Abstract:
A method for lubricating rolls, especially work rolls of a rolling stand, and rolling stock passed between the rolls during the rolling operation, in which a lubricant-gas mixture, a lubricant-water-gas mixture, a lubricant-water mixture and/or a grease-medium mixture is applied to the rolls or the rolling stock on the run-in side of the rolling stand, wherein the mixture is prepared with at least one mixing device in the area upstream of the rolling stand.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a Divisional Application of U.S. patent application Ser. No. 13/000,281, filed Jan. 25, 2011, which is a 371 of International application PCT/EP2009/004138, filed Jun. 9, 2009, which claims priority of DE 10 2008 028 620.6, filed Jun. 18, 2008, and DE 10 2008 034 099.5, filed Jul. 21, 2008, and DE 10 2008 050 392.4, filed Oct. 28, 2008, the priority of these applications is hereby claimed and these applications are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention concerns a method for lubricating rolls, especially work rolls of a rolling stand, and rolling stock passed between the rolls during the rolling operation, in which a lubricant-gas mixture, a lubricant-water-gas mixture, a lubricant-water mixture, and/or a grease-medium mixture is applied to the rolls or the rolling stock on the run-in side of the rolling stand. 
         [0003]    The rolling stand comprises several mutually supporting rolls, including, for example, a work roll, which comes into direct contact with the rolling stock and in turn rolls on a generally larger backup roll or intermediate roll. Many hot rolling mills for rolling a metal strip have an integrated roll gap lubricating system. These systems are used for the purpose of improving the surface quality of the work roll and the strip and have become part of the standard equipment of a rolling mill on which high-quality strip is to be produced. In one widely used system, a mixture of water as the base medium with oil is applied to the rolling stock or to the work roll or backup roll. 
         [0004]    In the cold rolling process, lubrication is customary. In this case, lubricant is applied to the rolling stock and/or to the work roll and/or is sprayed into the roll gap. The mixing of the oil and water is carried out far from the rolling stand. In most cases, an emulsion is used, which, in a complicated process in a circulation system, is separated, cleaned and resupplied to the lubricating system. 
         [0005]    WO 03 002277 A1 discloses a method and a device for cooling and/or lubricating rolls, especially work rolls, of a rolling stand, in which water in the form of spray jets is used as a cooling medium, and oil, an oil-air mixture, an oil-water mixture, an oil-water-air mixture, or grease mixtures are used as lubricants. To improve the lubricating and cooling effect, the combined use of supercooling of the strip and roll surface and roll lubrication on the run-in side of the rolling stand is proposed, in which the two media—water and lubricant—are supplied separately to the rolls and the rolling stock and are applied to different points of application on the surface of the roll. Separate supply lines to the spray bars are provided for water and the lubricant. 
       SUMMARY OF THE INVENTION 
       [0006]    The objective of the invention is to create a simplified method of lubrication during the rolling of a metal strip, which can be used both in cold rolling and in hot rolling. 
         [0007]    In accordance with the invention, this objective is achieved in a method of the aforementioned type by preparing the mixture with at least one mixing device in the area upstream of the rolling stand. In the cold rolling process, much as in the hot rolling process, the goal of the new lubricating method is to produce the lubricant just before its use or application and thus to avoid the complicated preparation in a closed circulation. To realize economical use of the method, a further goal of the invention is to minimize the amount of lubricant that is used. The same goal also applies to the use of the lubricating method of the invention for hot rolling. While reducing the amount of lubricant that is used, at the same time it is intended that the lubricating action be optimized and that it be possible to adjust the lubricating effect. 
         [0008]    Examples of lubricants that can be used are oil-water dispersions, oil-water emulsions, oil-free water-miscible lubricants, oil-air mixtures, or oil-water-air mixtures. The media can be sprayed in 2-, 3- or 4-component nozzles. 
         [0009]    To reduce the amount of lubricant, it is especially advantageous to atomize the lubricant with air. In a preferred embodiment, oil and water are mixed just before being atomized with air. This makes it possible to apply even extremely small amounts of oil to the surfaces of the rolls or to the rolling stock. In the case of hot rolling, the mixing of oil and water has the advantage, compared to the use of pure oil, that there is no fire hazard. 
