Method and device for rolling stock and use of a cooling lubricant

Abstract

A method for rolling rolling stock, wherein a water-based cooling lubricant is applied to the rolling stock and/or to at least one roller which forms a roll gap, at least one water-soluble and tribologically active additive being added to the water-based cooling lubricant prior to application to the rolling stock and/or to the at least one roller.

Claims

1. A method for rolling of rolling stock (1), comprising the steps of: applying a water-based cooling lubricant to the rolling stock (1) and/or to at least one roll of a pair of rolls (20, 22, 30, 32) forming a roll gap (200, 300); adding at least one water-soluble, tribologically active additive to the water-based cooling lubricant before the water-based cooling lubricant is applied to the rolling stock and/or to the at least one roll; collecting excess cooling lubricant after application to the rolling stock (1) and/or to the at least one roll (20, 22, 30, 32) whereupon the excess cooling lubricant is used again for application to the rolling stock (1) and/or to the at least one roll (20, 22, 30, 32); continuously filtering the excess cooling lubricant after the excess cooling lubricant has been applied but before the excess cooling lubricant is reapplied so as to filter material abraded from the rolls in a section of a particle spectrum in which a largest lengthwise dimension of a single particle is less than 5 m; determining with a sensor an accumulation of the water-soluble additive on the rolling stock (1) and/or on the at least one roll (20, 22, 30, 32) resulting from evaporation of a portion of the water-based lubricant; and adding additional of the water-soluble additive to the filtered excess-cooling lubricant based on the accumulation of the water-soluble additive on the rolling stock and/or on the at least one roll before the excess-cooling lubricant is used again for application to the rolling stock and/or to the at least-one roll.

2. A method according to claim 1, wherein the at least one water-soluble, tribologically active additive is selected to suit an individual rolling situation.

3. A method according to claim 1, wherein the water-based cooling lubricant together with the water-soluble, tribologically active additive is applied to the rolling stock (1) and/or to the rolls (20, 22, 30, 32) forming the roll gap (200, 300) as a function of a rolling situation.

4. A method according to claim 1, wherein, before the filtered cooling lubricant is applied again to the rolling stock (1) and/or to the roll (20, 33, 30, 32), the at least one water-soluble, tribologically active additive is re-added to reestablish a desired additive concentration in the cooling lubricant.

5. A method according to claim 1, wherein the accumulation of the additive on the rolling stock (1) and/or on the at least one roll (20, 22, 30, 32) is determined via an evaluation of measured rolling process data under inclusion of a suitable tribological rolling gap model, and the addition of the water-soluble, tribologically active additive is controlled so that a desired additive accumulation is achieved.

6. A method according to claim 1, wherein an additive accumulation on the rolling stock (1) leaving the roll gap (200, 300) is determined based on an additive layer remaining on the rolling stock (1), and the addition of the water-soluble, tribologically active additive is controlled accordingly in an open-loop or closed-loop manner.

7. A method according to claim 1, wherein a metered addition of the water-soluble, tribologically active additive is controlled in an open-loop or closed-loop manner based on a continuous measurement of abraded roll particles in the collected cooling lubricant.

8. A method according to claim 1, wherein an amount of water-soluble, tribologically active additive added to the cooling lubricant applied to a top of the rolling stock (1) and/or to an upper roll (20) is different from an amount added to the cooling lubricant applied to a bottom of the rolling stock (1) and/or to a lower roll (22).

9. A method according to claim 1, wherein an amount of water-soluble, tribologically active additive added is varied over time.

10. A method according to claim 1, wherein at least one additional water-soluble additive is metered into the cooling lubricant.

11. A device for rolling of rolling stock (1), comprising: rolls (20, 22, 30, 32) that form a roll gap (200, 300); apparatus arranged to apply a water-based cooling lubricant to the rolling stock (1) and/or to at least one of the rolls (20, 22, 30, 32) forming the roll gap a device for adding a water-soluble, tribologically active additive to the water-based cooling lubricant; at least one filter device (8) for continuous filtration of collected cooling lubricant, the filter device being configured to filter material abraded from the rolls in a section of a particle spectrum in which a largest lengthwise dimension of a single particle is less than 5 m; and, a device arranged to determine an accumulation of the water-soluble additive on the rolling stock and/or on at least one of the rolls resulting from evaporation of a portion of the water-based lubricant; wherein the device for adding the water-soluble additive adds additional of the water-soluble additive to the filtered excess-cooling lubricant based on the accumulation of the water-soluble additive on the rolling stock and/or on the at least one roll before the excess-cooling lubricant is used again for application to the rolling stock and/or to the at least one roll.

12. A device according to claim 11, further comprising a metering device (6) for adding the water-soluble, tribologically active additive to the cooling lubricant under open-loop or closed-loop control.

13. A method according to claim 2, wherein the additive is selected to suit a material of the rolling stock and/or desired tribological conditions in the roll gap.

