稀土微合金700MPa级高强钢卷取过程中的组织和硬度

Microstructure and hardness of rare earth microalloyed 700 MPa grade high strength steel during coiling

研究了稀土La对低合金高强钢热轧组织和硬度的影响。利用金相显微镜、透射电镜、显微硬度仪、X射线衍射仪等,对添加La含量不同的两种成分钢的显微组织、析出相进行了表征和分析。结果表明:添加0.003%的La,能促进针状铁素体的形成和细小碳氮化物的析出,使得组织均匀细化。采用在600℃卷取然后以6℃/s冷速冷却35 s到400℃后水冷的工艺,得到的试样硬度最高,且析出的第二相数量最多。

Influence of rare earth La on aged microstructure and hardness of hot-rolled low alloy high strength steel during coiling.The microstructure and precipitates of the tested steels with different contents of La were characterized and analyzed by using optical microscope,transmission electron microscopy,microhardness tester and X-ray diffraction meter.The results show that when added 0.008% La,the formation of acicular ferrite and precipitation of fine carbonitrides were promoted,and the microstructure is fine and uniform.When coiled at 600 ℃ then cooled with 6 ℃/s for 35 s to 400 ℃,the tested steels can obtain high hardness and the precipitates is at the most.