EP0545336A1 - Head to head welding joint of two aligned rail segments - Google Patents

Abstract

The invention describes the welding connection (5) as well as a method for its manufacture. The mutually facing end sides (6, 7) of the rail segments (1, 2) are interconnected via an added material (8) which extends from the rail foot (32) to the rail head (30). The welding connection (5) is formed by a welding zone (22; 23; 24, 25) connecting the rail foot (32), one connecting a rail web (31) and one connecting the rail head (30). The welding zones (22 to 25) are connected positively in contact regions (33 to 36) turned directly into one another. In addition, the welding zone (22) in the rail head (30) consists of fewer than 15 mutually adjacent, approximately parallel-running welding beads (26) which are melted into one another and preferably lie one above another. The welding zone (24, 25) in the rail foot (32) consists of fewer than 10 mutually adjacent, approximately parallel welding beads (28, 29) which are melted into one another. <IMAGE>

Description

The invention describes a welded joint as described in the preamble of claim 1 and a method for producing such a welded joint.

A wide variety of methods for connecting the ends of immediately successive rail parts for rails of tracks for rail vehicles, for example railroad tracks or tramway rails, are already known. The so-called aluminum-thermite welding is often used for such connection welding, if this is done in the area of laid tracks. In this aluminum thermite welding, metal powder is melted and poured in the liquid state into a mold surrounding the rail ends, so that the gap between the mutually facing, opposite ends of the front ends of the rails is poured out in a manner of casting and is thereby connected to one another.

Flash butt welding is also used for the welding of rails in laid tracks, but above all for the production of connection welds in rail bearings. In this case, the unprocessed abutting surfaces are kept in such light contact during the passage of the current that the material burns continuously at the small local contact points because of the large current density. The liquid metal is thrown out of the joint. After the depth of the burn-up zone is sufficient, the welding is carried out by sudden upsetting with simultaneous power cut-off. A burr is created at the weld due to the liquid material squeezed out of the butt joint. This burr is removed by shearing and subsequent grinding.

Furthermore, in the area of track systems with high rail loads and wear, particularly in curved sections, it is customary to restore the rail head profile by cladding. For this purpose, additional materials are often applied to the rails, in particular in the area of the rail head flanks, using open or concealed arc welds or inert gas welds. The desired rail head shape is then produced by grinding by removing the excess material.

The present invention is based on the object of creating a welded connection between two pieces of rail arranged one behind the other in the longitudinal direction of a rail track, which is composed of several individual seams and can be produced both by hand and by automatic welding processes in a short time without complex machinery.

This object of the invention is achieved by the welded joint described in the characterizing part of patent claim 1. The advantage of this solution is that by arranging several welding zones, in which the material thicknesses are approximately the same, the base materials can be melted sufficiently and an intimate connection can be established between the base material and the additional materials. Above all, this makes it possible to connect and fill the thicker areas by means of a plurality of weld seams arranged next to and above one another. As a result, the total temperature load on the rail track, especially in the area of the welding point, can be kept low, and embrittlement in the welding area is avoided. Another advantage of this solution is that welding can now be carried out under a protective gas atmosphere, as a result of which the access to oxygen to the heated or plasticized areas of the rail can be prevented.

Claim 2 describes a further advantageous embodiment of the welded connection. This makes it possible to use more resistant and harder materials in the areas most exposed to wear, the applied layer thickness and the area in which these materials are used, can now be freely selected and still be welded in a single operation.

An embodiment according to claim 3 is also advantageous, since the different stresses in the different areas of the rail can thereby also be taken into account when the welded connection is made.

The embodiment variant according to claim 4 advantageously enables the welded connection to be produced by a multiplicity of layers of the same structure, as a result of which a uniform structure is achieved over the entire welded connection and a high strength of the welded connection can be achieved. In addition, by adapting or switching on different layers of different additional materials in the interior of the individual welding zones, for example reinforcement areas and reinforcement ribs or layers which promote stretching, high elastic shape-change properties can be used.

Through the further development according to claim 5, internal stress zones can be avoided when transitioning between materials with different elasticity, stretching or bending properties, since sudden changes in the individual strength values are prevented.

The invention also includes a method for producing a welded joint, as described in the preamble of claim 6.