14. A method according to claim 3, wherein the water-based cooling lubricant together with the water-soluble, tribologically active additive is applied by adjusting application conditions.

15. A method according to claim 14, wherein the water-based cooling lubricant together with the water-soluble, tribologically active additive is applied by changing entrance temperature, application pressure, manner of application, and location of application.

16. A method according to claim 4, wherein the at least one water-soluble, tribologically active additive is re-added based on a determination of a depletion of the additive.

17. A method according to claim 16, wherein the depletion is determined by a continuous measurement of relative permittivity and/or specific electrical conductivity of the cooling lubricant.

18. A method according to claim 7, wherein the metered addition of the water-soluble, tribologically active additive is controlled using a database for comparison, which database contains data on the roll material, roughness of the rolls, type of roll, the rolling stock, an alloy, a reduction-per-pass plan, and a suitable tribological process model.

19. A method according to claim 10, wherein the at least one additional water-soluble additive is metered into the cooling lubricant to balance an action of the cooling lubricant between a washing effect and a lubricating effect.

20. A method according to claim 10, wherein the at least one additional water-soluble additive is metered into the cooling lubricant as a function of a desired surface appearance.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Preferred additional embodiments and aspects of the present invention are explained in greater detail by the following description of the FIGURE:

(2) FIG. 1 shows a schematic diagram of a cold-rolling mill from the side.

DETAILED DESCRIPTION OF THE INVENTION

(3) In the following, preferred exemplary embodiments are described on the basis of the figures. The same or similar elements or elements which function in the same way are designated by the same reference numbers, and in some cases these elements are not described again in order to avoid redundancy in the description.

(4) The rolling stock 1 passes through two schematically illustrated rolling stands 2, 3, each of which comprises an upper roll 20, 30 and a lower roll 22, 32, each of which is supported by a back-up roll 24, 34, 26, 36. Between the upper and lower rolls 20, 22, 30, 32, the roll gap 200, 300 itself is formed, where the rolling stock 1 is formed.

(5) The illustrated design of the rolling stands and the arrangement of the rolls is to be understood as being merely schematic, and any other arrangement of rolls of the individual rolling stands suitable for the rolling situation in question is also possible.

(6) The rolling stand 2 coming first in the rolling direction thus performs the first pass, whereupon the following rolling stands 3, etc., perform the subsequent passes.

(7) The cooling lubricant is applied to the rolling stock 1 before it enters the roll gap 200, 300 of the rolling stand 2, 3 in question. The cooling lubricant is applied to the rolling stock 1 in each case by means of spray bars 4, which extend transversely across the rolling stock 1, onto the top surface of the rolling stock 1. The individual spray bars 4 are supplied with the cooling lubricant through feed lines 40 for the cooling lubricant proceeding from a cooling lubricant reservoir 42.

(8) In a lower area underneath the stock 1, spray bars 5 are also provided, which are also supplied through feed lines 50 for the cooling lubricant proceeding from a cooling lubricant reservoir 52 and which are designed to apply the cooling lubricant to the rolling stock 1.

(9) The cooling lubricant can also be applied directly to the rolls 20, 22 which come in contact with the rolling stock 1. A corresponding device for this purpose is indicated schematically in FIG. 1 in the form of the spray bars 44, 54, which are arranged appropriately in front of the roll gap 200, extending across the rolls 20, 22.

(10) Underneath the rolling stands 2, 3 and/or underneath the spray bars 4, 44, 5, 54, collecting tanks 28, 38 can be provided, which collect the excess cooling lubricant dripping back down from the rolling stock 1 and/or from the rolls 20, 22. By means of the collecting tanks 28, 38, it is possible to collect the excess cooling lubricant again and then to return it to the cooling lubricant circuit. In this way, the cooling lubricant can be recycled, and thus the rolling process can be conducted more efficiently.

(11) In FIG. 1, the supply of cooling lubricant to the upper cooling bar 4 is separate from the supply to the lower cooling bar 5, so that it is possible to apply the cooling lubricant in an asymmetric manner, meaning that it is possible to obtain a rolled strip 1 with a surface appearance on the top different from that on the bottom.

(12) Water-soluble, tribologically active additives of different properties, as shown schematically by the metering device 6, can be added in variable amounts to the cooling lubricant.

(13) The metering device 6 for adding water-soluble additives to the cooling lubricant, which is applied via the cooling bars 4, 5, makes it possible to make precise adjustments to the properties of the cooling lubricant which is applied to the rolling stock 1 and/or to the rolls coming in contact with the stock.

(14) For example, the desired tribological properties in the roll gap can be achieved by means of a carefully calibrated addition of water-soluble, tribologically active additives to the water-based cooling lubricant. Through appropriate adjustment of the addition of the water-soluble, tribologically active additives, furthermore, it is possible, for example, to achieve a balance between a desired washing effect and a desired lubricating effect of the cooling lubricant, depending on the desired surface appearance and on the desired thickness reduction to be obtained during the production of the rolled strip from the rolling stock 1.

