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I Forge Iron

Found scrap turned out to be impossible to forge


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Hi.  I had an interesting problem the other day.  I was working on an open forge day, and I experienced some serious difficulties with a piece of found steel that I was working on.  It was one of those concrete form stakes with the holes for wires in it.  Normally, these are mild steel and are workable at reasonable temperatures.  I found two of them in the street, and they ended up making some useful things.  The third one I used was just terrible.  After a few heats, the metal would crack off while hammering.  It looked crystallized, like with grain growth problems or burnt metal.  It couldn't have been either, because the metal was cracking at high red.  I was pulling the steel out of the forge at a high drippy yellow with a tiny bit of sparking only at the tip.  It's what I call a "Frank Turley" heat; he says get the metal hot and "git over it!".  This heat has been ideal for forging mild steel, and I'm not afraid of it.  It is iffy for medium carbon steel, and of course awful for high carbon steel.  The metal would only survive about two heats before cracking, or more like crumbling.  The break looked almost like forging cast iron.  It was very embarrassing in a group setting, so I finally went to the grinder and looked at the sparks.  It looked exactly like mild steel.  No way it was even as high as an HC railroad spike.  A file and hacksaw cut like it was mild steel.  Very strange!

I took the piece home and wondered how it would do on the lathe.  It cut well.  HSS with no chip breaker at 100 ft per minute gave good C's and 9's.  Not medium carbon, since that would give strings without a chip breaker.  The finish was OK, but not super smooth, so it wasn't leaded.  Definitely not cast iron or anything like it, since that doesn't really draw a chip, more like black powder.  Strange stuff.  I suppose it is useful in the machine shop even if it is not forgeable.  I wonder if it is weldable...

A couple of lessons were learned.  First, scrap metal can be a good find, but it could also be unpredictable.  Second, just because one item works great doesn't mean that all similar items are made out exactly the same stuff.  Would anybody know what impurity would cause the problems I experienced?  The metal looked rough on the outside, but when the outside skin was turned off, it looked fine.  I've pulled junk out of creeks that have had half their diameter pitted away, and they made great artistic forgings being worked at all reasonable temperatures.

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I thought I knew everything in the first half of your post, but when you ckucked it in your lathe, my theory went out the window. 

I will lay odds that there are numerous steels that forge picky but machine well - but a form stake? :-/

Robert Taylor

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I suspect that form stakes may be made in a continuous casting/rolling process like rebar which means that the content and ally will change over the length of the bar depending on what scrap was being fed into the input end.  I have noticed that even cold rolled steel stock can vary over the length of a bar in recent years.

So, as you say, never count on consistency, even when you would expect it.  I think that most HC commercially purchased steel, e.g. 1085, will probably be pretty consistent but scrap and mild steel, not so much.  Rebar seems particularly inconsistent.

Also, no embarrassment about being negatively surprised by a piece of steel. It has happened to all of us. 

"By hammer and hand all arts do stand."

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Sulfur makes steel hot short and phosphorous makes it cold short.  "Bad" runs of steel were often used for items that it didn't matter so much; of course this was much more common back in the bad old days as steel can be tested in the melt fairly easily nowadays and ameliorated before the pour.

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Thanks, Thomas.  I am very suspicious of sulfur.  That would explain the somewhat shorter chips, too.

When the end falls off of the piece of metal you are working on, you look around quickly to see if any of the other blacksmiths are watching.  This most reminded me of forging M2 too hot.  But that was more like cottage cheese.  There was some kind of crumbly look, but not quite the same.


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