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Jwindle

Trouble shooting

5 posts in this topic

Hi there!

 I'm a Newbie to crucible steel and to this Wonderful wealth of information! 

I fired a batch of magnetite sand and charcoal and got an interesting puck. It seems very brittle and porous, so I'm wondering if its more closer to cast iron? I also wonder if I need more heat? It was fired in a foundry using a burner I have used for pattern welding for a period of 3.5 hours with an overnight slow cool.

Would heating to a welding temp and attempting to weld be a good idea?

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I have had that same experience with magnetite sand, and no, at this point it won't weld.  It's just sintered magnetite now, which means either not enough heat, not long enough at heat, and/or the conditions in the crucible were not reducing enough.

What are your variables?  Lid or not, flux or not, ratio of ore to charcoal, etc.  Direct reduction in a crucible is tricky, for every success I have had there have been five or six failures.  One of those looked a lot like your puck, and turned out to have been underfluxed.  The one following was overfluxed and nothing but slag...:wacko:

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Good morning!

 I sifted 11 oz. Of magnetite and mixed it with .2 oz of powdered charcoal and mixed both very together before putting them in the crucible. My train of thought was that the carbon added should be just the percentage of the desired carbon content. Perhaps my math was off too, I have been known for that!

I didn't use flux, kinda an ah,ha! moment there when you mentioned it!

I sealed it with glass and cut out a piece of kaowool placed that in the mouth of the crucible and sealed everything with refractory cement and fired once it was hard. I fired it for about 3.5 hours and let it cool overnight in the foundry. ( Just shut it off and let it sit)

I was using a foundry I had previously used to cast aluminum and brass for knife bolsters and was wondering if perhaps remnants of brass may have something to do with it?

 Also its a Venturi burner, maybe not enough heat?  I was pondering a switch to forced air/ propane might be better anyway.

Thanks!!

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Aha indeed!

1. Glass acts as a flux as well as a sealer.  Do use it in a wootz melt starting from cast iron and wrought, do not for direct reduction.  In the event you need flux (and you might, magnetite is a bitch to reduce) use lime. Oystershell is great.

2. One metal per crucible, no reusing for different metals.

3. While a venturi burner is theoretically possible for this, in reality they are not good enough.  You need a blown burner.  A big one. And a reducing atmosphere helps.

4. WAY off on the math for the charcoal.  It is there not only to add carbon to the iron, it is there primarily to produce the CO for the reduction to take place. If you figure the magnetic sand to be pure Fe3O4 (which it isn't, there is always other crap in there) you know you need at least four carbon atoms per oxygen in the magnetite. That's where it gets tricky, because nobody knows how to figure out the exact math, especially if you're running a reducing atmosphere in the furnace.  Adding about twice the final desired carbon percentage by weight seems to work sometimes.  Especially if you're using wool for a lid, it is porous enough you will lose a good bit of gas from the crucible.  For an 11 ounce ore charge I'd have run with about three ounces of charcoal.

5. Wool for the lid is not a good idea for other reasons.  If you're running hot and the wool sags enough to touch the charge in the crucible, it will melt into it, resulting in a nasty foamy black glass with no apparent iron visible. Kinda like what you have there, actually...

So, and please remember I am no expert on this and have had little success at it (which means I can tell you what won't work, not so much what will), new clean crucible, hard lid if you use one, a lot more charcoal, no glass, maybe a bit of lime, chalk, or other form of calcium carbonate, but not a whole lot.

Good luck and keep trying!  Hopefully someone who has had better success will chime in.  Tai Goo got pretty good at it.

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Thank you so much!

I'm excited to get back out there! I finished building a forced air burner. That actually makes a lot of sense I poked a hole directly to the bottom to see if it was melted, probably dragged a lot of garbage into the charge. I will definitely be trying a few things this coming weekend, can't wait to give it a go!

 Also! The oyster shells reminded me of a article I had read that shellfish actually contain higher levels of vanadium. That triggered a thought that potentially trace minerals could be introduced by other ingredients tossed in. Potentially a carbon source high in chromium or other trace elements.  I wonder if supplements even? I don't know how they have been altered for the body, though.

Sorry, got sidetracked on a rabbit trail.

 But thank you, I appreciate your help and time! I will be sure to share on the forum as I play around!

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