(15) In addition, the rolling process data originating from the monitoring and analysis of the roll gap under inclusion of a suitable tribological process model can be used to control the composition of the additives in the cooling lubricant.

(16) By the use of sensors 70, indicated here schematically, the additive accumulation present on the strip rolled from the rolling stock 1 behind the roll gap 200 can be measured after the rolling strip has passed through the roll gap 200. This parameter, too, can be taken into account when adjusting the addition of the water-soluble, tribologically active additives. In corresponding fashion, the mixture of the water-soluble, tribologically active additives in question is adjusted by the metering device 6.

(17) By means of electrical conductivity sensors or sensors which measure the relative permittivity of the cooling lubricant, such as by means of the sensor 72, indicated schematically by way of example, the depletion of individual additives in the cooling lubricant circuit can be determined, and an addition of the depleted water-soluble additive can be actuated correspondingly.

(18) In another advantageous embodiment, the abraded roll particles can be measured by the sensor 74, also indicated schematically, and the rolling process can be monitored by means of a particle measurement under comparative use of a database containing data on the roll material, the roll surface, the rolling stock being rolled, the alloy, the rolling conditions, and a suitable process model, on the basis of which a corresponding characteristic abrasion diagram can be created. The metered addition of the water-soluble additive by means of the metering device 6 can thus also be controlled in this way.

(19) The return stream of circulating cooling lubricant via the two collecting tanks 28, 38, shown schematically by way of example, passes first through the corresponding sensors 72, 74 and is then subjected to ultrafine filtration in the filter 8. The filtering device 8 which is used preferably provides an ultrafine filtration of such a kind that even particles with a size of less than 5 m are removed from the collected lubricant, so that the lubricant can be added back to the circuit of the cooling lubricant without loss of quality with respect to the forming of the rolling stock 1.

(20) Because one spray bar 4 is arranged above the strip and another spray bar 5 is arranged below it, it is possible to spray the additive asymmetrically onto the top and bottom of the strip 1, as a result of which different surface appearances can be produced.

(21) The provision of the metering device 6 also makes it possible to apply the water-soluble, tribologically active additive selectively and in time-variable fashion to the rolling stock. Thus a flexible rolling schedule can be followed, and customized products with variable properties of the rolling stock with respect to width, length, and time can be manufactured. For example, it is possible in this way to vary the thickness of the strip, its surface appearance, roughness, wettability, and coatability.

(22) The cooling lubricants which are used are formulated accordingly as water-based cooling lubricants, which, by means of water-based additives comprising viscosity increasers in particular, which provide for adequate hydrodynamic lubricating film formation, good cooling properties, and the necessary ultrafine filterability even in the range of less than 5 m, and simultaneously guarantee stability against the biodegradation of the cooling lubricant. The tribological conditions in the roll gap appropriate to the corresponding rolling task can thus be achieved through the addition of the water-soluble, tribologically active additives to the water-based cooling lubricant.

(23) The viscosity can be adjusted by the use of viscosity increasers, the addition of which is adjusted to fall within a range suitable for typical rolling jobs. This measure also offers the advantage over the use of rolling oils that the high viscosities required for certain applications such as the high-speed rolling of aluminum can be achieved, which is impossible with the use of the cooling lubricants in conventional use today.

(24) The interface friction in the roll gap is achieved by the accumulation of special water-soluble, tribologically active additives (selected for their suitability for the forming process by the rolls) on the roll surface and/or on the rolling stock, especially on the strip 1. In corresponding fashion, the water-soluble, tribologically active additives are adjusted to suit the rolling job, that is, in particular to suit the material and the rolling conditions in the roll gap; and the additive accumulation on the rolls, the roll surfaces, and the strip can be varied by adjusting and/or changing of the associated application conditions, such as by changing or adjusting the entrance temperature, the application pressure, and the manner in which, and the location where, the cooling lubricant is applied.

(25) Water-based cooling lubricants with viscosity increasers are known from, for example, the area of metal machining.

(26) Insofar as applicable, all individual features which are described in the individual exemplary embodiments can be combined with each other and/or exchanged without exceeding the scope of the invention.

LIST OF REFERENCE NUMBERS

(27) 1 rolling stock 2 rolling stand 20 upper roll 22 lower roll 24, 26 back-up rolls 28 collecting tank for excess cooling lubricant 200 roll gap 3 rolling stand 30 upper roll 32 lower roll 34, 36 back-up rolls 38 collecting tank for excess cooling lubricant 300 roll gap 4 upper spray bar for the rolling stock 40 feed line for cooling lubricant 42 upper cooling lubricant reservoir 44 spray bar for the upper roll 5 lower spray bar for the rolling stock 50 feed line for cooling lubricant 52 lower cooling lubricant reservoir 54 spray bar for the lower roll 6 metering device for one or more water-soluble, tribologically active additives 70 sensor for additive accumulation 72 sensor for measuring electrical conductivity 74 sensor for abraded roll particles 8 filter device W rolling direction