EP3511467A1 - Method for reconstructing a rail profile or connection welding of rails - Google Patents

Abstract

A method of reconstructing the rail profile of worn rails (1), comprising the steps of: applying a plurality of superimposed layers (8a - 8x) of metallic material (14) to a worn portion (10, 11, 12) of the rail (1), to towards the application of a cover layer (20) which projects beyond a desired desired profile (13) of the rail (1) to the outside; the application of at least one further layer (40) of a metallic material (14) on the cover layer (20) and the removal of the protruding material (14) until reaching the desired profile (13).

Description

The invention relates to a method for reconstructing a rail profile or for connection welding of rails according to claim 1.

BACKGROUND OF THE INVENTION

Rail or tram rails are heavily stressed when driving on rail vehicles and are therefore subject to relatively high wear. Typical signs of wear are z. B. Extensions on the tread or on side surfaces of the rail. In the following, various signs of wear and the subsequent reconstruction of the rail profile, as carried out in the prior art, based on FIGS. 1 to 4 briefly explained using the example of a tram track.

OBJECT OF THE INVENTION

Fig. 1 FIG. 12 shows a cross-sectional view of a typical covered area tramway rail 1 intended to be used in a lane or pedestrian area flush with the surface. FIG. The rail 1 comprises a driving head 3 with a running surface 7 on which the wheels of a rail vehicle roll. Adjacent to the travel head 3, a groove 6 is also provided, in which the wheel flange of the wheels of the rail vehicle is guided. Externally adjacent is then the so-called Radlenker 5. The transition region between the tread 7 and the groove 6 is referred to as the driving edge 4.

At the bottom of the driving head 3, a narrow, web-like transition region 9 is formed, which opens into a rail 2. As at the beginning has been mentioned, such rails 1 are subject to considerable wear. Typical signs of wear are exemplary 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 the Radlenker 5, as they occur in particular on curved sections. In addition, the groove bottom of the groove 6 may be worn, as shown schematically.

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

Fig. 3 shows a state in which several superimposed layers 8a - 8x metallic material 14 have already been applied to the worn portions 10 - 12 of the rail 1. Each of the layers 8a-8x may, for example, be 1 mm to 5 mm thick. The uppermost layer is a so-called cover layer 20, which is characterized in that it over a desired target profile 13 of the rail, which is to be reconstructed (usually this corresponds approximately to the original profile in new condition), outwardly protruding and their Material hardness can be adjusted to the specifications. After applying the cover layer 20, the surface of the rail 1 is then ground so far until the desired target profile 13 is reached.

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

The above-described method for reconstructing the profile of a rail 1 has the disadvantage that after the build-up welding, when the rail 1, 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 cause cracking of the welded areas. In addition, the material quality deteriorates and the rail is worn faster. 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, thus reducing martensite formation. This is done in the open superstructure at preheating temperatures of usually 300 ° C to 400 ° C. However, a grooved rail in the covered area can only be preheated to a maximum of 160 ° C, as at higher temperatures damage to components and construction elements in the surrounding area can occur. Due to the low preheating temperatures, martensite formation in the applied material continues to occur, particularly in the covered area.

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

It is therefore an object of the present invention to provide a method for reconstructing the rail profile of worn rails, with which the material quality of the reconstructed rail 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 will become apparent from the dependent claims.

According to the invention, a method for reconstructing the rail profile of worn rails, in particular railway or tram rails, is proposed, which comprises at least the following steps comprising: applying a plurality of superimposed layers of metallic material on a worn portion of the rail, to applying a cover layer with a defined target hardness, which projects beyond a desired desired profile of the rail, which is to be reconstructed, to the outside; the application of at least one further layer, which is also referred to below as sacrificial layer, of a metallic material on the cover layer, and the complete removal of the sacrificial layer and a portion of the cover layer until reaching the desired profile.

By applying the so-called sacrificial layer to the cover layer, it is achieved that the sacrificial layer heats the layers underneath, which leads to a tempering process which reduces the martensite content in the layers lying underneath. As a result, the material quality of the reconstructed rail can be significantly improved with relatively little effort. In an inventively reconstructed rail, this results in less cracking and the rail has longer life. The same method can also be used when connecting two rail pieces.

The invention relates to the repair of rails of rail vehicles, such. B. railway or tram rails, which are made of metal.

