forge welding

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tattooedfreak

Steel mutilater is more like it.
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Ok, I have a question. I have read in a number of forums (blade and blacksmith) that if you have had copper or brass in your forge you will no longer be able to forge weld steel/iron. If this is true, can anyone explain why? If you can weld SS and copper together (for mokume) and others, why would copper/brass in a forge have an effect on simple carbon steels?
 
I personally have found this to be not true in my about 15 years of being a farrier/blacksmith, I am always brazing on horseshoes in my forge using either copper or brass to attach borium or caulks and on the next horse I can forge weld a barshoe or jump weld a toe clip or another shoe modification to a horse shoe. I have done this in a both propane forge and a coke forge and before I made a dedicated bladesmithing forge I was even making damascus in the same forges.

I have no idea why people say you can not forge weld afterwards but here is another thought, with flux on the weld keeping oxygen out how will other impurities get in and stop a weld?

Maybe someone else will be along with some useful info as this is just my personal experience.
 
I always wondered about it, I have read it in at least a dozen posts on various site, and even one that talks about a visiting blacksmith tossing in pieces of copper or brass as a joke when the local guy wasn't watching. I just couldn't figure out what it would do to the forge to stop any weld from sticking. At first I thought it might be some fume that would linger in the forge lining but at the heat required I couldn't see it.
 
I have never understood this story either. I use brass, gold, silver, steel, copper, and iron in my forge, and it welds just fine. I think it is one of those urban legends that everyone tells, but no one really ever experienced it...sort of like Spanish Fly.

Someone just the other day posted on a thread that some smiths would punk a friend's forge by tossing in a piece of brass or copper when no one was looking,..... and making their friend's forge never able to weld again. Besides being a ludicrous story, if it was true, they would be asking for a hammer up the side of the head for putting someone out of business.....some friend they would be.

Copper has been used by blacksmiths to braze together iron and steel for centuries ( sometimes called a penny weld), so I don't see why a few stray atoms would stop any welding of damascus. Metallurgically, it may even help the weld.
 
The more I thought about this today I realized it is actually just a way for a guy that can not forge weld efficiently to put a blame to his lack of ability to forge weld ;) :p.
 
however the tin in spilled bronze in my forge made 3 bars of 1084 go red short in 2 heats, once I changed out the bricks with the spilled bronze on them the other ends of those bars in the same forge worked fine

I asked the head metallurgical engineer at the plant I worked at what was going on thinking it was the copper in the bronze (copper shavings in superalloy melts destroy the metal in parts per million concentrations, yet we melt in copper crucibles) and he said it was the tin diffusing into the steel

-Page
 
I posted the thread with the comment about the dirty trick--I never said it wouldn't weld ever again, just for that day, and I should have clarified that it was on coal forges.
If it's an urban legend, and I'm not contesting that, then it probably arose from situations such as sunshadow describes. Likewise, The piece I posted in that thread shows definite copper transfer despite the fact it never came into contact with any except right after the bit of bronze dripped into my forge.
It is very likely that people have tried to forge something like mokume and damascus in the same session with poor results. Later, when inspecting a shut or busted weld, and seeing that coppery glint or greenish oxide, blamed the copper/brass/bronze/etc.
 
It wasn't just you Ed, I have seen this before on other forums and it always made me wonder. I can understand, as Page said, the copper/tin diffusion but will that only happen if the steel touches the spill or can it be just from the molten metal in the forge?
 
There's a lot of weird, old blacksmith/bladesmith urban legends. I've often heard/read that you shouldn't quench a carbon steel blade in a copper tank :rolleyes:

Then there's "let the razor blade rest a day before using it again"...
 
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Filler rods for gas welding mild steel are copper plated...I don't think they'd sell many if the resulting welds were bad. Granted it's not forge welding but still...
 
That concerns mechanical welding used in manufacturing and construction, but it was an interesting article.

Damascus welding is done at the high end of the solidus state and is both eutectic as well as fusion welding. The eutectic welding comes from things like the alloys causing the surfaces to fuse at a slightly lower point, and the fusion welding comes from the liquification of the surfaces occurring at a lower temperature due to the pressure applied by forging.

Elements in a mechanical welding joint that are not desirable, like sulfur, will cause lowered eutectic welding in the solid steel adjacent to the joint, as well as dissolved elements in the liquid joint at the weld site - and then when solidified, will become a weak compound, like iron sulfide.

Steel that is properly alloyed and matched for making damascus should not normally have these problems.

The worries in making damascus are incomplete welds caused by:
1) Oxides forming on the surfaces ( and preventing fusion).
2) Too low a temperature to allow complete fusion of the surfaces.
3) Improperly matched steel choices for the layers.
4) Too much pressure applied during hammering/pressing in the initial setting of the weld, causing the temperature to rise too high at the weld junction during fusion, and making the material liquefy and separate along the grain boundaries ( crumble).
5) Foreign material in the weld joint - borax glass, scale, dirt, etc.

In none of these situations can I see where a few PPM of gasified cupric ions could impede a weld if the other circumstances are met.
I agree that the "There must be copper in my forge" most likely comes from someones excuse why a bad weld failed to work. Addressing the real cause of the failed welds usually solves the problem.
 
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