以管线钢X5 2为研究对象 ,在Gleeble 15 0 0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X5 2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动 ,而且会造成位错的增殖·因而微合金钢细化晶粒的机理主要有 :形变诱导铁素体、铁素体的动态再结晶和第二相的析出抑制晶粒长大使晶粒细化 Taking pipeline steel X5 2 as the research object, on the Gleeble 15 0 0 thermal simulator, the influence of different deformation amount and cooling rate on the transformation behavior and microstructure of X5 2 in austenite non-recrystallization zone was mainly studied. By optical microscope and scanning electron microscope analysis, it can be found that with the increase of deformation and cooling rate, the grains are obviously thinned. The experimental results show that the nucleation of ferrite can be greatly increased by rolling in austenite non-recrystallization zone Position, so that the grain refinement; the same time the cooling rate increases, ferrite nucleation drive increased, nucleation rate increases, but also the grain refinement significantly * In addition, the difference is that with low carbon steel, Precipitation of the second phase can be observed in the ferrite grain boundaries and in the ferrite grains. When the austenite non-recrystallization zone is rolled, the precipitation of the second phase suppresses recrystallization, and the precipitates Not only impedes the movement of dislocations but also causes the growth of dislocations. Therefore, the mechanism of grain refinement of microalloyed steels mainly includes deformation-induced ferrite, dynamic recrystallization of ferrite, and precipitation inhibition of the second phase Grain growth grain refinement