EP2601322B1 - Method for heat treating the wheel rim of railway vehicle wheels - Google Patents

Description

The invention relates to a method for heat treatment of the wheel rim of rail vehicle wheels, in particular of railway wheels.

From the EP 1 215 291 A1 a method for the heat treatment of heated, rotationally symmetrical bodies, for example rail vehicle wheels, of metallic materials is known, in which the relevant body is first descaled and then a functional area-related, defined and reproduced setting of mechanical properties (eg hardness within a successful hardening process) takes place by means of complex cooling processes, which are performed differently for different volume or surface areas of the body to be treated, such that the predetermined areas of the body by spraying or blowing at least one cooling medium (water and / or air) online-controlled or cooled online. During volume and surface specific cooling, the rotationally symmetric body is rotationally driven about its axis of rotational symmetry and the cooling media are simultaneously sprayed or inflated onto a plurality of the surface areas of the body to be cooled. For this purpose, the rotationally symmetrical body is in a horizontal, position such that its axis of rotational symmetry is vertical, and the cooling medium is applied by a plurality of cooling jets or cooling streams ring or forceps on the surface areas to be cooled. This is done by the fact that the rotationally symmetrical body is coated or lapped at the same time or approximately simultaneously by the cooling streams or cooling jets over its entire circumference at the surface areas to be cooled.

In this case, there is also the possibility that successively different cooling media with different cooling effect, for example air and / or water with hardness additives and / or air-water mixtures are applied to the surfaces to be cooled surface of the rotationally symmetrical body and the supply of the cooling medium time-dependent.

The focus of the volume of the cooling medium supply depending on the temperature of the heated rotationally symmetrical body, in particular its continuously measured surface temperature by means of a Temperaturmeßkamera realized, and thereby made the supply of the cooling medium in dependence of empirically determined Gefügewerte the body time-dependent.

The rotationally symmetrical body is during its rotary drive on its upper and Bottom and at its peripheral surface by the flow rates of the cooling medium simultaneously, optionally to different surface areas and / or delayed, cooled by simultaneously the tread and the Radunter- and the Radoberseite be acted upon by the cooling medium or the cooling media. With the cooling of edge regions and / or the top and bottom of the body can be cooled by one or more volume flows at the same time, the hub of the rotationally symmetrical body.

A disadvantage of this solution is the fact that for the targeted influencing of the desired material properties, the regulation and control of the cooling processes by a corresponding volume for the cooling medium supply, based on the measurement of the surface temperature of the rotationally symmetrical body. This surface temperature can be measured under production conditions but only outside the impact areas of the cooling medium on the rotationally symmetrical body and takes place on the tread-side Laufkranzstirnfäche the rail vehicle wheel. The determined surface temperature is thus not significant for the heat flow taking place in the body cross-section and the resulting qualitative and quantitative material property images of homogeneous microstructure or Brinell hardness (HB). A control of the volume of the required cooling medium supply, which is based on the measurement of the surface temperature during an online operation, is fundamentally not suitable for achieving the desired material properties of the rotationally symmetrical body because it has no relation to the heat conduction in the cross section of the body and is also too sluggish for the Homogeneous perlitic microstructure in a narrow time window.

The object of the invention is to propose a method in which realizes a homogeneous, substantially pearlitic structure over the entire cross section of the rim of the rotationally symmetrical body designed as rail vehicle and at the same time the required strength and hardness values in the wheel rim of the rail vehicle wheel by optimizing the heat dissipation the time and the amount of heat can be precisely adjusted to the functional cross section of the rim. It should be achieved in particular to the interior of the rim towards increasing strength and hardness values.

This object is achieved with the features specified in claim 1.

The advantages of the invention are that targeted in the first zone of the primary area (tread and flange) a cooling medium transfer belt is established through which the actual hardening process takes place, and the gentle cooling of the geometrically secondary area (both Laufkranzstirnflächen and the Laufkranzboden) a supporting Function in the optimal hardening and structure formation in the primary area belongs. As a result, the complex processes in the structure formation can be reliably influenced, so that increasing strength and hardness values can be achieved towards the interior of the wheel rim.

