Bainitic steel rail containing trace amounts of carbides and producing method of the same

Abstract

The present invention discloses a bainitic steel rail containing trace amounts of carbides, wherein, the bainitic steel rail mainly consists of bainitic structures, the carbides have a length of 0.05-0.5 μm, the major axis of carbides is oriented to a direction at a 50-70° included angle from the direction of the major axis of bainitic ferrite plates, and the carbides account for 1%-5% by volume. The present invention further discloses a method for producing a bainitic steel rail containing trace amounts of carbides, comprising: cooling a steel rail with residual heat after finish rolling by air cooling, till the temperature at the center of the rail head tread reaches 420-450° C.; cooling the rail head part of the steel rail by accelerated cooling at a 2.0-5.0° C./s cooling rate, till the temperature at the center of the rail head tread reaches 220-240° C.; loading the steel rail into a tempering furnace and tempering at 300-350° C. for 4-6 h; then, cooling the steel rail by air cooling to the room temperature. The steel rail provided in the present invention has outstanding wear resistance and contact fatigue resistance properties, and can meet higher requirement for the service of railroad steel rails, and the product is especially applicable to heavy-duty railroads.

What is claimed is: 
     
         1 . A bainitic steel rail containing trace amounts of carbides, wherein, the bainitic steel rail mainly consists of bainitic structures, the carbides have a length of 0.05-0.5 μm, the major axis of carbides is oriented to a direction at a 50-70° included angle from the direction of the major axis of bainitic ferrite plates, and the carbides account for 1%-5% by volume. 
     
     
         2 . The bainitic steel rail according to  claim 1 , wherein, the bainitic steel rail contains: 0.15 wt %-0.30 wt % C, 1.00 wt %-1.80 wt % Si, 1.50 wt %-2.50 wt % Mn, 0.50 wt %-1.00 wt % Cr, 0.20 wt %-0.50 wt % Mo, and Fe that accounts for the remaining content, and the total weight percentage of Mn and Cr meets 2.2%≦Mn+Cr≦3.0%. 
     
     
         3 . A method for producing the bainitic steel rail containing trace amounts of carbides in  claim 1 , comprising: cooling a steel rail with residual heat after finish rolling by air cooling, till the temperature at the center of the rail head tread reaches 420-450° C.; cooling the rail head part of the steel rail by accelerated cooling at a 2.0-5.0° C./s cooling rate, till the temperature at the center of the rail head tread reaches 220-240° C.; loading the steel rail into a tempering furnace and tempering at 300-350° C. for 4-6 h; then, cooling the steel rail by air cooling to the room temperature. 
     
     
         4 . The producing method according to  claim 3 , wherein, the medium of the accelerated cooling is selected from at least one of compressed air, water-air mixture, and oil-gas mixture. 
     
     
         5 . The producing method according to  claim 3 , wherein, the steel rail contains: 0.15 wt %-0.30 wt % C, 1.00 wt %-1.80 wt % Si, 1.50 wt %-2.50 wt % Mn, 0.50 wt %-1.00 wt % Cr, 0.20 wt %-0.50 wt % Mo, and Fe that accounts for the remaining content, and the total weight percentage of Mn and Cr meets 2.2%≦Mn+Cr≦3.0%.