WO2024240646A1 - Working roll for rolling a metallic item, roll stand, metallic strip, method for producing a working roll, and use of a working roll - Google Patents

Abstract

The invention relates to a working roll (1) for rolling a metallic item, in particular for rolling a metallic strip, comprising: - a main body (4) made of metal; and - an antiwear layer (2) at least partially applied to the main body, wherein: the antiwear layer is a thermal sprayed coating; and the antiwear layer has a chrome proportion of smaller than or equal to 90 wt.%, preferably smaller than or equal to 60 wt.%, and especially preferably smaller than or equal to 30 wt.%.

Description

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

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.

The invention further relates to a rolling stand.

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

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

The invention also relates to a use of a work roll.

Generic work rolls or methods for producing such work rolls are known from the prior art.

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 at the same time it can be possible to create a defined surface texture on a tape.

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 a high load in a rolling process can also show various wear characteristics.

As a rule, a suitable wear protection layer comprises a hard chrome coating, which, however, also tends to form microcracks, which in turn can have a negative effect on the service life and corrosion resistance. In the production of the previously known wear protection layers made of chrome, in particular in the production of hard chrome layers, a hexavalent chromium (Cr-6) has been used up to now. It is now considered proven that Cr-6 is carcinogenic and/or mutagenic.

There are different methods for applying a wear protection layer to a working roll.

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

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, having 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, wherein the wear protection layer 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. %. For further advantageous values for the chromium content of the wear protection layer and the related properties of the wear protection layer, please refer to Table 1.

The present wear protection layer serves to protect the working roll from wear.

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

On the other hand, the risk of critical carcinogenic and/or mutagenic interactions with living beings, in particular workers or operating personnel, can be excluded or at least significantly reduced.

The wear protection layer proposed here enables the work roll, but especially the wear protection layer itself, to be provided as freely as possible, preferably entirely, without the 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 other improved properties of the work roll, as described in more detail below.

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 for as long as possible, such as in particular the roughness and texture or smoothness of a producing metallic material surface, in particular of a metallic strip to be produced.

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

It should also be noted here that, in the context of the patent application at hand, indefinite articles and indefinite numerical statements such as "one...", "two...", etc. are generally to be understood as at least statements, 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.

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 indeed" or "namely".

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.

For further advantageous values for the nickel content of the wear protection layer and the related properties of the wear protection layer, please refer to Table 1. Further features, effects or advantages or disadvantages can be found in the following Table 1:

Tab. 1: Chromium and/or nickel content (wt.%) : residual compressive stresses and wear resistance (evaluation 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) )

As can be seen from Table 1, the wear resistance of the wear protection layer can be improved with a higher chromium content and/or a lower nickel content, whereby mutagenic and/or carcinogenic effects on the environment can be reduced by smaller Chromium content and smaller nickel content can be improved or avoided.

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 is always understood to mean compressive residual stress, unless this is explicitly stated otherwise.

The wear resistance of the wear protection layer can also be supported 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, in particular the adhesive tensile strength. The adhesive tensile strength of the wear protection layer can be advantageously influenced, in particular, by a decreasing nickel content.

Furthermore, any microcracks that may occur in the wear protection layer can be closed again by residual compressive stresses in the wear protection layer, whereby any crack growth of the microcracks can be advantageously reduced or prevented.

Tests have shown that the level of residual stresses observable in a wear protection layer can increase with increasing chromium content in the wear protection layer, while it can decrease with increasing nickel content in the wear protection layer. Furthermore, 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 gm, preferably greater than or equal to 0.5 gm and particularly preferably greater than or equal to 1.5 gm, and/or if the wear protection layer has an outer surface with an arithmetic mean roughness R _a of less than or equal to 17 gm, preferably less than or equal to 10 gm and particularly preferably less than or equal to 6 gm.

Tab . 2 : Arithmetic mean roughness R _a (gm) on the outside of the wear protection layer : Adjustment of the roughness of a rolled article, paintability of a rolled article, texture of a rolled article, deep drawing and pressing behaviour of a rolled article, adjustability of the rolling forces 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 ) )

For further advantageous values for the arithmetic mean roughness R _a of the outer surface of the wear protection layer and the related properties of the wear protection layer, please refer to Table 2.