         [0010]    In the case of cold rolling, the new method of lubrication has the advantage that the oil concentration in the lubricant can be varied very quickly and flexibly. In this way, the lubricant can be optimally adjusted to different materials to be rolled, to different strip speeds, to varying drafts, and to the given rolling stand. In addition, it is also possible to prepare different oils and lubricants for different applications. 
         [0011]    Since the amounts of lubricant are so small that just the roll and/or strip surface is wetted, there is no need for a complicated preparation process. The used lubricant, together with the water from the cooling systems and possibly other oil leakages, is conveyed to the wastewater treatment plant, and the oil is separated there. 
         [0012]    Advantageous refinements of the invention are described in the dependent claims. 
         [0013]    One of the advantageous provisions of the invention is that water and at least one lubricant are conveyed to a mixer through separate supply lines and are mixed in the mixer to form a water-lubricant dispersion or emulsion. In this connection, it can be provided that the water-lubricant dispersion or emulsion is atomized in atomizing nozzles by means of a gas, especially air, and applied to at least one of the work rolls and/or to the rolling stock. 
         [0014]    3-component or 4-component mixing nozzles or atomizing nozzles, in which the water, the one or more lubricants, and the air are mixed, are preferably used. Naturally, it is possible, in accordance with the invention, to use a gas other than air or to use a mixture of gases. 
         [0015]    Preferably, the one or more lubricants are first mixed with the water in a supply line to form a mixture, and then the mixture is mixed with the gas in the inner chamber of the 3-component or 4-component mixing nozzle. Alternatively, the water, the one or more lubricants, and the gas are mixed in the inner chamber of the 3-component or 4-component mixing nozzle. 
         [0016]    The lubricant-gas mixture, the lubricant-water-gas mixture, the lubricant-water mixture and/or the grease-medium mixture is preferably distributed over the entire width of at least one of the work rolls and/or the rolling stock. 
         [0017]    It has also been found to be advantageous if the amount of water, the one or more lubricants, the gas, the lubricant-gas mixture, the lubricant-water-gas mixture, the lubricant-water mixture and/or the fat-medium mixture is distributed by means of control valves over the width of at least one of the work rolls and/or the rolling stock. 
         [0018]    In another embodiment of the method, it is provided that the amount and/or the pressure of the one or more lubricants, the water, the lubricant-water mixture, the lubricant-gas mixture, and/or the fat-medium mixture is automatically controlled over the width of at least one of the work rolls and/or the rolling stock by means of the control valves and/or in flowmeters, pressure controllers, and/or in mixing blocks. 
         [0019]    It can also be provided that the one or more lubricants, water and gas are mixed in a 3-component nozzle, wherein the amount of lubricant is automatically controlled in sectors over the width of at least one of the work rolls and/or the rolling stock, and that the pressure and/or the volume of the gas and the water is automatically controlled. 
         [0020]    Alternatively, the mixing operation is realized in such a way that the one or more lubricants and the gas are mixed in a mixing block and that water is then added in 2-component mixing nozzles. In this case, the water can be admixed outside an inner nozzle tube of the 2-component mixing nozzles. 
         [0021]    In another advantageous embodiment of the method, the one or more lubricants are mixed with the gas, especially in a mixing block, and sprayed by nozzles onto at least one of the rolls and/or the rolling stock, while water is sprayed next to the nozzles. 
         [0022]    Preferably, a flatness control system is used to automatically control the supply of the one or more lubricants in zones over the width. 
         [0023]    The invention also concerns a device for lubricating at least one roll and/or rolling stock rolled between the rolls in a rolling stand. 
         [0024]    In accordance with the invention, the device is characterized by the fact that it has at least one mixing block and/or multicomponent mixing devices, especially atomizing nozzles, for mixing water, gas, and at least one lubricant, especially an oil, to form a lubricant-gas mixture, a lubricant-water-gas mixture, or a lubricant-water mixture. 
         [0025]    It is advantageous for the device to have automatic control devices, especially control valves, for determining the amount of the mixture to be sprayed by spray devices onto at least one of the rolls and/or onto the rolling stock. 
         [0026]    It is advantageous for the automatic control devices to be arranged in zones over the width of the one or more rolls or the rolling stock. In this connection, it is also possible to provide flowmeters and pressure controllers. 
         [0027]    The multicomponent mixing devices are designed either as internal mixers or external mixers. Preferably, they comprise a turbulence plate or a venturi tube. 
