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Please check out this explanation of the Ellingham Diagram from MIT.  

 

One thing I neglected to mention is that the Ellingham-Richards chart is all very dependent on exposure to free oxygen.  Inside a solid mass of metal you still rely on diffusion for things to move, then at the surface you have the opportunity for these reactions.  A liquid state allows much faster movement of elements to get to the surface.  From there you have to have free oxygen to reach the metal.  With induction melting we can keep this from happening with the SPAL process, where we drip liquid argon onto the liquid bath.  The argon expands greatly and displaces all oxygen, therefore no oxides!  The bigger reason this is often done is to keep the nitrogen out.  

 

Borax is sodium tetraborate decahydrate, Na2B4O7*10H2O, with the Na2B4O7 being the important bit.  Apply the principles of the chart above to the Na and B in borax and you will see that both like oxygen more than iron; or at least you would if they were on that chart.  But their reaction is definitely below iron, so they will preferentially strip the oxygen from iron oxide if the conditions are right (temperature and partial pressures).  This would also be true for lines above the iron line, but not necessarily any below the iron line, and keep in mind that the lines aren't all parallels to each other, so different things will be preferential in different conditions.  

 

BTW, there are also diagrams for things besides oxides, like sulfides.  Neat stuff.  

 

Carbon boils happen at a variety of temperatures, depending on the chemistry of the bath.  It generally happens when there is too much rust (iron oxide, and note that different forms of iron oxide have different lines on the chart) in the base charge so the reaction starts.  We stop the reaction by throwing a little ferrosilicon or aluminum in the bath to preferentially react with the oxygen.  No oxygen in the bath means the carbon isn't able to convert to CO.  

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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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That's just too cool, Jerrod!  Thanks for the explanation.  I'm stuck in the 19th century, science-wise, when it comes to smelting/remelting.  

 

And "Liquid Argon Drip" would be a great name for metal band...

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5 hours ago, Alan Longmire said:

And "Liquid Argon Drip" would be a great name for metal band...

Second that!:lol:

 

OK so no borax! Maybe that's what I was actually watching - not steel turning liquid but all the slag and extra borax leaking out. Still was really cool to see. Just wish I could have videoed it.

6 hours ago, Jerrod Miller said:

BTW, there are also diagrams for things besides oxides, like sulfides.  Neat stuff. 

VERY neat stuff. Again, second Alan's comment "That's just too cool".

I was wondering where Na and B fell on the graph. Do they fall above or below Cr?

 

This is a serious rabbit hole that I'm going to have to go down - but not tonight. Been up for 17 hours on 4 hours of sleep.

 

Thanks to you both for all the information.

 

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Na is way low on the graph, should be lower than Ca; very reactive stuff.  B looks to be just below and parallel to Mn.  Keep in mind though we aren't interested in just Na and B.  We have to consider a reaction/state that is lower energy than Na2B4O7.  So it is not going to be 4/3B+O2 = 2/3B2O3, We are going to be looking at something like Na2B4O7 + 1/2O2 = 2NaO + 2B2O3, or something along those lines, not too familiar with boron oxides.  At any rate that would be a completely different line.  It could even break down into something else that is some version of NaxByOz before dropping again to separate Na and B oxides.  And the difference between those energy states may mean that there is now something else in between.  

Ellingham diagram for oxides. | Download Scientific Diagram

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As the late Larry Harley once said to the late Al Pendray during a crucible smelt (direct reduction of ore in a sealed crucible), "It's more than just a bunch of fat old men watching a fire..." :lol:

 

I'm lucky to have been standing beside them at the time.

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1 hour ago, Alan Longmire said:

"It's more than just a bunch of fat old men watching a fire..."

Yeah, you can't forget the booze!

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I don't remember what flavor the 'shine was that year.  It wasn't strawberry, maybe that year it was plain?  Or blueberry...

 

But yes, booze was involved.

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Thanks Jerod

 

the MIT definition helps when explaining the graph is upside down. I keep wanting to add solid  carbon to the CO/CO2 ratios at those temperatures..I am not sure if that is the case or the numbers are just an actual measurement of added quantities.

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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.1_IMG_0218.jpg

It's made from cast-o-lite 3000 with a core (not shown) of inswool 2600. Molded spaces for the bricks to fit them nice and tight to make it easier to get the wire around without having to struggle. Worked so well I almost didn't need the wire. Used it today for its maiden voyage and it worked beautifully.

 

Had planned on 5 runs but due to mishaps with an experiment I tried, I only got four completed runs in. The experiment was to try and seed in a small amount of rice sized anthracite coal into the burn. Seemed to be going OK until I pulled the puck from the furnace. It was riddled with little bits of coal and broke apart when I hit it with a hammer. So the second run was actually running the material from the first run again - WITHOUT coal.

 

Starting material for the first three runs was grinder swarf packed tightly in 6 oz tomato paste cans. Was able to pack 150-200 grams of swarf in each can. Made the runs as 1 kg total loads. Yield was 571 g (no surprise with having to run it twice), 777 g and 726 g. The fourth run was the mild steel bar cut-offs from all my damascus billets. Total load was 1020 g and final yield was 941 g. There were good omens on my last run because as I was just starting the first charge I noticed two adult Bald Eagles flying over me. Was really cool. I wasn't able to get pictures of them, but my wife did.

 

Final pucks run order from top to bottom.

3_IMG_0226.jpg

 

All of them packed nice and tight when consolidated on the stump.

 

And the spark tests:

 

#1

5_IMG_0228.jpg

 

#2

6_IMG_0230.jpg

 

#3

7_IMG_0232.jpg

 

and #4

8_IMG_0236.jpg

 

The nicest part is these don't seem to be bi-polar this time. I don't know if it was a case of the base being so insulated it helped keep the heat in, or if it was because I had angled the tuyere at a bit steeper angle to keep more of the charcoal glowing -  or a combination of both. Regardless, I now have just over 3 kg of what appears to be (relatively speaking) homogeneous high carbon steel to work with.

 

Just have to wait for a relatively warm day to consolidate them.

 

Edited by Bill Schmalhofer
typo
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As I was digging through my stuff, I "found" the 3.5 Kg of "wrought iron" pucks that I had made when I was doing the demo at Conner Prairie. Had completely forgotten about this stuff. It was made chiefly of bottle caps and it didn't turn out very good (read high carbon - sparks as pure iron)) as I think we were using a poor set up (indestructible, heat impervious bricks that were a major heat sink - they were still hot after 3 hours of "cooling down"). But wrought does have its place in things. Needless to say, I have a LOT of consolidating to do...

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