Shear Steel; The Experiment Begins

[Will Wilcox]

In a previous thread, Alan Longmire gave some information regarding shear steel, an ancient process utilizing the carburization of wrought iron. This lit a serious fire under me, as ive always been incredibly interested in the study and (attempted) replication of archaic steel production, but do not have the knowledge to run a bloomery or the setup to do crucible steel. So i decided, im going to give it a go.

I do not expect to get high quality steel from this process right away, or maybe even my first dozen times. But knowledge is its own reward, and experimenting is fun! 

Im going to apologize in advance for bad photos, only had my phone on me at the time. 

So, here we go. 

I had some wrought iron laying around that i acquired about a year ago. I tried forging it and playing around with it back then but never did much with it. 

So today, I took what i had left and marked out roughly 1 inch sections for cutting:

Then cut them all apart:

Note the two on the far right were pieces i found from my previously mentioned toying around, already forged down pretty thin. 

 

Heres a shot of that oh so pretty wrought iron grain:

 

Now would be a good time to mention that back when i first obtained this piece, i brought a small section to the metallurgist where i work, hoping he could find time to analyze it. He was more than happy to help, excited actually. The next day he told me that it was almost pure iron, less than 0.005% carbon, close to no sulfur content, and practically nothing else. The inclusions were not huge like i expected, which leads me to the conclusion that this piece was refined at least once. He told me if i have any more samples to bring in, he would be happy to help.

Anyways, i took and forged about half of the pieces down to 0.1"-0.09", sadly did not have enough time to do them all before i had to leave for work. 

 

I was once again reminded of the fact that wrought iron is a totally different animal from modern steels. At the proper temperature, it forges like butter and moves easily. Too cold and it will just split right apart on you (guess how i figured that one out .) Nonetheless, i will get the rest forged down to similar thickness before proceeding. 

The plan is to cut the wider pieces down their length (hot dog, not hamburger) into about 1"x4"x0.09" pieces, and pack them into a pipe filled and tamped with charcoal powder, caps welded on both ends. Then proceed to heat the whole package to welding temp, and maintain for about 2 hours. If im lucky, the resulting blister steel will be high enough carbon for me to proceed. Probably wont turn out that way lol. 

The long term goal of this is to obtain enough decent steel to produce a blade of some kind. Im going to try to actually succeed before i conjure up a design. 

Thanks for looking! Updates will be added as this insanity progresses.

 

 

[Alan Longmire]

One very important thing that I may not have mentioned, since I am so used to working with wrought:  you have to cut it WITH the grain, not across.  Sorry I forgot, but that is absolutely key to getting good results with this.  Yet another way this stuff can mess with you...

[Will Wilcox]

And my own lack of experience with wrought rears its ugly face!  lol. Ill probably still try it just for giggles.

Why cant you go across the grain? Like i said, i have close to no experience with wrought iron. Seems to me like carburization is carburization no matter the orientation of the grain, no? Or is it a problem for reasons im overlooking? Couldnt i just cut the now forged pieces across the grain? 

[Christopher Price]

Cutting across won't hurt the carbon uptake at all, but will make re-welding it into Shear steel later that much harder.

[Will Wilcox]

I see. Well i suppose with the pieces i now have, i could cut them with the grain, into squares rather than strips, and either forge them into strips with the grain the correct way or just carburize them as squares. Apparently ive already made this harder than it needs to be, but no need to waste material! 

Edited April 16, 2018 by Will W.
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[Alan Longmire]

The problem with wrought grain direction is that if bent across the grain it will snap.  This only gets worse when made into steel.  This is why it took 40 years for cut nails to be accepted.  The nail-cutting machine was invented around 1790, but since the iron had to be fed into it cross-grained (nobody could roll a sheet of wrought large enough to cut strips with the grain at the time), the nails it made could not be clinched over.  They'd just snap off.  This meant nobody would buy them for making doors and other things that required a clinched nail. It took until around 1830 (in the US) until they could roll a large enough sheet of wrought to cut so the nail strip was cutting with the grain.  Then the nails could be clinched, and the hand wrought nail disappeared very quickly.

If you read old books on smithing you will see they greatly emphasize the importance of grain flow and direction for assorted operations in iron, particularly punching versus slitting and drifting holes.  Punching was considered poor form on parts the needed strength because it cut the grain, and slitting was only to be done with the grain or the bar would split when you tried to drift it.

Basically, wrought iron is a composite material, not a homogenous metal.  Think of the grain as the flexible equivalent of wood grain.  Make a hammer handle out of, say, ash.  If the grain runs the length of the handle, it's strong, flexible, and will do the job.  Now make the handle with the grain running shortways across the handle. What is going to happen the first time you use that hammer?

