Working roll for rolling a metallic item, roll stand, metallic strip, method for producing a working roll, and use of a working roll

Abstract

The invention relates to a working roll for rolling a metallic item, in particular for rolling a metallic strip, comprising: - a main body made of metal; and - an antiwear layer at least partially applied to the main body, wherein: the antiwear layer is a thermal sprayed coating; and the antiwear layer has a tungsten carbide (WC) proportion of greater than or equal to 10 wt.% and a ditungsten carbide (W2C) proportion of smaller than or equal to 50 wt.%, preferably smaller than or equal to 33 wt.% and especially preferably of smaller than or equal to 10 wt.% or smaller than or equal to 5 wt.%.

Description

[0001] Applicant: SMS group GmbH

[0002] Work roll for rolling a metallic product, rolling stand, metallic strip, method for producing a work roll and use of a work roll

[0003] The invention relates to a work roll for rolling a metallic material, in particular for rolling a metallic strip, comprising a base body made of metal and a wear protection layer arranged at least in regions on the base body, wherein the wear protection layer is a thermal splash protection layer.

[0004] The invention further relates to a rolling stand.

[0005] The invention further relates to a metallic strip which is cold-rolled by means of a work roll.

[0006] The invention further relates to a method for producing a work roll.

[0007] The invention also relates to a use of a work roll.

[0008] Generic work rolls and methods for producing such work rolls are known from the prior art.

[0009] In order to increase the service life of such work rolls, such work rolls are provided with a suitable wear protection layer on their surface, by means of which it is also possible to create a defined surface texture on a strip.

[0010] For the specific design of a wear protection layer, various influencing factors must be taken into account, since a wear protection layer in combination with high loads in a rolling process can also exhibit various wear characteristics.

[0011] Typically, a suitable wear-resistant coating comprises a hard chrome coating, which, however, is also prone to microcracking, which can adversely affect service life and corrosion resistance. Hexavalent chromium (Cr-6) has been used to manufacture the previously known wear-resistant coatings made of chromium, particularly hard chrome coatings. It is now considered proven that Cr-6 is carcinogenic and / or mutagenic.

[0012] There are different methods for applying a wear protection layer to a work roll.

[0013] The invention is based on the object of providing an improvement or an alternative to the prior art.

[0014] According to a first aspect, the object of the invention is achieved by a work roll for rolling a metallic material, in particular for rolling a metallic strip, comprising a base body made of metal and a wear protection layer arranged at least in regions on the base body, wherein the wear protection layer is a thermal splash protection layer, and wherein the wear protection layer has a proportion of tungsten carbide (WC) of greater than or equal to 10 wt. % and a proportion of ditungsten carbide (W2C) of less than or equal to 50 wt. %, preferably of less than or equal to 33 wt. % and particularly preferably of less than or equal to 10 wt. % or less than or equal to 5 wt. %.

[0015] Such small amounts of tungsten precipitates, particularly in the form of ditungsten carbide (W2C), in the wear protection layer have a particularly favorable effect on its properties, as will be explained in more detail below, in particular as can be seen from Table 1, whereby the tungsten precipitates listed in Table 1 are to be understood as tungsten precipitates in the form of ditungsten carbide (W2C).

[0016] Furthermore, it is also advantageous if the wear protection layer has a proportion of elemental tungsten (W) of less than or equal to 50 wt.%, preferably less than or equal to 33 wt.% and particularly preferably less than or equal to 10 wt.% or less than or equal to 5 wt.%.

[0017] Even such a small proportion of elemental tungsten (W) is advantageous, regardless of the other features of the invention, since it also allows wear protection layers of this type to be further developed extremely favorably.

[0018] For further advantageous values ​​for the weight fraction of tungsten precipitates in the wear protection layer and the associated properties of the wear protection layer, please refer to Table 1.

[0019] Tungsten precipitates in the form of elemental tungsten (W) and / or ditungsten carbide (W2C) can be formed by degradation of tungsten carbide (WC).

[0020] In particular, the application of pressure and temperature in conjunction with the required process times in which the starting material for the wear protection layer is processed plays a decisive role in the precipitation of ditungsten carbide (W2C) and / or elemental tungsten (W), with tungsten carbide (WC) first degrading to ditungsten carbide (W2C) and then the latter to elemental tungsten (W), depending on the physical parameters of pressure and temperature.

[0021] In this respect, shorter process times and / or lower temperatures are advantageous in the production of the wear protection layer in order to reduce degradation of tungsten carbide (WC) as much as possible or ideally to avoid it completely, whereby the degradation of tungsten carbide (WC) occurs in particular from 550 °C and above.

[0022] In this case, the faster the thermal spraying process takes place, in particular because the particles are cooler and / or the heating time of the particles is shorter, the lower the tungsten precipitation within the wear protection layer.

[0023] The aim is to achieve the lowest possible proportion of tungsten precipitates, which ideally are present in a negligible amount on the wear protection layer.

[0024] The starting material for the wear protection layer is preferably in the form of a powdery particle mixture of hard phase particles and matrix particles, wherein the hard phase particles comprise tungsten carbide (WC).

[0025] Tab. 1: Tungsten precipitates (elemental tungsten and / or ditungsten carbide W2C) in the wear protection layer (wt%): embrittlement, wear resistance, fracture toughness, adhesive tensile strength, service life, hardness and layer adhesion of the wear protection layer (each rated between 0 and 10 with the individual scales between smallest possible (0) and largest possible (10) (scale designation: kg) as well as neutral (0) and best possible (10) (scale designation: nb))

[0026] Tungsten precipitates in the wear protection layer, particularly in the form of elemental tungsten (W) and / or ditungsten carbide (W2C), can contribute to embrittlement of the wear protection layer, which can reduce the wear resistance of the wear protection layer, the fracture toughness of the wear protection layer, and / or the adhesive tensile strength of the wear protection layer with increasing tungsten precipitate content. Overall, a higher proportion of tungsten precipitates in the wear protection layer can therefore reduce its service life.

[0027] However, it should also be noted that a higher "wt%" content of tungsten precipitates, for example, can increase the hardness of the wear protection layer.

[0028] Furthermore, the proportion of tungsten precipitates within the wear protection layer can have an influence on the layer adhesion between adjacent, in particular superimposed, and not simultaneously worn individual layers of the wear protection layer, whereby the layer adhesion can decrease with an increasing proportion of tungsten precipitates.

[0029] In this respect, it is important to ensure that the wear protection layer has a balanced "wt. / " proportion of tungsten precipitates.

[0030] Solely by means of the proportion of tungsten precipitations, in particular the precipitations of elemental tungsten (W) and / or ditungsten carbide (W2C), a generic work roll can be advantageously further developed, so that related features or combinations of features are already advantageous without the other features of the invention.

[0031] The wear protection layer preferably has a chromium content of less than or equal to 90 wt . -%, preferably less than or equal to 60 wt . -% and particularly preferably less than or equal to 30 wt . -%.

[0032] For further advantageous values ​​for the chromium content of the wear protection layer and the associated properties of the wear protection layer, please refer to Table 2.

[0033] The present wear protection layer serves to protect the work roll from wear.

[0034] If the wear protection layer is designed as suggested, an improved wear resistance of the base body of the work roll can be ensured.

[0035] On the other hand, the risk of critical carcinogenic and / or mutagenic interactions with living beings, especially workers or operators, can be excluded or at least significantly reduced.

[0036] By means of the wear protection layer proposed here, the work roll, but especially also the wear protection layer itself, can be provided as freely as possible, preferably entirely, without chromium, in particular hard chromium, which has previously been predominantly required for wear protection layers, and this with at least the same or even improved qualitative properties, such as an improved surface quality, an improved service life and further improved properties of the work roll, as will be described in more detail below.

[0037] In any case, the wear protection layer makes it possible to ensure a consistent roughness on the work roll surface that lasts as long as possible, which influences the desired target values ​​for the metallic material to be rolled in a rolling process for as long as possible, such as in particular the roughness and texture or smoothness of a metallic material surface to be produced, in particular of a metallic strip to be produced.

[0038] In particular, a suitably designed wear protection layer for a working roll alone solves the problem of the invention.

[0039] It should also be pointed out here that in the context of this patent application, indefinite articles and indefinite numerical expressions such as "one...", "two..." etc. are generally to be understood as at least expressions, i.e. as "at least one...", "at least two..." etc., unless it is clear from the context or the concrete text of a particular passage that only "exactly one...", "exactly two..." etc. are meant.

[0040] At this point it should be mentioned that in the context of this patent application the expression "in particular" is always to be understood as introducing an optional, preferred feature. The expression is not to be understood as "and namely" or "namely".

