EP0757110A1 - Method for heat treating railway track elements - Google Patents

Abstract

The heat treatment of a track element which is heated over its entire length and then cooled in a coolant bath in such a way that, if necessary, the element is dipped - with its head portion leading - partially and with interruptions into the bath. According to a predetermined time sequence, the element is alternatingly dipped completely and partially into the coolant bath.

Description

The invention relates to a method for heat or heat treatment of a track part, in particular a switch part such as a spring tongue or frog, the track part being heated over its length and then cooled in a coolant bath in such a way that the track part is optionally partially and interrupted and by its head is immersed in the coolant bath.

A method for the heat treatment of rails can be found in WO 94/02652. In order to avoid undesired hardening of the much thinner webs, the rail is partially immersed with its head in a coolant bath containing synthetic additives, the rail base being simultaneously cooled with compressed air and / or a water / air mixture. With such a process, desired hardness or hardness distributions can be achieved in the rail head, since the rail has the same cross sections over its entire length in the head region.

In order to achieve a fine pearlitic structure in the head region of a rail, according to EP 0 088 746 A1 the rail head is cooled by means of a cooling medium from a temperature in the austenite region to a temperature at which pearlite conversion is complete. Water with synthetic coolant additives such as polyglycol is used as the cooling medium. Also known from DE-C 582 957 is a method for tempering railroad tracks, in which the head alone is immersed once in a cooling liquid.

It is known from DE 25 41 978 C3 to compensate for track parts with changing cross-sectional shapes, in particular switch parts, in order to achieve a fine pearlitic structure. to heat the switch part to austenitizing temperature by means of a burner or inductor and then to blow compressed air only from above onto the switch parts standing on the base, the width of the compressed air jet corresponding at least to the size and width of the switch part. After completion of the pearlite transformation, the soft part can also be quenched with water.

DE-C-262 970 discloses a method and a device for achieving different degrees of hardness and toughness of elongated objects. To do this, the object is passed through various baths of oil and water.

The present invention is based on the problem of developing a method of the type described at the outset in such a way that rail parts, in particular with cross-sectional shapes that change along their length, can be reproducibly remanufactured, at least in the head region, preferably over the entire cross-section, to a desired structure, such as preferably fine pearlitic formation.

According to the invention, the problem is essentially solved in that the track part is immersed one after the other in regions and on the other hand completely in the coolant bath in a predetermined chronological sequence during cooling. When viewed in the longitudinal direction, the track part can be partially or completely immersed in the coolant bath at an angle to the coolant surface.

The teaching according to the invention makes the cooling rate more uniform over the cross section of the track part, it being possible to adapt to different cross-sectional shapes in that the track part is immersed alternately in regions or completely and / or inclined in the coolant. As a result, the compensation can be evened out over the entire cross-section and voltage differences can thus be largely avoided without the risk of undesired hardening occurring in the areas of the track part in which there are reduced cross-sections compared to the head area.

Through the teaching according to the invention, rail parts, in particular switch parts, are remunerated in their driving areas, finished machined rail parts being heat-treated. After Remuneration is then only necessary that necessary holes are drilled or, for example, a spring point is milled.

If necessary, the tab chambers can be filled with compensation tabs and / or inorganic products such as concrete, among other things, in order to prevent undesired cooling speeds of the track part in these critical areas.

The tempering process is followed by tempering treatment or stress relief annealing for targeted microstructure adjustment.

The necessary straightening processes are carried out at elevated temperatures to avoid changes in tension and structure.

In particular, the method according to the invention can be used for a track part made of steel grade 900A or 1100A according to UIC conditions.

• a) Eintauchen des Gleisteils allein mit seinem Kopfbereich über eine Zeit t₁,
• b) vollständiges Eintauchen des Gleisteils über eine Zeit t₂,
• c) Eintauchen des Gleisteils allein mit seinem Kopfbereich über eine Zeit t₃ und anschließendes Herausnehmen des Gleisteils aus dem Kühlmittelbad oder vorheriges ein- oder mehrmaliges Wiederholen der Tauchschritte b) und c), wobei gegebenenfalls dem Tauchschritt a) ein vollständiges Eintauchen des Gleisteils in das Kühlmittelbad vorausgeht.

