Flux question.

Home enthusiasts discuss their Foundry & Casting work.

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DavidF
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Joined: Wed May 14, 2014 12:28 pm
Location: Delaware

Re: Flux question.

Post by DavidF »

Only 10 melts? I get between 35-40 melts. I would never use budget crucibles they are really badly made.
And thats high temp melts? IE silicon bronze and iron?? Thats impressive!! Mine get pretty thin after 10 melts. I might be able to get a few more out of them, but wouldnt want to take the chance. Whose crucibles are you using? Im due to order up some more.
The kaowool lasts for about 25 iron melts. I get a lot of kaowool given to me so cost is not a problem so why should I use anything else.
If your happy thats all that matters. I think my next furnace ill build with a bore to fit an A8 or A10 with a 1" thick refractory cement hot face backed by the kaowool maybe 2" thick. My small furnace with the A6 is just a little small for some of the stuff I cast, and the big furnace is a fuel pig that takes forever to heat up and just too big. So I need something in the middle, maybe 8" bore? Ill have too look at crucible sizes and figure it out.

How about a couple of pictures of your furnace??
BillS
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Joined: Fri Jul 11, 2014 1:44 am

Re: Flux question.

Post by BillS »

I use vesuvious crucibles for iron only. Morganite crucibles are not very good for iron. I will have to figure out how to post photos.

Bill
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Harold_V
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Re: Flux question.

Post by Harold_V »

BillS wrote: I will have to figure out how to post photos.
Very easy, Bill.

If you host your pictures away from your computer, all you need to is provide a link to the stored picture(s).

If you store them on your computer, or other medium, they must be uploaded to the Chaski board. Make sure they're not overly large in file size (less than 1 mb is very desirable), and they must NOT be larger than 1024 pixels in width or height, otherwise the software will reject the upload.

That being said, when you're composing your post, you're already on the proper page to include a photo or more, which are posted as attachments on this board. Look below the box in which you enter text. You'll see a broad blue line (I'm assuming you use subsilver2 as your board choice. It's the default selection) which has written within it Upload attachments, in orange text. Below that line you'll see a box that says Browse. Click that box, and that will permit you to go to the folder where you keep our pictures. Select the one you wish to post and follow the instructions. Once you'd done it you'll see how easy it is.

Be mindful that you can place pictures in line. Place your cursor where you wish a given picture to go, then select that picture from the list of pictures you've uploaded for that given post. It isn't necessary to place them in line, however. If you upload without doing so, they will appear at the bottom of the post, with the first one in the last one displayed.

Hope this helps.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
BillS
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Joined: Fri Jul 11, 2014 1:44 am

Re: Flux question.

Post by BillS »

Here are a couple of photos of the furnace.
Attachments
furnace.JPG
furnace lid.JPG
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steamin10
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Location: NW Indiana. Close to Lake Michigan S. tip

Re: Flux question.

Post by steamin10 »

Not to tell you how to run your furnace, but your lining melting is a result of overheating and turning it to glass. While this is part of the process, you can reduce this a bit by stepping your heat cycle, that is increasing your firing rate from preheat, to midrange, and then full on, for final temp and pour. This reduces the high heat time that the lining and crucible must endure, and saves some erosion. The idea is your heat will only absorb so much heat at whatever level exposed to, and in theory, a smaller gradient will help things live longer. I have found that vessel lips burn away the most, and the slag line next. So some used vessels become rim thin very early on. By preheating the vessel, adding the charge and then bringing the furnace up in steps some 5 to 8 minutes apart does not change the run time much, but shortens the max heat time.

Think about it, it is food for thought.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.
BillS
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Joined: Fri Jul 11, 2014 1:44 am

Re: Flux question.

Post by BillS »

Harold

My friend had another go at melting gold, this time he used far less borax and the result was the same, the flux was very thick and did not pour into the ingot mold. The second melt he used the same amount of borax but just before pulling the crucible out he added some more borax to thin out what was in the crucible, this time the flux was very fluid and came out to cover the gold in the ingot mold. Problem solved!

steamin10

The glassy areas on the furnace wall are caused by increasing the blast towards the end of the melt and a low pressure area forms over over the top of the crucible. It lifts the molten iron oxide slag out of the crucible and lands on the furnace walls and lid. The furnace lining is made from kaowool so when the slag drops on the kaowool it dissolves and a hole is the result. It can be quickly patched up pushing more kaowool in the hole and painting zircon paint over the patch.

BillS
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steamin10
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Re: Flux question.

Post by steamin10 »

Thanks for the note. My furnii are hard bricked with acid type brick for ladles. One unit with too large a bore has used kiln brick that was salvaged from a clay tile manufacturer.

Thanks clarifying the material.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.
HDB
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Location: Europe

Re: Flux question.

Post by HDB »

I recognize the damage done to the line. Same damage often can be seen on the aluminium oxide bricks. I use 1400°C kaowool / bricks and had the exact same thing while using borax for forge welding. Overheating the forge can cause damage to the insulation, but the grey fused insulation is from borax.

As mentioned before, there are sprays/coatings you can apply to the insulation that give it a glassy feel and protects the insulation from direct flame and fluxed such as borax.
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