EP1512469A1 - Method and device for lubricating rolling rolls - Google Patents

Abstract

An installation for the in-line lubrication of rolls for the hot rolling of steel strip by pulverization or atomization of a lubricant or mixture of lubricants on a target, comprises an essentially closed case (1) provided with: (a) a mechanism (10) for forming a cloud of lubricating droplets with a size of less than 2 mm, preferably less than 700 Microm and more preferably less than 200 Microm; (b) a diaphragm (3) with an adjustable opening placed on a leading surface of the case; and (c) a device for the recuperation of excess lubricant (4) on the part of the diaphragm inside the case and on the inner walls of the case. An independent claim is also included for lubricating rolling mill rolls using this installation.

Description

Object of the invention

The present invention relates to a new cylinder lubrication system of a rolling line, preferably a rolling line to hot.

The invention also relates to the method implemented on the installation.

Technological background and state of the art

During hot rolling of strips of steel, in each cage of the finishing train, the band of steel is subject to a thermomechanical path well determined (reduction, temperature) which is influenced by the friction between the work rolls and the band in the gap between the rollers. It is well known that this thermomechanical path has a major influence on the tape quality (surface appearance and properties Metallurgical).

It is therefore essential to be able to control and control the friction in the interstice of the rollers (or cylinders). A coefficient of friction too high leads to excessive energy consumption, rapid degradation of the rolls as well as defects in surface on the band. Conversely, a coefficient of low friction causes slip problems and guide the tape as well as entry problems of it in the cage.

Friction is mainly influenced by the evolution of the surface of the roll and by the film of scale formed on the surface of the rollers and the strip. Thus, the coefficient of friction changes during a rolling campaign, a deterioration of the surface of the rolls (banding, peeling) accompanied by a increase in this coefficient of friction. Friction is also influenced by the nature of the rolls, the new HSS rollers being characterized by higher coefficients of friction.

The control of the coefficient of friction is ensured by the lubrication process.

Currently cylinder lubrication rolling mill is produced by spraying an emulsion, which is a suspension of oil droplets in the water, without mixing of oil and water, with a concentration in oil typically ranging between 0.3 and 2%. he can either a stable emulsion or an emulsion unstable prepared online.

Generally, the emulsion is applied directly on the work rolls by means of a spray device located after the squeegees in the purpose of applying the oil on a dry surface. This mode application ensures a better distribution of the oil and therefore contributes to the reduction of the oil consumption.

The interest of a good lubrication of work rolls is not just limited to the problem roll performance (surface degradation) but is also related to the forces and rolling torques to apply and hence to the power consumption necessary. The need for lubrication performance is further enhanced with the use of HSS type rollers characterized by a coefficient of higher friction than traditional rollers.

Under normal rolling conditions, without lubrication, the friction coefficients of Coulomb amount to 0.2 - 0.25, at least in the first cages. With lubrication, we calculated, from the observed rolling pressure loss, that the coefficients friction are of the order of 0.15 - 0.18.

In addition to minimizing the degradation of work rolls, lubrication leads to a improvement of the metallurgical properties of the product, especially when the finishing lamination takes place at low temperature in the ferritic field. The level of required quality therefore requires very little lubrication performance. In fact, the level of coefficient of friction that should be achieved to obtain optimization of the mechanical properties of the product should to be close to 0.10, which is well below current performance.

In lubrication conditions, the coefficient of friction depends on many factors such that the application technology used, the quantity of oil, the nature of the oil, the speed of flow and the concentration of the oil emulsion, the temperature of the surface of the tape, the nature and condition of the rollers (roughness, degradation, scale, etc.), the speed of rolling, reduction, etc. Thus, the effectiveness of lubrication can be very different from a train to the other and from one cage to another in the same train.

In the laboratory, it has been determined that the lubrication efficiency is a function of the rolling temperature, the nature of the lubricant (mineral, ester-based, etc.) and the amount thereof. Satisfactory results are obtained by spraying oil in surface densities ("plate-out") of 0.1 to 1 g / m ² , which is significantly more than is required simply to control the degradation of the rollers .