This method is characterized by the features in the characterizing part of claim 6. It is advantageous in the production of the welded joint according to this method that by using the special welding gas to create the plasma, the gas atoms are dissociated into ions and free electrons or protective gas, the charged gas particles being heated to very high temperatures of, for example, 6,600 to 22,200 Degrees. By transferring the highly heated gas particles across the arc, the charged plasma particles release their heat, which at the same time melts the melting electrode and heats up or preheats the base material. An excellent, short-term plasticization of the base material is thus achieved, which prevents the edge regions in the transition between base material and additional material from being heated too strongly and excessively, which leads to embrittlement of the base material in the known processes.

The measures according to claim 7 are also advantageous, since this can specifically prevent local overheating of the base material.

The further measures according to claim 8 enable an embrittlement-free construction of the welding zones by avoiding expansion cracks between the individual welding beads.

In the procedure according to claim 9, it is advantageous that the additional thermal energy required can be kept low, since the welding zones can be produced in one operation without loss of heat in the rail pieces due to the manufacture of the weld beads in the previous welding zone.

If one proceeds according to claim 10, stress cracks or structural changes in the end regions of the welding beads of individual welding zones can be prevented that the welding beads lying one above the other or next to one another are produced as a continuous, one-piece part.

Finally, it is advantageous in the course of the method according to claim 11 that a layer-wise offset bond is made between the individual welding beads in the welding zone, which enables a more favorable transmission of forces between the individual rail pieces.

Fig. 1

einen Schienenstoß in Seitenansicht während der Herstellung einer Schweißverbindung mit der dazugehörigen Schweißanlage in vereinfachter, schematischer Darstellung;

Fig. 2

eine Schweißverbindung zwischen zwei Stirnenden von zueinander fluchtend angeordneten Schienen in Stirnansicht und im Schnitt, gemäß den Linien II-II in Fig.3;

Fig. 3

die Schweißverbindung nach Fig.2 im Schnitt, gemäß den Linien III-III in Fig.2;

Fig. 4

die Schweißverbindung in Stirnansicht mit der im Schienenfußbereich angeordneten Schweißzone und der dieser Schweißzone zugeordneten Kühlvorrichtung, geschnitten, gemäß den Linien IV-IV in Fig.5;

Fig. 5

die Schweißverbindung nach Fig.4 in Seitenansicht;

Fig. 6

die Schweißverbindung in Stirnansicht mit den bereits fertiggestellten Schweißzonen im Bereich des Schienenfußes und des Schienensteges mit der dem Schienensteg zugeordneten Kühlvorrichtung, geschnitten, gemäß den Linien VI-VI in Fig.7;

Fig. 7

die Schweißverbindung nach Fig.6 in Seitenansicht;

Fig. 8

die Schweißverbindung in Stirnansicht mit allen fertig gestellten Schweißzonen und den dem Schienenkopf und dem Schienensteg zugeordneten Kühlvorrichtungen im Schnitt, gemäß den Linien VIII-VIII in Fig.9;

Fig. 9

die Schweißverbindung nach Fig.8 in Seitenansicht.

The invention is explained in more detail below with reference to the exemplary embodiments illustrated in the drawings:
Show it:

Fig. 1

a rail joint in side view during the production of a welded connection with the associated welding system in a simplified, schematic representation;

Fig. 2

a welded connection between two ends of rails arranged in alignment with each other in front view and in section, according to lines II-II in Figure 3;

Fig. 3

the welded joint according to Figure 2 in section, according to lines III-III in Figure 2;

Fig. 4

the welded connection in front view with the welding zone arranged in the rail foot region and the cooling device assigned to this welding zone, cut, according to lines IV-IV in FIG. 5;

Fig. 5

the welded joint of Figure 4 in side view;

Fig. 6

the welded connection in front view with the already completed welding zones in the area of the rail foot and the rail web with the cooling device assigned to the rail web, cut according to the lines VI-VI in FIG. 7;

Fig. 7

the welded joint of Figure 6 in side view;

Fig. 8

the welded connection in front view with all completed welding zones and the cooling devices assigned to the rail head and the rail web in section, according to lines VIII-VIII in FIG. 9;

Fig. 9

the welded joint of Figure 8 in side view.

