Steel Alloys with Lower Bainite Microstructures for Use in Railroad Cars and Track.

摘要

In-line heat treatment of hot-formed steel mill products potentially offers the opportunity to achieve superior strength, ductility, and toughness at modest cost. The approach has been applied to the manufacture of railroad rail in an extremely refined pearlitic microstructure. With appropriate adjustments to chemical composition to control the transformation behavior, the approach provides a means to achieve close-to-isothermally produced bainitic microstructures of better strength, ductility, and toughness over the current pearlitic microstructure hot-formed mill products. In the railroad field, the approach appears to be applicable to the manufacture of rails, wheels, and tank car plates. This report reviews (a) the essential features of the in-line heat treatment process as it is currently applied to rails in the United States, (b) studies that have shown the value of bainitic microstructures, and (c) the characteristics of bainitic microstructures. A widely available computer code, SteCal, has been used to assess the effect of alloying additions on transformation behavior in a semiquantitative fashion. Finally, the applicability of the in-line heat treating approach for achieving bainitic microstructures in rails, wheels and tank car plates is discussed.