WO2016071299A1 - Roller and method for producing such a roller - Google Patents

Abstract

The invention relates to a roller for a machine for the production and/or further processing of a fibrous web, such as a paper, board, or tissue web, comprising a roller core, at least one adhesion layer applied thereto and composed of a first material, and at least one functional layer applied to the one adhesion layer and composed of a second material, wherein i) the second material of the at least one functional layer was applied by means of a thermal spraying method and the functional layer produced in such a way was then at least partially thermally melted; or ii) the second material of the at least one functional layer was applied by means of laser cladding or an equivalent method.

Description

 ROLLER AND METHOD FOR PRODUCING SUCH A ROLLER

The invention relates to a roller, in particular for use in a machine for producing and / or finishing a fibrous web such as a paper, board or tissue web and a method for producing such according to independent claims.

Such rollers are available in a variety of positions and with a variety of functions in the above-mentioned machines. Thus, rolls with soft cover layers are suitable for pressing and dewatering the fibrous web. Rollers with hard surfaces, in particular also with a heating device, are mainly used for smoothing and drying. Depending on the application, these rollers are on the one hand subject to considerable corrosion due to the environment to which they are exposed. In addition to water, these come directly or indirectly in contact with the fibrous web and the additives contained therein, such as chemicals. Depending on the installation position and intended use in the machine, the ambient temperatures to which the roller is exposed vary. On the other hand, such rollers must also have an extremely high abrasion resistance, depending on the intended use, since the fibrous web or such fibrous web carrying conveyors run indirectly or directly on its outer circumference.

Recently, new processes for coating roll cores made of steel or composite materials, which form a metallic, ceramic or cermet sprayed layer by means of processes such as HVOF or flame spraying on the roll core. Such rolls have been known for some time and form the current state of the art, for example in central press rolls, drying cylinders and guide rolls. The process of thermal coating provides that, for the production of the corresponding layer, a material may be added as an injection additive, for example as a powder, wire or in another suitable form by means of introduction of thermal energy. or completely melted and kinetically accelerated onto the roll core to be coated. The impacting material cools, solidifies and forms a mechanical and positive connection with the roll core. The properties and possibilities of the injection processes are essentially determined by the ratio of the kinetic to the thermal energy.

The known methods and the metallic, ceramic or cermet coatings which can be produced thereby have the disadvantage that the coating structure is closed-porous to open-porous, depending on the material and / or the manufacturing process. The porosity can lead to increased susceptibility to corrosion due to penetration of by-products and to adhesion problems. Accordingly, the surface of the sprayed layer must be filled, for example by final sealing with an additional material such as a polymer. The disadvantage of this is that these seals are not sufficiently resistant to abrasion and it comes to leaching during operation, in which the polymer is released from the pores. This in turn increases the risk of corrosion and adhesion of the entire coating.

Furthermore, thermal spraying is not an economical or ecological method because of the poor powder application efficiency with regard to the layer thickness that can be achieved per coating course (μιτι per stroke) and the percentage of powder remaining on the roller.

DE 101 30 313 A1 discloses an initially thermally sprayed and subsequently thermally remelted ceramic coating of a dewatering strip for a paper or board machine. As a rule, such a drainage strip has such a short service life as a wear component that the influence of corrosion is marginal. The requirements on the adhesion and abrasion resistance of the coating are low. For this reason, the thermally remelted ceramic coating is applied directly to the base material without an intermediate adhesive layer. DE 20 2012 012 592 U1 describes a roller for a paper machine, comprising a roller core, with an adhesive layer and an oxide ceramic layer applied thereto. The latter was coated by means of a thermal spraying method in which molten material impinges on the comparatively cold roll core and is mechanically clamped to its surface. To set a predetermined surface structure on the outer circumference of the thermally sprayed coating, this is first machined and then textured by laser radiation. By spotwise evaporation of the outer peripheral surface of the coating material of the oxide ceramic is removed. At least between the textured portions of the coating, the oxide ceramic remains porous. To prevent media from entering these cavities, the entire surface of the rollers must then be sealed by means of a polymer.