In Fig.1 two rail pieces 1,2 are shown, the longitudinal direction - arrow 3 - are aligned one behind the other and together form a rail track 4 for rail vehicles, such as trains, trams, funiculars, cranes, etc. The rail pieces 1, 2 are connected to one another in a non-positive and positive manner via a welded connection 5. For this purpose, an additional material 8 is introduced between facing end faces 6, 7 of the two rail pieces 1, 2 by melting a melting electrode 9. The additional material 8 is melted off via an arc 10 built up between the melting electrode 9 and the rail section 1, 2, the access of oxygen and nitrogen to the welding point being prevented by a gas jacket 11 consisting of various protective gases 12, 13, 14.

The fusible electrode 9, which is formed, for example, by a welding wire with a corresponding diameter, is drawn off from a supply roll 15 and fed via a welding gun 16, via which the current supply via a line 17 and the supply of the protective gases 12 to 14 or the protective gas mixture, respectively a line 18 takes place. The welding gun 16 is equipped in accordance with the known designs and is designed with the necessary switches for initiating and interrupting the wire feed of the melting electrode 9 or the power supply or the supply of the protective gases 12 to 14 or protective gas mixture and is provided with a control device 19 and with a voltage supply device 20 and with a container for the protective gases 12 to 14 or the protective gas mixture, for example gas bottles 21, in connection.

The melting electrode 9 has a diameter of between 0.8 and 4.0 mm for producing the welding zones provided, the voltage supply device 20 being designed to supply a current to the melting electrode 9 in the range from 100 to 1100 amperes. The protective gases 12 to 14, or the protective gas mixture produced therefrom, consist of 40% to 70% argon, 25% to 60% helium, 3% to 10% carbon dioxide and 0.1% to 1% oxygen.

The respective melting power or the current supply from the voltage supply device 20 is changed and controlled via the control device 19 so that between 400 to 1200 balls per second of the melting electrode 9 are melted, which preferably have a diameter which corresponds at least to the size of the diameter of the melting electrode 9.

With the above criteria, it is now possible to use the advantages of the spray arc transmission method in conjunction with drop sizes that are normally assigned to the globular transmission method. As a result, in connection with the new welding gas mixture, the increased metal current flow volume can be retained in the welded connection via the plasma field thus achieved, and an improved quality of the welded connection as well as better penetration can be achieved through largely continued preheating of the base material.

2 and 3, a welded connection between two rail sections 1 and 2 is shown, which consists of several weld zones 22, 23, 24 and 25. The welding zones 24 and 25 can also be formed by a common single welding zone.

As can be seen from the representations of the welding zones 22 to 25, each of these welding zones is formed by a plurality of welding beads 26, 27, 28 and 29. These welding beads 26 to 29 are, as the illustration in FIG. 3 in particular shows, arranged between the two facing end faces 6, 7 of the rail sections 1, 2 above and essentially parallel to one another. In each case 6 to 8, a maximum of 10 essentially parallel welding beads arranged one above the other form the welding zone 22 in the area of a rail head 30, while the welding beads 27 form the welding zone 23 in the area of a rail web 31 and the welding beads 28 and 29 form the welding zones 24 and 25 form in the area of a rail foot 32.

As shown schematically in the area of the rail foot 32, when the welding beads 28 or 29 lying one above the other are melted, the uppermost layer of the welding bead 28 or 29 underneath, indicated by dashed lines, melts Welding beads 26 to 29.

Likewise, it can be seen that the welding zones 22 to 25 in the mutually facing contact areas 33, 34, 35 and 36 are fused to one another and thus there is also a uniform microstructure in the different spatial directions of the rail sections 1, 2.

The contact area 34 is formed between the welding beads 27 and 29, the contact area 35 between the welding beads 27 and 28 and between the welding beads 28 and 29 in the area of the rail foot 32 the contact area 36. These contact areas 34 to 36 are shown schematically by dash-dotted lines and different types of hatching. However, it is also possible to design the welding zones 24 and 25 in the region of the rail foot 32 as a single welding zone, as is shown in more detail in a figure that follows later.

The advantage of this uniform microstructure is that uniform strength values are achieved in the welded joint and thus the bending strength or the tensile strength can be increased considerably.

