某电厂中压调速汽门2Cr12NiMo1W1V钢门杆断裂原因

Causes of fracture of 2Cr12NiMo1W1V steel door stem of medium pressure governing valve in a power plant

某电厂中压调速汽门2Cr12NiMo1W1V钢门杆在运行过程中发生断裂现象。采用宏观观察、化学成分分析、力学性能测试、金相检验、扫描电镜和能谱分析等方法对门杆断裂原因进行分析。结果表明:门杆断裂起源于漏气平衡孔壁处,该位置在渗氮过程中未做防渗氮保护,渗氮后材料脆性增强,进一步加剧了应力集中,在交变载荷的作用下材料形成微裂纹,并逐渐扩展至基体,最终导致门杆断裂;门杆的断后伸长率、冲击吸收能量偏低,强度偏高,韧性较差,在一定程度上加速了裂纹的扩展,缩短了门杆的使用寿命。

The fracture of 2Cr12NiMo1W1V steel door bar of medium pressure speed regulating valve in a power plant occurred during operation.The fracture reasons of the door stem were analyzed by means of macroscopic observation,chemical composition analysis,mechanical property test,metallographic examination,scanning electron microscope and energy spectrum analysis.The results show that the fracture of the door stem originated from the wall of the air leakage balance hole,which was not protected by anti-seepage nitrogen during the nitriding process.After nitriding,the brittleness of the material was enhanced,which further aggravated the stress concentration.Under the action of alternating load,the material formed microcracks and gradually expanded to the matrix,eventually leading to the fracture of the door stem.The elongation after fracture and impact absorption energy of the door bar were low,the strength was high,and the toughness was poor.To a certain extent,it accelerated the crack propagation and shortened the service life of the door bar.