Using the roughness values given here, the roughness R _a of the wear protection layer of the present work roll can be individually adjusted to the requirements of the product to be treated with it, which in turn allows the roughness R _a on the product surface to be determined almost arbitrarily, in particular the surface roughness of a strip material. In other words, the factory roughness R _a of the wear protection layer of the product to be sold can be adjusted in this way.

The possibility of a specific determination of a surface roughness of a product is particularly advantageous with regard to various product properties, such as the paintability of a product, the feel of a product, the deep-drawing and/or pressing behavior of a product, the adjustability of rolling forces or the like.

Furthermore, there is an interaction between the arithmetic mean roughness R _a of the surface of the wear protection layer and an achievable porosity of the wear protection layer . A generic work roll can be advantageously further developed solely by means of the features relating to the arithmetic mean roughness value, so that relevant features or combinations of features thereof are already advantageous without the other features of the invention.

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

An average value (cf. Table 2) for the arithmetic mean roughness R _a of the outer surface of the wear protection layer can contribute to optimal conditions for the paintability of a metallic product rolled with the work roll.

Higher values (see Table 2) for the arithmetic mean roughness R _{a of} the outer surface of the wear protection layer can improve deep drawing and/or pressing behavior as well as the adhesion of a strip coating to the metallic material rolled on the work roll.

It has been shown that wear protection layers with a low value (cf. Table 2) for the arithmetic mean roughness R _a of the outer surface of the wear protection layer contribute to a lower porosity of the wear protection layer, so that with 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.

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 having 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 gm or less than or equal to 20 gm.

For further advantageous values for the grain size of the wear protection layer and the related properties of the wear protection layer, please refer to Table 3.

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 size of particles 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.

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

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.

The term "matrix" or "matrix material" in the sense of the invention is a structure of a deposited wear

protective layer . The matrix of the wear protection layer may comprise iron and/or nickel and/or cobalt and/or molybdenum and/or boron and/or tungsten.

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 if a work roll's wear protection layer wears out faster than it corrodes.

By using nickel as a component of the matrix of the wear protection layer, the chemical resistance of the matrix of the wear protection layer can be improved. Depending on the alloy of the wear protection layer, a matrix containing nickel can ensure that the wear protection layer is chemically resistant overall, and in particular is corrosion resistant.

Cobalt as a component of the matrix of a wear protection layer can lead to an increase in the temperature resistance of the wear protection layer. Cobalt can also advantageously be used to increase the hardness of the matrix and thus of the entire wear protection layer.

By using molybdenum as a component of the matrix, the chemical resistance and/or the temperature resistance of the wear protection layer, in particular of the matrix, can be improved.

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. 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 using boron as a matrix component.

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 resistance and/or the like.

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.

Hard phases suitable for the wear protection layer can in particular be oxidic, carbide or boride hard phases, which advantageously have a high hardness. For example, a compound of silicon and carbon can be used, which forms silicon carbide (SiC).

The term “adhesive tensile strength” describes the resistance to adhesion acting on the wear protection layer.

Adhesion is the adhesive capacity of the wear protection layer on the base body of the working roll.

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

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 via the average diameter of the powder used.

Among other things, the grain size can have a beneficial effect 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 homogeneity mentioned above can be improved with decreasing grain size.

Furthermore, the roughness R _a , in particular the arithmetic mean roughness R _a , of the wear protection layer can be influenced by means of the grain size. In particular, a smaller value for the arithmetic mean roughness R _a of a thermally sprayed and subsequently not reworked wear protection layer can be achieved with a smaller grain size.

The grain size can influence the residual stress in the wear protection layer, whereby the residual stress in the wear protection layer can be increased with smaller grain size It has been shown that higher residual stresses in the wear protection layer can lead to an improvement in the adhesive tensile strength, whereby the risk of delamination of the wear protection layer from the base body of the work roll can be reduced on the one hand by a decreasing grain size.

