Method and mould for welding the ends of two rail portions

Abstract

Method for the aluminothermic welding of rails, involving the steps of: triggering an aluminothermic reaction in a crucible, pouring the metal resulting from said reaction into the mold so as to fill the molding cavity from the rail flange, after filling the cavity, triggering a second aluminothermic reaction above the rail head, and pouring the metal resulting from said reaction into the cavity in the region of the rail head. The mold used in the method is designed to fit over the ends of two rails to form a molding cavity comprising a crucible positioned above the rail head region so that it can be fed with molten metal of the cavity via a secondary passage.

Claims

1. A process for welding two longitudinal rail sections including: a step of placing the two longitudinal rail sections to be welded end-to-end so as to create a joining space between the ends of the two longitudinal rail sections; a step of installing a welding mold around said joining space, said mold defining a welding volume between the two longitudinal rail sections, wherein the welding volume has flaring in a lower half of the welding volume, the flaring increase, towards a bottom surface of the welding volume from a medial portion of the welding volume, is progressive, in a direction both parallel and perpendicular to a longitudinal axis of at least one of the two longitudinal rail sections such that a weld width is larger at a base than at the median portion of the welding volume; a step of pouring liquid welding metal into said welding volume such that the liquid metal mass poured is greater in the lower half of the welding volume than in a upper half; a solidification step of the poured metal so as to weld the two longitudinal rail sections.

2. The process according to claim 1, including, subsequent to the pouring step, a milling step limited to the part of the weld extending above the rail portions after the lifting of the assembly comprising the two rail sections and the weld.

3. The process according to claim 1, including a single milling step.

4. A welding mold for two longitudinal rail sections configured to be placed on said rail sections and defining a welding volume configured to receive a liquid welding metal and such that a space defined by the welding volume has a lower half that is greater than the space defined by the welding volume in an upper half, wherein the welding volume has flaring in the lower half, the flaring increase, towards a bottom surface of the welding volume from a medial portion of the welding volume, is progressive, in a direction both parallel and perpendicular to a longitudinal axis of at least one of the two longitudinal rail sections such that a weld width is larger at a base than at the median portion of the welding volume.

5. The mold according to claim 4, wherein the welding volume is has the flaring in at least the lower half of the welding volume so as to receive a greater liquid welding metal mass than that received by the upper half.

6. The mold according to claim 5, wherein the welding volume has the flaring progressively from the top down.

7. The mold according to claim 5, wherein the lower half of the welding volume includes at least one roughly tronconical section portion.

8. The mold according to claim 7, wherein said portion is a truncated pyramid.

9. An assembly formed by two longitudinal rail sections placed consecutively and a weld obtained by the process according to claim 1, part of which is placed between the two rail sections.

10. The assembly according to claim 9, wherein the weld includes a bead flared in lower portion of the weld.

11. The assembly according to claim 10, wherein the bead includes at least one truncated pyramid portion.

Description

(1) Other invention characteristics and advantages are revealed in the following description of the appended figures provided as non-limiting examples and in which identical references have been attributed to similar objects:

(2) FIG. 1 is a partial profile view of an assembly formed by two rail sections joined by a weld according to prior art;

(3) FIG. 2 is a view of the A1-A1 cross-section of the assembly in FIG. 1;

(4) FIG. 3 is a partial profile view of an assembly formed by two rail sections joined by a weld according to the invention;

(5) FIG. 4 is a view of the A2-A2 cross-section of the assembly in FIG. 3;

(6) FIG. 5 is a perspective view of the assembly in FIG. 3;

(7) FIG. 6 partially illustrates the profile of one embodiment of the weld mold according to the invention.

DETAILED DESCRIPTION

(8) Weld System and Mold According to the Invention

(9) Building and maintaining railway tracks requires welding rail sections together at their ends.

(10) FIGS. 3 to 5 are partial representations of assembly 10 formed by two rail sections 20 joined by a weld 30 at their ends 20e.

(11) Each rail section 20 includes an upper, mushroom-shaped part 22 and a base 24 extending along axis YY perpendicular to longitudinal axis XX of the rail sections 20. The upper part 22 and the base 24 are connected by a less thick surface 26.

(12) As illustrated by FIG. 3, weld 30 includes a bead 32 in the form of a truncated pyramid.

(13) Length L1 of the smaller base (or upper base) of truncated pyramid 32 extending along longitudinal axis XX of the rail sections is comprised between 45 mm and 55 mm, preferably approximately equal to 50 mm.

(14) Length L2 of the larger base (or lower base) of truncated pyramid 32 extending along longitudinal axis XX of the rail sections is comprised between 65 mm and 75 mm, preferably approximately equal to 70 mm.

(15) Length E1 represents the length of the smaller base of truncated pyramid 32 extending along axis YY perpendicular to axis XX.

(16) Length E2 represents the length of the larger base of truncated pyramid 32 extending along axis YY perpendicular to axis XX.

(17) Weld 32 joining assembly 10 is obtained by pouring liquid metal into a mold as described hereinafter.

(18) FIG. 6 illustrates welding mold 40 according to the invention placed around two rail sections 20 before pouring the welding metal in mold 40.

(19) Welding mold 40 includes a vent 42 extending roughly vertically along direction ZZ so as to allow the pouring of the welding metal by gravity up to the welding volume V defining the weld contours between the two rail sections 20.

(20) Passage 44 also allows the pouring of the welding metal at the level of the mushroom 22 of the rail sections 20 so as to completely fill welding volume V.

(21) Lastly, welding mold 40 includes curved contour 46 allowing the flare of the welding volume in its lower half so as to receive a greater quantity of welding metal and thereby to allow said metal not to sag rail sections 20 when it cools.

(22) Invention Implementation

(23) In order to weld the two longitudinal rail sections 20, the two rail sections 20 to be welded are placed end-to-end so as to create a joining space (not represented) between their ends 20e.

(24) An alignment bench can be used to place the two ends 20e of the rails sections 20 facing each other. The alignment consists in placing rail sections or end pieces 20 end-to-end such that the surfaces of the upper part 22 of rail sections 20 fall into the same roughly horizontal plane and that their lateral surfaces are oriented towards the interior of the track in a roughly vertical plane, both planes being perpendicular to each other.

(25) Welding mold 40 defining welding volume V between the two rail sections is then installed around said joining space.

(26) A system for pre-heating the welding mold and the ends 20e of the two rail sections 20 is then installed so as to facilitate and improve the welding of the two rail sections 20. Preheating may be by forced air, oxygen-propane, air-gas or any other known type of pre-heating in order to allow such welding.

(27) A crucible, containing an aluminothermic charge including the metal to be poured, is placed above the weld.

(28) The charge is lit so that the aluminothermic reaction occurs and the liquid welding metal flows from the crucible by gravity into the welding volume.

(29) Once poured, the liquid metal mass is then, according to the invention, greater in the lower half of the welding volume than in its upper half.

(30) The mold is then removed in order to allow the poured metal to cool and solidify so as to form the weld joining the two rail sections.

(31) The form conferred to the weld by the mold according to the invention allows, by tension forces in the metal, the weld lifting.

(32) The weld portion extending above the rail portion can therefore be milled before complete weld cooling.