Abstract: The microstructure and mechanical properties of controlled rolling and controlled cooling 0. 31% Ni and 0. 88% Ni two Nb-Ti microalloyed NiCr steel are investigated. The results show that granular bainite, upper bainite, acicular ferrite, polygonal ferrite and a little of pearlite in marine steel are obtained by controlled rolling-cooling. Controlled rolling and control! cooling result in the refinement of the feirite grain and the increase of M-A islands. Both steels have high tensile strength,yield strength,elongation and hardness,and the mechanical properties of 0. 88Ni- 0.32Cr steel are higher than those of 0. 31Ni- 0.33Cr steel. The impact energy of longitudinal direction all of the marine steels exceeds 200 J,and that of 0.88Ni- 0.32Cr steel exceeds 300 J at _80℃. 0. 88% Ni is optimum of containing nickel of steel. This is attributed to the ferrite grain refinement strengthening, M-A islands compound strengthening, precipitation strengthening and dislocation strengthening due to controlled rolling and controlled cooling. Nickel effectively improves low-temperature impact toughness of marine steel.

摘要： 研究了0.31%Ni和0.88%Ni二种控轧控冷Nb-Ti微合金化NiCr钢的组织和性能。结果表明,船舶用钢控轧控冷获得粒状贝氏体、上贝氏体、针状铁素体、多边形铁素体及少量珠光体等组成的复合组织。控轧控冷造成铁素体晶粒尺寸细化,细小M-A岛增多。二种钢均获得较高的抗拉强度、屈服强度、伸长率和硬度,0.88Ni-0.32Cr钢性能优于0.31Ni-0.33Cr钢。船舶用钢-80℃试样纵向冲击功都在200J以上,0.88Ni-0.32Cr钢甚至超过了300J。该钢中最佳的Ni含量为0.88%Ni。由于控轧控冷造成了铁素体细晶强化、M-A岛复合强化、析出强化和位错强化,合金元素镍有效的提高了船舶钢的低温冲击韧性。