Method and system for the application of a lubricant during cold rolling of a rolling stock in a roll stand

Abstract

The invention relates to a method and a system (20) for applying a lubricant (11) during the cold rolling of a metallic rolled stock (2) in a rolling stand (1) with two work rolls (3, 4) spaced apart from each other by a roll gap (7). The lubricant (11) is dispensed by several single-component nozzles, each designed as a flat jet nozzle, either onto a surface (2.1, 2.2) of the rolled stock (2) or onto a surface of a work roll (3, 4). Each single-component nozzle dispenses a lubricant quantity in the range of 200 ml / min to 500 ml / min at a pressure in the range of 2 bar to 10 bar, and the lubricant quantity dispensed by each single-component nozzle is regulated such that the lubricant quantity dispensed by the single-component nozzle per unit area onto a surface (2.1, 2.2) of the rolled stock (2) or onto a surface of a work roll (3, 4) is essentially independent of the instantaneous rolling speed.

Description

[0001] The invention relates to a method and a system for applying a lubricant during cold rolling of a metallic rolling stock in a rolling stand.

[0002] During cold rolling of a metallic rolled stock in a rolling stand, the rolled stock is passed through a roll gap between two work rolls of the rolling stand at a temperature below its recrystallization temperature, whereby its thickness is reduced. The rolling stand is either a so-called tandem rolling stand or a so-called reversing rolling stand. In a tandem rolling stand, the rolled stock is passed only once in one rolling direction. As a rule, a tandem rolling stand is part of a so-called tandem mill with several tandem rolling stands arranged one behind the other, through which the rolled stock is passed, whereby the thickness of the rolled stock is successively reduced. As the thickness of the rolled stock is reduced, the rolling speed, i.e. the speed of the rolled stock, increases along the tandem mill.The rolling stock is guided through a reversing rolling stand several times in so-called rolling passes, whereby the rolling stock is guided through the reversing rolling stand in successive rolling passes in opposite rolling directions.

[0003] The side of a rolling stand on which the rolling stock is fed into the roll gap is called the entry side of the rolling stand. The side of a rolling stand on which the rolling stock exits the roll gap is called the exit side of the rolling stand. In a reversing rolling stand, therefore, the exit side of one rolling pass is the entry side of the subsequent rolling pass, and vice versa.

[0004] In order to reduce the friction between the rolling stock and the work rolls, the roll gap of a rolling stand is lubricated.

[0005] Lubrication reduces the energy required for rolling, increases the service life of the work rolls and improves the surface quality of the rolled material.

[0006] EP 2 651 577 B1 discloses a method and a device for applying a lubricant during the rolling of metallic rolled stock, in particular a rolled strip guided through a roll gap between two work rolls. In the method, a mixture of lubricant and a carrier gas is generated in an atomization device. The mixture is supplied to individual spray nozzles in an array of spray nozzles to generate a continuous spray jet in the direction of the width of the rolled strip. By means of the spray jet, the mixture is applied to the surface of at least one of the work rolls and / or to the surface of the rolled strip.

[0007] WO 2020 / 221654 A1 discloses a method and a rolling apparatus for rolling a rolled stock. The rolled stock is alternately guided in two opposing rolling directions through a roll gap between two work rolls of a reversing rolling stand. A lubricant is introduced into a contact zone where the rolled stock rests against the work rolls to lubricate the contact zone, and a coolant is applied to the rolled stock and / or the work rolls. The lubricant, in a mixture with a carrier gas, is sprayed onto the work rolls and / or the rolled stock exclusively on an exit side of a rolling pass. The coolant is dispensed onto the work rolls and / or the rolled stock exclusively on an entry side of a rolling pass.

[0008] WO 2019 / 068382 A1 discloses a rolling apparatus for rolling a rolling stock and a method for operating the rolling apparatus. The rolling apparatus has two rolling stands, each having two work rolls spaced apart from each other by a roll gap. In a first operating mode, a lubricating mixture comprising a carrier gas, a lubricant, and a coolant is applied to at least one work roll of a first rolling stand and / or to at least one rolling surface of the rolling stock. In a second operating mode, a skin-pass agent is applied to at least one work roll of the first rolling stand, at least one work roll of the second rolling stand, and / or at least one rolling surface of the rolling stock.

[0009] The invention is based on the object of enabling a uniform application of a lubricant during cold rolling of a metallic rolling stock in a rolling stand, whereby the amount of lubricant applied per unit area to the surface to be lubricated can be kept constant even with changing rolling strip speeds, without the formation of an undesirable spray mist of fine lubricant droplets.

[0010] The object is achieved according to the invention by a method having the features of claim 1 and a system having the features of claim 13.

