针对球扁钢在孔型轧制时球头、腹板部位组织性能不均匀的问题，研究了钒氮微合金化技术改善高强度球扁钢截面均匀性的作用机制。采用ANSYS有限元模拟了球扁钢轧后冷却温度场的分布。结果表明，球扁钢轧后冷却过程中球头心部冷却较慢，腹板冷却较快。950℃终轧后冷却150S时，球头心部、腹板温度差异约为120℃；对比分析了钒和V—N微合金化球扁钢球头／腹板部位组织、性能的差异。和钒钢相比，V—N球扁钢屈服强度显著提高，球头心部、腹板强度差异约为5～10MPa。V—N设计细化了球扁钢的显微组织，球头心部、腹板平均铁素体晶粒尺寸仅相差1．24μm，低温韧性显著提高。球头心部较慢的冷却速度促进了钒的析出，细化了钒析出物的粒度，显著改善了球扁钢孔型轧制时不同部位冷却速度、变形量差异造成的截面不均匀性。
Microstructures and mechanical properties difference of V and V-N microalloyed bulb flat steel was aria lyzed, and strengthening and toughening mechanism of experimental steel was further discussed. The results show temperature field of bulb flat steel is nonuniform during cooling after finish rolling. The cooling rate in the center of the bulb is much higher than that in the flat. The temperature difference between center and flat is about 120℃ when the finish rolling temperature is 950℃. Yield strength of bulb fiat steel is increased significantly and strength difference between center and flat is only 5 10MPa by using V-N rnicroalloyed technology designing. The microstructures of experimental steel is also refined, the average ferrite grain size difference between center and flat is only 1.24μm which improve the impact toughness of steel ultimately. The slower cooling rate promote the precipitation of V（C,N）, and refining the second particles at the same time, which improve the section homo geneity caused by different cooling rate and pass deformation.
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