Weld fail

Jonathans

Jonathans

Joined
Jan 9, 2008
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588
I tried to make a RR Spike Tomahawk with a piece of 5200 hotdog welded in for the edge. Mostly a project to learn how to drift the hole well, and it was my first forge welding experience. The hawk wa a total failure, but I learned a lot. The one area I can use some direction in is why my weld didn't take well.
I spit the end of the blade around 3/4" and inserted a tapered piece of 1/8" 5200. Hammered it just snug, brought it to dull red and flexed it with borax. I then heated it to bright orange and hammered it hard.
The weld took at some spots, but not completely at others.
Was it not hot enough? Should I have been wire brushing it?
 
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5200 hotdog..?
Don't hammer hard to set the weld....the blow should be a "clunk"....heavy enough
to deform the steel , but not hard enough to rebound.
 
Bright orange isn't very hot, when you're talking about welding. Go for yellow/white.
If you're using gas, the main problem most people have is too much oxygen- your forge should be shooting just a bit of yellow flame. The guy that first taught me years ago always said, weld on a rising heat.
If you're using coal, it may sparkle just a bit when you pull it out of the hot spot- it's tricky, too much and you're burning it.
Let us know what your process is, perhaps you'll get just the tidbit of advice you need to tune it up.
 
I'm not slamming the the hit, just a good hard hit.
My forge is a propane blown Ellis. I generally have been turning the gas up until there is dragons breath and then opening the blower gate valve until the flames pull back in. I'm not sure how to adjust to get the hottest temps. More gas and more air?
 
My Chile Habanero will weld at like 4 PSI, 5 tops with the moderate dragon's breath thing going on. Is the spike low carbon, because that requires a bit more heat. but blacksmiths weld low carbon to low carbon all of the time. I well suing my press and I always do two welding passes and then do the initial drawing at pretty close to welding heat if not at it. My first thought was that the chrome in the 52100 might make it a bit more tricky, but then I remembered that a number of folks forge weld L6 bits into mild steel axe heads. Watch some of hose videos to see what kind of color you should be going for. You should also be able to see how your flux should be dancing around at welding heat.
 
Wish I could help, I'm not knowledgeable about venturi forges. Ask me anything about coal and blown propane :)
The thing about "rising heat" means not letting it sit too long in the heat getting oxides, once you get it roughly dialed in- enough flux and a rich enough mixture helps with that, though.
 
For an initial weld on a 2 1/2 to 3 inch tall by 6 long by 1 to 1 1/2 wide stack using 1/4 1084 and one or two pieces per layer of .065-.095 15N20, I put it in the forge and leave it for as 10 minutes for the first weld (using kerosene as "flux") and at least five to six on the second welding pass using borax to seal up any edges that might need it. I turn the billet a few times while it is heating, No worry about oxides as the borax creates a hard, abrasive belt and wheel destroying protective coating. :D
 
Using a blown forge (it's my understanding that you are) welding heats could certainly be possible at 1-2 psi. My blown vertical forge will weld well at 1.5 psi. It's less about the psi than about how the forge is actually responding. I'd say, run your forge up to a high orange heat and let it stabilize for a few minutes- then add a bit more gas and air, dial a little dragon's breath out the doors, throw a bar of mild steel in there, and see if it'll get it up to a yellow heat. Put some flux on the bar, and see if it dances around and if the steel looks like a stick of butter just short of melting. Fold the bar back on itself, flux, get to yellow, and see if you can stick it to itself with the hammer. Make a little pick out of some TIG rod or a coat hanger, poke that into the forge, and see if it wants to stick to the bar stock when held against it. Lots of ways to see if you have a welding heat, the main point being maybe don't try it right out on a project or knife that you want to finish.
 
Elementfe, it is a blown propane forge.
Thanks for the tips and advise Salem. I'll try that this weekend.
 
Most everyone does one of two things on their first few welds:
1) Not heat it nearly hot enough to weld (especially when using propane).
2) Burn it up (especially when using charcoal).

Welding takes practice. Some thongs that help:
1) Make everything clean.
2) Make everything it well.
3) Don't over flux. Flux can get in the way of a good weld. Look into hydrocarbon fluxing once you learn the basic welding method. No flux is a good thing.
4) Brush the billet with a stel wire brush before each weld, and after each heat.
5) Check to see if it is ready with a coat hanger. It will stick to the billet when poked hard against it (in the forge) if the billet is ready to weld.
6) Strike while the iron is hot. Steel welds a LOT hotter than it forges. Weld at 2200-2300F ( forge at 1600-2000F). Start with smooth and light to medium hits. Only work the steel while in the yellow heat at first. Weld from end to end, re-heat, then re-work the weld at least twice more. On the third welding heat, as you feel and hear the thunk become more of a whack, then you can increase the blows to more powerful. Striking too hard in the beginning will mush the steel and it may never weld again. Even the first couple drawing heats should be somewhat gentle.
7) Quit when the steel isn't hot enough. Don't weld down past orange. If you strike the steel below welding heat it will split the existing weld...and it may never weld again.

8) Biggest tip:
If you can see the weld as a distinct line, it isn't welded. A billet that is properly welded looks like a solid block of steel. If you see dark and light lines where the weld is...weld it some more. Don't think the weld will get better/stronger when you draw it out....it won't.
 
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