中文摘要：

经济发展使寒冷地区铁路建设大规模开展,而钢轨长期低温服役,力学性能会受到影响.钢轨铝热焊缝接头同钢轨钢材一样,在低温下其冲击韧性变差,容易发生脆性断裂,因此需要对低温下的冲击韧性进行研究.在＋20～-60℃温度范围内测量了我国常用钢轨焊剂ZTK-I（60U71Mn）型和ZTK-I（60U75V）型的U型缺口冲击功,试验结果显示2种焊缝的冲击功均随温度的降低而降低,同时在各个温度段的冲击功绝对值都较小.同时利用电镜扫描对微观形貌进行分析,显示出焊缝接头的脆性特征.研究结果表明：焊缝接头的韧性相对较差,铝热焊缝接头技术尚有继续研究改进之处.

英文摘要：

Economic advancement makes railway construction develop on a large scale in low-temperature regions,while the rail services for a long time,whose mechanical properties are effected.The same as rail steel,the impact toughness of thermit welding joints gets worse at a low temperature and brittle fractures happen more easily,so it is necessary to study on it.The U-notched impact energy of rail welding flux ZTK-I（60U71Mn） and ZTK-I（60U75V） is measured from ＋20℃ to-60℃.It reveals that the impact energy of both of them descends with the temperature,and the absolute value of the impact energy always keeps on a low level. The micro-morphology of impact fracture is analyzed using the scanning electron microscope,and it shows the brittle feature of welding joints. According to the study results, the toughness of rail welding joints is relatively poor, and the technology of thermit welding joints needs to be researched and improved.