WO2022128510A1

WO2022128510A1 - Method for producing assemblies and use of a separating means

Info

Publication number: WO2022128510A1
Application number: PCT/EP2021/083988
Authority: WO
Inventors: Wilfried Behr; Dirk Federmann; Holger Janssen; Walter Zwaygardt; Sebastian HOLTWERTH; Martin Müller; Markus Stähler
Original assignee: Forschungszentrum Jülich GmbH
Priority date: 2020-12-15
Filing date: 2021-12-02
Publication date: 2022-06-23
Also published as: EP4263109A1; DE102020215873A1

Abstract

The invention relates to a method for producing at least one assembly by welding, in particular by diffusion welding, and to the use of a separating means. In a method for producing at least one assembly (12) by welding, at least two components (10) are joined together by application of a force (F) acting along an axis (20). Adjacent objects (15) which are arranged along the axis (20) and which are not to be joined together are kept separate from one another using a separating means (30). The separating means (30) comprises fibers or graphene. A separating means of this kind does not penetrate into the surface, does not impair the quality of the surface, and, after the joining operation, can be removed from the surface easily and without leaving any residue.

Description

Process for manufacturing assemblies and use of a release agent

description

The invention relates to a method for producing at least one assembly by welding, in particular by diffusion welding, and the use of a separating agent.

In a method for producing an assembly by welding, in particular by diffusion welding, the assembly is produced by joining at least two components while applying a force. Components that are not intended to be joined are physically separated from one another with a release agent.

Solid separating plates, e.g. B. ceramic materials can be used. Separating plates are placed between the components that are not to be connected before the components are connected. Ceramic materials can be used as separator plates or as a coating. It can e.g. B. ceramic coated sheets or press surfaces can be used. Ceramic materials can also be used directly for coating the surfaces of the components that are not to be connected. For example, alumina or boron nitride can be used. These substances can be suspended as a powder in water, for example, in order to then apply them to the surfaces that are not to be joined. This can be done, for example, with a brush, a roller or by spraying.

The methods mentioned have some disadvantages. First of all, a smooth, flat application of the release agent is hardly possible. This creates structures on the surfaces that cause imprints or deformations and/or burn in when they come into contact with neighboring component surfaces. In the case of surfaces in particular, which have to meet certain requirements with regard to their surface quality, it is difficult to maintain such a required quality. For example, sealing surfaces have very low tolerances with regard to their roughness or evenness. Baking causes problems in the subsequent separation of the release agent from the joined component. If the release agent is firmly attached to the component, it has to be removed in a complex mechanical post-processing. In addition, particles of the release agent can get into openings in the components. For example, a component has a porous surface through which a defined material flow is to be generated during later use. There can also be open structures such as grids, nets, channels and cavities of all kinds into which particles can get. These cannot be removed or can only be removed with difficulty and can impair the function of the manufactured assembly. With porous surfaces, scorching and warping can create additional problems.

It is therefore the object of the invention to provide a further developed method for producing a plurality of assemblies and a corresponding use.

The object is achieved by the method for producing at least one assembly according to claim 1 and by using a separating agent according to the independent claim. Refinements are specified in the dependent claims.

A method for producing at least one assembly by welding, in particular by diffusion welding, is used to solve the task. At least two components are joined together by applying a force acting along an axis. Adjacent items along the axis that are not intended to be joined together are separated from each other with a separating agent. The release agent includes fibers or graphene.

It has been shown that a release agent comprising fibers has a number of advantages. On the one hand, such a release agent does not burn into the surface. It therefore does not affect the quality of the surface. Furthermore, after joining, such release agents can be detached from the surface in a particularly simple manner and without leaving any residue. In this way the components can be easily removed from each other and from the press plates and the release agent can be easily removed from the corresponding surfaces. The fibers allow the release agent to hold together particularly well, so that no residues remain. Due to the good cohesion, no particles get into cavities or porous structures of the components or the assemblies to be manufactured, so that the risk of contamination is significantly reduced. The release agent comprises at least one fiber and in particular a multiplicity of fibers. At least one assembly is produced from at least two components. An assembly comprises the at least two objects connected to one another. In particular, the components are joined by the force. In particular, the components for the production of the assembly are positioned between two pressing elements and are subjected to the force by means of these, so that the force acts between the contact surfaces of the components to be joined. In particular, pressing plates are used as pressing elements, which have a certain rigidity and in this way generate a very uniform force distributed over their surface. At least one of the press plates is pressed along the axis in the direction of the other press plate by a mechanical press, which can comprise, for example, a plurality of movable stamps. Both press plates are used to exert force on the components to be joined. The movement can in particular take place automatically via force and/or displacement control.

