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I have been wanting to try a hearth furnace for several months now, but a leak in the master bathroom and the resulting repair work has had me occupied for a long time. Today I finally said I need eda mental health day and to do something fun. So hearth furnace run one. Did the (what seems to be becoming the ) standard 7 brick furnace with the blower from my first coal forge. Charged it with 5 - 200 gram charges of A36 that I had sitting around. Time between charges was about 5-6 minutes. Total recovery was about 800 grams.

4_HF Assmebled_IMG_2166.jpg

 

Furnace before first charge.

7_First Charge_IMG_2173.jpg

 

Had two pieces come out. Here's the main one. Is about 770 grams.

11_Main Bloom_IMG_2192.jpg

 

Spark test of beginning material.

14_Spark test starting material_IMG_2239.jpg

 

Spark test of furnace material. Same belt, same grinder speed, same pressure as the starting material picture. Any thoughts on carbon content? Also, as I was consolidating it after pulling out of the furnace, it seemed super solid. I was not able to move it much with a 4 pound hammer.

15_Spark test hearth steel_IMG_2242.jpg

Edited by Bill Schmalhofer
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So colder weather is upon us and I now have a chance to fire back up the hearth furnace. During the break away from this I made a new base for holding the bricks. It's made from cast-o-lite 3000

I have been wanting to try a hearth furnace for several months now, but a leak in the master bathroom and the resulting repair work has had me occupied for a long time. Today I finally said I need eda

Hearth furnace Run 3 - Experimenting how to load 100 bottle caps at a time per charge.   First idea was to load them in paper sacks and toss a sack in per charge. As is often the case, theor

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Looks like you have made some ultra-high-carbon steel or white cast iron, one or the other.  You're on the right trail, but you may want to level out the tuyere a bit more to lower the end carbon content, if that puck has too much carbon to forge.  Cool stuff!

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Thanks for the reply Alan. I had a feeling I was a bit high in carbon. The tuyere was almost flat in when I was running. I dropped it by a brick height from where it was in the first picture after I got the fire going. I was thinking I may have to point it down a bit more to add some oxygen to lower the carbon.  

 

I also have a question for those that run hearth furnaces. Do you slag any of your fire bricks? This is what is left of the brick that the tuyere was stuck through. I don't remember seeing anyone else on the forum have this issue. The two bricks next to this one also had some damage but nothing like this. 

 

Lastly, my plan had been to heat the puck up to welding temperature in my forge and try to consolidate it and forge it flat. I'm assuming if the carbon is too high, if I go this route, it will just crumble when I pound on it?

 

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Edited by Bill Schmalhofer
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Round two of the hearth furnace and I decided to put Alan's frequent comment (you can use bottle caps, cans, lids, etc) to the test. Started with 1200 grams of material and final puck was 860 grams. The first run went very slowly for some reason. Had a total of 6 charges at 200 grams a charge and was averaging about 6-7 minutes between charges. At the end of the run, pulled a puck out of the furnace that was almost dead even with the tuyere. Was able to distinctly make out a few screws and a nail sticking out of it. Went to consolidated it and it crumbled into 5 chunks. The furnace was still glowing so I just fired it back up and ran the chunks through (nothing to loose right?). This time the charges went much faster. Was getting three minutes between charges this time. Pulled a single puck out that was well below the tuyere. Several small pieces broke off during consolidation, but I ended up with the 860 gram puck. This time it turned out to be bi-polar. Decent carbon on the top and what looks like wrought iron on the bottom. Between the two runs I have about 1600 grams of material. First nice day that I can get my forge out, I'm going to process them and see if I can combine the two. And I slagged another fire brick that had the tuyere going through it.

 

1200 grams of starting material.

1_Starting material_1_IMG_2267.jpg

 

Material after first run through the furnace. couple of screws and a nail clearly visible.

8_Results #1_IMG_2278.jpg

 

Spark test of the top of the final puck.

11_Top material_IMG_2297.jpg

 

Spark test of the bottom.

12_Bottom material_IMG_2299.jpg

 

O1 as a comparison.

9_O1 Steel_IMG_2293.jpg

Edited by Bill Schmalhofer
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Toldja it would work. ;)

 

On any melt or bloomery smelt you're not going to have a homogenous carbon distribution.  That's why we hear so much about how many times the steel for katanas was "folded."  That's what you have to do to even out the carbon, assuming you want to even it out.  The other thing you can do is separate out the high-C stuff from the low, and use the high-C as blade material and the low C as wrought iron.  

