quality of the copper wiring.

At least in my stereo, the speakers are close to the stereo – they are not strung across the room or something like that. Therefore, even if I bought into the premise that improved conductivity would make a difference, I don’t see how big the difference would be given that the signal has less distance to travel.

If you want the best audio, get a stereo amplifier and some big sub woofers. Those two additions will make a big difference in the quality of your sound, in my humble opinion.

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