[katoman]

My neighbor had an aluminum handle from his tablesaw which had broken in half repaired. The metal shop told him they have to freeze it to weld it because it is aluminum. Just curious, is this true? If so, why?

 

[naptown CR]

never heard of freezing before. Would require some sort of heli arc or mig welding.

 

[shanekw1]

I've never seen anyone freeze aluminum before welding it.

 

[nEighter]

pack the atoms tighter??.. hell I dunno why a person would do that. With any other cast fix you have to heat the broken ends so when you braze it it melts together better. Aluminum is a little weird, but I have never heard of that. I will google it to see if I can find anything on this..

 

[Crawdad]

15 years experience working in aluminum foundries, and I've never heard of freezing it to weld it.

 

[mdshunk]

I've seen really thin aluminum (pop can thin) get frozen before it's TIG'd. Not sure why, though. Seems like a big cast piece ought to be able to take the heat.

 

[katoman]

Yes, I have never heard of this. I'm a carpenter not a welder, so I don't know. But it came back fixed like new, no idea if they actually did freeze it. Now I have to know, off to Google.:blink:

 

[nEighter]

the only thing I can think of is the idea of crystalizing a part that is cast to make the whole piece one crystal. It is in the way you cool it. That way there is no bonds to break.. makes the part "harder".

 

[nEighter]

http://en.wikipedia.org/wiki/Single_crystal

 

[katoman]

http://en.wikipedia.org/wiki/Single_crystal

Sorry, I don't have a PhD in metalurgy, have to wait for a simpler explanation as I can't find it on Google.

 

[nEighter]

whole thing is cooled at 1 time so the metal solidifies and makes 1 crystal.. so it is all one melecular piece..

when you weld something together is the metal or the weld stronger? The weld is, and the metal on the side of the weld is the weakest spot. In this same theory, when something is cast.. it is all the same temp and it cools at the same time so there is no issue with bonding between parts.. it is all 1 piece structurally.

 

[katoman]

whole thing is cooled at 1 time so the metal solidifies and makes 1 crystal.. so it is all one melecular piece..

when you weld something together is the metal or the weld stronger? The weld is, and the metal on the side of the weld is the weakest spot. In this same theory, when something is cast.. it is all the same temp and it cools at the same time so there is no issue with bonding between parts.. it is all 1 piece structurally.

Thank you. I understand that. What do you think he was referring to then about the "freezing". Maybe he meant they cooled it at a rapid rate?

 

[nEighter]

Dunno. Car parts and airplane parts are cast like this. Pistons for cars and props for planes (pieces that see alot of stress) get this treatment. I dunno. Usually after it is beat (to tighten the atoms together..) it is thrown in a bucket of water.. I dunno man I have no clue.

I know if there is a steel sleeve being put into an aluminum engine they heat the engine block, and cool the steel sleeve.. that way the steel shrinks, and the engine expands.. so when they are joined they "fuse" together due to their original sizes being different. The block would cool and contract and the sleeve would expand thus locking the two together. Those metal guys sure are smart