Optimization of Nitrogen Injection via Top-Blown O2–N2 Mixed Gas in BOF Steelmaking for Enhanced Rebar Performance

Rebar is a critical material in concrete constructions like high-rise buildings and seismic-resistant structures. To enhance its properties, microalloying with nitrogen is employed, but traditional methods using micro alloy additives such as vanadium (FeV), niobium (FeNb), titanium (FeTi), and vanadium nitride (VN) face issues of high costs, reduced purity, and difficulty in controlling molten steel composition. This article presents a novel approach of injecting top-blown O2–N2 mixed gas to increase nitrogen content efficiently. Experiments simulated HRB400 steel samples, varying N2 ratios (10%, 20%, 30%, 40%), temperatures (1500 °C, 1550 °C, 1600 °C), and blowing times (1, 2, 3 min). Results show that optimized parameters enable nitrogen content adjustment from 50 to 104 ppm, with nitrogen utilization improved to 5.4%. This method utilizes inexpensive N2 gas, reduces impurities, and provides precise control, offering a cost-effective and sustainable solution for high-performance steel production by replacing costly alloys and meeting nitrogen requirements.