Method for rolling a product to be rolled

Abstract

A method for rolling a product to be rolled (3), wherein the product (3) is fed through a rolling gap (11) between two working rollers (9, 10) of a roll stand (1) and a cooling lubricant is introduced into a contact zone (15, 16), in which a contact surface (17, 18) of the product to be rolled (3) lies against a working roller (9, 10), in order to lubricate the contact zone (15, 16). Furthermore, a lubrication demand of the contact zone (15, 16) is determined in accordance with at least one process parameter of the rolling process and an additional lubricant is applied to the contact surface (17, 18) of the product to be rolled (3) before the rolling gap (11) at a specified application distance (D) if a cooling lubricant amount (C) presently introduced into the contact zone (15, 16) does not cover the lubrication demand. The application distance (D) is sized such that adhesion of the additional lubricant to the contact surface (17, 18) is increased and the lubricating effect in the contact zone (15, 16) is improved in comparison with application immediately before the rolling gap (11). In addition, the lubricant amount (C) introduced into the contact zone (15, 16) is reduced if additional lubricant is applied to the contact surface (17, 18).

Claims

1. A method for rolling a rollable material, comprising: rolling the rollable material in a rolling direction and guiding the rollable material through a rolling gap between two working rollers of a roll stand; in a contact zone, in which a contact surface of the rollable material contacts at least one of the working rollers, introducing a cooling lubricant for lubricating the contact zone on the rollable material then at the contact zone; determining a lubrication requirement of the contact zone, wherein the lubrication requirement depends on at least one process parameter of the rolling method; using at least one of a group consisting of a rollable material speed of the rollable material, a compressive strength of the rollable material, a roughness of the rollable material, a relative speed between the contact surface of the rollable material at a reference location and the surface of the working roller, a thickness of the rollable material, and a viscosity of the cooling lubricant as the at least one of the process parameters for determining the lubrication requirement; setting a quantity of an additive lubricant applied to the contact surface of the rollable material wherein the quantity of the additive lubricant depends on the lubrication requirement determined for the contact zone; applying the quantity of the additive lubricant to the contact surface of the rollable material ahead of the rolling gap in the rolling direction at a predefined application spacing from the rolling gap only when a quantity of the cooling lubricant that is currently introduced into the contact zone does not cover the lubrication requirement, and an application spacing ahead of the rolling gap is dimensioned such that an adhesion of the additive lubricant on the contact surface is increased; and reducing the quantity of the cooling lubricant introduced into the contact zone when additive lubricant is applied to the contact surface.

2. The method as claimed in claim 1, further comprising setting the cooling lubricant quantity introduced into the contact zone to depend on the at least one process parameter of the rolling process.

3. The method as claimed in claim 1, wherein a pure lubricant is used as the additive lubricant.

4. The method as claimed in claim 1, wherein the additive lubricant comprises a lubricant emulsion which has a higher lubricant proportion than the cooling lubricant.

5. The method as claimed in claim 1, wherein the step of applying the additive lubricant to the rollable material comprises spraying the additive lubricant.

6. The method as claimed in claim 1, wherein the step of applying the additive lubricant to the contact surface of the rollable material comprises uniformly supplying the additive lubricant to the contact surface across an entire rollable material width of the rollable material.

7. The method as claimed in claim 1, wherein the step of applying the additive lubricant to the rollable material comprises using an additional lubricating device which is independent of the introducing of the cooling lubricant for introducing the cooling lubricant into the contact zone.

8. The method as claimed in claim 1, wherein the step of determining the lubrication requirement of the contact zone occurs prior to the start of the step of rolling or during performance of the method of rolling.

9. The method as claimed in claim 1, wherein the determining of the lubrication requirement of the contact zone comprises using a Stribeck diagram for a coefficient of friction of the friction between the contact surface and the working roller in the contact zone to depend on at least one process parameter.

10. The method as claimed in claim 1, wherein the rollable material has two mutually opposite contact surfaces, and wherein the additive lubricant is applied to the two mutually opposite contact surfaces of the rollable material.

11. The method as claimed in claim 10, wherein the step of applying the additive lubricant comprises applying mutually dissimilar additive lubricant quantities to the two contact surfaces of the rollable material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a block diagram of a roll stand, of a cooling lubricating device, and of an additional lubricating device;

(2) FIG. 2 shows temporal profiles of a rollable material speed, of a cooling lubricant quantity, and of an additive lubricant quantity; and

(3) FIG. 3 schematically shows a rolling line of a rolling mill.

DESCRIPTION OF AN EMBODIMENT

(4) Equivalent parts are provided with the same reference signs in the figures.

(5) FIG. 1 shows a block diagram of a roll stand 1 for rolling a rollable material 3, a cooling lubricating device 5 and an additional lubricating device 7. The rollable material 3 is a metallic rolled strip, for example a steel strip, and the thickness of the strip is reduced by the rolling.

