EP0610460A1 - Rail thermal treatment process - Google Patents

Rail thermal treatment process

Info

Publication number
EP0610460A1
EP0610460A1 EP93914544A EP93914544A EP0610460A1 EP 0610460 A1 EP0610460 A1 EP 0610460A1 EP 93914544 A EP93914544 A EP 93914544A EP 93914544 A EP93914544 A EP 93914544A EP 0610460 A1 EP0610460 A1 EP 0610460A1
Authority
EP
European Patent Office
Prior art keywords
rail
coolant
cooling
synthetic
carried out
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP93914544A
Other languages
German (de)
French (fr)
Other versions
EP0610460B1 (en
Inventor
Alfred Moser
Georg Prskawetz
Peter Pointner
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Voestalpine Rail Technology GmbH
Original Assignee
Voestalpine Schienen GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Voestalpine Schienen GmbH filed Critical Voestalpine Schienen GmbH
Publication of EP0610460A1 publication Critical patent/EP0610460A1/en
Application granted granted Critical
Publication of EP0610460B1 publication Critical patent/EP0610460B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/04—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rails
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
    • C21D1/60—Aqueous agents
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/62—Quenching devices
    • C21D1/63—Quenching devices for bath quenching
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2221/00—Treating localised areas of an article
    • C21D2221/02—Edge parts

Definitions

  • the invention relates to a method for heat-treating rails, in particular the rail head, in which cooling is carried out in a coolant containing a synthetic coolant additive, starting from temperatures above 720 ° C.
  • a method of the type mentioned at the outset can be found, for example, in EP-PS 88 746.
  • synthetic coolant additives in the amount of 20 to 50% by weight, and in particular polyglycols, are used, the synthetic coolant additive primarily ensuring a uniformization of the cooling conditions while maintaining a reduced cooling rate.
  • Synthetic quenching agents are usually used in technology where a minimum cooling rate is required to set a martensitic structure.
  • the aim of such hardening is to harden the maximum cross-section, and in the case of objects which have different cross-sections, it naturally applies that the areas with smaller cross-sections are also completely hardened. In such applications, the workpiece can be left in the bath or hardening bath until the temperature is equalized.
  • the invention now aims to provide a method of the type mentioned at the beginning with which the optimum cooling speeds for the rail head can be maintained and at the same time it prevents the undesired hardening of the much thinner web from occurring.
  • the method according to the invention essentially consists in that the treatment is carried out by immersion in the coolant until a surface temperature of between 450.degree. C. and 550.degree.
  • the fact that the drawing is carried out at a point in time at which the immersed areas have reached a surface temperature between 450 and 550 ° C. without temperature compensation over the entire cross section ensures that the drawing is early enough to form a hardness structure in the jetty with certainty to be excluded.
  • the measure according to the invention being used as a criterion for the timeliness of the pulling, the achievement of a surface temperature between 450 and 550 ° C., here together with the fact the fact that a synthetic coolant additive is used means that the cooling rate in the head is low enough to reliably avoid hardening in the web.
  • the use of a synthetic coolant additive ensures a reduction in the cooling rate, but also a sufficiently high cooling rate, which ensures the formation of a high-strength, fine pearlitic structure in the rail head.
  • the process according to the invention is advantageously carried out in such a way that synthetic additives, such as, for example, glycols or polyglycols, are added to the coolant to an extent which transitions at a bath temperature between 35-55 ° C from film boiling to the boiling phase at a surface temperature of approx. 500 ° C. and the desired time for pulling the rails results from this.
  • synthetic additives preferably glycols and polyglycols
  • the use of synthetic additives, preferably glycols and polyglycols to an extent which ensures that the correct time for pulling the splint is indicated by a boiling of the bath, ensures that consistent and optimal results are guaranteed for both the rail head and the web.
  • the workpiece When reaching or just after reaching the boiling point, the workpiece must be pulled if excessive cooling is to be avoided and the film boiling adjusted in such a way that the head region of the rail is optimal to a depth of approximately 20 to 25 mm If pearlite formation can be achieved, after drawing, the lower lying areas are subsequently converted into pearlite, and conversely, if the workpiece were left in the bath after film boiling, it would form due to the rapid cooling which now begins would come from martensite. After reaching the boiling point, the further cooling outside the bath can be carried out slowly enough to ensure complete pearlite formation, which, as already mentioned, could no longer be ensured after the boiling had been reached due to the much faster cooling in the bath. Such a faster cooling rate in the bathroom would also have the consequence that, above all, the smaller cross-section of the web would be hardened more quickly and it undesirable martensite formation would occur, which naturally increases the risk of breakage.
