形变量和冷却速度对低碳微合金管线钢晶粒细化的影响

以管线钢X52为研究对象,在Gleeble1500热模拟机上,主要进行了在奥氏体未再结晶区不同形变量和冷却速度对X52的相变行为及显微组织影响的研究·通过光学显微镜、扫描电镜分析技术可以发现,随形变量和冷却速度的增加,晶粒明显变细·实验结果表明,在奥氏体未再结晶区轧制可以大大地增加铁素体的形核位置,使晶粒细化;同时冷却速度的增大,使铁素体的形核驱动力加大,形核率增加,也使晶粒明显细化·另外,与低碳钢不同的是,在铁素体晶粒边界和铁素体晶粒内部可以观察到有第二相的析出,在奥氏体未再结晶区轧制时,第二相的析出可以抑制再结晶,并且,析出物的存在不仅阻碍位错的运...

Effect of Deformation and Cooling Rate on the Grain Refinement of Low Carbon Microalloyed Steels for Line-Pipe Applications

The effect of the reduction and the cooling rate in non recrystallization anstenite region on ferrite transformation behavior and the microstructure were studied on the Gleeble 1?500 thermomethanical simulator for the pipeline steel X52. It is shown that the grains become fine with the increasing of reduction and cooling rate. The experimental results indicate that the deformation in non recrystallization region greatly increases ferrite effective nucleation sites and leads to grain refinement. At the same time,the acceleration of cooling rate can enhance the driving force of ferrite nucleation so that can increase nucleation rate to result in fine grains. On the other hand,the second phase precipitates can restrain the occurrence of recrystallization,can hinder the movement of dislocation and can promote dislocation generation. All these mechanisms result in the grain refinement in the micro alloyed steels which are different in the low carbon steels. The strain induced ferrite,ferrite recrystallization and second phase precipitates are the three main factors to refine microstructur in the steel.