Furthermore, the delamination resistance is also influenced by the influence of the grain size on the porosity of the wear protection layer.

Tab. 3: 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, hardness, number of peaks, homogeneity, in particular homogeneity of the distribution of the coating elements within the wear Protective layer as well as homogeneity of the thickness of the wear protection layer, (coating) element distribution, adhesive strength and delamination resistance (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 ) )

On the other hand, the grain size achieved within a wear protection layer can also influence the kinetics of the coating material when applied to the base body surface during the thermal spraying process, as well as the temperature of the particles of the coating material. The larger the average powder diameter and thus the larger the grain size of the wear protection layer, the lower the particle speed and the lower the adhesion capacity with constant heat transfer, which can also cause the adhesive tensile strength of the wear protection layer to decrease again with increasing grain size.

During thermal spraying of 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.

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 ditungsten carbide W ₂ C .

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 increase the porosity of the wear protection layer, which may reduce the hardness and/or delamination resistance of the wear protection layer.

Furthermore, the grain size can also influence the number of peaks of a wear protection layer and, associated with this, 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.

A generic work roll can be advantageously further developed solely by means of the features relating to the grain size, so that relevant features or combinations of features are already advantageous without the other features of the invention.

Particularly preferably, the wear protection 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 of greater than or equal to 70 wt. %.

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

By means of a weight proportion of tungsten carbide in the wear protection layer, in particular 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. 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.

The wear protection layer can be further improved if the wear protection layer has a proportion of tungsten precipitates, in particular of elemental tungsten (W) and/or ditungsten carbide (W ₂ C), with a proportion 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. %.

For further advantageous values for the weight fraction of tungsten precipitates in the wear protection layer and the related properties of the wear protection layer, please refer to Table 4.

Tungsten precipitates in the form of elemental tungsten (W) and/or ditungsten carbide (W ₂ C) can be formed by degradation of tungsten carbide (WC).

Tab. 4: Tungsten precipitates (elemental tungsten and/or ditungsten carbide W ₂ C) 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 (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))

Tungsten precipitates in the wear protection layer, particularly in the form of elemental tungsten (W) and/or ditungsten carbide (W ₂ C), can contribute to embrittlement of the wear protection layer, whereby 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 can be reduced with an increasing proportion of tungsten precipitates. Overall, a higher proportion of tungsten precipitates in the wear protection layer can therefore reduce its service life. 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.

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.

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

Solely by means of the proportion of tungsten precipitates, in particular the precipitates of elemental tungsten (W) and/or ditungsten carbide (W ₂ C ), 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.

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

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

It should be noted that thinner layers lead to lower cohesive forces. This increases the adhesion effect of the wear protection layer. Tests have shown that this can lead to better wear behavior, reduced delamination resistance and increased impact resistance, with particularly small values for the layer thickness of the wear protection layer showing a trend reversal for the delamination resistance and/or the impact resistance of the wear protection layer.

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.

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

Tab . 5 : Schichtdicke der Verschleißschutzschicht (pm) : Kohäsionskräfte , Verschleißresistenz , Delaminationsbeständigkeit , Elementenverteilung (Homogenität ) , Eigenspannungen, Schlagfestigkeit , Wol fram-Ausscheidung und Phasenverteilung, j eweils der Verschleißschutzschicht (Bewertung j eweils zwischen 0 und 10 mit den individuellen Skalen zwischen kleinstmöglich ( 0 ) und größtmöglich ( 10 ) ( Skalenbezeichnung : k-g) sowie neutral ( 0 ) und bestmöglich ( 10 ) ( Skalenbezeichnung : n-b ) ) With regard to the precipitation of elemental tungsten (W) and/or ditungsten carbide W ₂ C, experiments have shown that these increase with increasing layer thickness. During the 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 process of thermal spraying of the wear protection layer promotes the precipitation of elemental tungsten (W) and/or diwolfram carbide W ₂ C with increasing values for the cooling rate. It has also been shown that the rate of cooling of the wear protection layer during the process of thermal spraying of the wear protection layer can reduce the precipitation of elemental tungsten (W) and/or diwolfram carbide W ₂ C with increasing values for the cooling rate.