[0011] Advantageous embodiments of the invention are the subject of the subclaims.

[0012] The invention relates to a method for applying a lubricant during cold rolling of a metallic rolling stock in a rolling stand with two work rolls spaced apart by a roll gap, wherein the rolling stock is fed to the rolling stand at a variable rolling speed and the lubricant is dispensed by a plurality of single-component nozzles, each designed as a flat jet nozzle, either onto a surface of the rolling stock or onto a surface of a work roll, wherein each single-component nozzle dispenses a quantity of lubricant in the range of 200 ml / min to 500 ml / min at a pressure in the range of 2 bar to 10 bar, preferably in the range of 2 bar to 4 bar, depending on the current rolling speed and the quantity dispensed by each single-component nozzle

[0013] The amount of lubricant is controlled as a function of the instantaneous rolling speed in such a way that the amount of lubricant discharged by the single-component nozzle per unit area onto a surface of the rolling stock or onto a surface of a work roll is essentially independent of the instantaneous rolling speed at rolling speeds within a predeterminable speed interval.

[0014] In the method according to the invention, a lubricant is dispensed onto the rolling stock and / or at least one work roll of a rolling stand using single-component nozzles. The lubricant is not mixed with another liquid or a carrier gas; i.e., the single-component nozzles dispense a pure lubricant instead of, for example, an emulsion of lubricant and another liquid or a mixture of lubricant and a carrier gas. This allows the amount of lubricant used for lubrication to be reduced and precisely metered compared to lubrication using an emulsion. Furthermore, compared to applying the lubricant with a carrier gas, the costs of generating the pressure required to atomize the lubricant in the carrier gas are eliminated.

[0015] Furthermore, according to the invention, the lubricant is dispensed from the single-component nozzles at a relatively low pressure in the range of 2 bar to 10 bar, preferably in the range of 2 bar to 4 bar. This advantageously avoids a spray mist that would arise when the lubricant is dispensed under high pressure through the single-component nozzles and would have to be separately extracted from the rolling mill. If the medium supplied to the single-component nozzles were subjected to high pressure (for example, up to several hundred bar), this would disadvantageously promote the formation of a fine spray mist on the rolling mill. By applying low pressure to the lubricant according to the invention, a spray fan is created near the nozzle opening of a single-component nozzle, forming a liquid curtain that breaks up into larger lubricant droplets with increasing distance.These larger lubricant droplets have the advantage - in contrast to the smaller lubricant droplets in dual-fluid nozzles or flat jet nozzles that are operated at high pressure - that they do not tend to form mist, so that the corresponding extraction of spray mist is not necessary.

[0016] Furthermore, the amount of lubricant dispensed by each single-component nozzle is controlled according to the invention as a function of the current rolling speed such that the amount of lubricant dispensed by the single-component nozzle per unit area onto a surface of the rolling stock or onto a surface of a work roll is essentially independent of the current rolling speed at rolling speeds within a predeterminable speed interval. This ensures uniform lubrication of the roll gap, independent of the rolling speed, within the speed interval, even with changing rolling speeds. In particular, this avoids unnecessarily high lubrication and thus unnecessary lubricant consumption at low rolling speeds within the speed interval.

[0017] In one embodiment of the invention, a rolling oil is dispensed as a lubricant from the single-component nozzles. For example, a standard rolling oil with a viscosity of approximately 60 mPa s at a temperature of 40°C is used as the lubricant.

[0018] In a further embodiment of the invention, the single-component nozzles on at least one side of the rolling stand dispense a lubricant quantity in the range of 0.8 g / m² to 2.4 g / m² either onto a surface of the rolling stock or onto a surface of a work roll. This means that the amount of lubricant used is significantly lower than, for example, with conventional lubrication using an emulsion of lubricant and another fluid.

[0019] In a further embodiment of the invention, all single-component nozzles with which the lubricant is dispensed on the same side of the rolling stand either onto one or more surfaces of the rolled stock or onto a surface of a work roll are supplied with the lubricant by means of a single frequency-controlled pump with which a lubricant quantity in the range of 0.5 l / min to 6 l / min is delivered depending on the instantaneous rolling speed when the temperature of the lubricant is 30°C. The use of a frequency-controlled pump to supply several single-component nozzles with the lubricant enables precise control of the quantity of lubricant dispensed by the single-component nozzles by means of the pump speed.

