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Dmitry.M

From ingot to the trash

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Aluminum melts at such a low temperature, it might have time to ‘alloy’ its way out, before the steel was completely liquid…but it sounds like it might be worth a try – the explosion would probably not be too severe, if there were one. :o:D

With a crucible of molten steel and slag, you have a bunch of chemical reactions seeking equilibrium, and you need not only chemistry but also thermodynamics to really know what is going on as the molten steel cools to solid. Since I studied neither of those, I won’t go into any discussion of the underlying chemistry, ‘cause I’d probably get things wrong.

Adding charcoal to the slag once the charge got to liquid has increased my forge-ability percentage, significantly. However, it also increased the number of ingots with holes and entrained slag, I think because I also shifted to shutting down more on the early side, so as not to risk re-oxidizing. I have to cook up a few dozen more ingots before all the aspects are clear. The cool thing about using carbon in the slag (if your slag is basic (more lime than silica), not sure if the technique can be used with an acid slag) to deoxidize the melt is the slag changes color as the steel deoxidizes, so you have a clear indication of when it’s ok to ramp down. Of course, if you want to check your slag color you have to be using an open crucible, or at least a hole in the top that you can get an iron rod through.

It does increase carbon in the steel, how much is probably highly dependent on the specifics of how the run is conducted & how hot the furnace gets. I saw a jump of roughly 0.3 – 0.5%, but that is an intuitive guess since I’m not trying to run the smelts the same way each time. It is based on lab analysis of three ingots made with reducing slag versus all the ingots I measured before.

The reducing slags used in industrial steel production early in the 1900s were usually based on lime, silica and fluorspar, with coke dust for carbon added with more lime once the melt was underway. High carbon melts were fluxed with lots of lime, as much as 10 parts lime to one part each sand and fluorspar, for melts in electric furnaces.

 

Hello All,

I have been poking a hole in the tpo of the inswool top and adding a quick jab of aluminum TIG rod for many years now....if you are quick you can shoot it all the way to the bottom of the crucible and feel resistance..then it is gone.

Not much is needed...industry uses two pounds per ton of steel.

Put it in, seal off the top again with some more inswool and shut the furnace down.

 

If it were not your low forging temp I would have suggested phosphorous as it can be an issue at higher forging temps..but you were too cool for that to be an issue.

 

Been sick for a week.....back to bed.

Ric

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Jan, I stopped using fireclay crucibles because I could see the bubbles coming through the slag while the thing was hot, and see them in the steel after I sectioned the ingot – starting on the sides and heading for the top, the steel perfectly quiet otherwise. The heat had not sealed the walls, but opened them up to let the gasses come pouring through, I was convinced. :(

 

Dmitry, the carbon-added flux might work just as well with acid slags, I just have experience with the neutral and basic varieties. The main issue to watch out for (aside from the slag eating your crucible) is the slag becoming too thick to do it’s job properly, you may have to add a thinning agent along with the carbon to keep things fluid. Consider using a neutral flux rather than strongly acid as well, you should not get much erosion with a balanced slag, and it might be easier to control fluidity.

With an acid system, you might want to try deoxidizing with ferrosilicon. I can send you a pound or two, if you can figure out how to get it into the steel at the end of the run. ;)

 

Your method sounds simple and effective, Ric - I like it.

Get well soon!

Edited by Jeff Pringle

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Wow!!!!

It was an eruption of ideas! GOOD ideas!!!!! B)

 

Jan, unfortunately I am not convinced that my crucible is really sealed with the heat. I use mullite-kaolin composition and it is so refractory that barely fires up. The pot after the melt is still not glassy ceramic. It is rather crunchy stuff like a dense cracker. And it is realy porous.

I have no idea how much gases escaped through the walls, but I am sure, that in this case there were no bubbles in the steel. I ground one ingot before forging form a side. It was solid. And I was pretty sure it was almost perfect all the way through.

But your suggestion that I may have too much slag sounds very reasonabe. And I will try to use a lot less of it. The only reason why I used A LOT of slag-flux was to seal the steel from the atmosphere as soon as possible. I thought that the main oxidation happens at the very beginning, when the steel is not completely covered with the molten slag. But it is hot enough to suck all avalable oxygen. I may have been wrong.

 

 

Greg! the main and HUGE difference between ancient smelters and us is - they used charcoal as a fuel. And that make the furnace atmosphere strictly redusing. It is rater hard to make it oxidizing in the charcoal furnace unless you run it without charcoal(lean). So there was no way to burn steel out. It was more possible to add some carbon to the steel I think.

 

Richard, that is the exellent tip. Thank you! I need to try this.