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

Furthermore, it could be 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.

Simply by a suitable selection of the layer thickness of the wear protection layer, 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.

It is further 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 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 .

When carrying out an adhesion tensile test, it can be determined whether the wear protection layer under test has a tensile strength in the normal direction to the wear protection layer after the test. has completely, partially or not at all flaked off under the applied tensile force. Therefore, the tensile adhesive strength is understood to be the value for a tensile force at which the wear protection layer has not flaked off at all at the point under investigation. Accordingly, higher values for the tensile adhesive strength are advantageous for the delamination resistance of the wear protection layer.

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

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 are already advantageous without the other features of the invention.

In addition, it is advantageous if the wear protection layer 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%.

For further advantageous values for the porosity of the wear protection layer and the related properties of the wear protection layer, please refer to Table 6.

Tab. 6: Porosity of the wear protection layer (%): quality, corrosion resistance, delamination resistance, surface roughness, hardness, residual stresses and peak number of the wear protection layer (each rating between 0 and 10 with the individual scales between smallest possible (0) and largest possible (10) (scale designation: kg) and neutral (0) and best possible (10) (scale designation: nb)). The term "porosity" describes the number and/or size of the pores in the wear protection layer, which is given in percent (%). This number can be determined, for example, by means of an optical evaluation or with the help 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. 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 porosity of the wear protection layer.

In particular, the corrosion resistance of the wear protection layer can be improved by decreasing the porosity values.

The adhesive 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.

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

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.

Achievable values for the residual stress in the wear protection layer can also be increased by low values of porosity.

It was also shown that a higher peak number could be achieved with a low porosity of the wear protection layer, especially with an EDT Texturing process in which the surface of the wear protection layer can be textured by spark erosion.

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 are already advantageous without the other features of the invention.

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.

For further advantageous values for the permeability of the wear protection layer and the related properties of the wear protection layer, please refer to Table 7.

The permeability of the wear protection layer can also influence its quality. For example, a better layer quality with regard to the wear protection layer can be achieved if the wear protection layer has a low permeability, in particular a low gas permeability in Barrer.

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. In particular, the corrosion resistance of the wear protection layer can be improved with decreasing permeability values. The adhesive strength or delamination resistance of the wear protection layer can also be positively influenced by smaller permeability values of the wear protection layer. The hardness of the wear protection layer can also be increased with decreasing permeability values.

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

Surface roughness, hardness, residual stresses and number of peaks 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 ) )

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.

A generic working 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 can be achieved without the other features of the

invention are advantageous.

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.

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 related properties of the wear protection layer, reference is made to Table 8.

Tab. 8: Layer hardness of the wear protection layer (HV): Wear resistance and adhesive tensile strength of the wear protection layer (evaluation 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) )

Using the hardness values specified here, the wear resistance of the wear protection layer can be advantageously influenced or improved.

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, particularly 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 of the surface of the wear protection layer.

In particular, the ratio of hard phase to matrix, the precipitation of ditungsten carbide (W ₂ C ), the porosity and/or the permeability have an influence on the hardness of the wear protection layer of the working roll.

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.

Solely by means of the layer hardness selected for the wear protection layer, 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.

Furthermore, it is advantageous if the wear protection layer has a deviation of less than or equal to 40% from a weight proportion 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 a the elements tungsten carbide ₍ WC), aluminum oxide (AI2O3), zirconium _oxide ( _ZrO2 ), chromium carbide ( _Cr3C2 , _Cr7C3 and/or _Cr23C6 ) or _vanadium carbide (VC).

For further advantageous values for the maximum deviation of a weight proportion of a coating element within the wear protection layer (homogeneity of the distribution of the coating elements) and the related qualitatively assessed properties of the wear protection layer, reference is made to Table 9.

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

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

A determination in this regard can be made using microanalytical methods, such as an "EDX analysis" (Energy Dispersive X-ray Spectroscopy). EDX analysis can be used to advantageously carry out investigations of coating compositions. Even unknown materials or contamination with regard to chemical elements can be analyzed on the existing wear protection layer. Layer thickness measurements with regard to the wear protection layer can also be carried out.

