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So, we have all been there... working with coal, left a piece in the fire with another piece, accidentally got the fire up to welding heat and ended up with an unintentional weld that was a bugger and a pox on all our houses.

So comes the question... has anyone done this intentionally as a practice?
I have heated up two pieces, gotten them close to each other at a welding heat and they literally liquified themselves together... At the time it wasn't what I wanted... but now that I think about it, it would be a much more controlled environment for me than trying to pull them out to stick them together.

Has anyone come up with a methodology that helps them with this.. scarfing differently, building a different fire (clean coke on bottom, mounds on front and back with only a small slit on the sides for parts entry, and an open top, for example)?

If anyone has made a practice of this, I would like to hear about their experiences... I have some downtime before I get my shop back to coal burning worthiness... so the theory and practice of this has taken root in my idle mind.

Thanks,

RB

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Welding in the fire is a known technique for small delicate pieces.

My experience with unintended forge welds was between a piece of 2.5" square stock and 3/4" round stock in a gas forge (at 7000' altitude too) I had the 2.5" sq stock heating and another smith sharing the gas forge repositioned her 3/4" round stock and slid it up and against my workpiece---we had to sledge it off...

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IIRC I've had a discussion with JPH on squeeze welding of chainmaille rings; I don't know if it's published anywhere.  BTW forge welding is a SOLID PHASE welding process; liquid steel not needed.  (May I commend to your attention Tylecote's "Solid phase Welding of Metals" for more information.

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Thank you for that reference!  I will look that up now :-)

While I know you are right that it is not turning into liquid, clearly, the molten state of the steel on the surface of the stock is, in non-educated terms (which are all the terms I know), clinging, but "rolling about" the stock at the hottest point.  This moves toward another bar of similarly heated stock when they gain close proximity.  I have repeatedly watched this process (much to the chagrin of any safety people who might be reading this) and have been made very curious about the attractive behaviour on the surface and the possibility of having a weld with any penetration take place by merely letting the stock do what it seems to want to do.

It seems that your experience is that a decent penetrative weld can be made in this manner without the addition of force.

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how do you know that that is the steel and not molten scale and or flux?

Solid phase welding is a tripod: Cleanliness:Temperature:Pressure  Max any of them out and you can get a weld!  

Cleanliness: example Vacuum Welding (an issue in space)

Temperature: example Forge Welding which we generally do several hundred degrees below the melting point of steel

Pressure: example Explosive Welding (or even galling of a bolt/nut.)

As for experience: I welded my first billet about 1984...Had a remedial class with Billy Merritt at a conference. (It is rumored that Billy was not allowed into Philadelphia due to the possibility that the Liberty Bell might weld it's crack if he walked by it...)

The state that allows for a real weld is the sharing of electrons in the metal. (which is why cleanliness, pressure and temperature makes a difference.)

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That is a really good question.

I am trying to remember if I have seen this phenomenon (the sideways movement of the liquid while at welding temperature in the fire) only while using flux... and my gut says that I have seen it without... however, that doesn't mean that is true.  I have never really experimented with this, only observed it.  It's not a sheen, but more like a blob of butter... or possibly a blob of glass-like flux... :-)

I am not questioning or even disagreeing with your accurate description of welding.  Billy slapped me with the same cleanliness mantra for a year in his shop... I wasn't there long enough for him to slap me about pressure... I think he was saving it.  however, I am simply curious... and since he is no longer with us to ask, I have put it out to the digital universe as to whether or not anyone has noticed the same.

If you have not, then that's okay... my description is, as you have recognized, not an engineer's assessment, or one that comes from an industrial or metallurgical background.  I'm just a curious guy with a limited vocabulary to describe things that I don't understand.  I appreciate your candor and I really hope that your tone does not indicate that I have offended you in some way.

Thanks for the input.  I have already done a search for the suggested book, and found it to be the price of a birthday present ... or so says my wife.

Thanks again,

RB

 

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13 hours ago, ThomasPowers said:

The state that allows for a real weld is the sharing of electrons in the metal. (which is why cleanliness, pressure and temperature makes a difference.)

I don't think I've ever heard such a sensible scientific explanation of forge welding.  This really does explain why clean metal is essential to welding.  We all know that scale prevents a good weld, but I've never really thought about it being the sharing of electrons.  Great point!

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not exactally,  Scale can share electrons also, but it does it at very high temps

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"Like butter melting in the sun"

Where I live we hear the booms from the explosion sites fairly regularly and they have done a bunch of explosive welding---even using it for Art! (Also explosive repousse...NM Tech. Search on:  explosive art at NM Tech images  )  I had always though that explosive welding was a mechanical bond until I got to talk to some of the Profs out here and they told me that no, it actually is a solid phase weld.   Making industrial diamonds explosively was a real blast!

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Tylecote's Solid phase Welding of Metals may well be available from your local library. A quick Google search shows that there's a listing on WorldCat, so your local branch may be able to get it through interlibrary loan.

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3 hours ago, Steve Sells said:

not exactally,  Scale can share electrons also, but it does it at very high temps

Thanks Steve, that makes sense.

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Redbeard, if I understand your question I'd say the reason for using a hammer I stead of just touching them together in the fire is control.

I can think of many situations this would be lost if you just touch them in the fire.

Say you have two square bars and one has a little twist. Then the only contact may be just the top edge, or whichever are in contact. Thus an incomplete weld.

Another and most critical,,, I can't Imagine forgwelding to dimesion if I couldn't both use my hammer and my eyes and the anvil.

And then there is the drop the tongs weld, or say a forge welded right angle using say 1/4"x1".

I n the past I used the "touch test" to determine if I was at a FW temp, but that need is long replaced.

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One thing to consider is working with imperfect conditions:   When things are perfect it's generally easy to get good results.  When things are not so perfect anything that helps can make a big difference!

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I have seen Jerry Darnell do this type of weld.  If I remember correctly, he called it a "jump weld."  He was welding very small hooks onto larger stock.  Weld was initiated in the fire and then refined and shaped at the anvil.  Good fire control and heat isolation are critical.  He had no problems at all, however, it looked like a technique that should be practiced before trying on an actual piece.

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I"ve used a wiggle method for doing jump welds on the ends of T's like making a hardie or so..  Itis then finished in the hardie hole to set the scarf.. 

Like anything it just takes practice to make it accurate...  

in the way, way back I also experimented with taking a smaller round bar 1/2" and inserting it into a 1/2" hole in a 1" square bar and brought both up to temperature and wiggle, wiggle then whack either end, finish the 1" back to size.. It worked very well.. 

 

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