Kinetic Aspects of Nitrogen Removal during Vacuum Treatment of Low-Alloy Steels

Abstract

This study investigates the kinetic features of nitrogen removal during vacuum treatment of low-alloy steels under industrial conditions. The removal of dissolved nitrogen during vacuum treatment is a critical stage in the production of low-alloy steels, as excessive nitrogen content negatively affects mechanical properties and service performance. Although thermodynamic conditions under vacuum are favorable for nitrogen desorption, industrial practice shows that degassing efficiency is often limited by kinetic factors. The analysis is based on industrial data obtained from vacuum degassing operations and is supported by classical mass transfer theory and kinetic modeling concepts. Nitrogen removal is considered as a diffusion-controlled process described by a first-order kinetic approach, with particular attention given to the influence of vacuum stability, bubble dynamics, and metal–gas interaction mechanisms. The results demonstrate that stable vacuum conditions significantly enhance nitrogen removal efficiency, whereas pressure fluctuations reduce mass transfer effectiveness and may lead to partial nitrogen reabsorption. Comparison with published numerical and industrial studies confirms that kinetic limitations play a decisive role in determining the final nitrogen content after vacuum treatment. The findings highlight the importance of integrating theoretical models with real industrial data to ensure stable and reproducible refining results. The proposed approach provides a practical basis for optimizing vacuum degassing parameters and improving the quality of low-alloy steels in industrial steelmaking.