It is accordingly an object of the invention to provide a roller and a method for producing such, whose coating satisfies the requirements of its adhesion to the roll core, their corrosion and abrasion resistance, by paper, board or tissue machines in terms of temperature, humidity and load be made by chemicals.

The object is achieved by a roller and a method for producing such with the features of the independent claims. The term functional layer in the context of the present invention means a layer which comes into direct contact with the fibrous web or indirectly, for example via a conveyor belt lying between the fibrous web and functional layer, such as coverings or sieves revolving around them. The functional layer thus has properties that particularly reduce corrosion and abrasion to the highest degree. For the purposes of the present invention, an adhesive layer is understood as meaning a layer which serves for the bonding between the roll core and a functional layer on the one hand. A particularly good connection of the functional layer to the roll core takes place when the adhesive layer is ductile compared to the functional layer. Such a high ductility can be achieved by including or producing the adhesion layer from a nickel-aluminum alloy. Good ductility could be achieved with a blend ratio of 95% nickel and 5% aluminum, each in terms of the weight of the blend. Thus, both the adhesive layer and the functional layer are part of the solid coating already applied to the roll, which is successively applied to the roll core during manufacture. Functional and / or adhesive layer can be constructed from a plurality of individual layers. For the purposes of the present invention, the term "material" basically means the starting material from which the adhesive or functional layer is to be produced. In the case of thermal coating, in particular in the form of thermal spraying, this means the spray additive material, that is, the starting material which dissipates, melts or melts inside or outside a spray burner and accelerates in a gas flow in the form of spray particles to reach the surface of the underlying one Substrate to be thrown. In the case of Lasercladdings material is understood to mean that material which is applied to the substrate to be coated for the purpose of producing the corresponding layer.

Basically, in the context of the invention, the substrate is understood to mean, after the stage of the coating produced, the radially outermost material to be directly coated, such as the roll core, the adhesive layer, the functional layer or where this makes sense, a combination thereof. The term alloying region is understood to mean a metallic bond between them, as a result of the melting (with subsequent cooling) of at least two materials, with the formation of a crystalline lattice. For example, the materials of the adhesive layer and the roll core may be selected so as to form such an alloying region when they are formed together in the manufacture of the roll or in the production of the coating of the roll due to reflow by heat supply after solidification. Furthermore, the materials of the adhesion layer and the functional layer may be selected such that they do not form such an alloy region with one another.

According to the present invention, the term laser cladding or a method immediately following this is understood to mean a coating method by means of which it is possible to melt the surface to be coated-in other words, the substrate-itself or completely. Such a high heat input is not possible in the known thermal spray processes, such as flame, high-speed flame, arc or plasma spraying, which leads to the on or melting of the substrate. A melting or melting in Lasercladding can be done for example by supplying thermal energy to the substrate to be coated and can be preferably realized by radiation, such as laser radiation. Thus, the material of the adhesive or functional layer is generally introduced into laser beam path in the beam path of the laser, melted and applied to the substrate. At the same time the laser beam melts the surface of the substrate with respect to the radial thickness at least partially on or completely over its thickness in the radial direction, as far as such a complete melting makes sense.

Both by means of laser cladding and by means of the conventional spraying process, the coating of several individual layers is successively produced. Such a successive production is always necessary if the area over which the heat input takes place is significantly smaller than the total area to be coated the roller. This is the case in the generic rolls, when used for example in a paper machine.

