The relation between carbon content and hot rolling temperature in developing high induction in boron silicon–iron

Abstract

The development of high induction in boron silicon-iron involves satisfying both composition and processing requirements. One requirement for high induction, which necessitates complete secondary recrystallization to a strong (110) [001] texture, is sufficient carbon to assure the presence of some austenite at the hot rolling temperature. A related requirement is that a minimum of 3–4 ppm boron must be dissolved at the rolling temperature for the subsequent development of high induction. The objective of the work to be reported was to determine whether it would be beneficial to magnetic properties to raise the hot rolling temperature, thereby dissolving more boron, providing the carbon content was also raised to maintain the austenite content. Two sets of laboratory alloys, one with 30 ppm nitrogen and the other with 50 ppm nitrogen, and with carbon contents ranging 0.025% to 0.050%, were hot rolled from 1200, 1250, and 1300 °C. The highest inductions were obtained by hot rolling the 0.050% carbon alloys, whether with 30 or 50 ppm nitrogen, from 1250 or 1300 °C, with the higher rolling temperature giving the higher induction. It was concluded that increasing the hot rolling temperature, thereby dissolving more boron, is beneficial provided the carbon level is increased to maintain the austenite content around 5 volume percent. The major limitation of high austenite contents is severe edge cracking, as was encountered with about 20 volume percent.