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US 2003/0192625 A1Published application
High impact and wear resistant steel
AssigneeCF&I Steel, L.P.
InventorJ. Vincent Cordova
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AssigneeCF&I Steel, L.P.
InventorJ. Vincent Cordova
Estimating the term…
An improved steel railroad rail, and methods for producing same, having a high-carbon content in a range from more than 0.9 to 1.1 wt % is provided that has increased wear resistance and increased fracture toughness over conventional steel rail. The high-carbon rail is characterized as having a pearlitic phase of an eutectoid nature. The average ultimate tensile strength is in a range from 204,860 to 222,120 psi, with a minimum of 174,000 psi. The average yield strength is in a range from 132,320 to 148,450 psi, with the minimum of 120,000 psi. The average percent elongation is in a range from 10.50 to 11.14, with a minimum of 10.00. The Brinell hardness on the surface at any position of the head top and upper gage corners of the rail is in a range from 390 to 440 BHN. The hardness 19 mm below the top surface is in a range from 360 to 435 BHN and 19 mm below the surface at the upper gage corners is in a range from 360 to 410 BHN. The characteristics of the steel rail produced in accordance with the present invention is a substantial improvement as compared with rail used today. The production of a fully pearlitic steel rail having a carbon content from more than 0.9 to 1.1 wt % is remarkable and unexpected. A steel rail of this type having a hardness in a range from 400 to 440 BHN and a combination of yield strength, ultimate tensile strength, elongation and surface and in-depth Brinell hardness goes beyond all expectations and results in a superior and commercially important steal rail.
A high-abrasion resistant fine pearlite rail resistant to rolling fatigue damage, the rail comprising a head having a top and an upper gage corner on each side of the top, the head having a surface, the rail comprising the elements in a range from more than 0.9 to 1.1 wt % of C, 0.26 to 0.80 by wt % of Si, 0.8 to 1.2 wt % of Mn, less than or equal to 0.35 wt % of Cr, and a maximum of each of 0.45 wt % of Cu, 0.25 wt % of Ni, 0.05 wt % of Mo, 0.025 wt % of S, and 0.01 wt % of Al, the balance of iron and residual elements, the head having a substantially uniform fine pearlite structure, a Brinell hardness (BHN) at any position on the surface at the top and upper gage corners in a range from 390 to 440 BHN, and a hardness 19 mm below the surface at the top in a range from 360 to 435 BHN and a hardness 19 mm below the surface at the upper gage corners in a range from 360 to 410 BHN, the rail having a minimum yield strength of 120,000 psi and a minimum tensile strength of 174,000 psi with a corresponding minimum elongation of 10%.
A high-abrasion resistant fine pearlite rail resistant to rolling fatigue damage, the rail comprising a head having a top and an upper gage corner on each side of the top, the head having a surface, the rail comprising the elements in a range from more than 0.9 to 1.1 wt % of C, 0.26 to 0.80 by wt % of Si, 0.8 to 1.2 wt % of Mn, less than or equal to 0.35 wt % of Cr, the balance of iron and residual elements, the head having a substantially uniform fine pearlite structure, and a Brinell hardness (BHN) on the surface at any position at the top and upper gage corners of in a range from 390 to 440 BHN, and a hardness 19 mm below the surface at the top in a range from 360 to 435 BHN and a hardness 19 mm below the surface at the upper gage corners in a range from 360 to 410 BHN, a minimum yield strength of 120,000 psi and a minimum tensile strength of 174,000 psi with a corresponding minimum elongation of 10%.
A method for manufacturing a fully pearlitic steel rail of high toughness and high wear resistance, comprising:
A fully pearlitic steel railroad rail comprising the elements in a range from more than 0.9 to 1.1 wt % of C, 0.26 to 0.80 by wt % of Si, 0.8 to 1.2 wt % of Mn, less than or equal to 0.35 wt % of Cr, and a maximum of each of 0.45 wt % of Cu, 0.25 wt % of Ni, 0.05 wt % of Mo, 0.025 wt % of S, and 0.01 wt % of Al, the balance of iron and residual elements.
A fully pearlitic steel railroad rail comprising the elements in a range from more than 0.9 to 1.1 wt % of C, 0.26 to 0.80 by wt % of Si, 0.8 to 1.2 wt % of Mn, less than or equal to 0.35 wt % of Cr, the balance of iron and residual elements.
Dependencies are inferred from the claim text.
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With nickel: with copper
Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor: for rails
Ferrous alloys, e.g. steel alloys: containing manganese
Modifying the physical properties of iron or steel by deformation: by hot working
Term end not estimated
This invention pertains to steel compositions and methods of producing steel railroad rail, and particularly, but not by way of limitation, to steel rail resistant to damage due to impact and wear.
Efficient railroad transportation systems require that railroad rails withstand the demands of high-axle loads, acceleration and deceleration friction and stress, and high usage. Rail comprises a head, a base, and a web between the head and base. The head comprises an upper gage corner on each side of the top of the head. Rolling fatigue and damage occurs on the top surface of the head of straight rail and typically one of the two upper gage corners of curved rail and is a constant maintenance issue requiring periodic rail replacement.
Fracture toughness, or toughness, is a term used in the art to describe steel's resistance to cracking. Steel having a high toughness while maintaining ductility is less prone to fatigue cracking. The steel will be more fracture resistant to impact loads but more prone to wear and abrasion under sliding loads. Hardness is a term used in the art to describe steel's resistance to deformation. A steel having a high hardness while retaining ductility is less prone to wear and abrasion. Ideal steel for rail would be one that has a high toughness and a high hardness.
FIG. 1 illustrates a cross-section of a common type of railroad rail; and
FIG. 2 presents a graph of hardness data for steel in accordance with an embodiment of the invention.
In the following detailed description, reference is made to the accompanying drawings which form a part hereof wherein like numerals designate like parts throughout, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.
FIG. 1 illustrates a cross-section of a common type of railroad rail 1. The rail 1 comprises a head 10, a base 18 , and a web 16 between the head 10 and the base 18. The head 10 comprises a top surface 14 and a left and right upper gage corner 12a, 12b. The train wheel (not shown) contacts the rail 1 about the head 10.
The present invention is a product of intense research and experimentation to formulate a steel rail 1 having greater than 0.85 wt % carbon content while retaining substantially eutectoid physical characteristics in at least the rail head 10; heretofore unachieved in the history of manufacturing steel rail. It has been found that the combination of a steel with specific alloying agents, thermo-mechanical rolling and heat treatment methods produce a rail 1 with eutectoid physical characteristics with as much as 1.10 wt % of C. The resulting rail 1 exhibits superior hardness to resist abrasion while retaining desirable toughness to resist impact and fatigue damage. The characteristics of the steel rail 1 produced in accordance with the present invention is a substantial improvement as compared with rail used today. The rail 1 exhibits a combination of yield strength, ultimate tensile strength, elongation and surface and in-depth Brinell hardness in a combination much more desirable than anticipated or expected.