Abstract
A planishing roll has a surface structure, in particular for producing flat products from a metallic material, in particular from a steel material. The surface structure has a material ratio of 2% at a depth of 0.2 m to 9 m, preferably at a depth of 0.8 m to 5.5 m. The depth is measured, starting from a zero line, in the direction of an axis of rotation of the planishing roll, with the zero line running parallel to the axis of rotation of the planishing roll and. Starting from the surface of the planishing roll, the zero line is displaced in the direction of the axis of rotation of the planishing roll until the material ratio of the planishing roll is 0.1%.
Claims
1. A planishing roll comprising a surface structure, in particular for producing a flat product of a metal material, in particular a steel material, said surface structure having a material proportion of 2% at a depth of 0.2 m to 9 m, with the depth being measured starting from a zero line in a direction of an axis of rotation of the planishing roll, said zero line extending in parallel relation to the axis of rotation of the planishing roll and being displaced starting from the surface of the planishing roll in the direction of the axis of rotation of the planishing roll until the material proportion is 0.1%.
2. The planishing roll of claim 1, wherein the depth is 0.8 m to 5.5 m.
3. The planishing roll of claim 1, wherein the surface structure has a material proportion of 5% at a depth of 0.7 m to 12 m, preferably at a depth of 1.1 m to 6.5 m.
4. The planishing roll of claim 1, wherein the surface structure has a material proportion of 10% at a depth of 1.0 m to 15 m, preferably at a depth of 1.4 m to 7.4 m.
5. The planishing roll of claim 1, wherein the surface structure is electrolytically structure-chromium plated and hard-chromium plated.
6. The planishing roll of claim 1, wherein the surface structure has a roughness Ra=0.3-5 m and a peak number RPc=50300 1/cm.
7. A method for planishing a flat product of a metal material, in particular a steel material, comprising: rolling the flat product with a planishing roll having a material proportion of 2% at a depth of 0.2 m to 9 m, with the depth being measured starting from a zero line in a direction of an axis of rotation of the planishing roll, said zero line extending in parallel relation to the axis of rotation of the planishing roll and being displaced starting from the surface of the planishing roll in the direction of the axis of rotation of the planishing roll until the material proportion is 0.1%.
8. The method of claim 7, wherein the depth is 0.8 m to 5.5 m.
9. The method of claim 7, wherein the surface structure has a material proportion of 5% at a depth of 0.7 m to 12 m, preferably at a depth of 1.1 m to 6.5 m.
10. The method of claim 7, wherein the surface structure has a material proportion of 10% at a depth of 1.0 m to 15 m, preferably at a depth of 1.4 m to 7.4 m.
11. The method of claim 7, further comprising electrolytically structure-chromium plating and hard-chromium plating the surface structure.
12. The method of claim 7, wherein the surface structure has a roughness Ra=0.3-5 m and a peak number RPc=50-3001/cm.
13. The method of claim 7, wherein the flat product is rolled with a degree of planishing in a range of 0.1 to 2.0%.
Description
BRIEF DESCRIPTION OF THE DRAWING
[0031] The Invention will be explained in greater detail hereinafter with the aid of an exemplified embodiment and associated drawings. In the figures:
[0032] FIG. 1 shows a graph including a schematic exemplary progression of a surface structure of a roll in accordance with the invention,
[0033] FIG. 2 shows an Illustration of a zero line selected for measuring the roll material proportion,
[0034] FIG. 3 shows a schematic enlarged sectional view of a surface structure of a roll in accordance with the Invention with an associated material proportion graph,
[0035] FIG. 4 shows a sectional view according to FIG. 2 for a conventional roll with an associated material proportion graph, and
[0036] FIG. 5 shows a projection of a section through a flat product with PRETEX topography in accordance with the Invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0037] FIG. 1 shows a Cartesian coordinate system with a depth in m of approximately 15 to 0 m as the y-axis and a material proportion of approximately 0 to approximately 10% as the x-axis. An exemplary curve of a surface structure of a planishing roll in accordance with the invention is indicated in the coordinate system and is designated by A.
