Forge welding with charcoal

[Nick]

When I was using coal I had gotten pretty good with forge welding.  It was never my strongest suit but I had a lot of success, especially with small pieces.  Now that I've been using charcoal, though, I can't get a good weld.  I've had ok welds, but that's not good enough and none of them have been clean around the edges.  There are several projects I want to do that I'm sure I could have done in coal, but until I figure out this issue with charcoal I'm stymied.

 

I scarf the ends, clean the surfaces, and try to clean out the ash in the firepot as best as I can, flux, bring up to welding heat, baisically all the things I would normally do, but there's always a seam visible, and I can't get the very ends to weld in and the welds are weak.  I may have started doing something wrong, but is there something about the charcoal fire that changes how I need to do the weld compared to a coal fire?  The only thing I can think of is that ash is getting in the corners and seams and preventing the edges from blending.  I'm stuck on a lot of things until I figure it out, which is quite frustrating! 

[ThomasPowers]

How deep is your fuel stack and where in the stack are you placing the item?  How large is your charcoal pieces?  How is it being blown?  Is your forge tweaked to burn charcoal or are you using a coal forge with charcoal?

[Nick]

Bottom blast with a hand crank blower, it's a Centaur Forge coal firepot and hasn't been altered for charcoal (using charcoal has been by necessity, but I want to go back to coal as soon as I can find an easier way to get it).  Trying to keep the piece away from the direct air blast, above the middle of the firepot, and have the fuel piled a few inches over the pot.  The charcoal is very uneven in size, but on average about chestnut size.  I can forge fine, and the charcoal is lasting longer than it did when I started using it, but I may not be shaping it right for welding.

[Dan C]

Something that is helpful to me is putting a charred log that has a bit of a cavity ontop of the pile so I have a cave of sorts.  It seems to retain FW'ing heat better this way and I can still keep an eye on it vs. burying the piece and then hoping I don't burn it up.   Also doing any FW'ing early on with a clean fire vs. trying to do it after a fire has been going for 3-4 hours.

[Frosty]

I find charcoal needs a considerably deeper fire to consume all the oxy. I use fire bricks on edge on bricks laying flat around the duck's nest to deepen the fire to a minimum of 6". That may not be the correct depth but works for me as a minimum depth. Small pieces of reasonably uniform size, I don't know how large a chestnut is but walnut is pretty BIG.

 

The sweet spot is higher in the fire, well above that in a coal fire, almost on top of a coal fire high. I've also had good luck using fire brick to build an oven over the duck's nest in my forges. I lay the brick on edge two+ high and cover the top with bricks. Leaving both ends open doesn't seem to hurt at all. The idea of the oven is to contain the heat and fire so it consumes the oxy more efficiently. It's a shaky set up but works okay if I'm careful about bumping it or pile charcoal against the outside to hold it. If I had enough brick laying them all flat would make a nice stable oven, I used what I had at the time.

 

Once you have a deep enough fire it's just like welding with any forge only cleaner. The only tricky thing I can think of is the depth of the sweet spot and charcoal's lack of doming capability.

 

Frosty The Lucky.

[ausfire]

Maybe that's why I have a lot of issues with forge welding. I use charcoal exclusively and it's a pretty shallow pile at that. I have never used coal so I am in no position to make any comparisons, but it may be worth trying coal. No idea where I could find some here though.

[skender]

Hi gents . I am a new member to this site. I have only used charcoal so I couldn't compare it to using coal . Frosty is quite right in saying that you need a deep fire to burn up the oxygen.the size of the charcoal pieces work best between 10 to 20 mm as also not to let to much oxygen through.It is a bit more difficult with bigger pieces .It is better to weld in a fire that has been burning for a while rather than a newly started fire.the charcoal fire I use is bottom blast 125 mm deep. The iron would be at the top of the neutral zone with a good healthy pile off charcoal on top. It is easy to let the charcoal fire get hollow in the center so you need to make sure you've got a bit stacked up around the edges as to drag in quickly when needed.I bring the iron to a heat that it is just starting to sparkle. I take it from the fire , and give it a quick wire brush and stick the ends into sand and put back in fire. Then get it to welding heat and close together. I have tried other fluxes but have had best luck with sand. It is really essential to make sure the fire is tight and not to upset it with the poker . I have a question that I hope someone can help me also with. I have been using charcoal for the past twenty years as we can't get any good coal in west aus. I make all my own charcoal as you cannot buy anywhere here. I have recently made a gas forge to reduce my charcoal consumption and am going pretty well with it although I find the scale is really thick and difficult to remove. I have no idea if this is normall or if I am tuning the gas and air ratios incorrectly .hope I was of some help . I have a video on YouTube under blacksmithing in Western Australia . We were training some of the members of the association and made an anchore using charcoal fires and old wrought iron picked up arround the local farms . It may be off some use to you?(Skender)

