JPH1053816A - Heat treatment of rail joint manufactured with intermediate casting welding and burner unit fixed to using with this heat treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat treatment method which forms a welded joint properly suitable to the stress and also, remarkably shortens the required treating time in comparison with the conventional technique and can obtain high heat economization. SOLUTION: This device executes the treatment method applying a normalizing treatment in the joint range of the end parts of both rails and further, in the range of at least rail foot parts 2 by utilizing the remained heat yet existing in the heat affected zone in succession to in the welded part and both sides of the welded part in the max. limit following to the welding process. In such a case, plural burners 10, 11, 20, 21 are distributed in symmetric to the vertical longitudinal direction center plane 22 and the side direction center plane 14 vertically extended to the longitudinal direction center plane, and the burners are communicated with one piece of distributing pipe 3 providing a gas connecting part 5 at the one side of end part 4, and the device is constituted so as to be possible to set on a rail forming material 1 or a floor range adjoined to the rail forming material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The invention relates to a method for at least partially adjusting the fine-grained normalized structure, in particular in the joint area, as described in the preamble of claim 1.
The present invention relates to a heat treatment method for a rail joint manufactured by intermediate cast welding.

[0002] The invention furthermore relates to a burner unit specified for use within the scope of the method.

[0003]

2. Description of the Prior Art It is well known that the application of an aluminothermite welding process to produce a welded joint between two rail ends results in a cast steel structure in the joint area, the cast steel structure comprising: It consists of a steel formed by the aluminothermite reaction and a rail steel melted in the generated steel, in which case, on both sides of this intermediate casting structure, a heat-affected zone with a characteristic structure structure follows, Each heat-affected zone continuously transitions into a rail area which is unaffected by the welding operation. This organization takes place mainly in connection with the time course of the temperature field generated in the rail body as a result of the welding process, in particular in connection with locally different heating rates, temperatures and cooling rates. In the immediate vicinity of the heat-affected zone area, for example as a result of the welding process, a strong overheating results in a coarse-grained, hard pearlite structure, which contains (in the heat-affected zone, the weld joint The area where the hardness is reduced continues, and reaches the area that causes the lowest hardness based on the formation of pearlite, and begins with this virtually soft annealing area and is affected by the welding process. The rail area which does not receive will continue. As a result of the local decrease in the hardness of the rail joints and, consequently, the wear strength, depending on the degree of the hardness difference or in relation to the rail steel used in each case, it is absolutely necessary to postpone the heat treatment step in the welding process. Will be needed.

As rail steel, for example, 900 N / mm
A self-hardening steel with a minimum strength of ² and a hardness of 260 HV to 280 HV is used, the alloy composition of which mainly consists of carbon and manganese. By adding other alloying components such as chromium and vanadium, this hardened steel has a minimum strength of 1100 N / mm ² and 310 HV-330
It is also used as special steel with HV hardness. Still further, self-hardened steel whose strength and hardness are further improved by a special heat treatment method is used. The self-hardening steel in this case is a fine pearlite steel, and the hardness of the fine pearlite steel is increased to a value of 350 HV to 400 HV only in the rail head region subjected to a heavy load by running operation, or over the entire rail region. I have. The microstructural changes resulting from the welding process mentioned at the outset now have various effects, and in particular depending on the rail steel used.

For example, DE 43194
No. 17, there is known an intermediate cast welding method for a head quenched fine pearlite rail, in which case a steel melt produced by an aluminothermite reaction is applied to the end faces of both rail ends to be joined. After casting in the mold surrounding the welding part and after cooling the welding part, the running surface of the welding part and the running surface of the heat affected zone adjacent thereto are heated by the burner system from above for a short time of 50 s to 150 s. In this case, the burner surface of the burner system used is positioned at a distance related to the weight per meter of the rail with respect to the running surface of the weld. Efforts are thus made to obtain a fine pearlitization of the weld and the adjacent heat-affected zone and an equalization of the course of the hardness curve between the weld and the rail area which is not affected by the welding process. . By transferring the heat required for the heat treatment extremely quickly, in particular during a predefined time interval, over the entire running surface of the rail to be treated, a defined temperature gradient is obtained in the vertical direction, so that the rail The depth of the austenitic zone extending from the running surface is determined by the parameters that characterize the heat transfer. Cooling is provided directly by the cold region of the rail body itself, omitting the use of external coolant. If the weld joint is ignored in the longitudinal direction of the rail, the formation of a fine pearlite structure in the surface area of the rail head and the equalization of the hardness curve course,
As a result, wear resistance can be equalized.

Further, based on US Pat. No. 5,306,361 and US Pat. No. 5,377,959,
Known is a method and apparatus for performing a heat treatment on a welded joint as described above after performing welding, in which case an annealed thermite is used in a mold that completely surrounds the welded joint, and in a rail forming material. The heat to be introduced into the furnace is designed to achieve austenitization, which is followed by rapid cooling with pressurized air. Thus, a complete normalization of at least the surface area of the rail profile takes place with this known method.

