Appearance of Shear Steel vs Hearth/Bloom Steel?

[Aiden CC]

Lately I have been experimenting a lot with hearth steel, and have found it very rewarding but also rather challenging to do with my setup. I don't have a press and find myself losing a lot of carbon in the initial consolidation and first few folds. My main goal with home made steel right now is to make Japanese style blades, but I also hope to do some pattern welding in the future once I have enough material. On a recent project, I was able to revive a decarburized blade by case-carburizing it, which made me realize that maybe I have been going about this wrong and should be looking at blister/shear steel instead of hearth material. That brings me to my question: will a high layer count shear steel be able to get the look I'm after and mimic material made in a hearth or bloomery?

 

I would summarize my overall material goals as:

- Shallow hardening for a clear hamon/ the option for good sori

- Fine and relatively homogenous layering for subtle hada 

- Relatively "clean" material with a low amount of inclusions, porosity, etc

 

Does anyone know if shear steel will allow me to do this? It seems like starting out with blister steel carbon gradients could give higher contrast than I want, maybe alleviated somewhat by carburizing thin strips and lots of folding. Also, without a true melt, the slag from the wrought iron (which I would want to use to not have any Mn, Cr, etc) would likely be present in a greater amount than in the hearth material I have been making. I have only really seen smith-made shear steel used for European style blades and etched deeply to show the layers. It works well in that role, but I'm not as sure how it will work  for what I'm trying to do. I will do some experiments myself, but if anyone has experience with higher layer count shear steel, especially with a hamon, or any thoughts about how it might look compared to hearth/bloom material, I would be very glad to heat about it! 

[Alan Longmire]

Ric Furrer and Kevin Cashen did a fair bit with shear steel a while back, but you probably knew that.  Given your desired properties, everything will hinge on the quality of the wrought combined with how you manipulate it.  If your feedstock is something like recent anchor chain, that stuff is usually very clean indeed.  If you use wagon tire as feedstock, it'll be far less refined in general.  

 

If you start with very clean, highly refined wrought, and process it into shear steel using many more folds than is typical for Western shear, it ought to produce hada not unlike highly refined tamahagane, but perhaps with a more linear/lamellar grain.  I'm also thinking about what Michael Bell does with wire rope to get a pseudo-tamahagane hada.  Because of the way cable is made, the decarb at the welds ends up being more similar to what you'd see with bloom steel as opposed to shear steel.  

 

The thing with wrought is the linear/lamellar grain, especially with later rolled bar as opposed to hammered bar, isn't going to look like tamahagane unless you manipulate it in such a way as to get the shorter grains.  Hmmm...  

 

One good thing is that with wrought you don't usually have to worry about Mn.  Phosphorus, yes.  And I have no idea what that would do to hamon.  Probably nothing good.  You should look way back in Jeff Pringle's threads in History about when a togishi opened windows on Roman and Gaulish blades and found hamon.  I don't remember if the steel therein had any P content or not.

[Christopher Price]

Having studied at Ric's feet and made quite a bit of Shear myself, I'm going to suggest it's not a particularly suitable replacement for Japanese "look" in your blades. It is its own historical material, with plenty of examples of how it weathers and finishes.

If you're really going for all the Japanese properties, I'm not sure you can short-cut making Orishigane, which is very nearly the same amount of work as cooking up blister and refining it to single, double, or triple-refined Shear in the Sheffield style.

If you're stuck on starting materials and trying to avoid modern knife steels in the process, getting either some reasonably clear Mild Steel (or double-aught iron if you can find it) and white cast iron (which you can make by over-cooking and melting your blister material) should be the right mix of ingredients to fold up into something recognizable as Japanese tradition, since that's what you're aiming for.

[Aiden CC]

Thank you for the replies, I definitely have a lot to think about. One thing I think I need to do is get more familiar with the different features of the hada in tamahagane/oroshigane blades. In the past I have focused on geometry and hamon, but just from reading general sources it's clear that there is a lot out there on hada as well, though maybe not as much clear guidance on how to actually control the outcome as there is for making hamons.

 

20 hours ago, Alan Longmire said:

If your feedstock is something like recent anchor chain, that stuff is usually very clean indeed.  If you use wagon tire as feedstock, it'll be far less refined in general.  

As chance would have it, those are the two types of wrought I have the most of. I got the wagon tire since it seemed it would be much easier to flatten into bars for carburizing as well as cut into pieces for a hearth melt. I actually prepared two pounds of that material each way as part of looking into this. I ran a carburization cycle on it to reasonable success. The "blister" steel only has a few actual blisters but sparks like crazy. I may try forging a high layer count small seax out of shear steel and compare it to hearth material from the same feedstock at the same number of folds to see the differences for myself, probably with a hamon on each.

 

Also, thank you for the recommendation of Jeff Pringle's threads, I spent a while pouring over them yesterday! A lot of good stuff there I hadn't seen before. I was able to find the article about a polished seax in the Wayback machine, but clicking on the image to try and see it larger led to a dead link . 