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: k-g) as well as neutral (0) and best possible (10) (scale designation: n-b) )

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 is 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.

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.

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.

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.

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

Furthermore, properties of the wear protection layer present can be influenced if the wear protection layer has a thickness deviation of less 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. 20 % of a layer thickness of the wear protection layer 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 %, 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.

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.

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 with a waviness is not generally desired but only in special cases. Accordingly, for a large number of embodiments of a work roll, a wear protection layer with a homogeneous thickness and/or only small thickness deviations is advantageous.

The wear protection layer preferably 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.

By means of the thickness homogeneity proposed here, in particular the roughness Ra _of the wear protection layer and/or the waviness of the wear protection layer can be advantageously influenced.

Simply by designing the thickness homogeneity, 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.

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.

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.

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

Particularly advantageously, a hard phase comprises tungsten carbide (WC), aluminum oxide (AI2O3), zirconium oxide (ZrO2), chromium carbide (in particular Cr ₃ C ₂ , Cr ₇ C ₃ and/or Cr ₂₃ C ₆ ), vanadium carbide (VC), silicon carbide (SiC), tungsten boride (WB), chromium oxide (in particular CrO, Cr ₂ O ₃ , CrO ₃ and/or CrO ₃ ), titanium carbide (TiC), titanium oxide (in particular TiO, Ti ₂ O ₃ and/or TiO ₃ ) and/or molybdenum carbide (in particular Mo ₃ C and/or MoC).

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 . % .

For further advantageous values for the ratio of hard phase to matrix of the wear protection layer and the related qualitatively evaluated properties of the wear protection layer, please refer to Table 10.

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 element distribution, homogeneity of layer thickness distribution, peak number, adhesive tensile strength, residual stresses and porosity 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 ) . )

It should be expressly pointed out here that the term "ratio of hard phase to matrix" used here is to be understood in a 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.

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

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

Furthermore, the higher the hard phase content, the more particles can protrude from the wear protection layer, which can influence the roughness Ra _of the surface of the wear protection layer.

On the other hand, the softer the wear protection layer is, the denser this wear protection layer is, which in turn can result in the final thickness of the wear protection layer being thinner.

The softer the wear protection layer, i.e. the lower the hard phase content, the more particles can adhere to the surface, which can influence the homogeneity of the elements and the homogeneity of the thickness of the wear protection layer. Other interactions related to the existing hard phase/matrix ratio may occur at the wear protection layer in terms of peak count, adhesion, residual stresses and/or porosity.

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.

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 _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 (ZrO ₂ ), chromium carbide (Cr ₃ C ₂ , Cr ₇ C ₃ and/or Cr ₂₃ C ₆ ) and/or vanadium carbide (VC).

In particular, other coating elements can influence the formation and properties of the existing wear protection layer.

For example, the properties of all wear protection layers can be influenced with the following coating elements, consisting of tungsten carbide (WC), aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), chromium carbide (Cr ₃ C ₂ , Cr ₇ C ₃ and/or Cr ₂₃ C6), vanadium carbide (VC), silicon carbide (SiC), tungsten boride (WB), chromium oxide (CrO, Cr ₂ O ₃ , CrO ₂ and/or CrO ₃ ), titanium carbide (TiC), titanium oxide (TiO, Ti ₂ O ₃ and/or TiO ₂ ) or molybdenum carbide (Mo ₂ C and/or MoC), in particular at least one, two, three, four or more of the elements tungsten carbide (WC), aluminum oxide (AI2O3), zirconium oxide (ZrCt), chromium carbide (Cr ₃ C2, Cr ₇ C3 and/or Cr ₂ 3Ce) and/or vanadium carbide (VC) in all combinations and compositions.

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

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

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 their hardness as well as other properties of the wear protection layer.

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

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 are already advantageous without the other features of the invention.

It is further advantageous if the wear protection layer and/or the base body has 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 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 .

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.