At the same time, however, the impact strength is increased, so that, especially in the area of rail joints, even if small notches form in the area of a running surface 37 of the rail head 30, the vibrations resulting from the impact stress due to the rolling of the wheels over the life of such a welded joint 5 not adversely changed.

With the design of the welded joint 5 according to the invention, it is possible, despite the increased heat supply due to the greater material removal and the improved melting of the base material of the rail sections 1, 2, to prevent the embrittlement of the base material of the rail sections 1 and 2 by in the area of the welded connection during manufacture of the individual welding zones 22 to 25 cooling devices can be arranged.

4 to 9, the cooling devices 38, 39 and 40 required for the production of the different welding zones 22 to 25 are shown in the arrangement required for this. At the same time, the sequence of the representations in FIGS. 4 to 9 results in the process sequence for producing the welded connection 5 according to the invention.

As can be seen from FIGS. 4 and 5, a weld gap 41 is produced between the end faces 6, 7 in which a spacer 42 is located in the region of the rail head before the weld connection 5 is made between the end faces 6 and 7 of the rail pieces 1 and 2 30 is placed on the driving surface 37 and projects into the welding gap 41 with a projection 44 corresponding to a thickness 43 of the welding gap 41.

The cooling device 38 rests on a contact surface 45 of the rail pieces 1, 2 and has a recess 46, the width 47 of which corresponds at least to the thickness 43 of the welding gap 41 or, as shown in particular in FIG. 5, is designed to be somewhat larger. The aim of this is to achieve a certain protrusion of the additional material which protrudes beyond the contact surface 45.

In the area of the rail foot 32, only a single continuous welding zone 24 is shown here. Thus, the contact area 34 is formed between the welding zone 23 in the region of the rail web 31 with its welding beads 27 and the welding zone 24 with the welding beads 28.

Corresponding cooling with the cooling device 38 is achieved by passing coolant through a schematically illustrated line 48 in a schematically illustrated cooling circuit 49 with a pump 50 and a heat exchanger 51 for cooling the cooling medium. A corresponding temperature profile in the base material of the rail sections 1, 2 and in the weld beads 28, 29 adjacent to the base welding bead can thereby be achieved.

The spacer 42 used in the area of the rail head 30 prevents the welding gap 41 from being in the area due to the temperature load on the rail pieces 1, 2 in the area of the rail foot 32 of the rail head 30 reduced. At the same time, an aligned position of the running surfaces 37 of the rail sections 1 and 2 welded to one another is ensured.

Since the welding zone 24 or 25 can be produced with a relatively small number of a maximum of 10 welding beads 28, 29, an intimate connection between the individual welding beads 28 and 29 on the one hand and the base material of the rail pieces 1, 2 on the other hand is possible. Above all, this creates connecting webs in the form of a tension band between the rail sections 1, 2, for which it is possible to find sufficient length compared to the use of electrodes for producing such a welded connection with a considerably smaller number of weld beads 26 to 29.

After the two rail feet 32 of the rail pieces 1, 2 are welded to one another, as can be seen from FIGS. 6 and 7, a cooling device 39 is arranged on one of the two sides of the rail web 31 and the welding gap 41 between the end faces 6 and 7 by arrangement several horizontal weld beads 27 closed. However, there is also the possibility of welding the welding gap 41 with vertical welding beads 27, the cooling device being able to be moved from one side wall of the rail web 31 to the other during operation, so that the rail web 31 can be completely welded through.

After this working process, while the spacer 42 was still arranged between the end faces 6, 7 of the rail sections 1, 2, this spacer 42 is removed and, in addition to the cooling device 39, a further cooling device 40 is arranged on the side of the rail head 30 opposite the cooling device 39. The welding gap 41 in the region of the rail head 30 is then filled with 10 to 12, but a maximum of 15 welding beads 26. The cooling devices 39 and 40, like the cooling device 38, have corresponding depressions 46 in the area of the welding gap 41, so that a protrusion of the respective welding beads 26 to 29 over the surfaces of the rail sections 1, 2 can be made possible. In those areas where these supernatants over the adjacent surfaces of the rail sections 1, 2 are disruptive, these can be subsequently removed by means of shearing or grinding machines.

The cooling devices 39 and 40 can be acted upon with the same cooling circuit 49 as with the cooling device 38, but it is also possible to assign a separate cooling circuit 49 to each cooling device 38 or 39 or 40.