  • the process is carried out by selecting the appropriate amount of the synthetic coolant in the coolant and the exact determination of the point in time at which the immersed areas must be drawn in order to prevent undesired hardening of other areas.
  • the proportion of synthetic additives in the coolant determines the time of the transition from film boiling to boiling phase, the setting of the constellation having to be such that the boiling phase is only reached in the last cooling phase before drawing in order to ensure uniform cooling.
  • the set concentration must be kept constant over a corresponding control system - which is not necessary with the usual use of the agent according to the known state of the art - in order to ensure that this concentration, which is necessary for the detection of the timely drawing is essential, is not subject to fluctuations. The same applies to the bath temperature.
  • the bath circulation must be kept constant contrary to the known prior art. With regard to the flow velocity of the medium onto the rolling stock or the rail to be cooled, it should be noted that this must be as constant as possible over the entire length of the rolling stock or the rail and over the entire duration of the heat treatment in the present case. Because with the known methods for hardening, where the austenitic structure is fully immersed, it is sufficient to adhere only to a lower limit of this parameter in order to obtain the hardening effect.
  • the method according to the invention relates to an optimum combination for partial diving between the diving temperature and the diving time, the rail having a surface temperature between 450 and 550 ° C. at the end of cooling, with no temperature compensation over the entire cross section.
  • the procedure can be such that the rail foot is cooled with compressed air and / or a water / air mixture.
  • the method according to the invention is advantageously applied to a steel with the directional analysis 0.65-0.85% C, 0.01-1.2% Si, 0.5-3.5% Mn, 0.01-1.0% Cr, rest Fe and usual impurities applied.
  • FIG. 1 shows a section through a splint treated according to the inventive method, the hardness distribution HB being shown for different zones; and
  • FIG. 2 shows a diagram of the hardness distribution as a function of the distance from the center of the running surface in the direction of the rail web.
  • the rail or the rail head are immersed at a temperature of 820 ° C. in a coolant containing a synthetic coolant additive, the depth of the head being approximately 37 mm.
  • a bath temperature of 50 ° C and a selected bath concentration of 35% After a dipping time of 150 s there is a surface or reheating temperature of 505 ° C, this surface temperature being maintained or the immersed areas being drawn into one Time is made without that there was a temperature compensation over the entire rail or head cross-section.
  • the hardness distribution that can be achieved with such a method is shown for a rail profile UIC 60 in FIG. 1, the hardness distribution HB being specified for different areas. It is clear that the rail head has correspondingly higher hardness values than the rail web and the rail foot.
  • the diagram shown in FIG. 2 shows, depending on the distance from the center of the running surface in millimeters, the hardness distribution HB 30 that can be achieved with the method for the heat treatment of rails.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Physics & Mathematics (AREA)
  • Heat Treatment Of Articles (AREA)
  • Magnetic Heads (AREA)
  • Heat Treatments In General, Especially Conveying And Cooling (AREA)
  • Furnace Charging Or Discharging (AREA)
  • Control Of Heat Treatment Processes (AREA)
  • Excavating Of Shafts Or Tunnels (AREA)
  • Manufacturing Of Magnetic Record Carriers (AREA)

Abstract

A method for the thermal treatment of rails, in particular of the rail head, in which cooling is carried out in a cooling agent that contains a synthetic cooling agent additive, starting at temperatures above 720° C. The treatment is carried out by immersion in the cooling agent until withdrawl of the immersed areas, courses, at a surface temperature between 450 and 550° C. results without temperature equalization across the whole of the cross-section, section, there by avoiding hardening of the rail web whilst maintaining an optimal cooling rate for the rail head.

Description

Verfahren zum Wärmebehandeln von SchienenProcess for heat treating rails
Die Erfindung bezieht sich auf ein Verfahren zum Wärmebehan¬ deln von Schienen, insbesondere des Schienenkopfes, bei welchem in einem einen synthetischen Kühlmittelzusatz enthal¬ tenden Kühlmittel ausgehend von Temperaturen über 720°C gekühlt wird.The invention relates to a method for heat-treating rails, in particular the rail head, in which cooling is carried out in a coolant containing a synthetic coolant additive, starting from temperatures above 720 ° C.
