Crucible Steel - The Rabbit Hole Entrance

[AJ Prime]

This weekend, a friend and I attempted to produce crucible steel for the first time. It's something we've both been keen to try for a while so a couple weeks back we decided we'd put a plan together.

 

We were confident we could build the foundry but I wasn't sure my forge burner would be able to produce the heat required. We both have the same burner and they're sort of modular and could be easily transferred from a forge to a foundry so we figured why not use two burners and see how that goes.

 

We set out expectations at a realistic level and decided that this attempt would be to see if we could even melt steel.

 

We filled our crucible with cast iron (donated from resurfaced brake rotors) and small pieces of mild steel to bring the iron ratio up. The cast iron content was an unknown but we worked on the assumption of 2% carbon, aiming for a final level of 1.3%, though it could end up higher. Total mass was 600g.

Green glass was put on top.

 

Once it went in we were both surprised how quickly the glass melted. The crucible stayed in the foundry for a little over an hour before we killed the fuel supply and dropped in a little Aluminium. We left it sitting in the foundry for a few more minutes the took it out to cool.

 

An hour later the glass was cracked open and little puck fell out. It looked a little porous too it untrained eyes but we were still really happy we had seemingly pulled it off. High-fives were had.

I cut it in half to reveal what looked like a mostly solid puck but a quick polish and etch revealed that there were a couple pieces of unmelted mild steel in the bottom. 

Despite that we were pretty pleased with ourselves. So we attempted melt number two. This didn't go nearly as well.

 

Melt #2 was 900g of small bits from oroshigane smelts. After 80-minutes only the glass had melted.

Here's what I think happened:

The first run had depleted our gas bottles somewhat so at the second run our 9kg gas bottles were low and quickly freezing, dropping gas pressure and heat. Essentially we just weren't as hot the second time around. That, and powdered cast iron probably melts a lot easier than chunks of carbon steel.

 

So in the end we determined we need a hotter fire source. LPG is expensive and will always have the freezing issue so well be exploring a waste oil burner for future attempts. When we've established a system that will reliably melt steel we'll begin looking closer at our recipes.

 

All in all, we're pretty happy with the mornings work. 

All feedback welcome 

 

A.J. Prime 

*Edit* Photo seem to have published in the wrong order

 

Edited June 28, 2020 by AJ Prime

[Garry Keown]

On the gas supply problem AJ, the solution is to get one of the manifolds from Gameco so you can run two bottles together through the same regulator so if you had one with two bottles and yoiur friend did for his two bottles the freezing aspect would most likely dissapear. They are just $58 + gst each and are a simple fix for the feezing. I got one for both my forges and wouldn't dream of going back to a single bottle supply.

[AJ Prime]

5 hours ago, Garry Keown said:

On the gas supply problem AJ, the solution is to get one of the manifolds from Gameco so you can run two bottles together through the same regulator so if you had one with two bottles and yoiur friend did for his two bottles the freezing aspect would most likely dissapear. They are just $58 + gst each and are a simple fix for the feezing. I got one for both my forges and wouldn't dream of going back to a single bottle supply.

 

Each burner was on a separate bottle

[Alan Longmire]

LPG is easily able to get and hold temperatures for a cruxible furnace IF you use a blown burner. Venturis like that have the very issue you ran in to. With a blower freezing is no longer a problem.  An oil burner is fine too, of course, and adds another level of niftiness.

Congrats on the first semi-success!  You need to stir the melt, or at least probe it to ensure everything is liquid.  A carbon rod is ideal, but mild steel will work as long as you don't leave it in too long.  You'll need a foundry glove and face shield, and don't turn the gas down. Just lean over, poke around gently, and stir gently. Any glass you drag in will float back up.

[Daniel Cauble]

Just looking at the crucible in the 2nd pic I would say it didnt get nearly hot enough. Good job. If it were easy everyone would do it

[Garry Keown]

13 hours ago, AJ Prime said:

 

Each burner was on a separate bottle

Yes that is the problem AJ. You had just the two bottles with one for each burner. With  two bottles on the one manifold through one regulator and on one burner you are doubling the ammount of gas that is available to the regulator so as the bottles "freeze" there is still enough gas from each bottle to give a full pressure to the regulator. Then you have the same set up for the other burner.

For the two burners you have four bottles. 

I have 2 9kg bottles to the one burner in my small forge and when the other manifold arrives I will have 2 18kg bottles for my larger (3 burner) forge. Gas freezing will be a thing of the past for me.

