钢轨气压焊接头光斑缺陷研究

doi:10.11896/cldb.20060040

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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.

Key words： rail gas pressure welding white spot

Published: 03 August 2021

CLC number:

TG453

Fund:National Key R&D Program of China (2017YFB0304500).

About author:: Xiao Zheng, master of Southwest Jiaotong University, graduated from the school of materials science and engineering of Southwest Jiaotong University in June 2017 (undergraduate). From July 2017 to now, he studied at Southwest Jiaotong University, and his main research direction is rail welding.
Hong Dai, Professor of Southwest Jiaotong University, master's supervisor, expert enjoying special allowance of the State Council. In 1982, she graduated from Harbin University of Technology, majoring in metal mate-rials and heat treatment. In June 1985, she obtained a master's degree in engineering from Harbin University of technology. From 1987 to now, she mainly carried out the research and development of complete sets of technical equipment for rail welding automation and quality control, overcoming the key technical problems of rail welding series such as rail flash welding, numerical control pneumatic welding, etc., and has profound attainments and influence in the field of rail transit welding. She is the leader of China's railway welding technology. She has successively presided over many major projects of the state and the Ministry of railways,
especially the independent innovation major scientific and technological project of the Ministry of Railways “numerical control pneumatic rail welding vehicle”, which has become the world's first landmark achievement of modern rail welding equipment, and has been fully approved by General Secretary Hu Jintao; in 2010, she has achieved great success in the application of the Qinghai Tibet Railway seamless rail speed-up project. 11 patents have been authorized, and more than 60 papers have been published in core journals. She has won 1 National Science and technology progress award, 4 provincial and ministerial science and technology progress awards and teaching achievement awards. She has won many honors, such as the locomotive Medal of the Ministry of railways, excellent young teachers of Chengdu, excellent teaching management cadres of Sichuan Province, new Long March commando of Sichuan Province, excellent graduate tutor, etc.

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Cite this article:

ZHENG Xiao,DAI Hong. Research on White Spot Defect of Rail Gas Pressure Welded Joint[J]. Materials Reports, 2021, 35(14): 14142-14149.

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http://www.mater-rep.com/EN/10.11896/cldb.20060040 OR http://www.mater-rep.com/EN/Y2021/V35/I14/14142

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