Issue with making Ductile iron

Discussion in 'Sand Casting' started by metallab, Oct 16, 2022.

  1. metallab

    metallab Silver

    I tried the method of adding Mg metal + Ferrosilicon to liquid cast iron to convert it to ductile iron.
    I melted cast iron and when it was fully molten, I added FeSi mixed with Mg turnings wrapped in a napkin to the metal. The paper obviously burned away and when the Mg metal came in contact with the iron (which was over the boiling point of Mg) it vigorously ignied, but part of it is probably accepted along the FeSi by the iron. Then I stirred it with a steel bar and the surface looked clean like a mirror. Five minutes after the adding I poured it (the surface was still shiny).
    The mold filled normally, but break tests showed still gray, see first image below.

    What am I doing wrong ?

    castiron-fracture.jpg
    Detail of the fracture. The image is about 1" wide.


    RX603301.JPG

    The casting seen from top.
     
  2. Ironsides

    Ironsides Silver

    I have never tried to make ductile iron before so I cannot help you there but you are getting closer to filling up those seashell molds.
     
  3. Rocketman

    Rocketman Silver Banner Member

    Based on my experience working in an iron foundry years ago:

    You've likely created ductile iron base metal (which behaves somewhat similar to grey)
    Ductile iron does not achieve its ductile properties until it's been heat treated after casting
     
  4. metallab

    metallab Silver

    Now I remember that in 1978 I did apprenticeship at an iron foundry making automobile parts where they made a kind of ductile / malleable iron (they called it 'temper iron') which was indeed heat treated for several hours. Or is that 'malleable iron' ? What is the difference ?
     
    Last edited: Oct 17, 2022
  5. Ironsides

    Ironsides Silver

    Malleable iron has to be heated in sealed pots for at least two days to become malleable. Heating for several hours is probably a stress reducing treatment.
     
  6. Billy Elmore

    Billy Elmore Silver

    You will see an immediate higher tensile strength with ductile. You should pour it within seconds of the addition because the mag starts fading immediately. When we add the mg we waited 3 seconds for homogenization before dropping it in the mold.
     
  7. Billy Elmore

    Billy Elmore Silver

    You will not break those castings easily if the addition is right...they will bend first.
     

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