Using the present values, an improvement in the wear resistance of 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 the layer adhesion can be achieved by forming the proposed residual compressive stresses.

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

Furthermore, any microcracks that may occur in the wear protection layer can be closed again by residual compressive stresses in the wear protection layer, whereby any crack growth of the microcracks can be advantageously reduced or prevented. Analogously, residual tensile stresses can support the growth of microcracks.

As a rule, layer growth of the wear protection layer is also negatively influenced by unfavorable tensile residual stresses.

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

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 measured in N/mm ² .

Further features, effects and advantages or disadvantages can be found in the following Table 11:

Tab. 11: Residual compressive stress (N/mm ² ): Wear resistance, layer adhesion, layer adhesion and adhesive tensile strength of each wear protection layer (evaluation between 0 and 10 with the individual scales between smallest possible ( 0 ) and greatest possible ( 10 ) ( scale designation : kg) as well as neutral ( 0 ) and best possible ( 10 ) ( scale designation : nb ) )

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, 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.

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.

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.

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

It should be noted, however, 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 was shown that higher peak numbers can be achieved with higher arithmetic mean roughness values R _a , whereas high peak numbers can also be achieved with lower arithmetic mean roughness values R _a .

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

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

Particularly advantageously, the wear protection layer has an oxide content, in particular a content of chromium oxide (CrO, Cr ₂ O ₂ , CrO ₂ and/or CrO ₂ ) and/or aluminum oxide (Al ₂ O ₂ ) and/or zirconium oxide (ZrO ₂ ) and/or titanium oxide (TiO, Ti ₂ O ₂ and/or TiO ₂ ), 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. %.

Smaller values for the oxide content can be achieved, among other things, by using a thermal spraying device with a lambda value close to one or one .

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.

It has also proven to be advantageous if the base body has an outer surface to be coated with an arithmetic Average 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 average 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.

The roughness R _{a of} the base body surface can also be used to influence the wear protection layer, 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 _a of the 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.

The particle adhesion and thus also the layer adhesion of the wear protection layer to the base body surface can be influenced by the roughness of the base body surface.

The roughnesses R _a mentioned here with respect to the base body surface can be produced in different ways, whereby several of the roughnesses R _a indicated can be achieved by grinding the outer surface (base body surface) of the work roll, such as roughnesses R _a of 0.3 pm to 0.8 pm.

Further features, effects or advantages or disadvantages can be found in the following Table 12:

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 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) )

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

It has also proven to be useful 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.

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 working roll can be advantageously influenced or adjusted.

If the base body hardness is too soft, components of the wear protection layer can penetrate into 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 bounce off the base body when it is applied.

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

The harder the base body, the lower the adhesive tensile strength of the wear protection layer, which makes it easier for the wear protection layer to detach from the base body.

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.

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

In addition, defects can in turn influence the residual stresses in the wear protection layer, and vice versa. Furthermore, adhesion mechanisms in the spraying process can influence the roughness and layer thickness of the wear protection layer.

The harder the wear protection layer, the more the roughness Ra _of the surface of the wear protection layer can be influenced.

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

Further features, effects or advantages or disadvantages can be found in the following Table 13:

Tab. 13: Base body hardness (HRC): porosity, defect frequency, adhesive tensile strength, residual stresses and 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) ) 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 are already advantageous without the other features of the invention.

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.

Selected dimensions with regard to 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 also affect the quality of the wear protection layer.

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 individually adapted to different requirements, taking into account legal requirements for the avoidance of hard chromium.

According to a further aspect, the object of the invention is also achieved by a rolling stand having a working 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.

Advantageously, the surface image obtained on the metallic strip can be used to identify certain features of the wear protection layer. In particular, the texturing of the wear protection layer of the working roll can change during rolling. a metallic strip from the surface of the working roll, in particular the surface of the wear protection layer, to the surface of the metallic strip.

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.

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

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 produce process-specific wear protection layers.

The wear protection layer can be further adapted to suit the application if the wear protection layer is abrasive smoothed after application. Just as an example, it should be mentioned here that the surface roughness of the wear protection layer can be further adjusted on the working roll.