[0020] In a further embodiment of the invention, an emulsion is dispensed onto at least one surface of a work roll on at least one side of the roll stand, the emulsion consisting of the lubricant and another liquid or of another lubricant and another liquid. Preferably, the emulsion is not dispensed onto the surface of the work roll on that side of the roll stand on which the lubricant is dispensed onto the surface of a work roll using the single-fluid nozzles. The emulsion supports the lubrication of the roll gap through the lubricant in the emulsion. However, the emulsion primarily serves to cool the work rolls and the rolled stock through the additional liquid in the emulsion. The proportion of lubricant in the emulsion is, for example, 2 to 20 percent by volume.The emulsion and the pure lubricant are preferably not dispensed onto a work roll on the same side of the rolling stand, as otherwise the pure lubricant would be partially washed off the work roll by the emulsion. Preferably, the same lubricant is used for the emulsion that is also dispensed in pure form by the single-component nozzles. This has the advantage that the existing infrastructure of a rolling mill can usually be used to reuse the emulsion. In existing rolling mills, previously used emulsion is usually collected under the rolling stand, cleaned, pumped back into an emulsion tank, and reused.If the same lubricant is used for the emulsion that is also dispensed in pure form by the single-component nozzles, the used emulsion and the used pure lubricant can be collected together beneath the rolling mill, cleaned, pumped back into the emulsion tank, and reused as an emulsion. This may gradually increase the concentration of the emulsion used slightly, but this can easily be adjusted if necessary.

[0021] In a further embodiment of the invention, the rolling stand is a reversing rolling stand and the lubricant is discharged with the single-component nozzles only on the outlet side of the rolling stand and only either onto at least one surface of the rolling stock or onto at least one surface of a work roll.

[0022] In another embodiment of the invention, the rolling stand is a reversing rolling stand and the lubricant is dispensed with the single-component nozzles only on the inlet side of the rolling stand, wherein the lubricant is dispensed onto both surfaces of the rolling stock in a first rolling pass and onto only one surface of the rolling stock in each subsequent rolling pass.

[0023] In a further embodiment of the invention, the lubricant on the inlet side of the rolling stand with the single-component nozzles is only dispensed either onto at least one surface of the rolling stock or onto at least one surface of a work roll.

[0024] In a further embodiment of the invention, the lubricant on the outlet side of the rolling stand is dispensed with the single-component nozzles only either onto at least one surface of the rolling stock or onto at least one surface of a work roll.

[0025] The aforementioned embodiments of the invention take into account that, to lubricate the roll gap on one side of the rolling stand, it is generally sufficient to apply lubricant either to the rolling stock or to the work rolls. In the case of a reversing rolling stand, the rolling stock is repeatedly wound up between individual rolling passes. This means that the lubricant acts on the rolling stock for a longer period of time and thus adheres better to the rolling stock than in the case of a tandem rolling stand. Secondly, as the rolling stock is wound up, the applied lubricant is automatically distributed between adjacent windings of the rolling stock. Therefore, in the case of a reversing rolling stand, the rolling stock only needs to be lubricated on both sides on the entry side of the rolling stand before the first rolling pass, since the rolling stock fed into the rolling mill is still dry. For subsequent rolling passes, however, lubrication of the rolling stock on one side is sufficient.

[0026] In a further embodiment of the invention, the quantity of lubricant discharged by each single-component nozzle is controlled as a function of the instantaneous rolling speed in such a way that the quantity of lubricant discharged by the single-component nozzle per unit area onto a surface of the rolling stock or onto a surface of a work roll is essentially independent of the instantaneous rolling speed at rolling speeds within the speed interval and at changes in the rolling speed of up to 1 m / s 2<.

[0027] In a further embodiment of the invention, a speed of at least 600 m / min is specified as the lower limit of the speed interval and / or a speed of at most 1500 m / min is specified as the upper limit of the speed interval.

[0028] The two aforementioned embodiments of the invention take into account that, with the stated delivery and discharge quantities of lubricant by the pumps or single-component nozzles, the quantity of lubricant delivered per unit area onto the rolling stock and / or work rolls can typically be kept constant for rolling speeds between 600 m / min and 1500 m / min. At rolling speeds below 600 m / min, however, the quantity of lubricant delivered per unit area onto the rolling stock and / or work rolls by the single-component nozzles increases, since the pumps are not designed for smaller delivery quantities of lubricant. For example, the rolling speed is increased in the case of a defect in the rolling stock - e.g., a weld seam connecting two metal strips that are to be rolled one after the other in the rolling mill in question. to well below 600 m / min in order to avoid damage to the rolling stand. Therefore, due to the reduced rolling speed, zones are created on the rolling stock in front of and behind the relevant defect, which are supplied with a significantly larger quantity of lubricant. This is also tolerated within the scope of the invention. In this context, the dynamics of the pumps are essential, as they allow the amount of lubricant to be applied to be adapted to a varying rolling speed. Therefore, the pumps are designed according to the invention to be able to adapt the delivered amount of lubricant to rolling stock accelerations of up to 1 m / s 2< in such a way that the lubricant coverage is kept constant over the length of the rolling stock.

