Deterministically textured working roll for use in a cold-rolling mill, method for producing a deterministically textured working roll for use in a cold-rolling mill, and cold-rolling mill

Abstract

The invention relates to a deterministically textured working roll (1) for use in a cold-rolling mill, to a method for producing a deterministically textured working roll (1) for use in a cold-rolling mill and to a cold-rolling mill.

Description

[0001] Deterministically textured work roll for use in a cold rolling mill, method for producing a deterministically textured work roll for use in a cold rolling mill and cold rolling mill

[0002] The invention relates to a deterministically textured work roll for use in a cold rolling mill, a method for producing a deterministically textured work roll for use in a cold rolling mill and a cold rolling mill.

[0003] Work rolls in rolling mills, especially in cold rolling mills for flat steel production, are typically machined before use. Conventional work rolls are usually machined using a grinding process, which imparts a defined roughness to the work roll surfaces. The work rolls are then provided with different textures depending on the application.

[0004] These textures can be applied using, among other methods, the SBT (shot blasting texturing) process, the EDT (electro discharge texturing) process, the EBT (electron beam texturing) process, grinding structures, or the TOPOCROMO (reactor coating) process. These processes involve the application of a stochastic surface topography to work rolls. EP 1 368 140 B1 discloses a corresponding example for EDT. The EBT process also enables the application of a deterministic texture. A completely different process for the application of stochastic as well as geometrically determined, i.e. deterministic, surface topographies is the laser beam texturing (LT) process, in particular using a single or multiple shot, which leads to ablation on the surface of the roll material and thus to the establishment of a surface topography, cf.For example, see EP 0 184 568 B1, JP 56-119 687 A, JP 03-267 319 A, and DE 695 09 883 T2. Depending on the application, the rolls can be finely ground in a grinding process after texturing. After this process, depending on the requirements of the work rolls, they are coated with a metallic protective coating before being (re)used in the rolling stands.

[0005] The background to conventional surface finishing of work rolls is that equipping the surfaces of the work rolls with a metallic protective coating offers improved wear protection with regard to service life, as well as a positive influence on the required (strip) cleanliness. Furthermore, it is state of the art that reducing the roughness of work rolls for cold rolling of steel materials leads to less strip contamination. The problem here is that the rolling conditions are worsened by "smoother" work rolls. In particular, the required grip condition is negatively affected by the lower roughness. This behavior applies generally to cold rolling, but especially to discontinuous cold rolling.Thus, the gripping condition during cold rolling and the prevention of slipping of the work rolls on the strip to be rolled must be ensured with reduced friction, which can be described by the friction coefficient.

[0006] The object of the invention is therefore to provide a deterministically textured work roll for use in cold rolling mills, which meets the requirements of cold rolling, in particular without the use of a metallic protective layer.

[0007] The problem relating to a deterministically textured work roll for use in a cold rolling mill is solved by the features of claim 1. The problem relating to a method for producing a deterministically textured work roll for use in a cold rolling mill is solved by the features of claim 6. The problem relating to a cold rolling mill is solved by the features of claim 10.

[0008] A first teaching of the invention relates to a deterministically textured work roll with a surface for use in a cold rolling mill, wherein the surface has a topography with plateaus interrupted by depressions, wherein the plateaus occupy a maximum area of ​​90% with respect to the entire surface of the work roll, wherein the depressions have a void volume of between 0.4 cm 3 and 4.4 cm 3 per m 2 the surface of the work roll.

[0009] The topography according to the invention on the surface of the work roll is designed in such a way that rollability is guaranteed when the topography is used. During the cold rolling process, it is beneficial that (strip) dirt, roll abrasion and / or rolling emulsion are specifically removed and / or abrasion is reduced. The applied topography can ensure that rolling emulsion is present in the roll gap at all times and that any abrasion caused by the rolling process is simultaneously carried away by the flow of the rolling emulsion through the topography and thus does not remain on the strip. During cold rolling, friction plays a significant role in the force development in the roll gap. The relative speed during rolling has an effect in the form of frictional shear stresses between the roll and the rolling stock. In accordance with Coulomb's law of friction, the friction value is taken into account, which represents only a calculated value or an average value.Friction during rolling is necessary to pull the rolled material into and through the roll gap without external forces. These frictional conditions are called grip and pull-through conditions, which are familiar to those skilled in the art. The grip condition is met when the pulling-in friction force component in the rolling direction is greater than or equal to the repulsive normal force component. Gripping is possible when the pressure angle is smaller than the friction angle. The pull-through condition is met when the pressure angle during rolling is twice as large as during gripping.

