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Forgewelding- how low (temp) can you go?


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I had a bit of a discussion with a fellow who'd done some blacksmithing decades ago who was adamant that "You can't get a good weld at less than yellow-white heat". He was certain that the steel had to "start to melt" to weld. When I told him I could stack up pieces of metal, weld them at a high orange range (orange-yellow melted crayon, to be exact), take them through several forging heats, repeat, and then forge/grind down to a blade and heat-treat, all without a single weld popping apart, he wouldn't believe me. Apparently I'm using magic tricks or really good crazy glue.

All this aside, how low have you heard of people welding? I've heard that it can be done as low as a cherry-red if certain conditions are met.

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Food for thought...

 

Theoretically, if the fit between two steel parts is perfect, absolutely clean, and oxygen free, they will weld at room temperature. It takes me at least a good orange heat in practice, though.

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I am with George - even with a hydraulic press, anything "decent" needs to be orange.

 

in terms of physics/chemistry you just need to get the metal surfaces close enough for electrons to cross over to the other piece and make bonds. That can happen cold with little pressure if something is perfectly polished and perfectly flat (shims stick sometimes because of this).

 

What we are doing with heat and pressure is just putting the molecules as close together as possible and exciting the electrons so they can make the "jump."

 

kc

Edited by Kevin (The Professor)
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when box welding I have done good welds at a red heat (bright read just shy of orange) when the propane ran out when soaking a billet.(go for it or start over you know how it go's.)

I have heard that daryl meier used to do a demo were he would weld a Stainless steel pin into a stainless plate at room temp. I was told he pickled in some kind of acid rinsed in denatured and then pressed the pin in.... and it was welded..... but then he really is magic .....

MP

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I wish I had the book with me but industry roll welda at low heats of 300 to 600 C and very high tonnage and better welds can be had at lower temp as the material has enough physical resistance to being deformed , I mean you can only apply so much PSI to hot matal and it squishes out of the way .

In practice i would always go hot as that works for me.

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it's likely the pressure helps generate any other heat needed very quickly.

 

I remember watching a segment on how the coins here in the states are made and they're using some high tonnage presses. They said the coins kinda had their faces cast rather than stamped, as the stamping pressure caused enough heat that the metal would flow into the die to get really crisp images.

 

Could be a bunch of BS dunno. Kinda made sense though.

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I watched Daryl weld a billet at 1200 degrees at the ABANA. conference at Alfred in 1990.. it was under a pavilion but out side and you couldn't see any heat in the billet when it came out of the forge cause of the brightness of light under the pavilion.. I can't remember the specific steels but they were carbon not stainless... the billet was ground and passed around and it sure looked welded.. On a big air hammer but I don't recall what kind it was either.. and it was loud cause the steel was so cold

 

Dick

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I had a bit of a discussion with a fellow who'd done some blacksmithing decades ago who was adamant

 

You gotta watch those guys. :lol:

 

I had one a couple of weeks ago tell me that it was an absolute impossibility to weld in a gas forge, and that only an idiot would think he could forge with hydraulics... :rolleyes:

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Yeah, pattern welding has come a long way in the last couple decades. Have also seen Daryl Meier do it at a very dull red (closed weld). My welding forge wont get over 2200f and I rarely run it that hot.

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if you do a dry weld with high C carbon steel, it works.. did that in my old coal in a dark shop at an orange heat

 

- how bout if you have two billet just touching in the forge and they stick ( its a weld with very little pressure )

 

http://www.msm.cam.ac.uk/phase-trans/2005/Amir/bond.html

 

 

that tylecote's book on welding is suppose to be good ..too bad is as rare as chickens teeth.. like to get my mits on that one

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R. Tylecote in his book "solid phase welding of metals" gives conditions and tables for welding.

ALL that is required is two clean surface (oxide free) and to come within 4-5 angstroms distance..in this way they can share electrons..thus a bond is formed.

 

We can play with time, temperature and pressure, but rarely can get an oxide free surface....so

What temp is required depends upon how clean the metal is...we use flux to remove and prevent oxide and we use heat to lower the required pressure to get the surfaces to touch.

 

A "minimum" temp can be judged by heating two bars in the fire, adding flux and then rubbing the bars tother till you feel them "get sticky"..now look at the color..that is you effective minimum given your conditions on those bars.

 

NOW THEN

 

I an get a "weld" at room temp under my 3B nazel by stacking two thin sheets of steel and hitting them hard with 1/4" round dies..the small surface of contact and some elongation..no flux no heat....Tylecote places the pressure required to weld steel at room temp at about 225 ton per square inch and a given amount of deformation...lets say 50% though I do not recall what he states.

Now that is almost useless in a practical sense to use smiths because we want a bond larger than 1/4" round and do not have an infinite tonnage to use..so we heat and use flux and pounds or press the material with anything from a hand hammer on up.

 

BUT,

as far as what temp is"required", well...that depends....somewhere between room temp and liquids.

 

 

Daryl Meier is a genius and I wish he would do a brain dump to a group of us.........I am sure I could not keep up...last June I saw a pattern he had mentioned to me years ago...absolutely wonderful and a first in the world of pattern-welding..and flawless.

 

Ric

Edited by Richard Furrer
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...BUT,

as far as what temp is"required", well...that depends....somewhere between room temp and liquids....

 

There was one of the space probes that failed to perform a while back once it reached where ever it was supposed to go. The electrical switching contacts that were intended to open did not. They'd become welded during the trip.

 

Not because of the electric current but because NASA engineers required really clean surfaces and intimate contact. I bet that was within the short angstrom distance Ric mentions. I think room temperature is much lower in outer space.

 

Maybe all you guys who are busy with liquid nitrogen should be more careful. :rolleyes:

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I have never wanted to be normal, even before I met Daryl. ;) He is one of the great heroes of modern smithing. His influence is profound and deep in the craft of all who followed him down the pattern welded path, whether they know it or not.

 

Many things are now just, "everybody knows that". 'Twas not always so.

 

I have nothing to add to the metallurgy, you guys have covered that quite well. Carry on. :D

Edited by Howard Clark
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One thing I keep in mind, is that at the molecular level (maybe even atomic level), heat and pressure are fundamentally the same thing. So as you add pressure in the form of a whomping hammer, or press, you're increasing the heat within the piece, even if only for a moment, and not enough to see visible color difference (though I've seen that before, under the right conditions). With bubbly-yellow heat, less outside pressure is required to achieve a similar effect. And it's easier to get it hot, than to hit it hard, for most of us without large equipment, hence the tradition of sparky yellow billets.

 

I don't often quote Tai Goo on much, but he had a thesis some time ago I agree with, of knowing that every heat was abusing the steel... and minimization of heat cycles, and avoidance of overheating, was desirable in one's work. With the exception of welding really cruddy blister steel together, I try to follow that thought with regards to using lower heat than I did as a beginner, and my results have been better quality knives.

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R. Tylecote in his book "solid phase welding of metals" gives conditions and tables for welding.

ALL that is required is two clean surface (oxide free) and to come within 4-5 angstroms distance..in this way they can share electrons..thus a bond is formed.

 

We can play with time, temperature and pressure, but rarely can get an oxide free surface....so

 

Ok. If I put a granite surface plate in a box flooded with argon and sanded everything flat and smooth, what grit would I have to go to? If I ever have nothing but time on my hands I'd like to try this... :)

 

I'd heard the story about Daryl welding at 1200 or so at the ABANA conference, and I believe it was a 150# hammer in the version I heard.

 

-d

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