Another advantage of this solution according to the invention is, however, that by arranging a plurality of welding beads 26 to 29, the loads in the individual cross-sectional areas of the rail sections 1, 2 can be taken into account more easily by suitable selection of the additional materials and, above all, different additional materials. It is thus possible, for example, to weld the uppermost or more welding beads 26 closest to the running surface (s) 37 or the rail head flanks in the area of the rail head 30 with different, e.g. to produce harder additional materials, so that an increased resistance to wear in the area of the rail head 30, in particular the running surface 37 or the rail head flanks, can be achieved.

A particular advantage of the procedure now described for producing the welded joint 5 in connection with the welding gas mentioned at the outset is that when the plasma is created, the gas atoms are dissociated into ions and free electrons or protective gases, the charged gas particles reaching very high temperatures of e.g. 6,600 to 22,200 degrees can be heated. If such highly heated gas particles are now transferred across the arc, the charged plasma particles give off their heat in order to melt away the melting electrode 9 and to heat or preheat the base material. The subsequently cooled gas particles combine again to form the molecular structure of the original gas or gases.

It also proves to be advantageous in the production of the different welding zones 22 to 25 if the different properties of the additional materials 8 in welding beads which are directly adjacent to one another 26, 27, 28, 29 of a welding zone 22; 23, 24, 25 or contact area 33, 34, 35, 36 are not too different. If such a large difference is desired, for example, the hardness of the elastic modulus, the elastic elongation, the flexural strength or other relevant material properties, it is advantageous to have these values increase linearly or exponentially over several layers in order to then reach the final value. This avoids internal stresses in the weld seam and stress cracks can also be prevented in the subsequent operating loads.

Furthermore, when manufacturing the individual welding beads 26 to 29, it must be taken into account that a uniform structure can be achieved, in particular with high strengths, if the individual welding beads 26 to 29 are applied directly in succession in the various adjacent welding zones 22 to 25. This eliminates multiple cooling and heating of the connection area with the harmful disadvantages regarding embrittlement and internal tensions. Of course, this applies not only to the production of the adjacent welding beads 26 to 29 in each welding zone 22 to 25, but also to the immediately successive production in the adjacent welding zones 22 to 25 in their contact areas 33 to 36, since this causes internal tensions between the welding zones 22 to 25 and additional structural changes in the contact areas 33 to 36 between the individual welding zones 22 to 25 can be avoided.

It has also proven to be advantageous if the immediately adjacent, successively produced welding beads 26 to 29 are applied in a welding zone 22; 23, 24, 25 or in the adjacent welding zones 22 to 25 in opposite welding directions. This has the advantage that structural changes at the beginning of each welding process can be avoided, since this welding bead 26 to 29 is produced as an endless, theoretically zigzag-shaped welding bead 26 to 29 and thus transition losses, due to the renewed beginning of welding in Edge area of the welding zone 22 to 25, between the individual welding beads 26 to 29 can be prevented.

It can also prove to be advantageous if the weld beads 26 to 29 of a welding zone 22 to 25 or the weld beads 26 to 29, which are produced one after the other, in mutually adjacent weld connections 5 are offset with respect to one another in the longitudinal direction of the rails, but are arranged to overlap in edge regions running perpendicular to the longitudinal direction of the rails. This layer-by-layer displacement of the welding beads 26 to 29, for example by half the division, in order to produce a type of composite construction such as in masonry made of bricks, offers more intimate interlocking of the individual welding beads 26 to 29 or the individual layers of the additional material 8, which results in the overall properties this weld 5 can be significantly improved.

It is of course possible within the scope of the invention to change the arrangement of the individual elements as desired or to combine them differently in addition to the exemplary embodiments shown.

Individual features from the exemplary embodiments shown can also represent independent solutions according to the invention.

