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Phosphorus makes it cold short! (And sulfur makes it hot short!)

Wish you were down here I still have about a ton of wrought iron plate in 3/16" and 5/16" thickness from the old Ohio Penitentiary...Of course I think it's Byers bi directional rolled plate and so a lot like what a batter mill would produce...

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Hi Thomas,

I would like that very much as well, maybe I can convince you to send me some. ;)  

The other test I wanted to do was in several parts. I came across an article about forging high phosphorus iron and it gave me several ideas. The paper is here:


Not only does it show that many artifacts from ancient on up to the 14th and 15th centuries were made from high phosphorus iron. They come to the conclusion that it's the formation of two iron microstructures that causes the cracking issues, namely ferrite + austenite. The two states do not react well together and create two different mechanical behaviours that lead to forging difficulties. But if you forge it at below 900 C then austenite can't form and you don't get the issue. According to the article this would be around an orange temp (about 1350 F to 1450 F). 

So I tried this and it works pretty well, I don't know the exact percentage of phosphorus in the wrought iron I have but it appeared to work out. I did get a few cracks on the very edge of the pieces I was forging, but I don't know if it was the temp or I forged it out of temp. I was able to bring the metal back up to forging temp and weld the cracks back together.


The next test is to see how well the metal can be cold forged. This is essential for making armour as you can't use heat on very small parts or for fine detail work, some amount of cold work is unavoidable. I wanted to do a simple test that could be easily repeated to see how the metal will behave under different circumstances. So what I did was to put a corner of the metal in a vice and then I slowly bent the metal 90 degrees by hand. As a base test I did this on a scrap of mild steel 16 gauge plate I had laying around. And then I did the same with the wrought after I had finished several operations on it. Here is the results:

The first is the mild steel test

Second is one of the wrought plates that had been air cooled

Third is one of the plates after it had been quenched in cold water

Fourth is one of the plates after it had been annealed in the forge ashes

Fifth is another plate that I also annealed in the ashes

The last is a side view of the tests. The one on top is the last annealed test with one of the other tests under it.

The last test is very encouraging, it looks almost the same as the mild steel test. This gives me hope that I can cold work the metal and make some armour out of it, which is the next test. Why the other annealed test didn't work as well, I'm thinking that I didn't get the plate hot enough before I buried it in the ashes. This is just something that I need to get more experience with. 

I'm thinking of making a replica of Wade Allen's 14th century gauntlet finger plates here:

I suspect that, because of the phosphorus, the metal will work harden very quickly, so I'm going to need to plan the hammering steps carefully. I also made some thicker plates that will be good for making buckles as another test. :)








Well that didn't work very well, is there a way to order the images, or at least insert them in the text?

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Note the delamination on photo 6.  I had a lot of problems with that as the demolition company kept mangling the metal and then thinking they should be paid more!  I originally asked to buy about 10K pounds and after they mangled it I got substantially less---I ended up cutting along the folds to leave the flat "good" pieces as large as possible but a cutting torch was messy as the top layer would melt and then blow back at you till the lower layer would heat and you could cut.

BTW Ric Furrer really likes this stuff for making blister steel....

Now the issue is getting it cut and shipped as I have little time in my shop these days---why I was more likely to share it if *you* did the work...Using real charcoal you can work quite small but a lot of the finish work was done cold... 

I assume you have read "The Knight and the Blast Furnace"  Alan Williams; the top book on the metallurgy of armour with *modern* research!

Also Radomir Pleiner's "The Celtic Sword" mentions using high phosphorus wrought for the edges of celtic blades as well as high C wrought. As high Phosphorus  was a hardening agent too.  (again a lot on the metallurgy of them)

And to really make you put out your forge fire with your tears: 

Heroic Armor of the Italian Renaissance: Filippo Negroli and his Contemporaries ,   Pyhrr, Stuart W., and José-A. Godoy, with essays and a compilation of documents by Silvio Leydi (1998)

Exquisite chasing and repousse applied to armour and it was down in medium carbon steel!  (give you a hint, one helm was made for the Holy Roman Emperor and was signed on the brow in gold so he could brag that he had a Negroli!)


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Thanks Thomas, no problem on the wrought, I completely understand. :)  I wish I could afford "The Knight and the Blast Furnace", but I do have the Negroli book and to think that all of it was done using wrought iron/steel.  I will have to look into getting "The Celtic Sword" for sure.  

I have noticed additional delaminations on the other plates I did.  I suspect that I'm not getting the rod hot enough all the way through when I first start forging it and it's creating a separation right in the middle of the plate.  This has been a definite learning experience for me.  

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As wrought is generally forged from several pieces stacked and welded together that may well be an original weld failing when bent cold.

My wife bought me the Knight and the Blast Furnace for Christmas one year---used and still more expensive than several triphammer's I've owned...ILL is your friend!

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