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焊接方法对1000MPa级熔敷金属组织及力学性能的影响

Effect of welding methods on microstructure and mechanical properties of 1 000 MPa grade deposited metal

  • 摘要: 在相同热输入下分别采用熔化极活性气体保护焊(MAG)和钨极氩弧焊(TIG)进行1 000 MPa级熔敷金属试验,通过光学显微镜、透射电镜及断口分析等手段研究焊接方法对其组织和性能的影响. 结果表明,MAG焊熔敷效率明显高于TIG焊,MAG焊中出现了明显的"指状熔深". MAG焊熔敷金属及道间热影响区组织明显较TIG焊粗化. TIG焊熔敷金属组织细化、分布取向多样化且均匀分布的较多残余奥氏体是TIG焊低温冲击韧性优异的原因之一;MAG焊中生成大量非金属夹杂物易成为解理断裂起裂源,是导致熔敷金属冲击韧性恶化的因素之一. TIG焊力学性能明显优于MAG焊,这与焊接方法所导致的组织构成及夹杂物有直接关系.

     

    Abstract: With the same heat input, deposited metals were welded with 1 000 MPa grade solid welding wire as filler material by MAG (Metal Active Gas) and TIG welding methods, respectively. The effects of welding methods on microstructure and properties of deposited metals were studied by means of optical microscopy, transmission electron microscope (TEM) and fracture analysis etc. The results show that the deposition efficiency of MAG is significantly higher than TIG, and there is a clear "finger penetration" in MAG weld bead. The microstructure of primary weld region and reheated weld region of MAG deposited metal is significantly coarsing than TIG. TIG diposited metal has more refinement microstructure. The distribution is diversification and it includes more uniform distribution of retained austenite, which is one of the reasons for excellent low-temperature impact toughness. Besides, a large number of non-metallic inclusions in the MAG diposited metal, which is the initiation source of cleavage fracture. Therefore, non-metallic inclusion is another reason for deterioration low temperature impact toughness of MAG diposited metal. The results show that the integrated mechanical property of TIG diposited metal is much better than MAG, which is generated by the welding method for different microstructure type, morphology and characteristic of the non-metal inclusion.

     

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