         [0028]    It is advantageous to provide water spray bars above and/or below spray devices for spraying a lubricant-containing mixture onto at least one roll and/or onto the rolling stock. This has a fire protection effect in the case of hot rolling. Flammable oil or lubricant is shielded by a water spray curtain and thus cannot heat up and cause a fire. 
         [0029]    In addition, it is advantageous to equip the device with an automatic control device for controlling the flatness of the rolled strip by evaluating signals of a flatness measuring device, especially a flatness measuring roller. 
         [0030]    The flatness measuring device preferably comprises a flatness measuring roller, which generates signals that correspond to the flatness of the rolled strip and relays the signals to the spray devices for the purpose of adjusting the amounts or concentrations of the one or more lubricants. The use of the flatness measuring device makes it possible to consider even higher order flatness of the rolled strip by evaluation of the signals of the flatness measuring roller, and corrective measures can be taken, for example, by changing the amounts or concentrations of the lubricant. 
         [0031]    The spray devices are preferably arranged in two rows essentially parallel to the axis of the roll, especially offset from each other, so that even in the event of failure of some of the spray nozzles, adequate lubrication of the roll surface or of the rolling stock can still be guaranteed. 
         [0032]    The invention also concerns a rolling stand, in which a device of the type described above is used for lubricating a roll and/or the rolling stock. 
         [0033]    The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, specific objects attained by its use, reference should be had to the drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0034]    In the drawings: 
           [0035]      FIG. 1  shows a rolling installation with an oil-water-air lubricating system, which has a lubricant supply that is variable over the width and in which the lubricant is sprayed onto the upper work roll. 
           [0036]      FIG. 2  shows a rolling installation with an oil-water-air lubricating system, in which the lubricant is sprayed onto the upper work roll in equal amounts over the length. 
           [0037]      FIG. 3  shows a rolling installation with an oil-water-air lubricating system, which has a lubricant supply that is variable over the width and in which the lubricant is sprayed onto the underside of the rolling stock. 
           [0038]      FIG. 4  shows a rolling installation with an oil-water-air lubricating system, which has a plurality of 3-component mixing nozzles with gas-liquid atomizers and in which the lubricant is sprayed onto the upper work roll. 
           [0039]      FIG. 5  shows an embodiment of a 3- or 4-component mixing nozzle for mixing water, lubricant and gas, as used, for example, in the rolling installation illustrated in  FIG. 3 . 
           [0040]      FIG. 6  shows a two-row arrangement of mixing nozzles for applying lubricant to a roll or rolling stock. 
           [0041]      FIG. 7  shows a rolling installation with an oil-water-air lubricating system with a plurality of 3-component mixing nozzles with gas-liquid atomizers and with control valves assigned to each 3-component mixing nozzle for automatically controlling the amount of lubricant, in which the lubricant is sprayed onto the upper work roll. 
           [0042]      FIG. 8  shows a rolling installation with an oil-water-air lubricating system, in which lubricant and gas are mixed in a mixing block, and water is added in a plurality of 2-component mixing nozzles, and the lubricant is sprayed onto the upper work roll. 
           [0043]      FIG. 9  shows the mixing block according to  FIG. 8  in combination with a 2-component mixing nozzle in longitudinal section, wherein the media mix outside the mixing nozzle. 
           [0044]      FIG. 10  shows a 3-component mixing nozzle for mixing water, lubricant and gas with a mixture of the liquid media before entrance into the medium chamber in longitudinal section. 
           [0045]      FIG. 11  shows another 3-component nozzle for mixing water, lubricant and gas with a mixture of the liquid media before entrance into the medium chamber in longitudinal section, wherein all of the media mix in the medium chamber. 
           [0046]      FIG. 12  shows a rolling installation with an oil-water-air lubricating system, in which lubricant and gas are mixed in a mixing block, the lubricant is sprayed onto both work rolls, and at the same time water spray bars are provided as fire protection devices. 