This directional weakness is greatly magnified when you carburise the iron because steel is always a bit more brittle than iron, especially when hardened.

Get the idea?

[Alan Longmire]

I just want to add, because this sometimes confuses people as well:  when talking about wrought iron grain, it is in no way similar to or even related to the steel grain size that we usually talk about around here.  Steel grain size is a phenomenon caused by the crystalline structure of the atomic lattice form that iron occurs in by nature.  It is non-directional (for this purpose, you can forge it into a directional structure, but it is not the same idea).  Wrought iron grain is the fibers of nearly pure iron that run the length of a bar in combination with strings of slag, or iron silicate glass.  This is what gives  rusty wrought that woodgrain look, and what makes wrought look frayed when you do the break test. 

To make it even more fun, Wrought iron has both of these grain types, the macro-structural and the crystalline.  

[Jerrod Miller]

This all makes me want someone (certainly not me) to start some experiments with alternating orientations of wrought (like plywood).  And since Will here already has the samples...

[jake cleland]

6 minutes ago, Jerrod Miller said:

This all makes me want someone (certainly not me) to start some experiments with alternating orientations of wrought (like plywood).  And since Will here already has the samples...

pretty sure that's one of the standard hada patterns in Japanese swords... itame maybe?

 

[Jerrod Miller]

I was thinking really low layer count though, more like actual plywood, so maybe up to 10 layers max?  And then some bend tests.  Tensile tests would be neat, but who is going to spring for that?!

[Alan Longmire]

I actually have some of that, it's the Byers process for making water tanks and boilers.  I have a chunk of the water tower tank from the old Ohio state penitentiary made that way.  Really rusty and I've never used it, but it exists! Only two layers, grain direction crossing at 90 degrees.  Apparently allows much greater pressure without bursting along the grain of the wrought, exactly like plywood.  Nothing new under the sun, eh?

[Emiliano Carrillo]

When reading I was going to comment exactly what the others above have said! When I use my home made steel I generally don't fold 100% in the same direction. The first multibar sword I did with home made steel had shears all over it because of the iron being refined only in the lengthwise direction. Now I generally fold three times in one direction, switch 90 degrees and fold three more times, and repeat that process as many times as I need to get good clean material for my application. 

 

I think you are fine doing it with the orientation you chose, but be prepared to fold in the opposite direction quickly or even orient square pieces 90 degrees to each other to save yourself some work and heartache in the future. Jake is also right, it's a staple of Japanese techniques to alternate the direction of the folding as it really does make the material stronger. I haven't had occasion to test my home made steel blades in that sort of scenario but I can tell you the welding and folding gets much easier when you are changing directions 

[Vern Wimmer]

22 minutes ago, Alan Longmire said:

I actually have some of that, it's the Byers process for making water tanks and boilers.  I have a chunk of the water tower tank from the old Ohio state penitentiary made that way.  Really rusty and I've never used it, but it exists! Only two layers, grain direction crossing at 90 degrees.  Apparently allows much greater pressure without bursting along the grain of the wrought, exactly like plywood.  Nothing new under the sun, eh?

I had heard that the concept of plywood dates back to he ancient Egyptians ?? 

[Will Wilcox]

Thanks for the replies everyone. Im going to forge what i have left the same as the others, and try what was recommended, stacking with alternating grain orientation, and cutting accordingly.

Now, quick question. Would it be better to carburize, then proceed with the welding, or weld all the pieces now to refine it, cut it back up, then carburize and reweld? I would assume welding now and refining the iron before (hopefully) turning it into steel will result in a better product, yes?

3 hours ago, Jerrod Miller said:

This all makes me want someone (certainly not me) to start some experiments with alternating orientations of wrought (like plywood).  And since Will here already has the samples...

Assuming i can actually succeed in doing this, Jerrod, i would be happy to send you some samples if you wish to test them. I do not have a setup to test to failure with any sort of accuracy or measurability. 

[Will Wilcox]

2 hours ago, Vern Wimmer said:

I had heard that the concept of plywood dates back to he ancient Egyptians ?? 

http://www.reshafim.org.il/ad/egypt/timelines/topics/wood.htm

About halfway down in this article, under the "craftsmen and their techniques" section, they talk about egyptian plywood.

[Alan Longmire]

I'd weld before carburizing.  Less risk of burning and lost effort that way.

I also found a nifty reference to the tensile strength of wrought being pulled with the fiber versus across the fiber.  With the fiber, it can take 18% stretching deformation before failure.  Across the fiber, 4%.  

[Will Wilcox]

Roger that, Alan, thank you. I figured it would be stronger with the grain than against, but thats substantial. Interesting stuff. 

