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Why won’t my welds stick?

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So I’m a fairly new blacksmith, self taught and I built all my own equipment including my propane Venturi forge.Things were going pretty well until I tried my first forge weld and I just cannot get it to stick, and I’ve tried a bunch of times. Here’s my method, hopefully one of you can tell me what I’m doing wrong:

 I take 2 squares of 6mm mild steel and clean the faces on the grinder using a 36 grit belt until they’re flat and shiny. I mig weld them together

Throw them in a preheated forge and let them get cherry red then take them out for a quick brush and a sprinkle of sodium tetraborate decahydrate around the edges. Back in the forge until white hot then out again for a few light taps with the hammer, more borax and back in. Out again when white hot for a few more (slightly heavier) taps with the hammer then left to cool.

I’ve attached a picture of the ‘welded’ faces of my last attempt to give a little more info, any advice greatly appreciated. Thanks

 

 

C34F1873-E936-48FC-8412-10DB7C97C7BD.jpeg

Edited by Mod30
Excessive double spacing.

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Forge welding is one of those things that's a whole lot easier to learn being taught in person by someone who does it regularly using a similar set up.  For one thing I cant seem to tell if the atmosphere in your forge is reducing or oxidizing.

Anyone in BABA you could meet up with for a little coaching?

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I have no experience of gas firewelding, (Don't want to damage my gas forge's lining) but from the appearance in the pictures, they were not hot enough right through, you have to allow the welding heat to soak completely through the joining areas.

Patience is the key, bring it up to welding heat slowly to allow the heat to penetrate/permeate right through, turn over if needed during the process.

This is relevant to both gas and solid fuel forges.

 

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You may find it easier to learn forge welding with less surface area between the two pieces as well.  This could even be folding a piece of square rod back on itself.  Once you get a couple successful welds under your belt you'll know the right look and feel and should be able to move to larger welds.   Also, the greater the surface area and the lower the mass of the pieces to be welded, the faster they will cool below welding heat.  The anvil can suck heat out of thin stock very rapidly.

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Next time sprinkle a LITTLE flux between the layers before you tack them up. At red heat steel oxidizes rapidly, especially with a coarse finish, 36grit is really coarse, I clean mine with a 200grit belt or file if working without electricity. 

Bringing the billet to red, even orange heat  before fluxing is a common practice but oxidization is occurring at a visible rate and as soon as you take it out of the fire to brush and flux it's cooling and drawing air between the layers. If you flux it cold, then tack the billet the flux will melt and form a prophylactic barrier on both faces of the joint preventing ANY oxidization at around 230f or so. You can just leave it in the fire till it's soaked at welding heat and it's ready for the anvil. If I'm welding in coal or charcoal I preheat the joint above the fuel so no crud CAN get between the pieces. 

I NEVER need the flux to flush out scale and inclusions, they don't form in my weld joints. 

Of course that's just how I do it, your mileage may differ.

Frosty The Lucky.

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The photo doesn't make sense to me in relation to your sequence of events.  I think we're looking at the two facing sides after you cut the MIG weld off.   If so, the visible oxide colors on the nice and smooth faces look like maybe a shade of bronze which would suggest you were hovering in the 500 degree Fahrenheit range which would be a black heat. Further, the edges of both pieces are really square and crisp.  In my experience, white hot is right on the verge of burning.  Just taking a piece of mild steel stock to that temperature tends to soften crisp corners a bit.  Then again, maybe those edges got squared up when you cut the MIG welds off.

This leads me to my last question, did you MIG weld all the way around the perimeter?  If so, I wonder if you got something weird stuck inbetween the layers that set up an inclusion for you.

 

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Look up some of Joey Vandersteeg's videos on YouTube. He forge welds on quite a lot of his projects, and he takes the time in some of them to really explain in detail what he's doing. Obviously not as good as learning from someone firsthand, but from watching his videos I learned forge welding early on. I still mess it up sometimes,  but when all goes well you can't see where it was welded 

 

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There's also a video by Mark Aspery titled scarf theory that might help. 

Pnut

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All good advice here. Watch a lot of videos, do a lot of practice with scarf welding rods, and be patient. The initial failed welds that are happening right now will teach you a lot. Examine them closely, and cut them open to see what happened.
 

When you get a weld right, which only can happen when your pieces are at the right heat (and it can be different from one steel to the next), you’ll recognize the needed level of color and also the amount of smoke coming off the surface. You also will come to realize the very different hammering feel when you do a good weld. The hammer blows, a light series of taps to set the initial tack, are dull sounding and the material is suprisingly soft. You can both hear and feel a good weld. 
 

 

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1 hour ago, MilwaukeeJon said:

You can both hear and feel a good weld. 
 

No one ever mentions that you can feel to a pretty good extent if you're getting a good weld. I don't do a lot of forge welding but I noticed right away the difference in the way it felt between a failed weld and the first successful weld I did.

Pnut

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Pnut, right on.. You can feel it for sure..   It's almost like a magnet between the 2 pieces..   the hammer will sink into the weld vs bounce at all. 

Best place to learn welding if on your own is with chain.. 

forge welding in a gas forge can be a tough one for many and the variable can be troublesome..   it's the reason why tack welded or arc welded tacks are used vs pieces placed just in the gas forge. 

In a solid fuel forge no reason to once accuracy gets good.. 

If it doesn't stick stop hitting it..  it isn't going to get any better. 

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Many thanks for all your responses and sorry it’s taken me a while to reply.

