Timeline for Why don't metals bond when touched together?
Current License: CC BY-SA 3.0
16 events
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| Jan 28, 2021 at 13:52 | comment | added | minmax | If the surfaces are very flat and clean, once the air is expelled there will also be a high pressure (1atm roughly) bringing them even tighter together. At this point I believe cold welding occurs. I think the orientation also plays a role, so that the bond is stronger when there isn't a defect at the interface and one gets a single crystal lattice out of the two pieces. | |
| Apr 9, 2019 at 14:36 | comment | added | patta | With an hammer you can convince the electrons to move from one piece to the other, and form a weak cold weld | |
| Feb 13, 2016 at 20:48 | comment | added | Peter Diehr | I've had very clean metal surfaces weld themselves together while in an ultrahigh vacuum. The surfaces were smooth, but not overly so. These were friction fits for an electron gun. This also happens in outer space. The solution? (a) add some non-volatile dirt, such as "dry moly", molybdenum disulfide, or (b) coat the surfaces with different metals, such as silver on one, aluminum on the other, or (c) use different metals. This form of cold welding is accelerated when the vacuum chamber is baked out to remove the last remnants of water vapor. | |
| Nov 22, 2013 at 19:21 | comment | added | Mark Dominus | I think the point about gauge blocks (also called Johanssen blocks) should be made more forcefully. These are metal blocks whose surfaces are ground so perfectly flat that two blocks will adhere if merely pressed together. Wikipedia says: “Wringing is the process of sliding two blocks together so that their faces lightly bond. Because of their ultraflat surfaces, when wrung, gauge blocks adhere to each other tightly. Properly wrung blocks may withstand a 75 lbf (330 N) pull”. | |
| Nov 20, 2013 at 16:52 | comment | added | Pete Kirkham | @polkovnikov.ph gauge blocks are as much 'an ancient engineering tool' as a motor car is an ancient form of transport. Both date from the just before the turn of the 20th century, and both are still in current use. | |
| Nov 20, 2013 at 15:21 | comment | added | dmckee --- ex-moderator kitten | "It's also called cold welding." It is also part of what happens in the galling of threaded fastener. A point that can come up a lot in assembling ultra-clean parts for low background experiments in particle physics. | |
| Nov 20, 2013 at 12:44 | history | rollback | Hasan |
Rollback to Revision 2
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| S Nov 20, 2013 at 7:23 | history | suggested | Ramchandra Apte | CC BY-SA 3.0 |
changed link to english version
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| Nov 20, 2013 at 6:47 | review | Suggested edits | |||
| S Nov 20, 2013 at 7:23 | |||||
| Nov 20, 2013 at 6:24 | comment | added | BlueRaja - Danny Pflughoeft | There is a serious lack of videos about this on Youtube | |
| S Nov 20, 2013 at 5:58 | history | suggested | yuritsuki | CC BY-SA 3.0 |
major formatting, readability improvements
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| Nov 20, 2013 at 5:22 | review | Suggested edits | |||
| S Nov 20, 2013 at 5:58 | |||||
| Nov 20, 2013 at 4:03 | comment | added | polkovnikov.ph | There's even an ancient engineering tool, a set of metal parallelepipeds to measure length (something like weights for weighting). They're so polished that they almost weld when touch. Edit: found it! It's called "gauge blocks". en.wikipedia.org/wiki/Gauge_block | |
| Nov 19, 2013 at 22:22 | comment | added | DumpsterDoofus | I believe extremely clean and flat glass slabs will also bond together when placed in contact, but for an altogether different reason than delocalized electron bridging. | |
| Nov 19, 2013 at 18:47 | vote | accept | jcw | ||
| Nov 19, 2013 at 18:37 | history | answered | Hasan | CC BY-SA 3.0 |