More Hearth Steel

[Aiden CC]

I finally have some time for knife making and one of the things I've been working on is making more hearth steel. I want to get enough for a tanto, which has been somewhat of a challenge because of a persistent problem with carbon distribution in the initial pucks, more on that later.

 

On the suggestion of J. Arthur Loose, I got a used HVAC blower (an Amatek Windjammer) to replace the shop vac I was using. Definitely a fan (), it's quiet and powerful and the setup wasn't too bad. With a DIY three prong plug and a 0-10V DC power supply it was ready to go and offers very precise control over the air supply. On the right are the materials for one of the melts. This one was an assortment of drops, a mix of high and low carbon steel. I did two other runs with wrought iron nails from the Globe Elevator. I have read a few accounts of these containing phosphorous and hindering carbon uptake, but I was able to get some high carbon steel from them.

 

This is an attempt to show what I was talking about with carbon distribution. This is the puck from the shop scraps after I flattened it, quenched it, and then started breaking it up with a sledge hammer. These is a very clear demarcation between high carbon steel (the top, note the clean break) and the bottom (the bent piece resting on the anvil). The break test results also match how the material sparks. This is something I have noticed across all of the melts I've done; the top side is very high carbon and almost free of voids while the bottom side is more porous and much lower in carbon (with a few pockets of high carbon). I'm not quite sure what to make of this and would love to hear anyone's thoughts on it, but I have been able to work with it.

 

This shows all of my viable material so far sorter by carbon content. The left is all or mostly low carbon, the middle is medium carbon or a mix of high and low carbon, and the right is very high carbon.

 

Since this will be made into a Japanese style blade if it turns out, I decided to take the Japanese approach to consolidation. This is all of my best material, every piece consistently sparking with more branches than a test piece of W1. I would have loved to have a handle or a larger paddle, but that wasn't really possible given the quantity of material I was working with.

 

Here it is in the forge, along with one of the wrought iron nail pucks. For the first few heats it looked like it was going to be a resounding failure, but somehow it all came together. On the right is the billet after two folds. Since I hope to make this into a tanto, this will get a tone more folds, maybe 8-10 more. I will also likely have to add material from as I go or maybe make one or two smaller bars and weld them all together. If worse comes to worse, I can consolidate more of the low and medium carbon stuff and make some kind of composite. The 12" sunobi may also be too ambitious of a goal which I might have to reevaluate, but I guess we'll see.

 

Thanks for looking, and again, any insights on the carbon distribution (lots on the top and very little on the bottom) would be greatly appreciated!

[Daniel Cauble]

Have you checked my thread a ways down?

 

The likely reason why you are experiencing low carbon at the bottom and really high at the top, is because you really need the lower chamber to be hotter initially. Perhaps a longer pre-heat before the first injection of material. When the furnace isn't hot enough, the iron doesn't stay molten for long and could freeze up before it reaches the maximum bottom, which also leaves decreases carbon uptake since most of it is from the atmosphere when it is molten. This eventually builds up and the last of the material to be melted is very close to the hottest zone (tuyure blast) thus stays molten or very close to much longer with a lot of CO. 

 

I also feel like there may be too much scale on your plates for tsumiwakashi. Try to steam blast scale away prior to, or even vinegar soak to remove scale. The inclusions are already present in your initial consolidation and will probably follow you through the folding process. This materials doesn't quite behave like bloomery or tamahagane in which those materials still have enough slag in the beginning to allow easier mending of cracks and delays like that. I have followed many Japanese swordsmiths and this is one of the lessons I have seen shared. Plus, I've had it happen to me.

 

I personally only use a small air matress blower for this. If you are using a standard 12"^3 furnace, it's all you need. Too much and you increase your chances of making a puddle of cast iron.

