EP0161236B1 - Apparatus for manufacturing rails - Google Patents
Apparatus for manufacturing rails Download PDFInfo
- Publication number
- EP0161236B1 EP0161236B1 EP85870064A EP85870064A EP0161236B1 EP 0161236 B1 EP0161236 B1 EP 0161236B1 EP 85870064 A EP85870064 A EP 85870064A EP 85870064 A EP85870064 A EP 85870064A EP 0161236 B1 EP0161236 B1 EP 0161236B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- rail
- cooling
- rollers
- bead
- guide rollers
- 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.)
- Expired - Lifetime
Links
- 238000004519 manufacturing process Methods 0.000 title claims description 7
- 238000001816 cooling Methods 0.000 claims abstract description 62
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 16
- 238000005096 rolling process Methods 0.000 claims description 5
- 230000009466 transformation Effects 0.000 abstract description 27
- 239000010451 perlite Substances 0.000 abstract description 9
- 238000005098 hot rolling Methods 0.000 abstract description 4
- 239000011324 bead Substances 0.000 description 67
- 238000000034 method Methods 0.000 description 22
- 230000004907 flux Effects 0.000 description 17
- 229910000831 Steel Inorganic materials 0.000 description 16
- 239000010959 steel Substances 0.000 description 16
- 230000008569 process Effects 0.000 description 14
- 239000011572 manganese Substances 0.000 description 12
- 239000000203 mixture Substances 0.000 description 9
- 238000009434 installation Methods 0.000 description 8
- 229910000734 martensite Inorganic materials 0.000 description 8
- 235000021183 entrée Nutrition 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 7
- 229910052748 manganese Inorganic materials 0.000 description 7
- 229910001566 austenite Inorganic materials 0.000 description 6
- 235000019362 perlite Nutrition 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 5
- 238000012360 testing method Methods 0.000 description 4
- 230000001052 transient effect Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 240000008042 Zea mays Species 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 229910001563 bainite Inorganic materials 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 238000009864 tensile test Methods 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 238000013178 mathematical model Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- -1 pad Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Images
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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/62—Quenching devices
- C21D1/667—Quenching devices for spray quenching
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
- B21B45/0203—Cooling
- B21B45/0209—Cooling devices, e.g. using gaseous coolants
- B21B45/0215—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes
-
- 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
- C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/08—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling structural sections, i.e. work of special cross-section, e.g. angle steel
- B21B1/085—Rail sections
Definitions
- the present invention relates to a device for manufacturing rails, and in particular high resistance rails, by cooling the rails as soon as they leave the last stand of the rolling mill, that is to say in the hot rolling.
- Its object is to obtain, preferably without adding alloying elements to the steel, rails having, after cooling, a high breaking strength, good wear resistance, good resistance impact, elongation at least equal to 10% and good weldability.
- high strength steels it is especially meant steels containing 0.4% to 0.85% of C, 0.4% to 1% of Mn and 0.1% to 0.4% of Si and preferably 0 , 6% to 0.85% C and 0.6% to 0.8% Mn; where appropriate, these steels can contain up to 1% of Cr or up to 0.3% of Mo or up to 0.15% of V. It is not however outside the scope of the invention to apply the process with steels whose carbon and manganese contents are between 0.4% and 0.6% and which do not contain alloying elements.
- the bead must be made of fine perlite free of proeutectoid ferrite and martensite and possibly containing a certain percentage of bainite and that the hardness gradient in the bead be as low as possible.
- the applicants have proposed another method which consists in lowering the temperature of the rail at the outlet of the hot rolling mill to a value not less than that at which the pearlitic transformation in the bead begins; from this temperature, the continuously moving rail is subjected to rapid cooling until at least 80% of the aotenite-perlite allotropic transformation is carried out in the rail; the rail is then allowed to cool to room temperature.
- This process is based on the unexpected observation that it is not necessary to carry out the complete allotropic transformation of the bead during the intense cooling treatment, to give the rail the desired properties; it is quite possible to obtain these properties even for relatively short treatment times, provided that the different parts of the rail are subjected to cooling, the intensities of which are chosen in an appropriate manner.
- Figures 1, 2 and 3 attached hereto illustrate the reality of the basic principle of this process. Their purpose is to show that the properties (in this case the breaking load) are obtained when a large part of the bead is still in an austenitic state.
- curve A represents the change in temperature of a point located 14 mm below the upper surface of the bead, during the rapid cooling phase (I) and during the cool-down phase on the normal cooler (II).
- FIG. 2 represents, at two different times of such a heat treatment, the state of the austenite / perlite transformation in the bead (ie V in%), from the upper surface to the lower surface (distance d between 0 and 35 mm); curve B gives the situation of this allotropic transformation at the outlet of the rapid cooling device and curve C this situation 25 seconds after the end of this cooling.
- FIG. 1 It can be seen (FIG. 1) that at the depth of 14 mm (this depth corresponds to the taking of the tensile test pieces according to the standards), the cooling rate is 6.8 ° C / s and the temperature at the end of the treatment is 675 ° C.
- Figure 2 shows that at the depth of 14 mm, the transformation hardly started at the end of the treatment; despite this, the properties corresponding to the target values were obtained at this depth.
- FIG. 2 also shows that at the end of the rapid cooling phase, only 32% of the volume of the bead is transformed, this percentage rising to approximately 47%, 25 sec after the end of the treatment.
- FIG. 3 represents both the distribution in the bead of temperatures (° C) and the state of the allotropic transformation (%) at the outlet of the rapid cooling device; on the abscissa are given the distances between the points considered and the upper surface of the bead (mm).
- FIG. 3 shows that, for test No. 20 for example, the perlite formed in the bead at the outlet of the ramp only occupies around 42% of the volume thereof.
- the thermal cycle imposed on the bead in the cooling installation and chosen on the basis of metallurgical considerations is applied in a particular and selective manner to the upper and lower parts of the bead, while the cooling of the core and the pad is adjusted according to the transient deformations of the rail during the treatment.
- the deflection taken by the rail during treatment becomes so large that any mechanical guidance becomes illusory and the application of heat treatment of the rail impossible.
- the upper part of the bead is intensively cooled in order to ensure in this part the allotropic transformation of the austenite into perlite (possibly with bainite in mixture) while that the lower part of the bead is much less cooled to preserve the austenitic state there; during this same rapid cooling phase, the other parts of the rail are also cooled to harmonize the expansions.
- the process for manufacturing rails in which, as soon as it leaves the hot rolling mill, the temperature of the rail is lowered to a value not less than that at which the pearlitic transformation in the bead begins and, from this temperature, the rail is subjected to scrolling continuous rapid cooling and then allowed to cool the rail to room temperature, essentially consists in that for a given temperature of the bead at the entrance of the rapid cooling ramp, the length of the ramp is adjusted, the rail running speed and the average density of the heat fluxes applied to the bead, to the core and to the shoe so that on the one hand the final mechanical properties in the bead are obtained while, at the exit of said ramp , less than 60% of the section of the bead has undergone the allotropic austenite-perlite transformation and that on the other hand the differences in elongation between the bead and the â me and between the bead and the pad are minimized.
- the slow cooling phase which follows the rapid cooling phase, there is a temperature homogenization in the bead; the temperature decreases in the lower part of the bead due to the departure of calories to the cooler adjacent parts of the rail, that is to say both the upper part of the bead and the core.
- the residual austenite also turns into perlite and the entire rail then acquires the desired microstructure.
- the cooling is adjusted in such a way that the martensite is not formed at any point of the bead.
- This particular characteristic of the process is based on the work of the applicants relating to the cooling effect of the various devices which can be used to implement the process, and in particular the case of a nozzle of a determined type, placed at a certain height relative to at the surface cooled and supplied with water at a known rate and temperature.
