Refining Bloomery Iron into Hearth Steel with Hurstwic

[Emiliano Carrillo]

Hey everyone! 

 

Recently I've had the opportunity to do some work with Hurswtic near Worcester MA. They had an interest in iron making to explore Viking Age arms in a slightly more in depth way, and as soon as I found out I was very keen to be a part of it. We did a smelt recently that made 16lbs of iron which I cut and forged into small biscuits that we were then able to remelt. I have learned a huge amount from friends both on and off this forum who have stoked my interest in learning and experimenting with this process. Without that I would be more lost than I am now!  

 

Here is a link to some of the write up on Viking Age iron done by Hurstwic:

http://www.hurstwic.org/history/articles/manufacturing/text/bog_iron.htm

 

And the video that Bill shot and edited together of a presentation I did with them to teach how to create hearth steel from iron. Hope you guys enjoy!

 

 

 

[Charles dP]

Very interesting. Thanks for posting Emiliano.

[Alan Longmire]

Very cool!  Thanks for posting indeed!

[Joshua States]

This was brilliant. I would assume that this could be done using commercially available wrought iron as well with similar results?

[Alan Longmire]

Indeed it can.  Or with bottle caps, nails, bean cans, or any other mild scrap.  I think Emiliano even did it to a leaf spring at Ashokan?  Somebody did, anyway, and it was Emiliano's hearth...

[Joshua States]

6 hours ago, Alan Longmire said:

Indeed it can.  Or with bottle caps, nails, bean cans, or any other mild scrap.  I think Emiliano even did it to a leaf spring at Ashokan?  Somebody did, anyway, and it was Emiliano's hearth...

However, being that this is the refinement melt that adds carbon, you wouldn't want to start with a mid-high carbon material would you? Unless you were trying to make cast for a wootz melt. It would seem to me that you would want to use as low carbon as you can get. Maybe there's a way to adjust the tuyere blast to oxidize more on the higher carbon material?

[Alan Longmire]

Yeah, you want to start with low carbon if possible, and ideally with a little slag to protect the puck from the fire once it's melted.  That's why wrought or bloom is best for this process.  If you're using something other than bloom for this, I'd call the process oroshigane a'la Louis Mills, or short-stack grappage, depending on whether you prefer Japanese terms or French terms.   

[Joshua States]

9 hours ago, Alan Longmire said:

short-stack grappag

Do antibiotics work for that? 

[Emiliano Carrillo]

On 11/25/2018 at 7:48 AM, Charles du Preez said:

Very interesting. Thanks for posting Emiliano.

Cheers Charles! I'm glad you enjoyed  

On 11/25/2018 at 3:34 PM, Alan Longmire said:

Very cool!  Thanks for posting indeed!

Thanks Alan! 

On 11/26/2018 at 12:48 PM, Joshua States said:

This was brilliant. I would assume that this could be done using commercially available wrought iron as well with similar results?

Yes! My first experiments have been with wrought iron! It takes a hotter fire to melt properly, but with a bit of careful modulation of the fire you can melt and carburize anything, or decor for that matter! I've taken pure iron and made it into very high carbon steel and taken cast iron and turned it into really nice steel as well! This little furnace is the workhorse of furnaces in my opinion!  

On 11/26/2018 at 2:15 PM, Alan Longmire said:

Indeed it can.  Or with bottle caps, nails, bean cans, or any other mild scrap.  I think Emiliano even did it to a leaf spring at Ashokan?  Somebody did, anyway, and it was Emiliano's hearth...

We did our best attempt at it  at that point everyone had enjoyed a lot of libations and even some of the moonshine you may or may not have brought! But that sucker turned into a four foot bar of hearth steel without any cracks so I think it was a success!

[Zeb Camper]

Just tried this earlier with 3.5lbs of iron wire. I thought I heard you say 6 pounds in 5 oz. Charges  I was worried I wouldn't have enough charcoal for 3.5 lbs, let alone 6! 

I got what I believe is mild steel equivalent. My pipe was angled downward more and further down closer to the middle of the fire, so I think my air was blowing on it too much. 

Welding all this together should be interesting! 

There's a thought I've been having... I think I'd like to make high phosphorus iron to contrast with low phosphorus.I've read that phosphorus can be extracted from bone ash with heat. So, if I got some KFC and burnt the bones with each charge, might it add phosphorus?  

Thanks for the information and inspiration man! 

