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应用光学显微镜、扫描电镜等手段,对奥氏体焊条焊接HK—40炉管和1Cr5Mo法兰的异种焊接接头在长期高温服役期间开裂泄漏的失效原因进行了分析,结果表明在长期高温服役中碳扩散迁移,在熔合区邻近1Cr5Mo钢母材侧形成脱碳层;其基体因贫碳软化,强度降低,加上1Cr5Mo钢和奥氏体焊缝金属的线膨胀系数有较大差异.高温下变形不协调,熔合区存在应力集中,导致在脱碳层这个薄弱部位萌生裂纹并沿其扩展,穿透内外壁,造成泄漏。
The failure causes of cracking and leakage of austenitic welding rod welding HK-40 furnace tube and 1Cr5Mo flange during long-term high temperature service were analyzed by means of optical microscope and scanning electron microscope. The results showed that in the long-term high-temperature service carbon Diffusion and migration, forming a decarburized layer on the base metal side of the 1Cr5Mo steel in the fusion zone; the matrix is softened due to lean carbon and the strength is reduced, and the linear expansion coefficients of 1Cr5Mo steel and austenitic weld metal are quite different. Uncoordinated, there is stress concentration in the fusion zone, which leads to the initiation of cracks in the weak part of the decarburized layer and its expansion along the inner and outer walls, resulting in leakage.