Binder Level
To determine the effect of binder level on porosity, cores were made with levels ranging from 1.25-3%. Although these higher levels may never be encountered in actual practice, they were intentionally selected to magnify the effect of binder level or the effect of reclaimed sands having high loss-on-ignition values. As the binder level increased at the same Part I:Part II ratio, the severity of the porosity defects likewise increased.
If sufficient amounts of evolved H and/or N decomposition gases are available to solidifying irons, porosity will generally occur, even with favorable binder ratios and relatively high pouring temperatures. Excessive amounts of dissolved gases stemming from inappropriate charge materials or liquid metal processing will likewise be more susceptible to core gas defects from absorption of H and/or N.
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