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2 hours ago, Alan Longmire said:

Toldja it would work. ;)

Trust but verify...:D.

 

Don't think there is enough to be able to separate the two sides out. Going to try to fold and even it out and then combine with my first puck (if possible). It's interesting to note that when I did my first run, I was using fairly large solid pieces of starting material and the entire puck seems to be that super high carbon material. The second run was tiny pieces of bit and bobs and I got the very heterogeneous mixed puck. Have to keep track of this observation...

 

Also, the first puck is a solid chunk. The second one looks like a sponge on the edges - like something was being aerated through it as in sat in the charcoal. Any thoughts on this?

 

Thanks again for all your help.

 

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I've gotten the foamy outside when I use little bits as well.  I suspect we should turn the air down a notch when doing small stuff, but what fun is that? ;)

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Looking good Bill. I still have a 3/4" square bar somewhere in my shop that I made from one of these little runs. I got a lot of slag bleed out from my bricks too, but nothing quite like you have. I got some good tips and feedback on that post back in April 2018.....holy  jamoly almost 3 years ago. Check it out.

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17 hours ago, Joshua States said:

Looking good Bill. I still have a 3/4" square bar somewhere in my shop that I made from one of these little runs. I got a lot of slag bleed out from my bricks too, but nothing quite like you have. I got some good tips and feedback on that post back in April 2018.....holy  jamoly almost 3 years ago. Check it out.

Thanks for the link to that thread Joshua. Good read. I feel very much like you did. What the H _ _ _ am I doing and am I doing it right. Alan's comments on Goldilocksing (not too much this and not too much that - JUST right...) the puck is what I was looking for. The first puck is pretty solid but unfortunately very high carbon. Worried it's just going to crumble on me. I'm just hoping to get enough to make a knife from. If successful there, I may be hooked on this. Drinking way too much beer to save up more bottle caps for the next run though :D.

 

Since I don't have a designated forge area, don't know when I'm going to get to consolidate this material down. Hoping for a nice, semi-warm day some weekend.

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If that first one proves to be too HC to forge, you can always run it through again with a slightly down-angled tuyere to decarb it.  When you make the steel, you can do whatever you want!

 

(This is how we hook you, you've been warned!:lol:)

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  • 1 month later...

Funny update to this. Was talking with a friend a bit ago about this process and he said "I've got some bottle caps if you want them". Not wanting to seem rude, I said "Sure I'll take them".

 

This morning at work he dropped off a box weighing 11.2 KG of bottle caps. He said he's been collecting them since college and things got carried away. Then it got to be somewhat sentimental he didn't want to just throw them away. When we were talking he thought he knew exactly how to get rid of them. His wife is happy too!

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Yes it was a big score. The best part is now I have lots of material for my demo. For unknown reasons, someone I know has asked me to do some demos on running hearth furnaces. Now I have plenty of starting material.

 

I also feel I owe him something made out of his bottle caps (once I get time to process all this material) :D.

Edited by Bill Schmalhofer
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  • 2 weeks later...

The past two weekends have given me at least one day that was beautiful and so I finally got a chance to consolidate my two pucks. It was quite a learning experience and in the process, I lost quite a bit of material. Lost is a relative term though because everything I "lost" went right back into the scrap bucket for the next hearth run. The ultimate in recycling...

 

Last weekend I started with both pucks. I'm thinking I need to make a bigger forge as these almost didn't fit in my current one.

 

1_Pucks_IMG_2420.jpg

 

Got them both consolidated down to nice looking bars and then got greedy. I let them get cool while I worked on something else and then went back to try to forge weld them together without cleaning them off. Needless to say the welding didn't happen. I made the problem worse by trying to fix it. This was where I "lost" most of my material. I cut the losses and waited until this weekend.

2_Consolidated_IMG_2421.jpg

 

After cutting off all the nasty ends this is what I was able to salvage out of those two bar.

 

3.1 Stack_IMG_2437.jpg

 

Here is the stack all tacked up waiting to be stuck in the forge. Was able to weld this together and draw it out. Partially cut it in half, folded it over and welded it together. Did this cut and weld a total of two times. Don't know how this kind of work gets counted, but by the pattern welded criteria, it is 28 layers.

