Determining Iron Hardness vs White Iron Detection by Wedge Testing

Discussion in 'Sand Casting' started by Melterskelter, Jun 4, 2023.

  1. Melterskelter

    Melterskelter Gold Banner Member

    Today I had a runout of one of my molds for reasons that are unclear to me. Of course, a few cuss words resulted. But it also presented an opportunity to learn about rapid chilling of iron as I had promptly sprayed the pancake of iron on the ground with water to prevent it burning up my wooden flask. The iron had been inoculated with 1 oz of FeSi a minute prior to pouring.

    I expected the resulting iron to be white and in the range of 60+ Rc. Well I broke the piece and did not see any white iron much to my surprise. What I did see was an unusually fine-textured grey iron, but not any white iron even on the rim. So next I tried drilling it with a standard 1/4" bit and drill motor and I was able to drill it just fine. Next I took it home and tested it with both my Wilson Jr calibrated hardness tester and with my Leeb hardness tester. They agreed that the iron was about 42 on the Rc scale and was at the uppper limit or off the Rb scale. My machine tools like my lathe and my Bridgeport milling machine test in the mid 140's on the B scale which would be around 10 or so on the C scale.

    So, my conclusion is a wedge test of iron can distinguish grey from white iron. But it will not tell you if you have soft iron or relatively hard grey iron just that your iron is or is not white and superhard. Maybe knowing cast rion is soft won't matter in many cases, but it often does and especially so in the straight edges I cast. They routinely test in the mid 140's to low 150 HRB.

    Chilled Iron.JPG
    This is the iron "cowpie" formed by the runout. Near the center of the left half of the pie you can see a drilled 1/4: hole made with a common drill bit and drill motor.
    Chulled  Iron Runout.JPG

    Denis
     
  2. Billy Elmore

    Billy Elmore Silver

    We have a lot of those cow pies on top of our mold line if the pouring unit is not functioning as it should.LOL We do not cool them with water but being exposed to air before solidification is what we refer to as rapid cooling. The thinner sections usually contain more white iron than the thicker sections will. I usually do not see white iron in anything with similar thickness unless something is wrong with the chemistry or the late addition was not added and it is usually accompanied by shrinkage in the thickest or hottest sections. The addition you made to it seems to be working!
     

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