Ein Verfahren der eingangs genannten Art ist beispielsweise der EP-PS 88 746 zu entnehmen. Bei diesem bekannten Verfahren werden synthetische Kühlmittelzusätze im Ausmaß von 20 bis 50 Gew.-%, und im besonderen Polyglykole, eingesetzt, wobei der synthetische Kühlmittelzusatz in erster Linie eine Ver¬ gleichmäßigung der Abkühlungsbedingungen bei Einhaltung einer verringerten Abkühlungsgeschwindigkeit gewährleistet. Synthe¬ tische Abschreckmittel werden üblicherweise in der Technik angewandt, wo die Einhaltung einer minimalen Abkühlungsge¬ schwindigkeit zur Einstellung eines martensitischen Gefüges gefordert, wird. Ziel einer derartigen Härtung ist es, den maximalen Querschnitt durchzuhärten, und bei Gegenständen, welche unterschiedliche Querschnitte aufweisen, gilt natur¬ gemäß, daß auch die Bereiche mit kleineren Querschnitten voll¬ ständig durchgehärtet werden. Bei derartigen Anwendungen kann das Werkstück bis zum Temperaturausgleich im Bad bzw. Härtebad belassen werden.A method of the type mentioned at the outset can be found, for example, in EP-PS 88 746. In this known method, synthetic coolant additives in the amount of 20 to 50% by weight, and in particular polyglycols, are used, the synthetic coolant additive primarily ensuring a uniformization of the cooling conditions while maintaining a reduced cooling rate. Synthetic quenching agents are usually used in technology where a minimum cooling rate is required to set a martensitic structure. The aim of such hardening is to harden the maximum cross-section, and in the case of objects which have different cross-sections, it naturally applies that the areas with smaller cross-sections are also completely hardened. In such applications, the workpiece can be left in the bath or hardening bath until the temperature is equalized.
Bei der Verwendung synthetischer Abschreckmittel im Zusammen¬ hang mit der Wärmebehandlung von Schienen ist dabei eine Auf¬ härtung des Schienensteges keineswegs wünschenswert. Darüber hinaus wird ein Feinperlitisieren angestrebt und bei einem derartigen Feinperlitisieren ist die Einhaltung einer maxi¬ malen Abkühlungsgeschwindigkeit erforderlich. Wenn aber, wie beim bekannten Verfahren, die optimale Abkühlungsgeschwindig¬ keit im Schienenkopf eingestellt wird, welche ein fein- perlitisches Gefüge ohne Martensit und Perlit ermöglicht, würde dies bedeuten, daß die Abkühlungsgeschwindigkeit für den wesentlich dünneren Schienensteg bereits wesentlich zu hoch ist.When using synthetic quenching agents in connection with the heat treatment of rails, hardening of the rail web is in no way desirable. In addition, fine pearlizing is sought, and in the case of such fine pearlizing it is necessary to maintain a maximum cooling rate. If, however, as in the known method, the optimum cooling speed is set in the rail head, which enables a fine pearlitic structure without martensite and pearlite, this would mean that the cooling speed for the much thinner rail web is already much too high.
Die Erfindung zielt nun darauf ab, ein Verfahren der eingangs genannten Art zu schaffen, mit welchem die optimalen Abküh¬ lungsgeschwindigkeiten für den Schienenkopf eingehalten werden können und gleichzeitig verhindert wird, daß eine unerwünschte Aufhärtung des wesentlich dünneren Steges erfolgt. Zur Lösung dieser Aufgabe besteht das erfindungsgemäße Verfahren im wesentlichen darin, daß die Behandlung durch Eintauchen in das Kühlmittel solange vorgenommen wird, bis sich nach dem Ziehen der eingetauchten Bereiche eine Oberflächentemperatur zwischen 450°C und 550°C ohne Temperaturausgleich über den gesamten Querschnitt ergibt. Dadurch, daß das Ziehen zu einem Zeitpunkt vorgenommen wird, bei welchem die eingetauchten Bereiche eine Oberflächentemperatur zwischen 450 und 550°C ohne Temperatur¬ ausgleich über den gesamten Querschnitt erreicht haben, wird sichergestellt, daß das Ziehen frühzeitig genug ist, um die Ausbildung eines Härtegefüges im Steg mit Sicherheit auszu- schließen. Wenn nämlich der Temperaturausgleich abgewartet würde, käme es mit Sicherheit zu einer unerwünschten Auf- härtung im Steg, wobei die erfindungsgemäße Maßnahme als Kriterium für die Rechtzeitigkeit des Ziehens, die Erzielung einer Oberflächentemperatur zwischen 450 und 550°C anzusetzen, hier gemeinsam mit dem Umstand, daß ein synthetischer Kühlmittelzusatz eingesetzt wird, dazu führt, daß die Abküh¬ lungsgeschwindigkeit