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Casting Gray Iron

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Casting Iron:
I ran across a website in 2011 about someone who built an oil burner, furnace, and melted the broken parts of an old cast iron stove.
This was the first time I realized that gray iron could be melted in anything other than a cupola.

I built a furnace and oil burner, and while I had some initial success with casting iron, I could not consistently do it, and the Petrobond sand I was using was causing some defects.  I had no concept of how to tune an oil burner, and no idea of what fuel flow rate to use.

I ran across some local art-iron folks who make sculptures and such in iron using a cupola, and they introduced me to resin-bound sand, which is specifically designed to work very well with iron and steel castings.
The resin-bound sand has been a game changer to say the least, and if the runner(s) and gating are correct, this sand basically eliminates casting defects.

A buddy of mine built a furnace after I did, and he was regularly melting iron with it.
I was able to watch him at the Soule engine show, and learned a lot about handling the iron as it was melting, and handling the slag as it was produced.

I made a test stand with multiple valves, so I could quickly test my oil burner at various flow rates, such as 1,2,3,4,5,6,7,8,9 and 10 gallons per hour.
As it turned out, for my furnace dimensions, about 2.7 gallons per hour produced the hottest furnace interior.
I also learned that operating the burner reducing (rich) minimized the slag produced on top the iron.
Initially I though an oxidizing (lean) burn would work better, but that produced excessive slag.

Then I had to learn about ferrosilicon, and why it was needed (to eliminate hard spots in thin sections of iron).
And I had to learn the exact amount of ferrosilicon to use.  Too much caused excessive shrinkage and hot tears.
A very slight amount of ferrosilicon is required.

My first furnace was very heavy, and used dense cast refractory, so it took a long time to heat up.
I built a second furnace with a fraction of the mass.
First furnace had about 300 lbs of dense refractory; second furnace had 70 lbs of dense refractory.
The second furnace allowed me to reach pour temperature with gray iron in about 60 minutes, with a #10 crucible.

And I had to figure out which crucible worked with iron, and turned out to be a Morgan Salamander Super clay graphite crucible, which I use exclusively now.
This crucible is one of the few crucibles that is actually ferrous-metal rated, and rated for iron temperatures (about 2,900 F rated continuous).

Then I had to learn about sprues, runners, gates, risers, etc.
I have adopted modified methods that are from John Campbell's book "10 Rules for Good Castings".
There is a bit of an art to this, but basically you want to eliminate air aspiration, turbulence, high flow velocity, and irregular shrinkage/solidification.

Then I discovered spray-on ceramic mold coat, and that totally stops sand burn-on, and gives a smooth shiny finish right out of the mold, with no cleanup required.

It required quite a bit of sluthing to figure it all out.

At this point I can melt and cast gray iron with not much more difficulty than casting aluminum, and can create commercial-grade iron castings.
Gray iron melts are very hot, and the radiant heat is significant, so shaded goggles are required to avoid IR to the eyes, and full leathers are required.
And heat shields are required on the handles of the pouring shank, etc.

I prefer gray iron engine parts to any other metal, give the wear characteristics, and ease of machining/drilling/tapping, etc.

This year's challenge is to make dutile iron, and I have found some material to use for that.
Ductile iron used a secondary mixing chamber, where the reaction with a magnesium alloy takes place, and I think I have figured out how to build the secondary chamber.
The idea is to cast crankshafts in ductile iron.

Its a fun hobby, and really adds a lot to the engine building process in my opinion.

Casting Iron:
Examples of resin-bound sand molds.

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ddmckee54:
Is any of the resin bound sand recoverable, or is it all one-use-only?  If it's one-use-only how do you dispose of it?

Don

Casting Iron:
Resin-bound sand is not easily reused; there is some sort of recovery process in commercial foundries, and I think it involves burning off the resin.

I don't recycle mine.
It is considered a hobby discard, similar or even the same as many materials used in pottery.
Residential is allowed to discard X pounds of it each month, I forget the exact amount, but not a huge amount.

I think it is about like discarding epoxy material, or perhaps bondo-like material.

And once the resin is set, it is like plastic, and so it is relatively stable for a long time; not like a liquid that will leach out.

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Edit:
One thing to remember is that bound sand molds are very strong, and so they do not need to be very thick.
Some of my molds are only 3/4" thick, or less than that in some spots.
And I often block out the interior of my flask around the pattern, to shape-form the bound mold around the pattern, and save a lot of bound sand.

Generally speaking, a bound sand mold can be 1/3 or less the weight of a greensand mold (perhaps 25% of a greensand mold).
Using any more than that is a waste of bound sand and resin.

And the sand used with resin is required (per the instructions) to be very dry.
I use OK85, which is a commercial fine grain sand, and I am pretty sure it is baked, since it is extremely dry; I keep it sealed in 5 gallon buckets.

Edit02:
OK85 sand bound with sodium silicate is a viable alternative to either epoxy or resin-bound molds, and supposedly works with iron and other metals.
Sodium silicate can be hardened using either CO2 (5 second gas only....do not overgas soldium silicate molds or cores), or a catalyst can be used which will cause the mold to self-harden.
Sodium silicate is much more environmentally friendly than epoxy or resin.
It is often seen used for making cores, but it can be used to make the entire mold too in the same manner than resin-bound sand is ued to make molds.

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pirmin:
Fantastic ! i wish i had a garden for such projects! casting iron is realy something that starts to disapear. when i read old ME magazines i see that many local communitys and societys had someone in their area wich was able to cast iron . Now its a very expensive thing ! here in austria there is no company that offers casting services to private model engineers.

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