Working roll for rolling metal products, rolling stand, metal strip, method for producing working roll and use of working roll

Abstract

The invention relates to a working roll for rolling metal products, in particular for rolling metal strips, comprising: a metal matrix; and a wear-resistant protective layer at least partially arranged on the base body, the wear-resistant protective layer being a thermally sprayed protective layer; wherein the particle size of the wear-resistant protective layer is less than or equal to 50 m, preferably less than or equal to 45 m, particularly preferably less than or equal to 30 m or less than or equal to 20 m.

Description

[0001] The present invention relates to a work roll for rolling metal articles, particularly for rolling metal strips, comprising a substrate made of metal and a wear-resistant protective layer disposed at least partially on the substrate, wherein the wear-resistant protective layer is a thermally sprayed protective layer.

[0002] The present invention also relates to a rolling mill stand.

[0003] The present invention also relates to a metal strip cold rolled by means of work rolls.

[0004] The present invention also relates to a method for manufacturing work rolls.

[0005] The present invention also relates to the use of a work roller.

[0006] This type of work roll, or the method for manufacturing such a work roll, is known in the prior art.

[0007] In order to increase the service life of this type of work roll, a suitable wear-resistant protective layer is provided on its surface, which simultaneously creates a defined surface texture on the belt.

[0008] The specific design of the wear-resistant protective layer must take into account various influencing variables, because the wear-resistant protective layer combined with the high load during the rolling process may also exhibit various wear properties.

[0009] Typically, suitable wear-resistant protective coatings include hard chrome plating; however, hard chrome plating is also prone to microcrack formation, which in turn can adversely affect service life and corrosion resistance. In the manufacture of previously known chromium-based wear-resistant protective coatings, particularly hard chrome plating, hexavalent chromium (Cr-6) has been used to date. Cr-6 is now considered carcinogenic and / or mutagenic.

[0010] There are different methods to apply abrasion-resistant protective layers to work rolls.

[0011] The purpose of this invention is to propose an improvement or alternative to the existing technology.

[0012] According to a first aspect, the object of the present invention is to provide a work roll for rolling metal articles, particularly for rolling metal strips, comprising a metal substrate and a wear-resistant protective layer at least partially disposed on the substrate, wherein the wear-resistant protective layer is a thermally sprayed protective layer, wherein the wear-resistant protective layer has a particle size of less than or equal to 50µm, preferably less than or equal to 45µm, particularly preferably less than or equal to 30µm or less than or equal to 20µm.

[0013] Smaller particle size has many advantages for wear-resistant protective layers, and therefore also for this work roll.

[0014] The smaller the particle size in the wear-resistant protective layer, the thinner the wear-resistant protective layer can be formed, for example.

[0015] For example, in order to ensure sufficient roughness of the wear-resistant protective layer, it is advantageous if the wear-resistant protective layer has a particle size of greater than or equal to 2 µm, preferably greater than or equal to 5 µm.

[0016] For other favorable values ​​regarding the particle size and related properties of the wear-resistant protective layer, please refer to Table 1 below.

[0017] In the context of this invention, the term "particle size" describes the average diameter or average surface area of ​​the abrasive pattern of microcrystals (grains) within a polycrystalline metal. In the thermal spraying process, the particle size of the wear-resistant protective layer proposed herein is specifically determined by the particle size of the starting material used to provide the coating material for producing the wear-resistant protective layer. Therefore, in particular, the term "particle size" is related to the particle size of the powder particles used as the starting material.

[0018] The term “delamination” here describes, in particular, the unintentional separation of the wear-resistant protective layer from the substrate surface.

[0019] In the context of this invention, the term "elemental distribution" describes the volume fraction of the hard phase and the matrix, wherein the volume fraction can be determined, for example, by means of a microscope after coating the matrix.

[0020] In the context of this invention, the term "matrix" or "matrix material" refers to the structure of the applied wear-resistant protective layer.

[0021] In this case, the "hard phase" is embedded or "floated" in the softer material of the wear-resistant protective layer, especially in the softer matrix or softer matrix material of the wear-resistant protective layer.

[0022] In this case, the hard phase suitable for the wear-resistant protective layer can be, in particular, an oxide, carbide, or boride hard phase, which advantageously has high hardness. For example, a compound of silicon and carbon that forms silicon carbide (SiC) can be used.

[0023] In this context, the term "anti-adhesion tensile strength" describes the resistance to adhesion acting on the wear-resistant protective layer.

[0024] Adhesion is the ability of the wear-resistant protective layer to adhere to the substrate of the work roll.

[0025] In this context, the term "cohesion" mentioned below describes the adhesion between the individual layers or coatings of the wear-resistant protective layer.

[0026] The term "phase" here typically describes the state of one or more elements. In particular, intermetallic phases describe compounds of at least two metals, especially homogeneous compounds.

[0027] The particle size of the wear-resistant protective layer, especially the average particle size of the hard phase and the average particle size of the hard phase elements, affects multiple properties of the wear-resistant protective layer. Particle size can be influenced by the process parameters of the thermal spraying wear-resistant protective layer, particularly by the average diameter of the powder used.

[0028] Among other things, particle size can advantageously affect the uniformity of the wear-resistant protective layer, particularly the uniformity of the distribution of coating elements within the wear-resistant protective layer, especially the distribution of hard phase elements within the wear-resistant protective layer, as well as the uniformity of the thickness of the wear-resistant protective layer. Experiments show that the above-mentioned uniformity can be improved by decreasing the particle size.

[0029] In addition, the roughness R of the wear-resistant protective layer a In particular, the arithmetic mean roughness R a The roughness can be affected by particle size. In particular, by using a smaller particle size, the arithmetic mean roughness R of the thermally sprayed and subsequently unprocessed wear-resistant protective layer can be obtained. a The smaller value.

[0030] Residual stress in the wear-resistant protective layer can be affected by particle size. Smaller particle size can increase residual stress in the wear-resistant protective layer. It has been found that higher residual stress in the wear-resistant protective layer can lead to improved anti-adhesion tensile properties. As a result, on the one hand, the risk of delamination between the wear-resistant protective layer and the work roll matrix can be reduced by using smaller particle size. However, anti-delamination properties are also affected by the influence of particle size on the porosity of the wear-resistant protective layer.

[0031] Table 1: Particle size (µm) of wear-resistant protective layer: roughness of wear-resistant protective layer, roughness of product (strip) processed by work roll, residual stress in wear-resistant protective layer and / or substrate, porosity, hardness, peak number, uniformity, especially uniformity of coating element distribution within wear-resistant protective layer and uniformity of wear-resistant protective layer thickness, (coating) element distribution, resistance to adhesion stretching and delamination (evaluation in each case is between 0 and 10, with individual scales between minimum possible (0) and maximum possible (10) (scale name: kg) and neutral (0) and best possible (10) (scale name: nb). On the other hand, even during thermal spraying, the particle size obtained within the wear-resistant protective layer affects the kinetics of the coating material when applied to the substrate surface and the temperature of the coating material particles. A larger average powder diameter results in a larger particle size in the wear-resistant protective layer, lower particle velocity, and lower adhesion under constant heat transfer conditions. Consequently, the anti-adhesion tensile properties of the wear-resistant protective layer also decrease again with increasing particle size.

[0032] In the thermal spraying of wear-resistant protective layers, it has been found that as the average diameter of the powder used increases, and thus as the particle size of the wear-resistant protective layer increases, fewer particles of the powder remain adhered, resulting in the uniformity of element distribution being affected.

[0033] When thermally spraying a wear-resistant protective layer, the higher the thermal energy of the powder particles, the greater the risk of unwanted precipitation of elemental tungsten particles and / or tungsten dicarbide (W2C).

[0034] In addition to affecting roughness and residual stress, particle size also affects the porosity of the wear-resistant protective layer. In particular, larger particle sizes will increase the porosity of the wear-resistant protective layer, thereby reducing its hardness.