 

i think the most likely issue, what what I’ve read, is going to be temperature so the plan is to use a pyrometer to tweak the forge to the point that it’s capable of producing high enough temperatures 

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That should help although I've never used a pyrometer. For me, getting successful forge welds simply was a matter of finding a forge that could get my billets up to a bright yellow heat--almost wet, soft looking surface, smoking hot with a little bit of sparking at times. My little WhisperBaby just doesn't get there but my Diamondack and WhisperDaddy do. It was just a matter of me cranking up the flame/psi high enough. I think when I was first learning I was never patient enough to really take the piece up to crazy high heat. Once I did and felt that nice soft tacking weld take hold under my hammer, it was an epiphany!

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3 hours ago, MilwaukeeJon said:

 It was just a matter of me cranking up the flame/psi high enough. I think when I was first learning I was never patient enough to really take the piece up to crazy high heat. Once I did and felt that nice soft tacking weld take hold under my hammer, it was an epiphany!

I agree completely. And I can attest that a Diamondback will get to forge welding temps. Where do you set the psi on your Diamondback if you don't mind me asking. Mine was at about 18. I'd like to guage it by another's experience. Also, do you use a sacrificial brick or anything like that on the forge floor? I'd appreciate any feedback you could provide

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Have you burnt a piece of steel in your forge? That was the first thing I did the day I started trying to weld. That way I knew that the forge was capable of heating the stock enough to achieve a welding heat and I knew how hot was too hot. After burning the stock I knew if I failed at the attempt to weld it was on me but mainly I did it to watch the colors as it approached a welding heat. I don't know if anyone else has done this intentionally and like I said I don't Forge weld a lot and still am far from being able to do it consistently but practice makes for consistency. 

Pnut

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Chellie: The psi at which someone else's forge produces a particular temperature doesn't really apply to you where you live. There are a lot of location specific variables involved. You'll be much better served by keeping a notebook of your own forge, work and results. My too large shop forge has 4 T burners I  made on the lathe, they are as identical as I can make them and run off a manifold and single hose to the gauge and regulator. Each burner runs a slightly different temp, one is a golden bullet. 

When I weld a billet I match the faces then shine them up, an old 220grit belt for the final shine. When I stack the billet I sprinkle a little flux between each layer then wire or tack weld the billet. I preheat the billet at a lower than welding heat with a dusting of flux on the billet to watch for the melting temp of the flux, when It melts I flux the billet. I've never understood waiting until the joint is orange hot where steel will form scale the second it's exposed to ambient air. I can see it if you're using sand or dirt or plain borax . Borax melts at approx 1,300f. that's fast scaling HOT and if borax is all you have. . . However the flux I use contains boric acid with a melting temp of approx 340 f. which forms a prophylactic  barrier to contact with air. 340f. is WAY below fast scaling temp.

I buy commercial flux at a local welding supply and it works a treat for $26 and change per lb. can. I used to make my own but baking and milling anhydrous borax is just too much time when there is a commercial product that works better. You do NOT meed to melt borax to drive off the hygroscopic  moisture, an hour at 240f. is plenty. This is lab standards from "American Standard Test Methods" not some old geezer's opinion.

Back to the weld. I bring the billet to orange heat and let it soak before turning the forge up to welding temp. When the billet starts looking "wet" I ease back on the burners so it can soak with less likelihood of burning, I want the billet looking wet or watery depending on who's book you read. 

Soak time depends on thickness, blow pattern depends on width and length, I set the weld with heavy dead blows. 

I'm certainly not 100% but am usually successful if I take enough care to do it right.

There is NO magic to forge welding or any welding. the rules of welding are: Clean, CLEAN, CLEAN and follow the steps.

Frosty The Lucky. 

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2 hours ago, Frosty said:

You do NOT meed to melt borax to drive off the hygroscopic  moisture, an hour at 240f. is plenty. This is lab standards from "American Standard Test Methods" not some old geezer's opinion.

That's good to know. Makes it much less hassle. Thanks.

Pnut

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My pleasure though it will foam if heated too quickly and the hot water will sort of glue it together. I spread it on a silicone cookie sheet and put it in a cold oven and brought it to the "warm" setting for half an hour before raising the temp to 240f. I got a lot less foamy crust to deal with. The silicone cookie sheet or cake pan is easy to get borax off, just flex, stretch and crumble it. 

If you do want to melt it then find a small rock tumbler and some steel bearing balls to mill it. Trying to crush it with a hammer is just WAY to much work and not so effective. Toss the boric acid in the tumbler and mill it all together. It comes out dust but you can use a SS shalt shaker to apply it evenly. While you're driving off the moisture toss a couple small pieces of sheet rock in the oven too. The DRY sheet rock is an effective desiccant and will keep your welding flux from absorbing moisture from the air. It works for store bought flux too.

Frosty The Lucky. 

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pnut, yes I burnt the first chain link I made pretty badly. 2, 3 and 4 are mostly welded together, but they look pretty rough even after scrubbing the tar out of them with a block brush. I was just happy I got the welds as far as I did. 

Frosty, thank you for the great, detailed information. I'll take more careful account of what goes on in my own forge. I didn't even think about forges working differently in different environments. Thanks for your help. It has expanded my thinking by leaps and bounds on this subject.

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About the only thing a gauge on the forge does is give you a reference point to your forge, say when firing it up. I use the gauge to get close then adjust as nessessary by sight & sound. I once fired the forge not realizing the regulator was set at 20psi. A big surprise when a fireball rolled out the door.:o 

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