 

[Ryan Hobbs]

I'm really interested in trying one of these furnaces out! I have the resources for a smelt, but not enough space or time. Seems a lot more feasible for me right now. 

[Alan Longmire]

On 1/13/2019 at 4:29 PM, Zeb Camper said:

There's a thought I've been having... I think I'd like to make high phosphorus iron to contrast with low phosphorus.I've read that phosphorus can be extracted from bone ash with heat. So, if I got some KFC and burnt the bones with each charge, might it add phosphorus?  

I had that same thought back around 2006 or so.  The gurus of smelting at the time didn't think so, but nobody ever tried it.  For the record, on your path to the Fiery Beard you will read some rather obscure Norse sagas, including one in which the protagonist was told to feed iron filings to his geese and smelt the poop.  Modern theory is that would add Phosphorus to the now-oxidized iron, more or less making a high-P bog ore analogue with additional organic contributions from the other (ahem) solids.  

Got any geese?

 

[Zeb Camper]

Am I really considering buying some geese right now?... Yeah! 

I'll try the bones first 

 

[Emiliano Carrillo]

On 1/13/2019 at 4:29 PM, Zeb Camper said:

Just tried this earlier with 3.5lbs of iron wire. I thought I heard you say 6 pounds in 5 oz. Charges  I was worried I wouldn't have enough charcoal for 3.5 lbs, let alone 6! 

I got what I believe is mild steel equivalent. My pipe was angled downward more and further down closer to the middle of the fire, so I think my air was blowing on it too much. 

Welding all this together should be interesting! 

There's a thought I've been having... I think I'd like to make high phosphorus iron to contrast with low phosphorus.I've read that phosphorus can be extracted from bone ash with heat. So, if I got some KFC and burnt the bones with each charge, might it add phosphorus?  

Thanks for the information and inspiration man! 

 

Hey I just saw this, sorry for the late reply! I've found that tuyere angle is less important as long as the blast isn't directly on the puck, but when you have more material, the air blast will have to be higher to account for it! I usually do 2 lbs or 2.5 because I've found that is what I get the most consistency with, I very rarely end up with larger runs that are all homogenous as far as carbon content goes. 

 

If I can make a few observations from what I see right here that might help make your results better, I would suggest chopping the charcoal smaller, you want pieces around 1-1.5 inch in size for even heat, and I would make the charge with the iron wire as close to 2 lbs as possible. Once the fire is really going and you can tell it is at beyond a welding heat just below the tuyere, you can begin the charging, but for such small stuff like the wire you will probably want about 3 minutes between each run, also I like how you're binding the wire together like that, that is a very smart move and likely why the puck came out as together as it did! What are the sparks of that puck like? Is there any really high carbon in there? From what I see it looks like the stuff is fairly low to medium carbon. I'll attach a photo of a piece I made recently that broke off the larger puck, it's nearly cast iron. 

 

As far as phosphorous goes, in my experiments I have noticed that phosphorous does not really melt out of steel in this process. I have found it inhibits carbon uptake and increases decarb, leaving you with nearly iron after just a few folds. I have been making mostly Japanese style pieces with this steel so I am folding a minimum of 11 times and as much as 18 recently, so if the materials isn't top notch then I end up with very low carbon at the end. If you buy nails from the Old Globe elevator for instance, or use high p iron to begin with, you can remelt and add a small amount of carbon, but in my experience it really wasn't worth the effort to make hearth steel from phosphoric iron. 

 

I hope that helps some! If there's anything I didn't explain well or doesn't make sense I'll do my best to help!

[Zeb Camper]

@Emiliano Carrillo thank you sir!

Ive been meaning to message you or JJ about this, but just had a lot of other stuff going on both on the smithing side and real life. 

Yeah, I think it's mild steel equivalent. Some bursts, but not very fuzzy looking right at the wheel. I would say it came out just the same as it went in (carbon wise). 

And, I guess my next question is how do you keep contrast in P-weld without alloys? Just carbon? What about migration? Won't it Look muddy? I can't beat the carbon migration anymore because my home built power hammer needs a new motor and just can't afford it. I'll be by myself or with a striker (if I'm lucky). 

Thanks a ton man! 

Edited February 5, 2019 by Zeb Camper

[Emiliano Carrillo]

1 hour ago, Zeb Camper said:

@Emiliano Carrillo thank you sir!

