Fretting Al during transport

[Mikkelson]

Hi all,

We are producing Al wires and are transporting them as coils and on drums. Sometimes the wire gets superficially damaged on the contact points of neighbouring Al wire. At these contact areas a black dust is found.

I believed this is caused by a form of fretting?
Can the black powder be a form of Al2O3? And why is it black? Just because of the size? The Al is just EN-AW1370. I do not think 0.15% Fe causes the black color.
Some ideas to prevent the problem? Till now we focused on minimizing vibrations.

Regards Mikkelson

 

[EdStainless]

Is there anything (and I mean down to microscopic anything) on the surface of the wire when coiled?
Virtually all wire made is packaged with a coating of some kind. These are often not distinguishable but are there for shipping and handling reasons.
The color is likely just due to size and minor impurities (dust and dirt).

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P.E. Metallurgy

 

[Mikkelson]

Depended on the product.

You have the wire rod which is coiled. On this wire you have rests of the rolling emulsion. The phenomenon is seen both on coils as rolled as when annealed where you burn off (a part) of the emulsion.

The phenomenon is also noticed on drawn wire were the wire is degreased. This wire is drawn with oil but should be really clean when put on the drum.