Conventionally, the system of spraying the oil emulsion is either a venturi, the aspiration of the oil being carried out by the depression created by moving water in the main tube, a static mixer ("static tube mixer") where one oil injection into a tube area where the shear (velocity gradient) is increased thanks to the presence of "obstacles". The venturi or the "static tube mixer "is combined with a series of injectors whose number is selected based on the bandwidth at lubricate (3 to 7 injectors for a band up to 2 meters wide).

EP-A-1,193,004 discloses a method of lubrication system for cold rolling comprising steps of: supplying a rolling oil emulsion using a first device for supplying the oil in the form of an emulsion supplied to a cylinder and a steel strip according to a recirculation mode and a second device for supplying the emulsion only on the front and back surfaces of the steel strip. In the second device, the rolling oil is added to an emulsifier of the same type and concentration as those used for the first device, with a control of average size of particles so that they are more large than in the first device. The emulsion produced by the second device not adhered to the band is recovered at the same time as the emulsion produced by the first device.

US-A-3,933,660 proposes an oil lubricating reducer for hot rolling of copper and its alloys comprising 1000 parts by weight of water, 6 to 200 parts by weight of anionic surface activator of type carboxylic acid, sulfate or phosphate and 0.8 to 200 parts by weight of at least one compound containing a hydroxyl group of alcohol type, alkylene glycol or ether glycol. Rolling oil provides copper and its alloys a lubrication, an ability to remove a oxide film and an ability to prevent the formation of a oxide film by spraying between the cylinder of rolling and the hot rolling strip.

JP-A-55 151 093 describes a process lubrication in cold rolling of a covered strip by a polar organic compound which is sprayed with a emulsion of oil and a composition comprising a compound polar organic such as stearic acid. The emulsion excess oil is removed by spinning after formation of an adsorbed oil layer on the surface of the bandaged.

• l'interaction huile-eau, qui est fonction du type d'huile et de la "qualité" de l'eau, détermine le temps d'adhésion de l'huile sur le cylindre, ainsi que la quantité adhérente. L'efficacité des dispositifs utilisés n'est donc pas aisément prévisible ;
• les performances des émulsions instables utilisées sont hautement corrélées à la capacité de maintenir une bonne dispersion de l'huile dans l'eau, ou en d'autres termes à la valeur et à la stabilité au cours du temps du taux de cisaillement obtenu, lequel est corrélé au gradient de vitesse, qui est fonction à la fois de la longueur et du diamètre du tube utilisé ainsi que du débit de l'émulsion. Il est en fait difficile de maintenir cette stabilité entre le "static tube mixer" et les différents injecteurs ; en d'autres termes, il est difficile d'assurer la contrôlabilité du coefficient de frottement obtenu ;
• la mise en contact de l'huile et de l'eau conduit généralement à des réactions formant une phase polymérique dure et collante, bouchant les tuyaux d'admission et les injecteurs.

The main disadvantages inherent to these spraying devices of an oil emulsion, used on an industrial scale, are the following:

• the oil-water interaction, which is a function of the type of oil and the "quality" of the water, determines the time of adhesion of the oil to the cylinder, as well as the adhering amount. The effectiveness of the devices used is therefore not easily predictable;
• the performance of the unstable emulsions used is highly correlated with the ability to maintain a good dispersion of the oil in the water, or in other words the value and stability over time of the shear rate obtained, which is correlated with the speed gradient, which is a function of both the length and the diameter of the tube used as well as the flow rate of the emulsion. It is actually difficult to maintain this stability between the "static tube mixer" and the different injectors; in other words, it is difficult to ensure the controllability of the coefficient of friction obtained;
• the contacting of the oil with the water generally leads to reactions forming a hard and sticky polymeric phase, blocking the intake pipes and the injectors.

Goals of the invention

The present invention aims to provide a solution that overcomes the disadvantages of the state of technique such as the inability to control and control the concentration and stability of the emulsion oil-water, clogging of the intake pipes of the emulsion by formation of solid organic residues, the influence of the specific flow rate, etc.

The object of the invention is in particular to propose a new process of lubricating the cylinders of rolling to maintain constant or in any case under control the friction on an industrial scale.