The invention will be explained in more detail below using an exemplary embodiment and associated drawings.

Fig. 1

eine Schnittdarstellung eines rotationssymmetrischen Körpers in Form eines Schienenfahrzeugrades

Fig. 2

ein Blockschaubild des Verfahrensablaufes für die Wärmeführung

Fig. 3

eine vereinfachte Darstellung des Radkranzquerschnittes mit der Zoneneinteilung, angedeuteten Kühlmedienströmen und den Härteprüfstellen

Fig. 4

ein Diagramm zu den Volumenströmen für die Wärmeabführung innerhalb eines Härtezyklus

Fig. 5

Tabelle für ein beispielhaftes Basisprogramm für ein Schienenfahrzeugrad in Form eines Eisenbahnrades

Show it:

Fig. 1

a sectional view of a rotationally symmetrical body in the form of a rail vehicle wheel

Fig. 2

a block diagram of the procedure for the heat transfer

Fig. 3

a simplified representation of the Radkranzquerschnittes with the zoning, indicated cooling media streams and hardness testing

Fig. 4

a diagram of the volume flows for heat dissipation within a curing cycle

Fig. 5

Table for an exemplary basic program for a railway vehicle wheel in the form of a railway wheel

In the Fig. 1 the heat-treated, rotationally symmetrical body in the form of a rail vehicle wheel 1 is shown. In this case, the rail vehicle wheel 1 consisting of a metallic material (eg steel or steel alloy) comprises a hub 2, whose associated blade 3 establishes the connection to a tread ring 4, a tread 5 and a tread bottom 6 containing tread 7, which is provided on both sides by tread end faces 8, 9 is limited. For the required heat treatment (hardening process), the rail vehicle wheel 1 is rotationally driven about its vertical axis 10 and its surface areas for adjustment reproducible mechanical properties subjected to cooling processes in which the surface areas are subjected to at least one cooling medium (water and / or air).

The general requirements for a rail vehicle wheel are defined in the railway standard UCI 812-3.

For a long service life of the rail vehicle wheel 1, it is necessary for the running surface 5, despite the wear occurring on the surface, to have the same or increasing hardness relative to the wheel interior. The ideal state in this regard is exemplified at the cross-sectional area of the tread 7 with the hardness test lines and the assignment of hardness values in Fig. 3 and for the hardening process of superficial importance.

For hardening, the blank of the rail vehicle wheel 1 heated to a material-specific hardening temperature (for example, about 840 ° C.) is divided into different regions (geometric zones) for the heat treatment.

Regarding Fig. 3 On the one hand, this concerns the tread zone 19 and flank zone 17 on the tread 7 of the rail vehicle wheel 1, with the hardening zones 21 under the tread zone 19 and the flanged zone 17 as well as the secondary zones representing the tread 5 and the tread Flange 4 subsequent Laufkranzstirnflächenzonen 22, 23 and the Laufkranzbodenzone 20, and on the other hand, the area of the blade 3, the hub 2 with relatively low HB values, these zones depending on the on the tread 7 to be achieved microstructure volume and time controlled with at least one Cooling medium are applied, which with respect to the tread zone 19 and the flange portion 17 as an average water volume flow 11, with respect to the Laufkranzstirnflächenzonen 22, 23 as upper or lower water volume flow 12, 13 and additionally in the lateral region of the flange 4 as an air flow 14 out is is. The control lines 16 include the control zone 18 along which the hardness test points lie at intervals.

In this case, a thermal phase control is carried out to realize a homogeneous pearlitic structure over the entire wheel cross-section, except for the areas of the hub 2, the blade 3 and the cooling medium transfer belt 15 at a precisely adjustable hardness in the tread 5. In the areas of the hub 2 and the leaf 3 is no active cooling, but only free convection.