[Jerrod Miller]

1 hour ago, Will W. said:

Assuming i can actually succeed in doing this, Jerrod, i would be happy to send you some samples if you wish to test them. I do not have a setup to test to failure with any sort of accuracy or measurability. 

Sadly, I don't have the equipment for a scientific test either.  Maybe I could rig a bend test with my torque wrench, but nothing better than that.  I know where to have the tests done, but that costs a bit of money.  

[Will Wilcox]

So this is where im at. Pieces of wrought cut with the grain into squares and stacked alternating grain directions. Hoping to get it all cleaned and welded up, and perhaps folded again, before drawing out into thin bars before carburizing. With the leftover wrought, i may be able to get 3 stacks like this in total. Each stack roughly 2"Wx2"Lx1"T. This leaves me with ~4 cubic inches/stack, hoping to be around 3 cubic inches per stack after welding, before carburizing. Will get to welding these stacks this weekend.

Wondering how i should go about holding these together prior to the first forge weld. Could arc weld one or all of the corners, but im not sure how wrought takes to being welded with steel wire. Ill probably try to wire them together, which ive never done before, so it should be interesting! 

[Will Wilcox]

So my poor planning meant that i only had enough charcoal to weld up one of those billets. 

I took and arc welded one side just to hold everything together. Meant to get a picture of it. 

Forge welding went great! Ive never welded wrought iron before, but ive read that you need to get it much hotter than the high carbon steels most of us are accustomed to using. Equipped with that knowledge, i got the billet to white heat, gave it some light blows to set the weld and went to town. 

 

This was it after about 5 heats. 

I took and kept forging at high temps (stopping when it reached orange, about what the picture shows) and kept it fluxed constantly, to help with welding and try to mitigate loss to scale. Forging ceased when i ran out of fuel. 

 

This is it compared to the other billet, about what the forged billet started as.

Just out of curiousity, i did a very quick, down and dirty grind to 320 grit, and etched in hydrochloric.

Much to my suprise, there was a good deal of patterning for just 5 layers of iron. The iron also acted very different from steel in the acid, there was a stream of bubbles running off of it at a very constant rate. Only etched for maybe 30 seconds. Interesting. 

The plan is to weld up the second billet the same as the first, then cut them both apart and re weld into thin strips rather than squares. I think im also going to make up a third billet with the wrought i have left over that i have not done any forging on. After that comes the carburizing! 

Edit: i also spark tested to see if the iron carburized at all during the welding. It appears it did not, looks very low carbon still. 

Edited April 22, 2018 by Will W.
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[Alan Longmire]

Looking good!  As for the layers, if you were to etch a piece of the original stock it would look like that too.  Remember wrought iron is a composite material made of thousands of strands of iron and slag.  The Byers manual states that well-refined wrought contains around 250,000 strands of iron per square inch in cross section.

[Will Wilcox]

Meant to respond to this, Alan. Oops. 

Thats interesting, regarding etching an original piece. Might have to try that just for the giggles. As always, i appreciate the knowledge. Wrought iron is an interesting beast. 

Hoping to get the other two billets welded up tomorrow, maybe ground and prepped for re-welding. And if im VERY lucky (unlikely) i can get them all re welded into thin strips on Sunday. Hopefully carburize next week. 

Now, i was reading into this, and apparently the way the iron was carburized in the days of yore was in clay pipes. I would imagine this was because iron was precious and making a pipe out of it would be wasteful and unnecessary, but i believe i will try to replicate this 1. because i would like to try to do it as accurately to the ancient techniques as possible and 2. wouldnt doing it in a mild steel pipe also carburize the pipe? Not really what were going for here. 

 

[Vern Wimmer]

Kinda interested in this as it sunds like "case hardening" gun parts.

Conflabulating something from another thread I am wondering if you could "up carbon" a RR spike if you drew the blade out a bit first.

[Alan Longmire]

Yes, it will also carburize the inside of the pipe, they did use clay because iron would have been so much more expensive, and it is indeed a longer variant of how they still do case hardening.  Case hardening is meant to be a thin skin of hard on an otherwise soft part.  If you were to leave the part at heat for hours instead of minutes, you'd get a through-hardened part via the magic of carbon migration.

Both processes also recommend leather and bone charcoal as better than wood.  I have heard all sorts of explanations, ranging from phosphorus and potassium in bone promoting faster carburization to the black magic of using animal parts to the (more likely) it was a good way to use the byproducts of butchering.  Commercial carburizing compounds contain barium, and I have no idea why.  Plain old wood charcoal is fine.  Carbon is carbon, but I doubt diamonds make a good carburizing compound...

[dragoncutlery]

double sheard diamond steel has a nice ring to it