Edited May 30, 2021 by Daniel Cauble

[Aiden CC]

Thank you for the advice Daniel! I read through that thread (and watched a number of your YouTube videos) when I first decided to try this last year, but it’s probably worth revisiting. It would make sense that the bottom of the fire isn’t hot enough. When I upgraded my blower I noticed the steel came to rest lower, but not quite to the bottom. I’ll try running the furnace longer on startup. Do you think angling the tuyere down more could help with that as well? It’s currently only a few degrees below horizontal. 

 

As for the scale, that may be the case. I’m going to clean up my billet with a grinder to check the welds. It actually looks fairly solid other than a few unruly pieces. I think I also made my plates a little too thick; even the very high carbon pieces required a lot of force to break. I have one of the nail billets mostly flattened out, I’ll try steam blasting for the scale before I break it up.

[Joshua States]

Awesome work sir! This is always sitting in the on-deck circle for me to try again. If I may ask, which Amatek Windjammer did you get?

Daniels suggestion is intriguing. 

On 5/30/2021 at 7:35 AM, Daniel Cauble said:

a small air matress blower for this

I have a small battery powered one that doesn't have any real use anymore.

[Aiden CC]

@Joshua States sorry for the late reply on this, if you’re still interested it is one of the 116630 line. I don’t know how much the specific capacity matters, I’ve so far never used it much over 50% of the max control voltage. The output also happens to be an excellent fit in the ID if 3/4” pipe,

forming an adequate seal with no fittings or tape. 
 

In other news, I seem to have overcome the “two tone” carbon content problem I’ve had. Adding more angle of depression and upping the blower speed meant the bottom of the furnace was hotter. So I can remember, I used a control voltage of 6.2 V, YMMV. 

It may be a bit hard to see here, but it’s running hotter than before especially lower down. I didn’t time each charge, but it was faster than last time. 
 

The top then bottom. Lots of shiny bits! Most spots spark like W1 or more.  The feed stock was 900 g of Globe Elevator nails. It seems some have had trouble with phosphorus inhibiting carbon uptake in these, but I think I've

gotten lucky with my batch because all of my melts with them have yielded at least some very high carbon portions. That’s nice because I still have 20 lbs of them. 
 

Some more close ups. I’m excited to forge this, but I have a good bit of custom work accumulated during a recent vacation as my first priority. I have a project for this, but I think it needs at least one more puck. My W2 test blade came out to 354 g, but I need 10-12 folds as well. I started the soft metal work months ago but have been stalling out on the steel. It’s nice to start getting some more consistent high carbon stuff!  
 

Also, @Daniel Cauble you were right about the scale on my wafers. I started to have problems with folding that billet and thanks to your warning saved a lot of time by not chasing them too far. The average carbon content of that stack was maybe 0.6% which is not quite what I need  especially with all the loss from slowly forging it out by hand and alone. 

[Aiden CC]

Back at it again. I did two runs of 900g this afternoon. One at 6.2V and one at 5.4V (those numbers are mostly for me). I got excellent carbon content but poor consolidation. 
 

Running the furnace quite energetically as I’ve found that higher temperatures have given me better steel. 
 

These are all the pieces I pulled out hot. The biggest one is almost but not quite all of the first run while the second split between the second two. Everything but one or two pieces sparks like crazy, I’m pretty excited to start working this stuff! 
 

These are the stragglers I dug out of the furnace after it cooled off a bit. The super globular one looks like it could almost be cast iron though I haven’t spark tested it. 
 

A cool shot showing the glass formed from the slag in the nails (the greenish beads spread throughout the steel). Everything I pulled out was sizzling which may have been some combination of liquid slag and steel. Also, the pucks were sitting notably lower in the furnace. 
 

I hope to start working this stuff soon, I may finally have enough for what I want to do. Also, if anyone has ideas about why my higher carbon pucks have poorer consolidation I would be very interested to hear it. 

[Aiden CC]

Yesterday I was able to get in some time consolidating this most recent melt and some odds and ends. 
 

This is a little stack of all more of the high C pieces collected from my worse earlier pucks. 

