Abstract: 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 stu-died. 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 bon-ding 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.
郑霄, 戴虹. 钢轨气压焊接头光斑缺陷研究[J]. 材料导报, 2021, 35(14): 14142-14149.
ZHENG Xiao, DAI Hong. Research on White Spot Defect of Rail Gas Pressure Welded Joint. Materials Reports, 2021, 35(14): 14142-14149.
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2021, Vol. 35 
