METHOD OF MAKING A HYPEREUTECTOID, HEAD-HARDENED STEEL RAIL

摘要

A method of making a hypereutectoid, head-hardened steel rail is provided that includes a step of head hardening a steel rail having a composition containing 0.86-1.00 wt% carbon, 0.40-0.75 wt% manganese, 0.40-1.00 wt% silicon, 0.05-0.15 wt% vanadium, 0.015-0.030 wt% titanium, and sufficient nitrogen to react with the titanium to form titanium nitride. Head hardening is conducted at a cooling rate that, if plotted on a graph with xy-coordinates with the x-axis representing cooling time in seconds, and the y-axis representing temperature in Celsius of the surface of the head of the steel rail, is maintained in a region between an upper cooling rate boundary plot defined by an upper line connecting xy-coordinates (0 s, 775°C), (20 s, 670?C), and (110 s, 550°C) and a lower cooling rate boundary plot defined by a lower line connecting xy-coordinates (0 s, 750°C), (20 s, 610°C), and (110 s, 500°C).