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Track materials Rails Mechanical and electrical properties Page: 211-06 Yield ratio for different rail grades Yield point (Rp0,2) [N/mm2] Tensile strength [N/mm2] The electrical conductivity is dependent on the chemical compositions of the rail steels, in particular the Si-content. In the rail steels R200, R220, R260, R260Mn and R320Cr, the following values for the electrical conductivity can be observed: R200 R220 R260/Mn R320 Cr 4.6 - 4.8 Sm/mm² 4.4 - 4.7 Sm/mm² 4.3 - 4.6 Sm/mm² 3.0 - 3.3 Sm/mm² Continuous welded rail: Rails were formerly connected with tabs. There must be an expansion gap considered for the thermal expansion. Today, modern rail track systems are welded. They are called completely welded rails. The forces generated by the thermal expansion are taken up by the rail fastening and discharged over the threshold into the gravel track. Change in rail length ΔL due to temperature change: ΔL = L0 x ΔT x α L0 ΔT α = Rail length in mm = Temperature change in °C = Expansion coefficient for steel: approx. 0.000012 [-] Example: L0 = 120,000 mm ΔT = 60 °C ΔL = 120,000 x 60 x 0.000012 = 86.4 mm Without scale/schematic diagram Date of issue 08/10