Thermal melting in the context of the invention is a subsequent, preferably in the thickness direction partially, transient transfer of the corresponding present in solid state substrate, especially the last example by thermal spraying already prepared, radially outermost layer of the roller, in a liquid phase, in particular due to heat Understood. Partial melting means that the entire surface of the substrate is melted, even successively, but not over the entire layer thickness of the coating in the radial direction of the roll, but only near the surface. In contrast, complete melting would mean complete melting or melting of the substrate. In the former case, therefore, said functional layer can be melted across the surface over a fraction of its layer thickness. In the second case, the melting takes place over the entire layer thickness, preferably until just before the transition to the underlying adhesive layer - without, however, melting the adhesive layer itself. Nevertheless, such a melting of the adhesive layer and the overlying functional layer would be conceivable.

The thermal melting consequently serves for the subsequent melting of the substrate, such as the layer produced last, and preferably takes place over the entire surface of the roll to be coated, to be coated. The subsequent, temporary melting has the advantage, especially in the case of porous structures, that the pores are dissolved by the brief transfer of the substrate into the melt. Thus, after cooling the molten substrate in this area, a reduction in the porosity of the substrate can be achieved. As a result, if the melting occurs nationwide, can be dispensed with a conventional sealing of the finished coated roll by means of polymers. In other words, the melted serves and solidified layer of the substrate itself as a seal. Thus, by way of example, the radially outermost layer of the coating, such as the functional layer, can be subsequently melted. It is also conceivable to seal at least one single functional layer between the adhesive layer on the roll core and the radially outermost surface of the finished coated roll in this way. In other words, this means that not necessarily the radially outermost functional layer of the finished coating must be melted subsequently.

The term density of a layer basically means the mass density, measured at ambient temperature, of the layer produced by means of the thermal coating method and cooled to ambient temperature. In the case of porous layers, the bulk density is accordingly to be understood, which results from the quotient of the mass of the layer and the total volume, consisting of the volume of the solid and the volume of the pores.

If, for the purposes of the present invention, porosity of a layer is mentioned, then the ratio of void volume to total volume of the layer at ambient temperature is always meant. Further advantageous embodiments of the invention will become apparent from the dependent claims.

The invention will be described in more detail below with reference to the drawings without limiting the generality. In the figures show:

Fig. 1 is a highly schematic representation of two inventively coated rolls; a highly schematic representation of the order coating according to the invention; in each case an embodiment in a highly schematic sectional view through a coating according to the invention comprising at least one thermal spray coating.

1 schematically shows two rolls 1 produced according to the invention for producing and / or further processing a fibrous web, such as a paper, board or tissue web, as indicated between the two. Basically, you do not always have to roll both shown rollers towards each other. Both rolls 1 are parts of a paper, board or tissue machine, not shown. The rollers 1 can also be used in various positions in a machine for producing or processing a fibrous web, such as a paper, board or tissue web, with which they come into direct or indirect contact. In the position of a central press roll in the press section of a paper machine technically highest demands are placed on the roll 1 and its coating. This is especially true of sheet dispensing properties, wear resistance at high line loads in press nips, and corrosion resistance in wet environments. FIG. 2 shows, in a highly schematic view, the basic structure of a single layer, such as a functional layer of the coating 5 according to the invention, on a roll 1.

