Reason for Leakage of Fillet Weld Between U-tube of Final Superheater and Stainless Steel Hanging Plate
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摘要: 某电厂末级过热器12Cr1MoVG铁素体钢U型管与1Cr20Ni14Si2奥氏体钢吊挂板连接角焊缝在长时间运行条件下发生泄漏。通过宏观观察、成分分析、显微组织观察和硬度测试等方法对该角焊缝泄漏原因进行了分析。结果表明：U型管与吊挂板连接角焊缝边缘存在未焊全缺陷，焊缝内存在夹渣缺陷，在这些缺陷位置处应力集中现象明显；同时U型管侧熔合线位置存在碳迁移现象，导致硬度增大、塑性下降，在应力集中作用下，熔合线位置萌生裂纹并不断扩展，最终造成角焊缝的开裂失效。Abstract: The leakage of fillet weld between 12Cr1MoVG ferritic steel U-tube of final superheater and 1Cr20Ni14Si2 austenitic steel hanging plate of a power plant occurred during long-term running. The reason for leakage of the fillet weld was analyzed by macroscopic observation, composition analysis, microstructure observation and hardness measurement. The results show that incompletely filled grooves were observed at the edge of the fillet weld between U-tube and hanging plate, and slag inclusions existed in the weld. At these defect positions, stress concentration was obvious. Meanwhile carbon migration occurred at fusion line on U-tube side, resulting in the increased hardness and decreased plasticity. By the stress concentration, the cracks originated at the fusion line and propagated continuously, and finally led to the cracking failure of the fillet weld.
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Keywords:
- dissimilar metal welding /
- fillet weld /
- carbon migration /
- failure analysis
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