lowering the melting point of cast iron.

Discussion in 'Sand Casting' started by Ironsides, Sep 11, 2017.

  1. Ironsides

    Ironsides Silver

    Hi everyone

    I had a very successful day lowering the melting point of cast iron.

    I have tried to cast this air vent grille in the past in aluminium and cast iron but it would not fill up the mold completely, so this time around it did fill up the mold. This type of cast iron would be good for beginners trying to melt cast iron if their furnace is struggling to get to cast iron pouring temperature.

    Using an A6 crucible for this experiment I had two delays before I emptied the crucible. The first one was 29 seconds ( crucible in furnace to pouring). The second delay was 36 seconds ( I forgot to put out the ingot mold ) This shows that small crucibles can be used even though they cool off very fast.

    Have a look at the video
     
    _Jason, Al2O3 and DavidF like this.
  2. PatJ

    PatJ Silver

    That is a very nice casting.
    I believe you could sell a bunch of those for house restorations.

    Does ferrosilicon do the same thing?
    I have noticed that the melt appears to gets much more fluid after adding ferrosilicon.

    I wonder if there is a stateside source for that material?

    Do your crucibles come with the plinth on them, or is that something you are adding to the bottom of the crucible to elevate it?
     
  3. DavidF

    DavidF Administrator Staff Member Banner Member

    Excellent video Ironsides. Does the ferro phosphorus have any ill effects to the machine ability to the cast iron?
    That A6 sure did hold alot more metal than I would have thought watching your pours. When you said that you suspected the molds didnt fill I thought "yes he is probably right on" Its nice to be wrong :)
     
  4. Ironsides

    Ironsides Silver

    PatJ Ferrosilicon does the same thing but ferro phosphorus works even better than ferrosilicon. The first iron casting I showed in the video ferrosilicon was used and it looked very fluid but it would not flow everywhere into the mold. Bath tubs and other sanitary castings were made with this type of cast iron because it flows really long distances. The plinths are stuck to the crucible as I thought using a smaller crucible in my furnace, it would need to be closer to the lid. That A6 crucible sits a long way from the lid compared to my larger crucibles. Having said that it still melts cast iron so quickly. It does not bother me that they are stuck there so they will remain until the crucible is unsafe to use.

    DavidF ferro phosphorus makes a harder wearing iron, steam engine cylinders were made with this alloy so they would last longer. I ran a file across these castings, it will cut it but it is not like a really soft iron. Have close look at the video where I am pouring, I edited out all the cursing because the mold filled up so fast.
     
  5. DavidF

    DavidF Administrator Staff Member Banner Member

    That puts a smile on my face. Seems we have all been there and thought that we were not going to get our parts out, I think it makes us happier when we do.
    "A harder wearing iron..." That can be very useful... Going to have to track down some ferro phosphorus now...
     
    Last edited: Sep 14, 2017
  6. DavidF

    DavidF Administrator Staff Member Banner Member

    If someone asked me to cast that grate, I would have run to the wind...
     
  7. Jason

    Jason Gold

    I saw your video earlier. First class pour. You iron guys are outta my league. I'm stuck melting beer cans and this copper looking crap called Bronze. :p
     
  8. Jason

    Jason Gold

    Or if it's got dogs on it... lol
     
  9. Tobho Mott

    Tobho Mott Gold Banner Member

    Congrats on a successful pour, that came out "grate"! :)

    Always wondered how they get bathtub molds to fill; mine has a chip on it, and at least in that one spot the enamel coating is much thicker than it looks!

    Jeff
     
  10. DavidF

    DavidF Administrator Staff Member Banner Member

    Nah, the dogs are on easy street, but that grate? Well I would have to give up coffee for a week just to be able to pull the pattern from the sand... Then to get a good casting.. I would have thought it was near impossible, but seeing that ironsides pulled it off (and getting some good information on ferro phosphate) .. Well I still dont want to try it LOL
    I thought home heating radiators were high in silicon content, now i wonder if they had phosphate added to the mix?? I would be nice to have the testing equipment to find out. Im babbling..
     
  11. JoeC

    JoeC Copper

    OK, you win with that, hand back the hobby badge, you are now a pro

    That is just awesome, before I got stuck in an Aluminum casting career, I did gray and ductile iron, a properly hot material

    Great success in thin section casting. Stove plate (thin section and rangy) used to be cast out of cupola iron which by nature had high Phosphorous and Sulfur from the poor quality coke used as fuel.

    The old timers used to say such metal would "run like a bandit". Metallugry developed from trying to understand the why of this

    Your phase diagram shows what is going on, the eutectic point (lowest melt point) of cast iron is 4.3% Carbon, and other elements act like Carbon per this formula

    [​IMG]

    https://en.wikipedia.org/wiki/Equivalent_carbon_content

    So Carbon, Silicon, Phos, Sulfur, & Manganese all lower the melt/freeze point towards the eutectic temp of around 2100 F

    This lets a gas/oil fired furnace provide enough superheat or extra temp to allow the metal to fill thin sections before freezing off on a misrun

    Without these elements the furnace has to achieve higher temps to melt and doesn't have enough energy left to provide enough to superheat the metal and you get misruns

    We used thermal analysis to pour samples to find the CE and predict various properties

    quik cup.jpg

    This guy has the best take on thermal analysis in my opinion if you want to head for a metallurgy degree

    http://www.meltlab.com/SparkmanInfo.html

    The only down side is P, Mn, S reduce strength, although for a cosmetic casting it really is no concern

    I just smashed up a cast iron bathtub, a shame, maybe took 5 minutes

    Do you have a way to measure your actual cast iron temp, I have another post somewhere with the tools for that

    FoundryJoe
     

    Attached Files:

  12. Ironsides

    Ironsides Silver

    Excellent reply! I have a pyrometer but only use to measure furnace temp. If I dip it into molten cast iron it will not last more than two dips. Platinum wire is very expensive where I live. Cosmetic castings does not need much strength but I did break up an ingot, it was a lot tougher than I thought it would be. That is the same formula I used to work out how much silicon to add.

    DavidF Electric motor end bell castings are also the same alloy as bath tubs. Radiators could be the same alloy.
     
    Last edited: Sep 12, 2017
  13. JoeC

    JoeC Copper

  14. Ironsides

    Ironsides Silver

  15. DavidF

    DavidF Administrator Staff Member Banner Member

    Cant spare an arm or leg?? I hear kidneys are worth quite a bit as well... Thats the sad truth of things when it comes to shipping down under. There must be a better way..
     

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