[ThomasPowers]

Sounds like you are getting too much O2 in the fire can you adjust the choke on the burner?  What hind of "dragon's breath"do you see with the forge running? (the exhaust plume coming out the front of the forge---tells if it's reducing, oxidizing, neutral.)

[Nick]

Thanks for the suggestions.  I'll try building the fire up and making an oven.  I've done something similar when forge brazing, since I need easy access, but with a steel plate on top.  I think a charred log would work better.  Won't be able to get into the forge until next week, though, so it'll have to wait until then.  I'll also bust up the bigger chunks before putting them in.

 

The charcoal is certainly cleaner in that there's no slag, but does that mountain of ash factor in? 

[Detail Man]

Sounds like you are getting too much O2 in the fire can you adjust the choke on the burner?  What hind of "dragon's breath"do you see with the forge running? (the exhaust plume coming out the front of the forge---tells if it's reducing, oxidizing, neutral.)

Would you please elaborate on the "dragon's breath"?  What do reducing, oxidizing, neutral plumes look like?

[Frosty]

Skender, Detail man. How about putting your general location in the header you might be surprised at how many of the IFI gang live within visiting distance.

 

Skender: If your gas forge is making scale in the forge the burner is too lean, either reduce the air intake or increase the gas. Turning up the pressure on the regulator on a naturally aspirated burner isn't going to richen the flame as the air intake is determined by how much and fast the gas is flowing from the jet. Without swapping out jets, mig contact tips I hope for easy's sake you can use a torch tip cleaning file set. Just pick one that barely fits in the orifice and put it to work. Once it's moving with minimal cut, you can feel them cutting, test the burner in the forge. If it's still too lean pick the next larger tip file and repeat, always test before you move to the next size, a couple thousandths can be the difference.

 

Detail man:

 

Dragon's breath is the flame fueled by unburnt propane as it escapes the forge door and gets a little oxy from the room air. You should get a LITTLE orange dragon's breath from the door. This indicates there is a LITTLE excess fuel and all the oxy has been burnt. Some guys have good results with blue dragon's breath, getting it fine tuned is up to the end user.

 

WARNING WARNING WILL ROBINSON!!!  Any appliance that's burning anything produces exhaust and that's full of bad things to be breathing instead of fresh air. The most dangerous is CO Carbon Monoxide, The hemoglobin in your blood likes CO better than O2 and accumulates in your blood. Gas forges produce a LOT of CO and if there's dragon's breath, especially orange dragon's breath it's producing lots MORE CO and you better be on top of good ventilation and have a CO monitor installed and running.

 

When I say CO is the most dangerous thing in the exhaust from a forge that is NOT taking into consideration what you're heating. Do NOT heat galvy steel, gold colored bolts, chromed anything, etc. The fumes from burning metals isn't how you are evolved to absorb the ones that ARE necessary nutrients, minerals, etc. Some metals like cadmium and chrome are carcinogenic in the extreme besides being just plain very toxic. Even some "plain old" steel contains things like copper, molybdenum, cobalt, on and on, so you want good ventilation regardless. Stay away from ANY plated metal, ANY. If you want to KNOW what's in it, buy new.

 

Hey, that turned out pretty long but I think I covered two questions. . . I hope. <grin>

 

Frosty The Lucky.

[ThomasPowers]

2 of my propane burners have a plate I can move to choke the burner.  The other I use a pipe clamp and slide it down over the air inlets as needed.