[0010] If the empty volume of the wells falls below 0.4 cm 3 per m 2 the surface of the work roll cannot be guaranteed that the strip can be pulled through and that the gripping condition is met.

[0011] If the empty volume of the wells exceeds 4.4 cm 3 per m 2The surface of the work roll has many small plateau areas interrupted by a large number of depressions arranged one after the other, which means that rolling or the desired deformation in the rolling stand cannot be guaranteed.

[0012] The empty volume of the depressions can be determined using DIN EN ISO 25178-2:2012-09 by, for example, recording a partial area, for example an examined measurement area of ​​1 mm x 1 mm, and then creating a depth histogram using software such as psoft analysis premium (version 6). The upper limit Smr(cl) generated from this corresponds to the area of ​​the plateaus, which, after the depth histogram, represents the most frequently occurring texture depth. The depth histogram is transferred into a graphical representation, for example, of the empty volume parameters of the examined measurement area. The second limit is set at the deepest texture depth of the surface / measurement area. In this way, the empty volume of the depressions between the surface of the texture and the respective deepest texture points can be determined. cl is at the surface of the texture with the most frequent distribution in percentage terms, and c2 is at the deepest point of the texture.

[0013] The area of ​​the plateaus relative to the total surface of the work roll is in particular a maximum of 85%, preferably a maximum of 80%, preferably a maximum of 75%, particularly preferably a maximum of 70%, further preferably a maximum of 65%. To ensure rollability, the area of ​​the plateaus relative to the total surface of the work roll is at least 20%, in particular at least 25%, preferably at least 30%.

[0014] At the same time, it was shown that the topography of the invention on the work roll exhibits a service life comparable to that of standard work rolls with surfaces coated with metallic layers. Thus, the work roll according to the invention can be considered an "uncoated" work roll with a bare surface.

[0015] Work rolls for cold rolling processes are typically made of metal, for example, they are forged or cast. It goes without saying that the topography is provided axially on the surface of the work roll to such an extent that the flat material to be rolled is covered by the topography across its entire width in the rolling direction.

[0016] The flat material to be cold-rolled is preferably generally a steel flat product in strip form (steel strip). Alternatively, for example, an aluminum flat product (aluminum strip) can also be cold-rolled using the work roll according to the invention.

[0017] Due to their function, the work roll in a cold rolling process must meet different requirements than rolls in skin-pass processes, so-called skin-pass rolls. This ensures, in addition to the aforementioned tasks of removing abrasion and extending service life, a largely slip-free cold rolling process. The topography on the surface of work rolls for the cold rolling process can therefore be precisely adjusted and is not comparable to the topography on the surfaces of skin-pass rolls.

[0018] Deterministically textured means that a surface structure is created with recurring structures, for example embossings which have a defined shape and / or design, cf. EP 2 892 663 Bl. In particular, this also includes surfaces with a (guasi-) stochastic appearance, which, however, are applied by means of a deterministic texturing process and are thus composed of deterministic form elements.

[0019] According to one embodiment of the work roll, the depressions have a depth between 2 and 40 μm. The depth can be at least 3 μm, 4 μm, 5 μm, preferably at least 7 μm, 8 μm, or 9 μm, in order to maintain the specifically adjusted topography and thus a certain service life of the work roll in the event of unavoidable wear during cold rolling. The depth can, in particular, be limited to a maximum of 35 μm, 30 μm, or 25 μm.

[0020] According to one embodiment of the work roll, the depressions can have a width between 1 and 100 μm. The width can be at least 5 μm, 10 μm, 15 μm, preferably at least 20 μm, in order to ensure, in conjunction with the depth, a sufficient empty volume for abrasion and thus for the corresponding removal during cold rolling. The width can, in particular, be limited to a maximum of 85 μm, 60 μm, in order to avoid unwanted elevations, particularly in the rolling direction, and thus to avoid near-surface profiling on the flat material to be rolled.

[0021] According to one embodiment of the work roll, the surface of the plateaus of the work roll has a mean roughness Ra of a maximum of 0.5 pm. Since a mean roughness Ra cannot practically be 0 pm, this is > 0 pm. The mean roughness Ra of the surface of the plateaus can be at least 0.01 pm, 0.02 pm, 0.03 pm, in particular at least 0.04 pm, 0.05 pm, 0.06 pm. The mean roughness Ra of the surface of the plateaus can in particular be limited to a maximum of 0.45 pm, 0.40 pm, 0.35 pm, preferably to a maximum of 0.30 pm, 0.25 pm.

