Railway Track & Structures - June 2008 - (Page 18)

TTCI R&D New rail steels for the 21st Century Superior performance through advanced alloy design and thermomechanical processing. ail is the most valuable asset owned by railroads. In North America alone, railroads spend more than $2 billion a year on rail repair and replacement. Transportation Technology Center, Inc., in Pueblo, Colo., continuously conducts rail performance tests of the most modern premium rails developed by manufacturers worldwide. These tests are conducted to assess rail performance and compare improvements, as well as differences, among the tested rails, allowing clear identification of the improvements in the newly-developed rails. Historically, improvements in rail performance were made through the addition of alloying elements, mainly carbon. For instance, rail steels during the 1960s had approximately 0.7 wt%C that was increased to 1 wt%C in the past four decades. Figure 1 sketches the above mentioned historical pathways in the carbon content additions and provides an example of the typical microstructures for rail from different generations. In addition to the benefits of increasing carbon, a head hardening process was successfully implemented during the 1990s. Both developments have resulted in outstanding improvements in rail performance with a corresponding increase in hardness from 248 HB to more than 400 HB (rails manufactured in 2001). Although current rails have excellent wear resistance, fatigueresistant improvements are required since a great portion of the rail is removed prematurely due to fatigue related issues. TTCI is developing a new rail steel that possesses superior wear resistance properties with significantly higher fatigue resistance. Under the scope of this new rail development, TTCI has identified the presence of proeutectoid cementite on the prior austenite grain boundaries as the main factor that may have negative effects in fracture toughness, elongation, fatigue and wear resistance of pearlitic rail steels. TTCI is working in R Figure 1 is the Fe-C phase diagram showing the common phases present on the steel microstructure and the approximate carbon content for the respective rail generations. collaboration with researchers from the University of Pittsburgh. As part of this project, the microstructure of 13 premium rails from previous generations and the current generation was investigated and compared. Currently TTCI’s focus is on the analysis and understanding of the microstructure (interlamellar spacing, pearlite colony size and prior austenite by Francisco C. Robles Hernandez, TTCI principal investigator, Raymundo Ordoñez Olivares and Professors C. Isaac Garcia and Anthony DeArdo, University of Pittsburg Engineering PHDC www.rtands.com 18 Railway Track & Structures June 2008 http://www.aar.com http://www.rtands.com

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Railway Track & Structures - June 2008 Contents On Track Industry Today Supplier News AREMA News NRC News TTCI R&D Grade Crossings Provide Interface Between Railroads, Public Grade-Crossing Equipment & Materials Guide Fastener Suppliers Getting a Grip Grinding Plays Part in Rail Maintenance Big Picture Products and Literature People Calendar Sales Representatives Website Directory Advertisers Index Professional Directory Classified Advertising Chicago Perspective

Railway Track & Structures - June 2008

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