The invention also aims to increase the effectiveness of the attachment of the lubricating oil on the cylinders.

The invention also aims to increase the homogenisation of the distribution of the oil on the cylinders.

Main characteristic elements of the invention

• d'un moyen de formation d'un nuage de gouttelettes de lubrifiant de taille inférieure à 2 mm, de préférence inférieure à 700 µm, et de préférence encore inférieure à 200 µm ;
• d'un diaphragme à ouverture réglable associé audit moyen et placé sur une face avant du caisson et
• d'un dispositif de récupération de lubrifiant excédentaire sur la partie du diaphragme interne au caisson et sur les parois internes du caisson.

A first object of the present invention relates to an in-line lubrication plant for rolling rolls, preferably hot, of a metal strip, preferably steel, said lubrication being essentially carried out by spraying or atomizing a lubricant. or a mixture of lubricants on a target comprising said rolls and / or said strip, preferably in the vicinity of the gap of the working rolls, characterized in that it comprises a substantially closed box provided with:

• means for forming a cloud of lubricant droplets smaller than 2 mm, preferably less than 700 μm, and more preferably less than 200 μm;
• an adjustable aperture diaphragm associated with said means and placed on a front face of the housing and
• an excess lubricant recovery device on the part of the diaphragm internal to the box and on the internal walls of the box.

According to the invention, said lubricant possesses a purity of at least 95% and a boiling temperature greater than 130 ° C, and preferably a temperature boiling above 300 ° C and a flash point greater than 180 ° C. This requirement therefore excludes water as lubricant as well as oil emulsions in the water. At the limit, traces of water present in the lubricant, within its purity, may to be tolerated.

The installation of the invention is provided with means of controlling the temperature of the box, preferably comprising an electrical resistance or a water circuit. Temperature control provides a better controllability of the process in general and in particular reduces the problems related to the viscosity of the lubricant.

In a particularly advantageous manner, said temperature control means are associated to the use of a solid lubricant at temperature ambient and liquid at a working temperature of installation above room temperature.

Still according to the invention, said means of formation of a cloud of droplets comprises at least one nozzle or injector without air, preferably a jet of full cone type, or an internal mixing atomizer or external lubricant suspended in air or gas inert or an ultrasonic atomizer.

Advantageously, the installation comprises a plurality of nozzles or injectors or atomizers distributed the width of the rolling line, some of which can be made non-operational to adapt to the effective width of the band and / or quantity surface of lubricant to be deposited.

More preferably, the installation comprises means for cutting said sprinklers, ie one out of two, either randomly.

Advantageously, the box is subdivided into at least two parts, each part comprising a diaphragm and an associated device for recovering lubricant.

According to a preferred embodiment, the excess lubricant recovery device and / or the diaphragm (s) is (are) made of a material pierced with a plurality of holes or in a porous material.

According to another execution modality preferred, the lubricant recovery device surplus includes a closed circuit for the circulation of lubricant with pumping equipment and possibly lubricant recycling.

It results from the characteristics of the invention that the atmosphere of the box is confined.

An additional feature of the invention is that the spray angle, the opening the diaphragm (s) and their number on the face front of the box, as well as possibly the dimensions of the box, are chosen according to the width of the cylinders and / or the tape to be lubricated and the speed of the band.

Advantageously, the installation of the invention comprises means for increasing the opening of the diaphragm (s) with the scroll speed of the band, which is also equal to the tangential speed cylinders.

Always advantageously, the internal walls of the box are made of a material allowing suction of the lubricant.

In the context of the invention, the band scrolls at a speed ranging from 0.5 to 20 m / s.

• on règle les paramètres d'injection de lubrifiant, notamment la pression et la température, de manière à obtenir le débit de lubrifiant désiré ;
• on règle l'ouverture du (ou des) diaphragme(s) en fonction de la quantité surfacique de lubrifiant à déposer et de la vitesse de la bande ;
• on récupère par récolte et pompage le lubrifiant excédentaire et on renvoie celui-ci en circuit fermé dans le caisson, éventuellement après recyclage.

