Method and apparatus for treatment of a rail weld
The present invention provides a rail weld treatment device for improving a resulting microstructure in and around an effected zone of a rail weld and of rails surrounding the rail weld. The device includes, but is not limited to a fixture clamping and centering assembly for engaging a rail head of a rail and a heating and cooling device connected with the fixture clamping and centering assembly to be positioned over the rail head. The fixture clamping and centering assembly comprises an engagement member which removably engages the rail head. The heating and cooling device includes a heating member for heating an effected zone of the rail weld and a cooling member for cooling the effected zone.
1. A method for treating a pre-formed joint connecting a first end portion of a first rail head of a first rail to a first end portion of a second rail head of a second rail, wherein the pre-formed joint is provided by a rail weld that results in a weld heat affected zone in the first end portion of the first rail head and the first end portion of the second rail head, the method comprising the steps of:
locally applying heat to targeted local portions of the rail weld and/or the weld heat affected zone to raise a temperature of heated material of the targeted local portions from an initial temperature to an intermediate temperature which is higher than the initial temperature, wherein the intermediate temperature is high enough to transform some of the heated material substantially to austenite, then;
locally cooling the heated material of the targeted local portions from the intermediate temperature to a final temperature so as to form a resulting pearlitic structure within the targeted local portions of the rail weld and/or the weld heat affected zone that were locally heated to the intermediate temperature, wherein
a temperature of rail head material of at least portions of regions of the first rail head and the second rail head outside of the rail weld and the weld heat affected zone is not raised high enough to transform some of the rail head material substantially to austenite.
2. The method of claim 1 , wherein the resulting pearlitic structure is consistent with a pearlitic structure found in at least portions of the rail head material of the at least portions of the regions of the first rail head and the second rail head outside of the rail weld and the weld heat affected zone.
3. The method of claim 1 , wherein the local cooling of the heated material includes flowing a media over an outer surface of the rail weld and/or an outer surface of the weld heat affected zone.
4. The method of claim 3 , wherein the media is comprised of air, water, or some mixture of air and water.
5. The method of claim 1 , wherein the local cooling is performed using a modulated cooling rate.
6. The method of claim 1 , wherein the temperature of the heated material of the targeted local portions is raised from the initial temperature to the intermediate temperature at a rate of 10° C./s to 500° C./s.
7. The method of claim 1 , wherein the treated portion extends from an outer surface of the rail weld and the weld heat affected zone to a depth of 2 mm to 30 mm.
8. The method of claim 1 , wherein induction heating is used to locally apply heat to the targeted local portions.
9. The method of claim 1 , wherein latent heat from the formation of the rail weld is used, in part, to achieve the intermediate temperature.
10. The method of claim 1 , wherein the resulting pearlitic structure is generally homogenous with a pearlitic structure found in at least portions of the rail head material of the at least portions of the regions of the first rail head and the second rail head outside of the rail weld and the weld heat affected zone.
11. The method of claim 1 , wherein the resulting pearlitic structure comprises a fine lamellar pearlite with an interlamellar spacing of less than 1 μm.
12. The method of claim 11 , wherein the interlamellar spacing is less than 0.5 μm.
13. The method of claim 1 , wherein the step of locally applying heat uses a heating member to locally apply heat to the targeted local portions, and wherein the step of locally cooling uses a cooling member to locally cool the heated material of the targeted local portions.
14. The method of claim 13 , wherein the heating member is incorporated in a device including a length of from 50 mm to 400 mm, wherein the device is positioned such that the length of the device extends along a rail axis of the first end portion of the first rail head and the first end portion of the second rail head.
15. The method of claim 14 , wherein the length of the device is from 75 mm to 375 mm.
16. The method of claim 15 , wherein the length of the device is from 100 mm to 300 mm.
17. The method of claim 13 , wherein the heating member is incorporated in a device, and the method further comprising the step of removably attaching the device with respect to the first end portion of the first rail head and the first end portion of the second rail head.
18. The method of claim 13 , wherein the heating member is incorporated in a device, and the method further comprising the step of centering the device with respect to the first end portion of the first rail head and the first end portion of the second rail head.
19. The method of claim 1 , wherein prior to the step of locally applying heat, material of the rail weld and/or the weld heat affected zone have a microstructure varying from a substantially pearlitic microstructure of at least portions of the rail head material of the at least portions of the regions of the first rail head and the second rail head outside of the rail weld and the weld heat affected zone, and
wherein the resulting pearlitic structure provided after the step of locally cooling the heated material is consistent with the substantially pearlitic microstructure of the at least portions of the rail head material of the at least portions of the regions of the first rail head and the second rail head outside of the rail weld and the weld heat affected zone.