In particular, such a method can be advantageously further developed if the number of powder conveyors is increased, whereby a more homogeneous powder distribution can be achieved. This can also further increase the quality of the wear protection layer on the working roll.

At this point, it should be claimed that the method described 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 To advantageously further develop processes and to be able to present or formulate process specifications even more precisely.

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.

Furthermore, it can 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.

Additional sieving of powder can ensure a more homogeneous powder distribution.

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 for the purpose of optimizing residual stresses with regard to the wear protection layer.

The object of the invention is further also achieved by a work roll according to one of the features described here for cold rolling a metallic strip.

By using this work roll, high-quality surfaces can be reliably produced on the cold-rolled metallic strip, particularly over a longer period of time. The measures mentioned above, 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.

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

In the drawing, the only figure shows: a schematic 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.

According to the single figure, the production of a work roll 1 for rolling a metallic product (not shown), in particular for rolling a metallic strip (also not shown) is shown schematically.

The working roller 1 is processed by means of thermal spraying. More precisely, a wear protection layer 2 is applied to the surface 3 of a base body 4 of the working roller 1.

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

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

By means of the thermal spraying device 5, 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.

list of reference symbols

I Working roll 2 Wear protection layer

3 Surface

4 basic bodies

5 Device for thermal spraying

6 Powder conveyor 7 Sieving device

8 powders

9 powder components

10 Sieving device

I I Coating material 12 Direction of rotation

Claims

patent claims 1. 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 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. %. 2. Work roll (1) according to claim 1, 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. %. 3. Work roll (1) according to one of claims 1 or 2, characterized in that the wear protection layer (2) has an outer surface with an arithmetic mean roughness value 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 with an arithmetic mean roughness value 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. 4. 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. 5. 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. %. 6. Work roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) has a proportion of tungsten precipitates, in particular of elemental tungsten (W) and/or ditungsten carbide (W ₂ C), with a proportion 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. %. 7. 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. 8. Work 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 . 9. 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%. 10. 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%. 11. 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. 12. 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 proportion 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) _. . 13. Working roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) is 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, has a thickness deviation of less than or equal to 20% from 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%, 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. 14. 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. 15. 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. 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, in particular a ratio of hard phase to an overall layer system consisting of hard phase and matrix with a ratio value 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 value 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. %. 17. 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 (AI2O3), zirconium oxide ( _ZrO2 ), chromium carbide ( _Cr3C2 , _Cr7C3 and/or _Cr23C6 ), vanadium carbide (VC), silicon carbide (SiC), tungsten boride (WB), chromium oxide (CrO, _Cr203 , _CrO2 and/or CrO3), titanium carbide (TiC), titanium oxide (TiO, _Ti203 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), Aluminium oxide (AI2O3), zirconium oxide ( _ZrO2 ), chromium carbide ( _Cr3C2 , _Cr7C3 and/or _Cr23Ce ) and/or vanadium carbide (VC). 18. 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 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 (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 . 19. 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. 20. Working roll (1) according to one of the preceding claims, characterized in that the wear protection layer (2) contains an oxide portion, in particular a portion of aluminum oxide (AI2O3) and/or zirconium oxide (ZrO ₂ ) and/or chromium oxide (CrO, Cr ₂ O ₃ , CrO ₂ and/or CrO ₃ ) and/or titanium oxide (TiO, Ti ₂ O ₃ and/or TiO ₂ ), 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. %. 21. Work 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 value 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 value 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. 22. 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. 23. Roll stand comprising a work roll (1) according to one of claims 1 to 22. 24. Metallic strip, wherein the metallic strip is cold rolled with a work roll (1) according to one of claims 1 to 22. 25. A method for producing a work roll (1) according to one of claims 1 to 22 comprising the following steps: Providing the base body (4) ; and Application of the wear protection layer (2) using a thermal spraying process. 26. Method according to claim 25, characterized in that the wear protection layer (2) is abrasively smoothed after application. 27. Use of a work roll (1) according to one of claims 1 to 22 for cold rolling a metallic strip.