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Flaking On Copper Plate

06/15/2016 12:29 PM

While preparing cooling apparatus for Induction furnace, 10mm pure copper plates were bent on rollers (cold rolling) as a result of which flaking signs on the surface have appeared . How to remove or cure such flaking and make the surface smooth ?

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#1

Re: Flaking On Copper Plate

06/15/2016 8:47 PM

https://advancedplatingtech.com/plating-topics/plating-flake-loose-adhesion-plated-layer/

Do you clean your copper plates properly before putting them through the cold rolling process?

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#4
In reply to #1

Re: Flaking On Copper Plate

06/15/2016 11:36 PM

Correct me if I'm wrong, but, I don't think he was talking about "electro-plating or a variant of it", but ≥ 95% pure 10mm thick CU.

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#7
In reply to #4

Re: Flaking On Copper Plate

06/15/2016 11:53 PM

Yes, that'sounds what I mean

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#6
In reply to #1

Re: Flaking On Copper Plate

06/15/2016 11:50 PM

"10mm pure copper plates"

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#2

Re: Flaking On Copper Plate

06/15/2016 11:12 PM

Have you tried annealing the plates?

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#5
In reply to #2

Re: Flaking On Copper Plate

06/15/2016 11:48 PM

Seems he should have annealed the plate(s) before, but either way, he's going to have some flaking due to deformation of the CU "ingot" (being more than .060"- 1.5mm)

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#3

Re: Flaking On Copper Plate

06/15/2016 11:26 PM

Dependent of the bend radii, you may have stressed the copper beyond the ductility, which you didn't tell us what your finished angle is?

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#8
In reply to #3

Re: Flaking On Copper Plate

06/16/2016 12:01 AM

600 X 670 mm copper plate 10 mm thick bent at 90 degree at both ends of the 670 mm side to have 150 mm rise on either side . No annealing was made prior to bending on the apprehension that the plate could soften and become out of shape.

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#9
In reply to #3

Re: Flaking On Copper Plate

06/16/2016 12:01 AM

600 X 670 mm copper plate 10 mm thick bent at 90 degree at both ends of the 670 mm side to have 150 mm rise on either side . No annealing was made prior to bending on the apprehension that the plate could soften and become out of shape.

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#12
In reply to #9

Re: Flaking On Copper Plate

06/16/2016 2:43 AM

What was your bend radius? Did you allow for minimum bend radius? There's more to metallurgy than just throwing piece of metal on a brake press an forming it to whatever angle.

"There’s a rule of thumb to determine minimum bend radius, and this generally works for most metal's Divide 50 by the material’s tensile reduction percentage as specified by your supplier. This value will vary by grade."

"If the steel has a tensile reduction value of 10 percent, divide 50 by that value: 50/10 = 5. Next, subtract 1 from that answer: 5 – 1 = 4. Now, multiply that answer by the plate thickness. If the material is 0.5 in. thick: 4 × 0.5 = 2. So in this case, the minimum inside bend radius is 2 times the material thickness."

Note that this is just a rule of thumb. Finding the true minimum bend radius for steel or aluminum, copper plate requires a little research.

This should include data from your material supplier, whether you are bending with or against the grain, as well as information specific to the application"

Click here for more information about forming metals.

Hope that link helps

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#10

Re: Flaking On Copper Plate

06/16/2016 1:30 AM

Do you have any pictures you can post? It sounds like scaling which can be removed by sand blasting and you can pickle the copper for further protection by using a hot 5-10% sulphuric acid solution containing 0.35g/l potassium dichromate.... Components that have been pickled should be rinsed thoroughly in hot, fresh water and finally dried in hot air....as a general rule copper plate should have a minimum bend radius equal to the thickness of the plate....

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#11
In reply to #10

Re: Flaking On Copper Plate

06/16/2016 2:02 AM

Thank you for your suggestion, which is very much appreciated . Bending radius is 90 mm . Apart from cleaning the surface by sandblasting can the surface finish be improved by a coat of resin or something like that ?

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#16
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Re: Flaking On Copper Plate

06/17/2016 2:57 AM

Coating can be done to maintain appearance and as additional protection...

http://everbrite.net/portfolio/copper/

http://www.deltaindustries.com/powderbasics.htm

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#13

Re: Flaking On Copper Plate

06/16/2016 9:11 AM

Hi, I am no chemical engineer, but perhaps the several reactions below, could lead to a solution.

Should the flakes be due to oxidation, the bending process creates energy on the surface, might be the cause of copper reaction to O2 and form the oxides.

If those are oxides, the introduction H2 and CO might hold the solution. Would it be exothermic or endothermic reaction? I am not sure. Please consult a Chemical Engineering professional.

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#14

Re: Flaking On Copper Plate

06/16/2016 10:36 AM

Anneal and then hot pickle the plate in dilute hydrochloric acid, the metal become malleable and surface oxidants are removed.

It’s the way I was taught to do it.

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#15

Re: Flaking On Copper Plate

06/16/2016 12:22 PM

SO, no annealing prior to bending, 90 mm bend radius, and thus you have flaking/scaling of the hard copper. Learn your lesson, and go back and try this again on a heated piece (not near the melt, but well up into the ductile range).

Also, maybe your machine worked too fast and what you are really looking at is sticking/galling to the rollers? Try also slowing down the bending process to minutes or hours. A day with the Lord is as a thousand years. A day around some of these guys on this blog is taking like forever.

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#17

Re: Flaking On Copper Plate

06/17/2016 8:05 AM

Not my primary field, but spent a little while in a pressed matal shop that manufactured copper/brass/bronze electrical contacts.

Might also have something to do with grain direction in the original billet. You might be bending across the grain.

Annealing as others have suggested, plus die surface lubrication/polishing, plus adequate clearance between internal and external tooling.

You mightlik eto chseck section thickness through the bend. That will give you some indication whether you are "bending" the stock, or "drawing" the stock. If there is material thinning, then you are stretching the material during the bending process.

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