Trying Lost Foam with Iron

Discussion in 'Lost foam casting' started by SRHacksaw, Jun 3, 2022.

  1. SRHacksaw

    SRHacksaw Silver

    Thanks Kelly.

    You know, just thinking about it maybe I do have something. I have an old Rockwell block vibrating sander that always has a hard time getting up to speed when you first start it. It's a harmonic problem. I usually have to hold it against something solid to get it out of lower resonance into its high rate. And it takes a while. When it's at the low rate, it's really hard to hold, your hand really tingles after that vibration -- nearly at a painful level.

    Maybe that will do the same thing to a flask. For a flask I have a lot of choices, but maybe just a standard steel bucket would fit both castings in. For a pouring basin I was thinking a cutoff of thin wall stainless tube I have -- I think I might have both 1.25" and 1.5" on hand --- probably larger up to 2.5" as well. And lots of sizes of steel pipe and tube. The other possibility is molding some fireclay and sand, and firing that to vitrify. Or forming that inside a section of pipe. Suggestions?
     
  2. Al2O3

    Al2O3 Administrator Staff Member

    2.5"D x 4"L

    Pouring Cup.jpg
     
  3. SRHacksaw

    SRHacksaw Silver

    Okay, so that wide, it's got to funnel down to 1.25" to fit the foam part. That might best be done with fired sand/clay inside a steel tube section. Tomorrow it's going to rain so I can work on that...
     
  4. Al2O3

    Al2O3 Administrator Staff Member

    For this pour I wouldn't even worry about it. Fill the flask within 1/4" of the top of the sprue. Stick the cup 1/2" into the sand with the sprue in the middle and fill the flask near the top of the pouring cup. Pour and keep the cup full with no gaps in the pour. That's how 90% of hobbyst do their LF pours.

    Best,
    Kelly
     
  5. SRHacksaw

    SRHacksaw Silver

    Well, Kelly I want to keep unbonded sand out of the iron, if at all possible, and molding a little ganister into the steel cup is a couple minutes work.

    Raining cats and dogs now...no pouring iron today. It might clear up late afternoon, so I could fire some cup(s) for use tomorrow.
     
  6. FishbonzWV

    FishbonzWV Silver

    Before Kelly came up with the pouring basins, I used to wrap the top of the sprue with 4 or 5 layers of Aluminium foil. It would keep the sand from collapsing into the mould.
    Oooops, you’re doing iron, never mind.
     
  7. Al2O3

    Al2O3 Administrator Staff Member

    If you're going to do that, may as well make a whole pouring cup with well and weir. It is worth while, but you have a lot of other things going on too.

    Best,
    Kelly
     
  8. SRHacksaw

    SRHacksaw Silver

    Already cut two 4" sections of tube. Nothing else going on today. But in future if making a cast cup, for iron it would be great benefit to have a fence weir from the top to skim any remaining slag bits and floating impurities. Some iron ladles have just that arrangement and pour from the bottom.
     
  9. Al2O3

    Al2O3 Administrator Staff Member

    The offset pouring cups with weir naturally do so as long as you keep them full and active but I'm sure you could come up with an insert or as molded feature to incorporate that. Since the cups are expendable, just want to keep their construction practical. I originally said sodium silicate binder because you could mix a batch of core sand and gas/cure them instantly so you could make them in batches. Since the exterior will be supported by unbound sand, strength shouldn't be an issue other than construction and handling so they wouldn't need to use much material.

    Best,
    Kelly
     
  10. SRHacksaw

    SRHacksaw Silver

    Sounds good. I do have sodium silicate.

    In iron pours the impurities including sand are strongly buoyant because it's 3X the density of liquid aluminum, so the top fence or, better, a side choke in a bulkhead would be what I'd do.

    Sun just came out!

    Top and bottom of the plain pouring cup before baking:
    [​IMG][​IMG]
     
  11. SRHacksaw

    SRHacksaw Silver

    Interesting.....I decided to pre-dry the cups by putting them into a toaster oven @ 150F. After a half hour they weren't fully dry but fairly hard. I took one out to check and it slipped fairly easily out of the steel jacket. Since they would dry faster that way, I did the same for the other. I got them both up past 220F, then cranked the temp up to 350. When they both temped at 325 with an IR thermometer, I turned off the oven and let them cool.

    My original intention was to dry them first, then fire them in the oil furnace. They aren't vitrified at present. But I'm thinking that isn't necessary, now. Baked sand molds aren't vitrified, either.

    I do think I will slip them back in the steel tubes to pour iron, since I expect they will rapidly expand when the hot metal hits them,and that will help keep them from breaking apart. They weren't intended to work standalone.

    Baked liners:

    [​IMG]
     
  12. Al2O3

    Al2O3 Administrator Staff Member

    They look good. They'd be fine buried in sand without the steel sleeve. You'll want to burry them anyway to prevent run outs. It's really helpful to have a large cup for LF, perhaps 10-25% of part volume.......not that you would necessarily want to finish the pour with that much excess in the cup but it's certainly helpful to start the pour with that buffer capacity due to that classic initial pause filling the cup, then the rapid uptake of metal soon after. That along with the occasional flare and smoke can obscure vision and an interrupted pour is the kiss of death for a LF pour.

    Best,
    Kelly
     
  13. SRHacksaw

    SRHacksaw Silver

    Thanks Kelly. The part is 4.9 cu in, the sprue is 2.5 cu in, and the lined pouring cup holds 7.1 cu in.

    Total iron needed if the cup is full and mold filled is 4 lbs. Losses might add a pound. It would be smart to melt 6 and pour ingots if over. Finished part will only be 1 lb 6 oz.

    I'll probably go with half steam radiator metal, and half disk rotor metal.

    Using rotor metal and due to the part's small thickness it's almost certain to chill -- I'll put in a lot of ferrosilicon, say 11 grams, but likely will come out white iron. We'll hope annealing will salvage it.

    Assuming of course it actually comes out at all.....
     
    Last edited: Jun 9, 2022
  14. ESC

    ESC Silver

    I have never seen 1/4" chill with radiator feed stock. You can pour chill wedges to adjust your melt if needed. Let it cool in the sand.
     
  15. SRHacksaw

    SRHacksaw Silver

    ESC thanks, yep, me neither with pure radiator stock, but I have experienced problems with 1/4" thick castings from disk rotors, and that's the reason for the mix. Yep, I do know about chill wedges, and cooling time.
     
  16. SRHacksaw

    SRHacksaw Silver

  17. SRHacksaw

    SRHacksaw Silver

    [​IMG]
     
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  18. Al2O3

    Al2O3 Administrator Staff Member

    After you pour, post a picture of the casting complete with sprue and cup attached as it was positioned in the flask.

    Best,
    Kelly
     
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  19. SRHacksaw

    SRHacksaw Silver

    Some interesting fireworks and cute sand geysers next to the cup which continued spewing sand out for a couple minutes after the pour. Pour was interrupted when cup filled to the rim so I had to stop, then suddenly emptied and I resumed it.

    Sand all over the top spill and pour is from the geysers -- craters are around the cup.

    I did not put the steel pipe section around the cup, since it was too loose to provide support. The cup did crack at the top, at least.

    The melt itself was problematic because I had burner problems (plugging), but got it straightened out by the end. There was a LOT of slag, but I slagged twice, and carefully. No leftovers for ingots, but cup was full until split at top.

    [​IMG]

    [​IMG]
     
  20. SRHacksaw

    SRHacksaw Silver

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