在超声测厚过程中,某Q345R钢制压力容器在多处厚度存在异常,通过化学成分分析、力学性能试验和显微组织观察等方法,对压力容器厚度异常部位的内部缺陷进行分析。结果表明:压力容器厚度异常部位的锰含量偏高,导致其厚度中心位置出现大量MnS夹杂物和贝氏体、马氏体等异常过冷组织,在制造过程中,由于受到外力或热加工过程中温度应力作用,在过冷组织内部夹杂物位置处和过冷组织与铁素体界面处会产生应力集中,从而导致微裂纹形成。

In the ultrasonic thickness mesurment process,the thickness of a Q345R steel pressure vessel in many places was abnormal.The internal defects of abnormal thickness part of pressure vessel were analyzed through chemical composition analysis,mechanical performance test and microstructure observation.The results showed that the manganese content in abnormal thickness of pressure vessel was too high,resulting in a large number of MnS inclusions and abnormal supercooled structures such as bainite and martensite in center of thickness.During the manufacturing process,due to external force or temperature stress during thermal processing,stress concentration occurred at the location of inclusions in supercooled structure and the interface between supercooled structure and ferrite,resulting in the formation of microcracks.