Steel for rails and a method of manufacturing of a rail thereof

Abstract

A steel for rail having the following elements, 0.25%≤C≤0.8%; 1.0%≤Mn≤2.0%; 1.40%≤Si≤2%; 0.01%≤Al≤1%; 0.8%≤Cr≤2%; 0≤P≤0.09%; 0≤S≤0.09%; 0%≤N≤0.09%; 0%≤Ni≤1%; 0%≤Mo≤0.5%; 0%≤V≤0.2%; 0%≤Nb ≤0.1%; 0%≤Ti≤0.1%; 0%≤Cu≤0.5%; 0%≤B≤0.008%; 0%≤Sn≤0.1%; 0% ≤Ce≤0.1%; 0%≤Mg≤0.10%; 0%≤Zr≤0.10%; the remainder composition being composed of iron and unavoidable impurities caused by processing, the microstructure having, by area percentage, 2% to 10% of Proeutectoid Ferrite, the balance being made of Pearlite wherein the pearlite having interlamellar spacing from 100 nm to 250 nm .

What is claimed is: 
     
         1 - 15 . (canceled) 
     
     
         16 . A steel for rail comprising of the following elements, expressed in percentage by weight:
 0.25%≤C≤0.8%;   1.0%≤Mn≤2.0%;   1.40%≤Si≤2%;   0.01%≤Al≤1%;   0.8%≤Cr≤2%;   0≤P≤0.09%;   0≤S≤0.09%;   0%≤N≤0.09%;   and optionally including one or more of the followiing elements   0%≤Ni≤1%;   0%≤Mo≤0.5%;   0%≤V≤0.2%   0%≤Nb≤0.1%;   0%≤Ti≤0.1%;   0%≤Ce≤0.1%;   0%≤Mg≤0.10%;   0%≤Zr≤0.10%;   a remainder composition being composed of iron and unavoidable impurities caused by processing,   a microstructure of the steel comprising, by area percentage, 2% to 10% of Proeutectoid Ferrite, the balance being made of Pearlite wherein the pearlite has interlamellar spacing from 100 nm to 250 nm.   
     
     
         17 . The steel as recited in  claim 16  wherein the composition includes 0.27% to 0.75% of Carbon. 
     
     
         18 . The steel as recited in  claim 16  wherein the composition the composition includes 0.02% to 0.9% of Aluminum. 
     
     
         19 . The steel as recited in  claim 16  wherein the composition the composition includes 0.9% to 1.9% of Chromium. 
     
     
         20 . The steel as recited in  claim 16  wherein the Pearlite is between 93% and 99%. 
     
     
         21 . The steel as recited in  claim 16  wherein the interlamellar spacing of pearlite is from 110 nm to 230 nm. 
     
     
         22 . The steel as recited in  claim 16  wherein a tensile strength at 180° C. is greater than 900 MPa. 
     
     
         23 . The steel as recited in  claim 16  wherein the steel has hardness of 310 Hv or more. 
     
     
         24 . The steel as recited in  claim 16  wherein the steel has a resistivity of more than 40 Ωmm/m 2 . 
     
     
         25 . The steel as recited in  claim 16  wherein the steel has a maximum permeability equal to more than 165 or more measure at 4000 A/m. 
     
     
         26 . A method of production of a rail of steel, the method comprising the following successive steps:
 providing a steel composition in the form of semi-finished product, the steel composition expressed in percentage by weight including:
 0.25%≤C≤0.8%; 
 1.0%≤Mn≤2.0%; 
 1.40%≤Si≤2%; 
 0.01%≤Al≤1%; 
 0.8%≤Cr≤2%; 
 0≤P≤0.09%; 
 0≤S≤0.09%; 
 0%≤N≤0.09%; 
   and optionally including one or more of the followiing elements
 0%≤Ni≤1%; 
 0%≤Mo≤0.5%; 
 0%≤V≤0.2% 
 0%≤Nb≤0.1%; 
 0%≤Ti≤0.1%; 
 0%≤Cu≤0.5%; 
 0%≤B≤0.008%; 
 0%≤Sn≤0.1%; 
 0%≤Ce≤0.1%; 
 0%≤Mg≤0.10%; 
 0%≤Zr≤0.10%; 
   a remainder composition being composed of iron and unavoidable impurities caused by processing;   reheating the semi-finished product to a temperature from Ac3 to Ac3+500° C. and holding at the temperature from 5 seconds to 1200 seconds;   performing one or more hot rolling passes on the semi-finished product in the austenitic range at a hot rolling temperature from Ac3 to Ac3+300° C. to obtain a hot rail; and   cooling hot rail in two-step cooling, wherein in step one the hot rail is cooled at a cooling rate from 0.1° C./s to 5° C./s from Ac3 and Ac3+300° C. temperature to a temperature T1 ranging from 480 to 550° C., and thereafter in step two the hot rail is cooled at a cooling rate less 5° C./s from T1 to room temperature to obtain a rail.   
     
     
         27 . The method as recited in  claim 26  wherein the reheating temperature of the semi-finished product to is from Ac3+30° C. to Ac3+450° C. 
     
     
         28 . The method as recited in  claim 26  wherein the temperature T1 is from 490° C. to 530° C. 
     
     
         29 . The method as recited in  claim 26  wherein the CR1 cooling rate is higher than CR2. 
     
     
         30 . A method for the manufacture of structural or safety parts of a rail wagon comprising the method as recited in  claim 26 . 
     
     
         30 . A method for the manufacture of structural or safety parts of a rail wagon comprising the employing the steel as recited in  claim 16 .