L245NS钢天然气集输管线弯管开裂原因分析

Elbow Cracking Failure Analysis for L245NS Steel Grade of Gas Gathering Line

通过对输送天然气的L245NS钢热煨失效弯管断口的宏观和微观形貌观察、显微组织及力学性能的研究以及化学成分分析,探究其失效原因。结果表明:弯管材料的化学成分、硬度、拉伸和冲击性能均不能满足标准要求,弯管内弧、外弧的显微组织分别为贝氏体+铁素体,铁素体+马氏体,马氏体组织导致材料硬度偏高、表面缺陷处应力集中,致使弯管开裂失效。

In order to investigate the reason of heat- bending elbow cracking failure of L245NS steel grade, the leaked bend was tested by macroscopical and microcosmic fracture morphology analysis, microstructure examination, mechanical property and chemical composition analysis. Results showed that the chemical composition, tensile property, impact property and hardness did not meet the standards. It also revealed that the inside arc was bainite and ferrite while the outer arc was ferrite and martensite. Martensite resulted in higher hardness of the steel and the stress concentration occured in surface defects, which led to the elbow cracking.