[0035] Furthermore, particle size can also affect the peak number of the wear-resistant protective layer, and thus affect the roughness of the metal strip processed by the work roll. The optimal peak number can be achieved within the intermediate range of particle sizes considered here, so that the roughness of the metal strip processed by the work roll can also be optimal within the intermediate range of particle sizes considered here.

[0036] Preferably, the wear-resistant protective layer has a chromium content of less than or equal to 90% by weight, more preferably less than or equal to 60% by weight, and particularly preferably less than or equal to 30% by weight.

[0037] For other favorable values ​​regarding the chromium ratio and related properties of the wear-resistant protective layer, please refer to Table 2.

[0038] This wear-resistant protective layer is used to protect the work roll from wear.

[0039] If the wear-resistant protective layer is designed as suggested, it can ensure improved wear resistance of the work roll substrate.

[0040] On the other hand, it can eliminate or at least significantly reduce the risk of serious carcinogenic and / or mutagenic interactions with organisms, especially with workers or operators.

[0041] The wear-resistant protective layer proposed herein, the work roll, but especially the wear-resistant protective layer itself, can be provided as freely as possible, preferably completely free of chromium, especially hard chromium, which has been the main requirement for wear-resistant protective layers to date, and has at least constant or even improved quality properties, such as improved surface quality, improved service life and further improved performance of the work roll, which will be described in more detail below.

[0042] In any case, the wear-resistant protective layer can ensure a constant roughness on the surface of the work roll for as long as possible, which affects the desired target variables of the metal product to be rolled for as long as possible during the rolling process, such as the surface of the metal product to be produced, especially the roughness and texture or smoothness of the metal strip to be produced.

[0043] In particular, the wear-resistant protective layer designed accordingly for the work roll itself already achieves the purpose of this invention.

[0044] It should also be noted that, in the context of this patent application, indefinite articles and indefinite numbers, such as “one…”, “two…”, etc., should generally be understood as minimum values, i.e., “at least one…”, “at least two…”, etc., unless it can be clearly seen from the context or the specific text of a particular paragraph, for example, only “exactly one…”, “exactly two…”, etc.

[0045] It should also be noted that, within the scope of this patent application, the expression "in particular" always refers to the introduction of optional or preferred features through this expression. This expression should not be construed as "exactly" or "that is to say".

[0046] In this case, it is preferable to set a lower nickel content, especially a nickel ratio of less than or equal to 90% by weight, preferably less than or equal to 60% by weight, and particularly preferably less than or equal to 30% by weight, because wear resistance decreases with increasing nickel content.

[0047] For other favorable values ​​regarding the nickel content of the wear-resistant protective layer and its related properties, please refer to Table 2.

[0048] Further features, effects, advantages, or disadvantages can be found in Table 2 below: Table 2: Chromium and / or Nickel Ratio (wt%): Residual Compressive Stress and Abrasion Resistance (Evaluation in each case is between 0 and 10, with individual scales between minimum possible (0) and maximum possible (10) (scale name: kg) and neutral (0) and best possible (10) (scale name: nb). As shown in Table 2, a higher proportion of chromium and / or a lower proportion of nickel can improve the wear resistance of the wear-resistant protective layer. In particular, a lower proportion of chromium and a lower proportion of nickel can improve or avoid mutagenic and / or carcinogenic effects on the surrounding environment.

[0049] Experiments show that the selection of the chromium and / or nickel ratio in the wear-resistant protective layer affects the residual stress generated in the wear-resistant protective layer. In the context of this specification, the term residual stress should always be understood as residual compressive stress unless otherwise explicitly stated.

[0050] The level of residual compressive stress in the wear-resistant protective layer can also support its wear resistance. By establishing residual compressive stress in the wear-resistant protective layer, it is possible to achieve an advantageous clamping of the wear-resistant protective layer onto the substrate, thereby ultimately improving layer stability and / or layer quality, particularly resistance to adhesive tensile stress. Therefore, the resistance to adhesive tensile stress of the wear-resistant protective layer can be particularly advantageously affected by a reduction in the nickel content.

[0051] Furthermore, any microcracks that may appear in the wear-resistant protective layer can be closed again by the residual compressive stress in the wear-resistant protective layer, thereby advantageously reducing or preventing any crack propagation of the microcracks.

[0052] Experiments show that the residual stress level observed in the wear-resistant protective layer increases with the increase of the chromium ratio in the wear-resistant protective layer, and decreases with the increase of the nickel ratio in the wear-resistant protective layer.

[0053] Furthermore, if the wear-resistant protective layer has an arithmetic mean roughness R a The outer surface has a roughness greater than or equal to 0.01 µm, preferably greater than or equal to 0.5 µm, and particularly preferably greater than or equal to 1.5 µm, and / or if the wear-resistant protective layer has an arithmetic mean roughness R. a An outer surface with a diameter of 17µm or less, preferably 10µm or less, and particularly preferably 6µm or less, is advantageous.

[0054] Regarding the arithmetic mean roughness R of the outer surface of the wear-resistant protective layer a For other favorable values ​​related to the wear-resistant protective layer, please refer to Table 3.

[0055] Using the roughness values ​​given here, the roughness R of the wear-resistant protective layer of this work roll is... a It can be individually adjusted to meet the requirements of the product to be processed, resulting in the surface roughness R of the product. a The surface roughness, especially that of the strip material, can be determined almost arbitrarily. In other words, the factory roughness R of the wear-resistant protective layer of the product to be sold can be adjusted accordingly. a .

[0056] The ability to specifically determine the surface roughness of a product is particularly advantageous for various product performance characteristics, such as paintability, tactile properties, deep drawing and / or pressing behavior, and adjustable rolling force.

[0057] Table 3: Arithmetic mean roughness R of the outer side of the wear-resistant protective layer a(µm): Adjustability of the surface roughness of rolled products, paintability of rolled products, texture of rolled products, deep drawing and pressing behavior of rolled products, adjustability of rolling force and porosity of wear-resistant protective layer (evaluation in each case is between 0 and 10, with individual scales between minimum possible (0) and maximum possible (10) (scale name: kg) and neutral (0) and best possible (10) (scale name: nb). In addition, the arithmetic mean roughness R of the wear-resistant protective layer surface a There is an interaction between the wear-resistant protective layer and the achievable porosity.

[0058] By means of only the feature concerning the arithmetic mean roughness, general-purpose work rolls can be advantageously improved, such that the relevant feature or combination of features is already advantageous in the absence of other features of the present invention.

[0059] Arithmetic mean roughness R of the outer surface of the wear-resistant protective layer a Smaller values ​​can result in better texture of the work rolls and the strip material rolled by the work rolls, as well as favorable adjustability of the rolling force.

[0060] Arithmetic mean roughness R of the outer surface of the wear-resistant protective layer a The average values ​​(see Table 3) contribute to the optimal conditions for the paintability of metal products rolled with work rolls.

[0061] Arithmetic mean roughness R of the outer surface of the wear-resistant protective layer a Higher values ​​(see Table 3) can improve deep drawing and / or pressing behavior as well as the adhesion of strip coatings to metal products rolled with work rolls.

[0062] It has been found that the arithmetic mean roughness R of the outer surface with the wear-resistant protective layer a A lower value (see Table 3) for the wear-resistant protective layer helps reduce the porosity of the wear-resistant protective layer, resulting in a lower arithmetic mean roughness R. a At lower values, the anti-adhesion tensile properties of the wear-resistant protective layer, which depend on the porosity of the wear-resistant protective layer, can also be improved.

[0063] Particularly preferred, the wear-resistant protective layer has a proportion of tungsten carbide (WC) greater than or equal to 50% by weight, preferably greater than or equal to 60% by weight, and particularly preferred to have a proportion of greater than or equal to 70% by weight.

[0064] In the context of this application, tungsten carbide (WC) is explicitly understood to be tungsten carbide monocarbide (WC).