[0041] Preferably, a lower nickel content should be set, in particular a nickel content of less than or equal to 90 wt.%, preferably less than or equal to 60 wt.% and particularly preferably less than or equal to 30 wt.%, since the wear resistance decreases with increasing nickel content.

[0042] For further advantageous values ​​for the nickel content of the wear protection layer and the associated properties of the wear protection layer, please refer to Table 2.

[0043] Further features, effects, advantages, and disadvantages can be found in Table 2 below:

[0044] Tab. 2: Chromium and / or nickel content (wt%) : Residual compressive stresses and wear resistance (evaluation between

[0045] 0 and 10 with the individual scales between smallest possible ( 0 ) and largest possible ( 10 ) ( scale designation : kg) as well as neutral ( 0 ) and best possible ( 10 ) ( scale designation : nb ) )

[0046] As can be seen from Table 2, the wear resistance of the wear protection layer can be improved with a larger chromium content and / or a smaller nickel content, whereby mutagenic and / or carcinogenic influences on the environment can be improved or avoided by a smaller chromium content and a smaller nickel content.

[0047] Tests have shown that the selection of the chromium content and / or the nickel content for the wear protection layer has an influence on the residual stresses resulting in the wear protection layer, whereby in the context of this description the term residual stress always means compressive residual stress, unless this is explicitly clarified otherwise.

[0048] The wear resistance of the wear protection layer can also be enhanced by the level of residual compressive stresses in the wear protection layer. By building up residual compressive stresses in the wear protection layer, the wear protection layer can be advantageously clamped to the base body, which ultimately also improves the layer stability and / or the layer quality, particularly the adhesive tensile strength. The adhesive tensile strength of the wear protection layer can be advantageously influenced, in particular, by a decreasing nickel content.

[0049] Furthermore, any microcracks that may occur in the wear-protection layer can be closed by residual compressive stresses within the wear-protection layer, thereby advantageously reducing or preventing any crack growth of the microcracks. Tests have shown that the level of residual stresses observed in a wear-protection layer can increase with increasing chromium content in the wear-protection layer, while it can decrease with increasing nickel content.

[0050] In addition, it is advantageous if the wear protection layer has an outer surface with an arithmetic mean roughness R a of greater than or equal to 0.01 pm, preferably greater than or equal to 0.5 pm and particularly preferably greater than or equal to 1.5 pm, and / or if the wear protection layer has an outer surface with an arithmetic mean roughness R aof less than or equal to 17 pm, preferably of less than or equal to 10 pm and particularly preferably of less than or equal to 6 pm .

[0051] For further advantageous values ​​for the arithmetic mean roughness R a the outer surface of the wear protection layer and the associated properties of the wear protection layer, please refer to Table 3.

[0052] Using the roughness values ​​given here, the roughness R a The wear protection layer of this working roll can be individually adjusted to the requirements of the product to be treated, which in turn determines the roughness R a on the product surface can be determined almost arbitrarily, especially the surface roughness of a strip material. In other words, the factory roughness R a the wear protection layer of the product to be sold.

[0053] The possibility of a specific determination of the surface roughness of a product is particularly advantageous with regard to various product properties, such as the paintability of a product, the haptics of a product, the deep drawing and / or pressing behavior of a product, the adjustability of rolling forces or the like. Tab. 3: Arithmetic mean roughness R a (gm) on the outside of the wear protection layer: adjustability of the roughness of a rolled article, paintability of a rolled article, texture of a rolled article, deep drawing and pressing behavior of a rolled article, adjustability of the rolling forces and porosity of the wear protection layer (evaluation in each case between

[0054] 0 and 10 with the individual scales between smallest possible ( 0 ) and largest possible ( 10 ) ( scale designation : kg) as well as neutral

[0055] ( 0 ) and best possible ( 10 ) ( scale designation : nb ) )

[0056] Furthermore, there is an interaction between the arithmetic mean roughness R a the surface of the wear protection layer and an achievable porosity of the wear protection layer.

[0057] A generic work roll can be advantageously further developed solely by means of the features relating to the arithmetic mean roughness, so that relevant features or combinations of features thereof are already advantageous without the other features of the invention.

[0058] A small value for the arithmetic mean roughness R a the outer surface of the wear protection layer can lead to a better texture of the work roll and a strip material rolled with the work roll and an advantageous adjustability of the rolling forces.

[0059] A mean value (see Table 3) for the arithmetic mean roughness R athe outer surface of the wear protection layer can contribute to optimal conditions for the paintability of a metallic product rolled with the work roll.

[0060] Higher values ​​(see Table 3) for the arithmetic mean roughness R a the outer surface of the wear protection layer can improve the deep drawing and / or pressing behavior as well as the adhesion of a strip coating to the metallic material rolled on the work roll.

[0061] It has been shown that wear protection layers with a low value (see Table 3) for the arithmetic mean roughness R a the outer surface of the wear protection layer contribute to a lower porosity of the wear protection layer, so that at low values ​​for the arithmetic mean roughness R a the adhesive tensile strength of the wear protection layer, which depends on the porosity of the wear protection layer, can also be improved.

[0062] Furthermore, it is advantageous if the wear protection layer has a grain size with a value of greater than or equal to 2 pm, preferably greater than or equal to 5 pm, and / or with a grain size of less than or equal to 50 pm, preferably less than or equal to 45 pm and particularly preferably less than or equal to 30 pm or less than or equal to 20 pm.

[0063] For further advantageous values ​​for the grain size of the wear protection layer and the associated properties of the wear protection layer, please refer to Table 4.

[0064] The term "grain size" in the sense of the invention describes the average diameter or the average area in a micrograph of the crystallites (grains) within a polycrystalline metal. The grain size of the wear protection layer proposed here results in thermal spraying in particular from a particle size of a starting material for providing the coating material for producing the wear protection layer. In particular, the term "grain size" therefore correlates strongly with the particle size of powder particles of a powder for the starting material.

[0065] The term "delamination" describes an unintentional detachment of the wear protection layer from the base body surface.

[0066] The term "element distribution" in the sense of the invention describes the volumetric proportion of hard phase and matrix, whereby the volumetric proportion can be determined, for example, after coating the base body by means of microscopy.

[0067] The term “matrix” or “matrix material” in the sense of the invention is a structure of an applied wear protection layer.

[0068] The matrix of the wear protection layer may contain iron and / or nickel and / or cobalt and / or molybdenum and / or boron and / or

[0069] Wol fram exhibit .

[0070] By using iron as a component of the wear-protection layer matrix, a comparatively cost-effective wear-protection layer matrix can be achieved. This can be particularly advantageous when a work roll's wear-protection layer wears faster than it corrodes.

[0071] By including nickel in the wear-protection layer matrix, the chemical resistance of the wear-protection layer matrix can be improved. Depending on the alloy of the wear-protection layer, a nickel-containing matrix can make the wear-protection layer chemically resistant overall, particularly corrosion-resistant.

[0072] Cobalt as a component of the matrix of a wear-resistant layer can lead to an increase in the temperature resistance of the wear-resistant layer. Cobalt can also advantageously increase the hardness of the matrix and thus of the entire wear-resistant layer. Molybdenum as a component of the matrix can improve the chemical resistance and / or temperature resistance of the wear-resistant layer, especially of the matrix.

[0073] It can also be advantageous for the temperature resistance of the matrix and thus also of the entire wear protection layer if the matrix contains tungsten.

[0074] It has been shown that the adhesive properties of the matrix and thus also of the wear protection layer as such can be improved by boron as a matrix component.

[0075] Furthermore, the matrix of the wear protection layer can also contain manganese, copper, chromium and / or silicon, whereby the matrix of the wear protection layer can be further optimized with regard to its ductility, its hardness, its chemical resistance, its machinability, its friction properties, its temperature resistance, its adhesion strength and / or the like.

[0076] In this context, a "hard phase" is embedded or "floating" embedded in a softer material of the wear protection layer, in particular in a softer matrix or a softer matrix material of the wear protection layer.

[0077] Hard phases suitable for the wear-resistant layer can, in particular, be oxidic, carbide, or boride hard phases, which advantageously exhibit high hardness. For example, a compound of silicon and carbon can be used, which forms silicon carbide (SiC). The term "tensile adhesion strength" describes the resistance to adhesion acting on the wear-resistant layer.

[0078] Adhesion is the adhesive strength of the wear protection layer on the base body of the work roll.

[0079] In this context, the term "cohesion", which will be mentioned later, describes the adhesion capacity of individual layers or coating layers to one another in the wear protection layer.

