Abstract：Rails of passager Line are parted at the time straightening after rails are welded in the rail welding plant. Fracture cause are analysed by optical microscope and TEM. The results show that fracture reasons is boss defect existed at the end of the edge of rail，and cold crack is caused when the boss is shovelled smooth by tumor knife，rail is breaked off at last.Rails are kept straight when rails are rolled in finishing by means of controlling roll diameter difference and rolling line height and so on.Upturned or bend down are avoided，and thus boss defect are eliminated.
2011, Vol. 46 