 

@Christopher Price thank you very much for the advice. I will also try to optimize my hearth melting process. This effort was inspired in part by three disappointing runs in a row; one that yielded one piece of excellent material, but a puddle of cast iron, a second where I overcorrected and made a mix of low and high carbon that was poorly consolidated, and a third run which yielded only cast iron. I think starting with chunks instead of nails may help me with consolidation and only doing one run per burn will likely help with consistency. It's definitely a process, but if that's how I get the right material, I'll keep doing it.

 

As for forging cast iron/ultra high carbon steel, do you have any advice? I found that if I start at a low heat that the "cast iron" chunks are in fact forgeable, and with some hammering become much more manageable once they are flat. I may have some trouble getting a base plate to start a stack on though since they do tend to fracture when trying to straighten out bends too aggressively. Starting with ~2% carbon (my guess for the concentration based on some of the behavior) may allow me to get a high fold oroshigane billet. My hope is some of what I have is more like dirty crucible steel than true cast iron.

[Christopher Price]

My research and experience is that you're not trying to forge the cast as-is, but rather run it through a hearth to de-carb some of it and end up with fairly high-C steel. Blending that and your Iron together to get your blank, if you're doing it Kobuse-style. If you want mono-steel, I think you're aiming for anywhere from 0.55-0.75% C, trending to the lower side of that. Katana were generally not high carbon the way we think about it for knives, and it's that low hardenability and lack of alloying elements that gives you the options for interesting hamon and all the other structure they play with.

So to make Orishigane (your home-made sword steel) you're just adding in things to get to your desired %C level. Poor smiths without access to good Tamahagane would run busted up tea pots through their hearth to de-carb, and run nearly clean iron through the folding process to get the core bar.

[Aiden CC]

Ah, that makes sense about putting cast through a hearth (a second time for my material) rather than forging. I had heard about the teapots but never seen too many details. I’ll probably try a decarburizing hearth run at some point with how much cast I’ve accumulated. 
 

Here’s the raw material for the comparison. Coarse wrought that I think are wagon tires. They were fairly thick and crowned on the outside. The hoop these used to be must have been pretty big. One was 30 Oz, the other 35 Oz. The first bar I’ll make into 12 fold shear steel, the other 12 fold hearth steel. I’ll compare the appearance, quality (defects and carbon content), and yield for the two processes.  
 

I hammered out one of the bars into a thin plate and cut it into 12 strips which I carburized for four hours. Not many blisters but plenty of sparks. With this thin of material I didn’t plan to try and get it super high C on the outside since my case depth should go all the way to the center. These are the bars after the first four folds. I didn’t refine the wrought iron at all, so these started out behaving badly but got better quickly. They aren’t cracking or shedding tons of slaggy scale anymore. 
 

Looking at some pictures of different hada patterns I think I can see what Alan was talking about with longer grains in shear steel, referring to silica inclusions as opposed to crystallographic texture if understand correctly, as the stringers will be essentially continuous and just get longer through the process whereas in consolidating a stack of little tiles, the initial length of a given inclusion is much shorter (maybe 1000s of times), starting out as a tiny globule from the melt squished into a disk when making tiles. I’m curious to see how much tons of folding changes this. 

[Alan Longmire]

12 hours ago, Aiden CC said:

as the stringers will be essentially continuous and just get longer through the process

 

Exactly what I was trying to describe!  

[Aiden CC]

I got a little more done on the shear steel side of things, and I also worked on a little more "raw" hearth steel, though I really want to do the comparison with the exact same feed stock.

 

The first phot shows a 6 fold offcut on the left and an 8 fold combination on the right. With my starting stack, that makes for about 1500 layers. I will probably fold one or two more times since hearth steel starts with 2 or three "layers" before folding. I guess I could work our an equivalent amount of deformation from the feedstock for both materials too, but layer count is a rough approximation. At 6 folds, I measured the mass, and determined that I had a yield of 49% measured from the mass of the material as received. I would say that this is definitely tolerable since it took an hour of forging to flatten the wrought iron, some material was lost in cutting the strips with an angle grinder, and then the folding. This material gave off some of the nastiest, slaggiest, scale I have ever seen when I was beating it into a sheet and in the first few folds; I would say a few percent of that loss might have been for the best. I also theoretically added a bit of mass when I carburized it.

 

The second photo shows a (terribly out of focus) fracture surface of a test sample at 6 folds. At this point I'm paranoid about decarburization, so I made a little coupon and heat hardened it with a torch. One hit bent it very slightly and a second broke it clean through. I couldn't get an in-focus photo, but I feel pretty good about the test. There is pretty much no ductile character to the fracture, even though it bent a little. My guess is medium carbon at this point. The grains are a bit big, but this also was from a piece that was just at a welding heat before cooling to room temp and had no grain refinement treatment. This break was in the transverse direction, you can see some of the layers on the left side and what might have been the flaw where the fracture nucleated. 

 

Thanks for looking! More on this after I finish a commission and a few other projects I have been putting off.

[Aiden CC]

Upon trying and failing to make shear steel a second time, it seems to me that it doesn’t really offer an easier route to shop/made steel, and on top of that, doesn’t quite match the look of the steel I’m trying to emulate. I just made 10+ lbs of hearth steel, so I’ll likely just work through that for the time being. 

