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Thread: Novice Casting Questions

  1. #1
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    Novice Casting Questions

    I'm new to the forum, and retired so I'm not real adept at forums.

    I hope my questions aren't too elementary but I can't seem to find the answers.

    I've made a burner (mini-mongo style) which burns with a good blue flame and is pretty stable. I was going to build a furnace but tried a brick furnace first and even with gaps works well to melt aluminum.

    IMG_0984.jpg

    I've been melting aluminum cans and casting muffin ingots. My first sand casting was a cylinder 1-1/4"x6" and I thought it turned out well

    IMG_0988.jpg

    IMG_0989.jpg

    I was using talcum powder for parting. My second casting I used baking flour (I thought I read wheat flour was good but didn't know if that was Gold Bond Self Rising!) My second one burned the sand. Flour? Too hot? A problem? Did I damage the sand?

    IMG_0995.jpg

    IMG_0996.jpg

    It machined fine, but has very small (0.020") air bubbles. I measured the density to be about 95% of 6061 density.

    IMG_0999.jpg

    Thnaks in advance for any help I can get!

  2. #2
    Moderator DavidF's Avatar
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    Welcome to the forum, and thank you for the pictures....We like pictures!
    Im not really sure what to think of the burnt sand. Maybe someone on here has had a similar experience.??
    One thing I will advise is to step away from melting cans and start finding some good cast parts to melt down.
    A calm sea does not make a skilled sailor....

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    most of the black burnt looking sand is probably flour that burned when the molten metal was poured in. Your sand will probably have a smell about like my sisters biscuts but otherwise is unhurt.

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    I have seen the recommendation to not melt cans, and I have been collecting castings to melt. But what is wrong with melting cans? All I have read is they make a lot of slag. But they are free and I am practicing.

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    Quote Originally Posted by dallen View Post
    most of the black burnt looking sand is probably flour that burned when the molten metal was poured in. Your sand will probably have a smell about like my sisters biscuts but otherwise is unhurt.
    Thanks for the advice. Is talcum powder ok for parting compound?

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    hit up the dollar store for a big jug of baby powder.



    nothing wrong with them other then you loose about half of what your trying to melt to dross/slag, plus the alloy cans are made from isn't one of the best casting alloys around.

  6. #6
    Moderator DavidF's Avatar
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    Theres more to it than just slag. Cans are a pretty pure source of aluminum but that is not all ways a good thing. Aluminum is alloyed to increase it physical properties and or increase its cast ability. Metallurgy needs to be considered any time a casting is to be more than ornamental.
    A calm sea does not make a skilled sailor....

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    A pure metal solidifies at one temperature and can cause shrinkage defects, a metal with many various components freezes over a range of temp and is easier to make a feeding system to prevent shrinkage cavities.

  8. #8
    Quote Originally Posted by DavidF View Post
    Metallurgy needs to be considered any time a casting is to be more than ornamental.
    That's what I told my wife when I wanted to give her a wedding band made of steel! I lost that argument. :-/
    Visit me: WWW.HandcraftedLanterns.com
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    I've seen flour used as an additive to the sand in small proportions but not using it as parting (till now). I use a commercial parting that I overbought several years ago but I understand white chalkline chalk works well.
    High melt temp, length of time spent molten, and furnace atmosphere can all contribute to your porosity. A tight furnace would help you to control those variables. You could consider degassing as well, but it looks like you've gone to the trouble of making sand and tools, so you might as well complete a furnace.
    Welcome to the forum!

    Pete

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    Quote Originally Posted by hamilton View Post
    A pure metal solidifies at one temperature and can cause shrinkage defects, a metal with many various components freezes over a range of temp and is easier to make a feeding system to prevent shrinkage cavities.
    Thank you. I was surprised I didn't see anything I thought might be a shrinkage defect in the cylinders. Maybe that's an easy shape to cast as well.

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    Quote Originally Posted by jagboy69 View Post
    That's what I told my wife when I wanted to give her a wedding band made of steel! I lost that argument. :-/
    So she went for looks instead of durability?

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