钢轨气压焊接头光斑缺陷研究  

Research on White Spot Defect of Rail Gas Pressure Welded Joint

作　　者：郑霄 戴虹[1] ZHENG Xiao;DAI Hong(School of Materials Science and Engineering,Southwest Jiaotong University,Chengdu 610031,China)

机构地区：[1]西南交通大学材料科学与工程学院,成都610031

出　　处：《材料导报》2021年第14期14142-14149,共8页Materials Reports

基　　金：国家重点研发计划(2017YFB0304500)。

摘　　要：钢轨气压焊接头的典型缺陷是光斑缺陷。遗憾的是,迄今为止还没有深入研究光斑缺陷系统的报道。本工作采用落锤试验、光学显微镜(OM)、扫描电镜(SEM)、能谱分析(EDAX),对工地收集的带缺陷气压焊接头和验证试验接头进行了系统分析,研究了钢轨气压焊光斑缺陷的形貌特征和分类,阐述了光斑产生的机理。结果表明,气压焊光斑缺陷依据该部位是否发生了交互结晶的焊接冶金机理,可细分为完全未焊合型和部分焊合型两类。完全未焊合型光斑是待焊面被氧化物、油污、砂粒等污染物重度污染所致,部分焊合型光斑是轻度污染或欠热所致。完全未焊合型光斑缺陷的宏观断口特征为平齐、光亮、光滑(无毛刺感);其微观形貌为形状不一的团絮污染物,或焊前端面处理痕迹,有时有锈蚀斑;金相观察呈微裂纹。部分焊合型光斑缺陷的宏观断口特征是为平齐、发灰、粗糙(有细毛刺感);其微观形貌为细小韧窝与河流花样共存;金相观察呈细小晶粒,无微裂纹。钢轨气压焊接头轨底部位若存在完全未焊合型光斑缺陷,落锤性能将达不到标准要求,因此焊轨过程中应严格控制端面的清洁度。The typical defect of rail gas pressure welded joints is white spot defects.Unfortunately,no research of white spot to date has been reported systematically and in deep.In this paper,drop hammer test,optical microscope(OM),scanning electron microscope(SEM)and energy spectrum analysis(EDAX)were used to systematically analyze the gas pressure welded joints with defects collected from the construction site and verification test joints.The morphology,classification and production mechanism of white spot defects in rail gas pressure welding are studied.The results show that the white spot of gas pressure welding can be divided into partial bonding and completely not bonding white spot according to the welding metallurgical mechanism.The completely not bonding is caused by the contamination of oxide,oil and sand.Partial bonding is caused by mild pollution or under heating.The macroscopic characteristics of completely not bonding are flat,bright and smooth(without burr),sometimes with rust;the micromorphology is floc contaminant with different shapes,or the grinding marks before welding;metallographic observation shows microcracks.The macroscopic characteristics of partial bonding are flat,gray and rough(with burr);the micromorphology is the coexistence of small dimples and river pattern;the metallographic observation shows fine grains without microcracks.If there are completely not bonding at the rail bottom of rail gas pressure welded joint,the drop hammer performance will not meet the standard requirements.Therefore,the cleanliness of the end face should be strictly controlled in the process of rail welding.

关 键 词：钢轨 气压焊 光斑 

分 类 号：TG453[金属学及工艺—焊接]