- FIG. 5 shows the evolution of the surface temperature of the bead in the middle part of the cooling system.
- the surface temperature of the bead rises although, in the arrangement of sprinklers corresponding to this figure, the entire surface of the bead between two consecutive sprinklers is under water.
- the temperature at the start of martensite formation 250 ° C for the steel considered
- ⁇ (350) 1.32
- TMT average transformation temperature
- TMT temperature has been defined as follows: We considered a point in the section of the bead (either in the examples which follow a point located on the plane of symmetry of the rail and 14 mm from the surface of the bead - point of sampling of the tensile test pieces), point whose temperature varies during and after treatment according to law:
- Figure 8 shows an example of the relationship between the breaking load and TMT for a steel at 0.75% C and 0.72% Mn. This fact is of the greatest importance not only for the definition of the thermal cycle, but also for the control of the process.
- the core and the shoe of the rail are cooled by water nozzles similar to those used for the bead.
- the desired average flow is obtained by adjusting the distance between nozzles and the water flow rate per nozzle; these two parameters can be adjusted separately for the core and for the skate.
- the document FR-A-770659 describes a device for tempering a rail by
- a device for manufacturing rail by cooling applied immediately after leaving the rolling mill which comprises a plurality of nozzles arranged along a water cooling ramp as well as guide rollers of the rail in said cooling ramp, is characterized in that said nozzles are arranged in a uniform and uninterrupted manner along said cooling ramp, without interposition of air cooling zones, in that said guide rollers comprise rollers of vertical guide arranged alternately against the shoe and against the upper face of the bead of the rail so as to form alternating groups along the rail, and horizontal guide rollers arranged in pairs between said groups of vertical guide rollers and applied to the lateral faces of the rail bead, and in that the diameter of the horizontal guide rollers is comp reef between 0.5 and 1.5 times the distance between two of said successive rollers.
- FIG. 10 shows an exemplary embodiment of the principles set out above. Some of the guide groups can also be used as means for driving the rail with adjustable speed.
- rollers 1, 1 ', 1' ', ... arranged against the shoe of the rail and 2, 2', 2 '', ... arranged against the upper face of the bead are used for the guidance called " vertical"; the rollers 3, 3 ', 3' ', ... pressed against the short sides of the bead are used for so-called "horizontal" guidance.
- all or part of the guide rollers are supported on the rail with forces whose values are chosen beforehand to tolerate a certain deformation of the rail during the heat treatment.
- it is advantageous to leave the rollers which are supported with such a preset force for example the rollers 2, 2 ', 2' 'in FIG. 10), limited mobility in the guide plane, while the other rollers are said to be "fixed in space” (for example the rollers 1, 1 ', 1' 'in FIG. 10).
- Measuring the position of the rollers pressing on the rail with a preset force makes it possible to determine the deformations of the rail during processing.
- the computer separately adjusts the cooling on the core and the shoe so as to minimize deformation of the rail during treatment.
- This adaptation of the cooling on the core and on the shoe in order to minimize the deformations of the rail can be carried out both in the vertical plane and in the horizontal plane.
- FIG. 10 a further distinction is made between the cooling boxes fitted with sprinklers, spraying respectively the upper face of the bead (box 4), the lower face of the shoe (box 5) and the two faces of the core (boxes 6 and 7 ).
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Physics & Mathematics (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Articles (AREA)
- Escalators And Moving Walkways (AREA)
- Metal Rolling (AREA)
- Machines For Laying And Maintaining Railways (AREA)
- Control Of Vehicles With Linear Motors And Vehicles That Are Magnetically Levitated (AREA)
Abstract
Description
La présente invention porte sur un dispositif pour la fabrication de rails, et notamment de rails à haute résistance, par un refroidissement des rails dès leur sortie de la dernière cage du laminoir, c'est-à-dire dans la chaude de laminage.The present invention relates to a device for manufacturing rails, and in particular high resistance rails, by cooling the rails as soon as they leave the last stand of the rolling mill, that is to say in the hot rolling.
Elle a pour objet l'obtention, de préférence sans addition à l'acier d'éléments d'alliage, de rails présentant, après refroidissement, une résistance à la rupture élevée, une bonne résistance à l'usure, une bonne résistance aux chocs, un allongement au moins égal à 10 % et une bonne soudabilité.Its object is to obtain, preferably without adding alloying elements to the steel, rails having, after cooling, a high breaking strength, good wear resistance, good resistance impact, elongation at least equal to 10% and good weldability.
Par aciers à haute résistance, il faut entendre spécialement des aciers contenant 0,4 % à 0,85 % de C, 0,4 % à 1 % de Mn et 0,1 % à 0,4 % de Si et de préférence 0,6 % à 0,85 % de C et 0,6 % à 0,8 % de Mn; le cas échéant, ces aciers peuvent contenir jusqu'à 1 % de Cr ou jusqu'à 0,3 % de Mo ou jusqu'à 0,15 % de V. Il ne sort toutefois pas du domaine de l'invention d'appliquer le procédé à des aciers dont les teneurs en carbone et en manganèse sont comprises entre 0,4 % et 0,6 % et ne contenant pas d'éléments d'alliage.By high strength steels, it is especially meant steels containing 0.4% to 0.85% of C, 0.4% to 1% of Mn and 0.1% to 0.4% of Si and preferably 0 , 6% to 0.85% C and 0.6% to 0.8% Mn; where appropriate, these steels can contain up to 1% of Cr or up to 0.3% of Mo or up to 0.15% of V. It is not however outside the scope of the invention to apply the process with steels whose carbon and manganese contents are between 0.4% and 0.6% and which do not contain alloying elements.
Il est connu que pour obtenir un rail ayant les propriétés énumérées ci-dessus, il faut que le bourrelet soit constitué de perlite fine exempte de ferrite proeutectoïde et de martensite et contenant éventuellement un certain pourcentage de bainite et que le gradient de dureté dans le bourrelet soit le plus faible possible.It is known that to obtain a rail having the properties listed above, the bead must be made of fine perlite free of proeutectoid ferrite and martensite and possibly containing a certain percentage of bainite and that the hardness gradient in the bead be as low as possible.
A cet égard, il a déjà été proposé, en particulier dans le brevet belge n° 854.834, d'effectuer un traitement thermique du rail, en refroidissant de façon différente le bourrelet et le patin. Selon ce brevet belge, le bourrelet du rail est soumis à un refroidissement accéléré par trempe à l'eau bouillante agitée mécaniquement, alors que le patin est refroidi à l'air ou dans l'eau calme à 100°C.In this regard, it has already been proposed, in particular in Belgian patent n ° 854.834, to carry out a heat treatment of the rail, by cooling the bead and the pad differently. According to this Belgian patent, the rail bead is subjected to accelerated cooling by quenching in mechanically stirred boiling water, while the shoe is cooled in air or in still water at 100 ° C.
Ce procédé connu permet certes de minimiser les déformations permanentes des rails. Toutefois, sa mise en oeuvre à l'échelle industrielle présente des difficultés technologiques.This known method certainly makes it possible to minimize the permanent deformations of the rails. However, its implementation on an industrial scale presents technological difficulties.
En outre, il peut provoquer d'importantes déformations transitoires du rail au cours du traitement, ce qui risque de donner lieu à certaines déformations permanentes.In addition, it can cause significant transient deformations of the rail during treatment, which may give rise to certain permanent deformations.
