中文摘要：

对V-N微合金化Q550D高强度中厚板进行了控轧控冷工艺试验,研究了沿厚度方向不同位置的显微组织,并测定了其综合力学性能.结果表明：V-N微合金化Q550D中厚板显微组织为多边形铁素体＋针状铁素体,表面至心部的平均晶粒尺寸逐渐增大,针状铁素体的质量分数逐渐减少,20~30 nm的（Ti,V）N及小于10 nm的V（C,N）析出物弥散地分布在多边形铁素体和针状铁素体基体上;试验钢屈服强度、抗拉强度、断后延伸率、-20℃冲击功分别为651 MPa,733 MPa,18%,170 J;细晶强化、析出强化、位错强化、固溶强化、针状铁素体组织强化为主要的强化机制;晶粒细化、低C成分设计、针状铁素体组织的形成为主要的韧化机制.

英文摘要：

The controlled rolling and controlled cooling test was conducted on V-N microalloying Q550D high strength steel plate.The microstructures at different positions along the thickness of the steel were studied and the mechanical properties were tested.The results showed that the microstructure of V-N microalloying Q550D plate is composed of polygonal and acicular ferrites.From the surface to the center of the test sample,the average grain size increases,while the mass fraction of acicular ferrite decreases.It was also observed that the size of（Ti,V） N precipitates is 20~30 nm and the size of V（C,N） precipitates is smaller than 10 nm,and both precipitates distribute dispersedly in the matrix of polygonal and acicular ferrites.The yield strength,tensile strength,elongation and impact work at -20 ℃ of test steel were 651 MPa,733 MPa,18% and 170 J,respectively.The fine grain strengthening,precipitation strengthening,dislocation strengthening,solid solution strengthening and acicular ferrite strengthening were the major mechanisms of strengthening.Meanwhile,the role of fine grain,low C component and the formation of acicular ferrite were the major mechanisms of toughening.