NKK has developed a high-strength pearlitic rail named the SP (Super Pearlite) rail, which has superior wear and damage resistance and is most suitable for heavy haul railroads. Comprehensive research on the relation between microstructural factors and wear and RCF (Rolling Contact Fatigue) behaviors revealed that refining the pearlite colonies greatly improves wear and damage resistance. In the SP rail, the pearlite colonies are refined through microalloying design and TMCP (Thermo-Mechanical Controlled Processing). This paper introduces the basic properties of the SP rail including its wear and RCF behaviors as well as the concept of microstructural control.

Pearlitic steel, Colony size, Lamellar spacing, Volume fraction of cementite, Wear resistance, Damage resistance, Heavy haul railroads