This is all of the material from my last run flattened out. Minus the cast iron and a few small/low quality bits, it totaled about 1100 g at this stage. 
 

This is where all of my “bars” are at this point. That billet from earlier I though was failed got a bit nicer after four more folds and is now at six folds. The big crusty one has a large piece almost cracked off so it will take some love. The three fold stack (from the first picture in this post) is consolidating quite nicely and still sparks like crazy. 
 

The ugly edges of the six fold bar. This one never had great C content and has lost some of what it had, so it will likely become the core steel for a blade. I may actually have enough here for a knife! We’ll see at fold 10-12 though. 

 

[Joshua States]

Go man go!

 

[Aiden CC]

Thanks, Joshua! This project is definitely more marathon than sprint. It takes quite a bit to amass a big bar if this stuff! Luckily, I think I’m really getting the hearth operation down. 
 

It saves a ton of charcoal to do consecutive burns, but things overheated a bit with the second run and made what looks cast iron (left to right is the order of the runs). Run 1 (5.0 V) created poorly consolidated high carbon steel, run 2 (4.5 V) created cast iron I believe, and run 3 (3.5 V) made well consolidated steel with perhaps less carbon than round 1. I hope to start consolidating tomorrow. 

[Francis Gastellu]

I'm always in awe of this kind of dedication. It's great to see your progress, thank you for sharing!

[Aiden CC]

On 11/13/2021 at 11:09 AM, Francis Gastellu said:

I'm always in awe of this kind of dedication. It's great to see your progress, thank you for sharing!

I’ve enjoyed following your journey working with home made steel as well! Admittedly, the effort of consolidating this stuff stalled me out for a while but I finally got back to it. 
 

Definitely a long job to consolidate this by hand! The natural tendency is to let the billet get wider and wider, I’ve found that you really need to stay on top of that by drawing out to a fair length before folding and doing a few strategic “hot dog bun” folds. 
 

Here’s all the material I have up to six folds. This represents 2-3 pucks since one of the pucks in my last post was too high in carbon to forge. I plan to use some as is (seaxes, kitchen knives, et) and weld some together to get up to 10-12 folds. It’s 806g of material which gives a yield of approximately 40% from the raw nails, actually a lot more than I would have thought. The bars are each fairly small since I found I can move and fold them much more quickly at that size, hopefully offsetting the extra total surface area. 
 

Hard to do this one handed, but here are the sparks. 
 

Maybe some day I’ll get to actually make something out of this!

[Joshua States]

Still looks pretty good. Are you going to try and make that stack into a single bar now?

[Aiden CC]

With all of my various projects, I exhausted my supply of home made steel, which called for a hearth day. It saves a ton of fuel to batch these runs, so I did four in a row. When doing consecutive runs, it’s really important to watch the fire and lower the air or you’ll make tons of cast iron if it gets too hot. I have found that 6 V on my blower control consistently works for a first run, but will be too much for a second. 
 

Following some advice from @Christopher Price, I ran some cast iron and wrought iron (all from previous melts) for my second melt, shown above. The first was an old wagon tire cut into pieces, and the third my usual WI nails. 
 

For my last run, I decided I might as well try just sticking a wagon tire chunk in the hearth and let it melt down. Worked a lot better than I thought it would! Also shown is a spark arrestor I added to my setup. 

 

These images show both sides of the puck. From left to right: wagon tire small pieces, nails, remelt, big tire chunk. 
 

All is good steel except for some of the pieces of the nails, which melted completely and made (white?) cast iron. I think my consolidation problem may actually come from the small size and long shape of the nails causing them to melt into several “droplets” and not join up very well. I may be able to consolidate this batch on a press, which would be stellar. The forge there can’t weld too well though, so it might mostly be drawing out really long bars, then welding them in my forge and repeating that cycle. 

[Aiden CC]

I found some time to work on the most recent batch and things are looking pretty promising. 
 