A second subject of the present invention relates to a process for the in-line lubrication of rolling rolls, preferably hot rolls, of a metal strip, preferably made of steel, said lubrication being essentially carried out by spraying or atomizing a lubricant. or a mixture of lubricants on a target comprising said rolls and / or said strip, preferably in the vicinity of the gap of the working rolls, implementing an installation according to any one of the preceding claims,
characterized by the following steps:

• the lubricant injection parameters, in particular the pressure and the temperature, are adjusted so as to obtain the desired lubricant flow rate;
• the opening of the diaphragm (s) is adjusted according to the surface quantity of lubricant to be deposited and the speed of the strip;
• the excess lubricant is recovered by harvesting and pumping and the latter is returned in closed circuit to the box, possibly after recycling.

It is essential according to the invention that the opening of the diaphragm or diaphragms is adjusted to deposit on the target a surface amount ("plate-out") of lubricant of between 0.01 and 1 g / m ² .

Advantageously, the injection parameters of lubricant are regulated in open or closed loop.

Brief description of the figures

Figure 1 schematically represents a nozzle for atomizing oil in the air, mixing internal, according to the state of the art.

Figure 2 schematically represents a first preferred embodiment of this invention.

Figure 3 schematically represents a second preferred embodiment of this invention.

Figure 4 schematically represents a third preferred embodiment of this invention.

Description of a preferred embodiment of the invention

The idea behind the present invention is combined use in a lubrication device a means for spraying fine droplets of lubricant and a diaphragm equipped with a oil recovery.

As shown in FIGS. 2 to 4, the The present invention relates more specifically to a spray lubrication system comprising a sprayer (or vaporizer) 1 of pure lubricant or a mixture of lubricants such as lubricants-based carbon, silicone or even molybdenum disulfide. This or these lubricants have a degree of impurities or usual additives for products of this type commercially available (eg maximum 5%). Of preferably, the spraying is carried out in the presence air. Lubricants will be chosen as part of the present invention so as to have a temperature boiling above 130 ° C.

• d'un moyen de pulvérisation 10 ;
• d'un ou plusieurs diaphragmes 3,3' à ouverture réglable permettant d'ajuster la quantité de lubrifiant sortant du pulvérisateur ;
• d'un système de récupération 4 de l'excédent de lubrifiant sur la partie interne du ou des diaphragmes et/ou sur la surface interne du caisson 1. Ce système de récupération peut être réalisé dans un matériau percé de multiples trous ou dans un matériau poreux. Le diaphragme peut lui-même être réalisé dans le même matériau.

This system is based on the combined use in a spray box 1:

• a spraying means 10;
• one or more diaphragms 3,3 'with adjustable opening to adjust the amount of lubricant coming out of the sprayer;
• a recovery system 4 of excess lubricant on the inner part of the diaphragm or diaphragms and / or on the inner surface of the casing 1. This recovery system can be made of a material pierced with multiple holes or in a material porous. The diaphragm may itself be made of the same material.

The function of the spray box 1 is to confine the atmosphere created by the fog of spray.

In the context of the present invention, "spray" means either a spray or a spray atomisation, ie the reduction of the lubricant, at starting in the liquid state, in fine droplets, respectively in the presence or absence of air under pressure, leading to a droplet size ranging from a few microns to several millimeters, for example 2 mm, depending on the particular technology employed.

• soit un gicleur muni d'orifices de sortie de diamètre élevé, produisant des gouttelettes dont le diamètre est de l'ordre de 1 à 3 mm, plutôt adapté aux débits de pulvérisation importants ;
• soit un injecteur (sans air), de préférence un gicleur de type à cône plein, présentant des orifices de sortie de diamètre allant de 100 à 150 microns typiquement ; les gouttelettes produites sont distribuées de manière gaussienne avec une taille maximale inférieure à 700 microns environ ;
• soit un atomiseur à mélange interne ou externe (air) permettant d'obtenir une taille (diamètre) de gouttelettes inférieure à 200 microns environ ;
• soit un atomiseur à ultrasons permettant de créer une pulvérisation très précise en débit et en géométrie.