           [0047]      FIG. 13  shows the rolling installation according to  FIG. 7  but with the addition of a flatness measuring roller and a flatness control system. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0048]    A rolling installation  1  ( FIG. 1 ) comprises two work rolls  2 ,  3 , which are supported between two backup rolls  4 ,  5  and roll rolling stock  6  ( FIG. 3 ). In this operation, a lubricant, especially a first and a second oil, or additional oils and water are first supplied via separate supply lines  7 ,  8 , and  9 . First, the two oils are mixed together. Alternatively, only one oil or the other is used. The desired amounts of water and the two oils are adjusted by metering pumps  10 ,  11  and pumped to a mixer  12 . A dispersion or emulsion of the two liquids brought together in this way is formed downstream of the mixer  12 . To avoid separation of the mixture, the distance between the mixer  12  and control valves  13  downstream of the mixer is preferably very small, or the mixer and control valves are constructed as a single unit. The control valves  13  are distributed over the entire width of the upper work roll  2 . If relatively long pipelines cannot be avoided, turbulence plates (mixers) are installed a certain distance apart in the lines. The pipeline cross section is preferably selected as small as possible in order to realize a flow rate as high as possible and thus a short conveyance time. To be able to adjust a lubricant load over the width of the work roll  2  and also to be able to adjust it as a function of the width of the rolling stock  6  that is being processed, the control valves  13  deliver lubricant to downstream atomizing nozzles  14 , which are designed as 2-component mixing nozzles, according to the width of the rolling stock  6 . In the atomizing nozzles  14 , air is added to the mixture of lubricant and water. The air is supplied through a line  15  with a pressure controller for adjusting the air pressure. The amounts of lubricant or oil and the amounts of water are adjusted by a computer model and/or an automatic control device, which takes into account the various lubricating properties as a function of the strip material to be rolled, the strip speed, the draft, the temperatures and other parameters. The activation of the control valves  13  and the amounts pumped by the metering pumps  10 ,  11  are coordinated with each other. The automatic control device determines the lubricant concentrations or the types of lubricants and also carries out automatic crown and flatness control of the rolled strip  6 . Unflatness of the rolled strip  6  is then compensated by adjusting the amounts of lubricant supplied or by varying other parameters. If necessary, the level of rolling force can be controlled by varying the amount of oil, the type of oil, the concentration of oil in the water and/or the oil mixing proportions. 
         [0049]    In a simplified embodiment of the rolling installation  1  ( FIG. 2 ), there are no control valves  13 . In this case, the flow through the atomizing nozzles  14  is manually adjusted or results from the adjustment of the metering pump. In another embodiment ( FIG. 3 ), the lubricant-water-air mixture is applied directly to the underside of the rolling stock  6 . Control valves  13  are also provided in this case. 
         [0050]    In another embodiment ( FIG. 4 ), water, the lubricant, for example, oil, and air are first supplied through separate lines  7 ,  9 ,  15  and then applied to the upper work roll  2  by atomizing nozzles  14  or  17  in the form of 3-component nozzles, wherein the mixing and atomizing of the fluids constitute a unit in the atomizing nozzles  17 . However, in this case as well, control devices can be provided, which individually control the supply of the given fluid to the individual atomizing nozzles  17  or to a group of atomizing nozzles. Preferably, all of the individual automatic control devices are integrated in an automatic control system, which determines the volume and the mixing proportions of the fluids that are delivered by the atomizing nozzles  17  to the work roll  2  or the rolling stock  6 . Naturally, in all of the embodiments ( FIGS. 1 to 4 ), analogous designs are provided or can be provided for supplying a lubricant-water-air mixture to the lower work roll  3  and/or to the upper side of the rolling stock  6 . 
         [0051]    An atomizing nozzle  17  ( FIG. 5 ) is realized as an internal mixer pressure mixing nozzle with an inner chamber  18 , into which water and two lubricants are fed at one end through a supply line  19  and, if necessary, are mixed by means of, e.g., turbulence plates  36  or a pipe constriction  37 . The operation of mixing the liquids takes place just before the atomization. The mixer and nozzle constitute a unit here. Two lines  20 ,  21  first carry the lubricants into the supply line  19  immediately before the lubricants are delivered into the inner chamber  18 . A gas, especially air, enters the inner chamber  18  through another feed line  22  and is mixed in the inner chamber  18  with the mixture of water and the two lubricants. The mixture then leaves the nozzle orifice  23  in a conical spray and strikes the surface of a roll or the surface of the rolling stock  6 . Since the lubricant (for example, oil) or a plurality of lubricants is the most important component, it is also possible, in accordance with the invention, to control only the individual amount of oil per atomizing nozzle  17  and to control the other components in sections, i.e., over relatively large sections of the width of a roll and/or the width of the rolling stock  6 . The lubricant or lubricants can also be applied solely with the use of compressed air, i.e., without the use of water. In this case, a 2-component nozzle is used. 
