Mechanically, in particular tribologically, stressed component and method for its production

Abstract

The invention relates to a mechanically, in particular tribologically, stressed component in a rolling mill, the component comprising a main body of a base material and at least one functional layer (3) applied to the main body and consisting of at least one material different from the base material, wherein the material of the at least one functional layer (3) has a greater wear resistance than the base material, wherein the main body comprises at least one further, outer layer as a sacrificial layer (5), which at least partially encloses the at least one functional layer (3), and the sacrificial layer (5) consists of a material which has a lower wear resistance than the at least one functional layer (3). The invention also relates to a method for producing or restoring such a component.

Description

[0001] Mechanically, in particular tribologically stressed component and method for its production

[0002] The invention relates to a mechanically, in particular tribologically, stressed component in a rolling mill, as well as a method for producing or repairing such a component. A mechanically, in particular tribologically stressed component within the meaning of the invention can be, for example, a sliding guide, a linear guide, a guide bar, or a roller or roll that, for example, is in contact with the rolling stock and is designed as a wear partner with regard to its material configuration.

[0003] The invention particularly relates to a roller for engaging rolled stock in a rolling mill and to a method for producing or restoring a roller for engaging rolled stock in a rolling mill, in particular in a hot rolling mill.

[0004] Such a roller is known, for example, from WO 2009 / 130079A1. This publication relates to a roller for transporting continuously cast steel strands on a roller table or in a continuous casting machine, comprising a roller body comprising a roller shell made of a base material and a wear layer applied by build-up welding to the base material with a filler metal, which wear layer encloses the roller shell surface, the base material of the roller shell being steel. The build-up welding is implemented as a single-layer weld. The roller is restored after wear by preparing the roller shell as a turned part and applying a single-layer build-up weld to the base material with a specific minimum thickness. The weld layer is then turned back to a closed, single-surface roller shell surface while maintaining a minimum thickness of the wear layer.During operation, mechanical components are often subjected to loads that vary locally and do not spread evenly across the component. In particular, a difference is often observed between the core and the edge of a component. For predominantly cylindrical components, such as discs and shafts or rollers, as well as other components with flat surfaces, the core is often required to exhibit high ductility at low loads, while the boundary area near the surface is subjected to high mechanical, thermal, and / or corrosive stress.

[0005] For this reason, it is generally known to provide rollers, such as those described in WO 2009 / 130079A1, with coatings that perform different functions, for example increased wear resistance, increased bending or torsion resistance under static, dynamic or oscillating loads, increased temperature resistance, a certain thermal expansion or thermal conductivity, and increased corrosion resistance.

[0006] As described above, it is known to apply such functional layers by deposition welding, thermal spraying, vapor deposition, dusting, electroplating or chemical coating, or casting. Often, a specific surface quality, such as a defined roughness and waviness, is required for such components. This surface quality is not necessarily present after the application of the functional layers; rather, it must be achieved through appropriate post-processing, such as turning, milling, or grinding.

[0007] For components that are to be given increased wear resistance by applying a so-called functional layer, the creation of certain surface properties through post-processing is naturally relatively complex, since a wear-resistant material is more resistant to post-processing than a material that is less wear-resistant.

[0008] The invention is therefore based on the object of providing a component for engagement, in particular, in hot rolling stock in a rolling mill, which is optimized with regard to its wear properties and which can be manufactured relatively easily and / or which can be easily restored.

[0009] The invention is further based on the object of providing a corresponding method for producing and / or restoring such a component.

[0010] The object is achieved by the features of claims 1 and 8. Advantageous embodiments of the invention emerge from the subclaims.

[0011] According to one aspect of the invention, a mechanically, in particular tribologically stressed component is provided with a base body made of a base material and at least one functional layer applied to the base body, wherein the material of the at least one functional layer has a higher wear resistance than the base material, wherein the base body comprises at least one further outer layer as a sacrificial layer, which at least partially encloses the at least one functional layer and the sacrificial layer consists of a material which has a lower wear resistance than the at least one functional layer.

