STEEL FOR RAILS AND A METHOD OF MANUFACTURING OF A RAIL THEREOF

Abstract

A steel for rail having the following elements, 0.25%C0.8%; 1.0%Mn2.0%; 1.40%Si2%; 0.01%Al1%; 0.8%Cr2%; 0P0.09%; 0S0.09%; 0%N0.09%; 0%Ni1%; 0%Mo0.5%; 0%V0.2%; 0%Nb 0.1%; 0%Ti0.1%; 0%Cu0.5%; 0%B0.008%; 0%Sn0.1%; 0% Ce0.1%; 0%Mg0.10%; 0%Zr0.10%; 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 .

Claims

1-15. (canceled)

16. A steel for rail comprising of the following elements, expressed in percentage by weight: 0.25%C0.8%; 1.0%Mn2.0%; 1.40%Si2%; 0.01%Al1%; 0.8%Cr2%; 0P0.09%; 0S0.09%; 0%N0.09%; and optionally including one or more of the followiing elements 0%Ni1%; 0%Mo0.5%; 0%V0.2% 0%Nb0.1%; 0%Ti0.1%; 0%Ce0.1%; 0%Mg0.10%; 0%Zr0.10%; 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 mm/m.sup.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%C0.8%; 1.0%Mn2.0%; 1.40%Si2%; 0.01%Al1%; 0.8%Cr2%; 0P0.09%; 0S0.09%; 0%N0.09%; and optionally including one or more of the followiing elements 0%Ni1%; 0%Mo0.5%; 0%V0.2% 0%Nb0.1%; 0%Ti0.1%; 0%Cu0.5%; 0%B0.008%; 0%Sn0.1%; 0%Ce0.1%; 0%Mg0.10%; 0%Zr0.10%; 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.

Description

EXAMPLES

[0051] The following tests, examples, figurative exemplification and tables which are presented herein are non-restricting in nature and must be considered for purposes of illustration only and will display the advantageous features of the present invention.

[0052] Rails made of steels with different compositions is gathered in Table 1, where the rail is produced according to process parameters as stipulated in Table 2, respectively. Thereafter Table 3 gathers the microstructures of the rail obtained during the trials and table 4 gathers the result of evaluations of obtained properties.

TABLE-US-00001 TABLE 1 Steel Samples C Mn Cr Si Al S P N Mo Cu Ni V Ti I1 0.50 1.08 1.01 1.53 0.47 0.0010 0.007 0.004 0.0058 0.0130 0.006 0.008 0.0012 I2 0.51 1.08 1.04 1.54 0.06 0.0010 0.007 0.004 0.0058 0.011 0.006 0.0005 0.0011 I3 0.69 1.29 1.27 1.52 0.03 0.0011 0.004 0.004 0.0070 0.013 0.006 0.0008 0.0013

TABLE-US-00002 TABLE 2 HR Reduc- Steel Reheating Finish tion CR1 T1 CR2 Ac3 Sample ( C.) ( C.) % ( C./s) ( C.) ( C./s) ( C.) I1 1250 1035 67 0.6 500 0.1 848 I2 1250 1035 67 0.6 500 0.1 817 I3 1250 1035 67 0.6 500 0.1 800

[0053] Table 2 gathers the process parameters implemented on semi-finished product made of steels of Table 1. The trials 11 to 13 serve for the manufacture of rail according to the invention. The table 2 is as follows:

[0054] Ac3 values were determined through KASATKIN, O.G. et al. Calculation Models for Determining the Critical Points of Steel in Metal Science and Heat Treatment, 26:1-2, January-February 1984, 27-31.

TABLE-US-00003 TABLE 3 Pearlite Steel Pearlite Proeutectoid interlamellar Sample % ferrite % spacing (nm) I1 95 5 125 I2 95 5 170 I3 97 3 211

[0055] Table 3 exemplifies the results of the tests conducted in accordance with the standards on different microscopes such as Scanning Electron Microscope for determining the microstructures of both the inventive and reference steels in terms of area fraction. The results are stipulated herein:

TABLE-US-00004 TABLE 4 Max TS at Room TS at Permeability Sample Temperature 180 C. Resistivity measured at Steels (MPa) (Mpa) HV20 (mm2/m) 4000 A/m I1 1031 937 319 45.8 184 I2 1018 921 312 41.4 186 I3 1193 1049 350 42.3 170

[0056] Table 4 exemplifies the mechanical properties and magnetic properties of both the inventive steel and reference steels. In order to determine the tensile strength, tests are conducted in accordance of NF EN ISO 6892-1/2017 standards. Tests to measure the resistivity and permeability for both inventive steel and reference steel are conducted in accordance of IEC-60404-13 and IEC-60404-4 respectively . Tests to measure the hardness for both inventive steel and reference steel are conducted in accordance of EN-13674. The results of the various mechanical tests conducted in accordance to the standards are gathered.