 

So for the next run i will at least reduce the anoount of the slag I add into the crucible. I also will try to make it a bit more liquid. Some borax should not be a bad idea.

Second, that I will try to do is the aluminum KILL-BILL-STEEL trick. I was thinking and realized that add aluminum at the very begining is not good anyway. Even if I will protect it with the steel shell. But if I'll make thin-wall steel tube with the aluminum filing, it might be heavy enough to get to the steel before aluminum will melt. Than I will kill the steel while the tube will melt aswell. I'll try something anyway.

If I understood digits well, they add 0.1% of aluminum by weight on the factory. So for the 1...1-1/2lb ingot i really need just a drop.

 

The only concern is I can not open the furnace lid on the run... too hot for me. So i need to run it without the cover on the crucible or make a pause in the melt. I would rather prefer to run crucible without the cover....

Edited by Dmitry.M

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could use a steel brake line... thats a long tube... and just crimp the end and add a little Al shaving in the tube...

 

i'd also crimp it just after the Al pill... don't want any gases to fly up that tube if the Al reacts violently

 

G

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could use a steel brake line... thats a long tube... and just crimp the end and add a little Al shaving in the tube...

 

i'd also crimp it just after the Al pill... don't want any gases to fly up that tube if the Al reacts violently

 

G

Is it pure steel? I don't whant to get some copper in the ingot. Even if it is stainless it will "contaminate" the ingot steel....

But I'll think how to make it, thanks!

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Is it pure steel? I don't whant to get some copper in the ingot. Even if it is stainless it will "contaminate" the ingot steel....

But I'll think how to make it, thanks!

 

Hello All,

There are many ways to intruduce the aluminum...but what form do you have it in? wire, lump, block, coin?

One concern is not to have any volitile substance on the alum or the method of delivery...no waer, not oil not nothing that will "explode" when in contact with the liquid steel.

 

Greg's packet idea works...industry uses thick paper bundles (cardboard tube) with alloys inside, or steel packets, or just large bits of the alloy....but more often then not they can make a hole through the slag and dross. Getting through this layer is the concern for us.

If all is full liquid then it is simple unless you hit the cover of the crucible.

 

You could drill out the center of a DRY wooden dowel and jam aluminum into it and then stick the wood into the mix and stir...the wood will burn and fall apart..or the same with a carbon rod. The carbon uptake will be minimal as this is done just before shutting the fire off. If you use something strong then you get the added benefit of making sure there are no solid un-melted bits inside.

 

Still sick,

Ric

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Wow!!!!

It was an eruption of ideas! GOOD ideas!!!!!

 

Yes, thanks for bringing this topic up again!

A discussion of backyard deoxidizing was somewhat less productive 3 years ago: Killing your Steel

I guess we ARE making inroads into that big blank spot on the technology map that is labeled ‘wootz’

;)

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Ok, it is showtime!

I made a melt on Sunday. It went pretty smooth.

First I need to describe the new crucible. I made it almost twice as big and with twice as thick walls. I add approximately 1/10 part of craphite in the clay mix. So the raw crucible was rater dark.

I let it dry for few days and than dried in the kitchen oven at 350F for 3 hours twice(two coonsequent nights).

The charge was very odd... I put in around 2 pounds of trashed ingots and broken billets and leftovers. Some class on the bottom, than steel and than more glass and borax. On the top of that I put a full teaspoon of graphite and few pieces of the natural charcoal. I wanted to kbnow if it would be a significant amount of oxygen under the crucible cover. Actually the crucible was so full that the cover was laying on the charcoal and it was 1/4" gap...

Anyway, after the crucible became orange-yellow hot the cover set down and closed the crucible.

 

Here is the crusible after the melt.

IMG_2939.JPG

Edited by Dmitry.M

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After I opened the cover and looked inside I was shocked a bit. It was ugly.

Take a look yourself:

IMG_2940.JPG

Edited by Dmitry.M

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I turned the cricible upside down and let all the trash out. Here is what we have there:

Few pieces of the charcoal, almost the same size as it went in.

Around a half of the craphite amount.

Few croocked ugly pieces that were the pieces if aluminum before. I have to mention that I tried to kill the steel with aluminum and added it under the cover WITHOUT pushing it deep. I'll expalin later.

IMG_2941.JPG

Edited by Dmitry.M

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Ok, let's see whats with the ingot. I broke the crucible. It was easy.

Well, not bad ... right? :rolleyes:

IMG_2942.JPG

Edited by Dmitry.M

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A little bit of my comments on that picture.

