High carbon steel rail with enhanced ductility
This invention relates to a high carbon steel rail with enhanced ductility comprising 0.65-1.4 mass % of carbon, 0.1-1.5 mass % of silicon, 0.01-0.4 mass % of manganese, 0.1-1.5 mass % of chromium, and 0.005-0.05 mass % of titanium, with additional allowances for Mo, Nb, V, Cu, M, Co, B, N, Ca, Mg, Zr, Al, and W, with the remainder comprising iron and the inevitable impurities, that displays a head surface hardness of at least 325 HB and a microstructure comprising at least 90% pearlite at a depth of between 2-20 mm below the rail head surface. The invention also relates to the process for manufacturing the high carbon steel rail with enhanced ductility.
1. A high carbon steel rail having a composition comprising:
0.65 mass % to 1.4 mass % C,
0.1 mass % to 1.5 mass % Si,
0.01 mass % to 0.3 mass % Mn,
0.62 mass % to 1.5 mass % Cr,
0.005 mass % to 0.05 mass % Ti, and
the remainder being Fe and inevitable impurities, without the presence of rare earth metals, wherein a rail head surface hardness is at least 325 HB, and a microstructure comprises at least 90% pearlite at a depth of between 2-20 mm below the rail head surface.
2. The high carbon steel rail as claimed in claim 1 wherein the C comprises 0.65 mass % to 0.75 mass %.
3. The high carbon steel rail as claimed in claim 1 wherein the C comprises 0.75 mass % to 0.85 mass %.
4. The high carbon steel rail as claimed in claim 1 wherein the C comprises 0.85 mass % to 1.0 mass %.
5. The high carbon steel rail as claimed in claim 1 wherein the C comprises 1.0 mass % to 1.2 mass %.
6. A high carbon steel rail having a composition comprising:
0.65 mass % to 1.4 mass % C,
0.5 mass % to 1.5 mass % Si,
0.01 mass % to 0.4 mass % Mn,
0.62 mass % to 1.5 mass % Cr,
0.005 mass % to 0.05 mass % Ti, and
the remainder being Fe and inevitable impurities, without the presence of rare earth metals, wherein a rail head surface hardness is at least 325 HB, and a microstructure comprises at least 90% pearlite at a depth of between 2-20 mm below the rail head surface.
7. The high carbon steel rail as claimed in claim 6 wherein the C comprises 0.65 mass % to 0.75 mass %.
8. The high carbon steel rail as claimed in claim 6 wherein the C comprises 0.75 mass % to 0.85 mass %.
9. The high carbon steel rail as claimed in claim 6 wherein the C comprises 0.85 mass % to 1.0 mass %.
10. The high carbon steel rail as claimed in claim 6 wherein the C comprises 1.0 mass % to 1.2 mass %.
11. The high carbon steel rail having a composition as claimed in either of claim 1 or 6 further comprising of one or more of: up to 0.5 mass % Mo, up to 0.05 mass % Nb, up to 0.3 mass % V, up to 1.0 mass % Cu, up to 1.0 mass % Ni, up to 1.0 mass % Co, up to 0.005 mass % B, up to 0.025 mass % N, up to 0.02 mass % Ca, up to 0.02 mass % Mg, up to 0.2 mass % Zr, up to 1.0 mass % Al, and/or up to 1.0 mass % W.
12. A process for manufacturing a high carbon steel having a composition as claim in either of claim 1 or 6 comprising the steps of:
forming a rail shape by rolling of an austenitic structure;
cooling of the austenitic structure of the entire rail or any portion of the rail to below a pearlite transformation temperature at a cooling rate sufficient to achieve a hardness of at least 325 HB on a surface of a rail head while generating a microstructure that comprises at least 90% pearlite at a depth of between 2-20 mm below the rail head surface, where the austenite structure prior to pearlite transformation is either the austenite structure present after the rolling process or an austenite structure developed by reheating a cooled rail to above an austenite formation temperature, and the cooling is achieved either through ambient cooling and/or accelerated cooling by spraying, immersing, and/or flowing a cooling media across the entire surface or any portion of the surface of the rail; and
further cooling the rail to ambient temperature.