EP3511467B1 - Method for reconstructing a rail profile - Google Patents

Description

The present invention relates to the repair of rails for rail vehicles, such as. B. rail or tram rails, which are made of metal. The invention relates in particular to a method for reconstructing the rail profile of worn rails of a track, according to the preamble of claim 1.

BACKGROUND OF THE INVENTION

Railway or tram rails are usually heavily used when traveling on rail vehicles and are therefore subject to relatively high wear. Typical signs of wear are e.g. B. Extensions on the tread or on the side of the rail. In the following, various signs of wear and the subsequent reconstruction of the rail profile, as it is carried out according to in-house knowledge, are based on the Figures 1 to 4 briefly explained using the example of a tram rail.

Fig. 1 shows a cross-sectional view of a typical tram rail 1 for a covered area, which is intended to be used in a carriageway or a pedestrian area flush with the surface. The rail 1 comprises a traveling head 3 with a running surface 7, on which the wheels of a rail vehicle roll. A groove 6 is also provided adjacent to the traveling head 3, in which groove the wheel flange of the wheels of the rail vehicle is guided. The so-called wheel control arm 5 is then adjacent on the outside. The transition region between the tread 7 and the groove 6 is referred to as the driving edge 4.

On the underside of the traveling head 3, a narrow, web-like transition area 9 is formed, which opens into a rail foot 2. As at the beginning Such rails 1 are subject to considerable wear. Typical signs of wear are exemplified in Fig. 2 shown.

As in Fig. 2 can be seen, the rail 1 shows an extension 10 in the tread 7, which is caused by the rolling of the wheels of rail vehicles. In addition, the rail 1 shows lateral signs of wear 11, 12 on the driving edge 4 and on the wheel control arm 5, as occurs in particular on curved sections. In addition, the groove bottom of the groove 6 can also be worn, as is shown schematically.

In order to reconstruct the original rail profile, several layers of metallic material are applied to the worn area 10-12 by means of a welding process (so-called build-up welding).

Fig. 3 shows a state in which several layers 8a-8x metallic material 14 lying one above the other have already been applied to the worn areas 10-12 of the rail 1. Each of the layers 8a-8x can be 1 mm to 5 mm thick, for example. The uppermost layer is a so-called cover layer 20, which is characterized in that it protrudes outwards beyond a desired target profile 13 of the rail which is to be reconstructed (as a rule this corresponds approximately to the original profile when new) Material hardness can be adjusted to the specifications. After the application of the top layer 20, the surface of the rail 1 is then ground down until the desired target profile 13 is reached.

The final state is in Fig. 4 shown. As can be seen, the traveling head 3 in Fig. 4 his original profile again. The extended or worn areas 10-12 are filled with the metallic material 14.

The method described above for reconstructing the profile of a rail 1 has the disadvantage that after the build-up welding, if the rail 1 cools, a relatively high proportion of martensite is formed in the applied material 14. Martensite is very hard and brittle compared to rail steel, which can lead to cracking in the welded areas.

In addition, the material quality deteriorates and the rail wears out faster. In order to reduce the formation of martensite, it is known to preheat the rail in the welding area. This creates a build-up of heat that causes the applied material to cool down more slowly and thus reduces the formation of martensite. This takes place in the open superstructure at preheating temperatures of usually 300 ° C to 400 ° C. A grooved rail in the covered area can, however, only be preheated up to a maximum of 160 ° C, since components and construction elements in the surrounding area can be damaged at higher temperatures. Because of the low preheating temperatures, martensite formation continues in the applied material, especially in the covered area.

A general method for repairing components by inserting a product produced in a layer process is known from US Pat WO 2017/200401 A1 known.

The RU 2 624 752 C1 discloses a method for reconstructing the rail profile of worn rails, in which a plurality of layers of metallic material lying on top of one another are applied to a worn area of the rail, up to the application of a cover layer which projects beyond the desired target profile of the rail, and at least another layer of a metallic material on the top layer. From the DE 195 39 590 A1 and the BE 532 414 A Further methods for reconstructing the rail profile of worn rails are known, in which several layers of metallic material lying on top of one another are applied to a worn area of the rail.

OBJECT OF THE INVENTION

It is therefore an object of the present invention to provide a method for reconstructing the rail profile of worn rails which the material quality of the reconstructed splint can be significantly improved with comparatively little effort, at a significantly lower preheating temperature.

This object is achieved according to the invention by the features specified in claim 1. Further embodiments of the invention result from the subclaims.

According to the invention, a method for reconstructing the rail profile of worn rails, in particular railroad or tram rails, is proposed, which comprises the following steps: the application of a plurality of layers of metallic material lying on top of one another to a worn region of the rail, up to the application of a cover layer defined target hardness, which projects beyond a desired target profile of the rail that is to be reconstructed; the application of at least one further layer, which is also referred to below as the sacrificial layer, from a metallic material onto the cover layer, and the complete removal of the sacrificial layer and a part of the cover layer until the desired profile is reached.

By applying the so-called sacrificial layer on the top layer it is achieved that the sacrificial layer heats up the layers below, which leads to a tempering process that reduces the martensite content in the layers below. As a result, the material quality of the reconstructed splint can be significantly improved with relatively little effort. This results in fewer cracks in a rail reconstructed according to the invention and the rail has a longer service life.

According to the invention, the section of the rail to be reconstructed is further warmed up to a predetermined preheating temperature before the individual layers are applied. The preheating can be carried out, for example, with a gas burner or an electric heater. The preheating temperature is less than 80 ° C. For example, it can be around 50 ° C. The preheating temperature is a temperature that is measured directly on the weld or in the immediate vicinity of it. The low preheating temperature lowers the maximum temperature during the welding process by up to 50 ° C. This largely prevents damage to surrounding construction elements.