The stuff that covers the bottom of the crucible is whithish and glassy. It is far from the ugly black oxide that I had before. You can see how deep the craphite is gone from the crucible wall. And it has been burned from OUTSIDE. From inside it is still dark. But should I run the furnace a bit longer - it will be completely depleted. That's how the firnace burn out everything inside.

The crucible wall is a bit more that 1/2" Closer to 15mm (5/8"?) On the lid there is a dark center that liooks like a graphite, but it is not. This spot is covered with the molted slag and probably some iron oxide. The thickness of the cover is less than 1/2" and the craphite was depleted completely.

The slag layer is a bit thicker than 1/4" and it is rather dark. It has few droplets of steel or iron oxide in it. Along with the round spots and bubble tracks everything points at pretty active boiling.

I suppose that it was only top layer of the steel that really boiled. And I did not give it enought time to be completely "killed".

Here is the picture of the ingot.

You can see that the side is not covered with the black oxide. it is rather shiny. It is more dark on the very bottom. I checked it with the grinder, the black layer is extremely thin. it is pure solid steel under it.

You also can see that the upper "hat" is rather thin and not much extended to the sides.

IMG_2943.JPG

Edited by Dmitry.M

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Compare the shape of the ingot top with the old one, I had a lot of ingots like that before.

CA0003_2.jpg

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Ok, back to the last ingot.

Here is the picture of the top and the slag that corresponds to it. I did not break the slag, it broke like that by itself in the crucible while cooling down. You can see the bubbles and the slag color.

So far I think that it is the shrink in the middle and it might be combined with the bubbles. I can not forge this ingot as a whole, so I'll cut it. And will make a picture if there will be something interesting.

IMG_2944.JPG

Edited by Dmitry.M

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Hi Dmitry.

 

First....this topic is GREAT, thanks for showing it.

 

Sense i have done only 6 crucible steel runs i cant give any major guidens :lol:

But i have read lot´s of topic´s here and there....And have to say ingot of this last run of your looks nice, smooth and deffenetly did have that much shrinking. Tophat that is not.

I loved to see what kind of sructure the is in side.

 

Dmitry..if you dont mind some questins?

 

- Did you used lower temp or shorter melt time of you compare this run to old (pic) one whits had tophat?

- How long time is awarage melt time on your furnace / or how long you hold it in brite yellow / white collour?

- Was this top of ingot ...bad stuff anyways?

- " I suppose that it was only top layer of the steel that really boiled" is it steel that boils...or oxide, slag?

 

:huh: about aluminium..i allways thought that aluminium is BAD alloy ...and have i figure out it wrong if i say when aluminium used it get´s oxygen off the steel?

 

...if you want to ad aluminum way that it goes in slow....dould it be used in "sort of mineral" form...

Some time a go i find stones ( granate gemstone) and did some googleing on that....it contains Al...whits it´s formet in hi preasure and heat long time ago....but this is just my bit weard idea....Actially i was planing to ad one fingertip size rock in my 5 run but didnt...i was worried about this Al...

 

Anyways it´s so nice to see your melts...great work.

Can´t wait to see stucture !

 

Niko

Edited by Niko Hynninen

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Dmitry..if you dont mind some questins?

 

- Did you used lower temp or shorter melt time of you compare this run to old (pic) one whits had tophat?

- How long time is awarage melt time on your furnace / or how long you hold it in brite yellow / white collour?

- Was this top of ingot ...bad stuff anyways?

- " I suppose that it was only top layer of the steel that really boiled" is it steel that boils...or oxide, slag?

 

:huh: about aluminium..i allways thought that aluminium is BAD alloy ...and have i figure out it wrong if i say when aluminium used it get´s oxygen off the steel?

Niko

 

Hi Niko.

 

I did this run at a top temperature of my furnace. It was not the longest run, but not the shortest either. My furnace gets to the yellow-white temperature in about 40 minutes with big crucible inside. But it is what is visible. Inside the crucible I think it is colder at the beggining. The steel takes time to heat up, and it takes some heat energy to melt it. it is some kind of a energy step. ones you got the steel molten it will keep this additional energy untill the temperature drops. And during crystallization the steel ingot will emitt this excess of stored energy. It is very basic physics.

I think the top of the ingot is not good, and there are several reasons for that.

First, you are right about the boiling. I think that the stell on the top is saturated with oxide and has lower melting piont. So it is boiling. As I wrote before, should I keep the steel in molten condition longer, I might kill it completely and there would not be any boiling anymore.

But there is another bad thing about the top side of the ingot. If the crystallisation goes from the bottop up all contamination is pushed up-inside. In the tall and narrow ingot that would create the shrink channel in the middle. But in my shape and size it would rather make a "lens" or a "cone" on a top.