Therefore, the invention is also characterized in that the track part is a tongue, a wing rail or the heart of a rail steel of quality 900A or S 1100V, the track part being heated to austenitizing temperature T _{II in order} to achieve a defined, fine pearlitic or martensitic structure, is kept at the temperature T _II for a time t _II , is then cooled in a controlled manner by immersion in a coolant bath, the track part being repeatedly immersed both in regions with its head region alone and completely in the coolant bath, and that the track part is then at a tempering temperature T _V of about 400 ° C V T _V ≦ 600 ° C over a period t _V of preferably 1 h ≦ t _V ≦ 3 h and then optionally directed at a temperature T _VI ≦ T _V , preferably T _VI ≦ 300 ° C. becomes. In particular, the track part is subjected to the immersion steps with regard to the cyclical complete or partial immersion in the coolant bath:

• a) immersing the track part alone with its head area over a time t ₁ ,
• b) complete immersion of the track part over a time t ₂ ,
• c) Immersing the track part alone with its head area over a time t ₃ and then removing the track part from the coolant bath or repeating the immersion steps b) and c) one or more times beforehand, with the immersion step a) possibly completely immersing the track part in the Coolant bath precedes.

The immersion times t ₁ , t ₃ , ... t _n-2 , t _n can be selected so that the track part is cooled in a targeted manner over its entire cross-section such that t ₁ ≦ t ₃ and / or t ₃ ≦ t ₅ and / or t _n-2 ≦ t _n , in particular t ₁ <t _n . In this way, necessary predetermined structures are reproducibly achieved.

In particular, the heat or heat treatment according to the invention can be used for a track part made of rail steel of a quality such as S 1100V or 900A or 1100 according to UIC 860V with a directional analysis of, for example
0.53-0.62% C, 0.15-0.25% Si, 0.65-1.1% Mn, 0.8-1.3% Cr, 0.05-0.11% Mo, 0.05 - 0.11% V, ≦ 0.02 P, optionally up to 0.025 Al, optionally 0.5% Nb, residual iron as well as usual contamination due to melting.
or
0.73 - 0.79% C, 0.86 - 0.99% Mn, 0.21 - 0.32% Si, 0.07 - 0.025% P, 0.08 - 0.022% S, 0.02 - 0.14% Cr and 0.000% Nb as well as residual iron and common melting-related impurities.

Further details, advantages and features of the invention result not only from the claims, the features to be extracted from them - individually and / or in combination - but also from the following description of preferred exemplary embodiments which can be found in the drawings.

Fig. 1

ein Temperatur-Zeit-Diagramm einer Wärme- bzw. Vergütebehandlung einer Flügelschiene,

Fig. 2

einen zeitlichen Verlauf eines Abschreckprozesses der Flügelschiene bei der Wärme- bzw. Vergütebehandlung nach Fig. 1,

Fig. 3

ein Temperatur-Zeit-Diagramm einer Wärme- bzw. Vergütebehandlung eines geschweißten Herzstücks,

Fig. 4

einen Abschreckprozeß des geschweißten Herzstückes während der Wärme- bzw. Vergütebehandlung gemäß Fig. 3 und

Fig. 5 - 7

Prinzipdarstellungen einer teilweise bzw. vollständig in einem Kühlmittelbad eingetauchten Weichenzunge.

Show it:

Fig. 1

a temperature-time diagram of a heat or heat treatment a Wing rail,

Fig. 2

1 shows a time course of a quenching process of the wing rail in the heat or heat treatment according to FIG. 1,

Fig. 3

a temperature-time diagram of a heat or heat treatment of a welded core,

Fig. 4

a quenching process of the welded core during the heat or heat treatment according to FIG. 3 and

5 - 7

Schematic diagrams of a switch tongue partially or completely immersed in a coolant bath.

In order to achieve a predetermined structure such as fine pearlitic (steel of grade 900A) or martensitic (steel of grade S 1100V) over the entire length of a track part with different cross-sectional areas, the track part - preferably several corresponding track parts at the same time - is preferably lying on its head the entire length is heated, for example in a gas-heated tempering furnace, to an austenitizing temperature T _II at a controllable rate and kept at this temperature for a predetermined time. The temperature T _II can be adjusted over a wide range of the steel brand used. Temperatures T _II between approximately 850 ° C and 900 ° C are possible.

Then all of the track parts are removed from the tempering furnace and there is a controlled immersion of the track parts in a quenching bath downstream of the tempering furnace, in which there is a water-miscible synthetic cooling medium. The track parts are subjected to a cyclic cooling process in such a way that the rail parts are alternately immersed in regions or completely in the coolant bath. The cooling process itself is determined by monitoring and limiting the process parameters such as concentration and temperature of the cooling medium, immersion cycle, immersion depth etc.