[0029] A system according to the invention for applying a lubricant during cold rolling of a metallic rolling stock in a rolling stand with two work rolls spaced from each other by a roll gap through which the rolling stock is passed at a variable rolling speed, comprises: at least one lubrication beam with several single-component nozzles, each designed as a flat jet nozzle, which are arranged equidistantly with respect to a line parallel to the axis of a work roll and are each configured to dispense lubricant either onto a surface of the rolling stock or onto a surface of a work roll, at least one frequency-controlled pump configured to supply the lubricant to at least one lubrication beam, a flow measuring unit for each pump configured to measure a quantity of lubricant delivered by the pump per unit of time, and a control unit configured to control all pumps such that each single-component nozzle dispenses a quantity of lubricant in the range of 200 ml / min to 500 ml / min at a pressure in the range of 2 bar to 10 bar depending on the current rolling speed,so that the quantity of lubricant delivered per unit area from the single-component nozzle onto a surface of the rolling stock or a surface of a work roll is essentially independent of the instantaneous rolling speed at rolling speeds within a predeterminable speed interval.

[0030] In one embodiment of the system according to the invention, each lubrication bar has a distance from the rolling stock or a work roll in the range of 0.2 m to 0.5 m.

[0031] A further embodiment of the system according to the invention comprises a heating device for heating the lubricant, which can be controlled or regulated by the control unit in such a way that the lubricant can be heated to a predeterminable operating temperature before being supplied to the lubricating bars.

[0032] A system for applying a lubricant according to the invention enables the implementation of the method according to the invention. Therefore, the advantages of such a system correspond to the above-mentioned advantages of the method according to the invention.

[0033] The above-described properties, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of exemplary embodiments, which are explained in more detail in conjunction with the drawings. FIG 1 a rolling stand for cold rolling a rolled product, FIG 2 a block diagram of an embodiment of a system for applying a lubricant, FIG 3 a first view of the arrangement and jet profiles of single-fluid nozzles of a lubricating beam, FIG 4 a second view of the arrangement and jet profiles of single-fluid nozzles of a lubricating beam.

[0034] Corresponding parts are provided with the same reference numerals in the figures.

[0035] Figure 1 (FIG 1) shows a rolling stand 1 for cold rolling a rolled stock 2. The rolled stock 2 is a metallic rolled strip whose thickness is reduced by cold rolling. The rolling stand 1 comprises a first work roll 3, a second work roll 4, a first backup roll 5 and a second backup roll 6. The work rolls 3, 4 are spaced from one another by a roll gap 7 through which the rolled stock 2 is guided in a rolling direction 8. The first work roll 3 is arranged above the second work roll 4. The first backup roll 5 is arranged above the first work roll 3 and bears against the first work roll 3. The second backup roll 6 is arranged below the second work roll 4 and bears against the second work roll 4. The rolled stock 2 has a first surface 2.1 which bears against the first work roll 3 in the roll gap 7, and a second surface 2.2 which bears against the second work roll 4 in the roll gap 7.

[0036] Furthermore, the rolling stand 1 comprises emulsion beams 9 for applying an emulsion 10 to the work rolls 3 and a system 20 for applying a lubricant 11 to the rolling stock 2 and / or to the work rolls 3, 4 according to an embodiment of the invention. The lubricant 11 is a pure rolling oil, which, for example, has a viscosity of approximately 60 mPa s at a temperature of 40°C. The emulsion 10 consists of water and the lubricant 11, with the proportion of the lubricant 11 in the emulsion 10 being in the range of 2 to 20 percent by volume.

[0037] Figure 2 (FIG 2 ) shows a block diagram of the system 20. The system 20 comprises lubrication bars 21, each with five single-fluid nozzles 23, a control unit 25, pumps 27 frequency-controlled by the control unit 25, and a flow measuring unit 29 for each pump 27.

[0038] The rolling stand 1 is a tandem rolling stand or a reversing rolling stand. In the case of the rolling stand 1 being a reversing rolling stand, four lubrication beams 21 and two emulsion beams 9 are arranged on each side of the rolling stand 1. For each work roll 3, 4, exactly one lubrication beam 21 is arranged on each side of the rolling stand 1, whose single-component nozzles 23 are configured to dispense the lubricant 11 onto the surface of the work roll 3, 4. Furthermore, for each surface 2.1, 2.2 of the rolling stock 2, exactly one lubrication beam 21 is arranged on each side of the rolling stand 1, whose single-component nozzles 23 are configured to dispense the lubricant 11 onto the surface 2.1, 2.2 of the rolling stock 2. Each emulsion beam 9 has nozzles configured to dispense the emulsion 10.For each work roll 3, 4, exactly one emulsion bar 9 is arranged on each side of the rolling stand 1, the nozzles of which are designed to discharge the emulsion 10 onto the surface of the work roll 3, 4.

