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Phosphorus iron


Jack Hirsch

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Hey at this point I've done three wrought iron runs and I believe I'm ready for something more "exotic". And I hear that phosphorus iron while it has its downsides does have the positive properties I need for an upcoming project. Does anyone know how to add phosphorus to the smelt? I've heard bones or goose poop work but idk in what quantities or at what stage to add them. Does anyone have any knowledge on this subject?

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Phosphorus is a natural contamination in bog ore. So it's not added, it usually is a matter of getting rid of phosphorus by roasting bog ore prior to smelting. If you want to keep the phosphorus content, skip the roasting. 

Jeroen Zuiderwijk

Facebook page: https://www.facebook.com/barbarianmetalworking

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3 hours ago, Jan Ysselstein said:

I am not sure what you mean with a wrought iron run..how do you know your iron does not contain P?

 

I mean the bloomery I run shoots for iron not steel or when I'm lazy I use a modified forge of mine. I go to my local junior college and borrow their xrf spectrometer which confirms that it has no phosphorus.

12 minutes ago, Jeroen Zuiderwijk said:

Phosphorus is a natural contamination in bog ore. So it's not added, it usually is a matter of getting rid of phosphorus by roasting bog ore prior to smelting. If you want to keep the phosphorus content, skip the roasting. 

I've heard mixed evidence for this. Some anecdotal evidence (Such as the epic of Wayland the Smith) suggests it was somewhat intentionally added as a hardening agent before carburization was well known.  Also my ore contains no phosphorus so that's a big L.

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47 minutes ago, Jack Hirsch said:

I mean the bloomery I run shoots for iron not steel or when I'm lazy I use a modified forge of mine. I go to my local junior college and borrow their xrf spectrometer which confirms that it has no phosphorus.

I've heard mixed evidence for this. Some anecdotal evidence (Such as the epic of Wayland the Smith) suggests it was somewhat intentionally added as a hardening agent before carburization was well known.  Also my ore contains no phosphorus so that's a big L.

The local bog ore here usually has a lot of phosphorus in it. For local smelters it's a challenge to find a source that is low in phosphorus. IIRC, the high phosphorus is more purple in color. There is a lot of wrought here too that is high in phosphorus, usually used for things like wall anchors. So a lot of the wrought I find I can't use due to the high phosphorus content, which makes it impossible to forge.

Jeroen Zuiderwijk

Facebook page: https://www.facebook.com/barbarianmetalworking

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4 minutes ago, Jeroen Zuiderwijk said:

The local bog ore here usually has a lot of phosphorus in it. For local smelters it's a challenge to find a source that is low in phosphorus. IIRC, the high phosphorus is more purple in color. There is a lot of wrought here too that is high in phosphorus, usually used for things like wall anchors. So a lot of the wrought I find I can't use due to the high phosphorus content, which makes it impossible to forge.

That's unfortunate though from my limited metallurgical knowledge on the topic thankfully it's easier to remove phosphorus then to add it. I believe Man at Arms covered de-phosphoring in their episode on the sword from Eragon.  The only iron ore within 5 hours of me is just plain black sand, not too many impurities but no phosphorus. Which means it's literally good for everything except for high phosphorus iron. The reason I want to make phosphoric iron is for a historic iron demonstration on early viking period swords which tended to show signs of high phosphor content along the edges. Some experimental archeologists wonder when if instead of randomly relying on tainted ore they intentionally added phosphorus in some form (such as the goose droppings in the Wayland the smith story).

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Though my purpose here is to find out how they could have possibly if they intended to add it, how would they do so. My current theory would be as simple as mixing an organic high phosphorus material such as animal bones or as the old tale goes goose poop ( though I don't plan on force feeding goose a ground up sword, PETA would have a field day with that)

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This has been discussed long ago, and the general consensus is that you can't easily add phosphorus in the form of poop or bone, it just goes up the chimney, as it were.  It pretty much has to be in the ore to start with.

The European smiths knew which ores had phosphorus, and deliberately chose the irons from those ores for the edges.  Only took a few hundred years of trial and error.

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3 hours ago, Jack Hirsch said:

Though my purpose here is to find out how they could have possibly if they intended to add it, how would they do so. My current theory would be as simple as mixing an organic high phosphorus material such as animal bones or as the old tale goes goose poop ( though I don't plan on force feeding goose a ground up sword, PETA would have a field day with that)

It's more that it sounds similar to asking how would they have added slag to wrought to get the more rough wrought. It's the other way around. Such pure ores like the black sand are a rarity here and you're very fortunate to have access to that. Most iron ore here in Europe is bog ore (red hematite), ranging in quality from poor to terrible. It takes a major effort to turn it into something usable. Another source would have been rattling stones (don't know the English term, but called "klapperstenen" in dutch) which are a bit better (black hematite I think?). The highly priced more pure ores are a rarity, particularly magnetite ores. 

Jeroen Zuiderwijk

Facebook page: https://www.facebook.com/barbarianmetalworking

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Hi all! New to the forum but not the trade...also staggeringly ignorant with bloomery work, participated in a few runs as a helper and played with a tremendous amount of wrought in my early days ( lived in the NE US, place is lousy with it heh ) but made very little of my own....ok that long winded intro outta the way...why would one want a high phosphorus content? Id been under the impression it was a undesirable element? What properties does it impart? Also if trying to incorporate it would the blistering method work? Ie container with your phosphor ingredient then roasted in said container??

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Welcome aboard!

Phosphorus is indeed unwelcome in wrought iron in quantities of 0.3% or greater, because it makes it crumble at forging temperatures, and it makes cast iron too brittle to use.  What we are talking about here is late iron age swords and knives that were not quench-hardened.  Metallography has shown that these smiths of ca. 200 BC- 800 AD were making use of high-P iron's work-hardening properties to make tools and weapons with a hard edge and soft core to begin with, then used the high-P stuff (up to 0.5% P, after which it is totally unforgeable) as contrast in later pattern-welded blades, as it etches brighter than plain iron or steel.  