[0065] The hardness of the wear-resistant protective layer can be advantageously increased by the weight proportion of tungsten carbide in the wear-resistant protective layer, especially as a component of the hard phase of the wear-resistant protective layer. In particular, the increase in the proportion of monotungsten carbide (WC) in the wear-resistant protective layer allows for a further increase in the hardness of the wear-resistant protective layer.

[0066] The wear-resistant protective layer can advantageously have a proportion of tungsten carbide (WC) greater than or equal to 2% by weight, preferably greater than or equal to 20% by weight, particularly preferably greater than or equal to 25% by weight or greater than or equal to 30% by weight. Furthermore, the wear-resistant protective layer can advantageously have a proportion of tungsten carbide (WC) greater than or equal to 40% by weight, preferably greater than or equal to 45% by weight, particularly preferably greater than or equal to 65% by weight or greater than or equal to 70% by weight. Particularly advantageously, the wear-resistant protective layer can have a proportion of tungsten carbide (WC) greater than or equal to 75% by weight, preferably greater than or equal to 80% by weight, particularly preferably greater than or equal to 85% by weight or greater than or equal to 87% by weight.

[0067] If the wear-resistant protective layer has tungsten deposits, especially elemental tungsten (W) and / or tungsten carbide (W2C), the proportion of which is less than or equal to 50% by weight, preferably less than or equal to 33% by weight, particularly preferably less than or equal to 10% by weight or less than or equal to 5% by weight, the wear-resistant protective layer can be further improved.

[0068] For other favorable values ​​regarding the weight ratio of tungsten deposits in the wear-resistant protective layer and related properties of the wear-resistant protective layer, please refer to Table 4.

[0069] Tungsten precipitates in the form of elemental tungsten (W) and / or tungsten carbide (W2C) can be formed by the degradation of tungsten carbide (WC).

[0070] Table 4: Tungsten precipitates (elemental tungsten and / or tungsten carbide W2C) in wear-resistant protective layers (wt%): brittleness, wear resistance, fracture toughness, anti-adhesion tensile strength, service life, hardness, and layer adhesion of each wear-resistant protective layer (evaluations in each case are between 0 and 10, with individual scales between minimum possible (0) and maximum possible (10) (scale name: kg) and neutral (0) and best possible (10) (scale name: nb). Tungsten deposits in wear-resistant protective layers, particularly in the form of elemental tungsten (W) and / or tungsten dicarbide (W₂C), can lead to brittleness in the wear-resistant protective layer. Consequently, as the proportion of tungsten deposits increases, the wear resistance, fracture toughness, and / or anti-adhesion tensile strength of the wear-resistant protective layer can decrease. In general, a higher proportion of tungsten deposits in the wear-resistant protective layer thus reduces its service life.

[0071] However, it must be noted that, for example, a higher "weight%" proportion of tungsten deposits can increase the hardness of the wear-resistant protective layer.

[0072] Furthermore, the proportion of tungsten deposits within the wear-resistant protective layer affects the layer adhesion between adjacent individual layers of the wear-resistant protective layer, especially when one layer is placed on top of another and not applied simultaneously. In this case, the layer adhesion decreases as the proportion of tungsten deposits increases.

[0073] In this regard, it is essential to ensure that the wear-resistant protective layer has a balanced "weight%" ratio of tungsten deposits.

[0074] By means of the proportion of tungsten precipitates, particularly elemental tungsten (W) and / or tungsten carbide (W2C) precipitates, general-purpose work rolls can be advantageously improved, such that the relevant features or combinations thereof are already advantageous without the other features of the present invention.

[0075] It is also advantageous if the wear-resistant protective layer has a layer thickness of 2µm or greater, preferably 5µm or greater, particularly preferably 10µm or greater, and / or has a layer thickness of 80µm or less, preferably 40µm or less, particularly preferably 15µm or less.

[0076] For other favorable values ​​regarding the thickness of the wear-resistant protective layer and its related properties, please refer to Table 5.

[0077] By utilizing the aforementioned values ​​for the thickness of the wear-resistant protective layer, an exceptionally robust wear-resistant protective layer can be obtained.

[0078] It should be noted that the thinner layer chosen results in lower cohesion. Therefore, the adhesion relative to the wear-resistant protective layer increases. Experiments show that this can lead to better wear behavior, reduced delamination resistance, and increased impact resistance, with particularly small values ​​of the wear-resistant protective layer thickness exhibiting a reversal of the trend in delamination resistance and / or impact resistance.

[0079] The reason for this trend reversal may be the reduction in the magnitude of residual stress in the wear-resistant protective layer, which leads to a smaller layer thickness, since it has been shown that anti-delamination can increase with the increase of the value of residual stress in the wear-resistant protective layer.

[0080] Furthermore, lower layer thickness values ​​can achieve a more uniform distribution of elements in the wear-resistant protective layer and improved distribution of individual metallurgical phases within the layer. Experiments show that the uniformity of element distribution in the wear-resistant protective layer decreases with increasing layer thickness.

[0081] Regarding the precipitation of elemental tungsten (W) and / or tungsten carbide (W₂C), experiments show that these increase with increasing layer thickness. During the application of the wear-resistant protective layer, a thinner protective layer can result in a lower maximum temperature within the protective layer because the thinner layer can cool more quickly on the substrate side and the side of the protective layer facing away from the substrate. During the thermal spraying of the wear-resistant protective layer, an increase in the maximum temperature of the protective layer favors the precipitation of elemental tungsten (W) and / or tungsten carbide (W₂C). Furthermore, it has been shown that during the thermal spraying of the wear-resistant protective layer, an increase in the cooling rate can reduce the precipitation of elemental tungsten (W) and / or tungsten carbide (W₂C).

[0082] Furthermore, it can be observed that as the thickness of the wear-resistant protective layer increases, the minimum achievable arithmetic roughness of the surface of the wear-resistant protective layer may increase and / or lead to an increase in the uniformity of the thickness distribution of the wear-resistant protective layer, so that a larger thickness of the wear-resistant protective layer may also lead to higher post-processing costs until its intended use.

[0083] Table 5: Layer thickness of wear-resistant protective layer (μm): Cohesion, wear resistance, anti-delamination, elemental distribution (uniformity), residual stress, impact resistance, tungsten precipitate and phase distribution of each wear-resistant protective layer (evaluation in each case is between 0 and 10, with individual scales between minimum possible (0) and maximum possible (10) (scale name: kg) and neutral (0) and best possible (10) (scale name: nb). By simply selecting the appropriate thickness of the wear-resistant protective layer, general-purpose work rolls can be advantageously improved, making the relevant features or combinations thereof already advantageous even without other features of the present invention.

[0084] Furthermore, it is advantageous if the wear-resistant protective layer has an adhesive tensile strength greater than or equal to 60 N / mm², preferably greater than or equal to 70 N / mm², particularly preferably greater than or equal to 80 N / mm² or greater than or equal to 100 N / mm².

[0085] When performing an adhesive tensile test, it can be determined whether the wear-resistant protective layer under study completely, partially, or not at all peels off after being tested with a tensile force applied along the normal direction of the wear-resistant protective layer. Therefore, adhesive tensile resistance is understood as the value of the tensile force at which the wear-resistant protective layer does not peel off at the inspected location. Thus, a higher value of adhesive tensile resistance is beneficial to the wear-resistant protective layer's resistance to delamination.

[0086] In addition, the wear-resistant protective layer advantageously has an adhesive tensile strength greater than or equal to 55 N / mm², preferably greater than or equal to 65 N / mm², particularly preferably greater than or equal to 75 N / mm² or greater than or equal to 90 N / mm².

[0087] The anti-adhesion and tensile properties of the wear-resistant protective layer alone can advantageously improve general-purpose work rolls, making the relevant features or combinations thereof already advantageous even without other features of the present invention.

[0088] Furthermore, it is advantageous if the wear-resistant protective layer has a porosity 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%.

[0089] For other favorable values ​​regarding the porosity and related properties of the wear-resistant protective layer, please refer to Table 6.

