Method and Device for Production of Heat Treated Welded Rail for Rail Transport and Rail Produced Therewith

1 . A method for the production of heat treated welded rail for rail transport comprising the subsequent steps of:

i. providing rail lengths to desired specifications

ii. welding two rail lengths together in a welding unit to produce a continuous welded rail, CWR, or producing a longer continuous welded rail by welding one or more additional rail lengths to the continuous welded rail; and

iii. post-welding heat treating the entire continuous welded rail in a heat treatment unit by heating the entire continuous welded rail, or by heating all successive cross-sections of the continuous welded rail, to above the Ac 3 -temperature to achieve a fully austenitic microstructure in the entire continuous welded rail, followed by holding the continuous welded rail or all successive cross-sections of the continuous welded rail section above Ac 3 for a prescribed time t a followed by subjecting the continuous welded rail or all successive cross-sections of the continuous welded rail to cooling at a cooling rate using a cooling medium to a prescribed cooling stop temperature T stop to achieve the desired transformed final microstructure and properties along the entire length of the post-welding heat treated continuous welded rail.

2 . The method according to claim 1 wherein the continuous welded rail is heat treated at a constant feed rate of at least 0.5 and/or at most 10 m·min −1 .

3 . (canceled)

4 . The method according to claim 1 , wherein the continuous welded rail is produced by welding together lengths of steel having a composition suitable for obtaining a microstructure which is substantially eutectoid or hypereutectoid after heat treatment, wherein the cooling stop temperature is below Ar 1 , and wherein the transformed final microstructure treated of the post-welding heat treated continuous welded rail consists substantially of pearlite or pearlite and cementite and substantially free or completely free of martensite and/or bainite phases.

5 . The method according to claim 1 , wherein the continuous welded rail is made by welding together lengths of steel having a composition suitable for producing a bainitic microstructure after heat treatment, wherein the cooling stop temperature is such that the transformed final microstructure of the post-welding heat treated continuous welded rail is fully bainitic and substantially or entirely free of martensite and substantially or entirely free of pearlite or ferrite phases.

6 . The method according to claim 1 , wherein the welding process is a flash-butt welding process.

7 . A device for performing the method of claim 1 , provided with:

i. a welding unit for welding two rail lengths together in a welding unit to produce a continuous welded rail, CWR, or to produce a longer continuous welded rail by welding additional rail lengths to the continuous welded rail;

ii. a heat treating unit

a. for post-welding heat treating the continuous welded rail by subjecting the entire continuous welded rail to substantially the same heat treatment above the Ac 3 -temperature to achieve a fully austenitic microstructure in the continuous welded rail in a batch heat treatment unit, or

b. for post-welding heat treating the entire continuous welded rail by feeding the entire continuous welded rail through the heat treatment unit for heating all successive cross-sections of the continuous welded rail to above the Ac 3 -temperature to achieve a fully austenitic microstructure in all the successive cross-sections,

iii. a holding unit for holding the continuous welded rail or all the successive cross-sections above Ac 3 for a time t a , said holding unit being optionally integrated in the heat treating unit, and

iv. a cooling unit for cooling parts of the continuous welded rail (head, base of the foot, web) or the entire continuous welded rail or all the successive cross-sections of the CWR using a cooling medium to a cooling stop temperature T stop to achieve the desired homogeneous transformed final microstructure and properties in the entire post-welding heat treated continuous welded rail.

8 - 10 . (canceled)

11 . The method of claim 1 further comprising removing weld upset or upsets, or parts thereof, prior to post-welding heat treatment.

12 . The method of claim 11 , wherein removing the weld upset or upsets, or parts thereof, is by stripping, grinding, milling or any combination thereof.

13 . The method according to claim 11 , wherein the weld upset is removed from the foot of the rail.

14 . The method according to claim 12 , wherein the weld upset is removed from the foot of the rail.

15 . The method of claim 14 wherein the weld upset is further removed from the web and head of the rail.

16 . The method of claim 1 further comprising providing the head of the post-welding heat treated continuous welded rail at the locations of a weld with a desired rail head profile.

17 . The method of claim 16 wherein providing the desired rail head profile is by grinding or milling.

18 . The method according to claim 11 , wherein the weld upset is removed from the foot, wherein the weld upset is removed from the foot, web and head of the rail.

19 . The method according to claim 12 , wherein the weld upset is removed from the foot, wherein the weld upset is removed from the foot, web and head of the rail.

20 . The device of claim 7 , further comprising a unit for removing part of, or the whole weld upset or weld upset.

21 . The device of claim 20 , further comprising a head profiling means for providing the head of the continuous welded rail at the locations of the weld or welds with a desired rail head profile.

22 . The device of claim 7 , further comprising a straightening means to straighten the continuous welded rail and/or optional straightening means to straighten the heat treated continuous welded rail.

23 . The device of claim 7 , further comprising a straightening means to straighten the continuous welded rail and/or optional straightening means to straighten the heat treated continuous welded rail.

24 . A post-welding heat treated rail produced according to the method of claim 1 .

25 . The rail according to claim 24 , wherein no heat affected zones are present at any position along the entire length of the post-welding heat treated rail.

26 . The rail according to claim 24 , wherein:

the difference between the minimum hardness in HV30 of the post-welding heat treated CWR and the average hardness in HV30 of the post-welding heat treated CWR is lower than 10% of the average hardness value in HV30, or wherein

the difference between the maximum hardness in HV30 of the post-welding heat treated CWR and the average hardness in HV30 of the post-welding heat treated CWR is lower than 15% of the average hardness value in HV30, or wherein

the difference between the minimum hardness of the post-welding heat treated CWR and the average hardness in HV30 of the post-welding heat treated CWR is lower than 10% of the average hardness value in HV30 and the difference between the maximum hardness in HV30 of the post-welding heat treated CWR and the average hardness in HV30 of the post-welding heat treated CWR is lower than 15% of the average hardness value in HV30; and

wherein the hardnesses in HV30 are determined in accordance with ISO 6507-1:2005.

27 . A post-welding heat treated rail produced using the device of claim 7 .

28 . The rail of claim 27 , wherein no heat affected zones are present at any position along the entire length of the post-welding heat treated rail.

29 . The rail according to claim 27 wherein:

the difference between the minimum hardness in HV30 of the post-welding heat treated CWR and the average hardness in HV30 of the post-welding heat treated CWR is lower than 10% of the average hardness value in HV30, or wherein

the difference between the maximum hardness in HV30 of the post-welding heat treated CWR and the average hardness in HV30 of the post-welding heat treated CWR is lower than 15% of the average hardness value in HV30, or wherein

the difference between the minimum hardness of the post-welding heat treated CWR and the average hardness in HV30 of the post-welding heat treated CWR is lower than 10% of the average hardness value in HV30 and the difference between the maximum hardness in HV30 of the post-welding heat treated CWR and the average hardness in HV30 of the post-welding heat treated CWR is lower than 15% of the average hardness value in HV30; and

wherein the hardnesses in HV30 are determined in accordance with ISO 6507-1:2005.