         [0052]    Especially in the case of cold rolling, it is important that the lubricant film acts completely over the entire width of the rolling stock  6 . If the oil film breaks down, undesirable scratches are produced on the surface. To guarantee redundancy of the lubricant effect, two or more rows  24 ,  25  ( FIG. 6 ) of atomizing nozzles  17  are preferably provided opposite a roll, for example, work roll  2 , or opposite the rolling stock  6 . The atomizing nozzles  17  in the two or more rows  24 ,  25  are preferably offset from one another. Alternatively, a one-row nozzle spray bar can be used, whose nozzles have a large angle of spray, so that double coverage is realized. This means that if one nozzle fails, the adjacent nozzles cover this area. 
         [0053]    Similarly to the embodiments illustrated in  FIGS. 1 and 3 , other embodiments of the invention have automatic control devices  26  ( FIG. 7 ), with which the supply of the lubricant to each atomizing nozzle  14  is individually controlled over the entire width of the strip. The overall effect of the lubrication can be further influenced by varying the amounts of water and air. In the case of hot rolling, lubricant is applied to at least one of the work rolls  2 ,  3 , while in the case of cold rolling, lubricant is preferably applied to the rolling stock  6 . 
         [0054]    According to another variant ( FIG. 8 ), lubricant and air are brought together in a mixing block  27 . The air carries the lubricant to the atomizing nozzles  14 . Each of the nozzles  14  is individually fed. The water is supplied to the nozzles  14  separately. 
         [0055]    In the mixing block  27  ( FIG. 9 ), first the lubricant and air from the lines  7  and  15  are brought together. The mixture is then fed by a line  28  to a 2-component nozzle  29 , in which it is combined with water supplied by the line  8 . The 2-component nozzle  29  is designed as an external mixer. This means that the lubricant-air mixture and the water do not come together until they reach the nozzle orifice  30 . The mixing is made possible by two hollow cones formed by the fluids spraying into each other. The advantage of this 2-component nozzle  29  is that saponification is prevented, since the lubricant and water do not come into contact with each other until they arrive at the nozzle orifice  30 . The water supply can be shut off to realize pure lubricant-air lubrication. 
         [0056]    In a 2-component nozzle  31  ( FIG. 10 ), which is designed as an internal mixer with an inner chamber  32 , oil and water are first introduced together into the inner chamber  32  through a feed line  33 , and air is introduced separately. Turbulence plates  34  or a venturi tube is installed in the oil-water supply line  33  to guarantee thorough mixing of the media. 
         [0057]    A 3-component nozzle ( FIG. 11 ) likewise has an inner chamber  32 , into which the media oil, water and air are separately fed through lines  7 ,  8 , and  15 . The liquid media are thus not mixed until they reach the inner chamber  32 , and they are then atomized and sprayed. 
         [0058]    When one wishes to use an oil-air mixture without having to add water as an additional component, then in the case of hot rolling, provision is made for fire protection, when necessary, by producing a water curtain that shields the oil-air mixture towards the outside by means of water spray bars  38 ,  39  ( FIG. 12 ). In addition, shielding walls  40 ,  41  are placed around the oil-air mist produced by the atomizing nozzles  14 . The oil-air mist can be exhausted to the outside. The shielding walls  40 ,  41  as well as the nozzle spray bars  14  are designed to swivel in order to improve the shielding and to allow the nozzles to be placed just in front of the roll. Similar exhausting is also provided for the lubricant application to the rolling stock (in the case of cold rolling). 
         [0059]    In another embodiment of the invention, to control the surface structure (flatness, uniform state of stress) of the rolled strip  6 , a flatness measuring roller  42  ( FIG. 13 ) or other type of contactless (optical) flatness measuring system is provided to determine unevenness of the rolled strip  6 . This measuring system transmits signals via a signal line  43  to an evaluation unit (not shown here). The evaluation unit generates signals for controlling or regulating the atomizing nozzles  14  or control valves  13  to deliver properly adjusted amounts of lubricant to the work roll  2  over the width of the strip. Parabolic or higher order strip flatness can be influenced by the amount or concentration of lubricant delivered per zone. Naturally, corresponding automatic control can also be applied with respect to the lower work roll  3 . The atomizing nozzles  14  can also spray the lubricant directly onto the rolling stock  6  to influence the strip flatness and the strip stress distribution over the width of the strip. 
         [0060]    While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.