Finally, it should be noted that individual parts are disproportionately enlarged or shown schematically simplified in the drawings of the exemplary embodiment for a better understanding of the invention. List of reference symbols 1 Track piece 41 Welding gaps 2nd Track piece 42 Spacer 3rd arrow 43 thickness 4th Rail track 44 head Start 5 Welded joint 45 Footprint 6 Face 46 deepening 7 Face 47 width 8th Additional material 48 management 9 Fusible electrode 49 Cooling circuit 10th Electric arc 50 pump 11 Gas jacket 51 Heat exchanger 12th Shielding gas 13 Shielding gas 14 Shielding gas 15 Supply roll 16 Welding gun 17th management 18th management 19th Control device 20th Power supply device 21 gas bottle 22 Welding zone 23 Welding zone 24th Welding zone 25th Welding zone 26 Welding bead 27th Welding bead 28 Welding bead 29 Welding bead 30th Rail head 31 Rail web 32 Rail foot 33 Touch area 34 Touch area 35 Touch area 36 Touch area 37 Driving surface 38 Cooler 39 Cooler 40 Cooler

Claims (11)

Welded connection between two rail pieces arranged one behind the other in the longitudinal direction of a rail track, in which the mutually facing end faces of the rail pieces are connected to one another via an additional material which extends from the rail foot to the rail head, characterized in that the welded joint (5) is provided by a rail foot (32 ), a rail web (31) and a welding zone (22; 23; 24, 25) connecting the rail head (30) is formed and that the welding zones (22 to 25) are positively connected in mutually directly facing contact areas (33 to 36) and that the welding zone (22) in the rail head (30) consists of fewer than 15 mutually adjacent, fused and preferably superimposed approximately parallel welding beads (26) and the welding zone (24, 25) in the rail foot (32) consists of less than 10 neighboring, fused, almost parallel welds caterpillars (28,29). Welded connection according to claim 1, characterized in that the additional material (8) in a surface area directly facing at least one running surface (37) of the rail track (4) has a higher resistance or hardness than in the other weld zones (23 to 25). Welded connection according to claim 1 or 2, characterized in that the welded zones (22 to 25) are made with different additional materials (8). Welded connection according to one or more of claims 1 to 3, characterized in that the welded zones (22 to 25) are produced by several layers and preferably at least individual layers are made from different additional materials (8). Welded connection according to one or more of claims 1 to 4, characterized in that the hardness, the modulus of elasticity and the elastic expansion of the additional materials in the welding zones or the layers changes linearly and / or exponentially in the direction of the running surface (37) or in the direction of the rail foot (32). Method for producing a welded connection between mutually facing end faces of rail pieces of a rail track, in which the two facing end faces of the rail pieces are spaced apart from one another in the thickness of a welding gap, in particular according to one or more of claims 1 to 5, characterized in that using a Shielding gas (12 to 14), which consists of 40% to 70% argon, 25% to 60% helium, 3% to 10% carbon dioxide and 0.1% to 1% oxygen and using a melting electrode (9) with a diameter between 0.8 mm and 4.0 mm and a current of 100 amperes to 1100 amper welding beads (27) are applied one above the other in a welding zone (24 or 25) arranged in the region of the rail foot (32), after which the welding beads are applied in the area of the rail web (31) and the rail head (30) are located welding zones (23, 22), the welding zone ( 24.25) in the rail foot (32) by max. 10 and the welding zone (22) in the rail head (30) by max. 15 superimposed weld beads (26) is produced. A method according to claim 6, characterized in that a cooling device is first assigned to the welding gap on the contact surface of the rail pieces facing away from the rail head (30) and the welding zone (24, 25) is filled with additional material (8), after which the cooling device (38) is removed and a cooling device (39) is assigned to the welding zone (23) in the region of the rail web (31). Method according to claim 6 or 7, characterized in that the individual welding beads (26 to 29) in the individual welding zones (23 to 25) are each applied in direct succession. Method according to one or more of claims 6 to 8, thereby characterized in that the welding beads (26 to 29) in a further welding zone (22; 25; 23, 24) adjacent to the completed welding zone (23, 24) before the welding beads (26 to 29) cool in the already completed welding zone (23, 24) can be produced. Method according to one or more of claims 6 to 9, characterized in that the immediately adjacent, successively produced welding beads (26 to 29) of a welding zone (22 to 25) are applied in successive, opposite welding directions. Method according to one or more of claims 6 to 10, characterized in that the welding beads (26 to 29) in the respective welding zones (22 to 25) or in the adjacent welding zones (22 to 25) are offset with respect to one another in the longitudinal direction of the rail and in the same Edge regions running perpendicular to the longitudinal direction of the rail are arranged to overlap.

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