[0080] The term "phase" here generally describes a state of one or more elements. In particular, an intermetallic phase describes a compound, especially a homogeneous chemical compound, of at least two metals.

[0081] The grain size of the wear-protection layer, in particular the average grain size of a hard phase of the wear-protection layer, in particular the average grain size of the hard phase elements of the wear-protection layer, affects a number of properties of the wear-protection layer. The grain size can be influenced by the process parameters of the thermal spraying of the wear-protection layer, in particular by the average diameter of the powder used.

[0082] Among other things, the grain size can have a beneficial influence on the homogeneity of the wear protection layer, in particular on the homogeneity of the distribution of the coating elements within the wear protection layer, in particular on the distribution of the hard phase elements within the wear protection layer, as well as on the homogeneity of the thickness of the wear protection layer. Tests have shown that the aforementioned homogeneity can be improved with decreasing grain size. Furthermore, the roughness R a , in particular the arithmetic mean roughness R a , the wear protection layer can be influenced. In particular, a smaller grain size can result in a smaller value for the arithmetic mean roughness R a a thermally sprayed and subsequently non-reworked wear protection layer.

[0083] The grain size can influence the residual stress in the wear protection layer. With a smaller grain size, the residual stress in the wear protection layer can increase. It has been shown that higher residual stresses in the wear protection layer can lead to an improvement in tensile adhesive strength, which can also reduce the risk of delamination of the wear protection layer from the base body of the work roll by reducing the grain size. Furthermore, delamination resistance is also influenced by the influence of the grain size on the porosity of the wear protection layer.

[0084] On the other hand, the grain size achieved within a wear-resistant layer during the thermal spraying process can also influence the kinetics of the coating material when applied to the substrate surface, as well as the temperature of the coating material particles. The larger the average powder diameter and thus the larger the grain size of the wear-resistant layer, the lower the particle velocity and the lower the adhesion capacity with constant heat transfer. As a result, the adhesive strength of the wear-resistant layer can also decrease with increasing grain size.

[0085] Tab. 4: Grain size of the wear protection layer (pm): Roughness of the wear protection layer, roughness of a product (strip) machined with the work roll, residual stresses in the wear protection layer and / or the base body, porosity,

[0086] Hardness, number of peaks, homogeneity, in particular homogeneity of the distribution of the coating elements within the wear protection layer as well as homogeneity of the thickness of the wear protection layer, (coating) element distribution, adhesive tensile strength and delamination resistance (each rated between 0 and 10 with the individual scales between smallest possible (0) and largest possible (10) (scale designation: k- g) as well as neutral (0) and best possible (10) (scale designation: n- b)). When thermally spraying a wear protection layer, it has been shown that with increasing average diameter of the powder used and thus with increasing grain size of the wear protection layer, fewer particles of the powder used adhere, which can also affect the homogeneity of the element distribution.

[0087] The higher the thermal energy of the powder particles during thermal spraying of the wear protection layer, the higher the risk of undesirable precipitation of elementary tungsten particles and / or the precipitation of diwolfram carbide W2C.

[0088] In addition to influencing roughness and residual stresses, the grain size can also influence the porosity of the wear protection layer. In particular, a larger grain size can increase the porosity of the wear protection layer, which can reduce the hardness and / or delamination resistance of the wear protection layer.

[0089] Furthermore, the grain size can also influence the number of peaks of a wear protection layer and thus also the roughness of a metallic strip treated with the work roll, whereby the optimum number of peaks can be achieved in a medium range of the grain size considered here, so that the roughness of a metallic strip treated with the work roll can also assume optimum values ​​in a medium range of the grain size considered here.

[0090] A generic work roll can be advantageously further developed solely by means of the features relating to grain size, so that relevant features or combinations of features are already advantageous without the remaining features of the invention. Particularly preferably, the wear-resistant layer has a proportion of tungsten carbide (WC) of greater than or equal to 50 wt. %, preferably a proportion of greater than or equal to 60 wt. %, and particularly preferably greater than or equal to 70 wt.

[0091] In the context of this application, tungsten carbide (WC) is explicitly understood to mean mono-tungsten carbide (WC).

[0092] By including a weight proportion of tungsten carbide in the wear protection layer, particularly as a component of a hard phase of the wear protection layer, the hardness of the wear protection layer can be advantageously increased, whereby an increased proportion of mono-tungsten carbide (WC) in the wear protection layer allows the hardness of the wear protection layer to increase further.

[0093] The wear protection layer can advantageously have a proportion of tungsten carbide (WC) of greater than or equal to 2 wt.%, preferably a proportion of greater than or equal to 20 wt.% and particularly preferably greater than or equal to 25 wt.% or greater than or equal to 30 wt.%. Furthermore advantageously, the wear protection layer can have a proportion of tungsten carbide (WC) of greater than or equal to 40 wt.%, preferably a proportion of greater than or equal to 45 wt.% and particularly preferably greater than or equal to 65 wt.% or greater than or equal to 70 wt.% Particularly advantageously, the wear protection layer can have a proportion of tungsten carbide (WC) of greater than or equal to 75 wt.%, preferably a proportion of greater than or equal to 80 wt.% and particularly preferably greater than or equal to 85 wt.% or greater than or equal to 87 wt.%.

[0094] It is also advantageous if the wear protection layer has a layer thickness with a value of greater than or equal to 2 pm, preferably greater than or equal to 5 pm and particularly preferably greater than or equal to 10 pm, and / or with a layer thickness of less than or equal to 80 pm, preferably less than or equal to 40 pm and particularly preferably less than or equal to 15 pm.

[0095] For further advantageous values ​​for the layer thickness of the wear protection layer and the associated properties of the wear protection layer, please refer to Table 5.

[0096] By using the above-mentioned values ​​for the layer thickness of the wear protection layer, a particularly robust wear protection layer can be achieved.

[0097] It should be noted that thinner layers result in lower cohesive forces. This increases the adhesion of the wear-resistant layer. Tests have shown that this can lead to improved wear behavior, reduced delamination resistance, and increased impact resistance. Particularly small values ​​for the layer thickness of the wear-resistant layer indicate a trend reversal for the delamination resistance and / or impact resistance of the wear-resistant layer.

[0098] The reason for this trend reversal may be the decreasing values ​​for the magnitude of the residual stresses in the wear protection layer resulting from smaller values ​​for the layer thickness of the wear protection layer, since it has been shown that the delamination resistance can increase with increasing values ​​for the residual stresses in the wear protection layer.

[0099] Furthermore, with lower layer thickness values, a more homogeneous distribution of the elements in the wear-resistant layer and an improved distribution of the individual metallurgical phases within the wear-resistant layer can be achieved. Tests have shown that the homogeneity of the distribution of the elements in the wear-resistant layer decreases with increasing layer thickness values.

[0100] With regard to the precipitation of elemental tungsten (W) and / or diwolfram carbide W2C, experiments have shown that this increases with increasing layer thickness. During application of the wear protection layer, a thinner wear protection layer can lead to lower maximum values ​​for the temperature within the wear protection layer, since a thinner wear protection layer can cool down more quickly, both on the side of the base body and on the side of the wear protection layer facing away from the base body. The maximum temperature of the wear protection layer during the thermal spraying process of the wear protection layer favors the precipitation of elemental tungsten (W) and / or diwolfram carbide W2C with increasing values.Furthermore, it was shown that the cooling rate of the wear protection layer during the thermal spraying process of the wear protection layer can reduce the precipitation of elemental tungsten (W) and / or diwolfram carbide W2C with increasing values ​​for the cooling rate.

[0101] Furthermore, it was observed that with increasing values ​​for the layer thickness of the wear protection layer, values ​​for the achievable minimum arithmetic roughness of the surface of the wear protection layer can increase and / or an increasing deterioration of the homogeneity of the thickness distribution of the wear protection layer can result, so that larger values ​​for the layer thickness of the wear protection layer can also contribute to a higher post-processing effort of the wear protection layer until its designated use.

[0102] Tab. 5: Layer thickness of the wear protection layer (pm): Cohesive forces, wear resistance, delamination resistance, element distribution (homogeneity), residual stresses, impact resistance, tungsten precipitation and phase distribution, each of the

[0103] Wear protection layer (rating between 0 and 10 with the individual scales between smallest possible (0) and largest possible (10) (scale designation: kg) as well as neutral (0) and best possible (10) (scale designation: nb))

[0104] Simply by selecting the appropriate thickness of the wear protection layer, a generic work roll can be advantageously further developed, so that relevant features or combinations of features can be achieved without the other

[0105] Features of the invention are advantageous. It is also advantageous if the wear protection layer has an adhesive tensile strength with an adhesive tensile value of greater than or equal to 60 N / mm 2preferably greater than or equal to 70 N / mm 2 , and particularly preferably greater than or equal to 80 N / mm 2 or greater than or equal to 100 N / mm 2 .

