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Identifying a bad weld...


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Alright, so every now and then I get some baaaad welds, and I thought I'd just confirm with you guys whether or not this is a good way of eyeballing a bad weld early on:

Flaw 001.jpg

As we cal see from the pic above - a piece of the top layer of steel has a different heat color than the rest of the billet. This made me suspicious....

Flaw 002.jpg

And as I grind the bastard down - there you have it... Bad weld....

Flaw 003.jpg

I didn't want to take any chances - so I put the angle grinder to it and cut off every last trace of that bad weld.

 

However - a question for you guys; is there a better way of doing it? Can one simply just heat the billet hot as hell, and make it stick? Note that all of these steel pieces were clean as a whistle before I started - so I assume the bad weld is because of temperature and not clank or anything.

 

Sincerely, Alveprins.

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Ehh, what you did is what I do. However, a bad weld can always happen. There's a reason PW'd steel is much more expensive. I believe someone (Alan?) had mentioned that you can sometimes fix a bad weld with a sugar and flux mix (don't quote me on this), but doesn't really help with this type of bad weld.

Edited by Austin_Lyles
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This is what I do when I have a problem like this. I have used the sugar/flux trick, but only on multi bar blades. Otherwise, it just isn't worth it. In my experience if the weld doesn't take the first time on a billet like this, it probably isn't going to take no matter what, even if it does it's likely to come apart again when you are drawing it out.

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Thank you very much for the replies guys. I suppose I will keep doing what I'm doing when experiencing bad welds like this.

I am curious though - this sugar/flux trick... How exactly is it done? :)

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1 hour ago, Alveprins said:

Thank you very much for the replies guys. I suppose I will keep doing what I'm doing when experiencing bad welds like this.

I am curious though - this sugar/flux trick... How exactly is it done? :)

Take a some regular sugar like you would use for cooking and mix it in with your flux. The ratio isn't very important, but about two parts borax to one part sugar works great for me. 

How does it work? You sprinkle it on just like flux, and when the sugar gets burnt at welding heat the surface of the steel absorbs some of the carbon, lowering the welding temperature on the surface of the steel. Also, it makes your shop smell like marshmallows! 

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Exactly.  I learned that from the late Larry Harley, who also showed me a last-ditch way to fix an unwelded layer on a flat bar or blade, provided it's just a flux pocket that is indeed welded all around the edges: take a very sharp punch and poke a hole (hot!) in the unwelded spot as soon as you see the telltale darker spot show up, then reweld.  If the edges are delaminating like that the grinder is the only way I know to fix it.  Was that a fluxless weld?

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Yeah the uneven color as a billet cools often tells me if there's any issues. I don't get unwelds like that very often at all, but I do sometimes get blisters from my initial weld, typically 10-12 thin layers.

 

Yep, Alan, that's what I do too, more or less. I cycle the billet hot to cool to raise the blister, and pop it with a punch. I enjoy the pretty blue flame that usually shoots out and then lightly flux it, reheat and go in with a broad faced ball pein and lightly spiral from the edges to the center of the hole, then flux and flatten a bit. I've never seen a resulting flaw in a finished piece.

 

Never tried the sugar trick.

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1 hour ago, Alan Longmire said:

Exactly.  I learned that from the late Larry Harley, who also showed me a last-ditch way to fix an unwelded layer on a flat bar or blade, provided it's just a flux pocket that is indeed welded all around the edges: take a very sharp punch and poke a hole (hot!) in the unwelded spot as soon as you see the telltale darker spot show up, then reweld.  If the edges are delaminating like that the grinder is the only way I know to fix it.  Was that a fluxless weld?

Yes indeed it was. :)

 

I just got back from the forge, and noticed a trend. When not using flux - some of the welds are bad at the very edges of the billet.. That is - the "sides" of the billet. It's not so bad I wasn't able to fix it though. I think I will flux for the next step.. I am close to finishing the forge welding now.. :)

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