Thus the aforementioned spraying means 10, which defines the size of the droplets produced, may be, according to preferred embodiments of the invention:

• either a nozzle provided with high diameter outlet orifices, producing droplets whose diameter is of the order of 1 to 3 mm, rather adapted to large spray rates;
• either an injector (without air), preferably a solid cone type nozzle, having outlet orifices of diameter typically ranging from 100 to 150 microns; the droplets produced are distributed in a Gaussian manner with a maximum size of less than about 700 microns;
• an internal or external mixing atomizer (air) for obtaining a size (diameter) of droplets of less than about 200 microns;
• an ultrasonic atomizer to create a very precise spray rate and geometry.

These types of devices do not induce any limitation in pressure or temperature, but they must to be regulated.

FIG. 1 shows an atomizer oil / air with internal mixing known in the state of the and can advantageously serve as a means of Spray 10 according to the present invention. The air 12 is injected according to a ring 12 'surrounding the flow of oil 11, which makes it possible to obtain a conical cloud 20 atomization. According to the principle of atomization, the cloud of droplets is formed by the shock occurring between the oil from the oil nozzle 11 and the air (or a gas inert) injected 12, the oil being dispersed in the air just before the release of the oil from the atomizer.

In the case of external mixing atomizers, the oil flow is adjustable by changing the pressure of oil, the air pressure can be adjusted separately.

Figure 2 shows a sprayer according to a first preferred embodiment of the invention, comprising a only diaphragm 3, while figure 3 shows a sprayer according to a second preferred mode of the invention, comprising two diaphragms 3,3 '.

• réduire la hauteur du caisson de pulvérisation ;
• limiter la quantité de brouillard sortant du pulvérisateur.

The intermediate diaphragms 3 ', as installed in FIG. 3, aim to:

• reduce the height of the spray box;
• limit the amount of mist coming out of the sprayer.

The internal side walls of the box may be covered with a common material 5 or alternatively a material allowing the suction of the lubricant, as shown in Figure 4.

According to a particular modality embodiment of the invention, the excess oil or lubricant, located on the inner walls and on the diaphragm, is sucked outside, recycled and reintroduced into the lubrication device.

• élimination de l'interaction eau-huile, d'où meilleure contrôlabilité et meilleure efficacité du procédé, avec, le cas échéant, élimination du problème de bouchage des tubes ;
• possibilité d'utiliser des lubrifiants se trouvant à l'état solide à température ambiante, en les préchauffant initialement ;
• possibilité d'utiliser des lubrifiants purs ou des émulsions très concentrées en lubrifiant ;
• homogénéisation de la distribution d'huile sur la surface des cylindres ;
• optimisation de l'efficacité d'accrochage de l'huile sur le cylindre. En effet, la meilleure condition de pulvérisation est choisie puis l'ouverture du diaphragme est réglée pour laisser passer la quantité désirée d'huile. L'ouverture du diaphragme peut suivre l'augmentation de la vitesse des cylindres. Le seul paramètre libre du système est donc l'ouverture du (des) diaphragme(s). Les mesures effectuées ont permis de constater que l'efficacité de l'atomisation reste dans une large mesure constante en fonction de l'importance du dépôt surfacique d'huile, au contraire de la pulvérisation d'émulsions stables qui subissent un phénomène de ruissellement aux dépôts surfaciques élevés.

The present invention has the following advantages:

• elimination of the water-oil interaction, hence better controllability and better efficiency of the process, with, where appropriate, eliminating the problem of clogging of the tubes;
• possibility of using lubricants in the solid state at room temperature, initially preheating them;
• possibility of using pure lubricants or emulsions with a high concentration of lubricant;
• homogenization of the oil distribution on the surface of the rolls;
• optimization of the efficiency of attachment of the oil on the cylinder. Indeed, the best spraying condition is chosen and the aperture of the diaphragm is adjusted to let the desired amount of oil. The opening of the diaphragm can follow the increase in the speed of the cylinders. The only free parameter of the system is thus the opening of the diaphragm (s). The measurements carried out have made it possible to observe that the efficiency of the atomization remains to a large extent constant as a function of the importance of the surface deposition of oil, unlike the spraying of stable emulsions which undergo a runoff phenomenon at the same time. high surface deposits.