[0007] The purpose of the heat treatment method is to equalize the material properties in the area beyond the weld joint, in particular to equalize the material properties to those of the rail material outside the range of the weld joint. In particular, the material properties considered in this case are properties such as tensile strength and hardness. The main features of known heat treatment methods are:
First, the welded joint is effectively cooled to ambient temperature, then
The heating and cooling of the tissue area to be treated as a function of temperature-time. This means that the heat still remaining in the weld and the heat affected zone as a result of the welding process remains substantially unused.
Aside from the increased processing time required as a result of the cooling step, this working mode clearly shows that increased fuel usage is based on reheating to above the austenitizing temperature.

[0008] The load on the rail joints resulting from the running operation occurs in the rail foot region as bending vibration stress with alternating tensile stress.

[0009]

It is an object of the present invention to improve a heat treatment method of the type mentioned at the outset, to form a welded joint which is correctly adapted to stresses, and to reduce the required processing time compared to the prior art. It is an object of the present invention to provide a heat treatment method that can be significantly shortened and obtain high thermoeconomic efficiency, and to provide a device suitable for carrying out the treatment method, particularly that can be easily operated at a track work site.

[0010]

SUMMARY OF THE INVENTION The method according to the present invention for solving the above-mentioned problems is characterized in that it follows the welding process, that is, in the weld and on both sides of the weld. The advantage of the present invention is that the residual heat still present in the heat-affected zone is used to the greatest extent to provide a normalizing treatment in the joint area at the ends of the two rails, and at least in the area of the rail feet.

An important point of the invention is that following the aluminothermite welding process, ie immediately after the mold head has been removed and the feeder has been cut, and possibly also after the grinding operation has been carried out, and thus the weld joint area is still large. Is to start the heat treatment at a time when the residual heat is retained but at a temperature lower than the austenitizing temperature. The heat introduction for austenitization again, that is, the heat introduction performed for the purpose of adjusting the fine-grained austenite structure, can be quantitatively limited using the residual heat in this way.
Reduced fuel consumption within the framework of heat treatment and improved utilization of heat introduced into the joint area to carry out the welding process will reduce total fuel consumption and consequently labor costs . Except for the coarse-grained structure present both in the region of the intermediate-structured structure and in the heat-affected zone on both sides of the intermediate-structured structure, a fine-grained normalized structure is formed instead of the coarse-grained structure. However, in order to be able to withstand the stresses of running operation, in particular in terms of toughness properties, the heat treatment, ie the normalization, takes place at least in the region of the rail feet.

Subsequent to the heat treatment of the weld joint area, cooling to ambient temperature, finish grinding and removal of foot feeder and mold remnants are performed.

[0013] Furthermore, the unfavorable intrinsic stress states resulting from the welding process can be at least partially eliminated via the heat treatment method of the present invention.

The measures according to claim 2 relate to the size of the area to be subjected to the normalizing process, that is, it is specified that the means can be applied not only to the rail foot area but also to the rail head. However, in practice, the heat treatment of the temporal surface of the rail head causes a normalization of the running surface of the rail, based on the rapid propagation expansion of the resulting temperature field.

The measures according to claims 3 and 4 relate to different embodiments for cooling the heated and austenitic joint area. In principle, the cooling can be carried out with calm ambient air, but it is also conceivable to carry out a quenching treatment, for example by means of pressurized air, depending on the achievable cooling rate or the desired surface hardness.

The measures according to claims 5 and 6 relate to a further embodiment of a particularly advantageous embodiment of the heat treatment method.
The purpose of performing such treatment is as follows:
The introduction of heat into the heat-affected zone following this region depends on the geometry of the rail profile and the extent of the heat-affected zone, including the intermediate casting zone, and on the conditions of heat conduction or heat propagation. In relation to the temperature field generated inside the rail body based on the above, the control is performed so as to cause the following structural transformation over time and in place, and the structural transformation is the naked eye. A structural transformation which gives the desired rail properties, i.e. mainly sufficient toughness, and sufficient hardness and resistance to crack propagation in the rail head region, in particular in the running surface region, to the rail joint region.
The parameters used to control the temperature field include the spatial distribution of the introduced heat in the rail joint area, the local amount of heat introduction and the duration of the heat introduction, the last mentioned heat introduction The duration is used in particular to control the depth at which tissue metamorphosis is to occur. Cooling is effected via ambient air gently stagnating over other "cold" rail bodies, and in a special case at least locally acting quenching. In any case, the purpose of this cooling treatment is to replace the coarse-grained structure produced by the welding process with a fine-grained structure having improved strength properties and toughness properties, at least in specified areas, having been subjected to normalizing treatment. In that The basic processing steps associated with the normalization, i.e., heating up quickly to a temperature slightly higher than the austenitizing temperature, maintaining the temperature until a fine-grained austenite structure is formed, Subsequent rapid cooling steps are known in principle, and a detailed description in this regard will be omitted here.

