Nano-pearlite rail and process for manufacturing same

Abstract

A nano-pearlite rail and a process for manufacturing the same wherein the rail has excellent mechanical properties, including a tensile strength of no less than 1300 MPa, a yield strength of no less than 1000 MPa, a hardness of HRC 44-47, and an elongation of no less than 10%, as well as excellent wear resistance and fatigue resistance, and is particularly suitable for applications in heavy-haul railways, especially for the railway segments having a sharp turn, and for a wing rail in a bainite steel combined frog.

Claims

1. A nano-pearlite rail, which is a steel rail having an internal microstructure of 100% pearlite with an average interlamellar spacing of pearlite of 55-70 nm, and containing 0.83 to 0.93 of C, 0.05 to 0.10 of Mn, a certain content of Al and Si, 1.0 to 1.5 of Cr, 0.1 to 0.3 of Co, 0.35 to 0.55 of Zr, 0.02 to 0.06 of Mg, 0.01 to 0.05 of Cu, less than 0.025 of S, less than 0.025 of P, and reminder of Fe, wherein the content of Al is 8 to 12 times the content of Mn and the collective content of Al and Si is 1, wherein all the amounts are expressed in wt. %.

Description

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

Examples

Example 1

(1) A molten steel containing 0.83 of C, 0.05 of Mn, 0.6 of Al, 0.9 of Si, 1.4 of Cr, 0.11 of Co, 0.35 of Zr, 0.06 of Mg, 0.05 of Cu, 0.013 of S, 0.005 of P, and reminder of Fe (in wt. %), is smelted using a basic oxygen furnace, followed by external refining and vacuum degassing treatment, and continuous casting and rolling in a vacuum atmosphere to form a steel rail. In the rolling process, the following parameters are used: an initial rolling temperature of 1140 C., a rolling deformation rate of 6 s.sup.1, a single-pass deformation of 32%, a total compression ratio of 12, and a finishing rolling temperature of 960 C. After rolling, the rail is air cooled to a railhead temperature of 850 C. and the temperature is maintained for 30 min, followed by cooling at a cooling rate of 30 C./min to a railhead temperature of no higher than 550 C. and maintaining the temperature for 40 min, and air cooling to a temperature of 350 C. and maintaining the temperature for 80 min, and finally air cooling to room temperature. The cooled rail is then reheated to a temperature of 250 C. and the temperature is maintained for 60 min for stress relieving and tempering treatment. The rail thus obtained has an internal microstructure of 100% pearlite with an average interlamellar spacing of pearlite of 60 nm, which is nano-pearlitic. Therefore, the rail has very excellent mechanical properties, including a tensile strength of 1350 MPa, a yield strength of 1010 MPa, a hardness of HRC 44 and an elongation of 11%, as well as excellent wear resistance and fatigue resistance.

Example 2

(2) A molten steel containing 0.92 of C, 0.09 of Mn, 1.0 of Al, 0.5 of Si, 1.1 of Cr, 0.18 of Co, 0.52 of Zr, 0.04 of Mg, 0.03 of Cu, 0.001 of S, 0.011 of P, and reminder of Fe (in wt. %), is smelted using a basic oxygen furnace, followed by external refining and vacuum degassing treatment, and continuous casting and rolling in an argon atmosphere to form a steel rail. In the rolling process, the following parameters are used: an initial rolling temperature of 1120 C., a rolling deformation rate of 8 s.sup.1, a single-pass deformation of 48%, a total compression ratio of 11, and a finishing rolling temperature of 950 C. After rolling, the rail is air cooled to a railhead temperature of 850 C. and the temperature is maintained for 20 min, followed by cooling at a cooling rate of 50 C./min to a railhead temperature of no higher than 550 C. and maintaining the temperature for 30 min, and air cooling to a temperature of 350 C. and maintaining the temperature for 60 min, and finally air cooling to room temperature. The cooled rail is then reheated to a temperature of 300 C. and the temperature is maintained for 90 min for stress relieving and tempering treatment. The rail thus obtained has an internal microstructure of 100% pearlite with an average interlamellar spacing of pearlite of 55 nm, which is nano-pearlitic, Therefore, the rail has very excellent mechanical properties, including a tensile strength of 1370 MPa, a yield strength of 1050 MPa, a hardness of HRC 45 and an elongation of 12%, as well as excellent wear resistance and fatigue resistance.