im Kopf niedrig genug ist, um im Steg eine Aufhärtung mit Sicherheit zu vermeiden. Gleichzeitig wird aber durch die Verwendung eines synthetischen Kühlmittel- zusatzes zwar eine Verringerung der Abkühlgeschwindigkeit aber auch eine hinreichend hohe Abkühlgeschwindigkeit sicherge¬ stellt, welche die Ausbildung eines hochfesten, fein- perlitischen Gefüges im Schienenkopf gewährleistet. Mit Vor¬ teil wird hiebei das erfindungsgemäße Verfahren so durchge- führt, daß dem Kühlmittel synthetische Zusätze, wie z.B. Glykole oder Polyglykole, in einem Ausmaß zugesetzt werden, welches bei einer Badtemperatur zwischen 35-55°C den Übergang vom Filmsieden in die Kochphase bei einer Oberflächentempera¬ tur von ca. 500°C aufweist und sich daraus der gewünschte Zeitpunkt für das ziehen der Schienen ergibt. Insbesondere durch den Einsatz von synthetischen Zusätzen, vorzugsweise von Glykolen und Polyglykolen, in einem Ausmaß, welches sicher¬ stellt, daß der korrekte Zeitpunkt für das Ziehen der Schiene durch ein Sieden des Bades angezeigt wird, wird sicher¬ gestellt, daß gleichbleibende und optimale Ergebnisse sowohl für den Schienenkopf als auch für den Steg gewährleistet sind. Wenn nämlich an der Oberfläche der Schiene bei entsprechender Wahl des Anteiles an synthetischen Zusätzen der Kochpunkt ein¬ setzt, sind die tiefer liegenden Bereiche mit Sicherheit noch nicht in Perlit umgewandelt. Bis zum Erreichen des Kochpunktes erfolgt ein relativ langsameres Abkühlen gegen einem Abkühlen in einem Bad ohne die synthetischen Kühlmittelzusätze. Erst ab Erreichen der Kochphase steigt die Abkühlgeschwindigkeit rasch an, so daß der Kochpunkt eine relativ charakteristische Grenze für den Übergang von relativ langsamer zu relativ rascher Abkühlung .im Bad signalisiert. Bei Erreichen oder knapp nach dem Erreichen des Kochpunktes muß das Werkstück gezogen werden, wenn eine übermäßig rasche Abkühlung vermieden werden soll, und die Einstellung des Filmsiedens in einer Weise, daß der Kopfbereich der Schiene bis in eine Tiefe von ca. 20 bis 25 mm optimale Perlitbildung erzielen läßt, führt nach dem Ziehen dazu, daß die tieferliegenden Bereiche in der Folge noch in Perlit umgewandelt werden, wobei umgekehrt dann, wenn das Werkstück nach Erreichen des Filmsiedens im Bad belassen würde, es aufgrund der nunmehr einsetzenden rascheren Abküh¬ lung zur Ausbildung von Martensit kommen würde. Nach dem Erreichen des Kochpunktes kann die weitere Abkühlung außerhalb des Bades entsprechend langsam genug geführt werden, um eine vollständige Perlitbildung sicherzustellen, was, wie bereits erwähnt, nach Erreichen des Kochens durch die wesentlich raschere Abkühlung im Bad nicht mehr sichergestellt werden könnte. Eine derartige raschere Abkühlungsgeschwindigkeit im Bad hätte darüber hinaus zur Folge, daß vor allen Dingen der geringere Stegquerschnitt rascher aufgehärtet würde und es doch zu unerwünschter Martensitbildung kommen würde, wodurch die Bruchgefahr naturgemäß erhöht wird.The invention now aims to provide a method of the type mentioned at the beginning with which the optimum cooling speeds for the rail head can be maintained and at the same time it prevents the undesired hardening of the much thinner web from occurring. To achieve this object, the method according to the invention essentially consists in that the treatment is carried out by immersion in the coolant until a surface temperature of between 450.degree. C. and 550.degree. The fact that the drawing is carried out at a point in time at which the immersed areas have reached a surface temperature between 450 and 550 ° C. without temperature compensation over the entire cross section ensures that the drawing is early enough to form a hardness structure in the jetty with certainty to be excluded. If the temperature equalization were to be waited for, there would certainly be an undesired hardening in the web, the measure according to the invention being used as a criterion for the timeliness of the pulling, the achievement of a surface temperature between 450 and 550 ° C., here together with the fact the fact that a synthetic coolant additive is used means that the cooling rate in the head is low enough to reliably avoid hardening in the web. At the same time, however, the use of a synthetic coolant additive ensures a reduction in the cooling rate, but also a sufficiently high cooling rate, which ensures the formation of a high-strength, fine pearlitic structure in the rail head. The process according to the invention is advantageously carried out in such a way that synthetic additives, such as, for example, glycols or polyglycols, are added to the coolant to an extent which transitions at a bath temperature between 35-55 ° C from film boiling to the boiling phase at a surface temperature of approx. 