[Emiliano Carrillo]

I spent two years trying and failing at making good oroshigane because I was using feed stock that had too much phosphorous in it. Nowadays I only use the cleanest iron I can find to make my steel, so the regulating steel is as close to iron with some added carbon as I can get without any random alloying elements in it. My guess would be your issue has to do with your fire and the starting material. I would sometimes get material that could make hamon after 10-12 folds, but it was always very faint and would only really show up in the right type of light. I'm guessing those pieces were around .3%-.5% carbon at best. I was doing all of my work with a press which sped things up but not tremendously as the power wasn't there.

 

What I would recommend is to try and find something relatively pure, real 1018 is a good get if you can find it, as it has low carbon and a low alloying elements, and use that for your melts instead. The only way I've been able to make good progress with this has been by knowing my material as well as I can, and starting with 'random' material that you don't know the makeup of is a surefire way to get into trouble. For all of the time and effort that goes into forging a blade out of this stuff its a shame if you don't know you have a good shot at a nice high carbon piece. I know its old advice, but the whole 'find steel you like and buy a ton of it' isn't too far off here, I bought as much iron as I could find when I knew what worked for me, and haven't looked back since. 

[Aiden CC]

Thank you very much for the advice! I actually started with 1018 back when I first tried hearth steel a year and a half ago. I got poor consolidation and carbon uptake and (erroneously) blamed it on the feedstock lacking slag, etc. Next time I do a batch of melts, I’ll use 1018 for a few. The Mn gets oxidized out generally, right? I have a box full of off-cuts mostly labeled with the alloy plus about 20 lbs of thick section 1018 bars for ni-mai knives, axes, etc, since I got tired of A36. I’ve heard that anchor chain is a pretty clean wrought iron, and for me has been one of the easiest to source. Do you think it could be a good direction to look into for an “old” feedstock? 

 

As for phosphorus, was it your experience that you could make high carbon material which would later lose carbon quickly in folding? I was initially worried, but once I could make good (initial) material I guess I thought (perhaps incorrectly) that I was in the clear. On a related note, I’ve been thinking about pattern welding with my own material, do you think the high P stuff could be used for contrast in a twist, etc? That could be a nice way to make lemonade if it turns out to be my problem. I think my fire control is getting there, my most recent run produced 3.5/4 pucks in one piece that sparked well everywhere. 
 

I’m curious to see how my first remelt turns out. Because it had so much cast iron in it, I actually ran a net decarburizing atmosphere, which seems like it could have the potential to “clean up” the metal a bit with the air blast, though I’m not super familiar with phosphorous removal. There was still some slag that came out too, though probably not enough to really react much with the melt. 

Edited April 11, 2022 by Aiden CC

[Daniel Cauble]

To me, shear steels are not nearly as good looking as folded hearth steels.

 

I second what Emiliano expresses about clean starting materials. Some of my work and info in my hearth thread were made from remelted bloom/wrought, but a greater majority was the melting of 1018. Low enough S&P, and while it has high levels of Managanese, the hearth process removes it.

 

I have found in foundry journals that the addition of silica to a low temperature melt has an effect on lowering P levels. It so happens, I cast sand Into the fire during melts. I haven't done before and after analysis, but the effect seems to be specific to lower melting temps and doesn't seem to work the modern day steel foundry temps (5,000F~).

 

I have melted a lot of 1018 with sand addition and without. Both product seem to consolidate well for me and act more like a modern steel (with no managanese)manganese.

 

The only issues with oroshigane and the lack of slags are issues that happen during the folding process. It's is much more difficult to fix delams or bubbles in a billet vs doing it with tamahagane. This was told to me by one of these swordsmiths on social media, and I find it to be true with my own struggles.

[Christopher Price]

I make and use shear not for fancy looks, but to replicate appropriate material for historical reproductions that call for it. That limits you largely to Colonial America, and some adjacent English work of the 16th-18th centuries, for any recognizable application. Of course variations of it exist in antiquity, but from my research, this is where it shows up most. I also adapt it to serve as "piled steel" in old Roman or Norse work that is just layered up carburized iron.

[Aiden CC]

I still have a lot to think about with regards to this, but from what people have said and from my own experiences, I think I will be abandoning shear steel for the time being. I have been able to get some time on a press which has let me prep a lot of hearth steel and save the carbon content through a lot more work. I will likely conduct a number of melts in the near future and will definitely be throwing in some 1018. I also have some scrap "modern" steel (fairly old, but definitely steel) that I will also try with a melt, mostly because it has some significance due to its source. 

 

On 4/19/2022 at 1:06 PM, Christopher Price said:

I also adapt it to serve as "piled steel" in old Roman or Norse work that is just layered up carburized iron.

Out of curiosity, what kind of layer count do you aim for on work like this? I am getting to the point where I can make a bunch of knives from my own material (I have about 1800 g of high carbon material at 3 folds) and am thinking about how far I want to take it refinement wise for different projects. For Japanese work, I have a good idea of what I want to do, but am less sure for European inspired pieces.

[Christopher Price]

If memory serves, most historical examples are in the 100-300 layer range. That's what I've done, and I've been pleased with the results.