Development of high-strength microalloyed coiled rebar

High-strength rebar allows for a reduction in bar diameters, resulting in less congestion in the rebar/concrete column and lower overall fabrication costs. This work presents a development for high-strength, 20-mm diameter coiled rebar by properly adding microalloying elements, primarily Nb. Adjustments were made to the thermomechanical industrial rolling schedule to optimize the Nb precipitation effect on austenite during rolling and to use any potential remaining solute Nb for further precipitation strengthening during cooling. A combination of laboratory investigation and metallurgical modeling coupled with industry trials resulted in yield strength and elongation in excess of 600 MPa and 15%, respectively. © 2018 Iron and Steel Society. All rights reserved.