500 ° C. and the desired time for pulling the rails results from this. In particular, the use of synthetic additives, preferably glycols and polyglycols, to an extent which ensures that the correct time for pulling the splint is indicated by a boiling of the bath, ensures that consistent and optimal results are guaranteed for both the rail head and the web. If the boiling point starts on the surface of the rail with a corresponding choice of the proportion of synthetic additives, the deeper lying areas are certainly not yet converted to pearlite. Until the boiling point is reached, cooling takes place relatively more slowly than cooling in a bath without the synthetic coolant additives. Only after reaching the cooking phase does the cooling rate increase rapidly, so that the cooking point signals a relatively characteristic limit for the transition from relatively slow to relatively rapid cooling in the bathroom. When reaching or just after reaching the boiling point, the workpiece must be pulled if excessive cooling is to be avoided and the film boiling adjusted in such a way that the head region of the rail is optimal to a depth of approximately 20 to 25 mm If pearlite formation can be achieved, after drawing, the lower lying areas are subsequently converted into pearlite, and conversely, if the workpiece were left in the bath after film boiling, it would form due to the rapid cooling which now begins would come from martensite. After reaching the boiling point, the further cooling outside the bath can be carried out slowly enough to ensure complete pearlite formation, which, as already mentioned, could no longer be ensured after the boiling had been reached due to the much faster cooling in the bath. Such a faster cooling rate in the bathroom would also have the consequence that, above all, the smaller cross-section of the web would be hardened more quickly and it undesirable martensite formation would occur, which naturally increases the risk of breakage.
Wesentlich für das erfindungsgemäße Verfahren ist somit die Verfahrensführung durch Wahl der geeigneten Menge des synthe¬ tischen Kühlmittels im Kühlmittel und die exakte Bestimmung des Zeitpunktes, zu welchem ein ziehen der eingetauchten Bereiche erfolgen muß, um eine unerwünschte Aufhärtung anderer Bereiche zu verhindern. Der Anteil der synthetischen Zusätze im Kühlmittel bestimmt den Zeitpunkt des Überganges Filmsieden - Kochphase, wobei die Einstellung der Konstellation so erfolgen muß, daß die Kochphase erst in der letzten Abkühl¬ phase vor dem Ziehen erreicht wird, um eine gleichmäßige Kühlung zu sichern. Die eingestellte Konzentration muß hiebei über ein entsprechendes Regelsystem laufend - was bei üblicher Anwendung des Mittels gemäß dem bekannten Stand der Technik nich notwendig ist - konstant gehalten werden, um sicherzu¬ stellen, daß auch im Zuge des Verfahrens diese Konzentration, die für das Erkennen des rechtzeitigen Ziehens wesentlich ist, keinen Schwankungen unterworfen ist. Analoges gilt für die Badtemperatur.It is therefore essential for the process according to the invention that the process is carried out by selecting the appropriate amount of the synthetic coolant in the coolant and the exact determination of the point in time at which the immersed areas must be drawn in order to prevent undesired hardening of other areas. The proportion of synthetic additives in the coolant determines the time of the transition from film boiling to boiling phase, the setting of the constellation having to be such that the boiling phase is only reached in the last cooling phase before drawing in order to ensure uniform cooling. The set concentration must be kept constant over a corresponding control system - which is not necessary with the usual use of the agent according to the known state of the art - in order to ensure that this concentration, which is necessary for the detection of the timely drawing is essential, is not subject to fluctuations. The same applies to the bath temperature.