Pour éliminer les inconvénients mentionnés ci-dessus, les demandeurs ont proposé un autre procédé qui consiste à abaisser la température du rail à la sortie du laminoir à chaud jusqu'à une valeur non inférieure à celle à laquelle débute la transformation perlitique dans le bourrelet; à partir de cette température, le rail en défilement continu est soumis à un refroidissement rapide jusqu'à ce qu'au moins 80 % de la transformation allotropique austénite - perlite soient réalisés dans le rail; on laisse ensuite refroidir le rail jusqu'à la température ambiante.To eliminate the drawbacks mentioned above, the applicants have proposed another method which consists in lowering the temperature of the rail at the outlet of the hot rolling mill to a value not less than that at which the pearlitic transformation in the bead begins; from this temperature, the continuously moving rail is subjected to rapid cooling until at least 80% of the aotenite-perlite allotropic transformation is carried out in the rail; the rail is then allowed to cool to room temperature.
Ce procédé, qui a été décrit dans le brevet luxembourgeois n° 84.417 du 11.10.1982, donne des résultats intéressants, mais nécessite une durée de traitement assez importante.This process, which was described in the Luxembourg patent n ° 84.417 of October 11, 1982, gives interesting results, but requires a fairly long treatment time.
Au cours de leurs travaux ultérieurs, les demandeurs ont alors mis au point un procédé original, comportant une phase de traitement thermique beaucoup plus courte que celle nécessaire dans le procédé antérieur, combinant une méthode de refroidissement du bourrelet qui permet d'obtenir les qualités mécaniques requises, et une méthode de refroidissement du patin et de l'âme assurant la rectitude du rail, pendant et après le traitement thermique.During their subsequent work, the applicants then developed an original process, comprising a much shorter heat treatment phase than that required in the previous process, combining a method of cooling the bead which makes it possible to obtain the mechanical qualities required, and a method of cooling the pad and the core ensuring the straightness of the rail, during and after the heat treatment.
Ce procédé est basé sur la constatation inattendue qu'il n'est pas nécessaire de réaliser la transformation allotropique complète du bourrelet au cours du traitement de refroidissement intense, pour conférer au rail les propriétés voulues; il est tout à fait possible d'obtenir ces propriétés même pour des durées de traitement relativement faibles, pour autant que les différentes parties du rail soient soumises à des refroidissements dont les intensités sont choisies de manière adéquate.This process is based on the unexpected observation that it is not necessary to carry out the complete allotropic transformation of the bead during the intense cooling treatment, to give the rail the desired properties; it is quite possible to obtain these properties even for relatively short treatment times, provided that the different parts of the rail are subjected to cooling, the intensities of which are chosen in an appropriate manner.
Les figures 1, 2 et 3 ci-annexées illustrent la réalité du principe de base de ce procédé elles ont pour objet de montrer que les propriétés (en l'occurrence la charge de rupture) sont obtenues alors qu'une grande partie du bourrelet est encore à l'état austénitique.Figures 1, 2 and 3 attached hereto illustrate the reality of the basic principle of this process. Their purpose is to show that the properties (in this case the breaking load) are obtained when a large part of the bead is still in an austenitic state.
Sur la figure 1, qui est un diagramme température/temps, la courbe A représente l'évolution de la température d'un point situé à 14 mm sous la surface supérieure du bourrelet, au cours de la phase de refroidissement rapide (I) et au cours de la phase de refroidissement calme sur le refroidissoir normal (II).In FIG. 1, which is a temperature / time diagram, curve A represents the change in temperature of a point located 14 mm below the upper surface of the bead, during the rapid cooling phase (I) and during the cool-down phase on the normal cooler (II).
La figure 2 représente, à deux moments différents d'un tel traitement thermique l'état de la transformation austénite/perlite dans le bourrelet (soit V en %), depuis la surface supérieure jusqu'à la surface inférieure (distance d comprise entre 0 et 35 mm); la courbe B donne la situation de cette transformation allotropique à la sortie du dispositif de refroidissement rapide et la courbe C cette situation 25 secondes après la fin de ce refroidissement.FIG. 2 represents, at two different times of such a heat treatment, the state of the austenite / perlite transformation in the bead (ie V in%), from the upper surface to the lower surface (distance d between 0 and 35 mm); curve B gives the situation of this allotropic transformation at the outlet of the rapid cooling device and curve C this situation 25 seconds after the end of this cooling.
Ces figures 1 et 2 illustrent les résultats obtenus en pratiquant selon le principe ci-avant, dans les conditions suivantes :
- type de rail : EB 50 T;
- température d'entrée du rail dans la rampe de refroidissement rapide : 875°C;
- longueur de la rampe : 18 m;
- vitesse de défilement du rail : 0,53 m/sec;
- densité moyenne de flux calorifique à la surface supérieure du bourrelet: 1,15 MW/m²;
- densité moyenne de flux calorifique à la surface inférieure du bourrelet: 0,10 MW/m²;
- composition de l'acier : C: 0,63 %, Mn: 0,65 %.
- rail type: EB 50 T;
- rail inlet temperature in the rapid cooling ramp: 875 ° C;
- length of the ramp: 18 m;
- rail running speed: 0.53 m / sec;
- average density of heat flow at the upper surface of the bead: 1.15 MW / m²;
- average density of heat flow at the lower surface of the bead: 0.10 MW / m²;
- steel composition: C: 0.63%, Mn: 0.65%.
Le bourrelet est assimilé à un plat refroidi de manière intense à sa face supérieure et de manière modérée à sa face inférieure (
On constate (fig. 1) qu'à la profondeur de 14 mm (cette profondeur correspond au prélèvement des éprouvettes de traction suivant les normes), la vitesse de refroidissement est de 6,8°C/s et la température à la fin du traitement est de 675°C. La figure 2 montre qu'à la profondeur de 14 mm, la transformation n'a pratiquement pas commencé à la fin du traitement; malgré cela, on a obtenu, à cette profondeur, les propriétés correspondant aux valeurs visées.It can be seen (FIG. 1) that at the depth of 14 mm (this depth corresponds to the taking of the tensile test pieces according to the standards), the cooling rate is 6.8 ° C / s and the temperature at the end of the treatment is 675 ° C. Figure 2 shows that at the depth of 14 mm, the transformation hardly started at the end of the treatment; despite this, the properties corresponding to the target values were obtained at this depth.
La figure 2 montre également qu'à la fin de la phase de refroidissement rapide, 32 % seulement du volume du bourrelet sont transformés, ce pourcentage passant à environ 47 %, 25 sec après la fin du traitement.FIG. 2 also shows that at the end of the rapid cooling phase, only 32% of the volume of the bead is transformed, this percentage rising to approximately 47%, 25 sec after the end of the treatment.
La figure 3 représente à la fois la répartition dans le bourrelet des températures (°C) et l'état de la transformation allotropique (%) à la sortie du dispositif de refroidissement rapide; en abscisse sont données les distánces entre les points considérés et la surface supérieure du bourrelet (mm).FIG. 3 represents both the distribution in the bead of temperatures (° C) and the state of the allotropic transformation (%) at the outlet of the rapid cooling device; on the abscissa are given the distances between the points considered and the upper surface of the bead (mm).
Les courbes D et E représentent la répartition des températures et les courbes F et G la situation de la transformation allotropique austénite/perlite, dans les conditions pratiques suivantes :
Essai n° 19 (courbes E et G) :
acier 0,77 C - 0,68 Mn - 0,22 Si- température d'entrée du bourrelet : 810°C
- durée du traitement pour la section considérée →51 sec
- débit d'eau total dans la rampe : 34,2 m³/h
- densité de flux calorifique moyenne sur la face supérieure du
bourrelet 0,70 MW/m² - type de rail : ES 50 T
Résultat : charge de rupture à 14 mm sous la face supérieure du bourrelet : 1090 MPa.