[0090] Table 6: Porosity (%) of wear-resistant protective layers: mass, corrosion resistance, delamination resistance, surface roughness, hardness, residual stress and peak number of each wear-resistant protective layer (evaluation in each case is between 0 and 10, with individual scales between minimum possible (0) and maximum possible (10) (scale name: kg) and neutral (0) and best possible (10) (scale name: nb). In this context, the term "porosity" describes the number and / or size of pores in the wear-resistant protective layer, expressed as a percentage (%). This figure can be determined, for example, by means of optical evaluation or by a permeation experiment, in which the water displacement of the wear-resistant protective layer and / or the work roll together with the wear-resistant protective layer is examined under vacuum.

[0091] Experiments show that, in terms of the required properties of the work roll, especially corrosion resistance, delamination resistance, and hardness, the overall quality of the wear-resistant protective layer of the work roll can be improved by reducing the porosity of the wear-resistant protective layer.

[0092] In particular, the corrosion resistance of the wear-resistant protective layer can be improved as the porosity value decreases.

[0093] The anti-adhesion tensile properties or anti-delamination properties of the wear-resistant protective layer can also be positively affected by the lower porosity of the wear-resistant protective layer.

[0094] The hardness of the wear-resistant protective layer can also increase as the porosity value decreases.

[0095] A small roughness value on the outer surface of the wear-resistant protective layer can be advantageously achieved, especially with a small porosity value, particularly by adding the wear-resistant protective layer with the aid of a thermal spraying process and / or by removing the outer layer of the wear-resistant protective layer through subtraction.

[0096] The achievable value of residual stress in the wear-resistant protective layer can also be increased by using a low porosity value.

[0097] It can also be demonstrated that a higher peak number can be obtained at the low porosity of the wear-resistant protective layer, especially using the EDT texturing method, in which the surface of the wear-resistant protective layer can be textured by means of spark erosion.

[0098] By means of the porosity of the wear-resistant protective layer alone, general-purpose work rolls can be advantageously improved, making the relevant features or combinations thereof advantageous even without other features of the present invention.

[0099] Furthermore, it is advantageous if the wear-resistant protective layer has a permeability value of less than or equal to 1 bar, preferably less than or equal to 0.5 bar, and particularly preferably less than or equal to 0.1 bar.

[0100] For other favorable values ​​regarding the permeability and related properties of the wear-resistant protective layer, please refer to Table 7.

[0101] The permeability of the wear-resistant protective layer also affects its quality. Therefore, if the wear-resistant protective layer has low permeability, especially low gas permeability within the barrier, a better layer quality can be obtained.

[0102] Experiments show that, in terms of the required properties of the work roll, especially corrosion resistance, delamination resistance, and hardness, the overall quality of the wear-resistant protective layer of the work roll can be improved as the permeability of the wear-resistant protective layer decreases.

[0103] In particular, the corrosion resistance of the wear-resistant protective layer can increase as the permeability value decreases.

[0104] The anti-adhesion tensile properties or anti-delamination properties of the wear-resistant protective layer can also be positively affected by a lower value of the wear-resistant protective layer's permeability.

[0105] The hardness of the wear-resistant protective layer can also increase as the permeability value decreases.

[0106] In this context, the term "permeability" describes the permeability of the wear-resistant protective layer, which can be determined primarily by the number of flowable or open pores in the wear-resistant protective layer, particularly pores that allow gas flow.

[0107] By means of the permeability of the abrasion-resistant protective layer alone, general-purpose work rolls can be advantageously improved, making the relevant features or combinations thereof advantageous even without other features of the present invention.

[0108] Table 7: Permeability of Abrasion Protective Layers (Barriers): Quality, Corrosion Resistance, Delamination Resistance, Surface Roughness, Hardness, Residual Stress, and Peak Number of Each Abrasion Protective Layer (Evaluations in each case are between 0 and 10, with individual scales between minimum possible (0) and maximum possible (10) (scale name: kg) and neutral (0) and best possible (10) (scale name: nb). It is advantageous if the wear-resistant protective layer has a layer hardness value greater than or equal to 800 HV, preferably greater than or equal to 1000 HV, particularly preferably greater than or equal to 1100 HV, and / or has a layer hardness value less than or equal to 1600 HV, preferably less than or equal to 1500 HV, particularly preferably less than or equal to 1400 HV.

[0109] For other favorable values ​​of the hardness of the wear-resistant protective layer and related properties of the wear-resistant protective layer as measured by the Vickers method, which can be measured by means of macroscopic identification methods, please refer to Table 8.

[0110] Table 8: Layer hardness (HV) of wear-resistant protective layers: Abrasion resistance and anti-adhesion tensile properties of each wear-resistant protective layer (evaluation in each case is between 0 and 10, with individual scales between minimum possible (0) and maximum possible (10) (scale name: kg) and neutral (0) and best possible (10) (scale name: nb). The hardness values ​​provided here can be used to advantageously influence or improve the wear resistance of the wear-resistant protective layer.

[0111] However, experiments have shown that the harder the wear-resistant protective layer is, the lower its anti-adhesion tensile strength, especially regarding adhesion to the substrate of the work roll.

[0112] Furthermore, it should be noted that by selectively adjusting the layer hardness, the residual stress appearing in the wear-resistant protective layer and the surface roughness R of the wear-resistant protective layer can be advantageously influenced. a .

[0113] Specifically, the ratio of hard phase to matrix, tungsten carbide (W2C) precipitates, porosity, and / or permeability affect the hardness of the wear-resistant protective layer of the work roll.

[0114] Furthermore, the interaction between layer hardness and peak number of wear-resistant protective layer, porosity of wear-resistant protective layer and uniformity of wear-resistant protective layer can be advantageously utilized.

[0115] By simply by means of the layer hardness selected for the wear-resistant protective layer, general-purpose work rolls can be advantageously improved, making the relevant features or combinations thereof already advantageous in the absence of other features of the present invention.

[0116] Furthermore, if in multiple analytical points of 80% or more, preferably 90% or more, and particularly preferably 95% or more, the average weight ratio of the wear-resistant protective layer to the coating elements in the total number of analytical points has a deviation of less than or equal to 40%, preferably less than or equal to 30%, and particularly preferably less than or equal to 20%, wherein the total number of analytical points is greater than or equal to 5, preferably greater than or equal to 15, and particularly preferably greater than or equal to 25, and especially if the coating elements are tungsten carbide (WC), alumina (Al2O3), zirconium oxide (ZrO2), chromium carbide (Cr3C2, Cr7C3 and / or Cr... 23 It is advantageous to have one of the elements C6 or vanadium carbide (VC).

[0117] For the maximum deviation in the weight ratio of coating elements within the wear-resistant protective layer (uniformity of coating element distribution) and other favorable values ​​for the relevant qualitative evaluation performance of the wear-resistant protective layer, please refer to Table 9.

[0118] The uniformity of element distribution can also have a beneficial effect on the performance of wear-resistant protective layers.

[0119] In particular, the chemical elemental composition can be locally determined by analyzing the uniformity of elemental distribution. Both qualitative and quantitative analysis are possible.

[0120] This can be determined, for example, using microanalysis methods such as EDX (energy-dispersive X-ray spectroscopy). EDX analysis allows for advantageous studies of the coating composition. Even unknown materials or impurities related to chemical elements can be analyzed on existing wear-resistant protective layers. The thickness of the wear-resistant protective layer can also be measured.

[0121] Table 9: Uniformity of elemental distribution (qualitative): Uniformity of distribution of hard phase and matrix, hardness, porosity, (compressive) residual stress, anti-delamination and uniformity of layer thickness in each wear-resistant protective layer (evaluation in each case is between 0 and 10, with individual scales between minimum possible (0) and maximum possible (10) (scale name: kg) and neutral (0) and best possible (10) (scale name: nb). In summary, it can be noted that the more uneven the starting materials supplied to the thermal spraying process, the more uneven the resulting wear-resistant protective layer will be. Consequently, the ratio of the hard phase to the matrix in the wear-resistant protective layer will also be more uneven, which will affect several properties of the wear-resistant protective layer.