After the controlled cooling, a transformation into a given structure over the entire length of the rail, all the rail parts are removed from the coolant bath and the rail parts are again placed in an oven in order to be able to carry out a tempering treatment or stress relief annealing. As a result, all structural components that may occur due to the cross-section due to different cooling conditions are adapted to the specified structure. The guide parts can then be straightened from the starting heat in a temperature range depending on the steel brand. This temperature range can be just below 300 ° C, for example.

In order to achieve the predetermined structure at least in the driving area, preferably over the entire cross-section of the track part, a controlled quenching process of the following type is carried out according to the invention, whereby the cooling speed of the track part is made uniform over its entire cross-section. In order to ensure this also in the web area of the track parts, compensation tabs can be arranged in pairs.

1 and 2, the tempering method according to the invention is to be illustrated on the basis of a welded heart. The centerpiece was made of 900A rail steel in accordance with UIC conditions.

Even if several corresponding welded frogs are to be tempered at the same time, i.e. heated, quenched, tempered and cooled at the same time is always referred to below as a centerpiece or track part.

In the temperature-time diagram of FIG. 1, the rising edge I is intended to illustrate the heating of the track part to the austenitizing temperature. After reaching the austenitizing temperature, the track part is held at austenitizing temperature T _II for a predetermined period of time, in order to then be immediately quenched in a coolant bath, as a result of which the desired conversion into the predetermined structure takes place. This area is marked III in the diagram according to FIG. 1. This is followed by starting (flank IV) in order to then hold the track part over a period of time T _V , which can be, for example, 1-2 hours. This is followed by cooling in still air (falling flank VI), which may require straightening of the track part. This can be carried out in a temperature range that is just below 300 ° C.

According to the invention, the welded Herstück is cyclically partially or completely immersed in a coolant bath (10) containing water-miscible synthetic medium in such a way that a desired, uniform cooling takes place with the cross section of the frog.

In order to clarify the time sequence, the diving cycles are symbolized in FIG. 2 by a solid line (20), which runs with respect to the frog cross-sectional representations (12), (14), (16), (18) such that the frog either is only immersed in its head region or completely in the coolant bath (10). The cross sections (12), (14), (16) and (18) are further intended to illustrate that the centerpiece is always completely or partially immersed (head area) in the coolant bath (10) over its entire length.

wird das gesamte Gleisteil in das Kühlmittel eingetaucht, um sodann über eine Zeitdauer t₇ nur mit seinem Kopfbereich im Kühlmittel zu verbleiben. Nach Ablauf der Zeitspanne t₇ wird das Gleisteil vollständig aus dem Kühlmittelbad (10) entnommen, um auf eine Temperatur T_V zum Anlassen zu erwärmen und über einen Zeitraum t_V auf dieser Anlaßtemperatur T_V gehalten zu werden. Dabei kann T_V zwischen 400 und 550° C liegen. Der Zeitraum t_V kann 1 - 2 Stunden betragen. Dadurch entsteht das vorgegebene Gefüge und ein Spannungsausgleich über dem Querschnitt.In the exemplary embodiment illustrated by FIGS. 1 and 2, the track part is first immersed only with its head region over a period of time t ₁ . Over a subsequent, but shorter period of time t _{2, the track part} is completely immersed. Then the track part is partially raised from the coolant over a period t ₃ with t ₃ ≧ t ₁ , in order to again cool only the head region in the coolant bath (10). This is followed by a period of time t ₄ in which the track part is completely immersed, followed by an immersion of the head area alone over a period of time t ₅ ≧ t ₃ . Over a time t ₆ with preferably ${\text{t}}_{\text{2nd}}{\text{= t}}_{\text{6}}{\text{> t}}_{\text{4th}}$

the entire track part is immersed in the coolant in order then to remain in the coolant only with its head region over a period of time t ₇ . After the time interval t _7, the track part is removed completely from the coolant bath (10), to heat to a temperature T _V and for starting to be over a period t _V from this annealing temperature T _V maintained. T _V can be between 400 and 550 ° C. The period t _V can be 1 to 2 hours. This creates the specified structure and a tension compensation across the cross section.

3 and 4, a heat treatment of a wing rail (22) made of a material S 1100V is to be clarified in principle, with regard to heating to austenitizing temperature, holding to austenitizing temperature, tempering and cooling, in principle - if different in terms of time and temperature - Process takes place, which corresponds to that which has been illustrated with reference to FIGS. 1 and 2.

On the track part, i.e. adapted in the present case to the wing rail (22), however, there is a different chronological sequence of the quenching (flank III in FIG. 3), as shown in FIG. 4.

