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Re: What is oxygen-free copper wire and why use it?


Doesn't oxygen free copper have larger crystal size...

I haven't seen any evidence that it does. Jon Risch has tried to make the case for that being the case referencing some photomicrographs of crystal microstructure (http://microstructure.copper.org/coppers.htm) but the comparison as far as I can tell is apples and oranges.

Here's the shot of the OFHC sample:



And here's the shot of the ETP sample:



They look about the same when compared side by side such as this, but Jon points out that the line scale (that line in the lower left corner of the photo) is 125 microns for the OFHC sample but 50 microns for the ETP sample, which would, on the surface, indicate that the ETP sample has smaller grain structure.

What's overlooked however is the fact that the OFHC sample is in rod form without any subsequent processing whereas the ETP sample is in wire form after a hot roll process. Rod form is what exists right after the continuous casting. To make wire, the rods are then subsequently drawn or rolled to achieve the finished length and diameter.

Naturally if you roll or draw out the rod, increasing its length and reducing its diameter, you'll end up with crystals which have a smaller cross sectional area than when it was in rod form.

...and therefore less unwanted diode effect from the fewer crystal interfaces per given length of wire?

Haven't seen any evidence of crystal-to-crystal diode effects either. Just a bunch of hand-waving and half-baked theories.

se





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