So for those reasons I do not count the hat as a good steel.

In rare casec, where you had very pure charge with wely low contamination and cooling was strictly from the bottom-to-the-top you might get a "coin" of this bad stuff wich would burn and scale out during the later forging. So you can use the whole ingot "as is"/

in current case I would try to cut the top off. It is nesessary for two reasons. First to discover what those bubbles are. Second - to cut the dirty steel out.

 

You can read about aluminum in this topic on frist two pages. It is used at the end of the melt for deoxydation reasons only.

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The latest update. I weighted the ingot. It is 938gramms(2lb+)

Edited by Dmitry.M

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do you think the Aluminum oxidized quickly and that is why it didn't melt and become part of charge? ...

 

with that extra graphite... i would be worried that it may boost the carbon past 2% ... and past that point, the ingot would be very very crumbly like cast iron...

 

however....it is very strange that the extra graphite didn't get taken in by the liquid steel.... unless it was at a saturation/solubility point.... I think I read somewhere that cast iron could take in about 7 to 8% carb.. ( or maybe i'm dead wrong ) .... but you should be no where even close to that point !... so the graphite musta become hung up on the side, and not touch the steel...

 

 

the ingot looks ok... surface looks ok... but that can all change when you forge it...

 

 

i think the hat on the ingot maybe cause by the errosion of the crucible walls by the glass flux... .. as the flux sits on the top of the steel, it'll bubble away and erode some of the side of the crucible..... the gouged out area is then filled in abit by the steel leaving a hat when its cooled.... .... it could be that the flux is getting tired or full of additives by the end of the charge... and this is getting stirred into the surface of some ingots... ?? that could definitely give problems..

 

 

Dmitry... those are excellent pictures... fantastic looking crucibles..!

 

we are all learning a good deal from this post... wonderful

 

Greg ;)

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Thank you Greg!

 

I added aluminum on a top of the slag at the end of the melt. The main idea was to look at the aluminum behaviour. It partialy oxidized, but I feel that it happend when I was pushing it through the flames into the crucible. It remained molten and liquid inside the crusible long time. So I can conclude that inside the crucible where several pieces of the charcoal exist it is not much of an oxygen... However it did not sink, though the slag was really liquid, not as viscous as it use to be. And still aluminum floated.

The main goal was to check if just carbon on a top of a slag will kill the steel. And i think it did. And more important it did not saturate the steel with too much carbon.

You are right, everything might change under the hammer.

 

So far I cut the top "hat" off. I used the lathe. if you would do the same use carbide incerts only. No HSS will stand against the ingot.

As I expected the very middle was bad, crumbly. it did not produce nice and continious shaving. More like a dust at the beggining and not as good as on the side after I took a 1/4" hat off. The middle is still not viscous as the steel should be. It might be not because of the contamination anymore, but more because of the ingot crystallic structure. Will se later.

 

The brief etch with the 5% nitric acid in water showed very fine fields of hair-thin dendrites. The sized of those fields vary from 1/2" X1/2" and less. Directions are random. I do not have a camera at a moment, will try to make a picture later.

But what it showes is the very defined dendrite pattern, wich means there is not too much of carbon in the steel. AFAIK the cast iron has a grainy structure without the dendrites.

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I frogot to mention that the "bubbles" were at the very top of the ingot and NOTHING was found deeper that 1/8" from the top. So there was no bubblin-boiling deeper or all gases escaped before solidification.

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Your comments genlemen... :ph34r:

 

 

Dmitry,

 

I am very impressed with your crucible making skills. The fire danger in the West is so high right now all I am doing is cleaning, clearing and hauling fuel away from the place. Soon I will be inside the shop again.

Good luck with this ingot, I am anxious to see the drama unfold.

 

Jan

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Tried to forge yesterday.... a lot of ringing and not much of the shape changing. Ingot is stiff, very stiff. Left it for annealing.

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Hi Dmitry, can I ask how and what you made your crucibles from?

 

Cheers

 

John

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Hi Dmitry, can I ask how and what you made your crucibles from?

Hi John.

I made few with different shapes and sizes. The last one is made of 4" vinyl (PVC?)sanitary pipe. The inside piece is wood. I put four 2X2" together with epoxy and turned them. It is just because I did not have big enough piece of wood. Otherwise - you can turn it from steel, plastic or anything else. So I put the piece of pipe and an internal piece in it and layer by layer put the clay mix there. And pack it with the wooden stick. That's how i control the density. Too tight and it will crack in the firnace. Too loose and it will leak. Tricky.

mold1.jpg

mold2.jpg

Edited by Dmitry.M

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