采用Gleeble-3500热模拟试验机模拟了550 MPa级桥梁钢板热变形奥氏体的动态连续冷却转变过程,结合金相法绘制实验钢的CCT曲线,并对相变组织进行硬度和拉伸性能测试.结果表明,当冷却速度小于1℃/s时,钢的冷却组织为粒状贝氏体,其基体为铁素体；当冷速为5℃/s时,转变组织中开始出现少量板条贝氏体,为粒状贝氏体+板条贝氏体的混合组织,且粒状贝氏体岛状组织明显沿板条界面分布；随冷速继续增大,粒状贝氏体减少,板条贝氏体特征更加明显.随冷速的增大,组织细化,连续冷却转变组织硬度增加,强度升高.%The deformed austenite transformation of 550 Mpa bridge steel during continuous cooling was analyzed by the Gleeble-3500 thermal simulator, the microstructures of the samples were observed to help drawing the CCT curve, the tensile strength and the hardness was tested. The experimental results showed that the transformed microstructures were block granular bainite with the matrix of ferrite when the cooling rate was slower than lt/s; when the cooling rate was faster than 5 t/s, a few of lath bainite could be shown in the transformed microstructures, and the granular bainite islands dispersed along the laths boundaries. As the cooling rate increased, the amount of granular bainite decreased, and the lath bainite became the main phase of the microstructures, at the same time, the microstructures were finer, and the hardness and strength increased.
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