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Oil fired crucible furnace

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MetalCaster:
VT-

I have been on a similar journey for the last few years with the iron thing.

I have had a lot of conversations with Ironman, and the general concensus between us is that there is a lot of misleading information on the internet about things in general and casting iron and other metals in particular.

I has been difficuilt for me to sort through what I am told with what I discover for myself, and what I assume to be educated guesses.

My approach has been to break down the problem into managable parts, and solve one problem at a time.

I had a lot of recommendations to use coke for fuel, and build a cupola, but after searching for weeks for coke, and living one state away from the motherload of coke mines, I found that the normal joe cannot buy coke in small quntities.

I looked at propane, propane and oxygen, charcoal, kerosene, etc.
I finally settled in on diesel as fuel since it burns cleanly, is readily available from a large number of sources, and is much cheaper than kerosene around here.

I had to figure out how to make an efficient burner, and ended up with a hybrid combination of several designs that were out there on the net.
The hybrid burner works very well.

I did a lot of research on crucibles to find one that would last for a long time.
A crucible should last between 50-100 melts minimum.

I researched alloys, melting temperatures, machinability, availability, costs, etc.

I looked at types of sand, water-based, oil-based, binders, resin-based, sodium silicate, etc.

And I did some castings, all with Petrobond so far.

So what do I do when things go south?
Break down the problem and isolate the problem to a single source, then solve that problem and reintroduce other variables slowly, one at at time.

My suggestsion for using sodium silicate-based moulds is to eliminate many/most of the variables, to find out if the problem is with the sand, or the metal you are using.
If you use a sodium silicate mould, and still have blowholes, then it is not the sand, it is the metal.

I start with clean metal of a known composition, again to eliminate variables and start with a known entitiy (clean gray Class 40 cast iron that is easily machined).

Your crucibles are apparently not rated for cast iron temps, or you are directing your burner straight onto your crucible or something.  You got a big problem there.
There are guys on Alloy Avenue who do cast iron every day on a commercial basis and get over 100 pours per crucible.  There is no reason why you can't buy the same crucible they have.  That is an easy problem to solve.

You could start with some clean cast iron of known composition, then see if you still have gassing, inclusions, etc.

I have seen too many people use one or more additives without even checking to see if they could pour successfully without an additive.
Again don't intorduce multiple variables into the problem at the same time, expecially if you don't even need them.

Your sprue and riser are very short, but if you are getting a decent mould fill, then sufficient pressure is being developed.
The idea behind the sprue/runner/gating/risering is to prevent air aspiration, trap lose sand, skim slag, create even pressure at every gate, control solidification, and preventing shrinkage.
An even and consistent pressure is desirable to fill the mould, and I have found that vents on the top of the mould are necessary to get rid of trapped air, and would almost certainly be critical with water-based sand to vent steam.  I have also seen many commercial guys vent the core through the center and all the way out the mould.

So while I don't have a lot of casting experience, I have done a large amount of research, and specifically I have paid close attention to the guys who are doing a lot of cast iron work. 
I would recommend a more systematic approach.
No doubt you can do as good or better iron work than anyone out there, but I personally don't like to take a more tortuous path than I already face.
I see nothing to be gained by rediscovering the mistakes that many others have already made, unless like someone already stated "the journey is more important to you than the destination".

tekfab:
Good Post MC   :thumbup:

Mike

NeoTech:
Well if you don't have the means to buy the things you need.. The trial and error process is the logic step to take. I enjoyed this thread because of the trial and error process of repeating tests and casts.

I dont personally agree with learning from others is always the best thing. Sometimes playing with fire and get burned is the best lesson for figuring something out and getting the experience from it as needed. (dont put the damn hand in the fire). And is especially true when you dont have the means to follow some step by step commercial procedure outlined in a book.

But i do as well tend to go my own way and do whatever i think will work after sorting out the basics - experience isnt learned its experienced..

Oh well, less pie throwing and more trials an tribulation. Somewhere on the road taken the answer will show it self.. =)

vtsteam:
Pat, I think I have seen the same information repeated enough to have it memorized by now. That's not my way. I look forward to reading your own casting project threads.  I do see great value to be gained by rediscovering the mistakes that many others have already made, and as Andrew already stated "the journey is more important than the destination". 

Change of subject. Here are photos of my F60 silica sand without any binder.

tekfab:
That's quite possibly the nicest F60 silica sand that i've ever seen.

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