[0122] The more uneven the hard phase / matrix ratio, the lower the usable hardness of the wear-resistant protective layer. Furthermore, as the unevenness from the hard phase to the matrix increases, more defects appear, leading to an increase in the porosity of the wear-resistant protective layer.

[0123] The uniformity of the coating elements in the wear-resistant protective layer also reduces the available level of residual stress that may occur in the wear-resistant protective layer.

[0124] As a result, the reduced uniformity of the distribution of coating elements also leads to a decrease in the anti-adhesion tensile properties of the wear-resistant protective layer, which is particularly due to the increase in porosity and / or the decrease in the minimum residual stress level.

[0125] Last but not least, increased non-uniformity in the distribution of coating elements in the wear-resistant protective layer can also lead to non-uniformity in the layer thickness of the wear-resistant protective layer.

[0126] The uniformity of the wear-resistant protective layer alone can advantageously improve general-purpose work rolls, making the relevant features or combinations thereof advantageous even without other features of the present invention.

[0127] Furthermore, if the wear-resistant protective layer has a thickness deviation of less than or equal to 20%, preferably less than or equal to 10%, and particularly preferably less than or equal to 5% from the average layer thickness of the wear-resistant protective layer over the total number of measurement points in more than or equal to 80% of the measurement points, especially more than or equal to 90% of the measurement points, and the total number of measurement points is greater than or equal to 10, preferably greater than or equal to 25, and particularly preferably greater than or equal to 40, then the performance of this wear-resistant protective layer may be affected.

[0128] The wear-resistant protective layer preferably has a thickness tolerance of less than or equal to 1µm, more preferably less than or equal to 0.5µm, and particularly preferably less than or equal to 0.2µm.

[0129] Uniformity of layer thickness is a particularly advantageous property of abrasion-resistant protective layers. In other words, a corrugated surface of the abrasion-resistant protective layer is generally not required, but only in special cases. Therefore, for various embodiments of the work roll, abrasion-resistant protective layers with uniform thickness and / or only small thickness deviations are advantageous.

[0130] Preferably, the wear-resistant protective layer has a thickness tolerance of less than or equal to 2µm, more preferably less than or equal to 0.75µm, and particularly preferably less than or equal to 0.35µm.

[0131] The thickness uniformity proposed here can particularly advantageously influence the roughness R of the wear-resistant protective layer. a And / or the waviness of the wear-resistant protective layer.

[0132] By means of the design of thickness uniformity alone, general-purpose work rolls can be advantageously improved, making the relevant features or combinations thereof advantageous even without other features of the present invention.

[0133] Furthermore, it is advantageous if the wear-resistant protective layer has a hard phase and a matrix, wherein the hard phase is embedded in the matrix.

[0134] Experiments have shown that wear-resistant protective layers with hard phases are particularly wear-resistant, thus having an increased service life, especially if at least one hard phase is bonded to a matrix that is softer than the hard phase.

[0135] In the hard phase, there will be at least one particle containing at least one oxide, carbide and / or boride.

[0136] Hard phases particularly advantageously include tungsten carbide (WC), alumina (Al2O3), zirconium oxide (ZrO2), chromium carbide (especially Cr3C2, Cr7C3 and / or Cr 23 C6), vanadium carbide (VC), silicon carbide (SiC), tungsten boride (WB), chromium oxide (especially CrO, Cr2O3, CrO2 and / or CrO3), titanium carbide (TiC), titanium oxide (especially TiO, Ti2O3 and / or TiO2) and / or molybdenum carbide (especially Mo2C and / or MoC).

[0137] Furthermore, it is advantageous if the wear-resistant protective layer has a hard phase and a matrix, particularly the ratio of the hard phase to the total layer system composed of the hard phase and the matrix, which is greater than or equal to 40% by volume, preferably greater than or equal to 50% by volume, particularly preferably greater than or equal to 60% by volume, and / or particularly the ratio of the hard phase to the total layer system is less than or equal to 90% by volume, preferably less than or equal to 85% by volume, particularly preferably less than or equal to 80% by volume, or less than or equal to 75% by volume.

[0138] Table 10: Ratio of hard phase to matrix, i.e., the ratio of hard phase to the total layer system composed of hard phase and matrix: hardness and roughness R of each wear-resistant protective layer. a Density, uniformity of elemental distribution, uniformity of layer thickness distribution, peak number, resistance to adhesion tensile stress, residual stress, and porosity (evaluation in each case is between 0 and 10, with individual scales between minimum possible (0) and maximum possible (10) (scale name: kg) and neutral (0) and best possible (10) (scale name: nb). For the ratio of the hard phase to the matrix in the wear-resistant protective layer and other favorable values ​​for the relevant qualitative evaluation performance of the wear-resistant protective layer, please refer to Table 10.

[0139] It should be clearly stated here that the term "hard phase to matrix ratio" used here is understood quantitatively as the proportion of the hard phase in the wear-resistant protective layer, that is, the ratio of the hard phase to the total layer system composed of the hard phase and the matrix.

[0140] The hard phase / matrix ratio can be used to measure the distribution of elements in the wear-resistant protective layer.

[0141] In this regard, it is advantageous if the hard phase and matrix are present in the optimal ratio, because the more hard phase present, the higher the hardness of the wear-resistant protective layer.

[0142] Furthermore, a higher proportion of hard phase results in more particles protruding from the wear-resistant protective layer, which in turn affects the surface roughness R of the wear-resistant protective layer. a .

[0143] On the other hand, the following applies: the softer the wear-resistant protective layer is formed, the denser the wear-resistant protective layer will be, and as a result, the final thickness of the wear-resistant protective layer can be thinner.

[0144] The softer the wear-resistant protective layer, that is, the lower the proportion of hard phase, the more particles adhere to the surface, thus affecting the uniformity of elements and the uniformity of the thickness of the wear-resistant protective layer.

[0145] Other interactions related to the current ratio of hard phase to matrix, such as peak number, adhesion, residual stress, and / or porosity, may occur on the wear-resistant protective layer.

[0146] By means of the ratio of the hard phase to the total layer system consisting of the hard phase and the matrix, general-purpose work rolls can be advantageously improved, such that the relevant features or combinations thereof are already advantageous without the other features of the present invention.

[0147] Particularly advantageous is that the wear-resistant protective layer contains tungsten carbide (WC), alumina (Al2O3), zirconium oxide (ZrO2), chromium carbide (Cr3C2, Cr7C3 and / or Cr... 23 At least one, two, three, four, five, six, seven or more elements selected from 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), particularly tungsten carbide (WC), aluminum oxide (Al2O3), zirconium oxide (ZrO2), chromium carbide (Cr3C2, Cr7C3 and / or Cr2O3), vanadium carbide (VC), silicon carbide (SiC), tungsten boride (WB), chromium oxide (CrO, Cr2O3, CrO2 and / or Cr2O3), titanium carbide (TiC), titanium oxide (TiO, Ti2O3 and / or TiO2), or molybdenum carbide (Mo2C and / or MoC). 23 One, two, three, four or more elements selected from C6 and / or vanadium carbide (VC).

[0148] In particular, further coating elements can affect the design and performance of this wear-resistant protective layer.

[0149] For example, tungsten carbide (WC), alumina (Al2O3), zirconium oxide (ZrO2), chromium carbide (Cr3C2, Cr7C3 and / or Cr 23 The performance of all wear-resistant protective layers composed of 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) can be affected by the following coating elements, particularly tungsten carbide (WC), alumina (Al2O3), zirconium oxide (ZrO2), chromium carbide (Cr3C2, Cr7C3 and / or Cr... 23 At least one, two, three, four or more elements in all combinations and compositions of C6 and / or vanadium carbide (VC).

