54 - Pearlitic Ductile Iron and the Conflict with Boron

Abstract:

Many foundries have reported that tramp levels of boron can promote ferrite in pearlitic ductile iron, thus requiring excess Mn and Cu to obtain sufficient pearlite levels to produce castings to the pearlitic grades. The purpose of this project was to evaluate the influence of varying levels of B, and Ti and Zr in pearlitic ductile iron with respect to the pearlite content. In the initial phase of this study, the relationship between boron and the ferrite promoting tendencies in pearlitic ductile iron was demonstrated. Experiments in a small prototype foundry demonstrated that additions of ferro-boron to the furnace promoted increased levels of ferrite in Mn + Cu-alloyed pearlitic ductile iron. Boron levels ranging from less than 0.0005% up to 0.0026% increased the ferrite content from 6% to as high as 43%.