Softening Silver Plated Copper

[JRKH]

I have a problem I hope someone can help with. I have been looking on the internet without much luck.
Here is the run down.
Parts are made from a length of cold drawn copper bar 3/32" X 1/2".
Material spec calls out copper quarter hard 20 - 40 Rb
Parts are silver plated.
My customer reports that they have parts checking "in the low 40's

I would like to soften these parts without damaging the silver plate if possible.
(some discoloration of the plating would probably be OK.
Can this be done? What temps am I looking at here?

Any help would be appreciated.


James

[Wes Bucey]

Originally Posted by JRKH

I have a problem I hope someone can help with. I have been looking on the internet without much luck.
Parts are made from a length of cold drawn copper bar 3/32" X 1/2".
Material spec calls out copper quarter hard 20 - 40 Rb
Parts are silver plated.
My customer reports that they have parts checking "in the low 40's
I would like to soften these parts without damaging the silver plate if possible.
(some discoloration of the plating would probably be OK.
Can this be done? What temps am I looking at here?
Any help would be appreciated.
James

How many parts, James?
How long are the parts?
To check the hardness of the copper, customer has to destroy the silver plate. Have you checked and confirmed the readings?
What was the hardness test on the raw stock?
Did you keep a coupon sample? (Sometimes, not always, hydrogen embrittlement from the plating process can affect a hardness reading on some metals.)
Checking with the metallurgist at your local heat treater will give you information on how badly the silver plate will be affected by a softening process - you could even try a few samples, provided you have sufficient quantity to experiment.

All else failing, other options include:

1. stripping plating, heat treating to soften, replating.
2. negotiating with customer to use as is provided function (reason for 1/4 hard) is not impaired. [I'm curious - if product needs to be soft, is the plating affected by bending the product?]
3. scrapping and starting from scratch (make samples to confirm copper starts at 1/4 hard, does not get work hardened, does not get affected by hydrogen embrittlement.)

[JRKH]

Customer Has about 450 pcs. I have about 50 pcs here.
They are a small bent piece about 1" X 1".
Yes I have confirmed the readings.
Also I have checked parts with the plating on and I have removed plating on a couple of parts (deburr wheel) and then checked part. Little or no change in reading.

No I don't have a raw stock coupon on this, though I'll check with the shears and see if we still have some stock.

I'd really like to find out if someone knows what temperature is required to normalize copper.

[pthareja]

Well let me understand the problem first!
Customer specified Hardness is 20-40 HRB,
wishes you to preferably restrict at low of 40 ( does it mean 30+ ? )
What did you provide: beyond specs ( above 40?) If yes we need to soften.
So what is the target hardness and the final hardness? We will base the softening on this reqirement. for Temperature, time and atmosphere. The heating is going to be critical, even diffusion may have to be avoided because copper should expectedly tend to eat up ( diffuse into) silver.

Knowing target hardness and the final hardness, i shall be glad to suggest you the temperature.
thareja

[JRKH]

Current hardness is at 43
Desired hardness is 30 to 35.

Thanks

James

[pthareja]

Originally Posted by JRKH

Parts are made from a length of cold drawn copper bar 3/32" X 1/2".

Material spec calls out copper quarter hard 20 - 40 Rb
Parts are silver plated.
My customer reports that they have parts checking "in the low 40's
James

Originally Posted by JRKH

They are a small bent piece about 1" X 1".
James

I had another clarification, which I had forgot to ask, and tempted to ask just after my post:-

i) is cold drawn copper bar rectangular ? 3/32 " and 1/2 " ?
ii) clarification of 1" x 1" geometry : small bent pieces, and how they were made?

hardness available 43
required 30-35

regards
pthareja

[JRKH]

Originally Posted by pthareja

I had another clarification, which I had forgot to ask, and tempted to ask just after my post:-

i) is cold drawn copper bar rectangular ? 3/32 " and 1/2 " ?
ii) clarification of 1" x 1" geometry : small bent pieces, and how they were made?

hardness available 43
required 30-35

regards
pthareja

Material is purchased as cold drawn copper bar 1/8 inch X 1/2 inch X 8 Feet.
This is then sheared to length, one hole puched (.25 dia @ 5/16 from one end),
and bent to a 90 degree angle, where each leg is 1 inch long.
Parts are then silver plated.

James