Essai n° 20 (courbes D et F) :
acier 0,77 C - 0,68 Mn - 0,22 Si- température d'entrée du bourrelet : 865°C
- durée du traitement pour la section considérée → 49 sec
- débit d'eau total dans la rampe : 40,2 m³/h
- densité de flux calorifique moyenne sur la face supérieure du bourrelet 0,814 MW/m²
- type de rail : EB 50 T
Résultat : charge de rupture à 14 mm sous la face supérieure du bourrelet : 1080 MPa.Curves D and E represent the temperature distribution and curves F and G the situation of the aotenite / perlite allotropic transformation, under the following practical conditions:
Test No. 19 (curves E and G):
- steel 0.77 C - 0.68 Mn - 0.22 Si
- bead inlet temperature: 810 ° C
- duration of treatment for the section considered → 51 sec
- total water flow in the boom: 34.2 m³ / h
- average heat flux density on the upper face of the bead 0.70 MW / m²
- rail type: ES 50 T
Result: breaking load at 14 mm under the upper face of the bead: 1090 MPa.
Test No. 20 (curves D and F):
- steel 0.77 C - 0.68 Mn - 0.22 Si
- bead inlet temperature: 865 ° C
- duration of treatment for the section in question → 49 sec
- total water flow in the boom: 40.2 m³ / h
- average heat flux density on the upper face of the bead 0.814 MW / m²
- rail type: EB 50 T
Result : breaking
Cette figure 3 montre que, pour l'essai n° 20 par exemple, la perlite formée dans le bourrelet à la sortie de la rampe n'occupe que 42 % environ du volume de celui-ci.This FIG. 3 shows that, for test No. 20 for example, the perlite formed in the bead at the outlet of the ramp only occupies around 42% of the volume thereof.
Le fait que les propriétés voulues sont obtenues sans que la transformation dans le bourrelet soit complète est d'une grande importance pratique, car il permet, pour une production horaire donnée, de raccourcir la rampe et, par conséquent, de diminuer les frais d'investissement.The fact that the desired properties are obtained without the transformation in the bead being complete is of great practical importance, since it allows, for a given hourly production, to shorten the ramp and, consequently, to reduce the costs of investment.
Pour mettre en pratique les principes de base de ce procédé le cycle thermique imposé au bourrelet dans l'installation de refroidissement et choisi sur la base de considérations métallurgiques est appliqué de façons particulières et sélectives aux parties supérieures et inférieures du bourrelet, tandis que le refroidissement de l'âme et du patin est réglé en fonction des déformations transitoires du rail pendant le traitement. En effet, l'expérience a montré que, en l'absence d'un tel réglage, la flèche prise par le rail en cours de traitement devient tellement importante que tout guidage mécanique devient illusoire et l'application du traitement thermique du rail impossible.To put the basic principles of this process into practice, the thermal cycle imposed on the bead in the cooling installation and chosen on the basis of metallurgical considerations is applied in a particular and selective manner to the upper and lower parts of the bead, while the cooling of the core and the pad is adjusted according to the transient deformations of the rail during the treatment. Indeed, experience has shown that, in the absence of such an adjustment, the deflection taken by the rail during treatment becomes so large that any mechanical guidance becomes illusory and the application of heat treatment of the rail impossible.
C'est la combinaison des deux caractéristiques qui permet d'obtenir, dans des conditions économiques optimales, un rail répondant aux conditions imposées quant aux propriétés mécaniques et à l'aspect géométrique du produit final.It is the combination of the two characteristics which makes it possible to obtain, under optimal economic conditions, a rail meeting the conditions imposed as regards the mechanical properties and the geometric appearance of the final product.
Suivant une particularité essentielle du procédé, au cours de la phase de refroidissement rapide, on refroidit de façon intense la partie supérieure du bourrelet pour assurer dans cette partie la transformation allotropique de l'austénite en perlite (avec éventuellement de la bainite en mélange) tandis que l'on refroidit beaucoup moins la partie inférieure du bourrelet pour y conserver l'état austénitique; au cours de cette même phase de refroidissement rapide, on refroidit également les autres parties du rail pour harmoniser les dilatations.According to an essential feature of the process, during the rapid cooling phase, the upper part of the bead is intensively cooled in order to ensure in this part the allotropic transformation of the austenite into perlite (possibly with bainite in mixture) while that the lower part of the bead is much less cooled to preserve the austenitic state there; during this same rapid cooling phase, the other parts of the rail are also cooled to harmonize the expansions.
Selon les principes qui viennent d'être énoncés, le procédé pour la fabrication de rails, dans lequel dès la sortie du laminoir à chaud on abaisse la température du rail jusqu'à une valeur non inférieure à celle à laquelle débute la transformation perlitique dans le bourrelet et, à partir de cette température, on soumet le rail en défilement continu à un refroidissement rapide et on laisse ensuite refroidir le rail jusqu'à la température ambiante, consiste essentiellement en ce que pour une température donnée du bourrelet à l'entrée de la rampe de refroidissement rapide, on règle la longueur de la rampe, la vitesse de défilement du rail et la densité moyenne des flux calorifiques appliqués au bourrelet, à l'âme et au patin de manière telle que d'une part les propriétés mécaniques finales dans le bourrelet soient obtenues alors que, à la sortie de la dite rampe, moins de 60 % de la section du bourrelet ait subi la transformation allotropique austénite-perlite et que d'autre part les différences d'allongement entre le bourrelet et l'âme et entre le bourrelet et le patin soient minimisées.According to the principles which have just been stated, the process for manufacturing rails, in which, as soon as it leaves the hot rolling mill, the temperature of the rail is lowered to a value not less than that at which the pearlitic transformation in the bead begins and, from this temperature, the rail is subjected to scrolling continuous rapid cooling and then allowed to cool the rail to room temperature, essentially consists in that for a given temperature of the bead at the entrance of the rapid cooling ramp, the length of the ramp is adjusted, the rail running speed and the average density of the heat fluxes applied to the bead, to the core and to the shoe so that on the one hand the final mechanical properties in the bead are obtained while, at the exit of said ramp , less than 60% of the section of the bead has undergone the allotropic austenite-perlite transformation and that on the other hand the differences in elongation between the bead and the â me and between the bead and the pad are minimized.
Au cours de la phase de refroidissement lent qui suit la phase de refroidissement rapide, il se produit une homogénéisation de température dans le bourrelet; la température diminue dans la partie inférieure du bourrelet en raison du départ des calories vers les parties adjacentes plus froides du rail, c'est-à-dire à la fois la partie supérieure du bourrelet et l'âme. L'austénite résiduelle se transforme également en perlite et l'ensemble du rail acquiert alors la microstructure recherchée.During the slow cooling phase which follows the rapid cooling phase, there is a temperature homogenization in the bead; the temperature decreases in the lower part of the bead due to the departure of calories to the cooler adjacent parts of the rail, that is to say both the upper part of the bead and the core. The residual austenite also turns into perlite and the entire rail then acquires the desired microstructure.
Suivant une mise en oeuvre particulière du procédé, le refroidissement est réglé de manière telle que la martensite ne soit formée en aucun point du bourrelet.According to a particular implementation of the method, the cooling is adjusted in such a way that the martensite is not formed at any point of the bead.
Le choix de la longueur de la rampe de refroidissement rapide et de la vitesse de défilement du rail dans cette rampe revient à fixer la durée du traitement en question; ces valeurs sont liées au choix de la densité moyenne du flux calorifique appliqué à la surface du bourrelet au cours du traitement thermique.The choice of the length of the rapid cooling ramp and the speed of travel of the rail in this ramp amounts to fixing the duration of the treatment in question; these values are linked to the choice of the average density of the heat flux applied to the surface of the bead during the heat treatment.
Dans un procédé de fabrication de rail, déjà connu notamment par la demande de brevet européen n° 0098492, il a été préconisé d'appliquer au rail en défilement une phase de refroidissement intense dans une installation comprenant une série de zones de pulvérisation d'eau séparées par des zones de refroidissement à l'air.In a rail manufacturing process, already known in particular from European patent application No. 0098492, it has been recommended to apply an intense cooling phase to the running rail in an installation comprising a series of water spraying zones. separated by air cooling zones.