3_Stack_IMG_2441.jpg

 

Here's the final bar fresh from the last welding pass.

 

4_24 layers_IMG_2446.jpg

 

Cut off the nasty end and it looks solid through and through.

5_Nasty end cut off_IMG_2452.jpg

 

And the spark test:

 

NJSB 1084 as comparitor

 

6_NJSB 1084_IMG_2457.jpg

 

And my bar. To my eye it looks pretty close. Both ends and all edges spark the same, so I think I got it pretty homogeneous.  Final dimensions are 23 cm long, 3.5 cm wide, and 0.6 cm thick. I think this is going to make a nice knife.

7_Spark Test_IMG_2470.jpg

 

On a side note, I'm kind of curious to see what the composition actually is. Is there a company I can send a sample to for analysis, and if so, any idea on how expensive it would be?

 

Looking forward to processing that 11 Kg of bottle caps!

 

Additional note, final yield was 426g bar. So final yield from raw starting material to usable bar is was only 19%. But I think I would have got a lot more if I hadn't tried rushing my first round of forge welding.

 

Edited by Bill Schmalhofer
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Looking good!  As for layer count, you could blow some smoke up the Mall Ninja's behinds by counting every bottle cap as a layer.  The mythical 6,000-fold steel! ;)

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On 3/28/2021 at 11:29 AM, Alan Longmire said:

Looking good!  As for layer count, you could blow some smoke up the Mall Ninja's behinds by counting every bottle cap as a layer.  The mythical 6,000-fold steel! ;)

I'll have to remember that when I process the box of bottle caps!:lol:

 

@Alan Longmire Actually you don't know how true this is. Just sorted the bottle caps into 200 gram amounts. My friend was a bit over zealous in his estimation but it still turned out to be 6200 grams. Works out to ~2 grams / cap, 100 caps per charge, 500 caps per run (keeping it to 1000g / run), "6000 layers" look out :D.

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Element.com will do it for around $115 per sample for a general mass spec

 

However, from experimentation and testing, it will likely be devoid or trace amount of Manganese, and being modern steels, scraps, it will probably have small amounts of nickle, copper, Chromium, lots of carbon, and relatively low S&P.

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6 hours ago, Daniel Cauble said:

Element.com will do it for around $115 per sample for a general mass spec

 

However, from experimentation and testing, it will likely be devoid or trace amount of Manganese, and being modern steels, scraps, it will probably have small amounts of nickle, copper, Chromium, lots of carbon, and relatively low S&P.

Thanks Dan. I'm just curious. Mainly I'm interested in carbon content (to have an idea on quench speed) and to see what else is in there (there WAS a bit of stainless in the second run). Also to know if it really is worth taking the time to forge this out (if for some reason the S or P is sky high).

 

Sometimes I think I'm part cat...Hopefully it won't kill me!

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I have use Element before, specifically the Wixom lab, as I have been there and know a (now former) metallurgist there.  For the most part I use IMR, specifically Portland, OR, for these kinds of things (simple testing that I just don't have the equipment for, or need 3rd party testing).  When I used IMR a few months ago they charged $47 for sample prep (my samples were already polished, but they need to prep them themselves anyway) and $75 for full OES chemistry, so $122 total.  I also paid the extra $63 for a Nitrogen test, as that was what I really wanted to know anyway.  

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I would expect that they will each need a sample at least 0.25" thick and 1.25" diameter (2" diameter would be better) in order to run it in OES.  If you want a really accurate carbon and/or sulfur reading that will be another test that they will need to get shavings from the sample and then they will burn it (C/S combustion test, generally done on a LECO brand machine thus often called a LECO Carbon test).  I know that Element also does a few other interesting types of tests, too.  Like ICP.  

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Hearth furnace Run 3 - Experimenting how to load 100 bottle caps at a time per charge.

 

First idea was to load them in paper sacks and toss a sack in per charge. As is often the case, theory falls short when put into practice. As soon as the paper went up (obviously very quickly) the bottle caps scattered far and wide across the top surface of the charcoal. Trying to herd them back to the middle while trying to get a charge of charcoal on the top didn't work out very well.

1_Run 3 Starting material_IMG_2486.jpg

 

2_Run 3 five Charges_IMG_2487.jpg

 

Final puck looks like this spark test very uniformly across all surfaces. Only issue is yield was only 540 grams. Will have to figure out a better way to keep them all together when loading.