[0106] By conducting a tensile adhesion test, it can be determined whether the wear protection layer under test has completely, partially, or not at all chipped off after the test with a tensile force applied in the direction normal to the wear protection layer. Therefore, the tensile adhesion strength is defined as the value for a tensile force at which the wear protection layer has not chipped off at all at the tested location. Accordingly, higher tensile adhesion strength values ​​are advantageous for the delamination resistance of the wear protection layer.

[0107] Furthermore, the wear protection layer advantageously has an adhesive tensile strength with an adhesive tensile value of greater than or equal to 55 N / mm 2 to , preferably greater than or equal to 65 N / mm2 , and particularly preferably greater than or equal to 75 N / mm 2 or greater than or equal to 90 N / mm 2 .

[0108] A generic work roll can be advantageously further developed solely by means of the adhesive tensile strength of the wear protection layer, so that relevant features or combinations of features thereof are already advantageous without the other features of the invention.

[0109] It is also advantageous if the wear-resistant layer has a porosity value of less than or equal to 1%, preferably less than or equal to 0.5%, and particularly preferably less than or equal to 0.1%. For further advantageous values ​​for the porosity of the wear-resistant layer and the associated properties of the wear-resistant layer, reference is made to Table 6.

[0110] The term "porosity" describes the number and / or size of the pores in the wear protection layer, which is expressed as a percentage (%). This number can be determined, for example, by means of an optical evaluation or with the aid of a permeation test, in which the water displacement of the wear protection layer and / or the work roll together with the wear protection layer is examined under the influence of a vacuum.

[0111] Tab . 6 : Porosity of the wear protection layer ( %) : Quality ,

[0112] Corrosion resistance, delamination resistance, surface roughness, hardness, residual stresses and peak count of each wear protection layer (rating between 0 and 10 with individual scales between smallest possible (0) and largest possible (10) (scale designation: kg) as well as neutral (0) and best possible (10) (scale designation: nb))

[0113] Tests have shown that the general quality of the wear protection layer of a work roll with regard to the required properties of a work roll, in particular the corrosion resistance, the delamination resistance and the hardness, can be improved with decreasing porosity of the wear protection layer.

[0114] In particular, the corrosion resistance of the wear protection layer can be improved with decreasing porosity values.

[0115] The adhesive tensile strength or delamination resistance of the wear protection layer can also be positively influenced by smaller values ​​for the porosity of the wear protection layer.

[0116] The hardness of the wear protection layer can also be increased by decreasing the porosity values.

[0117] Small values ​​for the roughness of the outer surface of the wear protection layer can be advantageously achieved, in particular with a low value for the porosity, in particular by the additive application of the wear protection layer by means of a thermal spraying process and / or by the subtractive removal of an outer layer of the wear protection layer.

[0118] Achievable values ​​for residual stress in the wear-protection layer can also be increased by lowering the porosity. It has also been demonstrated that a higher peak count can be achieved with a lower porosity of the wear-protection layer, particularly with an EDT texturing process in which the surface of the wear-protection layer can be textured using spark erosion.

[0119] A generic work roll can be advantageously further developed solely by means of the porosity of the wear protection layer, so that relevant features or combinations of features thereof are already advantageous without the other features of the invention.

[0120] Furthermore, it is advantageous if the wear protection layer has a permeability with a permeability value of less than or equal to 1 Barrer, preferably less than or equal to 0.5 Barrer and particularly preferably less than or equal to 0.1 Barrer.

[0121] For further advantageous values ​​for the permeability of the wear protection layer and the associated properties of the wear protection layer, please refer to Table 7.

[0122] The permeability of the wear protection layer can also influence its quality. For example, better wear protection layer quality can be achieved if the wear protection layer has low permeability, particularly low gas permeability in barriers.

[0123] Tests have shown that the general quality of the wear protection layer of a work roll with regard to the required properties of a work roll, in particular corrosion resistance, delamination resistance and hardness, can be improved with decreasing permeability of the wear protection layer.

[0124] In particular, the corrosion resistance of the wear protection layer can be improved with decreasing permeability values.

[0125] Tab. 7: Permeability of the wear protection layer (Barrer): quality, corrosion resistance, delamination resistance,

[0126] Roughness of the surface, hardness, residual stresses and number of peaks of the wear protection layer (each rated between 0 and 10 with the individual scales between smallest possible (0) and largest possible (10) (scale designation: kg) as well as neutral (0) and best possible (10) (scale designation: nb)). The adhesive tensile strength or delamination resistance of the wear protection layer can also be positively influenced by smaller values ​​for the permeability of the wear protection layer.

[0127] The hardness of the wear protection layer can also be increased with decreasing permeability values.

[0128] The term "permeability" describes the permeability of the wear protection layer, which can be determined primarily by the number of permeable or open pores in the wear protection layer, in particular pores through which gas can flow.

[0129] A generic work roll can be advantageously further developed solely by means of the permeability of the wear protection layer, so that relevant features or combinations of features thereof are already advantageous without the other features of the invention.

[0130] It is advantageous if the wear protection layer has a layer hardness with a layer hardness value of greater than or equal to 800 HV, preferably greater than or equal to 1000 HV and particularly preferably greater than or equal to 1100 HV, and / or with a layer hardness value of less than or equal to 1600 HV, preferably less than or equal to 1500 HV and particularly preferably less than or equal to 1400 HV.

[0131] For further advantageous values ​​for the hardness of the wear protection layer measured in Vickers, which can be measured by means of a macro-identification method, and the associated properties of the wear protection layer, reference is made to Table 8.

[0132] Tab. 8: Layer hardness of the wear protection layer (HV): Wear resistance and adhesive tensile strength of the wear protection layer (each rated between 0 and 10 with the individual scales between smallest possible (0) and largest possible (10) (scale designation: kg) as well as neutral (0) and best possible (10) (scale designation: nb))

[0133] The wear resistance of the wear protection layer can be advantageously influenced or improved by means of the hardness values ​​specified here.

[0134] However, tests have shown that the harder a layer of the wear protection layer is, the lower the adhesive tensile strength of the wear protection layer, especially with regard to adhesion to the base body of the work roll. Furthermore, it should be noted that by selecting the layer hardness, the residual stresses occurring in the wear protection layer can be advantageously influenced, as can the roughness R a the surface of the wear protection layer.

[0135] In particular, the ratio of hard phase to matrix, the precipitation of diwolfram carbide (W2C), the porosity and / or the permeability have an influence on the hardness of the wear protection layer of the work roll.

[0136] Furthermore, interactions between the layer hardness and the number of peaks of the wear protection layer, the porosity of the wear protection layer and the homogeneity of the wear protection layer can be used advantageously.

[0137] Solely by means of the layer hardness selected for the wear protection layer, a generic work roll can be advantageously further developed, so that relevant features or combinations of features thereof are already advantageous without the other features of the invention.

[0138] Furthermore, it is advantageous if the wear protection layer has a deviation of less than or equal to 40% from a weight fraction of a coating element averaged over a total number of analysis points at more than or equal to 80% of a number of analysis points, preferably at more than or equal to 90% of a number of analysis points and particularly preferably at more than or equal to 95% of a number of analysis points, preferably a deviation of less than or equal to 30% and particularly preferably a deviation of less than or equal to 20%, wherein the total number of analysis points is greater than or equal to 5, preferably greater than or equal to 15 and particularly preferably greater than or equal to 25, in particular the coating element is one of the elements tungsten carbide (WC), aluminum oxide (Al2O3), zirconium oxide (ZrO2), chromium carbide (Cr3C2, Cr7C3 and / or Cr 23 C6) or vanadium carbide (VC).

[0139] For further advantageous values ​​for the maximum deviation of a weight fraction of a coating element within the wear protection layer (homogeneity of the distribution of the coating elements) and the associated qualitatively assessed properties of the wear protection layer, please refer to Table 9.

[0140] The properties of the wear protection layer can also be advantageously influenced by the homogeneity of the element distribution.

[0141] By analyzing the homogeneity of the element distribution, the chemical element composition can be determined locally. Both qualitative and quantitative analyses are possible.

[0142] Such determination can be carried out using microanalytical methods, such as "EDX analysis" (Energy Dispersive X-ray Spectroscopy). EDX analysis can be used to advantageously investigate coating compositions. Even unknown materials or contaminants with regard to chemical elements can be analyzed on the existing wear protection layer. Layer thickness measurements of the wear protection layer can also be performed.