Pour mettre en oeuvre ce procédé, il faut donc grouper les gicleurs à eau dans des zones séparées par des sections de refroidissement à l'air. Cette disposition a pour conséquence une ligne de refroidissement de grande longueur dont l'implantation dans un laminoir existant peut présenter certaines difficultés.To implement this method, it is therefore necessary to group the water jets in zones separated by air cooling sections. This arrangement results in a very long cooling line, the installation of which in an existing rolling mill can present certain difficulties.
Contrairement à cette technique connue, il s'est maintenant avéré, de façon surprenante, qu'il n'était pas opportun de disposer les gicleurs à eau par groupes séparés par des sections de refroidissement à l'air; une disposition uniforme et ininterrompue des gicleurs le long de la rampe de refroidissement permet d'obtenir les propriétés désirées tout en évitant la martensite. Cette disposition uniforme des gicleurs à eau est particulièrement avantageuse dans la mesure où elle permet d'utiliser des rampes très courtes.Unlike this known technique, it has now surprisingly been found that it was not advisable to arrange the water jets in groups separated by air cooling sections; a uniform and uninterrupted arrangement of the nozzles along the cooling ramp makes it possible to obtain the desired properties while avoiding martensite. This uniform arrangement of water sprinklers is particularly advantageous in that it allows the use of very short booms.
Cette caractéristique particulière du procédé est basée sur les travaux des demandeurs relatifs à l'effet refroidissant des différents dispositifs utilisables pour mettre en oeuvre le procédé, et notamment le cas d'un gicleur d'un type déterminé, placé à une certaine hauteur par rapport à la surface refroidie et alimenté en eau avec un débit et une température connus.This particular characteristic of the process is based on the work of the applicants relating to the cooling effect of the various devices which can be used to implement the process, and in particular the case of a nozzle of a determined type, placed at a certain height relative to at the surface cooled and supplied with water at a known rate and temperature.
La densité de flux calorifique enlevée à la surface refroidie en un point (x₁, y₁) de celle-ci dépend essentiellement de la température de cette surface : Φ = f (Ts). Pour une valeur donnée de Ts, le flux dépend également des coordonnées (x, y). La figure 4 montre la variation de (Φ) suivant (x) avec y = 0 et pour un gicleur plat pour lequel le plan oyz choisi est le plan de symétrie du gicleur. On constate que le flux diminue très rapidement dès qu'on s'éloigne du plan de symétrie du gicleur et ce, bien que l'eau s'étale sur la surface refroidie sur une assez grande distance du plan de symétrie du gicleur.The density of heat flux removed from the cooled surface at a point (x₁, y₁) thereof depends essentially on the temperature of this surface: Φ = f (T s ). For a given value of T s, the flux also depends on the coordinates (x, y). Figure 4 shows the variation of (Φ) following (x) with y = 0 and for a flat nozzle for which the oyz plane chosen is the plane of symmetry of the nozzle. It can be seen that the flow decreases very rapidly as soon as one moves away from the plane of symmetry of the nozzle, even though the water spreads over the cooled surface over a fairly large distance from the plane of symmetry of the nozzle.
Dans le cas d'un rail dont le bourrelet est refroidi au défilé dans une installation comportant des gicleurs uniformément répartis et distants l'un de l'autre de 175,5 mm, la figure 5 montre l'évolution de la température superficielle du bourrelet dans la partie médiane de l'installation de refroidissement. Dès qu'on s'éloigne du plan de symétrie d'un gicleur, la température superficielle du bourrelet remonte bien que, dans la disposition des gicleurs correspondant à cette figure, toute la surface du bourrelet entre deux gicleurs consécutifs est sous eau. De plus, la température du début de formation de la martensite (250°C pour l'acier considéré) n'est pas atteinte.In the case of a rail, the bead of which is cooled in the runway in an installation comprising uniformly distributed nozzles and spaced 175.5 mm apart from each other, FIG. 5 shows the evolution of the surface temperature of the bead in the middle part of the cooling system. As soon as one moves away from the plane of symmetry of a sprinkler, the surface temperature of the bead rises although, in the arrangement of sprinklers corresponding to this figure, the entire surface of the bead between two consecutive sprinklers is under water. In addition, the temperature at the start of martensite formation (250 ° C for the steel considered) is not reached.
Dans une représentation simplifiée que l'on peut adopter, l'évolution du flux calorifique le long de la rampe a une température de surface donnée est schématisée comme indiqué par la figure 6, où l'on considère néanmoins deux types de refroidissement sur la surface supérieure du bourrelet :
- a) les zones B sous l'influence directe des gicleurs pour lesquelles on utilise des valeurs Φ₁(t) qui constituent la moyenne spatiale dans la zone d'impact et pour chaque température;
- b) les zones A entre gicleurs; ces zones sont sous eau, mais les mesures ont montré que le flux calorifique y est nettement plus faible que sous les gicleurs du moins dans le domaine de la caléfaction. De plus, la transition caléfaction-ébullition nucléée y a lieu de manière relativement brutale.
- a) the zones B under the direct influence of the nozzles for which values Φ₁ (t) are used which constitute the spatial average in the impact zone and for each temperature;
- b) zones A between nozzles; these areas are under water, but the measurements have shown that the heat flow is much lower there than under the sprinklers at least in the area of calefaction. In addition, the nucleation-boiling transition nucleated there occurs relatively abruptly.
Dans la simplification ci-dessus, on a négligé la variation du flux suivant y, l'expérience ayant montré qu'elle est faible.In the above simplification, the variation of the flux following y has been neglected, experience having shown that it is weak.
Dans ce qui suit, on utilisera la notion de densité moyenne de flux calorifique (
Le flux moyen (
où A est la distance entre deux gicleurs consécutifs.The average flow (
where A is the distance between two consecutive nozzles.
En principe,
Si l'on adopte la simplification de la figure 6, on a :
où Φ₁ est la valeur du flux moyen dans la zone sous influence directe des gicleurs, Φ₂ est la valeur du flux moyen dans la zone noyée, mais non arrosée entre gicleurs, A la distance entre gicleurs et B la largeur de la zone arrosée par un gicleur; les valeurs de ces paramètres sont connues dès lors qu'il s'agit d'une installation déterminée.If we adopt the simplification of Figure 6, we have:
where Φ₁ is the value of the average flow in the area under direct influence of the sprinklers, Φ₂ is the value of the average flow in the flooded area, but not watered between sprinklers, At the distance between sprinklers and B the width of the area watered by a sprinkler; the values of these parameters are known when it is a specific installation.
La valeur du flux moyen étant déterminée grâce à la relation (α), pour appliquer le procédé, il n'y a dès lors plus qu'à rechercher la valeur de la durée (τ) de la phase du refroidissement rapide, en tenant compte bien entendu de la composition de l'acier, des propriétés visées pour le rail et des caractéristiques générales de l'installation dont on dispose.The value of the average flux being determined thanks to the relation (α), to apply the method, there is therefore only to find the value of the duration (τ) of the rapid cooling phase, taking into account of course the composition of the steel, the properties targeted for the rail and the general characteristics of the installation available.
On peut avantageusement utiliser la notion de "température moyenne de transformation" (en abrégé TMT).It is advantageous to use the concept of "average transformation temperature" (abbreviated as TMT).
Au cours de leurs travaux, les demandeurs ont en effet mis en évidence le fait que, si les paramètres tels que la vitesse moyenne de refroidissement ou la température moyenne en fin de refroidissement contrôlé ont une influence sur les propriétés mécaniques du bourrelet, le paramètre contrôlant directement et de manière univoque les propriétés est cette "température moyenne de transformation".During their work, the applicants have in fact highlighted the fact that, if parameters such as the average cooling speed or the average temperature at the end of controlled cooling have an influence on the mechanical properties of the bead, the parameter controlling directly and unequivocally the properties is this "average transformation temperature".