Ive been meaning to message you or JJ about this, but just had a lot of other stuff going on both on the smithing side and real life. 

Yeah, I think it's mild steel equivalent. Some bursts, but not very fuzzy looking right at the wheel. I would say it came out just the same as it went in (carbon wise). 

And, I guess my next question is how do you keep contrast in P-weld without alloys? Just carbon? What about migration? Won't it Look muddy? I can't beat the carbon migration anymore because my home built power hammer needs a new motor and just can't afford it. I'll be by myself or with a striker (if I'm lucky). 

Thanks a ton man! 

Looks like I forgot the photo... This is really high carbon oroshigane that made great hamon on a piece, I ended up with somewhere around 1% carbon I believe, but I haven't checked properly yet, that is based on the hardness as quenched. 

 

As far as contrast goes I've done a few pieces with refined steel and then higher P iron that was from my earlier attempts at hearth refining. I find that if the source of the iron is different the two pucks will look sufficiently different with an etch. I have also twisted bars that are the same material and seen contrast. I'll attach some of those here as well. 

 

This first one was low refined steel and iron folded together, the sources were similar iron, the only real difference was the iron was refined more and is the silvery lines you see. 

 

This one was all iron, but it was layered up from pieces I had refined separately and drawn and twisted, hence the faint pattern but the areas where you can see it are bright. 

 

This one is very subtle, this was just iron I had folded then twisted, for a very subdued pattern. 

 

And this one is a lot more recent, but was an experiment with iron that had three bands in it, that I folded into three pieces, to end up with basically seven layers for the twists. This one is certainly a little more out there in terms of the twists we are used to seeing in modern steel. 

[Zeb Camper]

Too freakin' cool! Thanks again man! I'll try this again real soon. 

[Jan Ysselstein]

I found this thread a few months ago and tried it with some low carbon bloomers iron. The yield was about 1kg a solid little bloom but quite a mix of carbon content ....it may average at about .8% C. I was looking for a higher carbon content and a more homogeneous ingot ( so I can estimate carbon content ). Trying to create a solid ingot of iron which I can use in a crucible ( after breaking it up with a hammer  ) and adjusting the final carbon content with some bloomers cast iron. I will try it again using a mix of bloomers iron pieces having different C concentrations. Hoping to get a fully liquid=solid ingot. I do not know how to get a photo on this post from the devise I am using and wii add it later. Emiliano thanks for the video ...very clear.

 

 

 

Edited November 7, 2020 by Jan Ysselstein

[Bill Schmalhofer]

Jan, you popped this one back up to the top just at the right time. I am also looking into doing this soon. We've had a discussion going on about Aristotle furnaces in the Beginner Place (Forge welding dirty gunky machine shavings  By J.Leon_Szesny, October 27).

 

Emiliano, thanks so much for this video and lesson. This is going to be a big help.

[Jan Ysselstein]

I am about to do a series of these, my furnace is like the Aristotle furnace without that extra primary little chamber. I do not enter at an angle but will be adjusting the bottom as needed. There is a lot of material around I hope to process ..I will post as I go along. I have photos of the little bloom I just made but for some reason they will not drag into the post. I think I just figured it out.

 

 

Edited November 15, 2020 by Jan Ysselstein

[Emiliano Carrillo]

Hey Jan! 

 

Beautiful little puck there  

It looks a lot like the one in my post above, I think you are on the cusp of cast iron! The puck in the above photo made some very nice hamon in japanese style after 16 folds, I think you could make quite nice steel from your piece after some refining! 

 

The biggest thing I have learned in this is to make sure whatever you're charging into the furnace has as little phosphorous as possible, it just doesn't allow carbon to absorb well and affects weldability. You can use this method to remelt and clean phosphor rich material but it won't be great for edges, better for pattern welding! 

 

Here is a photo of a more recent piece, hearth steel for the edge and bloom for the wolf tooth and spine twists. 

 

 

[Jan Ysselstein]

Emiliano,

   Beautiful blade , some fancy welding as well. I thought it was a hamon at first. Took down that offer of the little bloom , as it seemed awkward at its new location but it is still there. The rick assembly is looking better as I have just ruined a furnace due to a leak I should have plugged.

 

[Emiliano Carrillo]

Thanks! Yes it does look a lot like hamon! The edge bar hardened really interestingly, almost all the way through which means the steels layers are a little more hidden in the polish. I hope once it is finished you will be able to see the steel much better!