 

And I doubt blistering would work.  It works with carbon because it's such a small atom.  Phosphorus is only slightly larger but I don't know if it can  and it does not insinuate itself into iron crystals in the same way as carbon. Carbon is an interstitial element in the crystal lattice, Phosphorus is substitutional.  You could try, but what would be your P source?  Triple super phosphate might do...not trisodium phosphate, but the fertilizer stuff. It might just make a big mess, though.

 

I have about 50 lbs of nasty-looking high-P hematite ore full of quartz crystals I intend to smelt one of these days. Bright purple. 

Arsenic is also found in some early irons and has similar properties to Phosphorus.  

 

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For what it is worth, every modern steel spec I have seen that calls out the phos content limits it at 0.05% max, more often it is 0.03% or 0.04%.  Even less if you want to get into really specialty steels.  All of the alloys we make at the foundry I work at have P in the neighborhood of 0.02%, and I would be happier if it was lower, but I am limited by my melt stock, as we have no way to remove it.  

9 hours ago, Jack Hirsch said:

I go to my local junior college and borrow their xrf spectrometer which confirms that it has no phosphorus.

Just make sure their unit is indeed capable of reading appropriate levels of P.  Most hand held XRF units used on steels cannot (even if they give a reading, it isn't to be trusted).  Generally speaking, scrap yards won't have the right tool, but a college lab might.  And a bench-top unit is always better than hand held.  Light metals are a real PITA to detect accurately.  

 

For posterity:  P in any iron base alloy is bad.  The only reason we are not trying to talk Jack (OP) out of doing this is because he is trying to reproduce historically accurate materials and methods.  If he stated that his goal was to produce a superior material, we would tell him to not add P.  Jack - Good luck!  We like this kind of stuff here, so please keep us updated on your progress and results.  

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59 minutes ago, Jerrod Miller said:

For what it is worth, every modern steel spec I have seen that calls out the phos content limits it at 0.05% max, more often it is 0.03% or 0.04%.  Even less if you want to get into really specialty steels.  All of the alloys we make at the foundry I work at have P in the neighborhood of 0.02%, and I would be happier if it was lower, but I am limited by my melt stock, as we have no way to remove it.  

Just make sure their unit is indeed capable of reading appropriate levels of P.  Most hand held XRF units used on steels cannot (even if they give a reading, it isn't to be trusted).  Generally speaking, scrap yards won't have the right tool, but a college lab might.  And a bench-top unit is always better than hand held.  Light metals are a real PITA to detect accurately.  

 

For posterity:  P in any iron base alloy is bad.  The only reason we are not trying to talk Jack (OP) out of doing this is because he is trying to reproduce historically accurate materials and methods.  If he stated that his goal was to produce a superior material, we would tell him to not add P.  Jack - Good luck!  We like this kind of stuff here, so please keep us updated on your progress and results.  

Thank you very much Jerrod, that is indeed my purpose I'm well aware of the countless cold shuts that will occur but I'm a sucker for historic accuracy. Thanks for all the ideas, I'm off to the drawing board so to speak.

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41 minutes ago, Alan Longmire said:

Cold shuts aren't going to be your problem if you manage to add enough phosphorus.  It literally just crumbles when forged.  That's at and over about 0.5%.  

 Iirc to combat that phosphorus iron was mostly cold worked though I'm not sure that would work. That will be a bridge I'm willing to cross once I manage to get the iron

Edited by Jack Hirsch
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Well, you do have to forge it into basic shape first. ;) and if you want to weld it to a low-p core.  As long as the P content is 0.3% or less you won't notice TOO much, just treat it like really finicky wrought that is both cold and hot short.  Yellow heat only, short forging time.  Too hot and it crumbles, cooler than orange it crumbles.  Room-temperature forging, watch it like a hawk. It will harden up to a point, then it will crack.  There is no recovery short of remelting at that point.

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Thanks for all the info Alan. That does seem extremely finicky. But I low key expected that as a lot of old materials are. Reminds me of my one attempt at crucible steel aka as crumbly as feta cheese 

Edited by Jack Hirsch
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  • 3 months later...

Phosphorous also adds a contrasting element to the mix. It will visually contrast with the lower P iron.

 

Edit: oops Allen beat me to it

Edited by Daniel Cauble
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  • 3 months later...

Just a few quick notes, having browsed by here for the first time in a while. I see a lot of wrong statements in the above posts.
I have spent many years working to understand the role of P in bloom iron. It has many beneficial properties, and of course has some negative ones when you get over say 0.5%.... just like carbon has negative properties when it's over 2%. It's just a matter of appropriate use of the appropriate alloy, with P or C.
P does not make iron hot short, high P iron forges great. Alan, there must have been something else wrong with the iron you tried.
It can make the iron cold short if the P is high enough, but it can also make it work harden by cold hammering, enough so to make a serviceable blade. P actually can make the iron softer and more malleable at forging temperatures, and can make forge welding easier.
I'm just finishing up a paper on managing and exploiting phosphorus in bloom iron and I'll let y'all know when I publish it somehow.

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Thanks, Lee, it's always good to hear from you!  I suspect that particular fence picket is also high in sulfur, but I have no way of testing that.  The provenance is just questionable enough that I'm not sure where or when it was made, but I do believe it to be from northeast TN ore in the last half of the 1800s. 

I always look forward to reading your research, and as I still haven't smelted that nasty-looking high-P ore I have, that paper sounds like something I need to see.  I am always glad to learn, even when it means I've said things that were wrong.  :)  

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