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微合金化元素对离心铸造炉管焊接接头组织和性能影响

Effect of microalloying elements on the microstructural evolution and mechanical properties of weld joints of centrifugally cast furnace tubes

  • 摘要: 针对添加Ti,W等微合金化元素的离心铸造炉管焊接接头,研究了微合金元素对焊接接头组织和力学性能影响规律及作用机理.结果表明.在1 050℃、14~25 MPa条件下,使用Ti和W元素微合金化的25Cr35NiNb和35Cr45NiNb炉管焊接接头高温性能显著高于未微合金化焊接接头.微合金元素Ti显著影响炉管焊接接头组织,Ti元素含量高的焊接接头原始焊态组织中含NbTiC,经过高温时效后,组织中含铌相主要为NbTiC,在蠕变空洞周围局部转变为G相(Ni16Nb6Si7);Ti元素含量低的焊接接头原始焊态组织中含NbTiC和NbC,经过高温时效后全部转变为G相.微合金元素W主要通过固溶强化的方式,提高炉管焊接接头的高温性能.

     

    Abstract: Microstructural evolution and mechanical properties of weld joints of centrifugally cast furnace tubes with different contents of Ti and W are investigated via field emission scanning electron microscopy (FESEM) equipped with energy-dispersive X-ray spectroscopy, tensile testing machine and creep testing machine. The results show that high temperature performance of weld joints of 25Cr35NiNb+MA (micro alloy) and 35Cr45NiNb+MA furnace tube with addition of Ti and W is significantly higher than that of the weld joints without Ti and W. Micro alloying element Ti significantly affects the microstructures of weld joints. The microstructure of the original welded joints with high Ti content is NbTiC, and it partially transformed to G phase (Ni16Nb6Si7) during aging, which has poor creep resistance. Both NbTiC and NbC are present in the original welded joints with low Ti content, which totally transformed to G phase after high temperature aging. Micro alloying element W could improve high temperature performance of weld joints by solid solution strengthening.

     

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