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I Forge Iron

Will copper penny ruin a forge weld?

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Please be more specific.

Is that a REAL COPPER copper penny or the alloy mix they use to stamp out today's "copper clad" penny?

Is that coin tossed on to the forge table, onto the fire, melted in the fire and now a part of the clinker, or smeared onto the parts being welded?

There are too many variables. Please redefine your question so we can provide a specific answer.

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Let's say any of those that occur in a solid fuel forge so not on the table. I think the steel pennies I have are worth too much. I have read it too as copper pennies in the fire and the smith cannot weld until the fire is cleaned out. The books I have read this in are before plated pennies, so solid copper.

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Since it is an *old* saying or myth we can conclude:

- penny was an old solid copper penny, as copper clad pennies did not exist at that time
- it was thrown on top of the center of the coal fire, centered over the firepot
- heat started melting it, so the penny starts its travels downwards into the fire
- as penny travels gradually downwards into the fire, it continues to melt, joining with the coal and traveling with the coal and burnt materials as the coal and burnt materials moves downwards over time, depending on how fast the coal is expended
- as penny melts it both gives off vapors, and interacts with contents of fire to possible give off other vapors
- copper continues its travel downwards and iron is exposed to varying amounts of copper and copper influenced vapors
- copper continues its travels and eventually reached the bottom to become part of the clinker, still continuing to possibly give off vapor

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And old copper pennies are actually not 100% copper.

Copper on hot steel makes for problems along grain boundries; but I have seen welds done in a forge with copper added to the fire---as well as sulfur, flyash (dirty fire), etc as a demonstration that it CAN be done with a fire pretty much as bad as you could get.

Sure easier to do good welds in a clean fire though!

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In a farrier contest, I once beat one of the best on a forge welded barshoe when he missed his weld -- he blamed the fact that he'd been copper brazing in the forge (gas forge) Don't know if it was a fact, but this guy believes it since he's one to look for solutions, not excuses.

Incidentally 1981 and before pennies are copper. In a pinch, I've used them to braze with.

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This is from Metallurgical Consultants:

Copper in significant amounts is detrimental to hot-working steels. Copper negatively affects forge welding, but does not seriously affect arc or oxyacetylene welding. Copper can be detrimental to surface quality. Copper is beneficial to atmospheric corrosion resistance when present in amounts exceeding 0.20%. Weathering steels are sold having greater than 0.20% Copper.

It looks like there is a different effect between forge work and arc welding.

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I remember that, Rich. I may be able to find it.

Having copper actually alloyed with the steel is one thing; having once melted a tiny little bit of copper in the forge is something else entirely. Of course if you stick a penny in a joint you're trying to weld, it's going to be impossible. (You'll be in good shape to braze it, though!) But the idea that just because you once melted a penny in the forge, it somehow permanently contaminates every piece of metal you stick in the forge just doesn't make sense to me. Even if the penny and the iron are in the forge at the same time, as long as you're not rubbing molten copper or dirty clinker into the joint, I have trouble seeing how it can cause a problem. I'm convinced this is an old wive's tale and nothing more.

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It might be that if any copper was still in the coals/coke it would transfer to the work being heated and could cause problems. After the ash has been removed and fresh coal added I would not expect to see any problems. (ah, I see Glenn referenced a post on this)

So far it sounds like part myth and part fact. Fresh copper pennies would cause problems in welding due impurities and copper oxides. Once the forge is cleaned there would be no further problems. So, did anyone go out and try it yet???

Of course I once accidentally moved the magnet on my forge and that changed the polarity of my fire. Couldn't get a good weld for week until I moved it back.:D

Edited by Larzz
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