mcb

First serious attempt at forge welding, failure...

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So I have a new gas forge and after a few session to work out the kinks I made my first serious attempt to forge weld some steel.  I was not trying to make anything specific, just trying to learn the welding process.

My process was to clean a piece of steel especially the surface I was folding to attempt to weld.  Heat it and notch the underside with my hot-cut.  I then folded the steel onto itself at the notch making sure the two half were tight to each other.  Another moderate heat and fluxed the edges to seal the welding surfaces with Borax.  I then put it in and got it as hot as my forge would go.  I took it out and with moderate blows drove the pieces together before it had lost much color a reheated and repeated a second heat with moderate blows.  After a third heat I switched to pretty heavy blows and then tested the weld.  In all three attempts I got no weld at all.

My first two attempt were with some low carbon steel probably 1018 or 1020 (Home Depot stock).  I had heard/read higher carbon steel welds at lower temperatures and so my third attempt was with a scrape of car spring.

I am fairly color blind and working outside in the hot Alabama sun and those two challenges makes it hard for me to read the color/temperature so I bought myself an infrared thermometer rated to 2700F.  The highest temperature I had on my parts was just over 2100 F.  I suspect this is why I was not getting a weld but wanted to see what you guys thought.  Am I hot enough?  Am I missing something else?  Thanks in advance.

 

 

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2100 degrees F is good enough for forgewelding, but somewhat on the low side as once you take it out of the forge it start cooling down very quickly. Especially for mild steel; you are looking for that yellow-white hot. Your forge doesn't look hot enough on the inside.

If you are using borax; you need to look at it, and when it start bubbeling like boiling all over the piece (including the underside and inbetween the layers); you are at forgewelding temp on the outside of your billet. Give some time to soak then forgeweld. There should be enough borax so the whole billet looks wet.

Your choice of materials is also ... questionable. Mild steel can be forgewelded; but since you don't actually know what it is; you can never be sure. I've had large bars that just wouldn't forgeweld at all, later I found they had added lead in the steel composition to make it more malleable and machineable.... 

The leaf spring is pretty much the same.  I've had leaf spring for cores of laminates; I've used leaf springs in damascus. But I've also found leafsprings that just wouldn't weld together. This is typically with chrome in steel. I've always had trouble to weld chrome or nickel steels to themselves. I usually add a layer of something like O1 or 1095 inbetween, makes welding a LOT simpler.

So if I may give you some advice;

1. Use something really simple like clean ground degreased O1 / file billet. Don't weld something containing chrome or nickel to itself. Keep the chrome containing steels for later when you've mastered this. 

2. Make it really REALLY hot. The borax should be bubbeling on your anvil when you're hitting it.

3. I've learned most students the 3-welding heats principle. First welding heat; light taps, one side only. Basically just "set" the welds. Clean, flux. Second welding heat, on the other side , somewhat heavier taps, you should "feel" that the billet becomes one piece. Clean, flux. Third heat, hammer all you like; even on the sides, it should stay together and act like one piece of steel.

Hope this helps.

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That home Depot weldable steel unless marked as 1018 is actually A-36. I don't think that has a lot to do with the weld failing though. As already mentioned above, your forge doesn't look to be in the incandescent orange/White heat range, but it's in full sun and photos are notoriously hard to judge color with.

I've heard a lot of people having trouble welding leaf springs to themselves. 

I would try again after the sun is setting anit's a little easier to see the colors. At my forge in full sun a welding heat looks medium orange and a lemon yellow tends to look like a high orange. It's tough judging color outside. Find something you can put the steel in that's dark like a wood box with a small hole In for the steel to get back to where it's dark enough to truly see what color it is. Even being color blind it's more about incandescence than color. White light is brighter than yellow and yellow is brighter than orange.

Pnut

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Thanks guys that was very helpful.  I will see what I can do to get some known good tool steel or high carbon steel without nickle or chrome.  I will also see if I can get my forge a touch hotter too.

The hard to read colors working outside and my eyes is why I bough that IR temperature sensor.  I am guessing I need to be seeing 2200-2300 degrees in the forge to have the steel hot enough to weld by the time it gets to my anvil.