[0012] A mechanically stressed component within the meaning of the invention is, for example, a component designed as a wear partner for engaging with the rolling stock or for guiding the rolling stock. The term "component" within the meaning of the invention includes, for example, but is not limited to, sliding guides in roller tables, guide rails, rollers, or rolls, including, for example, backup rolls that interact with other rolls.

[0013] Preferably, the at least one functional layer consists of a relatively harder and / or more wear-resistant material than the sacrificial layer.

[0014] According to a further aspect of the invention, a roller for engaging in hot rolling stock in a hot rolling mill is provided as a component within the meaning of the invention, which roller has a roller body which comprises a roller shell made of a base material and at least one functional layer made of at least one material different from the base material, wherein the material of the at least one functional layer has a higher wear resistance than the base material, wherein the roller body comprises at least one further outer layer as a sacrificial layer which at least partially encloses the at least one functional layer and the sacrificial layer consists of a material which has a lower wear resistance than the at least one functional layer.

[0015] A roller for engaging hot rolled stock within the meaning of the present invention is a roller or roll as a roller table roller, roll of a rolling mill, roll of a continuous casting machine or continuous casting guide or another unit which is intended for supporting, treating and / or transporting the hot rolled stock.

[0016] The roller body and / or the roller shell are, for example, essentially cylindrical, although the outer surface of the roller can also be conical or cambered. The shell body of the roller can comprise a plurality of layers that can form a composite with corresponding material properties. At least one outer layer of the roller shell is designed as a so-called functional layer, meaning that the material of the functional layer has the desired properties for engagement with the rolled stock with regard to wear resistance, temperature resistance, hardness, or ductility.

[0017] A functional layer in the sense of the invention is understood to mean a wear protection layer which consists of a material which is more wear-resistant with respect to the base material of the roller body and / or with respect to other layers of the roller.

[0018] Preferably, the sacrificial layer does not meet all the requirements for engagement with the rolled stock; in particular, this sacrificial layer has lower wear resistance. With regard to surface quality (roughness, waviness, and dimensional accuracy), the sacrificial layer can nevertheless meet the desired application-specific properties.

[0019] In principle, the roller shell can comprise one or more supplementary layers arranged beneath at least one functional layer. Supplementary layers can perform various functions, e.g., separating two hard and brittle layers to prevent cracking or separating two different hard layers to prevent mixing, but can also function as a sacrificial layer.

[0020] The supplementary layers can, for example, have lower strength and greater ductility than the other layers, thus allowing the reduction of stresses and the prevention of cracks in the boundary area to a functional layer of high hardness and wear resistance.

[0021] The term sacrificial layer means that this partial layer does not have the properties required by the application, for example in a rolling mill, but that a partial layer or part of the entire layer is deliberately applied in order to provide the underlying layer area with particularly advantageous properties or to generally promote its effective, optimal use for the application.

[0022] The sacrificial layer can, for example, be applied above a hard layer and form the outermost surface of the roller. This surface can be machined to provide a desired surface quality, such as a specific surface roughness.

[0023] The sacrificial layer can completely or partially enclose an outer functional layer. If the roll has an additional soft layer above a hard layer that has been mechanically reworked, this has various advantages. This makes it easier to achieve a good surface quality during coating. Furthermore, mechanical processing of the sacrificial layer is much simpler. The sacrificial layer can be reworked using a simpler and more cost-effective process, such as turning or re-turning to a nominal diameter. Finally, the tool used for this is cheaper and easier to handle. The valuable hard layer or functional layer is completely or almost completely preserved, since the application and removal of the softer layer can be optimally tailored to the application.The thickness of the softer layer can be freely selected within wide limits and thus adapted to the requirements of the overall system. Maintaining the functional layer is one aspect of the invention, particularly when the functional layer has a property gradient in which the best properties are achieved directly at the surface.

[0024] This also increases the design flexibility when applying the hard layer. In preferred embodiments, this can be one layer with a structural and property gradient, or multiple layers with a structural and property gradient from layer to layer, or multiple layers with a structural and property gradient from layer to layer and within the layers. If, for example, a material removal of 200 to 500 micrometers were required after coating, a complex optimization of alloy composition and process parameters with the aim of achieving optimal properties near the edge, e.g., in the form of high strength or good corrosion resistance, would often be pointless.Sophisticated modern coating concepts, in which, for example, the proportion of hard foreign phases such as tungsten carbide or titanium carbide increases continuously (in one layer) or discontinuously (from layer to layer) or both continuously and discontinuously, could find no or only limited application in this case.