[0143] Tab. 9: Homogeneity of the element distribution (qualitative): Homogeneity of the distribution of hard phase to matrix, hardness, porosity, (compressive) residual stress, delamination resistance and homogeneity of the layer thickness of the wear protection layer (evaluation between 0 and 10 with the individual scales between smallest possible (0) and largest possible (10) (scale designation: kg) as well as neutral (0) and best possible (10) (scale designation: nb))

[0144] Overall, it can be stated that the more inhomogeneous a starting material is when fed into the thermal spraying process, the more inhomogeneous the resulting wear-protection layer and thus also the ratio of hard phase to matrix of the wear-protection layer, which influences several properties of the wear-protection layer. The more inhomogeneous the ratio of hard phase to matrix, the lower the usable hardness of the wear-protection layer. Furthermore, with increasing inhomogeneity between hard phase and matrix, more defects occur, which increase the porosity of the wear-protection layer.

[0145] With the homogeneity of the distribution of the coating elements in the wear protection layer, the usable level of the residual stresses occurring in the wear protection layer is also reduced.

[0146] As a result, a decreasing homogeneity of the distribution of the coating elements also leads to a reduction in the adhesive tensile strength of the wear protection layer, which decreases in particular due to an increase in porosity and / or a decrease in a minimum residual stress level.

[0147] Last but not least, an increasing inhomogeneity of the distribution of the coating elements in the wear protection layer can also cause an inhomogeneity of the layer thickness of the wear protection layer.

[0148] Solely by means of the homogeneity of the wear protection layer, a generic work roll can be advantageously further developed, so that relevant features or combinations of features thereof are already advantageous without the other features of the invention.

[0149] Furthermore, properties of the present wear protection layer can be influenced if the wear protection layer has a thickness deviation of less than or equal to 20% of a layer thickness of the wear protection layer averaged over a total number of measuring points at more than or equal to 80% of a number of measuring points, preferably at more than or equal to 90% of a number of measuring points and particularly preferably at more than or equal to 95% of a number of measuring points, preferably a deviation of less than or equal to 10% and particularly preferably a deviation of less than or equal to 5%, wherein the total number of measuring points is greater than or equal to 10, preferably greater than or equal to 25 and particularly preferably greater than or equal to 40.

[0150] Preferably, the wear protection layer has a thickness tolerance of less than or equal to 1 gm, preferably less than or equal to 0.5 gm and particularly preferably less than or equal to 0.2 gm.

[0151] The homogeneity of the layer thickness is a particularly advantageous property of a wear-protection layer. In other words, a surface of a wear-protection layer exhibiting waviness is not generally desirable, but only in special cases. Accordingly, for many work roll designs, a wear-protection layer with a homogeneous thickness and / or only slight thickness deviations is advantageous.

[0152] Preferably, the wear protection layer has a thickness tolerance of less than or equal to 2 gm, preferably less than or equal to 0.75 gm and particularly preferably less than or equal to 0.35 gm.

[0153] By means of the thickness homogeneity proposed here, in particular the roughness R a the wear protection layer and / or the waviness of the wear protection layer can be advantageously influenced.

[0154] A generic work roll can be advantageously further developed solely by means of the design of the thickness homogeneity, so that relevant features or combinations of features are already advantageous without the other features of the invention.

[0155] In addition, it is advantageous if the wear protection layer has a hard phase and a matrix, wherein the hard phase is embedded in the matrix.

[0156] Tests have shown that wear protection layers comprising a hard phase are particularly resistant to wear and thus have an increased service life, especially if at least one hard phase is embedded in a matrix that is softer than the hard phase.

[0157] A hard phase is defined as an inclusion of at least one grain of at least one oxide, one carbide and / or one boride.

[0158] Particularly advantageously, a hard phase comprises tungsten carbide (WC), aluminum oxide (AI2O3), zirconium oxide (ZrO2), chromium carbide (in particular Cr3C2, Cr7C3 and / or Cr 23 C6), vanadium carbide (VC), silicon carbide (SiC), tungsten boride (WB), chromium oxide (in particular CrO, Cr2O3, CrO3 and / or CrO3), titanium carbide (TiC), titanium oxide (in particular TiO, Ti2O3 and / or TiO3) and / or molybdenum carbide (in particular Mo3C and / or MoC).

[0159] Furthermore, it is advantageous if the wear protection layer has a hard phase and a matrix, in particular a ratio of hard phase to an overall layer system consisting of hard phase and matrix with a ratio of greater than or equal to 40 vol.%, preferably greater than or equal to 50 vol.% and particularly preferably greater than or equal to 60 vol.%, and / or in particular with a ratio of hard phase to the overall layer system of less than or equal to 90 vol.%, preferably less than or equal to 85 vol.% and particularly preferably less than or equal to 80 vol.% or less than or equal to 75 vol.%.

[0160] For further advantageous values ​​for the ratio of hard phase to matrix of the wear protection layer and the associated qualitatively assessed properties of the wear protection layer, please refer to Table 10.

[0161] It should be expressly pointed out here that the term "ratio of hard phase to matrix" used here is to be understood in the quantitative sense as the proportion of the hard phase in the wear protection layer, i.e. the ratio of hard phase to the overall layer system consisting of hard phase and matrix.

[0162] The ratio of hard phase / matrix can be used as a measure of the element distribution in the wear protection layer.

[0163] In this respect, it is advantageous if the hard phase and the matrix are present in an optimal ratio to one another, because the more hard phases there are, the higher the hardness of the wear protection layer.

[0164] Furthermore, the higher the hard phase content, the more particles can protrude from the wear protection layer, whereby the roughness R a the surface of the wear protection layer can be influenced.

[0165] On the other hand, the softer the wear protection layer, the denser it is, which in turn can result in a thinner final thickness. The softer the wear protection layer, i.e., the lower the proportion of hard phases, the more particles can adhere to the surface, which can affect the homogeneity of the elements and the homogeneity of the thickness of the wear protection layer.

[0166] Tab. 10: Ratio of hard phase to matrix, i.e. the ratio of hard phase to the total layer system consisting of hard phase and matrix: hardness, roughness R a, density, homogeneity of the element distribution, homogeneity of the layer thickness distribution, number of peaks, tensile strength, residual stresses and porosity of the wear protection layer (each rated between 0 and 10 with the individual scales between smallest possible (0) and largest possible (10) (scale designation: kg) as well as neutral (0) and best possible (10) (scale designation: nb).) Other interactions in connection with the existing ratio of hard phase / matrix can arise in the wear protection layer with regard to the number of peaks, adhesion, residual stresses and / or porosity.

[0167] Solely by means of the ratio of hard phase to the overall layer system consisting of hard phase and matrix, a generic work roll can be advantageously further developed, so that relevant features or combinations of features are already advantageous without the other features of the invention.

[0168] Particularly advantageously, the wear protection layer comprises at least one, two, three, four, five, six, seven or more of the elements tungsten carbide (WC), aluminum oxide (AI2O3), zirconium oxide (ZrO2), chromium carbide (Cr3C2, Cr7C3 and / or Cr 23 C6), vanadium carbide (VC), silicon carbide (SiC), tungsten boride (WB), chromium oxide (CrO, Cr2O3, CrO2 and / or CrO3), titanium carbide (TiC), titanium oxide (TiO, Ti2O3 and / or TiO2) or molybdenum carbide (Mo2C and / or MoC), in particular at least one, two, three, four or more of the elements tungsten carbide (WC), aluminum oxide (Al2O3), zirconium oxide (ZrO2), chromium carbide (Cr3C2, Cr7C3 and / or Cr 23 C6) and / or vanadium carbide (VC).

[0169] In particular, additional coating elements can influence the formation and properties of the existing wear protection layer.

[0170] For example, the properties of all wear protection layers can be influenced with the following coating elements, consisting of tungsten carbide (WC), aluminum oxide (Al2O3), zirconium oxide (ZrO2), chromium carbide (Cr3C2, Cr7C3 and / or Cr 23 C6), vanadium carbide (VC), silicon carbide (SiC), tungsten boride (WB), chromium oxide (CrO, Cr2O3, CrO2 and / or CrO3), titanium carbide (TiC), titanium oxide (TiO, Ti2O3 and / or TiO2) or molybdenum carbide (Mo2C and / or MoC), in particular at least one, two, three, four or more of the elements tungsten carbide (WC), aluminum oxide (Al2O3), zirconium oxide (ZrCt), chromium carbide (Cr3C2, Cr7C3 and / or Cr23Ce) and / or vanadium carbide (VC) in all combinations and compositions.