The roller 1 is rotatably mounted about its longitudinal axis and is suitably driven, so that it rotates away under a preferably parallel to the longitudinal axis along the roller 1 relative to this back and forth movable applicator 7. As a result, the entire surface of the roller 1 can be coated successively, for example in a continuous spiral line. However, it is also possible to apply the coating 5 in a different manner, for. B. in radial rings or axial stripes. The thermal coating device 6 for producing the roll according to the invention in the present case comprises a Applicator 7, an optional on and off material supply 8, an energy source 9, in which the usually powdery material is entered and a protective gas, not shown, for supplying inert gas to the roller. The coating device 6 can be designed such that it can carry out both the thermal spraying and the laser dadding. The application of inert gas is presently indicated by the cone, which adjoins the power source 9. The protective gas can serve to entrain and / or accelerate the material, such as spray additive material, which is introduced into the beam path of the energy source 9 for melting. In the conventional thermal spraying accelerated by inert gas, off, on or molten spray additive is thrown onto the roller to be coated 1, here, for example, the bare roll core. If the surface of the underlying substrate is also melted, as is the case with laser dandding, then the melted material supplied to the substrate also enters the substrate melt. Otherwise, only a clawing of the impinging at least partially molten spray additive material takes place on the surface of the roller 1 to be coated, as is fundamentally the case in conventional thermal spraying. As energy source 9 are therefore basically inductive and plasma-generating devices, devices that emit electron beams or lasers of various types such as CO ₂ laser, HDPL (High Power Diode Laser) or DDL (Direct Diode Laser) or combinations possible. In principle, the thermal coating device can be designed so that both thermal spraying with and without at least partial melting of the underlying substrate is possible. This can be achieved, for example, by means of which the thermal energy can be correspondingly adjusted.

FIGS. 3 to 5 each show, in a highly schematic sectional view, an embodiment of the present invention in a partial cross section perpendicular to the longitudinal axis through the roller 1. To simplify the Illustration, the roll curvature has been disregarded. It should also be noted that the thickness seen in the radial direction of the individual layers of the roller 1 is not shown to scale. It is only the sequence of layers to be symbolized. The roller 1 shown in each case usually has a radially inner roller core 2, which may be at least partially made of a metal such as steel or, more recently, of a plastic, in particular a fiber-reinforced plastic.

In the present case, as shown in each of FIGS. 3 to 5, a coating 5, comprising at least one adhesive layer 3 and at least one functional layer 4, is applied directly on the roll core 2 in the radial direction on its circumference. Adhesive layer 3 serves for bonding between the roller core 2 and the next outward radial direction. Since the adhesive layer 3 can be formed according to the prior art and thus known, a detailed description can be omitted.

On the at least one adhesive layer 3, according to the invention, a first functional layer 4, which is formed here from technical ceramics such as oxide ceramics, is applied. The entire coating 5 produced in each case according to the illustrated embodiments can be produced by means of the thermal coating device of FIG. 2.

According to the embodiment of FIG. 3, the functional layer 4 has been applied from a single single layer to the previously produced adhesive layer 3 by means of laser cladding. In this case, the adhesive layer 3 was at least partially melted by the heat input of the laser into the adhesive layer 3. Roll core 2 and adhesive layer 3 may form an alloy region (not shown) due to appropriate choice of their materials and their melting at the transition roller core adhesive layer. The laser cladding results in a high-density functional layer 4, which has a low porosity, in particular over its entire thickness extent. Alternatively or additionally, it would also be conceivable that the adhesive layer 3 or functional layer 4 could be made up of a plurality of individual layers. Other, meaningful sequences of the adhesive and functional layer would be conceivable in principle. The functional layer 4 produced by means of laser cladding has a low porosity in comparison to conventional coatings, for example produced by means of plasma spraying. The embodiment of FIG. 4 shows a development of the object of FIG. 3. The present radially outermost, produced by laser cladding functional layer 4 is not applied directly to the adhesive layer 3. Instead, this is applied to a thermally sprayed, functioning as an intermediate layer further functional layer 4. The latter itself is directly on the adhesive layer 3 - but without substantially melting them - for example, conventionally produced by thermal spraying. The functional layer 4 produced by means of thermal spraying has a higher porosity compared to the laser-injected functional layer 4. In other words, in this case the radially outermost functional layer 4 has a greater density than the functional layer 4 located directly underneath in the radial direction. This additional radially inner functional layer 4 thermally sprayed onto the adhesion layer 3 by means of plasma serves as an intermediate layer to the radially outer layer produced by means of laser cladding (and here even radially outermost) functional layer 4. It is permeable to penetrating media such as fluids. At the same time, the less porous, radially outermost functional layer 4 serves as corrosion protection. With regard to the possible layer structure, what has been said about FIG. 3 applies.