The sacrificial layer applied to the cover layer preferably has a thickness of at least 1 mm. According to a preferred embodiment of the invention, the thickness of the sacrificial layer is between 1 and 5 mm.

The cover layer can in principle consist of the same metallic material as the layers below, or alternatively also of a different metallic material. The material of the underlying layers is preferably a weldable steel. The standard hardness is, for example, in the range of 200 HV - 300 HV (Vickers hardness). The material of the cover layer is preferably also a weldable steel, the hardness can be selected in the range of 200 HV - 500 HV depending on the alloy components.

The sacrificial layer applied to the cover layer can also consist of the same or a different metallic material as the layers below. The material of the sacrificial layer is preferably a weldable steel, in the simplest case with a normal hardness of 200 HV - 300 HV.

BRIEF DESCRIPTION OF THE DRAWINGS

• Fig. 1 ein Profil einer beispielhaften Straßenbahnschiene im Neuzustand;
• Fig. 2 die Schiene von Fig. 1 in einem abgenutzten Zustand;
• Fig. 3 die Schiene von Fig. 1 in einem gemäß betriebsinternen Kenntnissen teilweise rekonstruierten Zustand;
• Fig. 4 die Schiene von Fig. 3 im gemäß betriebsinternen Kenntnissen vollständig rekonstruierten Zustand;
• Fig. 5 die Schiene von Fig. 1 in einem gemäß der Erfindung teilweise rekonstruierten Zustand, in dem eine zusätzliche Opferlage auf die Decklage aufgetragen worden ist; und
• Fig. 6 die Schiene von Fig. 5 im vollständig rekonstruierten Zustand.

The invention is explained in more detail below by way of example with reference to the accompanying drawings. Show it:

• Fig. 1 a profile of an exemplary tram rail in new condition;
• Fig. 2 the rail of Fig. 1 in a worn condition;
• Fig. 3 the rail of Fig. 1 in a partially reconstructed state according to in-house knowledge;
• Fig. 4 the rail of Fig. 3 in a completely reconstructed state in accordance with in-house knowledge;
• Fig. 5 the rail of Fig. 1 in a partially reconstructed state according to the invention, in which an additional sacrificial layer has been applied to the cover layer; and
• Fig. 6 the rail of Fig. 5 in the fully reconstructed state.

Regarding the explanation of the 1 and 2 reference is made to the introduction to the description. In the Fig. 2 shown rail 1 shows several worn areas 10, 11, 12, which have arisen over time due to wear. In order to reconstruct the original profile 13 of the rail 1, the following method can be carried out, for example:

In a first step, old weld metal and other residues such as rust, lubricant and dirt are preferably removed by grinding the rail 1. This also creates a uniformly shaped welding area.

The region of the rail 1 to be reconstructed is then brought to a predetermined preheating temperature. This can be done, for example, using a gas burner or an electric heater. The preheating temperature in the welding area is preferably 100 ° C. or less and according to the invention below 80 ° C. For example, it can be about 50 ° C. If the rail z. B. already has the desired temperature due to solar radiation, preheating can be dispensed with. Preheating is preferably only carried out when the rail temperature is lower than the desired temperature.

The weld metal is then applied to the worn areas 10, 11, 12 of the rail 1 in several layers 8a-8x one above the other. Typically, for example, one to twelve layers of a metallic material 14 can be welded on, each of which can have a thickness of 1-10 mm.

As in Fig. 3 can be seen, a so-called top layer 20 is applied to the layers 8a-8x underneath, which protrudes beyond the desired target profile 13 to the outside. The cover layer 20 can also have a thickness of 1-10 mm. It can also consist of the same or a different material, such as the layers 8a-8x underneath.

According to the invention, the cover layer 20 is not ground off, however, as in Fig. 4 is shown, but a further layer 40 - the so-called sacrificial layer - made of a metallic material 14 is applied to the cover layer 20. As a result, the cover layer 20 underneath is heated and there is a tempering process which leads to the martensitic content in the cover layer 20 and the layers 8a-8x underneath being reduced and the material quality of the rail being improved accordingly. Fig. 5 shows a state in which a sacrificial layer 40 is applied to different reconstructed areas.

In a final step, after removal of slag, the original profile or target profile 13 of the rail 1 is then removed by a grinding or Milling process restored. Fig. 6 finally shows the completely reconstructed splint 1.

Various welding methods known from the prior art can be used for the application of the individual layers 8a-8x, 20, 40, such as, for example, arc welding, metal shielding gas welding, submerged arc welding, laser welding or induction welding.

Claims (4)

1. Method for reconstructing the rail profile of worn rails (1) for rail vehicles, comprising the following steps:

   - applying several layers (8a - 8x), overlying one another, of metallic material (14) onto a worn region (10, 11, 12) of the rail (1), culminating in the application of a top layer (20) which projects outwards over a desired target profile (13) of the rail (1),

   - applying at least one further layer (40) made of a metallic material (14) onto the top layer (20) and

   - complete removal of the further layer (40) and a part of the top layer (20) until the target profile (13) is achieved

   characterised in that
   the rail (1) is preheated to a predetermined preheating temperature on a rail section which is to be reconstructed, wherein the preheating temperature is lower than 80°C and is in particular approximately 50°C.
2. Method according to claim 1,
   characterised in that
   the further layer (40) applied on the top layer (20) has a thickness of at least 2mm, in particular between 2mm and 5mm.
3. Method according to claim 1 or 2,
   characterised in that
   the top layer (20) consists of a different metallic material to the layers (8a - 8x) underlying it.
4. Method according to one of the preceding claims,
   characterised in that the further layer (40) applied onto the top layer (20) consists of a metallic material which is different from the layers underlying it (8a - 8x, 20).

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