低冷却速度下700MPa级V,Ti微合金化高强钢组织和性能

Microstructure and Property of 700 MPa Grade V/TiAlloyed Steel at Lower Cooling Rate

采用光学显微镜、扫描电镜和透射电镜观察700 MPa级钒微合金化低合金高强钢热轧后在3~5,1.5~2和0.3~0.5℃/s三个不同冷却速度下获得的微观组织,对晶粒度、珠光体体积分数、珠光体片层间距进行了定量分析,测定了拉伸性能并观察了拉伸断口。结果显示,冷却速度为1.5~2℃/s时产品性能最佳。这是因为该冷却速度下铁索体基体上纳米碳化物数量增加且弥散细小,析出强化效果随析出物数量呈线性增加。

The microstructures of 700MPa grade V-bearing microalloyed high strength low alloy steel with different cooling rate of 3~5,1.5~2 and 0.3~0.5 ℃/s respectively after rolling were observed by optical microscopy,scanning electron microscopy and transmission electron microscope.The grain size,phase fraction of pearlite and the interlamellar spacing were obtained by quantitative metallographical examination.The tensile properties were measured and the fractures were analyzed.It showed that the properties of product is best with cooling rate 1.5~2 ℃/s,because the precipitation particles are much more than that with other cooling modes and the precipitation strengthening effect increased linearly with the precipitation amount.