A cet effet, on a défini de la façon suivante la dite température TMT :
On a considéré un point de la section du bourrelet (soit dans les exemples qui suivent un point situé sur le plan de symétrie du rail et à 14 mm de la surface du bourrelet- point de prélèvement des éprouvettes de traction), point dont la température varie pendant et après le traitement suivant la loi :
We considered a point in the section of the bead (either in the examples which follow a point located on the plane of symmetry of the rail and 14 mm from the surface of the bead - point of sampling of the tensile test pieces), point whose temperature varies during and after treatment according to law:
Par ailleurs, la cinétique de la transformation allotropique en ce point est décrite par :
où z représente le pourcentage en volume de l'austénite transformée.Furthermore, the kinetics of the allotropic transformation at this point is described by:
where z represents the percentage by volume of the transformed austenite.
En combinant ces deux cinétiques (1) et (2), on obtient: T = f₃(z), d'où
Sur la figure 7, les relations (1) et (2) sont représentées à la partie supérieure (température et z en fonction du temps) au cours des deux phases de refroidissement rapide (I) et de refroidissement à l'air (II), tandis que la relation (3) est représentée à la partie inférieure (diagramme z/T°).In FIG. 7, the relationships (1) and (2) are shown at the top (temperature and z as a function of time) during the two phases of rapid cooling (I) and air cooling (II) , while the relation (3) is represented in the lower part (z / T ° diagram).
Se basant sur le fait remarquable qu'il existe une relation étroite et univoque entre les propriétés mécaniques et la température dite TMT, les demandeurs préconisent de déterminer les valeurs de Φ et de τ en utilisant comme seul paramètre cette température en question qui, pour un acier de composition donnée, serait alors la seule variable dont dépendent les propriétés mécaniques.Based on the remarkable fact that there is a close and unequivocal relationship between the mechanical properties and the so-called TMT temperature, the applicants recommend determining the values of Φ and τ using this temperature in question as the only parameter, which for a steel of given composition, would then be the only variable on which the mechanical properties depend.
La figure 8 montre un exemple de la relation entre la charge de rupture et TMT pour un acier à 0,75 % C et 0,72 % Mn. Ce fait est de la plus haute importance non seulement pour la définition du cycle thermique, mais également pour le contrôle du procédé.Figure 8 shows an example of the relationship between the breaking load and TMT for a steel at 0.75% C and 0.72% Mn. This fact is of the greatest importance not only for the definition of the thermal cycle, but also for the control of the process.
Pour un acier donné, la relation "charge de rupture - TMT" permet de déterminer (TMT) min et (TMT) max à partir des valeurs respectivement maximales et minimales des charges de rupture visées dans le bourrelet, par exemple dans le cas de la figure 8, des valeurs (TMT) min = 615°C et (TMT) max = 645°C si l'on vise une charge de rupture comprise entre 1080 et 1200 MPa (acier à 0,75 % C et 0,72 % Mn).For a given steel, the relation "breaking load - TMT" makes it possible to determine (TMT) min and (TMT) max from the maximum and minimum values respectively of the breaking loads targeted in the bead, for example in the case of the Figure 8, values (TMT) min = 615 ° C and (TMT) max = 645 ° C if we aim at a breaking load between 1080 and 1200 MPa (steel at 0.75% C and 0.72% Mn).
Dans un problème particulier, il est possible de déterminer un domaine de variation des deux paramètres
Les données du problème sont les suivantes :
- la composition de l'acier,
- la fourchette des propriétés mécaniques visées et dès lors les valeurs maximale et minimale de la température moyenne de transformation,
- la température d'entrée maximale du bourrelet dans la rampe fonction de la température de fin de laminage et donc de l'installation,
- la température d'entrée minimale du bourrelet dans la rampe; cette température doit être supérieure à la température de début de transformation afin d'éviter la formation de structures douces en surface du bourrelet.
Il existe en outre deux contraintes :
- l'absence de formation de martensite dans ce bourrelet,
- la transformation de 60 % max d'austénite dans la section du bourrelet à la sortie de la rampe.
The details of the problem are as follows:
- the composition of the steel,
- the range of targeted mechanical properties and therefore the maximum and minimum values of the average transformation temperature,
- the maximum entry temperature of the bead in the ramp as a function of the temperature of the end of rolling and therefore of the installation,
- the minimum entry temperature of the bead into the ramp; this temperature must be higher than the temperature at the start of transformation in order to avoid the formation of soft structures on the surface of the bead.
There are also two constraints:
- the absence of martensite formation in this bead,
- the transformation of 60% max of austenite in the section of the bead at the exit of the ramp.
On a donné à la figure 9 une représentation schématique du domaine de variation de
- La courbe A correspond à une température d'entrée maximum et une température moyenne de transformation minimum.
- La courbe B correspond à une température d'entrée minimum et uns température moyenne de transformation maximum.
- La courbe C correspond au flux maximum pour lequel il ne se forme pas de martensite dans la section du bourrelet.
- La courbe D correspond au temps de trempe pour lequel le pourcentage d'austénite transformée à la sortie de la rampe est de 60 %.
- Curve A corresponds to a maximum inlet temperature and a minimum average transformation temperature.
- Curve B corresponds to a minimum inlet temperature and a maximum average transformation temperature.
- Curve C corresponds to the maximum flux for which no martensite is formed in the section of the bead.
- Curve D corresponds to the quenching time for which the percentage of austenite transformed at the outlet of the ramp is 60%.
Un tel diagramme doit être créé dans chaque cas particulier. Il peut être calculé au moyen de modèle mathématique, par exemple le modèle simple suivant :
où τ = durée de traitement (s)
-
Φ = - flux moyen (MW/m²)
- TO=
- température initiale du bourrelet
- a, b, c, d =
- coefficients dépendant de la composition et du type du rail, ainsi que de la valeur visée pour TMT.
where τ = treatment duration (s)
-
Φ = - average flow (MW / m²)
- T O =
- initial bead temperature
- a, b, c, d =
- coefficients depending on the composition and type of rail, as well as the target value for TMT.
Par exemple, pour TMT = 645°C, un rail EB 50 T et un acier à 0,63 % C - 0,65 % Mn, on a les valeurs suivantes :
- a =
- - 0,095 m²s °C⁻¹ MW⁻¹
- b =
- 0,185 s °
C⁻ ¹ - c =
- 52,6 m²s MW⁻¹
- d =
- - 100 s
et donc finalement on obtient la durée τ du traitement.For example, for TMT = 645 ° C, an EB 50 T rail and a steel at 0.63% C - 0.65% Mn, we have the following values:
- a =
- - 0.095 m²s ° C⁻¹ MW⁻¹
- b =
- 0.185 s °
C⁻ ¹ - c =
- 52.6 m²s MW⁻¹
- d =
- - 100 s
and therefore finally we obtain the duration τ of the treatment.
Dans une mise en oeuvre avantageuse du procédé l'âme et le patin du rail sont refroidis par des gicleurs à eau analogues à ceux utilisés pour le bourrelet. Le flux moyen désiré est obtenu par un réglage de la distance entre gicleurs et du débit d'eau par gicleur; ces deux paramètres sont ajustables séparément pour l'âme et pour le patin.In an advantageous implementation of the process, the core and the shoe of the rail are cooled by water nozzles similar to those used for the bead. The desired average flow is obtained by adjusting the distance between nozzles and the water flow rate per nozzle; these two parameters can be adjusted separately for the core and for the skate.
