Effects of Rolling and Coiling Temperatures on Transformation Kinetics, Microstructure, and Properties of a Low-Carbon Bainitic Pipeline Steel

Effects of rolling and coiling temperatures on the microstructure and properties of a low -carbon, high-strength pipeline steel were investigated using a dilatometer, scanning electron microscope, and transmission electron microscope as well as tensile experiments. The results show that during the thermal mechanical control processing, coiling temperature played a more important role in tailoring the microstructure and mechanical properties than the rolling temperature. Finer grain size and higher strength at the cost of a slight decrease in elongation were obtained by decreasing the coiling temperature, while the microstructure and mechanical properties varied little at different rolling temperatures when the coiling temperature was the same. The bainite starting temperature decreased with the increase of rolling temperature, while it was not affected by the coiling temperature. Specimens at a low rolling temperature or a low coiling temperature exhibited a larger peak transformation rate, indicating the pro-moted transformation kinetics.