[0025] The disadvantages of the prior art are overcome according to the invention by applying a preferably softer sacrificial layer or cover layer, which is partially or almost completely removed during mechanical processing. Any residues of the soft layer are quickly removed during industrial use due to their low wear resistance and do not impair the functionality of the layer. The hard layer can then be used exactly for its original purpose because it is completely preserved. The property profile, which correlates with the macroscopic and microscopic structure of the layer, can thus be adjusted according to specifications or as desired. A thickness that is not exactly uniform across the length and width or across the surface due to the lack of processing of this hard layer can result in a thickness that is not exactly uniform across the length and width.The axial and tangential stresses level off during operation due to the resulting mechanical stress. An optimal combination of application and subsequent partial removal of the entire layer ensures that, on the one hand, the technical properties are particularly advantageous and, on the other hand, the product's cost-effectiveness is maximized.

[0026] It is preferably provided that the at least one functional layer consists of a relatively harder and / or more wear-resistant material than the sacrificial layer.

[0027] For example, in a rotationally symmetrical component such as a roller, the functional layer can have a radially extending structural and / or property gradient. For example, the functional layer can have a hardness gradient from the inside to the outside, for example, from softer to harder.

[0028] The functional layer can, for example, comprise a steel containing a certain proportion of hard foreign phases such as tungsten carbide or titanium carbide. These foreign phases can be distributed in a single layer, i.e., continuously, in such a way that a hardness gradient is achieved. Such a hardness gradient is readily achieved when a hard functional layer within the meaning of the present invention forms the outer surface of the component or, for example, the roller shell of the roller with a softer cover layer as a sacrificial layer. The sacrificial layer allows the set gradient to be maintained.

[0029] Almost all common steel grades can be considered as the material for the base body of the component, for example structural steels such as S355J or tempering steels such as 25CrMo4

[0030] A wear-resistant hot-work steel such as 1.2344 or a high-speed steel such as 1.3344 can be considered as a material for at least one functional layer. Martensitic stainless steels, for example, based on 1.4057, nickel-based alloys such as Inconel 625 and Inconel 718, or cobalt-based alloys such as Stellite 6 and Stellite 21 are also suitable. Particularly wear-resistant layers also contain hard phases such as tungsten carbides and / or titanium carbides. In extreme cases, the volume fraction of the hard phases can exceed that of the matrix.

[0031] In a preferred embodiment of the component or roller according to the invention, a plurality of functional layers are provided which have different properties and / or consist of different materials.

[0032] The plurality of functional layers can, for example, form a radial structural and / or property gradient of the roller shell.

[0033] In a preferred variant of the component according to the invention, its outer surface is designed as a single-surface surface, i.e., it has no steps or diameter changes. As already mentioned above, the outer surface of a roller as a component can be cylindrical, conical, cambered, or S-shaped.

[0034] A further aspect of the invention relates to a method for producing or restoring a mechanically, in particular tribologically stressed component according to one of claims 1 to 8, with a base body made of a base material and at least one functional layer applied to the base body, which comprises at least one material different from the base material, comprising the following method steps:

[0035] Providing a base body made of a base material,

[0036] Applying at least one wear-resistant functional layer to the base body,

[0037] Applying an outer sacrificial layer to the functional layer, wherein the sacrificial layer consists of a material which differs from the material properties of the functional layer and which has a lower wear resistance than the at least one functional layer,

[0038] Reworking of the base body with material removal on a surface that is at least closed in the area of ​​a functional surface with specified

[0039] Dimensions.

[0040] The process steps are preferably carried out in the order in which they are listed.

[0041] The application of the at least one functional layer and / or the sacrificial layer is preferably selected from a group of methods comprising build-up welding, thermal spraying, plasma coating, casting, centrifugal casting, vapor deposition, dusting, galvanic coating, chemical coating.