Starting with a basic program ( Fig. 5 ), whose parameters are based on relevant experience in the previous heat treatment on the basis of tests on different wheel cross sections and materials (eg low alloyed steel ER6, ER7, ER8 according to DIN EN 13262) rail vehicle wheels, and thus represent universal basic values, is the Ersthärtung a new Schienenfahrzeugrades using a hardening machine, as for example from the EP 1 215 291 B1 is known carried out. For this purpose, a cooling of the tread zone 19 and the subsequent flange zone 17 starting from the outer profile of the tread 7 to a depth of, for example, about 7 mm (0.5 .mu.m) is carried out by means of a cooling medium flow 11 (temperature eg 34 to 36.degree % of the diameter of the rail vehicle wheel 1 ==> 0.5% x 1.460 mm = 7.3 mm), which is carried out at a low cooling rate under stabilizing, completed at temperatures <620 ° C formation of a homogeneous microstructure, to form a cooling medium transfer belt 15, by which subsequently takes place an attenuation of the cooling effect of the further acting cooling medium for the heat dissipation in the actual hardening process of the underlying hardness zones 21. This cooling medium transfer belt practically acts as a guard ring and typically has a substantially lower hardness than the underlying areas of the hardening zones 21. The thickness of this cooling medium transfer belt 15 is about 2 to 7 mm.

The achieved hardness and microstructure in 2 to 7 mm depth of secondary importance, since these areas are removed in the mechanical post-processing. Due to this stabilized zone (cooling medium transfer belt), which later undergoes no further structural transformation, the actual hardening process takes place, in which the heat exchange between the discharged heat quantity and the internal heat content only takes place via this cooling medium transfer belt 15 at the tread zone 19 and the flange zone 17.

Due to the design of this cooling medium transfer belt 15 of 2 to 7 mm thickness and cooled to a temperature of 70 to 200 ° C, heat guides for curing can be achieved using water, which are otherwise accessible only by means of a salt or lead bath.

At the same time, the two raceway end faces 8, 9 and their Runner faces 22, 23 (secondary area) with a cooling medium (upper or lower water volume flow 12, 13) acted in conjunction with the heat dissipation zone, the return of heat from the interior of non-actively cooled areas in the hardness zones 21 and their negative impact on the already formed microstructure or to prevent the hardness in the hardness zones 21. The primary hardness range is thus procedurally not affected by refluxing heat, in particular from the Laufkranzstirnflächen 8, 9.

With the largest possible provision of the water volume flow 11, the cooling of the wheel 1 is completed in this area and short cycle times are reached. Without this supportive heat dissipation, it is not possible to reliably produce the maximum possible hardness in zones 21 in a homogeneous structure in the relevant areas or would significantly higher amounts of cooling media in the tread area necessary, which cause an exact control hardness / structural ratio is impossible , In addition, the cooling takes place in the lateral region of the flange 4 by an air flow 14th

In the Fig. 2 is the basic procedure for the heat transfer starting from the curing machine, as for example from the EP 1 215 291 B1 is known, with its actuators, the cooling medium quantity control and nozzle settings, the associated control with the modular options with regard to the effect on the thermal phases and geometric areas associated with the rail vehicle wheel and associated database for storing and calling wheel-specific program parts.

With a new rail vehicle wheel, the first rail vehicle wheel hardening is carried out with a basic program.

After the heat treatment of the first railway vehicle wheel has been completed by hardening, the wheel is subjected to a material-technical sample evaluation, metallographic and mechanical test values, with regard to microstructure, hardness test values, tensile test values and impact test results. The target / actual value comparison is carried out and from this the correction values for the manipulated variables for the geometric and thermal ranges are determined. In detail, it is the cooling medium dosing with respect to the thermal phases and geometric areas, the type of media, the design of the heat dissipation from the secondary wheel areas, as well as the speed of the rotary drive of the rail vehicle 1. These parameters and setting values are stored in the specific wheel program and provided for the 2nd heat control on the next rail vehicle wheel.

If evaluated positively, the data from the database is available for mass production.

It is the property of the rail vehicle materials that the quality of the structure formation and, associated with it, the mechanical properties at constant heat transfer according to the process Fig. 4 for the hardening process is quality-appropriate and clearly reproducible.