I think I might need slightly larger diameter fuel nozzles as I still think I am injecting the fuel too high of a velocity drawing in too much air in with it in my burners.  It's hard to get a reducing flame even with the airflow choked way down.  It goes from neutral to extinguished with very little reducing flame in between.  Fatter nozzles might let me get more fuel into the forge without overdoing the air too much.  When I first built the forge I was using .025 MIG tips as nozzles going to .035 made a noticeable improvement to the temperature.  I have a bunch of extra tips so I might drill some out to .047 and see if that helps get my temperature up a bit more.

I also need to get my propane tank into a large bucket of water, about half way through the session I froze it pretty hard and that was hurting my fuel output too.

 

 

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For temp judging in daylight, a large pipe or can allows you to put the hot steel in to the shade. 

Second, the 3 things you need to forge weld is flat (well matched surfaces) clean (chromium and iron oxides will foul you up) and of corse heat ( think of it like tosting a marshmallow if you do it right the outside gets light brown and the middle gets hit and gooey)

. Now the first blow tends to drive the surfaces together and make the matched surfaces. Their are some other factors like avoiding heat risers and making sure you have enugh meat as you inverably draw out the stock.

heating, especialy in gassers tends to generate scale, so heating to use your hot cut needs to be fallowed buy wire brushing off the scale, then cut and befor fully folding ad flux. The molten flux will be driven out of the weld zone along with any scale you missed, but wile its their it will prevent scale formation during the welding heat.

third, slowly roast the stock to get it hot all the way threw. Do not rest the hot stock on the anvil, hold it just above, don’t hesitate. 

Now A36 is Little beter than rebar as its not a steel formula but an engineering spec. So some times it won’t weld no mater what you do as their is no telling what scrap went in to its manufacture. This can acure in the same bar (drill six holes in the stuff and one will be hard and dull the drill!) the addition of sal amonic to your flux mix helps weld Crome steels like automotive leaf because it melts at a lower temp (were chromium oxide scale forms). 

Clear as mud right? 

 

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Thanks, the mud is getting at little more watery at least.

I did not flux inside the joint I was trying to make only fluxed after I had put the two surfaces together, so that no doubt did not help my attempts.

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I'm a little suspicious of that IR thermometer.  Get a small piece of cast iron and place it on a chip of hard firebrick.  That is a much better indicator of forge temperature for now.  If it doesn't melt, you're a little cold.  Also, pull those doors shut a bit.  If you want to weld high carbon steel, don't use leaf springs.  Many of them are not simple alloys.  Do a spark test.  Instead, start with a file, sandwiched in a folded piece of mild steel.  Try using an old garage sale file like a Nicholson or Simonds.  Some A-36 (modern mild steel) has a difficult time welding to itself.  Also, do a stick test with two coathangers.  You cannot miss that little sticky feel.  I have to get things just right in my propane forge.  It is kind of iffy.

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I never flux between the layers, but as soon as I see colourchange - dark reddish - I start to put flux on it. At first once molten it's like thick sticky goo; but as flux gets hotter, it becomes as thin as water. If your billet is well fluxed, it will "flow" inbetween. and once it starts bubbeling and boiling; you're at the correct temperature.

And your forge really doesn't look hot enough; so I share evfreek's opinion on the IR thermometer. Can you verify that thing with an actual thermometer with a K-type thermocouple ?

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The IR thermometer seems pretty close at lower temperatures.  Ice water. boiling water, some eutectic alloys I have and a 750 deg temperature stick I have all come out at the right temperature on the IR thermometer more or less.  When I first got it I heated some metal with a propane torch and inside my shop the color and temperature seem pretty close to what is expected up to what a cheap propane torque could do.  I would not be surprised if it was off by 25-50 degree at 2000 deg but from my experience its relatively close.

That said even if we assume the IR thermometer is right on the hottest temp I got was just over 2100 deg and from the feed back here and other reading I think I am going to need to see temps closer to 2300 deg inside the forge to have a chance of welding at the anvil.

I have a couple old files in the scrap bucket I was saving for various projects.  I will cut a chunk off one of those and try to weld it to some better quality mild steel on my next attempt.  Assuming I can get the forge a bit hotter with a nozzle change or some other improvement.  Thanks guys!  keep the suggestions and feed back coming its is greatly appreciated.

