U71Mn钢闪光-摩擦复合焊接头组织及性能研究

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Abstract：Flash buttwelding （FBW） is widely used inrail welding because of its high eficiencyand excellent characteristics. However，there are stillsome problems in the welded joints，such as gray spot defects and weld decarburization， whichcan not be completely solved.To address this problem，flash-friction hybrid welding （F-FHW） has beendeveloped.In this paper，U71Mn steel was welded by flash-friction hybrid welding，and compared with flash welding，and the influence laws of the two welding methods on the microstructure，temperature field and properties were studied.The results indicate that the weld ofF-FHW welding can obtain a metal microstructure close to that of the base metal； The grain size offlash weld is grade1 with anaverage grain diameter of about

350um，while F-FHWis grade 2.5 with anaverage grain diameter of about200um. The high temperature of the FBW welding isconcentrated inthecentralarea，andthedistributionof the high temperature zoneintheF-FHW welding temperature field is more uniform；The hardness ofFBW shows a significant decrease and is slightly lower thanthatofthe base material，while the hardness distributionofF-FHWjoints is uniformandhigherthanthatof the base material.The impact fracture morphology of FBW weld is cleavage plane with asmallamount of toughness dimples，and a smallamount of gray spots are found. The impact fracture morphology of F-FHW weld is cleavage plane and no gray spots are found.

Keywords：F-FHW；FBW；microstructure；temperature field；hardness； impact

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高速铁路在便利出行、促进经济发展等方面具有重要作用，而作为其重要组成部分的无缝钢轨，其连接的平顺、安全、稳定性对整体系统至关重要[1。（剩余5338字）