[0150] Further effects of the wear-resistant protective layer can be achieved through the hard phase and matrix.

[0151] As mentioned above, the ratio of hard phase to matrix can be advantageously defined based on the coating elements.

[0152] Different coating elements are usually distinguished by different properties, especially different hardness. In this respect, one element or several elements of a wear-resistant protective layer can advantageously affect its hardness and other properties of the wear-resistant protective layer.

[0153] In addition, different coating elements can also affect the residual stress of the wear-resistant protective layer.

[0154] By simply selecting one or more elements of the wear-resistant protective layer, a general-purpose work roll can be advantageously improved, such that the relevant features or combinations thereof are already advantageous in the absence of other features of the present invention.

[0155] It is also advantageous if the wear-resistant protective layer and / or the substrate has a residual compressive stress greater than or equal to -200 N / mm², preferably greater than or equal to 0 N / mm², and particularly preferably greater than or equal to 200 N / mm², and / or the wear-resistant protective layer and / or the substrate has a residual compressive stress less than or equal to 2000 N / mm², preferably less than or equal to 1500 N / mm², and particularly preferably less than or equal to 1000 N / mm².

[0156] At this point, it should be noted that the negative value of residual stress or residual compressive stress should be interpreted as residual tensile stress.

[0157] These values ​​enable improvements in the abrasion resistance of the work roll, particularly by tightly bonding or "clamping" the abrasion-resistant protective layer to the coated component, such as the substrate of this work roll. In this respect, improved layer adhesion can be achieved by forming the proposed residual compressive stress.

[0158] Furthermore, the formation of cracks, especially microcracks, in the wear-resistant protective layer can be offset by appropriate residual compressive stress.

[0159] Furthermore, any microcracks that may appear in the wear-resistant protective layer can be closed again by the residual compressive stress in the wear-resistant protective layer, thereby advantageously reducing or preventing any crack propagation of the microcracks. Similarly, residual tensile stress can support the growth of microcracks.

[0160] Furthermore, the growth of wear-resistant protective layers is often negatively affected by unfavorable residual tensile stress.

[0161] Furthermore, the anti-adhesion tensile properties, hardness, and final thickness of the wear-resistant protective layer can be negatively and positively affected by the corresponding residual stress, as can be seen in Table 11 below.

[0162] The available value range can be determined in different ways, but it is preferred to use the following methods: "ICP sensor monitoring curvature via Tsui and Clyne modes" or "STRAIN-FLEX MSF-2M Rigaku stress analyzer", where residual compressive stress or residual stress is measured in N / mm².

[0163] Further features, effects, advantages, or disadvantages can be found in the illustrations in Table 11 below: Table 11: Residual compressive stress (N / mm²): Abrasion resistance, interlayer adhesion, interlayer adhesion and anti-adhesion tensile strength of each abrasion protective layer (evaluation in each case is between 0 and 10, with individual scales between minimum possible (0) and maximum possible (10) (scale name: kg) and neutral (0) and best possible (10) (scale name: nb). By means of the residual stress in the wear-resistant protective layer and / or the matrix, particularly the residual compressive stress in the wear-resistant protective layer and / or the matrix, general-purpose work rolls can be advantageously improved, such that the relevant features or combinations thereof are already advantageous in the absence of other features of the present invention.

[0164] Furthermore, it is also advantageous if the wear-resistant protective layer and / or the substrate has a peak number of RPc values ​​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 has a peak number of RPc values ​​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.

[0165] By utilizing the values ​​for the number of peaks mentioned here, a particularly advantageous surface for the wear-resistant protective layer can be formed, especially a particularly advantageous texture for the surface of the wear-resistant protective layer.

[0166] In particular, this can also affect the adhesion between the wear-resistant protective layer and the substrate.

[0167] However, it should be noted that a high peak count on the substrate does not directly lead to a high peak count in the wear-resistant protective layer. Therefore, the peak count of the wear-resistant protective layer is not solely determined by the peak count of the substrate.

[0168] It has been proven that for higher arithmetic mean roughness R... a This allows for a higher peak count, while a lower arithmetic mean roughness R can be achieved. a This can also result in a higher peak count.

[0169] The current peak count is in "peaks per centimeter". For more information on peak count, please refer to DIN 10049-2014.

[0170] By means of the feature concerning the number of peaks alone, general-purpose work rolls can be advantageously improved, such that the relevant feature or combination of its features is already advantageous in the absence of other features of the present invention.

[0171] Particularly advantageous is that the wear-resistant protective layer has an oxide ratio of less than or equal to 5% by weight, preferably less than or equal to 3% by weight, and particularly preferably less than or equal to 1.5% by weight, especially the ratio of chromium oxide (CrO, Cr2O3, CrO2 and / or CrO3) and / or aluminum oxide (Al2O3) and / or zirconium oxide (ZrO2) and / or titanium oxide (TiO, Ti2O3 and / or TiO2).

[0172] Among other things, a lower oxide ratio can be obtained by using a thermal spraying device with a λ value close to 1 or 1.

[0173] Experiments have shown that increasing the oxide ratio reduces the service life of the wear-resistant protective layer and / or, in the case of a multilayer structure of the wear-resistant protective layer, negatively affects the layer adhesion of adjacent layers.

[0174] If the matrix has an arithmetic mean roughness R aThe roughness is greater than or equal to 0.1 µm, preferably greater than or equal to 0.2 µm, particularly preferably greater than or equal to 0.3 µm, and / or the arithmetic mean roughness R a A surface area to be coated that is less than or equal to 14 µm, preferably less than or equal to 4.0 µm, and particularly preferably less than or equal to 0.8 µm, has also proven to be advantageous.

[0175] By means of the roughness R of the substrate surface a It can also advantageously affect the wear-resistant protective layer, for example, the final roughness R of the wear-resistant protective layer. a Furthermore, it can also affect its uniformity. Here, we can assume that the roughness R of the material to be coated (the substrate) is... a The higher the surface roughness R of the wear-resistant protective layer, the better. a The higher the roughness R of the material to be coated (substrate), the better. a The higher the temperature, the greater the deviation in layer thickness, which will negatively affect the uniformity of the wear-resistant protective layer thickness.

[0176] The roughness of the substrate surface also affects the particle adhesion and therefore the layer adhesion relative to the wear-resistant protective layer.

[0177] The roughness R mentioned here is relative to the substrate surface. a It can be generated in different ways, wherein the roughness R a Many of these can be achieved, for example, by means of the outer surface (substrate surface) of the grinding work roll, such as a roughness R of 0.3µm to 0.8µm. a .

[0178] Further features, effects, advantages, or disadvantages can be found in the illustrations in Table 12 below: Table 12: Average roughness R of the wear-resistant protective layer a (µm): Layer roughness, layer thickness, uniformity of wear-resistant protective layer, residual stress of wear-resistant protective layer and anti-adhesion tensile strength of wear-resistant protective layer (evaluation in each case is between 0 and 10, with individual scales between minimum possible (0) and maximum possible (10) (scale name: kg) and neutral (0) and best possible (10) (scale name: nb). By means only of the arithmetic mean roughness R a The features can advantageously improve general-purpose work rolls, making the relevant features or combinations thereof already advantageous in the absence of other features of the invention.

[0179] It was also found that it is advantageous if the matrix has a hardness value greater than or equal to 35 HRC, preferably greater than or equal to 40 HRC, particularly preferably greater than or equal to 50 HRC, and / or a hardness value less than or equal to 70 HRC, preferably less than or equal to 65 HRC, particularly preferably less than or equal to 60 HRC.

[0180] In particular, the adhesion of the wear-resistant protective layer to the substrate of the work roll can be advantageously influenced or adjusted by means of the additional hardness values ​​of the substrate given here.

[0181] If the substrate hardness is chosen to be too soft, the components of the wear-resistant protective layer may adversely penetrate into the substrate. If the substrate hardness is too hard, there is a risk that a critical amount of the coating material may bounce off the substrate when applied.

