控轧控冷工艺中冷却温度对Q550D高强钢显微组织和拉伸性能的影响

对热轧Q550D钢板进行控轧控冷处理,研究了6组开始冷却(开冷)温度和终冷温度对试验钢显微组织和拉伸性能的影响。结果表明:6组冷却温度下试验钢的基体组织均由贝氏体+铁素体+马氏体/奥氏体(M/A)岛组成;在相同终冷温度下降低开冷温度,试验钢中铁素体含量明显增加,M/A岛含量略微增加,屈强比减小;在相同开冷温度下降低终冷温度,铁素体含量略有减少而M/A岛含量明显增加,屈强比增大;同时降低开冷温度和终冷温度,铁素体和M/A岛含量同步递增,但M/A岛的增加幅度较小,屈强比降低;在开冷温度755℃、终冷温度395℃下,试验钢具有最佳的拉伸性能。

Effect of Cooling Temperature in Controlled Rolling and Cooling on Microstructure and Tensile Properties of Q550D High Strength Steel

Controlled rolling and cooling process was conducted on hot-rolled Q550 Dsteel plates.The effect of six groups of start cooling temperatures and final cooling temperatures on the microstructure and tensile properties of the test steel was studied.The results show that the matrix microstructures of the test steel all consisted of bainite+ferrite+martensite/austenite(M/A)island at six groups of cooling temperatures.At the same finish cooling temperature,when the start cooling temperature decreased,the ferrite content in the test steel increased significantly and the M/A island content increased slightly;the yield ratio decreased.At the same start cooling temperature,when the finish cooling temperature decreased,the ferrite conten decreased slightly while the M/A island content increased obviously;the yield ratio increased.When the start cooling and finish cooling temperatures were lowered at the same time,the content of ferrite and M/A island increased synchronously,but the increase in M/A island content was smaller;the yield ratio decreased.The test steel had the best tensile properties at the start cooling temperature of 755℃and finish cooling temperature of 395℃.