Secondary recrystallization and magnetic properties of high permeability 3% silicon-iron alloys containing boron, sulfur, nitrogen and various amounts of MnS have been studied as a function of final cold reduction using two stage cold rolling method.
Boron-silicon-iron alloys are characterized, as compared to the conventional alloys, by a heavier final cold reduction and increased restraint to normal grain growth with a presence of boron, nitrogen and uncombined S. Laboratory alloys were hot rolled from 1250℃ to a thickness of about 2.8 mm, and cold rolling was performed to a final reduction in the range from 20% to 88%.
The alloys containing 0.004% Mn and uncombined S underwent complete secondary recrystallization and showed the best magnetic property at final cold reductions of 80% and 85%.
In alloys with uncombined S and large amount of Mn (0.057% Mn, 0.12% Mn), however the magnetic induction at the field of 800 A/m ($B_{10}$) was the highest at the final cold reduction of about 60%, and a heavier final cold reduction lead to normal grain growth and low $B_{10}$.
The alloy containing 0.11% Mn but without uncombined S underwent complete secondary recrystallization at only about 20% final cold reduction.
These results indicate that the effect of MnS rather than boron, nitrogen and sulfur dominates as the amount of MnS increases in the boron-silicon steel.
