Cold welding metal together on earth


#1

Originally published at: http://boingboing.net/2017/02/10/cold-welding-metal-together-on.html


#2

I saw the AvE video on this a few weeks ago. He also did it with gauge blocks, which are metal blocks with extremely flat, and precise dimensions.

The theory I heard on why it works is that if two surfaces are so flat and smooth, and there aren’t a lot of “bumps” of the two surfaces on the atomic level, that the like atoms will bond with each other. In space is happens easier as there is no air, but on earth if you press the two parts and twist to remove the air between the two halves, the two parts stick purely from the atoms bonding together.

I think in that AvE video he also shows a guy who polished a metal bench so smooth, he put a smooth metal puck on top of it and it just slid around on the cushion of air between the two.

This makes me wonder - if one was literally able to get two surfaces perfectly smooth - just one plane of atoms, on two parts, could you permanently fuse the two? With no gaps or other kinds of atoms, would the atoms just link and bond together? Or does there need to be maybe a little bit of heat?


#3

If they were molecularly smooth, and you placed them on each other in a 1G field in a vacuum, and maybe pushed the top piece slightly in the horizontal plane although that shouldn’t really be necessary, they would become a single piece. No external heat necessary.


#4

OH man - has anyone done this? I want to see it… just like a 1" cube become one with another.


#5

I don’t actually know… it was something we were taught by the old hands when I was in the rocket biz, because it happens easily in a hard vacuum. Everyone wants their super-ultra-space-tech to be all glittery and perfectly smooth, but making surfaces too precise meant stuff that could be stacked in free air, could not be stacked in a vacuum or it’d merge. The pebbly rind of a cast piece is better than a machined surface in many situations.


#6

I was under the impression that some of interest in Type III Hard Anodizing was in response to cold welding in a vacuum. I could easily be wrong, though.
That said, the gauge blocks likely aren’t cold welding, as there’s atmosphere and oil in the way. Instead, it seems more likely that the precision is such that the oil helps create a vacuum between the blocks (and that’s what holds them together).

I love AvE.


#7

Anodizing does roughen the surface, and more importantly deposits a film of non-elemental material on it, so that makes sense to me.

(I was answering Mister44’s specific question, not talking about machinist blocks sticking together - which is typically caused by oil suction, as you say, in my experience).


#8

[quote=“nothingfuture, post:6, topic:94765”]I love AvE.[/quote]Haven’t seem his stuff before as far as I can recall. The swearing just adds so much flavor. (Seriously!)


#9

So has anyone managed it with chinesium yet?


#10

Agreed.


#11

Maybe need to align the crystal structure, if any, and if needed coat one surface with an atom smattering of flux impurities to take care of remaining trapped molecules of atmosphere.


#12

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