(6) The roll stand 1 has two working rollers 9, 10 which are disposed one on top of the other and which are mutually spaced apart by a rolling gap 11. In order for the rollable material 3 to be rolled, the working rollers 9, 10 are set in rotation, and the rollable material 3 is drawn by the rotating working roles 9, in a rolling direction 13 through the rolling gap 11. In the region of the rolling gap 11, the rollable material 3 herein is in contact with the working rollers 9, 10 in two contact zones 15, 16, wherein an upper contact surface 17 of the rollable material 3 contacts the upper working roller 9 in a first contact zone 15, and a lower contact surface 18 of the rollable material 3 contacts the lower working roller 10 in a second contact zone 16.

(7) A cooling lubricant is introduced into the contact zones 15, 16 by way of the cooling lubricating device 5. The cooling lubricant is a cooling lubricant emulsion which is composed of a cooling liquid and a lubricant, for example of water as the cooling liquid and oil as the lubricant, as well as potentially of emulsifiers. The main component of the cooling lubricant emulsion herein is the cooling liquid, while the lubricant proportion of the cooling lubricant is only a few percent, for example two to three percent.

(8) The cooling lubricating device 5 comprises a cooling lubricant pump 19, at least one cooling lubricant spray beam 21 for each working roller 9, 10, cooling lubricant lines 23, and a cooling lubrication controller 25. Each cooling lubricant spray beam 21 comprises cooling lubricant nozzles for dispensing cooling lubricant to the respective working roller 9, 10. The cooling lubricant is pumped by the cooling lubricant pump 19 through the cooling lubricant lines 23 to the cooling lubricant spray beams 21 and by way of the cooling lubricant spray beams 21 is sprayed onto the working rollers 9, 10. The cooling lubricant quantities that are in each case dispensed by the cooling lubricant spray beams 21 are set by the cooling lubrication controller 25 by actuating the cooling lubricant pump 19. Cooling lubricant that is sprayed onto the working rollers 9, 10 is transported to the contact zones 15, 16 on account of the rotation of the working rollers 9, 10.

(9) An additive lubricant can be applied to the rollable material 3 by way of the additional lubricating device 7. The additive lubricant is a pure lubricant, for example a rolling oil, or a lubricant emulsion made of a carrier liquid and a lubricant, for example water as the carrier liquid and rolling oil as the lubricant, wherein the lubricant proportion of the additive lubricant is higher than the lubricant proportion of the cooling lubricant, and is approximately 20%, for example.

(10) The additional lubricating device 7 comprises an additive lubricant pump 27, in each case at least one additive lubricant spray beam 29 for each contact surface 17, 18 of the rollable material 3, additive lubricant lines 31, and an additional lubrication controller 33. Each additive lubricant spray beam 29 has additive lubricant nozzles for dispensing additive lubricant onto the respective contact surface 17, 18. The additive lubricant is pumped by the additive lubricant pump 27 through the additive lubricant lines 31 to the additive lubricant spray beams 29 and is sprayed onto the contact surfaces 17, 18 by way of the additive lubricant spray beams 29. The additive lubricant quantities A that are in each case dispensed by the additive lubricant spray beams 29 are set by the additional lubrication controller 33 by actuating the additive lubricant pump 27. Additive lubricant that is sprayed onto the contact surfaces 17, 18 is transported to the contact zones 15, 16 on account of the movement of the rollable material 3.

(11) With regard to the rolling direction 13, the additive lubricant spray beams 29 herein are disposed ahead or upstream of the rolling gap 11 at a predefined application spacing D, in order for the additive lubricant to be applied to the rollable material 3 at this application spacing D ahead of the rolling gap 11. As a result, the additive lubricant acts on the contact surfaces 17, 18 of the rollable material 3 until the additive lubricant or the surfaces 17, 18 reaches the rolling gap 11. Adhesion of the additive lubricant to the contact surfaces 17, 18 is enhanced during this dwell time. On account thereof, the lubricating effect (the so-called plate-out) of the additive lubricant in the contact zones 15, 16 is advantageously improved as compared to an application of the additive lubricant to the contact surfaces 17, 18 directly ahead of the rolling gap 11.

(12) In order for the additive lubricant quantities A to be applied to the contact surfaces 17, 18 to be set, a lubrication requirement for each contact zone 15, 16 is determined so as to depend on at least one process parameter of the rolling process. A rollable material speed v of the rollable material 3 is used herein as a process parameter. The rollable material speed v herein is determined, for example, by the additional lubrication controller 33 from measuring signals 35 of a strip speed sensor 37 that are supplied to the additional lubrication controller 33, said strip speed sensor 37 detecting a strip speed of the rolled strip. Material properties 41 of the respective rollable material 3, for example a compressive strength, and/or a roughness of the rollable material 3 are optional further process parameters for determining the lubrication requirement, the optional further process parameters being supplied as material property data 41 to the additional lubrication controller 33 by a production system 43.

