Carbon-titanium steel rail
View Patent ↗An improved steel railroad rail, and methods for producing same, having a carbon content in a range from 0.7 to 0.95 wt % and titanium in the range of 0.005 to 0.105 wt % is provided that has increased wear resistance and increased fracture toughness over conventional steel rail. The rail is characterized as having a pearlitic phase of an eutectoid nature. The average ultimate tensile strength is in a range from 178,000 to 207,000 psi, with a minimum of 174,000 psi. The average yield strength is in a range from 122,000 to 141,000 psi, with the minimum of 120,000 psi. The average percent elongation is in a range from 10.3 to 12.5, with a minimum of 10.00. The Brinell hardness on the surface at any position of the head top and upper gage corners of the rail is in a range from 370 to 420 BHN. The hardness 19 mm below the top surface is in a range from 360 to 405 BHN and 19 mm below the surface at the upper gage corners is in a range from 360 to 410 BHN. The characteristics of the steel rail produced in accordance with the present invention is a substantial improvement as compared with rail used today. The production of a fully pearlitic steel rail having a carbon content from 0.7 to 0.95 wt % and titanium in the range of 0.005 to 0.105 wt % Ti is remarkable and unexpected. A steel rail of this type having a hardness in a range from 370 to 420 BHN and a combination of yield strength, ultimate tensile strength, elongation and surface and in-depth Brinell hardness goes beyond all expectations and results in a superior and commercially important steel rail.
1. A method for manufacturing a fully pearlitic steel rail of high toughness and high wear resistance consisting essentially of:
forging a steel billet comprising the elements in a range from 0.7 to 0.95 wt % of C, 0.005 to 0.105 wt % of Ti, 0.26 to 0.80 by wt % of Si, 0.8 to 1.2 wt % of Mn, less than or equal to 0.35 wt % of Cr, the balance of iron and residual elements;
hot rolling the billet such that the rolling finishing temperature is about 1000.degree.C, thereby forming a rail; and
heat treating by cooling the rail at a cooling rate in a range from 3.3.degree.C./sec to 4.3.degree.C./sec. beginning substantially at said rolling finishing temperature and continuing to at least 480.degree.C. at which point the rail is released from heat treating.
2. The method according to claim 1 , wherein the steel comprises a maximum of each of the elements 0.45 wt % of Cu, 0.25 wt % of Ni, 0.05 wt % of Mo, 0.025 wt % of 5, and 0.01 wt % of Al.
3. The method according to claim 1 , wherein the steel further comprises vanadium in a range from 0.0 to 0.020 wt %.