Effect of boron on intragranular ferrite nucleation mechanism in coarse grain heat-affected zone of high-nitrogen steel

The effect of boron on intragranular ferrite (IGF) nucleation mechanism in the simulated coarse grain heated-affected zone (CGHAZ) of a high-nitrogen steel was investigated. When boron (B) was added to the steel, the ferrite transformation temperature increased from 775 degrees C to 800 degrees C and the amount of polygonal ferrite increased from 63.2% to 78.6%. Consequently, the ductile-to-brittle transition temperature decreased from -30 degrees C to -50 degrees C. (Ti,V)(C,N)-MnS-BN, MnS-BN, Al2O3-MnS-BN, and BN served as IGF nucleation sites. The core of the complex precipitates was formed by undissolved (Ti,V)(C,N)-MnS, Al2O3-MnS, and MnS, with a BN cap formed on the undissolved precipitates, which increased the IGF nucleation potency. (C) 2019 Elsevier B.V. All rights reserved.