[0042] Reworking can be done, for example, by turning and / or milling and / or grinding.

[0043] The thickness of the at least one functional layer and / or the sacrificial layer can be selected such that the sacrificial layer at least partially encloses the at least one functional layer after the material removal.

[0044] For example, the lateral surface can be manufactured as a single-surface lateral surface. In a variant of the process, a plurality of functional layers can be applied, each having different properties and / or consisting of different materials, such that the plurality of functional layers forms a structural and / or property gradient.

[0045] A further aspect of the invention relates to a method for producing or restoring a roll for engaging hot rolling stock in a hot rolling mill, in particular for producing or restoring a roll with a roll body comprising a roll shell made of a base material and at least one functional layer made of at least one material different from the base material, comprising the following processing steps:

[0046] Providing a roller body with a roller shell made of a base material,

[0047] Applying at least one wear-resistant functional layer to the roller body,

[0048] Applying an outer sacrificial layer to the functional layer, wherein the sacrificial layer consists of a material which differs from the material properties of the functional layer in terms of material properties and which has a lower wear resistance than the at least one functional layer,

[0049] Reworking the roller shell by reducing the diameter to a closed roller shell surface with a specified outer diameter.

[0050] The process steps are preferably carried out in the order in which they are listed. The application of the at least one functional layer and / or the sacrificial layer can be carried out, for example, by deposition welding, thermal spraying, casting, vapor deposition, plasma coating, centrifugal casting, dusting, electroplating, or chemical coating.

[0051] The method according to the invention may further comprise utilizing the heat supplied during the application of the sacrificial layer to influence the ductility of the underlying functional layer. The functional layer is subjected to an annealing process by the sacrificial layer.

[0052] Post-processing can be done by turning and / or milling and / or grinding.

[0053] Preferably, the thickness of the at least one functional layer and / or the sacrificial layer is selected such that the sacrificial layer at least partially encloses the at least one functional layer after the diameter reduction of the roller shell.

[0054] The roller shell surface is preferably constructed as a single-surface shell surface. This can, for example, be completely closed.

[0055] The method according to the invention can provide for the application of a plurality of functional layers that have different properties and / or consist of different materials, such that the plurality of functional layers form a preferably radial structural and / or property gradient of the roller shell. The described layers with the corresponding properties can be adapted to different loads acting on the roller shell at different times in such a way that the best possible roller shell properties are achieved with respect to the respective external loads, depending on the arrangement of the layers on the roller.

[0056] The wear and / or load resistance of the roller according to the invention can, for example, be optimized in an application-oriented manner, wherein a method for application-oriented optimization can comprise the acquisition of tribological data during the manufacture and / or restoration of at least one roller, the acquisition of wear and / or load data resulting from the operational use of the roller, the correlation of the tribological data from the manufacture and / or restoration of the roller with the wear and / or load data from the operation of an electronic database and the automatic load-oriented design and / or modification of the structure of the roller shell and / or the automatic modification of the operational load of the roller.

[0057] The optimization of wear and / or load resistance of the component or roller can also be carried out, for example, using data regarding material removal during operation and / or during the restoration of the component.

[0058] The tribological data are preferably measurement data selected from a group of measurement data comprising torques, cutting forces, feed forces, frictional forces, friction coefficients and temperatures during machining of the component or the roller shell and surface roughness of the roller shell surface immediately after machining of the roller shell.

[0059] The tribological data can be recorded both location-related and time-related with regard to the geometry of a roller.

[0060] The wear and / or load data from the operation of the roller are preferably measured data, which are either recorded temporarily on the roller in operation or recorded online during operation.

[0061] The wear data may include measured surface properties selected from a group of measurement data on roughness, waviness, profile, surface hardness, friction coefficient of the outer surface of the roller and the structure of the wear traces in the outer surface of the roller.

[0062] Machining processes with geometrically defined and indeterminate cutting edges can also be considered tribometers. Therefore, the recording of material removal and the associated resulting parameters such as surface quality as well as the shape and position of the surfaces can be taken into account to optimize the wear and / or load resistance of the component.

