Annealed Copper

Annealed copper will discolor, but 24 hours?? I'd suspect one of two things:

You have a godawful atmosphere at your plant. It's OK to have your management breathing H₂S and ammonia, but give the poor line workers a break.

Your copper annealer is cutting corners and not controlling the atmosphere during the annealing process. You need tight process controls.

What does your QA guy say about this?

Thanks for the response

"What does your QA guy say about this?"

Well that's why they run to me. I am supposed to be the metallurgist, but my background is more is steelmaking than Copper - only joined a short wile ago. I knew discoloration will take place, but also suspected this is too short a time.

Any good articles you can propose on this topic of annealing/discoloration?

Thanks

I don't have any good reference at the moment. I think I'd get a piece of fully annealed electrical wire and leave it lying about for a day beside your regular copper to see if it turns also.

The other thing to check is the oxygen content of your copper.

I use annealed copper all the time.

Annealed copper will gradually harden over time, but 24 hours, sounds a little ridiculous. It takes about a year for the copper to harden to the point the annealing process is nullified and to start to discolor.

If the copper is not discolored when it arrives, the problem is in your process. It has been exposed to chemicals or excessive heat.

Copper will react to just about any chemical such as cleaning products, oils etc. Check your equipment for residues. Talk to the maintenance people.

Thanks for all the info,

I have spoken to the QA department again.

Seems the copper sheet arrives in this state, rather than discoloring on site.

Thsi makes me believe that the problem is in the controlls applied by the heat treater. We will go and audit his process.

He uses a vacume furnace. The discoloration is in areas on the copper plate - not all over. It looks like the product could be touching each other in the furnace.

Anythis spcific I should be looking for in the audit?

Thanks

Check the cleanliness of the pre-heat treated copper plates. If they are contaminated (oily, wet, other impurities), that may give you trouble. Also, see how they do the cooling and the content of O2/H2O in the nitrogen they use.

24 hrs as suggested use time is crazy. The guy who is performing annealing does not no what he is talking. A good annealed parts under proper storage conditions can last up to year maintaining its use quality.

The problem area is poor input quality for annealing which is connected to making short cut in cleaning and degreasing of the parts before annealing and normal indicator are patchy discoloration of the sheet

Improper furnace condition and atmosphere. Only audit at vendor site can bring this us.

To me either way it is the Annealing vendor trying to justify poor quality of their work