[0017] According to a seventh aspect of the present invention, there is provided an apparatus according to the present invention, which is adapted to carry out the heat treatment method which further solves the above-mentioned problem. A plurality of burners are distributed symmetrically with respect to a transverse central plane extending perpendicularly to the burner.
The gas connection is in communication with one distribution pipe provided at one end and the device can be mounted on the rail profile to be treated or on the roadbed area adjacent to the rail profile The point is that it is configured.

An important point of the apparatus of the present invention is that a plurality of burners are distributed symmetrically with respect to two planes orthogonal to each other and connected to one distribution pipe for guiding a combustible gas mixture. is there. The device according to the invention is designed so that the device can be used in a position such that the lateral center plane coincides with the corresponding center plane of the intermediate casting area, and therefore, when heat is introduced into the rail joining area. The essential symmetry property has already been guaranteed based on the burner arrangement described above. The device according to the invention is designed in particular for mounting on parts of rail profiles.
This is because in this way it is ensured that the specified spacing between the burner nozzle unit and the surface section of the rail profile to be heated is reproducible.

The measures according to claims 8 to 11 relate to the spatial distribution of the burners, in which the heating of the intermediate casting area is effected on two side faces of the rail head. The heating of the rail foot region is provided by burners and the burners are oriented in the heat affected zones on either side of the intermediate casting region.

The supporting element according to claim 12 and the spacer according to claim 13 together with the rail molding make it possible to always reproduce the heat transfer conditions in the rail joint area and to make the field work comfortable. .

[0021]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

Reference numeral 1 designates a rail forming material to be treated, in particular, a joint (joining) area between two rail ends. It is placed on the track through the track. Therefore, the burner unit is used in the laid rail frame.

The burner unit has a distribution pipe 3 installed to guide a combustible mixed gas composed of, for example, propane and oxygen, and a gas connection 5 is provided at one end 4 of the distribution pipe. The other end 6 of the distribution pipe, which is located opposite the end 4, is closed. The distribution pipe 3 extends horizontally above the rail head 7 at an interval and is supported by the rail molding 1 in a manner to be described later.

Two branch pipes 8 and 9 are connected to the distribution pipe 3, and both branch pipes are connected to burners 10 and 11, respectively. 12,
13 and is held at a specified distance from the temporal surface. The branch pipes 8, 9 and the burners 10, 11 extend substantially in a transverse central plane 14 which simultaneously forms a plane of symmetry of the intermediate casting area 15 and, on both sides of said intermediate casting area, a welding not shown. The heat affected zone is connected. On both sides of said lateral center plane 14,
Moreover, the planes 16, 1 are symmetrical with respect to the lateral center plane.
Further branch pipes 18 and 19 extend into the pipe 7, and burners 20 and 21 are arranged at the ends of both branch pipes. The arrangement of the branch pipes 8 and 9 and the branch pipes 18 and 19 provided with the burners 20 and 21 are configured symmetrically with respect to the vertical longitudinal center plane 22 of the rail forming material 1.

Furthermore, the burners 20, 21 are arranged such that each jet direction is on both sides of the intermediate casting area 15 and in the area adjacent to the rail foot 2, and is directed directly to the welding heat affected zone. Furthermore, each of the burners 20, 21
Has two burner surfaces extending at an angle to each other and each having a plurality of jet nozzles, the orientation of the burner surfaces being substantially substantially equal to the rail foot 2 and directly adjacent to the rail foot 2 The orientation of the facing area of the web area is adapted.

Reference numeral 23 denotes a support element attached to the casing of the burner 20, and the support element includes:
It is specified to stand on the facing surface of the rail foot 2. The same support elements 24 are arranged on opposing burners 21. The support element 2
3 and 24 together form a support mechanism for the burner unit according to the invention, which is symmetrical with respect to the horizontal center plane 14 and the vertical center plane 22.

Furthermore, reference numerals 25 and 26 denote web-like spacers, which extend from the side of all the branch pipes 18 and 19 facing the rail-forming material 1 and have a temporal surface 12 and 26, respectively. 13 to abut. The compensating mass body 27 attached to the other end 6 of the distribution pipe 3 is for further securing the stability of the burner unit.

The burners used in the different surface areas of the weld joint are, as will be clear from the above description, symmetrical with respect to both planes, ie, about the vertical longitudinal center plane 22 and the transverse center plane 14. Are distributed and arranged. The surface spacing of the burner nozzle from the opposing surface of the rail profile, the amount of flammable gas mixture introduced through the distribution pipe 3 to carry out the heat treatment (in this case normalizing), and thus also the heat to be transferred. Alternatively, the duration of the heat transfer is set in relation to the residual heat of the rail profile from the preceding welding process.