According to a preferred embodiment of the invention, the portion of the rail to be reconstructed is heated to a predetermined preheating temperature before application of the individual layers. The preheating can be carried out for example with a gas burner or an electric heater. The preheating temperature is preferably less than 100 ° C, and more preferably 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 thereof. The low preheating temperature lowers the maximum temperature prevailing during the welding process by up to 50 ° C. Damage to surrounding construction elements can be prevented as far as possible.

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 underlying layers, or alternatively also of another material. The material of the underlying layers is preferably a weldable steel. The control hardness is for example in the range 200 HV - 300 HV (Vickers hardness). The material of the cover layer is preferably also a weldable steel, the hardness can be selected depending on the alloy components in the range 200 HV - 500 HV.

The sacrificial layer applied to the cover layer can also be made of the same or a different material as the underlying layers. The material of the sacrificial layer is preferably a weldable steel, in the simplest case with a normal 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 dem Stand der Technik teilweise rekonstruierten Zustand;
• Fig. 4 die Schiene von Fig. 3 im gemäß dem Stand der Technik 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 will now be described by way of example with reference to the accompanying drawings. Show it:

• Fig. 1 a profile of an exemplary tram track in new condition;
• Fig. 2 the rail of Fig. 1 in a worn condition;
• Fig. 3 the rail of Fig. 1 in a state partially reconstructed according to the prior art;
• Fig. 4 the rail of Fig. 3 in the state completely reconstructed according to the prior art;
• 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 completely reconstructed state.

Regarding the explanation of Fig. 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 are caused by wear over time. In order to reconstruct the original profile 13 of the rail 1, for example, the following procedure can be carried out:
In a first step, preferably old weld metal and other residues such as rust, lubricating material and dirt are removed by grinding the rail 1. In addition, this creates a uniformly shaped weld area.

Thereafter, the region of the rail 1 to be reconstructed is preferably brought to a predetermined preheating temperature. This can be done for example by means of a gas burner or an electric heater. The preheating temperature in the welding region is preferably 100 ° C. or less and in particular less than 80 ° C. It can be for example about 50 ° C. If the rail z. B. already has the desired temperature due to sunlight, can be dispensed preheating. Preheating is preferably done only when the rail temperature is lower than the desired temperature.

After that, weld metal is applied to the worn areas 10, 11, 12 of the rail 1 in several superimposed layers 8a-8x. Typically, for example, one to twelve layers of a metallic material 14 are welded, each of which may have a thickness of 1-10 mm.

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

However, according to the invention, the topsheet 20 is not abraded, as in FIG Fig. 4 (Prior art) is shown, but it is a further layer 40 - the so-called sacrificial layer - applied from a metallic material 14 on the cover layer 20. Thereby, the underlying cover layer 20 is heated and there is a tempering process, which causes the martensite in the top layer 20 and the underlying layers 8a - 8x decreases and improves the material quality of the rail accordingly. Fig. 5 shows a state in which a sacrificial layer 40 is applied to various reconstructed areas.

In a final step, then, after removal of slag, the original profile or desired profile 13 of the rail 1 is restored by a grinding or milling process. Fig. 6 finally shows the finished reconstructed rail 1.

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

Claims (6)

Method for reconstructing the rail profile of worn rails (1) or for joint welding of rails (1), comprising the following steps: - Applying a plurality of superimposed layers (8a - 8x) metallic material (14) on a worn portion (10, 11, 12) of the rail (1), to applying a cover layer (20) over a desired desired profile (13) the rail (1) protrudes outwards, - Applying at least one further layer (40) of a metallic material (14) on the cover layer (20) and - Complete removal of the further layer (40) and a part of the cover layer (20) until reaching the desired profile (13). Method according to claim 1,
characterized in that
the rail (1) is preheated to a rail section to be reconstructed or an end section to a predetermined preheating temperature. Method according to claim 2,
characterized in that
the preheating temperature is lower than 80 ° C and more preferably about 50 ° C. Method according to one of the preceding claims,
characterized in that
the further layer (40) applied to the cover layer (20) has a thickness of at least 2 mm, in particular between 2 mm and 5 mm. Method according to one of the preceding claims,
characterized in that
the cover layer (20) of a different material is like the underlying layers (8a - 8x). Method according to one of the preceding claims,
characterized in that on the cover layer (20) applied further layer (40) consists of a different material as the underlying layers (8a - 8x, 20).

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