(13) Furthermore, relative speeds between the contact surfaces 17, 18 of the rollable material 3 at established reference locations and the surfaces of the working rollers 9, 10 can optionally be used as process parameters for determining the lubrication requirement. The relative speeds can be determined, for example, from the rollable material speed v at a reference location and from measuring signals 35 of rotation speed sensors 39 for detecting the revolutions of the working rollers 9, 10, and from the thicknesses of the rollable material 3 ahead of and behind the rolling gap 11, cf. to this end, the equation (3.13) on page 113 in H. Hoffmann, R. Neugebauer and G. Spur (publishers), “Handbuch Umformen” (“Manual of forming”), 2nd edition, Carl Hanser Verlag, 2012, ISBN 978-3-446-42778-5. A viscosity of the cooling lubricant, and/or a thickness of the rollable material 3 are further optional process parameters for determining the lubrication requirement. If necessary, the respective cooling lubricant quantities C that are currently present in the contact zones 15, 16 and/or the lubricant proportion of the cooling lubricant can furthermore be recorded and be used as process parameters. Moreover, control data 45 can be exchanged between the cooling lubrication controller 25 and the additional lubrication controller 33, in order for the settings of the cooling lubricant quantities C and the additive lubricant quantities A to be adjusted with respect to each other.

(14) The additive lubricant is applied to each contact surface 17, 18 so as to depend on the lubrication requirement determined for the contact zones 15, 16 of the contact surface 17, 18 when the cooling lubricant quantity C currently introduced into the contact zones 15, 16 does not cover the lubrication requirement determined for the contact zone 15, 16, for example because a rollable material speed v changes or a rollable material 3 having an increased compressive strength is being rolled. The cooling lubricant quantities C applied to the working rollers 9, 10 herein are either kept constant or likewise set so as to depend on the at least one process parameter of the rolling process, and/or on the additive lubricant quantities A applied to the contact surfaces 17, 18, cf. to this end the description pertaining to FIG. 2.

(15) FIG. 2 illustrates a method for rolling a rollable material 3, having a roll stand 1, a cooling lubricating device 5, and an additional lubricating device 7, the devices being configured according to FIG. 1. To this end, FIG. 2, in a manner depending on a time t, shows profiles v(t), C(t), A(t) of a rollable material speed v of the rollable material 3, of a cooling lubricant quantity C which by way of the cooling lubricating device 5 is applied to a working roller 9, 10 of the roll stand 1, and of an additive lubricant quantity A, which by way of the additional lubricating device 7, is applied to a contact surface 17, 18 of the rollable material 3 that contacts the working roller 9, 10 in a contact zone 15, 16. The cooling lubricant quantity C and the additive lubricant quantity A herein are in each case defined as a volume that is applied per unit of time.

(16) FIG. 2 shows a case in which the rollable material 3 is composed of different rolled part-strips which are welded to one another. A first rolled part-strip herein is initially rolled between the temporal points to and t.sub.4. Subsequently a first transition region between the first rolled part-strip and a second rolled part-strip having a first weld seam that connects the two rolled part-strips is rolled between the temporal points t.sub.4 and t.sub.5. Subsequently, the second rolled part-strip is rolled between the temporal points t.sub.5 and t.sub.8. Subsequently, a second transition region between the second rolled part-strip and a third rolled part-strip having a second weld seam that connects the two rolled part-strips is rolled between the temporal points t.sub.8 and t.sub.9. Subsequently, the third rolled-part strip is rolled as from the temporal point t.sub.9. The second rolled part-strip herein has a higher compressive strength than the first rolled part-strip and the third rolled part-strip, the two latter having the same compressive strength.

(17) The cooling lubricant quantity C and the additive lubricant quantity A herein are in each case set by the cooling lubrication controller 25 and the additional lubrication controller 33 so as to depend on a lubrication requirement which for the contact zones 15, 16 is determined so as to depend on the rollable material speed v and on the compressive strength of the respective part-strip, and optionally on further process parameters mentioned above. In order for the lubrication requirement to be determined, for example a so-called Stribeck diagram for a friction coefficient of the friction between the contact surface 17, 18 and the working roller 9, 10 in the contact zone 15, 16 so as to depend on the process parameters is used, such as is known, for example, from J.B.A.F. Smeulders, “Lubrication in the Cold Rolling Process Described by a 3D Stribeck Curve”, AISTech 2013 Proceedings, pp. 1681-1689.

