Method and mould for welding the ends of two rail portions
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.
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.