Effect of Nb/V/Ti Microalloy on Microstructure and Properties of 16Mn Seamless Steel Pipe

Abstract

In order to study the effect of Nb, V and Ti microalloys on the microstructure and properties of 16Mn seamless steel tube, the static CCT diagram of tested steel was made on Glecble-3800 thermo-mechanical simulator. Based on the observation of microstructures and precipitates by optical microscopy, SEM and TEM, the effect of different microalloy on mechanical properties of 16Mn steel was analyzed. The results show that Ti treated 16Mn steel is advantageous to both grain refinement and the low temperature impact toughness. The impact toughness of Nb or V microalloyed steel is decreased, which appeared bainite in hot rolling. Normalizing can improve the impact toughness of Nb microalloyed steel, while the microstructure and properties of V microalloyed steel are not improved. 16MnTi is taken to produce hot-rolled pipes with wall thickness between 8 mm to 16 mm, that impact value is more than 80 J at - 40 °C; while 16MnTiNb is taken to produce normalized pipes with wall thickness greater than 16 mm, that impact value reaches 120 J at -40°C.