[0039] If the rolling stand 1 is a tandem rolling stand, the two outlet-side lubrication beams 21, whose single-component nozzles 23 are designed to discharge the lubricant 21 onto the surface of a work roll 3, 4, as well as the associated pump 27 and the associated flow measuring unit 29, are omitted. The omitted lubrication beams 21, the omitted pump 27 and the omitted flow measuring unit 29 are shown in the Figures 1 and 2 each surrounded by a dashed frame 30.

[0040] Each single-component nozzle 23 is designed as a flat jet nozzle, i.e., the lubricant jet emitted by a single-component nozzle 23 is essentially concentrated on one plane or has only a small extent perpendicular to the plane. The single-component nozzles 23 of each lubrication beam 11 are arranged equidistantly with respect to a line parallel to the axis A of a work roll 3, 4, around which the work roll 3, 4 rotates during operation of the rolling stand 1. For example, the inner diameter of each flat jet nozzle 23 has a diameter of approximately 0.3 mm at its narrowest point, and the cross-section of the nozzle opening at the nozzle outlet of each single-component nozzle 23 is designed, for example, such that the flow rate of lubricant 11 emitted through the nozzle opening corresponds to the flow rate of a nozzle that has a circular nozzle opening with a diameter of 0.6 mm and is otherwise designed like the single-component nozzle 23.

[0041] Figure 3 (FIG 3 ) and Figure 4 (FIG 4 ) show schematically the geometric arrangement of the single-component nozzles 23 of a lubricating beam 21 and the jet profiles of the lubricant jets emitted by the single-component nozzles 23 using the example of the lubricating beam 21 which is arranged on the inlet side of the rolling stand 1 and whose single-component nozzles 23 emit the lubricant 11 onto the surface of the first work roll 3. Figure 3 shows the single-component nozzles 23 and their jet profiles in a plane which is perpendicular to the z-axis of a Cartesian coordinate system with coordinates x, y, z, wherein the x-direction corresponds to the rolling direction 8 and the y-direction runs parallel to the axis A of the work roll 3. Figure 4 shows the single-component nozzles 23 and their jet profiles in a plane perpendicular to the x-axis of this coordinate system. The x-direction of the coordinate system is the main discharge direction of the lubricant 11 through the single-component nozzles 23.

[0042] Each single-component nozzle 23 discharges the lubricant 11 as a flat jet 31, which is essentially concentrated in a plane whose plane normal forms a small, non-zero angle α with the z-direction in the yz-plane and which has an opening angle β. The angle α advantageously prevents two flat jets 31 from simultaneously hitting the same area of ​​the surface of the work roll 3 and influencing each other. The distance c between two adjacent single-component nozzles 23 and the distance a of the single-component nozzles 23 from the surface of the work roll 3 are selected such that an extension b of each flat jet 31 in the y-direction upon impact of the flat jet 31 on the surface of the work roll 3 is approximately twice as large as the distance c.This advantageously ensures that the flat jets 31 apply the lubricant 11 evenly distributed over the surface of the work roll 3, because a flat jet 31 generally has a higher density of the lubricant 11 in its central region than in its edge regions.

[0043] The distance c between two adjacent single-component nozzles 23 is, for example, approximately 320 mm. The distance a of the single-component nozzles 23 from the surface of the work roll 3 is, for example, in the range of 200 mm to 500 mm and is preferably 325 mm. The angle α is, for example, in the range of 2 degrees to 5 degrees. The opening angle β is, for example, in the range of 60 degrees to 120 degrees.

[0044] Each pump 27 is configured to supply the lubricant 11 to exactly two lubrication beams 21, wherein these two lubrication beams 21 are configured to discharge the lubricant 11 on the same side of the rolling stand 1 either onto the surface of a work roll 3, 4 or onto a surface 2.1, 2.2 of the rolling stock 2. Furthermore, each pump 27 has a speed range of, for example, 200 rpm to 2300 rpm and a power requirement of up to approximately 1 kW, and is configured to deliver a lubricant quantity of 0.5 l / min to 6 l / min when the temperature of the lubricant 11 is 30°C.

[0045] Each flow measuring unit 29 is configured to measure a quantity of lubricant delivered by the pump 27 assigned to it per unit of time.