[0038] The material proportion in % describes the presence of material of the planishing roll within a surface which is representative of the entire upper peripheral surface of the planishing roll. Therefore, a proportion of roughness valleys can be considered to be the opposite of the material proportion in %. The proportion of material in the surface is ascertained for this purpose by means of a 3D measurement starting from the surface in the direction of a central axis of rotation of the roll. The 3D measurement relates to a representative surface of approximately 2.5 mm.sup.2. The material proportions in % ascertained by the 3D measurement then relate to a depth given in m starting from the surface of the planishing roll. The material proportions can be determined using the roughness profile of the roll. The material proportions illustrated in FIG. 2 have been ascertained according to ISO 25178 from an extensive 3D roughness measurement on the corresponding rolls. To ensure that the ascertained material proportions are comparable, a reference plane must be defined for these measurements, from which the height or depth values are counted. In general, in order to produce material proportion curves a zero line displacement of 5% is used in this case, i.e. starting from the surface of the roll in the direction of the axis of rotation of the roll. Since the roll profiles already have apparent differences in the region of the first 5% of the material proportion, a zero line displacement of only 0.1% material proportion is used, i.e. the zero line for measuring or determining the depth in m is displaced only until the material proportion is 0.1% of the roughness peaks of the surface present in this region. The depth in m is then determined starting from the zero line in the direction of the axis of rotation of the roll. The depth Indicated in FIG. 2 is also averaged over the surface part of the roll and is representative of the entire peripheral surface of the roll because the planishing of the roll is uniform.
[0039] FIG. 2 shows an illustration of the above-described displacement of the zero line N starting from the surface of the planishing roll 1 radially in the direction of an axis of rotation D of the planishing roll 1. In this case, the zero line N extends in parallel with the axis of rotation D and in the region of the surface of the planishing roll 1. The axis of rotation D extends in the direction of the longitudinal extension of the planishing roll 1 and centrally in the planishing roll 1. The zero line N is displaced into schematically Indicated structure elements 2 of a surface structure of the planishing roll 1 and radially in the direction of the axis of rotation D until the desired material proportion of 0.1%, based on the structure elements 2, is achieved.
[0040] FIG. 1 shows that the exemplary progression A of a planishing roll in accordance with the invention starting from the depth of 0 m, based on the 0.1% material proportion, extends very flatly and only has a material proportion of 10% In the region of approximately 3.5 m. In qualitative terms, this can therefore be described as a planishing roll comprising a low material proportion at low depths. Furthermore, the Topocrom method produces a topography of hard chromium hemispheres with steep flanks.
[0041] Surface structures of planishing rolls which have a specific progression in the depth direction in the region of the material proportions of 2% to 10% are particularly favourable. This progression can be described as a sequence of selected percentage material proportions of the roll. A sequence of material proportions of 2%, 5% and 10% is selected hereinafter. Rolls, of which the material proportions and depths are in the following ranges enable production of an advantageous flat product topography:
material proportion 2%depth 0.2 m to 9 mpreferably depth 0.8 m to 5.5 m
material proportion 5%depth 0.7 m to 12 mpreferably depth 1.1 m to 6.5 m
material proportion 10%depth 1.0 m to 15 mpreferably depth 1.4 m to 7.4 m
[0042] These ranges relating to the depths and material proportions are indicated in FIG. 1 as polygons. The polygon with a dotted line shows the aforementioned further depth ranges and the polygons with a broken line show the preferred depth ranges.
[0043] A metallic flat product, in particular a steel strip, comprising an advantageous flat product topography, can be produced with such planishing rolls with an arbitrarily produced surface structure and the progression of material proportions described in relation to FIG. 1. For this purpose, a corresponding flat product is rolled in the longitudinal direction in a typical manner with planishing rolls which are deployed using external force, in particular hydraulic pressure. By virtue of the force transmitted linearly to the flat product volume located between the planishing rolls, the flat product is lengthened and thereby reduced in thickness and the surface structure of the planishing rolls is formed on the surface of the flat product. The material displacement follows the principle of least resistance, depicting the surface structure and lengthening the flat product. If the surface structure of the planishing rolls is completely filled, an increase in force acts upon the lengthening of the flat product. The maximum lengthening of the flat product Is defined by the change in the mechanical characteristic values of the flat product.
[0044] The ideal surface structure of a planishing roll for producing a topography of the flat product in accordance with specifications is configured in such a way that it can be depicted in the surface of the flat product before the maximum permissible strip lengthening is achieved.
[0045] A planishing roll comprising a surface structure as shown in FIG. 1 approximates an idealised structure. This planishing roll allows a high transmission of a specific rolling force which corresponds to a force per length of the line contacting the flat product, a change in the topography of the flat product and a low transmission of the specific rolling force in favour of a larger lengthening of the flat product. A typical specific rolling force Is in the region of 1.9 kN/mm. The change in topography can be described by the parameters of roughness Ra, peak number RPc or more generally by displaced volume. The lengthening of the flat product is expressed by the degree of planishing. Since the degree of planishing is generally defined by the change in the mechanical properties, the largest possible ratio between the change in topography and lengthening of the flat product is favourable in order to achieve a low waviness and small lengthening of the flat product. The waviness can be described by the Wsa (1-5) value according to SEP1941. In this case, a minimum degree of planishing is certainly required in order to achieve a desired change in topography before a desired degree of planishing is exceeded. The degree of planishing is approximately in the range of 0.1 to 2.0%.