Figures 5a and 5b show another embodiment of the present invention. In contrast to FIG. 4, the functional layer 4 is composed of a plurality of individual layers, which are not shown here in detail. Each single layer is formed, as shown in Fig. 2, by material, for example applied layer by layer on the roll core 2 by plasma spraying without substantially melting the underlying substrate. Such a functional layer composed of several individual layers is shown in FIG. 5a.

As shown in FIG. 5b, the finished functional layer 4, which, as shown in FIG. 5a, can be constructed from a plurality of functional individual layers, is subsequently remelted at least partially in the thickness direction (radial direction) by supplying thermal energy. Such melting can be effected by means of the thermal coating device 6 shown in FIG. 2, for example by the action of laser radiation. In this case, it is dispensed with the addition of a spray additive material by the material supply of the coating device 6 is turned off. Melting and re-cooling removes most of the pores achieved by plasma spraying. Thus, in the present case, the radially outermost surface of the roller 1 or of the coating 5, that is to say the radially outermost functional layer 4, is thermally closed against the entry or passage of media. Thus, the radially outermost functional layer 4 or the individual layer forming it has a higher density than the underlying, thermally sprayed functional layer 4 or the corresponding individual layer. Such sealing can take place close to the surface, so that the sealed layer thickness in the radial direction makes up a fraction of the total layer thickness of the coating 5 or of the entire functional layer 4. Regardless of the illustrated embodiments, at least one functional layer (or individual layer) may also be provided between the roller core 2 and the radially outermost functional layer 4, which has a greater density than a single functional layer 4 located radially below be made of several individual layers and by means of thermal spraying or laser cladding. Also the Single layers of functional layer and / or adhesive layer can consist of different chemical compositions.

