A welding unit for welding rails of a track includes a first sub-unit which is displaceable on unit guides in a rail longitudinal direction relative to a second sub-unit by using displacement cylinders. Each sub-unit includes clamping cylinders disposed underneath the unit guides and coupled to clamping jaws for clamping the rails. The two sub-units are connected by the displacement cylinders in that a cylinder body of the respective displacement cylinder is connected to one sub-unit and a piston rod of the respective displacement cylinder is connected to the other sub-unit. Thus, it is not necessary to support the displacement cylinders relative to a transverse beam disposed at the front.

A welding unit for welding rails of a track includes a first sub-unit which is displaceable on unit guides in a rail longitudinal direction relative to a second sub-unit by using displacement cylinders. Each sub-unit includes clamping cylinders disposed underneath the unit guides and coupled to clamping jaws for clamping the rails. The two sub-units are connected by the displacement cylinders in that a cylinder body of the respective displacement cylinder is connected to one sub-unit and a piston rod of the respective displacement cylinder is connected to the other sub-unit. Thus, it is not necessary to support the displacement cylinders relative to a transverse beam disposed at the front.

A rail tool-holder cart (1) comprises a T-shaped support frame (2), a tool-holder arm, (12) rotatable about a vertical axis and tiltable between an upper position and a lower position and having a coupling interface for a tool (17, 17), a spring (19), which pushes the tool-holder arm permanently towards the upper position, so as to compensate at least one part of the weight of the tool (17, 17), as well as adjustment means (20) for adjusting the spring thrust (19).

Rolling support and guiding element (2) for a rail vehicle, comprising at least one upper portion forming the rolling surface, said portion being made from steel (1) having a composition comprising, in addition to Fe: 0.15C0.3%, 1Mn2%, 0.2%Ni1%, 0.5Cr2%, the steel (1) having a mixed structure of tempered martensite and residual austenite and bainite after having undergone a tempering heat treatment at a controlled speed and for a controlled length of time.

Rolling support and guiding element (2) for a rail vehicle, comprising at least one upper portion forming the rolling surface, said portion being made from steel (1) having a composition comprising, in addition to Fe: 0.15C0.3%, 1Mn2%, 0.2%Ni1%, 0.5Cr2%, the steel (1) having a mixed structure of tempered martensite and residual austenite and bainite after having undergone a tempering heat treatment at a controlled speed and for a controlled length of time.

A rail tool-holder cart (1) comprises a T-shaped support frame (2), a tool-holder arm, (12) rotatable about a vertical axis and tiltable between an upper position and a lower position and having a coupling interface for a tool (17, 17), a spring (19), which pushes the tool-holder arm permanently towards the upper position, so as to compensate at least one part of the weight of the tool (17, 17), as well as adjustment means (20) for adjusting the spring thrust (19).

A method for assembling at least one rolling support and guide element with a complementary part by direct flash welding includes the step of a first step carried out by a first flashing phase intended to increase the temperature of the surfaces to be welded in a homogeneous manner, the duration of this first step being between 15 s and 40 s. A second step is carried out by a phase of preheating by Joule effect of the parts to be welded, the duration of this second step being between 45 s and 55 s with a heating current of between 55 kA and 70 kA. A third step is carried out by a second flashing phase to deoxidize the faces to be welded while avoiding their re-oxidation, the duration of this third step being between 12 s and 22 s and with a flashing current of between 16 kA and 19 kA. A step is included bringing the surfaces to be welded into contact.

A method for assembling at least one rolling support and guide element with a complementary part by direct flash welding includes the step of a first step carried out by a first flashing phase intended to increase the temperature of the surfaces to be welded in a homogeneous manner, the duration of this first step being between 15 s and 40 s. A second step is carried out by a phase of preheating by Joule effect of the parts to be welded, the duration of this second step being between 45 s and 55 s with a heating current of between 55 kA and 70 kA. A third step is carried out by a second flashing phase to deoxidize the faces to be welded while avoiding their re-oxidation, the duration of this third step being between 12 s and 22 s and with a flashing current of between 16 kA and 19 kA. A step is included bringing the surfaces to be welded into contact.

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.

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.