[0046] A material proportion, which is low in accordance with the invention, on the planishing roll results in the contact forcei.e. high local pressuresbeing distributed over a small areaand thus results primarily in a change in topography instead of the lengthening of the flat product. By reason of the change in topography, a locally defined, lateral volume redistribution is effected on the surface of the flat product. The low material proportion of the planishing roll in accordance with the invention has a positive effect such that it hinders the volume redistribution to a lesser extent than planishing rolls comprising a higher material proportion. Accumulations of redistributed volumes at points on the surface of the flat product are avoided. The accumulations at points result in an undesirably high waviness Wsa (1-5) according to SEP1941.
[0047] The surface structures of planishing rolls comprising a low material proportion and the surface structure which are produced by methods which allow a surface structure with a high flank steepness are preferred. Such surface structures on planlshing rolls can be achieved preferably by the hard-chromium plating method known as Topocrom.
[0048] FIG. 3 schematically illustrates an enlarged sectional view of a surface structure of a roll in accordance with the invention with an associated material proportion graph. By way of example, the surface structure has elevations in the form of a rectangle, a parabola and a triangle. These elevations are separated by intermediate spaces which are defined in depth by a planar surface of the roll. Next to the schematic illustration, the graph known from FIG. 1 is illustrated in qualitative terms with the depth above the material proportion. It is apparent that, as known from the graph in FIG. 1, the material proportion of the elevations Is low overall and, as the depth Increases to a complete surface of the roll, increases Initially only slightly and greatly in the region of maximum depth. During planishing of a flat product, a roll comprising this type of surface structure with a low material proportion over the entire height or entire depth of the elevations results preferably in a change in topography of the planished flat product prior to the lengthening of its strip. A use of the rolls in accordance with the Invention results in a small waviness in the topography of the flat product and a small lengthening of the strip of the flat product.
[0049] FIG. 4 corresponds substantially to FIG. 3 but the surface structure is inverse to the surface structure shown in FIG. 3. Accordingly, the elevationsshown by way of example in FIG. 3in the form of a rectangle, parabola and triangle placed upside down each form the Intermediate spaces. The surface structure shown in FIG. 4 is found in conventional rolls. Also, next to the schematic illustration, the graph known from FIG. 1 is again illustrated in qualitative terms with the depth above the material proportion. In comparison with the curve progression in FIG. 3, it Is apparent that the material proportion of the elevations is high overall and, as the depth increases to a complete surface of the roll, increases initially greatly and only slightly in the region of maximum depth. During planishing of a flat product, a roll comprising this type of surface structure with a high material proportion over the entire height or entire depth of the elevations results preferably in a lengthening of the strip of the planished flat product prior to its change in topography. Since the length of the strip increases to a greater extent, configuration of the topography of the flat product will be possible only to a limited extent.
[0050] The surface structures shown in FIGS. 3 and 4 differ significantly in terms of their material proportions and their progression over the depth of the elevations of the surface structures. However, these surface structures cannot be distinguished in terms of the roughness index Ra but, when used on planishing rolls for transferring the roughness from the roll to the flat product, provide different results in terms of the Increase in waviness until the surface topography required by the customer and described by Ra and RPc of the sheet is achieved. The roughness index Ra is in the range of 0.9 to 1.4 m and the peak number RPc is greater than 751/cm.
[0051] FIG. 5 shows a projection of a section through a flat product comprising an inventive PRETEX topography which has been produced with a planishing roll comprising a material proportion which is low in accordance with the invention. The y-axis plots a height/depth in each case in m based on a zero line and the x-axis plots a length of the section in m. The Inventive PRETEX topography shows a pronounced sequence of elevations and valley-shaped intermediate spaces and has the characteristic values Ra=1.04 m, RPc=106 cm-1 and waviness Wsa (1-5)=0.208 m. A high flank steepness at the edge of the spherical cap Impression can also be seen. The material proportion of the associated planishing roll ascertained from a 3D roughness measurement is 2% at a depth of 2.0 m, 5% at a depth of 2.8 m and 10% at a depth of 4.3 m. This corresponds approximately to the progression indicated in FIG. 1 as A.
[0052] By using an inventive planishing roll comprising a low material proportion, it Is possible to achieve a sheet surface which with a low roughness (0.9 m<Ra<1.2 m) and high peak number (RPc>95/cm) has a low waviness Wsa (1-5) of less than 0.22 m. The material proportion of the sheet surface ascertained via a 3D roughness measurement is 2% at a depth of 1.5 m, 5% at a depth of 2.3 m and 10% at a depth of 2.8 m.
