Causes for Weld Seam Performance Nonconformance and Spot Defect of SAWL Pipe
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摘要: 针对直缝埋弧焊管焊缝出现低温冲击韧性不合格、导向弯曲不合格及内焊缝近表层点状缺陷，分析了钢板原料成分及缺陷发生处的宏观形貌和金相组织。分析认为：为降低成本，调整了L485M 母材化学成分，使后来批次的母材合金元素中不含Mo 元素，为保证焊缝的冲击韧性，制管厂应当选择合适的焊丝进行匹配，以调整焊缝化学成分的含量；在保证焊缝熔透量的情况下，尽量使用小的焊接热输入量，使焊接后冷却凝固的熔池金属得到理想的组织成分和晶粒组织。Abstract: Addressing the nonconformance concerning low temperature impact toughness and guided bending,and the near surface spot defects as developed in the weld seam of the SAWL pipe,the blank steel plate chemical composition,and the macro-morphology and metallographic structure of the metal where the said defects present are analyzed. Based on the analysis,actions as follows should be taken:adjusting the chemical composition of the L485M base metal to get the base metal of the batches as following free of the alloy element Mo,so as to reduce the cost;determining well-matched weld wire by the pipe maker to adjust the chemical element contents of the weld seam so as to ensure the impact toughness thereof;and under the condition that the weld seam penetration is assured,trying as far as possible to use small weldingheat input amount to make the cooled down and solidified weld pool metal have ideal after-welding microstructure and grain structure as well.
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