Author Topic: 3/8 copper plate warping temperature? solved  (Read 5990 times)

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Online coppercone2Topic starter

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3/8 copper plate warping temperature? solved
« on: July 17, 2023, 06:20:00 am »
I would like to patch the ends of a groove I made in a copper plate, by soldering two copper blocks on either end (~1/8 inch thick by 1cm squared)

I thought to put the whole thing on a hot plate and solder it with solder paste.

However, the copper plate is flatish right now (8x4 inches).

Would bringing this block to soldering temperature on a hotplate incur warping? I mean with regular electronics solder paste, not brazing.

I never noticed this effect soldering pipes but I never worked with a substantial piece of copper plate before. I want it to stay flat.

Should I stick to glue, or is this safe?

Not really clear about what temperature metal warping occurs at.

I am pretty sure this is fine, but it would be a major PITA to fix this thing. My plan was to take off the hot plate when the solder melts and then set it on a soft fire brick for slow cooling.
« Last Edit: July 18, 2023, 03:47:47 am by coppercone2 »
 

Online coppercone2Topic starter

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Re: 3/8 copper plate warping temperature?
« Reply #1 on: July 18, 2023, 02:13:32 am »
actually I remembered clickspring and I did it on a fire brick with a blow torch. Worked fine little bit messy but I don't see it doing anything funny. Guess its similar to brass.

polished up nice and sealed the trench well. The holes under the block got filled. lead free PCB solder works fine for brass/copper junctions even with high thermal mass.
« Last Edit: July 18, 2023, 03:49:05 am by coppercone2 »
 

Online Doctorandus_P

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Re: 3/8 copper plate warping temperature? solved
« Reply #2 on: July 29, 2023, 03:30:47 pm »
If the plate is heated evenly, it expands evenly and it won't warp.

If the center is hotter then the circumference, then it will bulge.
If the circumference is hotter then the center, then it will also warp, The outside will expand, but it can't go outward, and therefore the outside will get "wobbly". It is for this reason that circular saws have narrow slits in between some of the teeth. This divides the circumference into segments, and each segment can expand a bit when the saw gets hot during sawing, and it can do so without warping.

Placing the whole thing in an oven will ensure quite even heating. putting some heat insulation will also improve even heating
 

Online coppercone2Topic starter

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Re: 3/8 copper plate warping temperature? solved
« Reply #3 on: July 29, 2023, 04:06:09 pm »
the warping from cutting the slot is >> then the warping from the lead soldering. I would call it non issue.

But yea oven makes most sense I guess.


but what temp does permament deformation occur?
 

Online coppercone2Topic starter

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Re: 3/8 copper plate warping temperature? solved
« Reply #4 on: July 29, 2023, 04:08:32 pm »
Actually not sure how this works.

If you heat a metal slightly, back and forth, does it get micro deformations? I figured bellow some temperature range, it will be basically ideal. Like it has memory.

I am guessing this has something to do with pressure due to temperature gradient (mechanical pressure/stress) and there are geometries that are infact very sensitive to small temperatures because they will buckle some membrane.
 

Online T3sl4co1l

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Re: 3/8 copper plate warping temperature? solved
« Reply #5 on: July 29, 2023, 08:15:01 pm »
Well...

If you bring it up to the annealing temperature, stress is relieved, which might've been stress that was holding it in its exact shape (e.g. cold rolled stock that's been milled flat).  If it's already annealed (or not stressed), it probably doesn't matter.

Soft soldering doesn't quite reach those temperatures for copper or brass, so that shouldn't be a problem regardless.

I'm not aware of anything that's cycle dependent, if the temperature is uniform across the piece.

Uneven and rapid heating/cooling can cause local deformation, which locks in stress.  It seems doubtful a hotplate could deliver such heating, maybe even if the cold workpiece is placed directly on a hot hotplate.  These metals are very conductive, and spread heat quickly.  The more likely danger is very hot torches (oxy), water quenching, or wide area workpieces where the temperature differential can be large despite the conductivity (working sheet with a (gas/air) torch, perhaps).

Also, soft solder fills gaps easily, so the mating faces don't have to be exceptionally flat.  And over a wide workpiece, clamping can easily reduce gaps without needing flatness or the prevention of warpage.

Tim
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
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