【摘要】 针对当前Q345qNH耐候桥梁钢的研究，采用Formastor-FⅡ相变仪，测试了含Nb、V的Q345qNH钢不同冷却速率下发生相转变的温度、时间，分析了显微金相组织、硬度值和相变过程，并构建了Q345qNH钢的CCT曲线。结果表明：当冷却速率为0.3～2℃/s时，试验钢组织主要为珠光体和铁素体；冷却速率为2～3℃/s时，试验钢组织由均匀的珠光体+铁素体+少量的粒状贝氏体组成；冷却速率为3～20℃/s时，试验钢组织由均匀的铁素体基体和均匀的粒状贝氏体组成；随着冷却速率的提高，20～50℃/s冷速区间，以铁素体+粒状贝氏体为主导，微观组织中出现板条状贝氏体。硬度和微观组织的关系曲线可以分为3个阶段：铁素体细晶强化阶段、粒状贝氏体增量强化阶段和贝氏体板条形态强化阶段。更多还原

【Abstract】 The Q345qNH weathering bridge steel was investigated. The phase transition temperature and time of Q345qNH weathering bridge steel containing Nb and V at different cooling rates were measured using Formastor-FⅡ phase transformation tester. The metallographic microstructure, hardness and transformation process were analyzed, and the continuous cooling transformation(CCT) curve of Q345qNH steel was created. The results showed that the microstructure of tested steel was mainly composed of pearlite and ferrite when the cooling rate was 0.3-2 ℃/s. As the cooling rate was 2-3 ℃/s, the microstructure was composed of uniform pearlite + ferrite + a small amount of granular bainite. When the cooling rate was 3-20 ℃/s, the microstructure of tested steel was mainly composed of uniform ferrite matrix + uniform granular bainite. When the cooling rate was further increased to 20-50 ℃/s, the lath bainite appeared in the microstructure, but the ferrite and granular bainite were dominant. The relationship between hardness and microstructure could be divided into three stages: the stage of ferrite refined crystalline strengthening, the stage of granular bainite incremental strengthening, and the stage of bainite strip morphology strengthening.更多还原