 

I'm always amused by folks asking if it was ok to forge in their garage because they have *1* window open for ventilation.  Myself I have 2 10'x10' doors on opposing ends of the shop the main direction of wind in our valley plus the gables are totally open plus I have some ridge vents.  CO is sneaky, underhanded, mean, tricksy and DOES NOT PLAY NICE WITH OTHERS!  As I like to forge knives and so often run a reducing forge I'd rather err on the side of living to see my great grandkids!  (even minor exposure can have issues---see the studies done on smokers...)

[skender]

Thanks frosty much appreciate info on exiting flame . I reckon I am fairly close to what you were explaining and need a little fine tuning. The burners I made are similar to the Michael Porter desighn with a sliding choke .I am arking up the fire this morn and will play Round with air intake. I have made with mig tips so have been experimenting with .8 and .9 tips or (.30 to .35 tips).I have been putting off making a gas forge for a lot of years but am happy so far with the heat I am getting from this little fire. Nick , I havnt had to put anything on top of our charcoal fires to forge weld. Me and another older fella that taught me how to work with charcoal go to perth to the west australian blacksmith association and teach forge welding classes. We normally have 8 fellas working and they all have a charcoal fire to work on. For example I will start with the fist guy and get his fire right and within 15 minutes he will be producing fairly good welds. I would make my way through the rest of the students and finally get back to my first student who by then is in all sorts off trouble with manky looking attempts at failed welds. The problem always seems to be that they have let there charcoal burn to low and hollow. As soon as we get the fire built up again we are back in welding buisness.I don't know what's it's like to weld in coal but I do know that with charcoal the fire has to be perfect to get results. I personly have a lovely decoration of dents around my tin shop wher the hammer has been thrown through the air in frustration over the learning years. I have watched lots of vids on YouTube of coal forging and would love to have a go at it but have tried but cannot get hold off here. I am 3 hours drive fom perth in the south west of Aus .charcoal here is like gold. if you get time to watch the video I mentioned you can see we are welding 2 inch x 2 inch bar on fairly small fires . I had to constantly stoke fire up.ok am going back to get gas fire going to see if I can adjust without poisoning myself .(Skender)

[Frosty]

I have my best luck using a 0.035" contact tip in 3/4" burners. The more guys who build the things the wider the range they're getting to work well so I can't say what IS the right size anymore.

 

That's right, NO POISONING YOURSELF ALLOWED! If you kill yourself Glenn, or any of the other Admin guys for that matter, will kick you off IforgeIron as soon as they find out. It's against the rules, follow the rules!

 

Frosty The Lucky.

[skender]

Spent this arvo studying the colors of the Dragons Breath. They were mainly blue with faint orange tips. I adjusted gas from 10 , 20 and 30 psi. I tried adjusting the the choke in all ranges . I opened and closed the rear door on the forge and I must be going blind as the colors didn't change at all. Only noticed that the more gas THE BIGGER THAT DRAGON BEARED DOWN ON ME . The forge is 10 inch ID and 22inches long . I have made it to take 2 three quarter inch burners but only have one burner in at the moment. Tomorrow i will be forging some pretty heavy bar (2 inch dia ) so I think I may have to just experiment with air intake . Realy tempting to push that dragon into the cnr put a muzzle on it and fire up the charcoal but must persist . With all your well appreciated help I may even learn how to use this thing .

[Frosty]

Faint orange tips on the dragon's breath is right.

 

Is 10" the inside diameter of the chamber? That makes it a bit more than 1,700 cu/in and a candidate for 4 burners if you want welding heat full length. It's unlikely you'll ever need welding heat on 22" of stock, right now my imagination is running away trying to think of what I'd do with a piece that long that hot let alone how I'd handle it. Sounds like fun though, probably a fun ONCE thing though. <wink>

 

Do you really need that much diameter? The length is easy to adjust, a movable back wall is common enough, I can and do move side and end walls in my forge as a matter of course.

 

Frosty The Lucky.

