How to improve moulding sand refractoriness 2

[luizpaulom17]

So basically my small size mounding sand is turning black after pouring the cast iron. It then gets grey and star decomposing in the ground. The wall thickness of the mounding is thin too. I thought about putting some iron oxide in the mixture so it will increase its heat capacity but I still think it wont be enough. Any ideas of what else can I add to avoid it turning grey and decomposing in the floor?

 

[Guest102023]

Foundryman’s Handbook is the classic text.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[EdStainless]

There are many factors the sand (size and re-use), the clay, the oil, moisture, packing density, how you cure them.
And I am sure that there are more.
the American Foundry Soc has some very good basic guides to working with oil sand molds.

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P.E. Metallurgy, consulting work welcomed

 

[luizpaulom17]

Why does the sand turn black? Is it oxidation from high temperature?