TRACK PART MADE OF A HYPEREUTECTOID STEEL

Abstract

In a track part, in particular rail for railway vehicles, made of a hypereutectoid steel, comprising a rail foot, a rail web and a rail head portion, a hypereutectoid steel with the following directional analysis is used: 0.98-1.17 wt.-% of C 0.90-1.35% wt.-% of Mn 0.70-1.10% wt.-% of Si 0.15-0.70 wt.-% of Cr
and wherein the steel, at least in the head portion of the rail, has a pearlitic structure that is substantially free of secondary cementite networks.

Claims

1. Track part, in particular rail for railway vehicles, made of a hypereutectoid steel, comprising a rail foot, a rail web and a rail head portion, characterized in that the hypereutectoid steel comprises a following directional analysis of: 0.98-1.17 wt.-% of C 0.90-1.35% wt.-% of Mn 0.70-1.10% wt.-% of Si 0.15-0.70 wt.-% of Cr and the steel, at least in the head portion of the rail, has a pearlitic structure that is substantially free of secondary cementite networks.

2. Track part according to claim 1, characterized in that C is present in amounts of 1.05 to 1.17 wt.-%, preferably 1.06 to 1.15 wt.-%, and particularly preferably 1.08 wt.-%.

3. Track part according to claim 1, characterized in that the hypereutectoid steel additionally contains Al in an amount of 0.01-0.06 wt.-%.

4. Track part according to claim 1, characterized in that the hypereutectoid steel additionally contains V in an amount of 0.07 to 0.20 wt.-%, in particular 0.10 to 0.20 wt.-%.

5. Track part according to claim 1, characterized in that the hypereutectoid steel additionally contains Nb in an amount of 0.01-0.03 wt.-%.

6. Track part according to claim 1, characterized in that the hypereutectoid steel additionally contains Ti in an amount of 0.015-0.05 wt.-%.

7. Track part according to claim 1, characterized in that that the hypereutectoid steel additionally contains V in an amount of 0.07-0.2 wt.-%, in particular 0.10-0.2 wt.-%, together with Nb in an amount of 0.01-0.03 wt.-%.

8. Track part according to claim 1, characterized in that that the hypereutectoid steel additionally contains Al in an amount of 0.01-0.06 wt.-% together with Nb in an amount of 0.01-0.03 wt.-%.

9. Track part according to claim 3, characterized in that the hypereutectoid steel additionally contains N in an amount ranging from 40 to 120 ppm.

10. Track part according to claim 1, characterized in that the hypereutectoid steel, at least in the head portion of the rail, has a tensile strength greater than 1500 MPa, an elongation at break of greater than 8% and a Brinell hardness greater than 460 HB.

11. A method for producing a track part according claim 1, characterized in that the hypereutectoid steel having a composition according to claim 1 is taken from a furnace at a temperature of 1000-1300 C., then rolled at a final rolling temperature of 850-950 C. and is then subjected to forced cooling to a temperature of 450 C. to 600 C.

12. The method according to claim 11, characterized in that the deformation in the temperature range 1000-850 C. at least in the head portion of the rail has an accumulated comparative degree of deformation of min 1.4.

13. The method according to claim 11, characterized in that the forced cooling takes place at least in the head portion of the rail.

14. The method according to claim 11, characterized in that the forced cooling takes place in a bath of cooling medium not being pure water.

15. The method according to claim 11, characterized in that the forced cooling takes place in a polymer bath having a temperature of 15-50 C.

16. The method according to claim 11, characterized in that the forced cooling is performed at a rate of at least 4 C./sec, preferably at least 8 C./sec, more preferably at least 12 C./sec.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0059] FIG. 1 depicts the pearlitic microstructure of the track part according to the invention,

[0060] FIG. 2 is a chart showing the cementite lamella thickness of the track part of the present invention as compared to the cementite lamella thickness of a rail according to the state of the art,

[0061] FIG. 3 depicts a classification of secondary cementite networks in the material microstructure of the inventive rail part and

[0062] FIG. 4 is a chart showing the wear resistance of the track part of the present invention as compared to the wear resistance of a rail according to the state of the art.

[0063] The rail material microstructure, at least in the standard tensile test position of the rail (10 mm below the running edge), has a pearlitic structure below 3%-nital-etching substantially free of secondary cementite networks corresponding to the classification chart in FIG. 3.

[0064] The cementite lamella thickness is significantly increased in the case of the rail according to the invention compared with a rail from the prior art (rail R400HT according to EN 13674-1), as can be seen from FIG. 2.

[0065] The degree of secondary cementite itself can be assessed with the aid of a classification chart for assessing the secondary cementite precipitates on the microstructure, as shown in FIG. 3.

[0066] 0 . . . free of secondary cementite

[0067] 1 . . . very few traces of secondary cementite

[0068] 2 . . . isolated contiguous secondary cementite structures

[0069] 3 . . . closed secondary cementite network The wear resistance of rails corresponding to the examples was measured by means of a test device according to AT 409766 B (wheel-rail test bench) and compared with that of conventional rail steels according to EN 13674-1 (FIG. 4).

[0070] The results obtained show that the wear resistance of the invention examples could be significantly increased compared to the commercially available railroad tracks, whereby the increased demands on the product properties can be significantly better fulfilled with the aid of the invention.