3_Run 3 Main puck_IMG_2494.jpg

 

 

Runs 4 and 5 were identical.

For some reason I have been saving the swarf off my grinder. I had over 4 kg of material. One of these steel cans pictured below weighs between 24-30 grams. I took 10 of them and packed in grinder swarf to balance them up to 200 grams each. Put the cut off lid back in and pounded them closed. This actually worked very well, although due to the large size of the can, the charge rate was about 6-8 minutes per charge and not the 3-4 minutes that is kind of normal. Had NO idea what the puck would look like, or if I would even get a puck.

 

4_Run 4:5 Five charges_IMG_2488.jpg

 

Proof is in the pudding. Spark test of the main puck from run 4. The whole thing sparks uniformly like this. Weight of puck 4: 764 grams

5_Run 4 Main pucl_IMG_2496.jpg

 

Spark test of puck 5. There is a small protuberance on one side that sparks like wrought with maybe a small hint of carbon.

6_Run 5 one tip of main puck_IMG_2501.jpg

 

Majority of puck 5 sparks like this. Weight of puck 5: 750 grams.

7_Run 5 Majority of main puck_IMG_2504.jpg

 

All in all a good day of playing with fire and hot metal. All three pucks packed down fairly compactly. Should have no issue getting them into my forge for consolidation.

 

A general question referring to runs 4-5. What is the general consensus concerning the make up of grinder swarf? I'm pretty sure the carbon is basically non-existent

in what is coming off the belt. But is it known what happens to the rest of the alloying elements?

 

EDIT: I found a lot of the "missing" bottle caps. As I was breaking down the furnace last night, I was noticing all these little nodules that were not charcoal. Went and got a big magnet and lo-and-behold, the nodules are magnetic. Picked up about 375 grams of nodules from around the perimeter of the hearth.:lol:

Edited by Bill Schmalhofer
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On 3/29/2021 at 5:11 PM, Jerrod Miller said:

I have use Element before, specifically the Wixom lab, as I have been there and know a (now former) metallurgist there.  For the most part I use IMR, specifically Portland, OR, for these kinds of things (simple testing that I just don't have the equipment for, or need 3rd party testing).  When I used IMR a few months ago they charged $47 for sample prep (my samples were already polished, but they need to prep them themselves anyway) and $75 for full OES chemistry, so $122 total.  I also paid the extra $63 for a Nitrogen test, as that was what I really wanted to know anyway.  

So I contacted both companies, but have only heard back from one, Element (the Wixom lab). Just received the quote this morning and it was for $308.00. I am guessing I was asking for the wrong tests. If I contact them again, what should I ask for as far as testing is concerned to get the much more reasonable rates?

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Were you dealing with Jim Keiming?  He is who I was emailing yesterday and today to do some testing for us.  If it is him (or anyone else there, really), I would be happy to call them up and do all the technical communicating for you if you want.  Basically though, I think just asking for an OES (Optical Emission Spectroscopy) reading will tell you what you really want to know.  You'll probably want to clarify that there is not a specification your are needing to certify to, just informational.  How bad do you want to know your EXACT carbon?  Is +/- 0.05% close enough?  If you are wanting to really dive in on accuracy then the cost goes up, but I don't think that will be necessary for you on this one.  

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9 minutes ago, Jerrod Miller said:

Were you dealing with Jim Keiming?  He is who I was emailing yesterday and today to do some testing for us.  If it is him (or anyone else there, really), I would be happy to call them up and do all the technical communicating for you if you want.  Basically though, I think just asking for an OES (Optical Emission Spectroscopy) reading will tell you what you really want to know.  You'll probably want to clarify that there is not a specification your are needing to certify to, just informational.  How bad do you want to know your EXACT carbon?  Is +/- 0.05% close enough?  If you are wanting to really dive in on accuracy then the cost goes up, but I don't think that will be necessary for you on this one.  

 

Just looked back through the email stream and think I started in the Wixom lab and got shunted over to the Daleville IN. lab. The only "name" I have as contact there is DM and the quote came from Elizabeth.They were quoting me for RFQ Chemical analysis. At +$300 I turned them down, but will re-contact them and ask about OES. If they still can't help me, I will take you up on your offer. Thanks!

 

I would be happy at knowing +/- 0.1 :D. Is it closer in spec to 1095-10100 or 1075. Quench speed and all.

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