Die Badumwälzung muß entgegen dem bekannten Stand der Technik konstant gehalten werden. Bezüglich der Anströmgeschwindigkeit des Mediums auf das abzukühlende Walzgut bzw. die Schiene ist festzuhalten, daß diese im gegenständlichen Fall über die gesamte Länge des Walzgutes bzw. der Schiene und über die gesamte Dauer der Wärmebehandlung möglichst konstant sein muß. Denn bei den bekannten Verfahren für das Härten, wo aus dem austenitischen Gefügezustand voll getaucht wird, genügt es, nur eine untere Grenze dieses Parameters einzuhalten, um den Härteeffekt zu erhalten. Das erfindungsgemäße Verfahren dagegen betrifft eine für das partielle Tauchen optimale Kombination zwischen Tauchtemperatur und Tauchzeit, wobei die Schiene am Ende der Abkühlung eine Oberflächentemperatur zwischen 450 bis 550°C aufweist, wobei es zu keinem Tempera¬ turausgleich über den gesamten Querschnitt kommt. Während des partiellen Tauchens der Schienen und des Ein¬ tauchens des Schienenkopfes kann so vorgegangen werden, daß der Schienenfuß mit Preßluft und/oder einem Wasser-Luftgemisch gekühlt wird. Mit Vorteil wird das erfindungsgemäße Verfahren auf einen Stahl mit der Richtanalyse 0,65-0,85 % C, 0,01 - 1,2 % Si, 0,5-3,5 % Mn, 0,01 - 1,0 % Cr, Rest Fe und übliche Verunreinigungen angewendet.The bath circulation must be kept constant contrary to the known prior art. With regard to the flow velocity of the medium onto the rolling stock or the rail to be cooled, it should be noted that this must be as constant as possible over the entire length of the rolling stock or the rail and over the entire duration of the heat treatment in the present case. Because with the known methods for hardening, where the austenitic structure is fully immersed, it is sufficient to adhere only to a lower limit of this parameter in order to obtain the hardening effect. The method according to the invention, on the other hand, relates to an optimum combination for partial diving between the diving temperature and the diving time, the rail having a surface temperature between 450 and 550 ° C. at the end of cooling, with no temperature compensation over the entire cross section. During the partial immersion of the rails and the immersion of the rail head, the procedure can be such that the rail foot is cooled with compressed air and / or a water / air mixture. The method according to the invention is advantageously applied to a steel with the directional analysis 0.65-0.85% C, 0.01-1.2% Si, 0.5-3.5% Mn, 0.01-1.0% Cr, rest Fe and usual impurities applied.
Die Wahl der korrekten Konzentration für den synthetischen Kühlmittelzusatz und die Maßnahme, das Ziehen zu einem defi¬ nierten Zeitpunkt, nämlich dem Übergang vom Filmsieden in die Kochphase vorzunehmen, ergibt insgesamt auch bei unterschied¬ lichen Schienenprofilen jeweils optimale Ergebnisse in bezug auf die Gefügeausbildung nach der Wärmebehandlung.The choice of the correct concentration for the synthetic coolant additive and the measure of pulling at a defined point in time, namely the transition from film boiling to the boiling phase, gives optimal results with regard to the structure of the structure, even with different rail profiles Heat treatment.
Die Erfindung wird nachfolgend anhand eines Ausführungsbei- spieles des erfindungsgemäßen Verfahrens näher erläutert, wobei in der Zeichnung die mit dem erfindungsgemäßen Verfahren zum Wärmebehandeln erzielbaren Härtewerte näher dargestellt sind. In dieser zeigen Fig.l einen Schnitt durch eine gemäß dem erfindungsgemäßen Verfahren behandelte Schiene, wobei die Härteverteilung HB für unterschiedliche Zonen dargestellt ist; und Fig.2 ein Diagramm der Härteverteilung in Abhängigkeit vom Abstand von der Fahrflächenmitte aus in Richtung Schienensteg.The invention is explained in more detail below on the basis of an exemplary embodiment of the method according to the invention, the hardness values achievable with the method according to the invention for heat treatment being shown in more detail in the drawing. 1 shows a section through a splint treated according to the inventive method, the hardness distribution HB being shown for different zones; and FIG. 2 shows a diagram of the hardness distribution as a function of the distance from the center of the running surface in the direction of the rail web.