[0182] In addition, the following points must be considered regarding the hardness of the matrix: The harder the substrate, the lower the anti-adhesion tensile strength of the wear-resistant protective layer, which makes it easier for the wear-resistant protective layer to detach from the substrate.

[0183] The harder the matrix is ​​designed, the higher the risk of more defects appearing in the matrix wear-resistant protective layer composite material, which in turn increases the risk of delamination.

[0184] This defect also typically increases porosity, which negatively impacts the adhesion between the wear-resistant protective layer and the substrate.

[0185] Furthermore, defects can affect the residual stress of the wear-resistant protective layer, and vice versa.

[0186] In addition, the adhesion mechanism during the spraying process can affect the roughness and thickness of the wear-resistant protective layer.

[0187] The harder the wear-resistant protective layer, the higher its surface roughness R. a The greater the impact, the more likely it is to be.

[0188] The matrix hardness HRC of the present invention is preferably measured by a macroscopic identification method.

[0189] Further features, effects, advantages, or disadvantages can be found in the illustrations in Table 13 below: Table 13: Matrix Hardness (HRC): Porosity, defect frequency, anti-adhesion tensile strength, residual stress and layer thickness of each wear-resistant protective layer (evaluation in each case is between 0 and 10, with individual scales between minimum possible (0) and maximum possible (10) (scale name: kg) and neutral (0) and best possible (10) (scale name: nb). By means of only the characteristics relating to the matrix hardness, general-purpose work rolls can be advantageously improved, such that the relevant features or combinations thereof are already advantageous in the absence of other features of the present invention.

[0190] In addition, other design options for the substrate can advantageously influence the wear-resistant protective layer, such as the material used to manufacture the substrate.

[0191] The selected dimensions of the substrate, such as its width, diameter, length, and the support width between the substrate's support points, also affect the quality of the wear-resistant protective layer.

[0192] In any case, by virtue of the above features and taking into account legal requirements for avoiding hard chrome, work rolls used for rolling metal products, especially their wear-resistant protective layers, can be advantageously adapted individually to different requirements.

[0193] According to another aspect, the object of the present invention is also achieved by a rolling mill stand having a work roll having one of the features described herein.

[0194] The object of the invention is also achieved by a metal strip, wherein the metal strip is cold-rolled using a work roll according to one of the features described herein.

[0195] Based on the surface images obtained on the metal strip, certain features of the wear-resistant protective layer can be advantageously identified. In particular, when rolling the metal strip, the texture of the wear-resistant protective layer on the work roll can be transferred from the surface of the work roll, especially the surface of the wear-resistant protective layer, to the surface of the metal strip.

[0196] The object of the present invention is also achieved by a method for manufacturing the work roll, wherein its wear-resistant protective layer is applied to a previously provided substrate by a thermal spraying process.

[0197] Therefore, it is advantageous to manufacture work rolls with wear-resistant protective layers.

[0198] In particular, with the help of thermal spraying, even different powder compositions can be easily and precisely applied to the substrate of the work roll to produce a process-specific wear-resistant protective layer.

[0199] If the wear-resistant protective layer is smoothed by the abrasive after application, it can be further easily adapted. As an example only, it should be mentioned that this allows for further adjustment of the surface roughness of the wear-resistant protective layer on the work roll.

[0200] In particular, increasing the number of powder conveyors can advantageously improve this method, resulting in a more uniform powder distribution. Consequently, the quality of the wear-resistant protective layer on the work rolls can also be further improved.

[0201] In this regard, it is also required that the described method can be supplemented by other technical features mentioned herein, in particular by features of the work roll or its wear-resistant protective layer, so as to advantageously improve the method or enable a more precise representation or specification of the method.

[0202] The powder conveyor can preferably be arranged above the burner (e.g., a high-velocity oxygen fuel (HVOF) burner or a high-velocity air fuel (HVAF) burner) used for thermal spraying of wear-resistant protective layers, thereby conveniently increasing the static pressure used to introduce the powder into the burner.

[0203] Furthermore, regarding powder preparation, it may be advantageous for the design of this wear-resistant protective layer if any powder is preheated to produce a wear-resistant protective layer.

[0204] Additional sieving of the powder can provide a more uniform powder distribution.

[0205] Similarly, proper preheating or powder screening can advantageously influence the fabrication of the wear-resistant protective layer, particularly in terms of bending / belt dimensions, in order to optimize residual stress relative to the wear-resistant protective layer.

[0206] The object of the present invention is also achieved by a work roll for cold-rolled metal strip according to one of the features described herein.

[0207] By using the work rolls of the present invention, high-quality surfaces can be produced on cold-rolled metal strips, especially over a longer period of time.

[0208] The aforementioned measures, particularly the selection of coating materials and, especially, the selection of more complex coating parameters, can greatly contribute to providing a high-quality wear-resistant protective layer for the rolling of metal strips in this situation.

[0209] Other advantages, details and features of the invention also arise from the embodiments explained below.

[0210] In the attached diagram: Figure 1 A view of a work roll for rolling metal products is shown, in which a wear-resistant protective layer is thermally sprayed onto the substrate of the work roll. Figure 2 schematically shown Figure 1 A partial cross-sectional view showing details of the working roller.

[0211] according to Figure 1 The manufacture of a work roll 1 for rolling metal products (not shown), and particularly for rolling metal strips (also not shown), is schematically shown.

[0212] In this case, the work roll 1 is processed by means of thermal spraying. More specifically, a wear-resistant protective layer 2 is applied to the surface 3 of the substrate 4 of the work roll 1.

[0213] The thermal spraying of the wear-resistant protective layer 2 is carried out by means of a suitable thermal spraying device 5, which has a burner 6, such as an HVOF burner or an HVAF burner, wherein multiple powder conveyors 7 (shown and numbered only as an example) are arranged above the burner 6, at least some of which can preheat the powder 8.

[0214] As claimed in this invention, powder 8 can be made by mixing together multiple powder components 9 individually.

[0215] The powder conveyor 7 also has a device 10 for screening powder 8 or its powder components 9.

[0216] With the aid of the thermal spraying device 5, when the work roller 1 rotates about its bearing axis 12 in the direction of rotation 12, the coating material 11, which is particularly advantageously assembled, can be applied integrally to the substrate 4 of the work roller 1.

[0217] according to Figure 2 The illustration shows the details of the work roll 1 as a cross-sectional view of the boundary region 20 between the wear-resistant protective layer 2 and the substrate 4.

[0218] In particular, the tip 22 of the roughness (not numbered again) of the boundary surface 24 of the substrate surface 3 is easily identifiable, wherein the tip 22 also forms a cavity 26 on the substrate surface 3.

[0219] The tip 22 and the cavity 26 form the roughness of the boundary surface 24, which is shown as a serrated line (not numbered again).

[0220] The wear-resistant protective layer 2 has hard phase particles 28 (dashed line structure) of different particle sizes (not numbered again) embedded in the matrix 30 of the wear-resistant protective layer 2.

[0221] In this embodiment, the identifiable particle size is on average between 5 µm and 25 µm.

[0222] If the wear-resistant protective layer 2 has special properties, the particle size can also be between 10 µm and 20 µm (see Table 1).

[0223] To give just a few more specific examples, an average particle size between 30 µm and 45 µm is also possible.

[0224] Other favorable particle sizes can be found in Table 1 to enable the achievement of other favorable properties with respect to the wear-resistant protective layer 2.

[0225] It can be clearly seen how the hard phase particles 28 are pressed into the cavity 26, and in this case, they partially abut against the side 32 of the tip 22 in a frictionally locked manner over a large surface area.

[0226] In boundary region 20, there may be higher residual compressive stress than in areas further away from boundary region 20.

[0227] With the appropriate setting of high residual compressive stress, the wear-resistant protective layer 2 is pressed more strongly onto the substrate 2, especially into the cavity 26, and the hard phase particles 28 of the wear-resistant protective layer 2 also interact more closely with the side surface 32.