[0022] According to one embodiment of the work roll, the (entire) surface of the work roll has a mean roughness Ra between 0.4 and 4 pm. The mean roughness Ra of the surface of the plateaus and the mean roughness Ra of the depressions are taken into account, so that the overall surface can have a mean roughness Ra of, in particular, at least 0.45 pm, 0.5 pm, or 0.55 pm. The mean roughness Ra of the surface of the work roll can, in particular, be limited to a maximum of 3.8 pm, 3.6 pm, 3.4 pm, preferably to a maximum of 3.2 pm, or 3 pm.

[0023] According to one design of the work roll, the plateaus are shaped as polygons, particularly quadrilaterals. Other geometric shapes are also conceivable, but a deterministic arrangement of the plateaus must be ensured.

[0024] According to a second teaching, the invention relates to a method for producing a deterministically textured work roll for use in a cold rolling mill, wherein a work roll to be textured is provided, wherein the surface of the work roll is textured in order to create a topography on the surface of the work roll, wherein depressions are introduced into the surface, which lead to interrupted plateaus, wherein the plateaus occupy a maximum area of ​​90% with respect to the entire surface of the work roll, wherein the depressions have a void volume of between 0.4 cm 3 and 4.4 cm 3 per m 2 the surface of the work roll.

[0025] To avoid repetition, reference is made to the aforementioned designs of the work roll.

[0026] According to one embodiment of the method, a thermal method is used for texturing, for example a texturing method using a laser. Devices for carrying out the laser texturing method are prior art, see also EP 2 892 663 B1, EP 3 172 006 B1 and EP 3 877 112 A1. In this way, it is possible to create a topography on the surface of the work roll which, through laser bombardment, causes ablation, i.e. material removal, on the surface in the area of ​​the impacting bombardment. Through targeted adjustment, the laser shots can overlap or be spaced so far apart that an almost initial state remains between the laser shot areas. The areas not hit by the laser bombardment thus form the plateaus on the surface of the work roll.

[0027] According to an alternative embodiment of the method, a mechanical method is used for texturing, for example, by engraving. Devices for performing the engraving are also state of the art.

[0028] According to another alternative embodiment of the method, a chemical process, such as etching, is used for texturing. Devices for performing the etching are also state of the art.

[0029] According to a third teaching, the invention relates to a cold rolling mill with at least one, in particular at least two, preferably at least three, preferably at least four and at most nine, in particular at most seven, preferably at most five rolling stands, wherein at least one rolling stand has two work rolls according to the invention. A cold rolling mill with one rolling stand can, for example, be a reversing stand. With two or more rolling stands of a cold rolling mill, two work rolls according to the invention can be provided in each case, particularly viewed in the process direction, at least in the first and second or in the second and third rolling stands. The cold rolling mill is preferably a tandem cold rolling mill or part thereof. Among other things, further systems can also be arranged upstream and / or downstream of the cold rolling mill in the process direction, such as, for example, a continuous pickling line in the advance section of the cold rolling mill.The arrangement of work rolls in a rolling stand of a cold rolling mill as well as the structure and functioning of a cold rolling mill or a tandem cold rolling mill are state of the art.

[0030] An exemplary embodiment of a work roll (1) according to the invention and the corresponding deterministic topography (3) is shown in the single Figure 1.

[0031] Top right is a sketch of a work roll (1) with a surface (2) for use in a cold rolling mill. Two enlargements are shown from the small window at the top left and bottom of Figure 1, each schematically depicting a partial top view of the surface (2) of the work roll (1) with a topography (3). The bottom left illustration in Figure 1 shows a partial cross-section of the work roll (1), which shows the topography (3) on the surface.

[0032] (2) with the plateaus (3.1) and depressions (3.2). The depth (T), which can be between 2 and 40 pm, and the width (B), which can be between 1 and 100 pm, of the depression (3.2) are illustrated in the partial cross-sectional view. The depth (T) is determined from the highest point of the plateaus (3.1) surrounding the depression (3.2) on the surface (2) of the work roll (1) and the deepest point in or within the depression (3.2) made in the work roll (1). The width (B) is determined on the surface (2) between two opposite points at which the curvature or radius and thus the start of the impression of the depression (3.2) begins.

[0033] The deterministically textured work roll (1) with a surface (2) for use in a cold rolling mill, wherein the surface (2) has a topography (3) with plateaus (3.1) interrupted by depressions (3.2), wherein the plateaus (3.1) occupy a maximum area of ​​90% with respect to the entire surface (2) of the work roll (1), wherein the topography

[0034] (3) with quadrangular plateaus (3.1), see Figure 1 left-hand versions in different sizes of the quadrangles. The recesses (3.2) have a void volume between 0.4 cm 3 and 4.4 cm 3 per m 2 the surface (2) of the work roll (1).

