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discoloration and deterioration of M2 form roll

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Plako

Mechanical
Jan 14, 2009
8
US
I have a question about an M2 form roll we are using to shape some copper wire that has been solder coated with a solder that contains 2% silver. After rolling some 14000 ft. of wire (35 minutes), the "wire track" becomes very visible on the roll as a darkish amber discoloration. The discoloration of and by itself is not a problem, but what happens at the same time is a subtle deterioration of the brightness of the form being rolled onto the wire. That brightness continues to deteriorate to the point where the wire is rejected by QC.

We have studied the roll. There does not seem to be any significant buildup of debris or any other material. The form itself is still good and sharp. On the coated wire itself we can see a very distince "dulling" of the surface finish. The form itself still appears acceptable.

Is it possible that there is some reactivity between one of the alloys contained in the M2 roll and the silver contained in the solder? There does seem to be a direct correlation between the discoloration of the roll and the deterioration of the wire.

I sure would appreciate any help/light anyone might be able to shed on this problem.
 
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Silver tarnishes readily in air, so it is possible the discoloration is due to oxidized silver, which wouldn't be thick enough to be noticed as a buildup.
 
Sounds like you need to look into coatings for the roll. Probably oxides sticking to it causing the problems. Look into ceramic coatings.
What do you use for a lubricant? You might need one.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
 
Any lubricant that is used around your operation should be checked for sulfur. Sulfur reacts with both Cu and Ag.
 
Tarnish on silver is not silver oxide but silver sulfide.Oxide usually forms only with ozone.Unclesyd is right again ! Look at the lube. I had a tarnish problem on fancy silver plated bearings , they packaged it in corrugated cardboard which no one realized is loaded with sulfur !
 
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