List of rollers

Roll core

adhesive layer

functional layer

coating

Thermal Beschichtungsvornchtung

applicator

Material supply

energy

Claims

claims Roller for a machine for producing and / or further processing a fibrous web, such as a paper, board or tissue web, comprising a roll core (2), at least one adhesive layer (3) of a first material applied thereto and at least one, at least one Adhesive layer (3) applied functional layer (4) of a second material, wherein i) the second material of the at least one functional layer (4) applied by means of a thermal spraying process and the functional layer (4) thus produced was then at least partially thermally melted; or ii) the second material of the at least one functional layer (4) has been applied by means of laser cladding or an equivalent method. Roller according to claim 1, characterized in that when the functional layer (4) according to alternative i) is produced, it can be achieved by means of a thermal spraying method in which the at least immediately underlying layer, such as adhesion layer (3) and / or functional layer (4) in FIG Was not melted, such as flame, high-speed flame, arc, or plasma spraying. Roller according to claim 1 or 2, characterized in that when performing the functional layer (4) according to alternative ii) the at least immediately underlying layer, such as adhesive layer (3) and / or functional layer (4) has been at least partially melted. Roller for a machine for producing and / or further processing a fibrous web, such as a paper, board or tissue web, comprising a roll core (2), at least one adhesive layer (3) of a first material applied thereto and at least one, at least one Adhesive layer (3) applied functional layer (4) of a second material, wherein the at least one functional layer (4) comprises a first, preferably radially inner region and a second, preferably radially outer region, wherein the Functional layer (4) is designed such that it has a higher density in the second region than in the first region. 5. Roller according to claim 4, characterized in that the second region is the radially outermost region of the roller. 6. Roller according to one of the preceding claims, characterized in that the functional layer (4) and / or the adhesive layer (3) is constructed of a plurality of superposed individual layers / are. 7. Roller according to one of the preceding claims and preferably according to claim 6, characterized in that the functional layer (4), the adhesive layer (3) and / or the corresponding single layer has been applied by means of a thermal spraying process, in which the adhesive layer (3 ) and / or the underlying layer is substantially not melted, such as flame, high velocity flame, arc or plasma spraying. 8. Roller according to one of the preceding claims and preferably according to claim 6 or 7, characterized in that the functional layer (4), the adhesive layer (3) and / or the corresponding single layer by means of Lasercladding, wherein the adhesive layer (3) and / or the immediately underlying layer is at least partially melted, has been / were. 9. Roller according to one of the preceding claims, characterized in that the materials of the individual functional layers (4) with each other and / or the adhesive layers (3) differ from each other. 10. Roller according to one of claims 6 to 9, characterized in that the materials of the individual individual layers of the functional layer (4) and / or the adhesive layer (3) differ from each other. 1 1. Roller according to one of the preceding claims, characterized in that the second material is at least partially a technical ceramics, such as oxide ceramics. 12. Roller according to claim 1 1, characterized in that the oxide ceramic contains metal oxides which are selected from chromium oxide (Cr ₂ O 3), titanium oxide (ΤΊΟ 2), Alumina (Al2O3), zirconia (ZrO2), silica (S1O2), yttria (Y2O3) or mixtures thereof. 13. Roller according to one of the preceding claims, characterized in that the first material is at least partially a metal. 14. Roller according to claim 13, characterized in that the first material comprises a nickel-aluminum alloy, preferably with a mixing ratio of 95% nickel and 5% aluminum. 15. Roller according to one of the preceding claims, characterized in that the material of the roller core (2) is at least partially a metal and the roller core (2) is preferably at least partially made of steel. 16. Roller according to one of the preceding claims, characterized in that the material of the roller core (2) and the first material are selected such that these in the region of the transition from roller core (2) to the adhesive layer (3) together an alloy region, in which a metallurgical connection of the two materials is present, form. 17. A method for producing a roll for a machine for producing and / or further processing a fibrous web, such as a paper, board or tissue web, wherein the roller (1) comprises a roller core (2), at least one adhesive layer (3) applied thereon a first material and at least one functional layer (4) made of a second material applied to at least one adhesive layer (3), the method comprising the following steps: a) producing the at least one adhesive layer (3) by applying the first material on the roll core (2) or on an already formed layer such as functional layer (4) or adhesive layer (3); b) producing the at least one or a further functional layer (4) by applying the second material to the adhesive layer (3) produced; c) supplying heat in the region of the transition from the one adhesive layer (3) to the one functional layer (4), so that at least one of the materials, preferably both, are at least partially melted. 18. The method according to claim 17, characterized in that the Functional layer (4) in step c) by means of laser cladding or an equivalent method in which the adhesive layer (3) is at least partially melted, is achieved. 19. A method for producing a roll for a machine for producing and / or further processing a fibrous web, such as a paper, board or tissue web, wherein the roller (1) comprises a roller core (2), at least one adhesive layer (3) applied thereon a first material and at least one functional layer (4) made of a second material applied to at least one adhesive layer (3), the method comprising the following steps: a) producing the at least one adhesive layer (3) by applying the first material the roll core (2) or on an already formed layer such as functional layer (4) or adhesive layer (3); b) producing the at least one or a further functional layer (4) by applying the second material to the adhesive layer (3) produced; c) supplying heat to the produced functional layer (4) so that it is thermally melted at least in the region of its side facing away from the adhesive layer (3). 20. The method according to claim 19, characterized in that the Functional layer (4) in step b) by means of a thermal spraying method in which the adhesive layer (3) is substantially not melted, such as flame, high-speed flame, arc, or plasma spraying is achieved. 21. A method according to claim 19 or 20, characterized in that the supply of heat in step c) by a suitable heat source such as by heat radiation, heat conduction, convection, induction, laser radiation, electron beam, arc, plasma gas or combinations thereof. 22. The method according to any one of claims 17 to 21, characterized in that the functional layer (4) and / or the adhesive layer of a plurality of individual layers is / are constructed.