Bei der Durchführung eines Verfahrens zur Wärmebehandlung von Schienen, insbesondere des Schienenkopfes, werden beispiels¬ weise folgende Parameter eingehalten. Die Schiene bzw. der Schienenkopf werden mit einer Temperatur von 820°C in ein einen synthetischen Kühlmittelzusatz enthaltendes Kühlmittel getaucht, wobei die Tauchtiefe des Kopfes etwa 37 mm beträgt. Bei einer Badtemperatur von 50°C und einer gewählten Badkon¬ zentration von 35% ergibt sich nach einer Tauchzeit von 150 s eine Oberflächen- bzw. Rückwärmtemperatur von 505°C, wobei diese Oberflächentemperatur erhalten bzw. das Ziehen der ein¬ getauchten Bereiche zu einem Zeitpunkt vorgenommen wird, ohne daß ein Temperaturausgleich über den gesamten Schienen- bzw. Kopfquerschnitt erfolgte.When carrying out a method for the heat treatment of rails, in particular the rail head, the following parameters are observed, for example. The rail or the rail head are immersed at a temperature of 820 ° C. in a coolant containing a synthetic coolant additive, the depth of the head being approximately 37 mm. With a bath temperature of 50 ° C and a selected bath concentration of 35%, after a dipping time of 150 s there is a surface or reheating temperature of 505 ° C, this surface temperature being maintained or the immersed areas being drawn into one Time is made without that there was a temperature compensation over the entire rail or head cross-section.
Die mit einem derartigen Verfahren erzielbare Härteverteilung ist für ein Schienenprofil UIC 60 in Fig.l dargestellt, wobei für unterschiedliche Bereiche die Härteverteilung HB angegeben ist. Es ergibt sich deutlich, daß der Schienenkopf entspre¬ chend höhere Härtewerte als der Schienensteg und der Schienen¬ fuß aufweist.The hardness distribution that can be achieved with such a method is shown for a rail profile UIC 60 in FIG. 1, the hardness distribution HB being specified for different areas. It is clear that the rail head has correspondingly higher hardness values than the rail web and the rail foot.
In dem in Fig.2 dargestellten Diagramm ist in Abhängigkeit vom Abstand von der Fahrflächenmitte in Millimetern die mit dem Verfahren zum Wärmebehandeln von Schienen erzielbare Härtever¬ teilung HB 30 dargestellt.The diagram shown in FIG. 2 shows, depending on the distance from the center of the running surface in millimeters, the hardness distribution HB 30 that can be achieved with the method for the heat treatment of rails.
Insgesamt ergibt sich, daß durch die Tatsache, daß das Ziehen des eingetauchten Werkstückes bzw. des Schienenkopfes vor dem Zeitpunkt erfolgt, bevor der gesamte Querschnitt¬ temperaturausgleich erfolgte, ein unerwünschtes Härten des Steges mit Sicherheit vermieden wird, während der Schienenkopf die gewünschte Härte bzw. Härteverteilung aufweist. Overall, it follows that the fact that the immersed workpiece or the rail head is pulled before the point in time before the entire cross-sectional temperature compensation takes place, an undesired hardening of the web is reliably avoided, while the rail head has the desired hardness or Hardness distribution.

Claims

Patentansprüche: Claims:
1. Verfahren zum Wärmebehandeln von Schienen, insbesondere des Schienenkopfes, bei welchem in einem einen synthetischen Kühl- mittelzusatz enthaltenden Kühlmittel ausgehend von Tempera¬ turen über 720°C gekühlt wird, dadurch gekennzeichnet, daß die Behandlung durch Eintauchen in das Kühlmittel solange vorge¬ nommen wird, bis sich nach dem ziehen der eingetauchten Bereiche eine Oberflächentemperatur zwischen 450°C und 550°C ohne Temperaturausgleich über den gesamten Querschnitt ergibt.1. A process for the heat treatment of rails, in particular the rail head, in which cooling is carried out in a coolant containing a synthetic coolant additive, starting from temperatures above 720 ° C, characterized in that the treatment is carried out by immersing it in the coolant for as long as possible until a surface temperature of between 450 ° C and 550 ° C is obtained without temperature compensation across the entire cross-section after the immersed areas have been drawn.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß dem Kühlmittel synthetische Zusätze, wie z.B. Glykole oder Poly- glykole, in einem Ausmaß zugesetzt werden, welches bei einer Badtemperatur zwischen 35-55°C den Übergang vom Filmsieden in die Kochphase bei einer Oberflächentemperatur zwischen 450 bis 550°C aufweist und sich daraus der gewünschte Zeitpunkt für das Ziehen der Schiene ergibt.2. The method according to claim 1, characterized in that the coolant synthetic additives, such as. Glycols or polyglycols are added to an extent which, at a bath temperature between 35-55 ° C, has the transition from film boiling to the boiling phase at a surface temperature between 450 to 550 ° C and is the desired time for pulling the rail results.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß der Schienenfuß mit Preßluft und/oder einem Wasser-Luftge¬ misch gekühlt wird.3. The method according to claim 1 or 2, characterized in that the rail foot is cooled with compressed air and / or a water-air mixture.