[0035] The surface of the plateaus (3.1) of the work roll (1) has a maximum mean roughness Ra of 0.5 pm. The surface (2) of the work roll (1) has a mean roughness Ra between 0.4 and 4 pm. In practical tests, two work rolls (1) according to the invention were used in a rolling stand of a tandem cold rolling mill to determine their service life and effectiveness, particularly in comparison to standard work rolls equipped, for example, with a metallic protective coating. The work rolls (1) according to the invention were uncoated.

[0036] The work rolls (1) used according to the invention were those shown at the top left and bottom in Figure 1.

[0037] The upper version has plateaus (3.1) formed as small squares, with an area of ​​57% in relation to the total surface (2) of the working roll (1) and an empty volume of the depressions (3.2) of 3 cm 3 per m 2the surface (2) of the work roll (1). The average depth (T) of the depressions (3.2) was approximately 7 pm. The average width (B) of the depressions (3.2) was approximately 35 pm. The average roughness Ra of the surface of the plateaus (3.1) was approximately 0.25 pm. The overall average roughness Ra of the surface (2) of the work roll (1) was 0.57 pm.

[0038] The lower version has plateaus (3.1) formed as a medium-sized quadrangle, with an area of ​​35% in relation to the total surface (2) of the work roll (1) and an empty volume of the depressions (3.2) of 0.5 cm 3 per m 2 the surface (2) of the work roll (1). The average depth (T) of the depressions (3.2) was approximately 7 pm. The average width (B) of the depressions (3.2) was approximately 35 pm. The average roughness Ra of the surface of the plateaus (3.1) was approximately 0.25 pm. The overall average roughness Ra of the surface (2) of the work roll was 3.2 pm.

[0039] Flat steel products in the form of steel strips (coils) were cold-rolled. The longer the service life (coil throughput), the more economical the use of the work rolls. The standard work rolls and the work rolls according to the invention (1) were tested with service lives typically achieved in cold rolling, and it was found that the topography (3) was still sufficiently present. Thus, comparable results with the work rolls according to the invention (1) were achieved compared to the work rolls known from the prior art.

Claims

Patent claims 1. Deterministically textured work roll (1) with a surface (2) for use in a cold rolling mill, wherein the surface (2) has a topography (3) with plateaus (3.1) interrupted by depressions (3.2), wherein the plateaus (3.1) occupy a maximum area of ​​90% of the entire surface (2) of the work roll (1), characterized in that the depressions (3.2) have an empty volume of between 0.4 cm 3 and 4.4 cm 3 per m 2 the surface (2) of the work roll (1).

2. Work roll according to claim 1, wherein the depressions (3.2) have a depth between 2 and 40 pm.

3. Working roll according to one of the preceding claims, wherein the surface of the plateaus (3.1) the work roll (1) has a mean roughness Ra of maximum 0.5 pm.

4. Work roll according to one of the preceding claims, wherein the surface (2) of the work roll (1) has a mean roughness Ra between 0.4 and 4 pm.

5. Working roll according to one of the preceding claims, wherein the plateaus (3.1) are formed as a square.

6. Method for producing a deterministically textured work roll (1) for use in a cold rolling mill, wherein a work roll to be textured is provided, wherein the surface of the work roll is textured in order to produce a topography (3) on the surface (2) of the work roll (1), wherein depressions (3.2) are introduced into the surface (2), which lead to interrupted plateaus (3.1), wherein the plateaus (3.1) occupy a maximum area of ​​90% with respect to the entire surface (2) of the work roll (1), characterized in that the depressions (3.2) with a void volume between 0.4 cm 3 and 4.4 cm 3 per m2 the surface (2) of the work roll (1).

7. The method of claim 6, wherein a thermal texturing process is used. Method according to claim 6, wherein a mechanical method is used for texturing. Method according to claim 6, wherein a chemical method is used for texturing. Cold rolling mill with at least one and at most nine rolling stands, characterized in that at least one rolling stand has two work rolls (1) according to one of claims 1 to 5. Cold rolling mill according to claim 10, wherein, viewed in the process direction, two work rolls (1) are provided in each of at least the first and second rolling stands or in the second and third rolling stands. Cold rolling mill according to claim 10 or 11, wherein the cold rolling mill is a tandem cold rolling mill. Cold rolling mill according to claim 10, wherein the cold rolling mill comprises a reversing stand.

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