The axis is an imaginary axis that runs along the effective direction of the force. The components to be joined are located between the press plates so that the axis runs through the components. The axis can be aligned horizontally or, preferably, vertically. In other words, the components to be joined are stacked or arranged one above the other or next to one another. Several component stacks can be arranged next to each other between two press plates in order to produce several assemblies in parallel. In this case, several axes run between the two press plates through all the components of the assemblies to be joined.

The contact surfaces of the components to be joined, on which the components make contact, run at an angle, in particular perpendicularly, to the axis. The axis runs through the contact surfaces. Adjacent contact surfaces of components to be joined run in particular parallel to one another. If more than two components are joined to form an assembly, the more than two components are arranged adjacent to each other along the axis. The axis runs through all components to be joined together. The components are thus arranged on the axis. The separating means is also arranged on the axle; the axis thus runs through the release agent.

The objects that are not intended to be joined to one another are in particular a component and a press plate and/or two adjacent components that are different assemblies. In the first case, the separating means can be fixedly arranged on one or both press plates, so that the surface of the component adjacent to the press plate facing the press plate is physically separated from the press plate.

Adjacent objects that are not intended to be joined together are physically separated from one another by means of the separating means. The separating agent thus prevents direct contact between the adjacent components. In particular, the separating means is arranged areally between the adjacent components, so that physical contact between the components is prevented. In this way, undesired welding of these adjacent components is prevented. In particular, the separating agent is arranged between the adjacent components that are not to be joined before the start of the welding process.

Joining is done by welding. Accordingly, the components are permanently connected to one another using heat and/or pressure. A material connection is created. The parting agent according to the invention can be used in any welding process in which components are produced by joining with the application of a force acting along an axis. The separating agent can be used particularly advantageously in diffusion welding, since the high temperatures in the area of objects that are not to be joined together place particularly high demands on a separating agent.

Fibers are linear structures that consist of a fibrous material and have an external fibrous shape. The fibers are thin in relation to their length. They have a length to diameter ratio of >5:1, in particular >10:1. The fibers can appear in a composite. Basically, the material of the fibers is of secondary importance. Carbon nanotubes are also fibers within the meaning of the invention. Carbon nanotubes can also be arranged around other fibers.

In one embodiment, the fibers have a diameter that is greater than 1 μm, in particular greater than 5 μm, preferably greater than 10 μm and/or less than 50 μm, in particular less than 30 μm, preferably less than 20 μm. In particular, the release agent comprises fibers in a volume and/or mass fraction of more than 10%, preferably more than 25% and in one embodiment more than 50%. Graphene offers the same advantages due to its mechanical properties. Graphene is used in particular as a monolayer or thin layer. In one embodiment, a release agent containing or consisting of graphene is coated on both sides of a release plate. The separating plate together with the separating means can be arranged between the objects that are not to be joined together.

In one embodiment, a number of assemblies are produced from at least two components each. The separator is positioned between adjacent components positioned along the axis.

Thus, multiple assemblies are manufactured in such a way that they are jointly subjected to the force acting along the axis. Several groups of components, each of which is to be joined to form an assembly, are arranged on the axis. They are exposed to the force together. In other words, multiple assemblies are manufactured in series. In this way, a large number of assemblies can be manufactured efficiently and quickly, for example in one furnace run. In particular, the assemblies are manufactured in a batch operation, which includes, for example, vacuuming and/or heating and therefore requires a certain lead time. A significant increase in efficiency can be achieved through the simultaneous manufacture of a large number of assemblies in one kiln run. High throughputs can be achieved in particular with flat components and/or assemblies. . The production of the several assemblies takes place in particular at the same time and/or in one work step.

In this embodiment, adjacent objects that are not intended to be joined to one another are two adjacent components which are arranged along the axis and belong to different assemblies. In this configuration too, the contact surfaces of the components to be joined typically run at an angle, in particular perpendicularly, to the axis. The separating agent is also arranged on the axis, so it cuts it. In particular, the separating means runs perpendicular to the axis.

The adjacent components, which are separated by the separating agent, belong to different assemblies. Neighboring components that are not to be joined are physically separated from one another by the separating agent. The separating agent thus prevents direct contact between the adjacent components. on this prevents undesired joining of these adjacent components. In particular, the separating agent is arranged between the adjacent components that are not to be joined before the start of the welding process. This prevents unwanted welding of these components during the welding process. In particular, during the production of assemblies according to the invention, an increased temperature prevails at least in the contact area of components to be joined together.

In one embodiment, the assembly groups are joined in an atmosphere with an elevated temperature. In particular, the temperature of the atmosphere is between 500°C and 1000°C. The atmosphere means the environment of the components or assemblies. It can be a gas atmosphere in which a gas or gas mixture with the elevated temperature is present. For example, it can be an atmosphere of at least one inert gas, for example argon and/or nitrogen. It can be a vacuum atmosphere.

In one embodiment, the temperature of the atmosphere is greater than 400°C, in particular greater than 600°C and preferably greater than 700°C. In one embodiment, the temperature is less than 1200°C, in particular less than 950°C and preferably less than 850°C. In another embodiment, in particular for joining titanium components, the temperature of the atmosphere is between 800°C and 1200°C.