I was able to work on these with a press, but wasn’t really able to weld while using it (the forge in that shop isn’t built to deal with flux and doesn’t have the ability to run both hot and rich from what I can tell), so instead of folding, I drew each billet out into a long bar and welded in my own forge. I consolidated by hand, but the total mass lost when going from roughly squared to basically three folds was only 10%, which was a huge improvement. All three spark very well. 

 

Here’s where everything is now, the wagon tire material (first and third) are out to three “folds” (i.e. 8 layers), the remelt material is at two folds. The rightmost piece is my first piece of pattern welding with this material. 
 

It isn’t much, but I’m happy with it! Eight layers, alternating anchor chain and 0 fold hearth steel, or maybe 3 fold since I started with two layers and did cut-and-stack (since folding always doubles up a layer) to get 8 layers. I’m glad there’s some contrast, which I hope is also a good sign for the carbon content. The plan is to draw it out into a bar and twist it. I’m thinking of welding up some twists “2x2” like some old seaxes, so I figured low layers would work best with smaller bars. 
 

Hopefully I’ll get some more done on this soon. Thanks for looking!

[Aiden CC]

Getting a press has made this go much faster, I actually have my first finished knife made from this material now. 
 

These two bars are both 8 layers of hearth steel made from wrought iron wagon tires. The sparks look like approximately 1% C, but hard to tell exactly. 
 

This nakiri is welded up from a piece of anchor chain with a piece of hearth steel welded in warikomi fashion. I decided not to etch it, I may try some stones or possibly just leave it to patinate in the kitchen. 
 

These two blades are through heat treatment, but likely won’t be finished for a while. One is inspired by knives from the Viking age, the other the Iron Age. Both have full-length wrought iron tang I’m going to try and bend into loops. 

[Aiden CC]

I recently did another hearth burn with four runs, all wagon tire sections stuck into the hearth in one piece, about 10 lbs total. All of it looks promising so far, three pucks went straight to the press and one was quenched for examination. 
 

 

 

I also etched my first piece of this material with ferric chloride for a recent project:

This is 8 folds etched in FC with scotchbrite for the oxides, a very different look than what you get from lemon juice and polishing compound. This knife actually has a (very high) hamon, but it’s hard to see. It follows the part of the blade with colored oxides after the quench in my previous post.

[Emiliano Carrillo]

Nice work Aiden! That looks fantastic! 8 folds is what I usually do when going to medieval or viking age work! 

[Aiden CC]

1 hour ago, Emiliano Carrillo said:

Nice work Aiden! That looks fantastic! 8 folds is what I usually do when going to medieval or viking age work! 

Thank you, it means a lot! I'm excited to see how this batch and the last one behave with more folds in some Japanese style blades in the near(ish) future as well. A pretty active auto-hamon was peeking through during polishing, but I wanted more of an etch so it's mostly buried. 

[J.Arthur Loose]

Perhaps more bricks stacked horizontally for better heat retention? Lower blast pressure? Hard to say but I’ve never had that happen and those are two differences I notice right away. Here’s my usual set up and a freshly consolidated puck.

 

 

[Aiden CC]

Is that after just the initial heat of consolidation? If so you’re definitely getting more well consolidated pucks than I am out of the furnace, that looks quite nice! It looks like you have a smaller cross section which I could imagine helps. I did also squeeze one or two of mine before the hottest parts were totally solidified, and I made some mistakes on the press since I’ve never done this step that way before. A single large piece of feedstock (~2.5 lbs) charged vertically has worked far better for me than the same weight of nails/scraps for consolidation though, and the pucks are much more solid now. 

[Aiden CC]

Got some more done with this material and I’m wishing I’d bought a press a year ago! 
 

I drew out some 8-fold material to use for a bit of pattern welding, this bar was a remelt and from a mix of cast iron and low carbon scraps from old nails. 
 

My pattern welded bar was three layers of hearth steel and four layers of anchor chain. I wanted enough for four 1/4” bars for a broken back seax, I ended up with about twice as much as I needed which was definitely nice. 
 

