Effects of Boron and Zirconium on microstructure and magnetic properties of batch annealed Al-Killed low carbon steels

Crystallographic texture is one of the major factors affecting magnetic permeability of steels at flux densities
\geq;1.5T
. It is known that texture formation, and hence, permeability is significantly impacted by the precipitation of retained alumninum and nitrogen as AlN at sub-grains or cold-worked grain boundaries prior to recrystallization. This apparently induces the preferential nucleation and growth of the magnetically unfavorable {111} orientation. Since both B and Zr have a greater affinity for nitrogen than Al, laboratory experiments were conducted to examine their influence on the structure and magnetic permeability of Al-killed, low carbon steels. Investigation showed that the additions of B and Zr resulted in the following: a) substantial retardation of AlN precipitation, 2) suppression of the {111} orientation, and 3) enhanced magnetic permeability. In addition, relationships between magnetic permeability and various levels of B and Zr for different processing conditions were established.