[0171] The wear protection layer can be further influenced by means of the hard phase and the matrix.

[0172] Depending on the coating elements, the ratio of hard phase to matrix can be advantageously defined, as already described above.

[0173] Different coating elements are generally characterized by different properties, in particular a different hardness, and in this respect one element of the wear protection layer or several elements of the wear protection layer can advantageously influence its hardness as well as other properties of the wear protection layer.

[0174] Furthermore, different coating elements can also influence the residual stresses of the wear protection layer.

[0175] Simply by selecting one or more elements of the wear protection layer, a generic work roll can be advantageously further developed, so that relevant features or combinations of features thereof are already advantageous without the other features of the invention.

[0176] It is also advantageous if the wear protection layer and / or the base body have a residual compressive stress with a value of greater than or equal to -200 N / mm 2 preferably greater than or equal to 0 N / mm 2 and particularly preferably greater than or equal to 200 N / mm 2 , and / or the wear protection layer and / or the base body have a residual compressive stress with a value of less than or equal to 2,000 N / mm 2 preferably less than or equal to 1,500 N / mm 2 and particularly preferably less than or equal to 1,000 N / mm 2 .

[0177] At this point it should first be noted that negative values ​​for a residual stress or a compressive residual stress should be understood as tensile residual stress.

[0178] Using the present values, an improvement in wear resistance on the work roll can be achieved, in particular by a particularly close connection or "clamping" of the wear protection layer on a coated component, such as the base body of the present work roll. In this respect, an improvement in layer adhesion can be achieved by forming the proposed residual compressive stresses.

[0179] Furthermore, crack formation, in particular micro-crack formation, in the wear protection layer can be counteracted by means of suitable residual compressive stresses.

[0180] Furthermore, any microcracks that may occur in the wear-resistant layer can be closed by residual compressive stresses in the wear-resistant layer, which can advantageously reduce or prevent any crack growth of the microcracks. Similarly, residual tensile stresses can promote the growth of microcracks.

[0181] As a rule, layer growth of the wear protection layer is also negatively influenced by unfavourable tensile residual stresses.

[0182] In addition, the adhesive tensile strength of the wear protection layer, the hardness of the wear protection layer and the final layer thickness of the wear protection layer can be influenced both negatively and positively by appropriately provided residual stresses, as can be seen in particular from Table 11 below.

[0183] The present value ranges can be determined in different ways, but preferably using the following methods: "ICP- sensor monitors the curvature by Tsui and Clyne mode" or "Rigaku stress analyzer of model STRAIN-FLEX MSF-2M", where the compressive residual stresses or residual stresses are given in N / mm 2 be measured.

[0184] Tab. 11: Compressive residual stress (N / mm 2): Wear resistance, layer adhesion, layer adhesion and adhesive tensile strength of the wear protection layer (rating in each case between 0 and 10 with the individual scales between smallest possible (0) and largest possible (10) (scale designation: kg) as well as neutral (0) and best possible (10) (scale designation: nb) ) A generic work roll can be advantageously further developed solely by means of the residual stress in the wear protection layer and / or the base body, in particular the residual compressive stress in the wear protection layer and / or the base body, so that relevant features or combinations of features are already advantageous without the other features of the invention.

[0185] Further features, effects and advantages or disadvantages can be found in the following Table 11.

[0186] Furthermore, it is also advantageous if the wear protection layer and / or the base body has a peak number with an RPc value of greater than or equal to 1 / cm, preferably greater than or equal to 30 / cm and particularly preferably greater than or equal to 60 / cm, and / or a peak number with an RPc value of less than or equal to 300 / cm, preferably less than or equal to 250 / cm and particularly preferably less than or equal to 200 / cm.

[0187] By means of the values ​​mentioned here with regard to the number of peaks, a particularly advantageous surface of the wear protection layer can be formed, in particular a particularly advantageous texturing of the surface of the wear protection layer.

[0188] In particular, this can also influence the adhesion between the wear protection layer and the base body.

[0189] However, it should be noted that a high number of peaks on the base body does not directly lead to a high number of peaks on the wear protection layer. Accordingly, the number of peaks on the base body is not the only factor that determines the number of peaks on the wear protection layer. It has been shown that at higher arithmetic mean roughness values ​​R a higher peak numbers can be achieved, whereby even with lower arithmetic mean roughness values ​​R a high peak numbers can be achieved.

[0190] The present number of points has the unit "points / cm". Further information on the number of points can be found in DIN 10049-2014.

[0191] A generic work roll can be advantageously further developed solely by means of the features relating to the number of points, so that relevant features or combinations of features thereof are already advantageous without the other features of the invention.

[0192] Particularly advantageously, the wear protection layer has an oxide content, in particular a content of chromium oxide (CrO, Cr2O2, CrO2 and / or CrO2) and / or aluminum oxide (Al2O2) and / or zirconium oxide (ZrO2) and / or titanium oxide (TiO, Ti2O2 and / or TiO2), of less than or equal to 5 wt.%, preferably of less than or equal to 3 wt.% and particularly preferably of less than or equal to 1.5 wt.%.

[0193] Smaller values ​​for the oxide content can be achieved, among other things, by the thermal spraying device having a lambda value of close to one or one.

[0194] Tests have shown that an increasing value for the oxide content can reduce the service life of the wear protection layer and / or, in the case of a multi-layered wear protection layer structure, can negatively influence the adhesion of adjacent layers.

[0195] It has also proven advantageous if the base body has an outer surface to be coated with an arithmetic mean roughness R a of greater than or equal to 0.1 pm, preferably greater than or equal to 0.2 pm and particularly preferably greater than or equal to 0.3 pm, and / or an arithmetic mean roughness R a of less than or equal to 14 pm, preferably less than or equal to 4.0 pm and particularly preferably less than or equal to 0.8 pm.

[0196] Using the roughness R a The wear protection layer can also be advantageously influenced by the base body surface, such as the final roughness R a of the wear protection layer, and also its homogeneity. It can be assumed that the higher the roughness R a of the material to be coated (base body), the higher the roughness R athe surface of the wear protection layer; and the higher the roughness R a of the material to be coated (base body), the greater the deviation in the layer thickness, which can also negatively influence the homogeneity of the layer thickness of the wear protection layer.

[0197] The particle adhesion and thus also the layer adhesion with regard to the wear protection layer on the base body surface can also be influenced by the roughness of the base body surface.

[0198] Roughnesses R mentioned here a regarding the base body surface can be produced differently, whereby several of the specified roughnesses R a can be achieved by grinding the surface of the work roll, such as roughness R a from 0.3 pm to 0.8 pm.

[0199] Further features, effects, advantages, and disadvantages can be found in the following Table 12:

[0200] Tab. 12: Average roughness R a (pm) of the wear protection layer: layer roughness, layer thickness, homogeneity of the wear protection layer, residual stresses of the wear protection layer and adhesive tensile strength of the wear protection layer (each rated between 0 and 10 with the individual scales between smallest possible (0) and largest possible (10) (scale designation: kg) as well as neutral (0) and best possible (10) (scale designation: nb) )

[0201] Solely by means of the characteristics regarding the arithmetic mean roughness R a a generic work roll can be advantageously further developed so that relevant features or combinations of features are already advantageous without the other features of the invention.

[0202] It has also been found to be expedient if the base body has a base body hardness with a hardness value of greater than or equal to 35 HRC, preferably greater than or equal to 40 HRC and particularly preferably greater than or equal to 50 HRC and / or a base body hardness with a hardness value of less than or equal to 70 HRC, preferably less than or equal to 65 HRC and particularly preferably less than or equal to 60 HRC.

[0203] By means of the additional hardness values ​​specified here with regard to the base body, the layer adhesion of the wear protection layer to the base body of the work roll can be advantageously influenced or adjusted.

[0204] If the base body hardness is set too soft, components of the wear-resistant coating may penetrate the base body, causing damage. If the base body hardness is too hard, there is a risk that a critical number of components of the coating material will rebound from the base body when applied.

[0205] Furthermore, the following should be noted with regard to the base body hardness:

[0206] The harder the base body, the lower the adhesive tensile strength of the wear protection layer, which means that the wear protection layer is more likely to detach from the base body.

[0207] The harder the base body is designed, the higher the risk that more defects will occur in the base body-wear protection layer composite, which in turn can increase the risk of delamination.

