780DP高强汽车钢等温过程中的组织变化分析

Analysis on Microstructure Change of 780DP High Strength Automobile Steel during Isothermal Process

汽车结构的轻量化是实现汽车节能环保最为有效的途径。采用管式电阻炉对780DP高强汽车钢进行热处理试验,研究了等温温度和等温时间对钢的组织演变和维氏硬度的影响规律。结果表明,在780~840℃等温10~300 s热处理条件下,基体组织仅发生回复,同时伴随铁素体向奥氏体的转变。随着保温时间的延长和等温温度的升高,淬火后得到的马氏体体积分数不断增加。随着保温时间的延长,试验钢的维氏硬度由于等温过程中的回复与马氏体体积分数的变化而先下降再升高。

The lightweighting of automobile structure is the most effective way to realize energy saving and environmental protection of automobile. Heat treatment test of 780DP high strength automobile steel was carried out by tube resistance furnace, the effects of isothermal temperature and isothermal time on the microstructure evolution and Vickers hardness of steel were studied. The results show that the matrix structure only recovers and accompanies by the transformation of ferrite to austenite at 780-840℃ for 10-300 s isothermal heat treatment. With the prolongation of holding time and the increase of isothermal temperature, the volume fraction of martensite increases continuously. With the prolongation of holding time, the Vickers hardness of the experimental steel decreases first and then increases due to the change of the recovery and martensite volume fraction during isothermal process.