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通对某超超临界锅炉在安装期间发现裂纹的水冷壁鳍片和管子进行化学成分、机械性能、示波冲击、显微硬度、金相组织、断口形貌试验等分析,得出鳍片部位存在折叠和微裂纹等轧制原始缺陷。诱发鳍片与管子焊接过程中产生裂纹并扩展的主要原因是鳍片硬度高、脆性大,而且存在原始缺陷;次因之一是鳍片与管子的焊接质量差、氧气切割时产生热应力,在切开的尖锐的直角缺口部位产生较大的应力集中,导致鳍片在缺口处开裂并扩展;次因之二是水冷壁管屏在生产工地到安装工地的吊装及运输过程中在二次应力的作用下产生多次振动和冲击,在裂纹的启裂部位产生弯矩和扭矩,导致裂纹迅速开裂并扩展。
Through the analysis of the chemical composition, mechanical properties, oscillometric impact, microhardness, microstructure and fracture surface morphology of the water wall fins and pipes found cracks during the installation of an ultra-supercritical boiler, There are rolling defects such as folding and microcracking. Induced fins and pipes in the process of welding cracks and expansion of the main reason is the high hardness of the fins, large brittleness, and the existence of the original defects; one of the reasons is the poor quality of welding fins and tubes, oxygen cutting thermal stress, Resulting in greater cracking of the fins at the notches and expansion of the fins. The second reason is that during the lifting and transportation of the water-cooled wall panels from the production site to the installation site, Under the action of stress, multiple vibrations and impacts are generated, bending moments and torques are generated at the crack initiation site, causing the crack to crack and expand rapidly.