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Thread: Horizontal better than vertical casting ?

  1. #1

    Horizontal better than vertical casting ?

    First: happy New Year to everyone !

    I made a candle wax pattern to replicate in stainless steel and copper castings.

    I noticed that in both SS and copper the casting is much more rough when cast vertically instead of horzontally. The outer diameter of the flower is 45mm (1 3/4").
    On the picture they are all displayed.

    Top left: the candle wax pattern.

    Top row: SS and copper vertical casting, on the copper one, I still had the sawn off sprue which I put on it for the photo to see the size (almost 4" including the flower). Using a bottle shaped cast iron flask where the 'neck' is the sprue.

    Bottom row: the horizontal castings, where the 'flask' are two aluminum rings 80mm (3 1/4") diameter and each 50mm 2" high.

    In all cases, the 'Delft clay casting' sand (an orangish oily clay like sand) on oil based rather than water based, designed for jewelry casting.
    The sand is OK, but I think that the larger hydrostatic pressure in the vertical casting is larger, particularly with copper (density 8.0 @ 1100 C), stainless steel is about 7.0 @ 1600 C, maybe even slightly lower due to the chrome content. Over a height of 80mm the hydrostatic pressure of Cu is:

    10000mm water equals 1000 mbar
    10000 / 8.0 = 1250mm (liquid) copper equals 1000 mbar, so 1000 * 80/1250 = about 64 mbar == 1psi, assuming 80mm metal column in mold.
    In the horizontal casting it is 1000 * 50/1250 (50mm height of metal column in mold) = 40mbar, so a difference of 24 mbar (0.4 psi) difference. Can that really make castings rougher ?
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  2. #2
    for the smaller castings like that, they're usually cast vertical to allow for more head pressure to push the metal into the molds and into the finer details of the small parts. The higher head pressure usually leads to it pushing the metal into the sand much more and it'll cause it to pick up more of the texture of the sand rather than casting it horizontal. It's handy for casting small thin parts like rings tho that would be normally difficult to fill, and would be cleaned up afterwards.

  3. #3
    Senior Member Spelter's Avatar
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    To my way of thinking, better names for the two flask styles are vertical parted and horizontal parted, named for the orientation of the parting plane at pouring, rather than horizontal and vertical castings.

    I'm thinking the differences in casting quality look like temperature effects, not pressure differences. The botom row ones look like cooler pours, and the differences in flask design could easily drive enough hesitation in pouring to provide a consistent temp difference at pouring.

    As a check, the vertical parted castings will have pressure difference running from the spruing point to the opposite side of the flower. At the spruing point, pressure is about equal to the other flask, the sprue lengths being about equal. The opposite side pressure should be about twice as much, flower height is about sprue length. So pressure increase effects should increase approaching the opposite side. I can't tell from the photos, but with the parts in hand, it's something to look for.
    Last edited by Spelter; 01-01-2018 at 02:51 PM. Reason: typo
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  4. #4
    Temperature might be an option. You are right, the bottom row are cooler pours than the top row.

    The copper castings are made in one session, I first poured the vertical parted and then the horizontally parted from the same crucible, so the first was hotter.
    The SS castings were poured in two separate sessions, the first (in a vertically parted mold) I somewhat overheated the metal because I thought not everything was melted and I could not look directly into the crucible as it was in the rear of the fume hood to prevent any sparks getting out of it and my head + welding helmet could not reach that far. But it turned out to be completely molten, but overheated to well above 1600 C.
    The second session (which I poured in the horzontally parted mold) was molten more quickly. I check normally by dipping the carbon rod into the metal and check whether it hits the bottom. Obviously, during this fraction of a second the arc stops as it shorts the current.

    So a hotter pour results in a more rough casting ?

  5. #5
    Senior Member Tobho Mott's Avatar
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    That seems to be a good general rule, I've often read that for best results (smoother finish, less shrink etc.), you should pour as cool as you can get away with and still fill the mold. What I've seen in my own small experience would seem to support this.

    Jeff
    Tobho had learned to work Valyrian steel at the forges of Qohor as a boy. Only a man who knew the spells could take old weapons and forge them anew.

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  6. #6
    Indeed that is true, but with cast iron has no sharp melting point, but more a 'melting range' between 1150-1350 C , when not hot enough it is a syrupy like liquid which results in loss of detail and hence it needs to be heated to 1400 C (2600 F).

    Stainless, copper and bronze don't have this issue.

  7. #7
    Senior Member Spelter's Avatar
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    Yep, cooler pour=smoother finish, often looks as if higher surface tension.

    You might want to round up a mirror for looking into the crucible. I dug one out myself, the other day. I was a bit skittish about having my head in line with the opening of an experimental crucible in a new heater. Saved some anxiety.
    "The former lives of objects need not interfere with their current use."

  8. #8
    Senior Member Tobho Mott's Avatar
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    Quote Originally Posted by metallab View Post
    Indeed that is true, but with cast iron has no sharp melting point, but more a 'melting range' between 1150-1350 C , when not hot enough it is a syrupy like liquid which results in loss of detail and hence it needs to be heated to 1400 C (2600 F).

    Stainless, copper and bronze don't have this issue.
    I guess that is where that "as cool as you can get away with" comes into play - if the casting lacks th anticipated detail, you didn't get away with pouring it that cool!

    But I have zero experience casting ferrous metals, so you should take anything I say here with that firmly in mind and a grain of salt.

    Jeff
    Tobho had learned to work Valyrian steel at the forges of Qohor as a boy. Only a man who knew the spells could take old weapons and forge them anew.

    How I built my oil furnace | My Photo Album | My Videos | TheHomeFoundry Forums

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