The determination of the required quantities required for heat dissipation is defined individually according to wheel type, size, material, geometry of the cross-sectional profile and with regard to the given properties as well as to the properties, microstructure and associated hardness values required in the wheel areas.

The values thus found are stored in a database and are available for series production of rail vehicle wheels of this special type.

The representation of the water and air volume flows 11, 12, 13, 14 and their assignment to the rail vehicle are on the heat treatment time in the Fig. 4 shown. Therein, the design of the heat dissipation by the cooling media in a characteristic curve as a function of the cooling medium amounts and type over time with the division into thermal phases (phase 1 to 3) is reproduced.

Determining the hardness is the heat removal per unit time, i. the volume flow of the acting cooling medium.

The correction values required after the sample evaluation for setting the desired microstructure and hardness values of the wheel rim 7 are shown in the diagram ( Fig. 4 ) in the region of the zone 2 on both sides in the direction of the dot-dash line extending, drawn solid lines. A very steep increase in the straight line causes a high hardness, a flat rise guarantees a homogeneous structure.

• Phase 1 = Bildung des Kühlmediumübertragungsbandes,
• Phase 2 = Härtevorgang,
• Phase 3 = Wärmeableitung aus dem bereits gehärteten Bereich,

die Informationen zum Anfahr-, Verlaufs- und Endverhalten aufweisen.This diagram is divided into thermal phases

• Phase 1 = formation of the cooling medium transfer belt,
• Phase 2 = hardening process,
• Phase 3 = heat dissipation from the already hardened area,

have the information on start-up, progress and end behavior.

List of used reference numbers

1

Railway vehicle

2

hub

3

leaf

4

flange

5

tread

6

Tread ground

7

tread

8th

Tread face

9

Tread face

10

axis

11

mean water volume flow

12

upper water volume flow

13

lower water volume flow

14

Airflow

15

Coolant transfer belt

16

Control line for the hardness test points

17

Flanged zone

18

Control zone with lines along which the hardness test points lie at intervals

19

Tread zone

20

Tread soil zone

21

Hardiness zones

22

Tread face zone

23

Tread face zone

Claims (1)

1. A method for heat treating the wheel rim of railway vehicle wheels,
   characterized in that
   the running rim (7) of a first rail vehicle wheel is divided into zones, namely the running surface zone (19), the flange zone (17), the hardness zones (21) lying under the running surface zone (19) and the flange zone (17), the two running rim end face zones (22, 23) connected to the running surface (5) or the flange (4), and the running rim bottom zone (20), and at least one cooling medium is applied to the said zones in a volumetric-flow- and time-controlled manner depending on the microstructures to be achieved on the running rim (7) on the basis of a basic program divided into thermal phases, wherein:

   - first the running surface zone (19) and the connected flange zone (17) are cooled starting at the outer profile of the running rim (7) to a depth of 0.5 percent of the diameter of the railway vehicle wheel (1) at a low cooling rate under stabilizing formation of a homogeneous pearlitic microstructure in order to form a cooling medium transfer band (15), by means of which subsequently the cooling effect of the still acting cooling medium for the heat conduction for the actual hardening process of the hardness zones (21) lying under the cooling medium transfer band is damped;

   - at the same time, the cooling medium (12, 13) is applied to the two running rim end face zones (22, 23) in order to prevent, in conjunction with the heat dissipation zone, heat from flowing back into the hardness zones (21) and affecting the already produced microstructure in the hardness zones (21), wherein cooling by means of a cooling medium (14) occurs additionally in the lateral area of the flange (4);

   - after the completed heat treatment of the first railway vehicle wheel, the wheel is subjected to a materials sample evaluation, and correction values (cooling medium amounts associated with the thermal phases, the cooling medium type, and the specification of the heat dissipation from the secondary area of the railway vehicle wheel (1) and of the speed of the rotational drive of the railway vehicle wheel (1)) for the hardening of a further railway vehicle wheel are specified on the basis of the target/actual comparison with respect to the microstructure and the hardness values in order to optimize the heat treatment process, and

   - the values found in such a way are stored in a database and are available for series production of railway vehicle wheels (1) of this specific type.

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