E690钢奥氏体化过程的内耗分析

利用内耗法并结合硬度测试与显微组织分析,研究了奥氏体化过程加热温度与保温时间对E690钢碳化物溶解量的影响。结果表明:奥氏体化温度低于Ac₃时,升高温度可以显著增加淬火钢的SKK峰值,钢中碳化物的溶解量增加;当奥氏体化温度高于Ac₃时,升高温度与延长保温时间使淬火钢的SKK峰值变化不明显,钢中碳化物的溶解程度较高。另外,延长保温时间会造成淬火态试样板条状马氏体组织粗化,奥氏体化保温5 min可以使得钢中碳化物接近完全溶解,淬火态试样显微组织为板条分布较细小的状马氏体。因此,可以通过在高于Ac₃点的适当温度保温较短时间进行奥氏体化来提高调质热处理的效率。

Internal friction analysis on austenitizing process of E690 steel

Effect of austenitizing temperature and holding time on carbides dissolved amount of E690 steel was studied by means of measuring internal friction, hardness testing and microstructure analysis. The results show that, when the austenitizing temperature is lower than Ac₃ point, the strength of SKK peak can be significantly increased with the increase of temperature, and the dissolved amount of carbides is also increased. When the austenitizing temperature is over the Ac₃ point, the strength of SKK peak does not change obviously with the increase of temperature and holding time, the degree of carbide dissolution in the steel is relatively high. Besides, the structure of coarsened martensite can be observed by the process of an extended holding time. The carbides in the steel can completely be dissolved during austenitizing for 5 min, in which the microstructure is a martensite with a relatively small distribution of strips. Therefore, it is feasible that the efficient of quenching and tempering is improved through selecting shorter holding time when the temperature is appropriately over Ac₃ point.