(18) The first rolled part-strip between the temporal points to and t.sub.1 is rolled at a first rollable material speed v.sub.1. The rollable material speed v between the temporal points t.sub.1 and t.sub.2 is increased to a second rollable material speed v.sub.2. The second rollable material speed v.sub.2 is maintained up to the temporal point t.sub.3. The lubrication requirement between the temporal points to and t.sub.3 can be covered solely by the cooling lubricant such that no additive lubricant is applied. The increase of the rollable material speed v from the first rollable material speed v.sub.1 to the second rollable material speed v.sub.2 increases the lubrication requirement. The increased lubrication requirement is covered by a corresponding increase of the cooling lubricant quantity C.

(19) The rollable material speed v between the temporal points t.sub.3 and t.sub.4 is heavily reduced from the second rollable material speed v.sub.2 to a third rollable material speed v.sub.3, in order to prepare the rolling of the first transition region between the first rolled part-strip and the second rolled part-strip comprising the first weld seam. The first transition region thereafter, between the temporal points t.sub.4 and t.sub.5, is rolled at the third rollable material speed v.sub.3. Subsequently, the rollable material speed v between the temporal points t.sub.5 and t.sub.6 is increased to a fourth rollable material speed v.sub.4 at which the second rolled part-strip is rolled between the temporal points t.sub.6 and t.sub.7.

(20) The lubrication requirement for the rolling of the first transition region herein is increased in relation to the lubrication requirement for the rolling of the first rolled part-strip because of the very low third rollable material speed v.sub.3. The lubrication requirement for the rolling of the second rolled part-strip is even higher than the lubrication requirement for the rolling of the first transition region due to the high compressive strength of the second rolled part-strip. Therefore, additive lubricant is applied as from the temporal point t.sub.3, wherein a larger additive lubricant quantity A is applied for the rolling of the second rolled part-strip between the temporal points t.sub.6 and t.sub.7 than for the rolling of the first transition region between the temporal points t.sub.4 and t.sub.5. The cooling lubricant quantity C applied between the temporal points t.sub.3 and t.sub.6 is simultaneously decreased and kept constant between the temporal points t.sub.6 and t.sub.7, in order for any washing-off of applied additive lubricant by the cooling lubricant to be prevented or reduced, respectively.

(21) The rollable material speed v between the temporal points t.sub.7 and t.sub.8 is again decreased from the fourth rollable material speed v.sub.4 to the third rollable material speed v.sub.3, in order to prepare the rolling of the second transition region between the second rolled part-strip and the third rolled part-strip comprising the second weld seam. The second transition region thereafter, between the temporal points t.sub.8 and t.sub.9, is rolled at the third rollable material speed v.sub.3. Subsequently, the rollable material speed v between the temporal points t.sub.9 and t.sub.10 is increased to the second rollable material speed v.sub.2 at which the third rolled part-strip is rolled between the temporal points t.sub.10 and t.sub.11.

(22) Accordingly, the additive lubricant quantity A applied is first decreased for the rolling of the second transition region, and no additive lubricant at all is applied for the rolling of the third rolled part-strip at the second rollable material speed v.sub.2. Concurrently, the applied cooling lubricant quantity C is increased again.

(23) The rollable material speed v between the temporal points t.sub.11 and t.sub.12 is decreased from the second rollable material speed v.sub.2 to a fifth rollable material speed v.sub.5 at which the third rolled part-strip is rolled as from the temporal point t.sub.12.

(24) The rolling of the third rolled part-strip at the fifth rollable material speed v.sub.5 necessitates a lubrication requirement which cannot be covered solely by the cooling lubricant. Therefore, additive lubricant is again applied for the rolling of the third rolled part-strip at the fifth rollable material speed v.sub.5, and the cooling lubricant quantity C applied is simultaneously reduced, wherein the additive lubricant quantity A and the cooling lubricant quantity C applied are mutually tuned such that the lubrication requirement is covered and any washing-off of applied additive lubricant by the cooling lubricant is prevented or reduced, respectively.

(25) FIG. 3 schematically shows a rolling line 47 of a rolling mill, having a plurality of roll stands 1 disposed behind one another for rolling a rollable material 3. The roll stands 1 have in each case two working rollers 9, 10 that are disposed one on top of the other, and have one support roller 49 for each working roller. For each roll stand 1, the rolling line 47 comprises one cooling lubricating device 5 (not illustrated in FIG. 3) and one additional lubricating device 7. The cooling lubricating devices 5 are in each case configured like the cooling lubricating device 5 illustrated in FIG. 1, and the additional lubricating devices 7 are in each case configured like the additional lubricating device 7 illustrated in FIG. 1, wherein, with regard to the rolling direction 13, the additive lubricant spray beams 29 of each additional lubricating device 7 are disposed at the application spacing D ahead of the rolling gap 11 of the associated roll stand 1.

(26) While the invention has been illustrated and described in detail by way of preferred exemplary embodiments, the invention is not limited by the disclosed examples, and other variations can be derived herefrom by a person skilled in the art without departing from the scope of protection of the invention.