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Hello,

I have looked around for about 30 min and could not find what I am looking, so here is my first actual post. 

I bought a clay graphite crucible online. When I received it I put it over a open flame for 30 min to cure it and take any moisture out of it. I read this is what I needed to do. So 2 days later I fire up the foundry and like 7 seconds later I her a loud pop and a couple of others. So I turned the foundry off and opened it to find my crucible shattered. I've included pictures. 

I emptied my foundry and cut a butane bottle off a butane torch in half and used it. It was bright red after like 2 min. I started putting cans in right after that, and made some ingot. After two heat cycles the tank was too soft and made the top too narrow too fit cans in. 

 

So here is my question what did I do wrong/Right? Should I buy another clay graphite crucible? 

I'm just a beginner and would love a simple to maintain crucible that is not likely to get heat shocked. I have 3 inch square tube with the walls about 1/2 inch thick, should I use that as a crucible?

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Aluminum should be able to use steel crucibles, and why melt cans? they are not a castable alloy

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First; may I commend to your attention: alloyavenue.com a series of forums dedicated to metal casting (used to be backyard metal casting .com)

Second; as mentioned, why melt Al cans?  They are not a good alloy to cast and they generally give you less money for them if you sell them as scrap that way as they can't be sure of the alloy anymore.  To get alloys that are good for casting find items that were cast from Al!

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I was using cans just to learn and try my foundry out at first. I will be getting better aluminum. 

Did I do something wrong with that clay crucible? 

Thank for your advice. 

Also what are some good gloves. I burned my knuckle through my welding gloves the other day, I didn't even touch anything it was when I was pulling my crucible out.

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Thers is nothing wrong with melting cans. It all depends on what you want to do with them. I think it’s awesome to use trash that’s blowing around, melt it, and make art. I do lost foam. I even use them to make belt buckles. If you want to machine it or make parts for a steam engine, then yea, use higher quality AI.

As to why your crucible failed? Could of just been a defect or maybe how you tempered it. The guys over at AlloyAvenue will have better insight.

-m

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Hi Mr.Read, I very gentle pre-heat all my crucibles before first melting action. That means put then empty in your furnace and bring the slowly up to yellow-red heat temperature. After that stop your burner and leave it in the furnace to slowly cool down to room temperature.

If you start melting ‘full power’ with a brand new crucible I will be an expensive hobby to by new ones over and over again.

Another tip for future melting on other materials, please buy a separate crucible for every different material you intent to cast.

Reg Hans

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Thank y'all so much. Is that other crucible still usable to practice pre-heating before I stick a new one in there.

Also can I use a steel crucible to melt brass?

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Hallo C, This is what happens to my cast iron (pseudo) crucible after my second attempt to melt brass. I strongly advice to use clay/carbon/silica crucible for every metal with a higher melting point then 1300 F. Please find also the melting points below. 
At your service, Hans

Cast iron crucible.jpg

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Melting temperatures metals.JPG

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Oh wow. Thank you! I guess I need to learn to control my foundry temp better. Because at the temp I was melting aluminum made my steel butane bottle crucible super soft.

I did just make a super strong crucible out of 5 inch schedule 80 pipe. It's heavy.

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from chapter 21 of  Knifemaking 2.0

The strength of structural steel begins to deteriorate at temperatures above 650°F (345°C) and looses 50% of its structural strength at about 1000°F (540°C) and 90% at 1475°F (800° C).

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not really but we did stay at a Holiday Inn Express once, and notice that the data explains how easily the twin towers fell .

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On 6/25/2018 at 5:24 PM, Steve Sells said:

not really but we did stay at a Holiday Inn Express once, and notice that the data explains how easily the twin towers fell .

"The Two Towers" is my favorite of Tolkien's books. Let's hear it for Dwarf tossing!

We're joshing ya C. We hang here for the free exchange of information and someone somewhere on IFI has the link, file or works in the industry you have a question about. We aren't really all that smart, there are just a LOT of us willing to share what brain cells still function. :ph34r:

Frosty The Lucky.

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On 6/25/2018 at 5:24 PM, Steve Sells said:

t we did stay at an Holiday Inn Express once

as an uninformed African pray tell how?

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In general, pre-heat everything. Crucible, stock, furnace.  Can aluminum...well, the big thing is it has a lot of surface area, but isn't very thick, right? So because it oxidizes so easily, you get a lot of slaggy crud between aluminum oxides and the liners/paint, with very little aluminum to show for your trouble.  Worse, the slag sticks to everything, especially the crucible.  I've had good luck with cast car parts.  An aluminum transmission housing has a looot of aluminum.

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Some of the cast car parts include (I suspect) magnesium in the mix.

 

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Some cast car parts do indeed include magnesium but I have yet to hear of a transmission housing being made of it. Radiator supports and a few rails, crossmembers and some rims.. what I can think of at the moment. 

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Here is some info on aluminum alloys and the major alloying element, magnesium is pretty common. http://www.esabna.com/us/en/education/blog/how-and-why-alloying-elements-are-added-to-aluminum.cfm

Cast wheels were typically A356 which is basically a cast version of the most common alloy 6061. Wheels would be better than transmission cases because they will not be oil soaked. Cast aluminum is porous and it was always a struggle getting getting parts like VW engines, motorcycle side covers, etc  clean enough to weld. May not be a big deal when casting, but something to think about.

 

As to magnesium. It is being used more where weight is a factor because it is lighter than aluminum. Today I have seen magnesium cast onto the part itself for recycling information. Sometimes the name or advertising gives us clues. The Mag77 worm drive saw has a magnesium body. When scrounging it can be difficult to spot but with some research you can find it. OLD VW Bug engines (1200 - 1300cc) were or had a lot of magnesium in them, wheels used for drag racing - and you would only want to melt down destroyed rims as complete ones in good shape are worth a fortune today,  Magnesium when tarnished or corroded has a darker gray color to it than aluminum. It TIG welds beautifully, and gives off a greenish hue to the arc unlike aluminum which is an intense white light. I repaired a "vintage" Yamaha dirt bike rear racing hub that was magnesium for a guy back East. Fun project.

Here is some more aluminum alloy info http://www.aluminum.org/resources/industry-standards/aluminum-alloys-101

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Note that melting magnesium instead of say Al alloyed with Mg is rather tricky and NOT suggested for a neophyte caster!!!!!!!!!!!!!!!!!!!!!!!!!!!  Something about Magnesium fires....(it can be done with a non-O2 atmosphere; but pouring is also difficult.) You don't want to mess around with Mg fires!

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