[0228] In general, the residual compressive stress, in particular, between 500 N / mm² and 1500 N / mm², ensures a particularly tight bond between the wear-resistant protective layer 2 and the substrate 4, and thus also ensures particularly good anti-adhesion tensile properties.

[0229] Even the hard phase particles 28 within the matrix 30 can be more tightly "clamped" together under this residual compressive stress.

[0230] List of reference numerals 1. Working roll 2 Wear-resistant protective layer 3 Surface 4. Matrix 5. Thermal spraying equipment 6. Powder conveyor 7. Screening equipment 8 Powder 9 powder ingredients 10. Screening equipment 11 Coating Materials 12. Rotation direction 20 Boundary Area 22 Tips 24 Boundary Surface 26. Cavity 28 Hard phase particles or particle size 30 substrate 32 Side View

Claims

1. Work roll (1) for rolling metal products, in particular for rolling metal strips, comprising: - a metal base body (4); and - a wear-resistant protective layer (2) arranged at least partially on the base body (4), wherein the wear-resistant protective layer (2) is a thermal spray protective layer; characterized in that the wear-resistant protective layer (2) has a grain size of less than or equal to 50 pm, preferably less than or equal to 45 pm, particularly preferably less than or equal to 30 pm or less than or equal to 20 pm. the wear-resistant protective layer (2) has a grain size of greater than or equal to 2 pm, preferably greater than or equal to 5 pm.

2. The work roll (1) according to claim 1, characterized in that the wear-resistant protective layer (2) has a proportion of chromium of less than or equal to 90% by weight, preferably less than or equal to 60% by weight, particularly preferably less than or equal to 30% by weight.

3. The work roll (1) according to any one of claims 1 or 2, characterized in that the wear-resistant protective layer (2) has a proportion of nickel of less than or equal to 90% by weight, preferably less than or equal to 60% by weight, particularly preferably less than or equal to 30% by weight.

4. Work roll (1) according to any of the preceding claims, characterized in that the wear-resistant protective layer (2) has a proportion of tungsten carbide (WC) of greater than or equal to 50% by weight, preferably greater than or equal to 60% by weight, particularly preferably greater than or equal to 70% by weight.

5. Work roll (1) according to any of the preceding claims, characterized in that The wear-resistant protective layer (2) has an arithmetic average roughness R a greater than or equal to 0.01 pm, preferably greater than or equal to 0.5 pm, particularly preferably greater than or equal to 1.5 pm, and / or an arithmetic average roughness R a of the outer surface is less than or equal to 17 pm, preferably less than or equal to 10 pm, particularly preferably less than or equal to 6 pm.

6. Work roll (1) according to any of the preceding claims, characterized in that the wear-resistant protective layer (2) has a proportion of tungsten precipitates, in particular elemental tungsten (W) and / or ditungsten carbide (W2C), which is less than or equal to 50% by weight, preferably less than or equal to 33% by weight, particularly preferably less than or equal to 10% by weight or less than or equal to 5% by weight.

7. Work roll (1) according to any of the preceding claims, characterized in that the wear-resistant protective layer (2) has a layer thickness of greater than or equal to 2 pm, preferably greater than or equal to 5 pm, particularly preferably greater than or equal to 10 pm, and / or has a layer thickness of less than or equal to 80 pm, preferably less than or equal to 40 pm, particularly preferably less than or equal to 15 pm.

8. Work roll (1) according to any one of the preceding claims, characterized in that the wear-resistant protective layer (2) has an adhesive tensile value of greater than or equal to 60 N / mm2, preferably greater than or equal to 70 N / mm2, particularly preferably greater than or equal to 80 N / mm2or greater than or equal to 100 N / mm2.

9. Work roll (1) according to any one of the preceding claims, characterized in that the wear-resistant protective layer (2) has a porosity value of less than or equal to 1%, preferably less than or equal to 0.5%, particularly preferably less than or equal to 0.1% porosity.

10. Work roll (1) according to any one of the preceding claims, characterized in that the wear-resistant protective layer (2) has a permeability value of less than or equal to 1%, preferably less than or equal to 0.5%, particularly preferably less than or equal to 0.1% permeability.

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

12. Work roll (1) according to any one of the preceding claims, characterized in that ​ 13. Work roll (1) according to any one of the preceding claims, characterized in that At more than or equal to 80% of the analysis points, preferably more than or equal to 90% of the analysis points, particularly preferably more than or equal to 95% of the analysis points, the wear protection layer (2) has a deviation of less than or equal to 40%, preferably less than or equal to 30%, particularly preferably less than or equal to 20% from the average weight proportion of the coating elements over the total number of analysis points, wherein the total number of analysis points is more than or equal to 5, preferably more than or equal to 15, particularly preferably more than or equal to 25, particularly preferably the coating elements are one of tungsten carbide (WC), aluminium oxide (AI2O3), zirconium oxide (ZrO2), chromium carbide (Cr3C2, Cr7C3 and / or Cr 23 C6) or vanadium carbide (VC).

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

15. Work roll (1) according to any 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, in particular less than or equal to 0.2 pm.

16. Work roll (1) according to any 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 any 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 the hard phase to the total layer system consisting of hard phase and matrix, which has a ratio value of more than or equal to 40% by volume, preferably more than or equal to 50% by volume, in particular more than or equal to 60% by volume, and / or in particular a ratio value of the hard phase to the total layer system of less than or equal to 90% by volume, preferably less than or equal to 85% by volume, in particular less than or equal to 80% by volume, or less than or equal to 75% by volume.

18. Work roll (1) according to any one of the preceding claims, characterized in that The wear protection layer (2) has at least one, two, three, four, five, six, seven or more elements of 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 elements of tungsten carbide (WC), aluminum oxide (AI2O3), zirconium oxide (ZrO2), chromium carbide (Cr3C2, Cr7C3 and / or Cr 23 C6) and / or vanadium carbide (VC).

19. Work roll (1) according to any one of the preceding claims, characterized in that The wear protection layer (2) and / or the substrate (4) has a residual compressive stress with a value of more than or equal to -200 N / mm2, preferably more than or equal to 0 N / mm2, in particular more than or equal to 200 N / mm2, and / or the wear protection layer (2) and / or the substrate (4) has a residual compressive stress with a value of less than or equal to 2000 N / mm2, preferably less than or equal to 1500 N / mm2, in particular less than or equal to 1000 N / mm2.

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

21. Work roll (1) according to any of the preceding claims, characterized in that The wear protection layer (2) has an oxide proportion, in particular a proportion of aluminum oxide (AI2O3) 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% by weight, preferably less than or equal to 3% by weight, in particular less than or equal to 1.5% by weight.

22. Work roll (1) according to any of the preceding claims, characterized in that The substrate (4) has an arithmetic average roughness R a greater than or equal to 0.1 pm, preferably greater than or equal to 0.2 pm, particularly preferably greater than or equal to 0.3 pm, and / or an arithmetic average roughness R a less than or equal to 14 pm, preferably less than or equal to 4.0 pm, particularly preferably less than or equal to 0.8 pm.

23. Work roll (1) according to any of the preceding claims, characterized in that The substrate (4) has a substrate hardness with a hardness value of more than or equal to 35 HRC, preferably more than or equal to 40 HRC, in particular more than or equal to 50 HRC, and / or a substrate hardness with a hardness value of less than or equal to 70 HRC, preferably less than or equal to 65 HRC, in particular less than or equal to 60 HRC.

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

25. A metal strip, wherein, The metal strip is cold-rolled with the work roll (1) according to any one of claims 1 to 23.

26. A method for manufacturing a work roll (1) according to any one of claims 1 to 23, comprising the steps of: - providing the base body (4); and - applying the wear-resistant protective layer (2) by a thermal spraying process.

27. The method of claim 26, wherein, The wear-resistant protective layer (2) is abraded smooth after application.

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

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