Les essais industriels ont toutefois montré que malgré tous les soins apportés au réglage du refroidissement des trois parties du rail (bourrelet, patin, âme), il était impossible d'éviter complètement les déformations transitoires de celui-ci dues surtout à l'apparition et au développement différentiel de la transformation allotropique dans les trois parties du rail.Industrial tests have, however, shown that despite all the care taken in regulating the cooling of the three parts of the rail (bead, pad, core), it was impossible to completely avoid the transient deformations of the latter due mainly to the appearance and to the differential development of the allotropic transformation in the three parts of the rail.
L'existence de cette tendance aux déformations transitoires rend le guidage du rail, pendant le traitement, indispensable, mais aussi difficile.The existence of this tendency to transient deformations makes guiding the rail, during treatment, essential, but also difficult.
Le document FR-A-770659 décrit un dispositif de trempe d'un rail parThe document FR-A-770659 describes a device for tempering a rail by
immersion, avec des galets de guidage réglables en fonction du type de rail mais fixes jour chaque type de rail. Ces galets appliquent un cintrage mécanique de correction du rail. Au cours de leurs travaux, les demandeurs ont développé un mécanisme de guidage efficace, dont les caractéristiques essentielles sont les suivantes:
- le guidage du rail dans le plan vertical n'est pas assuré par des paires de galets dont les axes de rotation sont situés dans un plan perpendiculaire au déplacement du rail, mais les galets doivent être décalés et de préférence être groupés par trois;
- le diamètre des galets de guidage dans le plan horizontal doit être compris entre 0,5
1,5 fois la distance entre deux galets successifs;et - le guidage dans le plan horizontal doit se faire par appui sur les faces latérales du bourrelet par des galets à axe vertical situés entre les groupes de galets de guidage vertical.
- the guide of the rail in the vertical plane is not ensured by pairs of rollers whose axes of rotation are located in a plane perpendicular to the movement of the rail, but the rollers must be offset and preferably be grouped by three;
- the diameter of the guide rollers in the horizontal plane must be between 0.5 and 1.5 times the distance between two successive rollers;
- guiding in the horizontal plane must be done by pressing on the lateral faces of the bead by rollers with vertical axis situated between the groups of vertical guide rollers.
Conformément à la présente invention, un dispositif pour la fabrication de rail par un refroidissement appliqué immédiatement après la sortie du laminoir, qui comprend une pluralité de gicleurs disposés le long d'une rampe de refroidissement à l'eau ainsi que des galets de guidage du rail dans ladite rampe de refroidissement, est caractérisé en ce que lesdits gicleurs sont disposés de façon uniforme et ininterrompue le long de ladite rampe de refroidissement, sans interposition de zones de refroidissement à l'air, en ce que lesdits galets de guidage comprennent des galets de guidage vertical disposés en alternance contre le patin et contre la face supérieure du bourrelet du rail de façon à former des groupes alternés le long du rail, et des galets de guidage horizontal disposés par paires entre lesdits groupes de galets de guidage vertical et appliqués sur les faces latérales du bourrelet du rail, et en ce que le diamètre des galets de guidage horizontal est compris entre 0,5 et 1,5 fois la distance entre deux desdits galets successifs.According to the present invention, a device for manufacturing rail by cooling applied immediately after leaving the rolling mill, which comprises a plurality of nozzles arranged along a water cooling ramp as well as guide rollers of the rail in said cooling ramp, is characterized in that said nozzles are arranged in a uniform and uninterrupted manner along said cooling ramp, without interposition of air cooling zones, in that said guide rollers comprise rollers of vertical guide arranged alternately against the shoe and against the upper face of the bead of the rail so as to form alternating groups along the rail, and horizontal guide rollers arranged in pairs between said groups of vertical guide rollers and applied to the lateral faces of the rail bead, and in that the diameter of the horizontal guide rollers is comp reef between 0.5 and 1.5 times the distance between two of said successive rollers.
Des modes préférés de réalisation du dispositif selon l'invention sont énumérés dans les revendications 2 à 7.Preferred embodiments of the device according to the invention are listed in
La figure 10 montre un exemple de réalisation des principes énoncés ci-dessus. Certains des groupes de guidage peuvent être également utilisés comme moyens d'entraînement du rail à vitesse réglable.FIG. 10 shows an exemplary embodiment of the principles set out above. Some of the guide groups can also be used as means for driving the rail with adjustable speed.
Sur cette figure 10, les galets 1, 1', 1'', ... disposés contre le patin du rail et 2, 2', 2'', ... disposés contre la face supérieure du bourrelet servent au guidage dit "vertical"; les galets 3, 3', 3'', ... appuyés contre les petits côtés du bourrelet servent au guidage dit "horizontal".In this figure 10, the
Dans une réalisation particulière du dispositif de l'invention, tout ou partie des galets de guidage sont appuyés sur le rail avec des forces dont les valeurs sont choisies au préalable pour tolérer une certaine déformation du rail au cours du traitement thermique. Dans une telle réalisation du dispositif, il est avantageux de laisser aux galets qui sont appuyés avec une telle force préétablie (par exemple les galets 2, 2' , 2'' sur la figure 10), une mobilité limitée dans le plan de guidage, tandis que les autres galets sont dits "fixes dans l'espace" (par exemple les galets 1, 1', 1'' sur la figure 10).In a particular embodiment of the device of the invention, all or part of the guide rollers are supported on the rail with forces whose values are chosen beforehand to tolerate a certain deformation of the rail during the heat treatment. In such an embodiment of the device, it is advantageous to leave the rollers which are supported with such a preset force (for example the
La mesure de la position des galets qui appuient sur le rail avec une force préétablie permet de déterminer les déformations du rail au cours du traitement. A l'aide du modèle du procédé, le calculateur ajuste séparément le refroidissement sur l'âme et le patin de manière à minimiser les déformations du rail au cours du traitement.Measuring the position of the rollers pressing on the rail with a preset force makes it possible to determine the deformations of the rail during processing. Using the process model, the computer separately adjusts the cooling on the core and the shoe so as to minimize deformation of the rail during treatment.
Cette adaptation du refroidissement sur l'âme et sur le patin en vue de minimiser les déformations du rail peut s'effectuer aussi bien dans le plan vertical que dans le plan horizontal.This adaptation of the cooling on the core and on the shoe in order to minimize the deformations of the rail can be carried out both in the vertical plane and in the horizontal plane.
Sur la figure 10, on distingue encore les boîtes de refroidissement munies de gicleurs, arrosant respectivement la face supérieure du bourrelet (boîte 4), la face inférieure du patin (boîte 5) et les deux faces de l'âme (boîtes 6 et 7).In FIG. 10, a further distinction is made between the cooling boxes fitted with sprinklers, spraying respectively the upper face of the bead (box 4), the lower face of the shoe (box 5) and the two faces of the core (
Claims (7)
- Device for manufacturing a rail by means of a cooling applied immediately after the exit of the rolling mill, which comprises a plurality of jets disposed along a ramp for cooling with water as well as rollers for guiding the rail in the said cooling ramp characterised in that the said jets are disposed uniformally and continuously along the said cooling ramp without interposition of zones for cooling with air, in that the said guide rollers comprise vertical guide rollers (1, 1', 1''; 2, 2', 2'') disposed alternately against the flange and against the upper face of the head of the rail so as to form alternate groups along the rail, and horizontal guide rollers (3, 3') disposed in pairs between the said groups of vertical guide rollers and applied on the lateral faces of the head of the rail, and in that the diameter of the horizontal guide rollers (3', 3'') is between 0.5 and 1.5 times the distance between two of the said successive rollers (3', 3'').
- Device according to Claim 1, characterised in that the said vertical guide rollers (1, 1'; 2, 2') are grouped in threes, each of the said groups of three rollers comprising two rollers (2, 2'; 1', 1'') disposed on the same side of the rail, that is to say either above or below the rail, and a third roller (1; 2'') located on the other side of the rail, that is to say either below or above the rail, longitudinally between the two other rollers of the said group.