[0063] The load data can be selected from a group of data comprising the point loads acting on the roll, line loads, surface pressures, the rotational speeds and the slip of the roll as well as the temperature and / or nature of the rolling stock and / or the media used in rolling stock cooling.

[0064] The method may comprise an automatic evaluation of the corrected data with the aid of at least one expert system and / or using methods based on machine learning methods, in particular based on artificial neural networks, deep artificial neural networks, decision trees, ensemble methods based on decision trees, linear or non-linear regression models with or without regularization, support vector machines with linear, polynomial or other kernel functions, or the like.

[0065] The invention is explained below with reference to an embodiment illustrated in the drawings. They show:

[0066] Figure 1 is a schematic representation of a partial section through a roller designed according to the prior art,

[0067] Figure 2 is a schematic representation of several manufacturing stages of the roll shown in Figure 1,

[0068] Figure 3 is a schematic representation of the manufacturing or restoration process of a roll according to the invention by means of several partial sectional views,

[0069] Figure 4 shows a partial section through a roller according to the invention after a certain operating time and

[0070] Figure 5 is a schematic representation of a multi-layer system of a roll according to the invention.

[0071] Reference is first made to Figures 1 and 2, which show several partial sectional views of a prior art roller in various stages of manufacture. The reference numerals used in relation to Figures 1 and 2 are equally used for the roller according to the invention shown in Figures 3 to 5.

[0072] The roller 1 shown in Figures 1 and 2 is shown as a partial sectional view, with the sectional view shown above an axis of symmetry of the roller 1. The roller 1 comprises a roller body 2 made of steel as the base material and a shell layer comprising a so-called functional layer 3. A supplementary layer 4 can be arranged below the functional layer 3.

[0073] Either during new production or during restoration of the roller 1, the functional layer is generally applied as a wear-protection layer with appropriate material properties, for example by build-up welding, to the supplementary layer 4 or directly to the roller body 2. In order to ensure that the outer surface of the roller has the appropriate surface quality, i.e. surface roughness or surface flatness in accordance with the specifications, it is machined after the application of the functional layer 3, i.e. generally turned to the nominal diameter of the roller 1 and ground accordingly. The condition of the roller 1 after application of the functional layer 3 is shown in Figure 2A, and the condition after machining of the surface is illustrated in Figure 2B. It is readily understandable that reworking the surface of the functional layer 3 entails a corresponding amount of effort.

[0074] The method according to the invention and the component according to the invention, in the example described a roller 1, are illustrated in Figures 3 to 5. As already mentioned at the beginning, possible components include, for example, but not exclusively, sliding guides in roller tables, guide rails, rollers or cylinders, for example also backup rollers that interact with other cylinders or other mechanically loaded components subject to wear.

[0075] Figure 3A shows the state of the roller 1 after application of the functional layer 3 made of a wear-resistant and hard and / or tough material, which has more favorable properties in terms of wear properties than the base material of the roller body 2 and / or a supplementary layer 4 arranged therebetween. The supplementary layer 4 can, for example, consist of a relatively soft material based on the austenitic stainless steel 1.4404. The functional layer 3, which was applied by build-up welding in the described embodiment of the invention, consists, for example, of a wear-resistant hot-work steel such as 1.2344 or a high-speed steel such as 1.3344 comprising foreign phases of tungsten carbide and / or titanium carbide, which achieve a corresponding wear resistance of the functional layer 3.

[0076] Immediately after its application to the roller body 2 according to Figure 3A, the functional layer 3 in no way meets the requirements for the surface quality of the finished component. In a next step, which is illustrated in Figure 3B, a sacrificial layer 5 is applied to the functional layer 3, which consists, for example, of the same material as the other supplementary layers or of a different material, since the sacrificial layer may, for example, have lower ductility than the supplementary layers further inside (e.g. buffer layers) or, for example, unlike these, does not have to meet any special requirements with regard to thermal conduction and / or thermal expansion. The sacrificial layer 5 does not meet the application-specific requirements for the wear resistance and / or hardness and / or toughness of the material.

