Zhou, F.; Wu, K.; Zhou, W., and Matrosov, M., 2015. Fine-grained X80 pipeline steels produced by a novel ultra fast cooling process.

The relationship between microstructure and the mechanical properties of the X80 pipeline steels produced by an ultra fast cooling process was investigated using scanning and transmission electron microscopy and an energy dispersive spectrometer. Predominantly fine-grained acicular ferrite microstructure was obtained from the ultra fast cooling process. The developed X80 pipeline steel had low yield ratio and low temperature impact toughness. The ultra-fast cooling resulted in work hardened austenite before the phase transformation and also pushed the transformation to a lower temperature. Also, the Nb-Ti carbonitride precipitation was inhibited during ultra fast cooling. Therefore, the fine-grained microstructure and superior mechanical properties were attributed to grain refinement and the inhibiting of Nb-Ti carbontride precipitation, which was caused by ultra fast cooling.