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13 hours ago, BartW said:

1. Use something really simple like clean ground degreased O1 / file billet. Don't weld something containing chrome or nickel to itself. Keep the chrome containing steels for later when you've mastered this.

Psssst.........    O1 is a chrome containing steel that also can air harden when working, not a good choice for a new smith

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Over the summer i have been working on welding. I have gone from about a 50% failure rate to around 10%. One thing i have found that helps me is that when i set the welds i do not hit the metal as much as "press" the metal. I try and not let the hammer rebound basically. 

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Light taps.

And indeed, O1 contains very little chrome, but as long as you aren't welding it to itself,  it should be OK. and the Manganese makes really nice black lines in damascus after some instant coffee etch :D 

 

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Steve forge welds some difficult aloys into knife and sword billets,  he is certainly on my “if he speaks” list. Certainly not the only one, but one for sure

 

 

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Made another attempt this morning.  First thing I did was switch out my burner nozzles.  At first I tried .055 and that just turned my forger into a orange ball of fire burping monster.  Shut it down and put in .047 diameter nozzle and that seems to be pretty close to a sweet spot for my forge.  Using the same IR thermometer I was able to hold 2200F with a peak of 2265F.

This time I folded a piece of mild steel over and in the fold put a piece of high carbon steel from a file.  I had ground off the teeth and cut off about 1.5 inches of the the file and ground the mild steel clean too.  The piece of file got tucked into the folded over end of mild steel. No pictures of it but the folded mild steel covered only about half of the top of the piece of file.  Heated it until just starting to turn red and then applied a nice coating of Borax flux.  Back into the fire and watched for the Borax to bubble.  It did not bubble as vigorously as I though it would so I almost missed it but it did bubble and out it came for firm controlled blows with the hammer.  Before it lost too much color it when back in for a second heat and then slightly firmer blows.  A final third head and heavy blows and I had a pretty good weld it seemed.

I cut the side off the weld with my grinder to expose the weld seams and it seemed to take pretty good.  I decided I would attempt to make a small wood chisel from it so I ground the mild steel off of the top side leaving the high carbon steel exposed on one side.  I then drew out the weld layer to nearly twice is original length.  Figure if it didn't come apart doing that it was a decent weld.  I ground off the scale on the edge of the weld and used a sharp file to clean it up and you can see the weld interface and the small separation at both  ends of the weld.  I will grind those out when I finish rouging in the file.  I ran out of propane.

Thanks for the all advise and suggesting guys.  That weld might not be pretty but it would not have been possible at all without your feedback.  Thanks for all the help!

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Very nice. looks like a very nice usable chisel after some clean up. Congrats. Feels good doesn't it ?

Did you notice the difference in reaction to your hammer blows ? Once a weld is set; it feels like a solid piece of steel under a hammer; before it feels different .. more mushy, less rebound.

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Thanks BartW,.  I have been playing with the blacksmith hobby off and on for the past 4+ years and this is the first time I feel more like a hobby blacksmith and less like a goof pounding on hot scrap metal.  I still have lots to learn but it felt really good to succeed at this one skill.  It expands the realistic projects I can attempt by a nice notch and that feels good too.

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I don't think it's been mentioned here yet. 

Scarfing is one of the most important aspects of any forge weld.  A square edge going into a flat surface if the thicker piece is the square edge will create a shear zone at this point. 

on another note and as an example:

I try to show how 2 separate pieces when placed together at welding temperature when the temps are just right and I lay the pieces on top of each other. They will instantaneously (like a magnetic pull) will be joined before even being hit with a hammer. 

the hammer merely helps to push out any flux or other crap stuck between, and initially I use very light quick blows. Again driving out what ever is stuck between the pieces. 

Forged a hatchet yesterday at a meet and the eye weld popped some as I entered in an eye drift nearly 2X to big for the amount of metal forcing it in and apart. 

I then kept at it as I massaged the metal around the eye with still one smallish section holding that weld.  I then welded the split part back together even without cleaning it all up and filing the areas clean. 

Technique has the larges effect on the weld. Understanding how or why it works becomes on facet rarely talked about. 
 

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Thanks jlpservicesinc, that makes total sense and with that knowledge I can see where the lack of a scarf in my weld has cause problems.  I will be sure to scarf my next weld.

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