[0046] The pumps 27 are configured to pump the lubricant 11 from a lubricant reservoir 13. A heating device 15 is configured to heat the lubricant 11 in the lubricant reservoir 13 to a predeterminable operating temperature, which is, for example, at least 30°C.

[0047] The control unit 25 is configured to control the respectively active pumps 27 such that a quantity of lubricant 11 in the range from 200 ml / min to 500 ml / min is dispensed from the single-component nozzles 23 of these pumps 27, and thus a quantity of lubricant in the range from 1 l / min to 2.5 l / min is dispensed from an active lubrication bar 21, at a pressure in the range from 2 bar to 10 bar, depending on the instantaneous rolling speed. Thus, the quantity of lubricant dispensed per unit area by the single-component nozzle 23 onto a surface 2.1, 2.2 of the rolling stock 2 or a work roll 3, 4 is essentially independent of the instantaneous rolling speed at rolling speeds within a predeterminable speed interval. For example, a speed of at least 600 m / min is specified as the lower limit of the speed interval, and a speed of at most 1500 m / min is specified as the upper limit of the speed interval.

[0048] Furthermore, the control unit 25 is configured to regulate the quantity of lubricant dispensed by each single-component nozzle 23 as a function of the instantaneous rolling speed such that the quantity of lubricant dispensed by the single-component nozzle 23 per unit area onto a surface 2.1, 2.2 of the rolling stock 2 or onto the surface of a work roll 3, 4 is substantially independent of the instantaneous rolling speed at rolling speeds within the speed interval and at changes in the rolling speeds up to 1 m / s 2<.

[0049] In addition, the control unit 25 is configured to control or regulate the heating device 15 such that the lubricant 11 in the lubricant reservoir 13 is heated to the operating temperature.

[0050] If the rolling stand 1 is a tandem rolling stand, the lubrication beams 21 and emulsion beams 9 are used in the operation of the rolling stand 1, for example, according to one of the following possibilities: A) The inlet-side lubrication bars 21 for the rolling stock 2 are active, the outlet-side lubrication bars 21 for the rolling stock 2 are optionally active (i.e., active or inactive), the lubrication bars 21 for the work rolls 3, 4 are inactive, the inlet-side emulsion bars 9 are optionally active, and the outlet-side emulsion bars 9 are active. B) The inlet-side lubrication bars 21 for the rolling stock 2 are inactive, the outlet-side lubrication bars 21 for the rolling stock 2 are optionally active, the lubrication bars 21 for the work rolls 3, 4 are active, the inlet-side emulsion bars 9 are inactive, and the outlet-side emulsion bars 9 are active.

[0051] In both variants A) and B), the outlet-side lubrication bar 21 for the first surface 2.1 of the rolling stock 2 is preferably only activated if a device (for example a blower, a scraper or a squeeze roller) is present for removing the emulsion 10 remaining on this surface 2.1.

[0052] Variant A) can be modified such that instead of the inlet-side lubrication bars 21 for both surfaces 2.1 and 2.2, only the inlet-side lubrication bar 21 is active for one of the two surfaces 2.1 or 2.2, and / or that only the outlet-side lubrication bar 21 is optionally active for one of the two surfaces 2.1 or 2.2, while the outlet-side lubrication bar 21 is inactive for the other of the two surfaces 2.1 or 2.2.

[0053] Variant B) can be modified such that instead of the lubrication bars 21 for both work rolls 3, 4, only the lubrication bar 21 for one work roll 3 or 4 is active, and / or that only the outlet-side lubrication bar 21 for one of the two surfaces 2.1 or 2.2 is optionally active, while the outlet-side lubrication bar 21 for the other of the two surfaces 2.1 or 2.2 is inactive.

[0054] If the rolling stand 1 is a reversing rolling stand, the rolling direction 8 and thus the entry side and the exit side of the rolling stand 1 change after each rolling pass and the lubrication beams 21 and emulsion beams 9 are used during the operation of the rolling stand 1 during a rolling pass, for example, according to variant A) above or one of the following possibilities: C) The inlet-side lubrication bars 21 for rolling stock 2 are inactive, the inlet-side lubrication bars 21 for work rolls 3, 4 are active, the outlet-side lubrication bars 21 for rolling stock 2 are optionally active, the outlet-side lubrication bars 21 for work rolls 3, 4 are inactive, the inlet-side emulsion bars 9 are inactive, and the outlet-side emulsion bars 9 are active. D) The inlet-side lubrication bars 21 are inactive, the outlet-side lubrication bars 21 for rolling stock 2 are active, the outlet-side lubrication bars 21 for work rolls 3, 4 are optionally active, the inlet-side emulsion bars 9 are active, and the outlet-side emulsion bars 9 are inactive. E) The lubricant 11 is applied in a first rolling pass on the inlet side to both surfaces 2.1 and 2.2 of the rolling stock 2 and in each subsequent rolling pass only to one surface 2.1 or 2.2 of the rolling stock 2.For example, the lubrication bars 21 for the work rolls 3, 4 are inactive, while the emulsion bars 9 are active.