[skender]

Didn't get a chance to fire forge again . Got bogged in paperwork and charcoal making. Yes frosty the internal diameter is 10 inches and 22 inches long. I made this forge in pure desperation after the fires Nearly stoped burning due to lazy organisation skills while moveing workshop. Figured I didn't have storage space while between moves and let stock dwindle. Just so happened when I got back to working the forge it was the middle of summer here. Fiiiiiireman said no can do. I made the forge as big as I thought would work as to try and get all sorts of shapes inside. Oxy and LPG is verry costly for us and I try to do all or most of my work in the forge and only pick up the oxy for tweeking . Most of my fuel is wasted by doing long draw downs under the hammer. My reasoning was that larger peices off stock could be put in the gas fire and switched to the charcoal to get final white heat to work.Just so happened I found this site and followed a conversation you were having about gas forges with another fella.I seen the pics of your forges and could have kicked myself as would be a better design for what I needed it for. Anyway! Got to start somewhere. On saying all that , it was the sizes of similar forges in Michael Porter book and am verry surprised at the heat I am getting. It does get verry near a welding heat when it's been running for an hour or so. He did mention in the book about putting baffles in if only using half the forge so will have to make one .All my forge welding would be done in charcoal although now I've come this far would be great to be able to get a weld in the gas. Will have try a smaller fire with these burners. Will let you know how it goes when I put the second burner in next week. ( Skender)

[skender]

Finally got back to the fire. Thanks Thomas powers , I adjusted the choke and scale was thin and wire brushed of easily. I reckon you are right frosty as I do believe this size forge could do with an extra burner or two to get max heat . Did well though with 50 mm bars . Got enough heat to forge under little hammer.I did trash the the forge itself though. Broke the bottom bricks and tore the kaol wool on sides. Need to learn how to be gentile. May have to get lessons from my wife. (Skender)

[ThomasPowers]

One trick I have used when wanting a Zero Free O2 forge is after adjusting the choke as much as possible I cover the floor of the forged with a layer of crushed industrial coke.  For even more extreme situations I have placed a piece of pipe in the forge with one end closed off and put in a layer of crushed charcoal in the pipe and let the pipe heat up to make a "muffle furnace" from either my propane or coal forges---with coal it helps to rotate the pipe to get the entire surface up to temp before placing a blade in it.  (and yes blades for heat treat are generally when I want to control the atmosphere as much as possible.)

[Frosty]

Skender: When I said "Oxy" I was referring to atmospheric oxy, (fresh air) not bottled oxy.

 

A bit of experience to share, unless you're going to be twisting or scrolling a length there is no, ZERO good purpose to heating more than a few inches at a time. Even using a power hammer, 50mm (2" +/-) heating more than say 4-5" is wasting fuel. The only thing you can forge is what's under the hammer.

 

Once you get your forge volume within the operating range of your burners you won't be needing anything else to bring it to welding heat. If I turn mine up it'll melt steel if you're not paying attention. I sometimes turn it up for students who don't pay attention after they've invested some work in the stock.

 

Regardless your burners will get more than hot enough to weld once you get the forge in range. Putting charcoal, coke, etc. (carbon) in the forge will scavenge free oxygen from the fire. It works well.

 

Frosty The Lucky.

[HWHII]

Nick, did you solve your problem yet? Haven't been on in a bit. I have had a awful time learning to forge weld with charcoal. Like others have said deep fire. I made this u shaped piece for the forge I have been using and it made all the difference. When I am running this full above which is 4" tall 1" bellow and 1" above for a 6" deep pile. A charcoal fire to me can be tempermental. You can have a good welding heat and the next heat in the same spot not.

[Nick]

Not yet, but I haven't been able to work in the forge enough the last couple weeks.  I'm going to keep working at it, though.

[Rhyfelwr]

I've welded in a charcoal fire, I didn't have too much trouble. I use a hand crank blower and I learned to gradually bring the heat up, seems to me that when I was in a rush to get things hot in the charcoal forge I burn them up or they scale up. I used plenty of 20 mule team borax, and I made sure my welding surfaces were clean as I could get them. Also my forge shape is very conical with a single point for the air to enter, meaning my heat point is fairly predictable.

 

I welded until I couldn't beat my test welds apart, I probably need to start doing it more often to keep the skill up.