Edited June 28, 2020 by Garry Keown

[AJ Prime]

8 hours ago, Alan Longmire said:

 

Congrats on the first semi-success!  You need to stir the melt, or at least probe it to ensure everything is liquid.  

Thank you! I gave it a prod and stir every now. I think what happened was I pushed that un-melted piece flat to the bottom so when I went prodding at the end I thought I was hitting the bottom of the crucible.
Can you explain what you mean by a carbon rod?

[AJ Prime]

7 hours ago, Daniel Cauble said:

Just looking at the crucible in the 2nd pic I would say it didnt get nearly hot enough. Good job. If it were easy everyone would do it

I know right, imagine my disappointment. I was envisaging pulling out a puck of steel made from steel I made. It just looked like the top of a very hot lasagna.
I'm hoping I can just remelt it once I figure my heating source out properly

Edited June 28, 2020 by AJ Prime

[AJ Prime]

34 minutes ago, Garry Keown said:

With  two bottles on the one manifold through one regulator and on one burner you are doubling the ammount of gas that is available to the regulator so as the bottles "freeze" there is still enough gas from each bottle to give a full pressure to the regulator.

I might explore that option Garry. Might give Corin a bell too

[Alan Longmire]

9 minutes ago, AJ Prime said:

Can you explain what you mean by a carbon rod?

 

These things: http://www.graphimaterials.com/graphite-rods.html, go for the JC3s.

They're expensive, but they're good to 3200 C and they won't contaminate the melt.

[AJ Prime]

@Daniel Cauble, I've been following your oroshigane exploits which I find very interesting (it's another rabbit hole I'm slowly tumbling down). Do you use charcoal for your crucibles melts too?

 

13 minutes ago, Alan Longmire said:

 

These things: http://www.graphimaterials.com/graphite-rods.html, go for the JC3s.

They're expensive, but they're good to 3200 C and they won't contaminate the melt.

Thanks you Sir

Edited June 28, 2020 by AJ Prime

[Daniel Cauble]

35 minutes ago, AJ Prime said:

@Daniel Cauble, I've been following your oroshigane exploits which I find very interesting (it's another rabbit hole I'm slowly tumbling down). Do you use charcoal for your crucibles melts too?

 

Thanks you Sir

 

Nope, blown propane for crucible. 

 

Oroshigane or hearth steel has been one of the things that keeps me coming back. The range of product I can produce in a relatively simple furnace is invaluable to me.

 

As far as I know, I've been the only one that sees the ease of using oroshigane as the feed material in crucible steel. To me it's a no brainer. I'm glad to read you are using it the same way.

 

Little to no slag to deal with in the melt vs using bloomery and something I can make in my backyard in an hour.

[AJ Prime]

8 minutes ago, Daniel Cauble said:

 

Nope, blown propane for crucible. 

 

Oroshigane or hearth steel has been one of the things that keeps me coming back. The range of product I can produce in a relatively simple furnace is invaluable to me.

 

As far as I know, I've been the only one that sees the ease of using oroshigane as the feed material in crucible steel. To me it's a no brainer. I'm glad to read you are using it the same way.

 

Little to no slag to deal with in the melt vs using bloomery and something I can make in my backyard in an hour.

That's validating to hear. I've had a few people say they think the oroshigane will be too dirty but I've found it comes out of the smelt really quite clean, and I assume putting it in a crucible will only purify it more. I'm using the pieces that were too small to mess around forge welding, so it's as good a use as any for it.

[Daniel Cauble]

23 minutes ago, AJ Prime said:

That's validating to hear. I've had a few people say they think the oroshigane will be too dirty but I've found it comes out of the smelt really quite clean, and I assume putting it in a crucible will only purify it more. I'm using the pieces that were too small to mess around forge welding, so it's as good a use as any for it.

 

People use dirty wrought and cast iron as their ingredients. The ancients used bloomery. Oroshigane is cleaner than both in regards to slag. It can also be made to have lower amounts of P than the other two.

 

It's been my main feed material for the past 12 crucible runs. 

[Daniel Cauble]

I can make a chunk or hearth steel and break it up all by itself and add to a crucible, and plop out a puck of ~1.6% crucible steel at will at this point.

[AJ Prime]

22 minutes ago, Daniel Cauble said:

I can make a chunk or hearth steel and break it up all by itself and add to a crucible, and plop out a puck of ~1.6% crucible steel at will at this point.