4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekenn- zeichnet, daß ein Stahl mit der Richtanalyse 0,65-0,85 % C, 0,01 - 1,2 % Si, 0,5-3,5 % Mn, 0,01 - 1,0 % Cr, Rest Fe und übliche Verunreinigungen der Wärmebehandlung unterworfen wird. 4. The method according to any one of claims 1 to 3, characterized in that a steel with the directional analysis 0.65-0.85% C, 0.01-1.2% Si, 0.5-3.5% Mn, 0.01-1.0% Cr, rest Fe and usual impurities are subjected to the heat treatment.
EP93914544A 1992-07-15 1993-07-09 Rail thermal treatment process Expired - Lifetime EP0610460B1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
AT1455/92 1992-07-15
AT145592 1992-07-15
AT0145592A AT399346B (en) 1992-07-15 1992-07-15 METHOD FOR TREATING RAILS
PCT/AT1993/000116 WO1994002652A1 (en) 1992-07-15 1993-07-09 Rail thermal treatment process

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EP0610460A1 true EP0610460A1 (en) 1994-08-17
EP0610460B1 EP0610460B1 (en) 1999-10-20

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KR (1) KR0134900B1 (en)
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CA (1) CA2116216C (en)
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RU (1) RU94019951A (en)
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AT402941B (en) 1994-07-19 1997-09-25 Voest Alpine Schienen Gmbh METHOD AND DEVICE FOR THE HEAT TREATMENT OF PROFILED ROLLING MATERIAL
IN191289B (en) 1994-07-19 2003-11-01 Voest Alpine Schienen Gmbh
DE69523149T2 (en) 1994-11-15 2002-06-20 Nippon Steel Corp., Tokio/Tokyo PERLITE RAIL WITH HIGH ABRASION RESISTANCE AND METHOD FOR THE PRODUCTION THEREOF
CN1083013C (en) * 1996-09-29 2002-04-17 攀枝花钢铁(集团)公司 Heat treatment method and device for producing high-strength steel rail by using rolling waste heat
AT407057B (en) * 1996-12-19 2000-12-27 Voest Alpine Schienen Gmbh PROFILED ROLLING MATERIAL AND METHOD FOR THE PRODUCTION THEREOF
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JP5145795B2 (en) * 2006-07-24 2013-02-20 新日鐵住金株式会社 Method for producing pearlitic rails with excellent wear resistance and ductility
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US20010023724A1 (en) 2001-09-27
US6547897B2 (en) 2003-04-15
US6406569B1 (en) 2002-06-18
DE59309839D1 (en) 1999-11-25
LV11192B (en) 1996-06-20
ATE185845T1 (en) 1999-11-15
WO1994002652A1 (en) 1994-02-03
CA2116216A1 (en) 1994-02-03
AT399346B (en) 1995-04-25
CZ283571B6 (en) 1998-05-13
HRP931054B1 (en) 2000-02-29
CZ56394A3 (en) 1994-06-15
CA2116216C (en) 2001-09-18
CN1085258A (en) 1994-04-13
EP0610460B1 (en) 1999-10-20
ATA145592A (en) 1994-09-15
SK29494A3 (en) 1994-11-09
PL175451B1 (en) 1998-12-31
UA26282C2 (en) 1999-07-19
ES2139661T3 (en) 2000-02-16
TW259818B (en) 1995-10-11
LV11192A (en) 1996-04-20
CN1040232C (en) 1998-10-14
LTIP797A (en) 1994-03-25
KR0134900B1 (en) 1998-06-15
MD940198A (en) 1996-01-31
BR9305583A (en) 1996-01-02
RU94019951A (en) 1996-04-10
HRP931054A2 (en) 1995-06-30
LT3008B (en) 1994-08-25
PL302766A1 (en) 1994-08-22
SK281598B6 (en) 2001-05-10

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