Example 3

(3) A molten steel containing 0.85 of C, 0.07 of Mn, 0.7 of Al, 0.8 of Si, 1.3 of Cr, 0.11 of Co, 0.35 of Zr, 0.06 of Mg, 0.05 of Cu, 0.010 of S, 0.005 of P, and reminder of Fe wt. %), is smelled using a basic oxygen furnace, followed by external refining and vacuum degassing treatment, and continuous casting and rolling in a vacuum atmosphere to form a steel rail. In the rolling process, the following parameters are used: an initial rolling temperature of 1100 C., a rolling deformation rate of 8 s.sup.1, a single-pass deformation of 42%, a total compression ratio of 11, and a finishing rolling temperature of 960 C. After rolling, the rail is air cooled to a railhead temperature of 850 C. and the temperature is maintained for 25 min, followed by cooling at a cooling rate of 35 C./min to a railhead temperature of no higher than 550 C. and maintaining the temperature for 35 min, and air cooling to a temperature of 350 C. and maintaining the temperature for 70 min, and finally air cooling to room temperature. The cooled rail is then reheated to a temperature of 280 C. and the temperature is maintained for 70 min for stress relieving and tempering treatment. The rail thus obtained has an internal microstructure of 100% pearlite with an average interlamellar spacing of pearlite of 65 nm, which is nano-pearlitic. Therefore, the rail has very excellent mechanical properties, including a tensile strength of 1360 MPa, a yield strength of 1030 MPa, a hardness of HRC 45 and an elongation of 12%, as well as excellent wear resistance and fatigue resistance.

Example 4

(4) A molten steel containing 0.91 of C, 0.09 of Mn, 1.0 of Al, 0.5 of Si, 1.2 of Cr, 0.21 of Co, 0.44 of Zr, 0.05 of Mg, 0.02 of Cu, 0.008 of S, 0.016 of P, and reminder of Fe (in wt. %), is smelted using a basic oxygen furnace, followed by external refining and vacuum degassing treatment, and continuous casting and rolling in an argon atmosphere to form a steel rail. In the rolling process, the following parameters are used: an initial rolling temperature of 1100 C., a rolling deformation rate of 8 s.sup.1, a single-pass deformation of 35%, a total compression ratio of 12, and a finishing rolling temperature of 960 C. After rolling, the rail is air cooled to a railhead temperature of 850 C. and the temperature is maintained for 25 min, followed by cooling at a cooling rate of 40 C./min to a railhead temperature of no higher than 550 C. and maintaining the temperature for 35 min, and air cooling to a temperature of 350 C. and maintaining the temperature for 90 min, and finally air cooling to room temperature. The cooled rail is then reheated to a temperature of 290 C. and the temperature is maintained for 65 min for stress relieving and tempering treatment. The rail thus obtained has an internal microstructure of 100% pearlite with an average interlamellar spacing of pearlite of 68 nm, which is nano-pearlitic. Therefore, the rail has very excellent mechanical properties, including a tensile strength of 1410 MPa, a yield strength of 1090 MPa, a hardness of HRC 47 and an elongation of 12%, as well as excellent wear resistance and fatigue resistance.

Example 5

(5) A molten steel containing 0.90 of C, 0.06 of Mn, 0.7 of Al, 0.8 of Si, 1.1 of Cr, 0.28 of Co, 0.41 of Zr, 0.05 of Mg, 0.04 of Cu, 0.008 of S, 0.015 of P, and reminder of Fe (in wt. %), is smelted using a basic oxygen furnace, followed by external refining and vacuum degassing treatment, and continuous casting and rolling in an argon atmosphere to form a steel rail. In the rolling process, the following parameters are used: an initial rolling temperature of 1100 C., a rolling deformation rate of 7 s.sup.1, a single-pass deformation of 45%, a total compression ratio of 12, and a finishing rolling temperature of 955 C. After rolling, the rail is air cooled to a railhead temperature of 850 C. and the temperature is maintained for 27 min, followed by cooling at a cooling rate of 45 C./min to a railhead temperature of no higher than 550 C. and maintaining the temperature for 35 min, and air cooling to a temperature of 350 C. and maintaining the temperature for 75 min, and finally air cooling to room temperature. The cooled rail is then reheated to a temperature of 250 C. and the temperature is maintained for 85 min for stress relieving and tempering treatment. The rail thus obtained has an internal microstructure of 100% pearlite with an average interlamellar spacing of pearlite of 70 nm, which is nano-pearlitic, Therefore, the rail has very excellent mechanical properties, including a tensile strength of 1420 MPa, a yield strength of 1100 MPa, a hardness of HRC 47 and an elongation of 12%, as well as excellent wear resistance and fatigue resistance.