Optimization of the Final Annealing Temperature for Cold-Rolled Non-Grain Oriented (CRNO) Electrical Steel through Gleeble Simulation

The magnetic properties of cold rolled non-grain oriented (CRNO) electrical steels are determined by the optimum grain size and preferred texture, which are functions of composition, and thermomechanical processing. The annealing process plays an important role in the final magnetic and mechanical properties of CRNO electrical steels. In this work, methodology has been developed for simulating continuous annealing processes using thermomechanical simulator (Gleeble). Cold rolled full hard samples of CRNO steel with Si values 0.3, 0.7, 1.0, and 1.3% were collected and subjected to plant annealing cycles for the temperature range of 780−1000°C. Subsequently, the microstructure, texture and magnetic properties were measured in simulated samples. This paper explains the effect of Si content and final annealing temperature on the grain size and texture, and its impact on magnetic properties such as core loss and permeability. Core loss decreases with increasing annealing temperature up to a certain value and after that increase. This optimum temperature increases with increases in Si content in steel. Permeability decreases continuously with increasing annealing temperature for all Si steel because of the strengthening of magnetically unfavorable gamma fiber [〈111〉//ND (Normal direction)] texture. An empirical relationship was also developed to determine the optimum annealing temperature as a function of Si content. This off line simulation was successfully used to enhance process optimization of new grades by reducing the requirement of online trials that helps in product customization.