[0055] Analogous to the above-mentioned modifications of variants A) and B) for a tandem rolling stand, variants A), C) and D) for a reversing rolling stand can also be modified in such a way that only lubrication bars 21 are active for a surface 2.1 or 2.2 of the rolling stock 2 and / or the surface of a work roll 3 or 4.

[0056] Regarding the method on a reversing rolling mill, it should be noted that, due to the repeated winding of the rolling stock 2 between the individual rolling passes, this has the advantage, compared to a tandem rolling mill, of a longer exposure time of the lubricant 11 to the rolling stock 2 (and thus better adhesion of the lubricant 11 to the rolling stock 2). In variant E), the rolling stock 2 is lubricated with the lubricant 11 on both sides on the entry side of the rolling stand 1 before the first rolling pass, since the rolling stock 2 is generally completely dry when it arrives at the rolling stand 1 from a preceding pickling plant. For the subsequent rolling passes, one-sided lubrication of the rolling stock 2 is sufficient because, during winding of the rolling stock 2, the applied lubricant 11 is automatically distributed between adjacent windings of the rolling stock 2.In this context, it should also be noted that the rolling stock 2 is 80% to 90% shorter before the first rolling pass than after the rolling process, so that less lubricant 11 is required for double-sided lubrication of the rolling stock 2 before the first rolling pass than would be required for double-sided lubrication of the rolling stock 2 in later rolling passes.

[0057] The Figures 1 to 4 The described embodiment of a system 20 for applying the lubricant 11 can be modified in various ways. In particular, a lubrication beam 21 can have a different number (other than five) of single-component nozzles 23. Furthermore, a lubrication beam 21 can be omitted, which is never activated during operation of the rolling stand 1 according to one of the variants A) to E) described above or their modifications. The same applies to the emulsion beams 9.

[0058] Although the invention has been illustrated and described in detail by means of preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention. List of reference symbols

[0059] 1Roll stand 2Rolling stock 2.1, 2.2Surface 3, 4Work roll 5, 6Back-up roll 7Roll gap 8Rolling direction 9Emulsion beam 10Emulsion 11Lubricant 13Lubricant reservoir 15Heating device 20Lubricant application system 21Lubrication beam 23Single-component nozzle 25Control unit 27Pump 29Flow measurement unit 30Frame 31Flat jet Axis a, cDistance bExtension αAngle βOpening angle x, y, zCartesian coordinate

Claims

1. A method for applying a lubricant (11) during cold rolling of a metallic rolling stock (2) in a rolling stand (1) with two work rolls (3, 4) spaced apart from one another by a roll gap (7), wherein - the rolling stock (2) is fed to the rolling stand (1) at a variable rolling speed and - the lubricant (11) is sprayed onto a surface (2.1, 2.2) by means of a plurality of single-component nozzles (23), each designed as a flat jet nozzle,2) of the rolling stock (2) or onto a surface of a work roll (3, 4), wherein - a quantity of lubricant (11) in the range from 200 ml / min to 500 ml / min is dispensed from each single-component nozzle (23) at a pressure in the range from 2 bar to 10 bar depending on the instantaneous rolling speed - and the quantity of lubricant dispensed from each single-component nozzle (23) is regulated depending on the instantaneous rolling speed in such a way that the quantity of lubricant dispensed by the single-component nozzle (23) per unit area onto a surface (2.1, 2.2) of the rolling stock (2) or onto a surface of a work roll (3, 4) is substantially independent of the instantaneous rolling speed at rolling speeds within a predeterminable speed interval.

2. Method according to claim 1, wherein a rolling oil is dispensed from the single-component nozzles (23) as the lubricant (11).

3. Method according to one of the preceding claims, wherein with the single-component nozzles (23) on at least one side of the rolling stand (1) a lubricant quantity in the range of 0.8 g / m 2 up to 2.4 g / m 2 either onto a surface (2.1, 2.2) of the rolling stock (2) or onto a surface of a work roll (3, 4).