[Brief description of the drawings]

FIG. 1 is an end view of a burner unit according to the present invention mounted on a rail molding.

FIG. 2 is a plan view of the burner unit as viewed in the direction of arrow II in FIG.

FIG. 3 is a side view of the burner unit viewed in a direction of an arrow III in FIG. 2;

[Explanation of symbols]

1 rail forming material to be processed, 2 rail foot,
3-minute pipe, one end of 4-minute pipe, 5 gas connection, 6-minute pipe other end, 7 rail head, 8,9 branch pipe, 10,11 burner,
12, 13 temporal plane, 14 lateral center plane,
15 intermediate casting area, 16, 17 plane,
18, 19 another branch pipe, 20, 21 burner,
22 vertical longitudinal center plane, 23, 24 support elements, 25, 26 web-like spacers,
27 Compensating mass

Continued on the front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI Technical display location C21D 1/26 C21D 1/26 R 1/28 1/28 1/52 1/52 Y 9/50 101 9 / 50 101Z // B23K 101: 26 (72) Inventor Michael Steinhorst Essen Schlossgarten 21 Germany

Claims (13)

[Claims] In a heat treatment method for rail joints produced by intermediate cast welding, in particular for at least partially adjusting the fine-grained normalization structure in the joint area, following the welding process, that is to say welding By taking full advantage of the residual heat still present in the section and in the heat-affected zone on either side of the weld, in the joint area at the ends of the two rails, and at least in the area of the rail foot (2) And a heat treatment method for rail joints manufactured by intermediate cast welding, characterized by performing normalizing treatment. 2. The method according to claim 1, further comprising the step of normalizing the region of the rail head. 3. The method according to claim 1, wherein the one or more treatment areas are normalized while cooling in a calm surrounding air.
The heat treatment method described. 4. The normalizing is performed while cooling at least one processing area by a quenching method using pressurized air.
Or the heat treatment method according to 2. 5. The heat introduced into the joint zone within the normalizing zone is transmitted symmetrically in the longitudinal and transverse directions to the intermediate casting zone (15), and the heat applied to the rail head (7). The transfer takes place in the intermediate casting area (15) via both side heads (12, 13), and the heat transfer to the rail foot (2) takes place in the heat-affected zones on both sides of the intermediate casting area (15). The heat treatment method according to claim 1, wherein the heat treatment is performed in a region. 6. Improving parameters that characterize the heat transfer, such as heating rate, holding time and cooling rate, in particular the wear strength and friction resistance of the rail head (7) and the ductility of the rail foot (2). The heat treatment method according to claim 5, wherein the heat treatment method is selected. 7. An apparatus for carrying out the heat treatment method according to claim 1, in particular a burner unit, wherein a vertical center plane (22) and a vertical center plane are provided. The plurality of burners (10, 11, 20, 2, 2) are symmetrical with respect to a vertically extending transverse central plane (14).
1) is distributed and the burners (10, 11, 20,
21) communicates with one distribution pipe (3) provided with a gas connection (5) at one end (4), and the apparatus comprises:
An apparatus for performing a heat treatment method, wherein the apparatus is configured to be mountable on a rail forming material (1) to be processed or on a roadbed area adjacent to the rail forming material. 8. At least one burner (10, 11) provided on each side of the longitudinal center plane (22) has a jet direction located in the transverse center plane (14). Item 7. The apparatus according to Item 7. 9. The burner (10, 11) according to claim 7, wherein the jet direction is oriented towards the temporal surface (12, 13) of the rail profile (1) to be treated. apparatus. 10. At least one burner (20, 21) is provided on both sides of the vertical center plane (21) and both sides of the horizontal center plane (14), respectively, and the jet direction of the burner is the horizontal direction. 10. The device according to claim 7, wherein the device extends parallel and at a distance to a directional center plane. 11. The jet direction of the burner (20, 21) is:
11. The device according to claim 10, wherein in the region of the heat-affected zone, the rail profile to be treated is substantially oriented with respect to the rail foot. 12. A support element (23, 24) specified for standing upright on a part of the rail foot (2) on both sides of the weld joint comprises a longitudinal center plane (22) and a transverse plane (22). 12. The device according to claim 7, wherein the device is arranged symmetrically with respect to (10). 13. A burner (10, 11, 20, 21) communicates with a distribution pipe (3) through a branch pipe (8, 9, 18, 19), and further comprises a rail forming material (1). Spacers (2) supported on the rail profile (1) to hold the burner at a defined distance from the surface to be heated
Device according to any one of claims 7 to 12, wherein (5, 26) is provided.