Claims (18)

In-line lubrication system for rolling rolls, preferably hot-rolled, of a metal strip, preferably of steel, said lubrication being essentially carried out by spraying or atomizing a lubricant or a mixture of lubricants on a target comprising said cylinders and / or said band, preferably in the vicinity of the interstice of the working rolls, characterized in that it comprises a substantially closed box (1) provided with: means (10) for forming a cloud of lubricant droplets less than 2 mm in size, preferably less than 700 μm, and more preferably less than 200 μm; a diaphragm (3,3 ') with adjustable opening associated with said means (10) and placed on a front face of the box and an excess lubricant recovery device (4) on the portion of the diaphragm internal to the box and on the inner walls of the box. Plant according to claim 1, characterized in that said lubricant has a purity of at least 95% and a boiling point above 130 ° C, and preferably a boiling point above 300 ° C and a flash point greater than 180 ° C. Installation according to claim 1 or 2, characterized in that it is provided with means for controlling the temperature of the box (1), preferably comprising an electrical resistance or a water circuit. Installation according to claim 3, characterized in that said temperature control means are associated with the use of a solid lubricant at ambient and liquid temperature at a working temperature higher than the ambient temperature. Installation according to any one of the preceding claims, characterized in that said means (10) for forming a cloud of droplets comprises at least one nozzle or injector without air, preferably a full cone-type nozzle, or an atomizer with internal or external mixing of lubricant suspended in air or in an inert gas or an ultrasonic atomizer. Installation according to claim 5, characterized in that it comprises a plurality of nozzles or injectors or atomizers distributed over the width of the rolling line, some of which may be rendered non-operational in order to adapt to the effective width of the strip and or the surface quantity of lubricant to be deposited. Installation according to claim 6, characterized in that it comprises means for cutting said nozzles, either one out of two, or randomly. Installation according to any one of claims 1 to 7, characterized in that the box (1) is subdivided into at least two parts, each part comprising a diaphragm (3,3 ') and an associated lubricant recovery device (4). ). Installation according to one of the preceding claims, characterized in that the excess lubricant recovery device (4) and / or the diaphragm (s) (3,3 ') is (are) embodied in a material pierced with a plurality of holes or in a porous material. Installation according to any one of the preceding claims, characterized in that the excess lubricant recovery device (4) comprises a closed lubricant circulation circuit provided with pumping equipment and optionally recycling of the lubricant. Installation according to any one of the preceding claims, characterized in that the atmosphere of the box is confined. Installation according to any one of the preceding claims, characterized in that the spray angle, the opening of the diaphragm or diaphragms and their number on the front face of the box, as well as possibly the dimensions of the box, are chosen according to the width of the rolls and / or the strip to be lubricated and the speed of the strip. Installation according to claim 12, characterized in that it comprises means for increasing the opening of the diaphragm (s) with the running speed of the strip, which is also equal to the tangential speed of the rolls. Installation according to any one of the preceding claims, characterized in that the internal walls of the box are made of a material (5) allowing the suction of the lubricant. Installation according to any one of the preceding claims, characterized in that the strip travels at a speed ranging from 0.5 to 20 m / s. A method of in-line lubrication of rolling rolls, preferably hot rolling, of a metal strip, preferably steel, said lubrication being essentially carried out by spraying or atomizing a lubricant or a mixture of lubricants on a target comprising said cylinders and / or said band, preferably in the vicinity of the interstice of the working rolls, implementing an installation according to any one of the preceding claims, characterized by the following steps: the lubricant injection parameters, in particular the pressure and the temperature, are adjusted so as to obtain the desired lubricant flow rate; the opening of the diaphragm (s) is adjusted according to the surface quantity of lubricant to be deposited and the speed of the strip; the excess lubricant is recovered by harvesting and pumping and the latter is returned in closed circuit to the box, possibly after recycling. Method according to claim 16, characterized in that the opening of the diaphragm or diaphragms is adjusted to deposit on the target a surface amount ("plate-out") of lubricant of between 0.01 and 1 g / m ² . Method according to Claim 16 or 17, characterized in that the lubricant injection parameters are regulated in open or closed loop.

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