热处理对稀土5Cr钢组织及析出相的影响

以稀土5Cr钢为对象,研究了热处理工艺(870、900、930 ℃保温50 min水淬,670、690、710 ℃保温90 min回火)对其组织及第二相析出行为的影响。结果表明,试验钢经870 ℃淬火后,组织未完全奥氏体化;随着淬火温度的升高,试验钢完全奥氏体化,原始奥氏体平均晶粒尺寸从900 ℃的13.49 μm增大到930 ℃的15.01 μm,且组织均匀性明显下降。合适的淬火温度为900 ℃。在670~710 ℃回火后,组织分布为回火屈氏体、回火屈氏体+回火索氏体、回火索氏体。回火后第二相为分布在基体上的Cr₇C₃碳化物及在界面聚集的Cr₂₃C₆碳化物。随着回火温度的升高,Cr₂₃C₆碳化物比例逐渐增加。为避免回火过程中M₂₃C₆型碳化物的聚集和粗化,合适的回火温度为690 ℃。

Effect of heat treatment on microstructure and precipitates of 5Cr steel with RE addition

Taking 5Cr steel with RE addition as the object, the effect of heat treatment (water quenching at 870, 900, 930 ℃ for 50 min , and then tempering at 670, 690, 710 ℃ for 90 min) on microstructure and second-phase precipitation behavior of the tested steel was studied. The results show that after quenching at 870 ℃, the structure is not completely austenitized. The tested steel is completely austenitized with the increase of quenching temperature, and the prior-austenite average grain size is increased from 13.49 μm at 900 ℃ to 15.01 μm at 930 ℃, while the microstructure uniformity is obviously reduced. By selecting the proper quenching temperature as 900 ℃, and after tempering at 670-710 ℃, the microstructure is tempered troostite, tempered troostite + tempered sorbite and tempered sorbite in turn. The second phases after tempering are Cr₇C₃ carbide distributed on the matrix and Cr₂₃C₆ carbide aggregated at the interface. With the increase of tempering temperature, the proportion of Cr₂₃C₆ carbide increases gradually. In order to avoid the aggregation and coarsening of M₂₃C₆ carbides during tempering, the appropriate tempering temperature is 690 ℃.