[0208] Further features, effects, advantages, and disadvantages can be seen in the following Table 13:

[0209] Tab. 13: Base body hardness (HRC): porosity, defect frequency, adhesive tensile strength, residual stresses and layer thickness of the wear protection layer (each rated between 0 and 10 with the individual scales between smallest possible (0) and largest possible (10) (scale designation: kg) as well as neutral (0) and best possible (10) (scale designation: nb))

[0210] Such defects usually also increase the porosity, which can also negatively affect the adhesion between the wear protection layer and the base body.

[0211] In addition, defects can in turn influence the residual stresses in the wear protection layer, and vice versa.

[0212] Furthermore, adhesion mechanisms in the spraying process can influence the roughness and the layer thickness of the wear protection layer. The harder the wear protection layer, the more the roughness R a the surface of the wear protection layer.

[0213] The existing base body hardness HRC is preferably measured using a macro identification method.

[0214] A generic work roll can be advantageously further developed solely by means of the features relating to the base body hardness, so that relevant features or combinations of features thereof are already advantageous without the other features of the invention.

[0215] Furthermore, further configurations of the base body can have an advantageous effect on the anti-closure layer, such as the material from which the base body is made.

[0216] Selected dimensions regarding the base body, such as in particular the width of the base body, the diameter of the base body, the length of the base body, but also the support distance between bearing points of the base body can affect the quality of the wear protection layer.

[0217] In any case, by means of the above-mentioned features, a work roll for rolling a metallic product, in particular a wear protection layer thereof, can be advantageously adapted to different individual requirements, taking into account legal requirements for the avoidance of hard chromium.

[0218] According to a further aspect, the object of the invention is also achieved by a rolling stand comprising a work roll according to one of the features described here. The object of the invention is also achieved by a metallic strip, wherein the metallic strip is cold-rolled with a work roll according to one of the features described here.

[0219] Advantageously, certain features of the wear-resistant layer can be identified based on the surface pattern obtained on the metallic strip. In particular, the texturing of the wear-resistant layer of the work roll can be transferred from the surface of the work roll, in particular the surface of the wear-resistant layer, to the surface of the metallic strip during rolling of a metallic strip.

[0220] The object of the invention is also achieved by a method for producing the present work roll, in which the wear protection layer is applied to a previously provided base body using a thermal spraying process.

[0221] In this way, the working roll can be advantageously manufactured with the wear protection layer.

[0222] In particular, using a thermal spraying process, even different powder compositions can be applied easily and precisely to the base body of the work roll to create process-specific wear protection layers.

[0223] The wear protection layer can be further adjusted to suit the application by abrasively smoothing it after application. For example, this allows the surface roughness of the wear protection layer to be further adjusted on the working roll.

[0224] In particular, such a process can be advantageously further developed by increasing the number of powder conveyors, which allows for a more homogeneous powder distribution. This also allows the quality of the wear-resistant coating on the working roll to be further improved.

[0225] At this point, it should also be claimed that the described method can also be supplemented by further technical features mentioned here, in particular by features of the present work roll or its wear protection layer, in order to advantageously further develop the method or to be able to represent or formulate method specifications even more precisely.

[0226] Preferably, powder conveyors can be arranged above a burner for thermal spraying of the wear protection layer (e.g. High Velocity Oxygen Fuel (HVOF burner) or High Velocity Air Fuel (HVAF burner)), whereby the static pressure for introducing the powder into the burner can be expediently increased.

[0227] Furthermore, it may be advantageous for the design of the present wear protection layer if, with regard to powder preparation, any powders for producing the wear protection layer are preheated.

[0228] Additional sieving of powder can ensure a more homogeneous powder distribution.

[0229] Likewise, the production of the wear protection layer can be advantageously influenced by appropriate preheating or sieving of powder, particularly with regard to crowning / strip dimensions in order to optimize residual stresses with regard to the wear protection layer.

[0230] The object of the invention is further achieved by a work roll according to one of the features described here for cold rolling a metallic strip. By using the present work roll, high-quality surfaces can be reliably produced on the cold-rolled metallic strip, particularly over a longer period of time.

[0231] The above-mentioned measures, in particular the selection of the coating material and in particular the selection of more complex coating parameters, can contribute significantly to providing high-quality wear protection layers for rolling a metallic strip.

[0232] Further advantages, details and features of the invention will become apparent from the exemplary embodiment explained below.

[0233] The drawing shows:

[0234] Figure 1: schematically shows a view of a work roll for rolling a metallic product during thermal spraying of the wear protection layer onto a base body of a work roll for rolling metallic products; and

[0235] Figure 2: schematically shows a partially sectioned view of a section of the working roll from Figure 1.

[0236] Figure 1 schematically illustrates the production of a work roll 1 for rolling a metallic material (not shown), in particular for rolling a metallic strip (also not shown). The work roll 1 is processed by thermal spraying. More specifically, a wear-resistant layer 2 is applied to the surface 3 of a base body 4 of the work roll 1.

[0237] The thermal spraying of the wear protection layer 2 is carried out by means of a suitable device 5 for thermal spraying, which has a burner 6, such as an HVOF burner or an HVAF burner, wherein above the burner 6 a plurality of powder conveyors 7 (shown and numbered only as an example) are arranged, at least some of which can preheat the powder 8.

[0238] The powder 8 can be individually mixed together by a plurality of powder components 9, as claimed in the sense of the invention.

[0239] The powder conveyors 7 also have a device 10 for sieving the powder 8 or powder components 9 thereof.

[0240] By means of the device 5 for thermal spraying, a particularly advantageously composed coating material 11 can be applied to the base body 4 of the working roller 1, while the latter rotates about its bearing axis 12 in the direction of rotation 12.

[0241] According to the illustration in Figure 2, a section of the working roll 1 is shown as a sectional detailed view in the interface area 20 between the wear protection layer 2 and the base body 4.

[0242] In particular, the peaks 22 of the roughness (not numbered again) of the interface 24 of the base body surface 3 are clearly visible, with the peaks 22 also forming cavities 26 on the base body surface 3. In particular, thermal spraying or deposition can achieve a higher number of peaks on the wear protection layer than the number of peaks on the base body (not directly shown). Furthermore, thermal spraying or deposition can achieve a higher roughness of the wear protection layer than the roughness on the base body (not shown).

[0243] Peaks 22 and cavities 26 form the roughness of the interface 24, which is illustrated as a jagged line (not numbered again).

[0244] The wear protection layer 2 has hard phase particles 28 (dashed structures) comprising tungsten carbide (WC) (not numbered again), which are embedded in a matrix 30 of the wear protection layer 2.

[0245] During thermal spraying of the wear protection layer 2, some tungsten precipitates 28A (black particles) consisting of ditungsten carbide (W2C) (not separately numbered again) or elemental tungsten (W) (also not separately numbered again) were formed in the wear protection layer 2.

[0246] It is clearly visible how, in particular, the hard phase particles 28 are arranged in a pressed-in manner in the cavities 26 and in this case partially lie frictionally on the flanks 32 of the tips 22 over a large area.

[0247] Higher compressive residual stresses may prevail in the interface region 20 than further away from the interface region 20.

[0248] By setting correspondingly high residual compressive stresses, the wear protection layer 2 is pressed more strongly against the base body 2, in particular more strongly into the cavities 26, whereby hard phase particles 28 of the wear protection layer 2 also interact much more intimately with the flanks 32. Overall, by means of residual compressive stresses, in particular between 500 N / mm2 and 1,500 N / mm2, a particularly intimate bond between the wear protection layer 2 and the base body 4 and thus also particularly good adhesive tensile strength can be ensured.

[0249] Even hard phase particles 28 within the matrix 30 can “clamp” together more closely with such residual compressive stresses.

[0250] List of reference symbols

[0251] 1 working roller

[0252] 2 Wear protection layer

[0253] 3 Surface

[0254] 4 basic bodies

[0255] 5 Device for thermal spraying

[0256] 6 powder for order

[0257] 7 Sieving device

[0258] 8 powders

[0259] 9 powder ingredients

[0260] 10 Sieving device

[0261] 11 Coating material

[0262] 12 Direction of rotation

[0263] 20 Interface area

[0264] 22 peaks

[0265] 24 Interface

[0266] 26 cavities

[0267] 28 hard phase particles

[0268] 28A W-precipitates (diwolframcarbide (W2C) or wolfram (W))

[0269] 30 Matrix

[0270] 32 flanks

Claims

Patent claims 1. A work roll (1) for rolling a metallic material, in particular for rolling a metallic strip, comprising: a base body (4) made of metal; and a wear protection layer (2) arranged at least in regions on the base body (4), wherein the wear protection layer (2) is a thermal splash protection layer; characterized in that the wear protection layer (2) has a proportion of tungsten carbide (WC) of greater than or equal to 10 wt.% and a proportion of ditungsten carbide (W2C) (28A) of less than or equal to 50 wt.%, preferably less than or equal to 33 wt.% and particularly preferably less than or equal to 10 wt.% or less than or equal to 5 wt.%.

