Aluminum sand casting for Chenery Gnome Rotary

[albd5a]

The remaining aluminum needs to be poured out of the crucible into ingot molds.
I use steel ingot molds that are made from steel angle iron, with the end caps welded on at an angle to allow the ingot to release.
The ingot molds need to be preheated to perhaps 500 F before you pour into them.
I generally place the ingot molds in the exhaust stream of the furnace.
If you don't preheat the ingot molds, the slight amount of moisture on the surface can flash and pop the molten aluminum back into your face.

If you leave metal in the crucible, it could crack the crucible as it cools/contracts, and then expands when heated.
Some folks scrape out their crucible after a pour, but I have never done that, and never had any crucible problems.
All of my crucibles after the first off-brand one have been Morgan Salamander-Super clay graphite; one for each metal type to avoid contamination.

Here is a video of what can happen if the ingot mold is not preheated to about 500 F.
Needless to say, never wear synthetic clothes or shoes when melting/pouring iron, since it will melt onto your skin.

I had this exact thing occur with iron, and I had preheated my ingot molds, but not to 500 F.
I got some 3rd degree burns when some iron splatter ran down inside my gloves.
You want burn photos? I got burn photos.

What is the best type of fire extinguisher to use?

 

[Fidlstyks]

I do not want a cracked crucible!!! So, thank you. How long can a graphite crucible be used for, about 8 kg crucible?

I do not want a cracked crucible!!! So, thank you. How long can a graphite crucible be used for, about 8 kg crucible?

I use no 16 Clay Graphite crucibles for iron casting, they pour around 400# before getting thin, at around 42# per pour.
I use longer lasting Carbon bonded Silicon Carbide for aluminum abd brass. They last alot longer.
What can happen to them is the drawing of moisture. If you even leave one out in the dew of night, they can split off from steam. One must seek dryout advise from a manufacturer.

 

[albd5a]

I use no 16 Clay Graphite crucibles for iron casting, they pour around 400# before getting thin, at around 42# per pour.
I use longer lasting Carbon bonded Silicon Carbide for aluminum abd brass. They last alot longer.
What can happen to them is the drawing of moisture. If you even leave one out in the dew of night, they can split off from steam. One must seek dryout advise from a manufacturer.

If I am understanding this correctly, that would be 10 pours at the most. And that’s the problem, they get thin?

 

[Fidlstyks]

If I am understanding this correctly, that would be 10 pores at the most. And that’s the problem, they get thin?

For running 2,900°< aluminum they can last alot longer. Yes when they melt away and the top ring meltsbrakes out. Time for a new one. One can see it.

 

[Fidlstyks]

Looking at my flasks, half are only 3-1/2" tall on cope or drag side.
For your little piece, that would not be the problem.
The first pour looked like either hot sink, never filled from too cold or steam. But steam usully has other signs. Like it wanted to fill over the pock mark, with a real thin skim.

 

[GreenTwin]

I do not want a cracked crucible!!! So, thank you. How long can a graphite crucible be used for, about 8 kg crucible?

have been using my Morgan Salamander Supers for over 10 years, and they are all in good condition.
I have never scraped one out.
The aluminum film that remains in them after you pour the molten metal out is very thin and flexible.

 

[GreenTwin]

If I am understanding this correctly, that would be 10 pores at the most. And that’s the problem, they get thin?

A good crucible brand will last almost indefinitely at aluminum temperatures.

At brass/bronze/iron temperatures, you may get 30-40 melts on a high quality crucible.

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[GreenTwin]

What is the best type of fire extinguisher to use?

I run my furnace out in the driveway, well away from the garage, and I use diesel, with is not very flamable.
I showed someone a video of one of my casting sessions, and they exclaimed "Not a single fire extinquisher in sight anywhere ! ".

I had not really thought about a fire extinquisher, and I actually need to find one and know where it is, but it is not fire I am worried about.
The thing to avoid is getting moisture in, on, or around a hot crucible full of metal, because if you introduce moisture into hot molten metal, even a very trivial amount of moisture, you will have an explosion.
It is the explosions I work extremely hard to avoid.
Fire is the least of my problems.
I can pour diesel all over my driveway, and put a blowtorch on it, and it is pretty much impossible to get it to burn.
You can drop lit matches into a bucket of diesel, and it will not light.

Kerosene is a lot more flamable, and I don't use it for that reason.

The fire extinquishers I have are the dry powder type.
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[Jasonb]

It's that bit of hot metal from the explosion that lands unseen in the garage or on the shingled roof and starts a fire you need think about.

Time is not a good indicator of crucible life, how many pours in that time? Bit like a car you could do 1000miles a year or 25000miles, I know which will be more worn after 10 years.

 

[GreenTwin]

Clarke Easterling routinely gets 30-40 melts on his Morgan Salamander-Super clay-graphite crucibles, with iron, but this is using crucibles under extremely harsh conditions.
Iron is rough on crucibles, and it is the slag that erodes the surface, not really the molten iron.

Aluminum is very tame metal as far as how it reacts with a quality clay-graphite crucible.
There is no noticeable degradation of any of my Morgan Salamander-Supers that I have used to melt aluminum, regardless of the quanitity of melts.
Aluminum melts at such a low temperature, and the Salamander-Super is rated for continuous 2,900 F, so it is really overrated for the application, which is perfectly ok.
I have never noticed a Morgan SS getting thin with aluminum use as they do with iron.
I would say a Morgan Salamander Super would be good for hundreds of aluminum melts, assuming some corrosive flux is not used.

Using flux may degrade a crucible quickly.
Using borax is the fastest way to ruin a crucible that I am aware of, and I never use borax for that reason.

I chatted with a Morgan sales rep one time, and learned a lot about crucibles.
The Salamander-Super clay graphite crucible is ferrous-metal rated for 2,900 F, but it works very well with any metal (aluminum, brass, bronze), and so many of the backyard casters I know standardize on using that type exclusively, myself included.
I don't mix crucible and metal types though; once I use a crucible for a specific metal, it remains dedicated to that metal.

There are some Morgan crucibles specifically design for aluminum use, which are their "Excel", and "Hi-Melt" silicon carbide crucibles.
It should be noted that these are not ferrous-metal-rated, and their operating temperature rating is significantly lower than a Salamder-Super clay graphite unit.
The rep said the "Hi-Melt" will outlast the "Excel" by a significant amount.

But like I have said many times, don't solve problems that you don't have.
Don't purchases "Hi-Melt" for long life when your Salamander Super shows no signs of wear after numerous uses.

Even my Salamader Super crucibles used with iron don't look that bad, but they do degrade much faster with iron.
You may not ever wear out a Salamander Super with aluminum, if you avoid fluxes.

Also, Morgan crucibles come with a glaze coating on them, and you preheat the crucible to set that glaze.
You should try to not disturb the glaze, since it protects the crucible material beneath it.
Scraping the interior of a crucible after each use just scrapes off the glaze, and degrades the life of the crucible.

A crucible should be tempered per the instructions for that particular crucible type.
This will increase the life of the crucible.
You can see the temper proceedure at the bottom of the Salamander Super sheet below.
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