- Device according to anyone of Claims 1 and 2, characterised in that at least some of the said guide rollers bear on the rail with preset forces and in that the said rollers which bear with the said preset forces have a limited mobility in the guide plane.
- Device according to anyone of Claims 1 to 3, characterised in that the said jets are mounted in cooling boxes (4, 5, 6, 7), in that the said cooling boxes are disposed around the rail, and in that areas of overlap of the said cooling boxes are provided in the longitudinal direction.
- Device according to anyone of Claims 1 to 4, characterised in that each of the said guide rollers (1, 1'; 2, 2'; 3, 3') is disposed between successive cooling boxes (4; 5; 6; 7) corresponding to a face of the rail and opposite at least one of the said successive cooling boxes corresponding to at least another of the faces of the rail.
- Device according to anyone of Claims 1 to 5, characterised in that it comprises means for measuring the position of the guide rollers (1, 2, 3) which bear on the rail with a preset force.
- Device according to anyone of Claims 1 to 6, characterised in that it comprises means for separately adjusting the cooling on the flange and on the web of the said rail.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT85870064T ATE66252T1 (en) | 1984-05-09 | 1985-05-08 | DEVICE FOR MAKING RAILS. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
BE6047966 | 1984-05-09 | ||
BE6/47966A BE899617A (en) | 1984-05-09 | 1984-05-09 | IMPROVED METHOD AND DEVICE FOR MANUFACTURING RAILS. |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0161236A2 EP0161236A2 (en) | 1985-11-13 |
EP0161236A3 EP0161236A3 (en) | 1987-05-13 |
EP0161236B1 true EP0161236B1 (en) | 1991-08-14 |
Family
ID=3874946
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP85870064A Expired - Lifetime EP0161236B1 (en) | 1984-05-09 | 1985-05-08 | Apparatus for manufacturing rails |
Country Status (8)
Country | Link |
---|---|
US (1) | US4668308A (en) |
EP (1) | EP0161236B1 (en) |
AT (1) | ATE66252T1 (en) |
AU (1) | AU578689B2 (en) |
BE (1) | BE899617A (en) |
CA (1) | CA1262670A (en) |
DE (1) | DE3583768D1 (en) |
LU (1) | LU85885A1 (en) |
Families Citing this family (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
BE899617A (en) * | 1984-05-09 | 1984-11-09 | Centre Rech Metallurgique | IMPROVED METHOD AND DEVICE FOR MANUFACTURING RAILS. |
DE3579681D1 (en) * | 1984-12-24 | 1990-10-18 | Nippon Steel Corp | METHOD AND DEVICE FOR TREATING THE RAILS. |
AT384624B (en) * | 1986-05-22 | 1987-12-10 | Voest Alpine Ag | DEVICE FOR CONTROLLED HEAT TREATMENT OF SOFT PARTS |
LU86510A1 (en) * | 1986-07-10 | 1988-02-02 | Centre Rech Metallurgique | METHOD AND DEVICE FOR MANUFACTURING A HIGH RESISTANCE RAIL |
US4886558A (en) * | 1987-05-28 | 1989-12-12 | Nkk Corporation | Method for heat-treating steel rail head |
US4895605A (en) * | 1988-08-19 | 1990-01-23 | Algoma Steel Corporation | Method for the manufacture of hardened railroad rails |
US5018666A (en) * | 1989-12-01 | 1991-05-28 | Cf&I Steel Corporation | Unitary one quarter mile long railroad rail free of weld seams |
DE4200545A1 (en) * | 1992-01-11 | 1993-07-15 | Butzbacher Weichenbau Gmbh | TRACK PARTS AND METHOD FOR THE PRODUCTION THEREOF |
BE1008648A6 (en) * | 1994-09-29 | 1996-07-02 | Centre Rech Metallurgique | Manufacturing process for rail. |
EP0807692A1 (en) * | 1996-05-15 | 1997-11-19 | Sms Schloemann-Siemag Aktiengesellschaft | Method of cooling structural steel beams |
ITMI20072244A1 (en) * | 2007-11-28 | 2009-05-29 | Danieli Off Mecc | DEVICE FOR HEAT TREATMENT OF RAILS AND ITS PROCESS |
EP2674504A1 (en) * | 2012-06-11 | 2013-12-18 | Siemens S.p.A. | Method and system for thermal treatments of rails |
Family Cites Families (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB422954A (en) * | 1933-07-11 | 1935-01-11 | Illinois Steel Company | Heat treatment of steel rails |
FR770659A (en) * | 1934-03-26 | 1934-09-18 | Laminoirs Hauts Fourneaux Forg | Improved process for tempering vineyard rails and grooved rails to avoid fragility |
FR852749A (en) * | 1938-04-12 | 1940-03-01 | Method and apparatus for heat treatment of steel rails | |
FR2109121A5 (en) * | 1970-10-02 | 1972-05-26 | Wendel Sidelor | |
BE826456A (en) * | 1975-03-07 | 1975-06-30 | PROCESS FOR THE TREATMENT OF RAILS | |
JPS57198216A (en) * | 1981-05-27 | 1982-12-04 | Nippon Kokan Kk <Nkk> | Manufacture of high-strength rail |
CA1193176A (en) * | 1982-07-06 | 1985-09-10 | Robert J. Ackert | Method for the production of improved railway rails by accelerated colling in line with the production rolling mill |
LU84417A1 (en) * | 1982-10-11 | 1984-05-10 | Centre Rech Metallurgique | IMPROVED PROCESS FOR THE MANUFACTURE OF RAILS AND RAILS OBTAINED BY THIS PROCESS |
BE899617A (en) * | 1984-05-09 | 1984-11-09 | Centre Rech Metallurgique | IMPROVED METHOD AND DEVICE FOR MANUFACTURING RAILS. |
-
1984
- 1984-05-09 BE BE6/47966A patent/BE899617A/en not_active IP Right Cessation
-
1985
- 1985-05-07 LU LU85885A patent/LU85885A1/en unknown
- 1985-05-08 EP EP85870064A patent/EP0161236B1/en not_active Expired - Lifetime
- 1985-05-08 US US06/731,717 patent/US4668308A/en not_active Expired - Lifetime
- 1985-05-08 DE DE8585870064T patent/DE3583768D1/en not_active Expired - Lifetime
- 1985-05-08 AT AT85870064T patent/ATE66252T1/en active
- 1985-05-08 CA CA000481056A patent/CA1262670A/en not_active Expired
- 1985-05-09 AU AU42240/85A patent/AU578689B2/en not_active Ceased
Non-Patent Citations (3)
Title |
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Cinétique de la transformation allotropique des aciers. Application au refroidissement du fil machine en acier dur. Thèse de Doctorat en Sciences Appliquées- Université de Liège, Faculté des Sciences Appliquées, Publication no. 80, 1979, pages 23-63 (N. LAMBERT) * |
Laboratory Study of the S.ED.C. Cycle for Mild Steels. 1st part : Ferritic Grain Growth - Metallurgical Reports CRM, no. 55, November 1979, pages 25-32 (M. ECONOMOPOULOS, N. LAMBERT) * |
The EDC process : metallurgical background and industrial application - Wire Journal, 1981, mars, pages 90-95 (M. ECONOMOPOULOS, N. LAMBERT) * |
Also Published As
Publication number | Publication date |
---|---|
LU85885A1 (en) | 1986-01-14 |
BE899617A (en) | 1984-11-09 |
AU578689B2 (en) | 1988-11-03 |
EP0161236A2 (en) | 1985-11-13 |
ATE66252T1 (en) | 1991-08-15 |
CA1262670A (en) | 1989-11-07 |
US4668308A (en) | 1987-05-26 |
AU4224085A (en) | 1985-11-14 |
EP0161236A3 (en) | 1987-05-13 |
DE3583768D1 (en) | 1991-09-19 |
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