Thus, the wing rail (22) is first initially over a time period t ₀ completely into the coolant bath (10) immersed in order to then via one of the time duration t ₀ corresponding time t ₁ alone head in the coolant bath (10) to leave. This is followed by the complete or partial immersion of the wing rail (22) over the same time sequences t _2, t ₃ and t ₄ , and then over a period of time compared to the periods t ₀ or t ₁ or t ₂ or t ₃ and t ₄ t ₅ considerably longer period of time to leave only the head of the wing rail (22) in the coolant bath (10). The coolant bath (10) is then removed in order to leave the wing rail (22) on - in accordance with the procedure shown in FIG. 1. This is followed by cooling in still air (flank VI), whereby the wing rail (22) can be straightened. This temperature range can be just below 300 ° C.

If it has been made clear on the basis of FIGS. 1-4 that the slide parts are immersed either only in their head region or completely in the coolant bath (10) in a certain time sequence, then - as FIGS. 5-7 are intended to show - there is also the possibility of a track part such as, for example, a switch tongue (24) inclined towards the surface (26) of the coolant bath (10) to additionally take into account considerably different cross-sectional areas along the switch tongue (24). For example, according to FIG. 5, the switch tongue (24) is more immersed in the area of its end (28) than in the area of its beginning (30). After complete immersion (FIG. 6), the switch tongue (24) is then pulled out again from the coolant bath (10), the beginning (30) of the switch tongue (24) being complete, but the end (28) of which is still inside the coolant bath ( 10) runs. Regardless of this, however, there is an immersion sequence which corresponds in principle to that of FIGS. 2 and 4.

Claims (11)

Process for the heat or heat treatment of a track part, in particular a switch part such as a spring tongue or frog, the track part being heated over its entire length and then cooled in a coolant bath in such a way that the track part is optionally interrupted and immersed in the coolant bath from its head becomes,
characterized by
that the track part is successively immersed in a predetermined time sequence on the one hand in regions and on the other hand completely in the coolant bath. Method according to claim 1,
characterized by
that the track part, viewed in the longitudinal direction, is partially or completely immersed in the coolant bath at an angle to the coolant bath surface. The method of claim 1 or 2,
characterized by
that the track part after its removal from the coolant bath an annealing treatment or is subjected to stress relieving. Method according to at least one of the preceding claims,
characterized by
that the track part is preferably straightened after the tempering treatment or stress relief annealing at a temperature T _VI such as 250 ≦ T _VI Spannungs 300 ° C. Method according to at least one of the preceding claims,
characterized by
that the track part is subjected to the following dipping steps: a) immersing the track part alone with its head area over a time t ₁ , b) complete immersion of the track part over a time t ₂ , c) immersing the track part alone in its head area over a time t ₃ and then removing the track part from the coolant bath or repeating the immersion steps b) and c) one or more times beforehand, the immersion step a) possibly being preceded by a complete immersion of the track part in the coolant bath. Method according to at least one of the preceding claims,
characterized by
that if the head area of the track section is immersed several times at a time at the beginning of the cooling process (quenching process), the immersion of the head area is shorter in time than at the end of the quenching process. Method according to at least one of the preceding claims,
characterized by
that only the head region of the track part, calculated from the beginning of the cooling process, takes place over periods t ₁ , t ₃ , t ₅ , t ₇ , t _n-2 , t _n , where t ₁ ≦ t ₃ and / or t ₃ ≦ t ₅ and / or t _n-2 ≦ t _n is in particular t ₁ <t _n . Process for heat or heat treatment of a track part in the form of a switch part, preferably made of rail steel of quality 900A or S 1100V or 1100 according to UIC conditions,
characterized by
that the soft part is heated to austenitizing temperature T _II , is kept at temperature T _II for a time t _II , then is cooled in a coolant bath in order to achieve a predetermined structure, the soft part being alternated several times in the head area and then completely immersed in the coolant and vice versa, and that the switch part is then kept at a tempering temperature T _V for a period of time t _V and is then warmed and / or cooled. Process for heat or heat treatment of a track part in the form of a switch part,
characterized by
that is directed before the complete cooling at a temperature T _VI . Method according to at least one of the preceding claims,
characterized by
that several identical track parts are subjected to heat or heat treatment at the same time, the track part preferably being an essentially finished component. Method according to at least one of the preceding claims,
characterized by
that the switch part to austenitizing temperature T _II over a time t _II with 10 m ≦ t _II ≦ 30 m and / or at a tempering temperature T _V of approximately 400 ° ≦ T _V ≦ 600 ° C over a period t _V of approximately 1 h ≦ t _V ≦ 3 h and is preferably directed at a temperature T _VI of about 300 ° C.

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