4. Method according to one of the preceding claims, wherein all single-substance nozzles (23) with which the lubricant (11) is dispensed on the same side of the rolling stand (1) either onto one or more surfaces (2.1, 2.2) of the rolling stock (2) or onto a surface of a work roll (3, 4), the lubricant (11) is supplied by means of a single frequency-controlled pump (27) with which a quantity of lubricant in the range from 0.5 l / min to 6 l / min is conveyed depending on the instantaneous rolling speed when the temperature of the lubricant (11) is 30°C.

5. Method according to one of the preceding claims, wherein on at least one side of the rolling stand (1) an emulsion (10) is dispensed onto at least one surface of a work roll (3, 4), wherein the emulsion (10) consists of a further liquid and another lubricant or preferably the lubricant (11).

6. The method according to claim 5, wherein the emulsion (10) is not dispensed onto the surface of the work roll (3, 4) on that side of the rolling stand (1) on which the lubricant (11) is dispensed onto the surface of a work roll (3, 4) by means of the single-component nozzles (23).

7. Method according to one of the preceding claims, wherein the rolling stand (1) is a reversing rolling stand and the lubricant (11) is dispensed with the single-component nozzles (23) only on the outlet side of the rolling stand (1) and only either onto at least one surface (2.1, 2.2) of the rolling stock (2) or onto at least one surface of a work roll (3, 4).

8. Method according to one of claims 1 to 6, wherein the rolling stand (1) is a reversing rolling stand and the lubricant (11) is dispensed with the single-component nozzles (23) only on the inlet side of the rolling stand (1), wherein the lubricant (11) is dispensed in a first rolling pass onto both surfaces (2.1, 2.2) of the rolling stock (2) and in each further rolling pass only onto one surface (2.1, 2.2) of the rolling stock (2).

9. Method according to one of claims 1 to 6, wherein the lubricant (11) on the inlet side of the rolling stand (1) is dispensed with the single-component nozzles (23) only either onto at least one surface (2.1, 2.2) of the rolling stock (2) or onto at least one surface of a work roll (3, 4).

10. Method according to one of claims 1 to 6 or 9, wherein the lubricant (11) on the outlet side of the rolling stand (1) is dispensed with the single-component nozzles (23) only either onto at least one surface (2.1, 2.2) of the rolling stock (2) or onto at least one surface of a work roll (3, 4).

11. Method according to one of the preceding claims, wherein the quantity of lubricant dispensed by each single-component nozzle (23) is controlled as a function of the instantaneous rolling speed in such a way that the quantity of lubricant dispensed by the single-component nozzle (23) per unit area onto a surface (2.1, 2.2) of the rolling stock (2) or onto a surface of a work roll (3, 4) at rolling speeds within the speed interval and at changes in the rolling speed up to 1 m / s 2 is essentially independent of the current rolling speed.

12. Method according to one of the preceding claims, wherein a speed of at least 600 m / min is specified as the lower limit of the speed interval and / or a speed of at most 1500 m / min is specified as the upper limit of the speed interval.

13. System (20) for applying a lubricant (11) during cold rolling of a metallic rolling stock (2) in a rolling stand (1) with two work rolls (3, 4) which are spaced apart from one another by a roll gap (7) through which the rolling stock (2) is guided at a variable rolling speed, the system comprising: - at least one lubricating bar (21) with a plurality of single-component nozzles (23), each designed as a flat jet nozzle, which are arranged equidistantly with respect to a line parallel to the axis of a work roll (3, 4) and are each designed to apply lubricant (11) either onto a surface (2.1, 2.2) of the rolling stock (2) or onto a surface of a work roll (3, 4), - at least one frequency-controlled pump (27) which is designed to supply the lubricant (11) to at least one lubricating bar (21), - a flow measuring unit (29) for each pump (27) which is designed to record a quantity of lubricant delivered by the pump (27) per unit of time, and - a control unit (25) which is designed to control all pumps (27) in such a way that a quantity of lubricant (11) in the range from 200 ml / min to 500 ml / min is delivered from each single-substance nozzle (23) at a pressure in the range from 2 bar to 10 bar depending on the current rolling speed, so that the quantity of lubricant delivered per unit area by the single-substance nozzle (23) onto a surface (2.1, 2.2) of the rolling stock (2) or a surface of a work roll (3, 4) is substantially independent of the instantaneous rolling speed at rolling speeds within a predeterminable speed interval.

14. System (20) according to claim 13, wherein each lubrication bar (21) has a distance from the rolling stock (2) or a work roll (3, 4) in the range of 0.2 m to 0.5 m.

15. System (20) according to claim 13 or 14, further comprising a heating device (15) for heating the lubricant (11), which can be controlled or regulated by the control unit (25) such that the lubricant (11) can be heated to a predeterminable operating temperature before being supplied to the lubricating bars (21).

Images