在意大利引进的回路组装过程中,发现一条回路试验段出口处管道的内壁有微裂纹,该回路在意大利已运行过7000小时。为弄清裂纹的性质及来源而进行本试验。试验通过宏观、微观检查,化学成分分析,夹杂物性质分析,力学性能复验等,揭示出初始缺陷形成于材料成型中,在使用中逐渐扩展成裂纹。 During the assembly of the circuit introduced in Italy, it was found that there was microcracking on the inner wall of the pipe at the exit of a circuit test section which had been operating in Italy for over 7000 hours. This experiment was conducted to understand the nature and origin of cracks. The test reveals that the initial defects are formed in the material forming through the macroscopic and microscopic examination, the chemical composition analysis, the analysis of inclusion properties and the re-inspection of the mechanical properties, and gradually expand into cracks during use.