Patent ID: 6770155
Filing Date: 2004-08-03
Classification: C21D

Abstract:
A process for the manufacture of a railroad rail of a steel alloy having a pearlitic microstructure, which rail has a weight of 30 to 100 kg/m, good long-term serviceability, high ductility and high abrasion resistance of the working surface at a rail head, wherein a rail which has a chemical composition in weight % ofcarbon (C)0.4 to 1.0silicon (Si)0.1 to 1.2manganese (Mn)0.5 to 3.5chromium (Cr)up to 1.5,optionally other alloy elements below 1 weight %, the rest being iron (Fe) and impurities occurring in the manufacturing process, is shaped, during a last pass of a multiple longitudinal rolling, at a reduction rate of 1.8 to 8% and aligned straight in its longitudinal direction at a temperature between 770Â° C. and 1050Â° C., whereafter the rail is mounted in a vertically suspended position with its head down and is allowed to cool slowly in still air to a temperature of 5 to 120Â° C. above an Ar3 temperature at a rate of 3Â° C./min, and upon reaching this temperature at least the rail head is dipped, in its entire longitudinal extension, into a cooling liquid and is cooled, within a range between 800Â° C. and 450Â° C., with increased cooling intensity and at a rate of 1.6 to 2.4Â° C./s, to a temperature of conversion of an austenitic grain microstructure into a fine pearlitic grain microstructure, followed by lifting the rail out of the cooling liquid, placing it onto a cooling bed and allowing it to cool slowly in still air.