Grade 700 rails that used to be the main product for railroads some 60 years ago, may be considered as the starting point for the development which since took place. The Grade 700, with about 0.5% C, has a microstructure of about 30% ferrite and 70% pearlite within the rail head, which is the relevant location for comparison.
The first step to raise strength, and consequently wear resistance, was to increase the carbon content to achieve a 100% pearlitic microstructure. This way Grade 900 rails were developed.
Category Archives: Rail Steel
Rail Steels: Part One
Modern railway systems are subjected to intense use, with fast trains and increasing axle loads. Rails have to be more wear resistant and achieve higher standards of straightness and flatness in order to avoid the surface and internal defects which may lead eventually to failure. The shape of the manufactured rail depends to a large extent on the uniformity of thermo mechanical processing; the most advanced mills are computer controlled with continuous feed-back from the product during manufacture.