2. Work roll (1) according to claim 1, characterized in that the wear protection layer (2) has a proportion of elemental tungsten (W) (28A) of less than or equal to 50 wt.%, preferably less than or equal to 33 wt.% and particularly preferably less than or equal to 10 wt.% or less than or equal to 5 wt.%.

3. Work roll (1) according to one of claims 1 or 2, characterized in that the wear protection layer (2) has a chromium content of less than or equal to 90 wt.%, preferably less than or equal to 60 wt.% and particularly preferably less than or equal to 30 wt.%.

4. Work roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) has a nickel content of less than or equal to 90 wt.%, preferably less than or equal to 60 wt.% and particularly preferably less than or equal to 30 wt.%.

5. Working roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) has an outer surface with an arithmetic mean roughness R a of greater than or equal to 0.01 pm, preferably greater than or equal to 0.5 pm and particularly preferably greater than or equal to 1.5 pm, and / or having an arithmetic mean roughness R a of less than or equal to 17 pm, preferably less than or equal to 10 pm and particularly preferably less than or equal to 6 pm.

6. Work roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) has a grain size with a value of greater than or equal to 2 pm, preferably greater than or equal to 5 pm, and / or with a grain size of less than or equal to 50 pm, preferably less than or equal to 45 pm and particularly preferably less than or equal to 30 pm or less than or equal to 20 pm.

7. Work roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) has a proportion of tungsten carbide (WC) of greater than or equal to 50 wt. %, preferably a proportion of greater than or equal to 60 wt. % and particularly preferably of greater than or equal to 70 wt. %.

8. Work roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) has a layer thickness with a value of greater than or equal to 2 pm, preferably greater than or equal to 5 pm and particularly preferably greater than or equal to 10 pm, and / or with a layer thickness of less than or equal to 80 pm, preferably less than or equal to 40 pm and particularly preferably less than or equal to 15 pm.

9. Working roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) has an adhesive tensile strength with an adhesive tensile value of greater than or equal to 60 N / mm 2 preferably greater than or equal to 70 N / mm 2 , and particularly preferably greater than or equal to 80 N / mm 2 or greater than or equal to 100 N / mm 2 .

10. Work roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) has a porosity with a porosity value of less than or equal to 1%, preferably less than or equal to 0.5% and particularly preferably less than or equal to 0.1%.

11. Work roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) has a permeability with a permeability value of less than or equal to 1%, preferably less than or equal to 0.5% and particularly preferably less than or equal to 0.1%.

12. Work roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) has a layer hardness with a layer hardness value of greater than or equal to 800 HV, preferably greater than or equal to 1000 HV and particularly preferably greater than or equal to 1100 HV, and / or with a layer hardness value of less than or equal to 1600 HV, preferably less than or equal to 1500 HV and particularly preferably less than or equal to 1400 HV.

13. Work roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) has a deviation of less than or equal to 40% from a weight fraction of a coating element averaged over a total number of analysis points, preferably a deviation of less than or equal to 30% and particularly preferably a deviation of less than or equal to 20%, at more than or equal to 80% of a number of analysis points, preferably at more than or equal to 90% of a number of analysis points and particularly preferably at more than or equal to 95% of a number of analysis points, wherein the total number of analysis points is greater than or equal to 5, preferably greater than or equal to 15 and particularly preferably greater than or equal to 25, in particular the coating element is one of the elements tungsten carbide (WC), aluminum oxide (AI2O3), zirconium oxide (ZrO2), chromium carbide (Cr3C2, Cr7C3 and / or Cr23C6) or vanadium carbide (VC).

14. Work roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) has a thickness deviation of less than or equal to 20% of a layer thickness of the wear protection layer (2) averaged over a total number of measuring points, preferably a deviation of less than or equal to 10% and particularly preferably a deviation of less than or equal to 5%, at more than or equal to 80% of a number of measuring points, preferably at more than or equal to 90% of a number of measuring points and particularly preferably at more than or equal to 95% of a number of measuring points, wherein the total number of measuring points is greater than or equal to 10, preferably greater than or equal to 25 and particularly preferably greater than or equal to 40.

15. Work roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) has a thickness tolerance of less than or equal to 1 pm, preferably less than or equal to 0.5 pm and particularly preferably less than or equal to 0.2 pm.

16. Work roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) has a hard phase and a matrix, wherein the hard phase is embedded in the matrix.

17. Work roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) has a hard phase and a matrix, in particular a ratio of hard phase to a total layer system consisting of hard phase and matrix with a ratio of greater than or equal to 40 vol.%, preferably greater than or equal to 50 vol.% and particularly preferably greater than or equal to 60 vol.%, and / or in particular with a ratio of Hard phase to the total layer system of less than or equal to 90 vol.%, preferably less than or equal to 85 vol.% and particularly preferably less than or equal to 80 vol.% or less than or equal to 75 vol.%.

18. Work roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) comprises at least one, two, three, four, five, six, seven or more of the elements tungsten carbide (WC), aluminum oxide (Al2O3), zirconium oxide (ZrO2), chromium carbide (Cr3C2, Cr7C3 and / or Cr23C6), vanadium carbide (VC), silicon carbide (SiC), tungsten boride (WB), chromium oxide (CrO, Cr2O3, CrO2 and / or CrO3), titanium carbide (TiC), titanium oxide (TiO, Ti2O3 and / or TiO2) or molybdenum carbide (Mo2C and / or MoC), in particular at least one, two, three, four or more of the elements tungsten carbide (WC), aluminum oxide (Al2O3), zirconium oxide (ZrO2), chromium carbide (Cr3C2, Cr7C3 and / or Cr23Ce) and / or vanadium carbide (VC).

19. Working roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) and / or the base body (4) has a residual compressive stress with a value of greater than or equal to -200 N / mm 2preferably greater than or equal to 0 N / mm 2 and particularly preferably greater than or equal to 200 N / mm 2 , and / or the wear protection layer (2) and / or the base body (4) has a residual compressive stress with a value of less than or equal to 2,000 N / mm 2 preferably less than or equal to 1,500 N / mm 2 and particularly preferably less than or equal to 1,000 N / mm 2 .

20. Work roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) and / or the base body (4) has a peak number with an RPc value of greater than or equal to 1 / cm, preferably greater than or equal to 30 / cm and particularly preferably greater than or equal to 60 / cm, and / or a peak number with an RPc value of less than or equal to 300 / cm, preferably less than or equal to 250 / cm and particularly preferably less than or equal to 200 / cm.

21. Work roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) has an oxide content, in particular a content of aluminum oxide (Al2O3) and / or zirconium oxide (ZrO2) and / or chromium oxide (CrO, Cr2O3, CrO2 and / or CrO3) and / or titanium oxide (TiO, Ti2O3 and / or TiO2), of less than or equal to 5 wt.%, preferably of less than or equal to 3 wt.% and particularly preferably of less than or equal to 1.5 wt.%.

22. Working roll (1) according to one of the preceding claims, characterized in that the base body (4) has an outer side to be coated with an arithmetic mean roughness R a of greater than or equal to 0.1 pm, preferably greater than or equal to 0.2 pm and particularly preferably greater than or equal to 0.3 pm, and / or an arithmetic mean roughness R aof less than or equal to 14 pm, preferably less than or equal to 4.0 pm and particularly preferably less than or equal to 0.8 pm.

23. Work roll (1) according to one of the preceding claims, characterized in that the base body (4) has a base body hardness with a hardness value of greater than or equal to 35 HRC, preferably greater than or equal to 40 HRC and particularly preferably greater than or equal to 50 HRC and / or a base body hardness with a hardness value of less than or equal to 70 HRC, preferably less than or equal to 65 HRC and particularly preferably less than or equal to 60 HRC.

24. Roll stand comprising a work roll (1) according to one of claims 1 to 23.

25. A metallic strip, wherein the metallic strip is cold rolled with a work roll (1) according to one of claims 1 to 23.

26. A method for producing a work roll (1) according to one of claims 1 to 23, comprising the following steps: Providing the base body (4); and Application of the wear protection layer (2) using a thermal spraying process.

27. Method according to claim 26, characterized in that the wear protection layer (2) is abrasively smoothed after application.

28. Use of a work roll (1) according to one of claims 1 to 23 for cold rolling a metallic strip.

Images