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Oil fired crucible furnace

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dsquire:

--- Quote from: MetalCaster on July 19, 2013, 02:45:09 PM ---You have seen my work, nothing new to show there.

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MetalCaster

I have checked all of your previous posts and can find no pictures of your work. It would be nice to see your work as you sound like you have a lot of skill and experience.  :)


Perhaps you could go to http://madmodder.net/index.php/board,3.0.html and make an introductry post to help the members get to know you.  :D


Cheers  :beer:

Don

tekfab:
I'm guessing he was here previously under a different guise ?

Mike

vtsteam:

--- Quote from: doubleboost on July 19, 2013, 04:53:04 PM ---
--- Quote from: awemawson on July 16, 2013, 02:27:15 AM ---Steve

I used to sprinkle something on the plinth brick to stop it sticking to the crucible but for the life of me I cannot remember what. Can't have been sand as that would fuse at those temperatures

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Beer mats work well
John

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Damn, I should have saved up back when I remembered where they came from!

vtsteam:
Today I increased the size of the exhaust port in the furnace lid to 4". Don't know if that will help or hinder melting. I think it will probably allow more air through, by reducing back pressure, which means I can open the fuel up all the way.

I couldn't do that before without the furnace smoking. The main reason I did it though, was to allow dropping additional metal more easily into the crucible, and also observing the melt.

I also tried out making some cores using Ironman's Portland cement and sand mix method. I used 1" PVC pipe as the core boxes. I slit them ahead of time. I used a very fine grade of sand I had on hand.

I was worried they would dry out before curing (in 3 days) so I put them inside a ziplock plastic bag, and also put a crumpled up wet paper towel in with them. Since humidity would then be 100% inside the bag, I didn't see any reason not put the whole thing out in the sun -- since that would speed up cure. Concrete blocks are rapid cured when cast by exposure to steam, so I though this might work in a similar way.

It's been very hot here the last week, but sunny at last. Temperatures have been up in the mid 90's F (34 C). So I'm sure the temperature was high in that bag today. Condensation showed the humidity was in there. I'll probably still go 3 days and then dry the cores as well after. But this was just an expeiment.

ironman:
vtsteam

What you can do is before you add water to your sand is weigh the sand dry and then put in 4% water. For future mixes you may have to adjust the moisture level. For thick castings ram the sand more gently so it has more porosity.

 I see that you noticed I don't put in vents in the middle of the core. When molten iron touches the core/mold surface gases have to travel through the sand to reach the vent. If the sand has no porosity it will bubble through the metal. It will always take the path of lest resistance. Can you see why I don't bother with vents?

It is extremely rare for me to get blowholes in my castings so I must be doing something right. Have a look at my video " How to change steel to cast iron using a waste oil furnace" to see how I solved the shrinkage problem on the pulley casting. You will notice how shallow the copes are on my molds.

Just increasing the head pressure will not fix the shrinkage problem, making large enough risers so they will freeze last instead of the casting feeding the riser. 

When I saw the photo of how distorted your crucible was it would have been scary to lift out the crucible. Years ago I used to ask the foundry supplier is the crucible rated for iron? His answer was the crucible was rated for 1400C. Since then I never ask if the crucible is rated for iron and use them for iron. I have used a lot of crucibles over the years and never had one deform like yours.

 I have seen photos in other forums of crucibles with bad faults and are unusable after two melts. It is sad to say but I have come to the conclusion that the U.S.A. makes really bad crucibles. The ones I use are imported from Mexico, India, scotland and Brazil and never had a problem with them. I find some brands will last longer than others.

I have destroyed two crucibles through misuse, so making mistakes is part of the learning process. I never use flux with cast iron. Soda ash is the second worst flux to use in a crucible, the worst is borax. They will dissolve your crucible very quickly. If you insist on use fluxes your crucible, it will have a very short life.

vtsteam as a beginner there is no way your furnace will reach 1650C (3000F) I have a pyrometer that will measure to 1770C (3218) and in a typical iron melt the furnace is struggling to get over 1570C (2858F). I have never used a silicon carbide crucible for iron. I was hoping someone would buy one and see how much longer they last compared to a clay graphite crucible.

 Over the years many hobbicasters have visited my home foundry and everyone has said I do everything differently from what is written in books or the way they think it should be done. But when they leave I find out a few weeks later they have copied nearly every method I use. 

Metalcaster welcome to the forum. I'm sure everyone would like to know what sort of casting you have done.

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