#goals

[Richard Furrer]

Dan, I am surprised that you can get a regular carbon content via Hearth.

 

[Daniel Cauble]

1 hour ago, Richard Furrer said:

Dan, I am surprised that you can get a regular carbon content via Hearth.

 

I mean it may vary a little bit, but I think I'm in like...10 of the past 12 melts using hearth steel only and yielding between 1.3 and 2%. Once I may have hit 1.3, but the rest have fallen in this 1.6% average area.

 

Then in the recent past I was approached by an archaologist that specializes in ancient metals. The structures I was finding in my steel and showing in micrographs were present in the exact same way as the UHC and cast steel chunks they were finding in Roman slag pits. Interestingly, of the chunks that were in the steel range, their carbon content was also in this 1.6% range. I suspect there is a golden ratio of settings that make chunks of steel with average carbon contents in these ranges if it's all combined.

 

I have been a strong advocate of the hearth and have strived pretty hard to consistently make a UHC product. After toying with certain attributes of the furnace itself, the running of the furnace, everything...changing one thing at a time and comparing what really works and what doesnt...I've just grow a pretty comfortable hand with my way of doing it.

 

In the end the hearth chunk is made up of zones of varying carbon concentrations. If you can maintain a high average, you can take that chunk and remelt it by itself in the crucible.

 

This last run I did things a bit different. Normally the only ferrous feed material I use is derived from the hearth. This time, I didnt have solid chunks of hearth steel on hand to do it that way. Instead I had white and gray cast that was indeed made in the hearth. When I make steel in these ranges, I often get a tentacle or two of about a half pound of white or gray cast that bleeds away from the initial chunk of steel. I suspect conditions are usually perfect at some point in time to maintain a liquid state longer than normal, resulting in liquid steel traveling horizontally across the hearth floor among the charcoal and enriching to the point of cast. I usually break these nodes off the main chunk because they are typically pure cast with no chance of being forgeable (the white cast in the main chunk of hearth steel is forgeable for me because I suspect the lower carbon forgeable steel welded to it gives it the ductility it needs to move ala, forge). So I take this cast and hold onto it to dope crucibles with if I think they need more carbon.

 

Well I needed a puck and happened to have 2 pounds of these cast nodes ranging from white cast 2.1% C, to gray cast, past 3%. Maybe some bits of steel in the mix, but overall cast. With it I added a chunk of crucible steel I made in the past that crossed into the 2.2% range. Then I really wanted around .005% V and added W2 to the melt to bring the carbon level down and add my Vanadium. 

 

But yea, I usually just break a chunk of hearth steel I to pieces, add glass and melt. Way too many melts resulting in the ~1.6, 1.7% range to call it coincidence at this point.

 

Sorry for the hijack.

Edited June 29, 2020 by Daniel Cauble

[AJ Prime]

30 minutes ago, Daniel Cauble said:

Sorry for the hijack.

Not at all

[Daniel Cauble]

Wrong guy, I mispoke. I contacted that particular archaeologist because I noticed a very high similarity in materials. I then found out he has been following my work already for awhile, so that was reassuring.

 

I was approached by a metallographer to take micros of one of my pucks awhile back.

 

Which reminds me that I need to send that.

[Tim Mitchell]

Good Job on your first attempt AJ.  It was a good test for seeing if you can get hot enough. For now though I suggest you make a basic blown burner and make sure you put a lid on that crucible.. having an open crucible will add several extra failure points and that is something that you want to avoid.  Just stick a section of brick on it to keep the atmosphere away so you don't get too much porosity in your ingot..

 

Second thing... only use known ingredients especially when starting out. Using ingredients with unknown elemental composition is inviting Murphy to the party.. the source of cast iron, grey cast iron brake rotors has between 2 and 4% Carbon and it is high in Silicone which makes graphite form in the ingot (the grey in grey cast iron).  Also adding Aluminium to "kill" the ingot is something that unfortunately Al and John did in their paper but it is a bad idea also.  You need to keep Aluminium far from your ingots, it will also aid in forcing carbon out as graphite in your ingot.  Graphite is your enemy when forging ingots, it makes them brittle and they will crumble under the hammer. There are ways to avoid disaster when forging ingots which contain graphite forming ingredients but they are not something that a beginning smith would be able to do easily, it is like dancing on a knife edge....