高参数大型电站锅炉集箱裂纹检验及分析

Inspection and Analysis of Cracks in Headers of a High Parameter Large-sized Utility Boiler

某大型电站锅炉安装过程中,通过磁粉探伤检测发现后烟井下集箱连接管管座角焊缝发生严重裂纹。首先对集箱、管接头、焊接材料及加工工艺进行复验,确认符合标准要求;然后对裂纹产生处切取制样,通过金相试验、硬度试验和电镜扫描试验对试样的微观组织形貌进行分析研究。试验结果表明:裂纹的性质为再热裂纹。为防止此类裂纹的产生,应对集箱焊接及焊后热处理工艺进行优化,适当提高了焊接预热温度采用对称施焊从而提高集箱制造的合格率。

During the installation of a large-sized utility boiler,through a magnetic powder non-destructive inspection,a serious crack was found in the fillet welding seams between the connection tubes and the tube seats on the lower header in the rear flue gas well. Firstly,a recheck was performed of the header,tube connector,welding material and manufacturing process to make sure that all met the requirements set in relevant standards,then,a sample or specimen was cut and made at the location of the crack. Through a metallurgical test,hardness test and electronic microscope scanning test,the microorganization and morphology of the sample were analyzed and studied. The test results show that the crack pertains to a reheat-caused one. To avoid reoccurrence of this kind of cracks,the welding and after-welding heat treatment process of headers should be optimized,thus enhancing the eligibility rate of headers thus manufactured.