39 - Elimination and Neutralization of Boron in Ductile Irons

Abstract:

The presence of small amounts of boron in ductile iron is reported to have multiple and sometimes conflicting effects on the mechanical properties of ductile irons. The technical literature up until the early 1990’s states that small amounts of boron is a powerful carbide stabilizing element. Boron levels as low as 0.001% (10 ppm’s or parts per million) stabilize pearlite but larger amounts were found to form very stable carbides. Recent investigators have found just the opposite effects at very low boron levels in pearlitic ductile iron; reduced pearlite levels and Brinell hardness have been reported at levels between 0.0011 and 0.002% (11 to 20 ppm).