| 摘要 |
PURPOSE: To produce a high strength rail excellent in surface damage resistance by forming a pearlitic structure having high ductility and high toughness in the part from the railhead top to the inner part. CONSTITUTION: At the time of rolling a rail steel bloom, first-stage finish rolling is performed at 850-1050 deg.C railhead surface temp., and then within 10sec to 2min second-stage finish rolling by one pass or plural passes is done at a draft of <=10% per pass. Subsequently, rapid cooling is started within 0.1-10sec and the region of <5mm, starting from the surface under the surface of the railhead and corner part, is temporarily cooled down to a temp. not higher than the Ar1 transformation point, and third-stage finish rolling by one pass or plural passes is carried out at a draft of 10-20% per pass. After the surface temp. is recovered to a value not lower than the Ac1 transformation point by recuperation, cooling is successively done at a cooling rate of >=4 deg.C/sec by the maximum cooling rate at the surface of the railhead top. By providing a layer having high toughness and high ductility to the part ranging from the surface to the inner part, the high strength rail improved in surface damage resistance can be obtained. |
