In this study, a failure in a high pressure steam pipeline, made of ASTM A335 P11 steel grade, has been investigated. The failure in this case appeared in the form of cracking in a 16 inch pipe, containing high pressure steam (47 bar) at 400 °C after eight years of service, which is considered as a relatively premature failure in comparison to the design service-life of the pipeline. Optical and electron microscopies were employed to investigate the microstructure of the failed pipe. Hardness measurement was also conducted to measure the hardness of samples. Results indicated that the main mechanism of the failure was stress-relaxation cracking (SRC). Formation of coarse carbide precipitates at grain boundaries appears to have a vital attribution to this failure. Failure mechanism and mitigation strategies are discussed in this paper.

在这项研究中，对由 ASTM A335 P11 钢级制成的高压蒸汽管道的故障进行了调查。在这种情况下，故障以 16 英寸管道破裂的形式出现，其中含有 400 °C 的高压蒸汽（47 巴），使用八年后，与设计服务相比，这被认为是相对过早的故障-管道的寿命。光学和电子显微镜被用来研究失效管道的微观结构。还进行硬度测量以测量样品的硬度。结果表明，失效的主要机制是应力松弛开裂（SRC）。在晶界处形成粗大的碳化物沉淀似乎是这种失效的重要原因。本文讨论了失效机制和缓解策略。