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Forge welding, No Flux, and different welding methods?

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Being new to knife making and forge welding Damascus knife blades, I see references to Welding with no flux, welding with Borax, welding with WD40, and Kerosene. Could some of the experts members detail how they prepare the blade material stack for a, Dry welding (no flux) , b, borax and other commercial welding compounds, c, WD-40 and, d, Kerosene. 


I use a coal forge for most forge work including welding. To determine if the metal is hot enough for the weld, should I look for the first spark and then weld or match the color of the wet looking billet to the coals under and around the billet? In the past when the first spark welding, when the metal was removed from the fire it burst into sparks. Matching the metal color to the background coke worked best.

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I've never done any other type of welding than what I describe there. I haven't decided I need to risk losing $50+ in steel yet. 

I have used wd40 (and borax) in weld flaws to try and close them up.... Did they close? Yeah, was it by luck or wd40? I couldn't tell you. 


Good luck! Hopefully Garry Mulkey sees this. I forgot, but there are pinned topics on this too btw, you might look around. 

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The short version is, for welding in coal use borax and don't let it spark.  A spark or two on mild steel doesn't hurt much,  but with high carbon damascus sparking is very bad.  


The dry stack is for gas forges running rich, and the WD-40 and kerosene are for cannister welds in gas forges.  

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I actually gained some experience with this in the summer although I am no where near expert.  I took a pattern welding class, and thought to myself that all of us in the class were bound to be speckled up from burns from borax splatters.  I was very wrong. 


The trick with welding without fluxes during the pattern welding class (using 1080 and a nickle alloy) was to make sure all the welding surfaces where ground flat to each other.  Tack weld them together, get your heat and smack it. We were using a gas forge and I am really impressed with how easily the welds took as I normally attempt to weld mild steel. 


Basically gagged the proper welding temp just by color. A uniform yellow heat, where all the layers looked the same color.  Pretty easy for low carbon alloys.  I did use flux at places where my welds did not take, but when I did use flux, very very little was required.  A pinching was all that was needed. 


You may see on the popular TV show that smithys pour flux over their welds.  That's a nightmare of burns coming from splatter. You only every need enough flux to make a sheen of coating over the welding area to keep it clean from scale.  


fluxless welding in coal, I believe I have two pieces welded without flux. At least the two pieces are stuck together, but not very strongly. You do however have a much better chance of the weld taking if you use some flux, for carbon steel alloys in coal, just remember that they do not need to be white hot to weld.  It maybe possible to do the same thing in coal, but no experience there. I asked my instructor "What if we used the coal forges for all this" his replay was "It would just be a disaster." Far to easy to burn up the alloys.

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I greatly appreciate the great information concerning pattern welding. 

From the information I have received, using coal throws a huge snag in the welding process. Namely, there  is a huge risk of overheating the blade.on the outside of the stack and having the interior too cool to take a weld. 

Just thinking, the size of the stack may be a major contributing factor in coal forge welding problems. If the stack is kept thinner, then the interior would have a much better chance to reach welding temperature at the same time as the exterior. Of course, thinner stack mean more cut and weld heats.

My propane forges won't reach Welding heat, so the coal forge is to my rescue.

I have been reading about dipping the stack in Kerosine

I have a lot of diesel fuel to run tests on instead of kerosine. Anyone tried diesel when welding in a coal forge?

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I have not.  I weld in coal all the time, and I use anhydrous borax.   The practical size limit of a billet depends on the size of your firepot.  I use a Centaur rectangular pot, and it can handle up to a 2"×2"×6" billet.  The trick to not burning it and getting an even heat is to

1. Use enough coal.  Huge deep fire.

2. Be sure it's coked. Green coal will ruin a weld if it's under the billet.  On top is fine.

3. Heat slowly.  I use a hand crank blower and for large billets it's barely turning until the billet is up to heat.

4. Watch it.  Don't stare into the fire,  but keep an eye on things.  

5. Know that you're only going to be able to weld two inches or so per heat.  Don't stress about it,  just weld what you can and back in the fire at full blast.

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9 hours ago, Alan Longmire said:

Know that you're only going to be able to weld two inches or so per heat


On the first welding heat on my billets, I weld the entire billet, hammer its whole length, which I try to keep about 5 inches. This "sets" the weld. Then every subsequent welding heat only achieves about 2 inches of solid weld, like Alan said, before its cooled below welding heat. 


I go fairly aggressive with the borax on the first heat, then slowly use less and less on each subsequent heat. After 5 or 6 welding heats, it's not necessary to flux anymore, assuming the welds took. 


This is just how I do it. Works well for me. I use charcoal by the way. 


A big part of learning to forge weld is to find a process that works for you in your situation and with your setup, and do that every time. Once you can weld just about anything using your process, then i would say experiment with things.


Hope this helps. 

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Alan is right on.  The purpose of  the flux  is to keep  oxygen away from the steel at welding temp as it will create scale almost instantly and contaminate the weld.  To weld  w/o  flux you have to  have a reducing environment (no  oxygen) which can't be done with coal.  


Remember to use a good, clean bituminous coal as a dirty coal will  contaminate your  welds.  The best that I know of comes from the Pocahontas vein. 


When I was first taught to  weld on coal,  my mentor used a mix  of 1/2 borax and 1/2 silica sand for a  flux.  I'm not  sure  that is necessary but it worked as the  sand melted into a glass which provided a great  oxygen barrier.


Good Luck and Happy Forging!

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Yeah, your mileage may vary, depending on how big a billet you have and how fast you are.


I forgot one major thing, though: you need at least 3 or 4 inches of coke between the air blast and the steel,  and another inch or two on top.  Don't get closer to the blast or you'll either burn the steel or scale it so bad it won't weld.

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