[0077] After application of the sacrificial layer 5, the roller shell has an oversize, which is reduced to the nominal diameter of the roller 1 in a further process step by appropriate post-processing such as milling, grinding or turning and, as illustrated in Figure 3C, ultimately has the desired surface roughness according to the specifications from the application of the roller 1.

[0078] Figure 4 shows a partial section through the roller 1 according to the invention after a certain downtime or operating time. Parts of the sacrificial layer have been worn away due to stress, but parts of it are still present. Parts of the functional layer 3 are also worn away, although the degree of wear in the two layers is generally different. The thickness of the functional layer 3 becomes uniform over time.

[0079] Figure 5 illustrates a multi-layer system for the roller shell, comprising a plurality of functional layers 3 and a plurality of supplementary layers 4 arranged to achieve a radial hardness gradient. A sacrificial layer 5, not shown in Figure 5, is applied above the layer arrangement of functional layers 3. This sacrificial layer 5, as in the example according to Figure 3, is subjected to appropriate post-processing with regard to surface roughness and the nominal diameter of the roller.

[0080] List of reference symbols

[0081] 1 roll

[0082] 2 Roller body 3 Functional layer

[0083] 4 Supplementary layer

[0084] 5 sacrificial layer

Claims

Patent claims 1. A mechanically, in particular tribologically stressed component in a rolling mill, comprising a base body made of a base material and at least one functional layer (3) applied to the base body made of at least one material different from the base material, wherein the material of the at least one functional layer (3) has a higher wear resistance than the base material, wherein the base body comprises at least one further outer layer as a sacrificial layer (5) which at least partially encloses the at least one functional layer (3), and the sacrificial layer (5) consists of a material which has a lower wear resistance than the at least one functional layer (3).

2. Component according to claim 1, characterized in that the at least one functional layer (3) consists of a relatively harder and / or more wear-resistant material than the sacrificial layer (5).

3. Component according to one of claims 1 or 2 as a roller (1) for a rolling mill, in particular for a hot rolling mill.

4. Component according to claim 3, characterized in that the functional layer (3) has a preferably radially extending structural and / or property gradient.

5. Component according to one of claims 1 to 4, characterized by a plurality of functional layers (3) which have different properties and / or consist of different materials.

6. Component according to one of claims 3 to 5, characterized in that the plurality of functional layers (3) form a preferably radial structural and / or property gradient of the roller shell.

7. Component according to one of claims 3 to 6, characterized in that the roller surface is designed as a single-surface surface.

8. A method for producing or restoring a mechanically, in particular tribologically, stressed component according to one of claims 1 to 7, comprising a base body made of a base material and at least one functional layer (3) applied to the base body, which comprises at least one material different from the base material, comprising the following method steps: Providing a base body made of a base material, Applying at least one wear-resistant functional layer to the base body, Applying an outer sacrificial layer (5) to the functional layer (3), wherein the sacrificial layer (5) consists of a material which differs from the material properties of the functional layer (3) in terms of material properties and which has a lower wear resistance than the at least one functional layer (3), Reworking the base body by removing material to a surface that is closed at least in the area of ​​a functional surface and has specified dimensions.

9. Method according to claim 8, characterized by a production or restoration of a roller (1) as a component, comprising reworking of the roller shell with a diameter reduction to a closed roller shell surface with a predetermined outer diameter. Method according to one of claims 8 or 9, characterized in that the application of the at least one functional layer (3) and / or the sacrificial layer (5) is selected from a group of methods comprising build-up welding, thermal spraying, plasma coating, casting, centrifugal casting, vapor deposition, dusting, galvanic coating, chemical coating. Method according to one of claims 8 to 10, characterized in that the reworking is carried out by turning and / or milling and / or grinding. Method according to one of claims 8 to 11, characterized in that the thickness of the at least one functional layer (3) and / or the sacrificial layer (5) is selected such that the sacrificial layer (5) at least partially encloses the at least one functional layer after the material removal.Method according to one of claims 8 to 12, characterized in that the lateral surface is produced as a single-surface lateral surface. Method according to one of claims 8 to 13, characterized in that a plurality of functional layers are applied, which have different properties and / or consist of different materials, such that the plurality of functional layers (3) form a preferably radial structural and / or property gradient.

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