Here is all of my material right now, minus a box of little pieces. The pattern welded bar is 24” long and 3/8” square, a kiss block helped here. I also have one bar ready to be laminated with wrought iron for an edge bar billet . I thought I made a lot of material, but I have some more ideas so I may need to run another 10 lbs soon!

[Aiden CC]

I posted these in a show and tell thread, but I figured I would add them here with some other commentary. 
 

This is my most recent run, five pucks, a total of 5.1 kg of feedstock. From left to right: old window bars (high P?), wrought iron brackets that didn’t forge well, a single piece of wagon tire, a failed shear steel experiment (wagon tire strips), and anchor chain scrap. The shear steel scrap consolidated quite well and is now at 8 folds. 
 

This is my first pattern welding with home made material. The edge is made from a remelt of multiple failed batches of hearth material (wrought and cast iron), some of which was old nails which may have been high in phosphorus, that and an auto-hamon gave it a lot of contrast. The center bar is anchor chain and hearth steel from wagon tire, the back is wrought iron I bought as 1/2” round bar from some unknown prior life. 

[Gary LT]

Man Aiden, I really like what your doing and I’m enjoying this shared venture. 
I believe everyone is as well, so keep up the photos and details!!

Gary LT

[Aiden CC]

Thank you Gary, this feels a bit like a journal sometimes, I’m glad some others are getting something out of it too. I actually got a small hard covered notebook to keep up with this stuff, my various note pads pads and scraps of paper have often met wet, dusty, or charred ends. 
 

I’ve been steadily cranking away with the run of material from my previous post, some of the updates are in my Hearth Steel Seaxes thread. Pucks four and five are completely consolidated, with four being about half gone from use in a few seaxes and a funayuki experiment (did not go well, I forgot photos though). 
 

Pucks after one heat and three folds. Previous failures have led me to really focus on cleanliness. Lots of brushing and each fold is preceded by a thorough scrub and forging with water to blast off the scale. I’m also getting more used to the press and not popping welds nearly as often. 
 

This is the entirety of puck number five combined with a prior wagon tire melt that proved to be well behaved (no hot or cold shortness). I originally got into this to make Japanese blades, which is where this material is going. Sources from two feed stocks combined after six folds, which from what I have found is one of the ways to hada was manipulated in nihonto. 
 

Here’s the results. The 12 fold bar weighs 700 g, meaning it should be enough for two tanto with a kobuse construction. The left is the largest piece of puck two at six folds. I left it there because it gives me a few options; combined with more material I could prepare it for a Japanese blade, it could be folded a few times for edge material, or it could be added to pattern welding (though I will probably test all of my wrought and hearth for etch contrast before I do that). 
 

Finally, here are a few etched blades. The hearth steel tends to weld to wrought iron very readily and sometimes with carbon diffusion it’s like the cladding gets “transparent” when you grind it close. It gives a lovely ethereal look like the narrow sax balde above. The small seax is my best “warikomi” (I feel it happens a lot that the only word around for stuff like this today is Japanese, though I’m sure there was a name for it elsewhere) with this material. Because both materials have layering and a bit of silica, it’s very hard to pick out the weld line before etching, even though a hamon would pop out immediately at coarse grits. I guess this makes sense as many old nihonto are “hon-sanmai”, which means they have both a hamon and a weld line running along the length of the blade, but only the former shows clearly in the polish (I’m sure connoisseurs can pick out both). Based on metallurgical analysis of contemporary finds, the sax that was given a Japanese polish was likely a composite too, but looks basically like mono-steel with a narrow hamon. The point of that tangent is that with a shallow hardening, layered steel welded to wrought iron, I found I needed to etch frequently to make sure the grind exposed the hearth steel in a similar, and visually pleasing, way on both sides. This is what I have done on my last few blades, with decent results. 
 

That’s all for now, thank you for looking!

[Alan Longmire]

This continues to be an excellent thread!  Thanks for updating it.