In particular, the temperature is lower than the melting point of the material or materials of the components. In one embodiment, the temperature is greater than 40%, in particular greater than 50%, preferably greater than 60% of the melting point of the material of the components. In one embodiment, the temperature is less than 95%, in particular less than 90%, typically less than 80% of the melting point of the material of the components. This enables a firm connection with minimal deformation of the components at the same time.

In particular, the assemblies are manufactured in an oven. This can generate the atmosphere with increased temperature. The components to be joined, the release agent and the press plates are arranged in the oven. The increased temperature facilitates and accelerates the joining. With diffusion welding, the joining takes place at high pressure and high temperature in a vacuum or under a inert gas atmosphere. Very high joint qualities are achieved since the properties of the assembly in and around the welding area are at least approximately the same as the properties of the component material before welding.

In one embodiment, the components are exposed to a vacuum at least for certain periods of time. A vacuum means a pressure reduced by at least 90%, in particular by at least 99%, compared to atmospheric pressure. In particular, the production of the at least one subassembly takes place in the vacuum, at least for certain periods of time. The pressure can be below 10' ⁴ mbar.

The vacuum prevents contamination and thus enables particularly clean connections with high quality. The diffusion of the particles is also improved. Furthermore, the oxygen partial pressure is reduced, so that oxidizable objects such as components or release agents do not oxidize. In this way, a high quality of the manufactured components and an effective function of the release agent are guaranteed. In an alternative or supplementary embodiment, the components are exposed to an inert gas atmosphere at least for some periods of time.

In one embodiment, the method is carried out in a vacuum oven. This can generate an increased temperature and a vacuum, so that the components can be joined particularly efficiently.

In a further embodiment, the release agent is a flat solid. A flat solid is a solid whose extent in the first direction is many times smaller than the extents in the second and third directions. All three directions are perpendicular to each other. The expansion in the first direction is, for example, more than 0.001%, in particular more than 0.01% and/or, for example, less than 10%, in particular less than 1%, of the expansion in the second and third direction.

Flat solids are particularly easy to handle and position between the respective objects. In particular, the flat solid is aligned perpendicular to the axis. In one embodiment, the planar solid has a flexibility that bends through an angle of 90° on a Distance of 20 cm, in particular 10 cm and preferably 5 cm allows. Such a flexible release agent can be detached from the objects in a particularly simple manner.

In particular, the extent of the fibers along the surface of the flat solid is greater than the extent of the fibers perpendicular to the surface of the flat solid. In particular, this applies when averaged over all fibers. The extent along the surface may exceed the extent perpendicular to the surface by a factor of at least 5. In one embodiment, the fibers are at least substantially aligned along the face.

In one embodiment, the components from which an assembly is made are made of the same material. In one embodiment, all components are made from the same material.

In one configuration, the release agent includes carbon fibers. Carbon fibers, also referred to as carbon filaments, have proven to be particularly easy to remove from the components, even after the application of large forces. They are readily available and easy to use. In addition, carbon fibers have the advantage that they cause very little burn-in or imprints in the components. In particular, assemblies with surfaces that must have certain properties in order to fulfill a specific function, for example sealing surfaces with low tolerances in terms of surface roughness, can be produced in particularly high quality in this way.

Carbon fibers are also particularly temperature-resistant. This assumes that the oxygen partial pressure is sufficiently low that the carbon does not oxidize or burn. In one embodiment of the method, the oxygen partial pressure is so low that carbon fibers do not oxidize or only oxidize to a negligible extent.

In one configuration, the separating agent also contains an agent which reduces the adhesion of the separating agent to the surface of the object. Alternatively or additionally, the release agent is subjected to a surface treatment in order to reduce the adhesion of the release agent to the surface of the object.

In other words, the adhesive properties of the separating agent are changed in such a way that adhesion to the surface of the objects to be separated is reduced even further becomes. The release agent can be coated with an agent. In one embodiment, such an agent, in particular PTFE, is applied to the material containing fibers as a spray. Graphene can also be used to further reduce adhesive properties. For this purpose, graphene can be applied to a material containing fibers, for example. In one embodiment, the surface properties of the release agent are changed by a thermal, chemical and/or mechanical process. The suitable selection is made in particular taking into account the environmental conditions.

In another embodiment, the release agent also contains an agent that changes the porosity or surface structure of the release agent. Alternatively or additionally, the release agent is subjected to processing that achieves this effect. In this way, the adhesive properties and/or the surface structure of the assemblies can be changed or specifically adjusted after the joining process.

In a further embodiment, a fleece, paper or fabric containing the fibers is used as the release agent. Fleeces, papers and fabrics containing fibers are readily available and technically easy to use. In addition, such materials have the advantage of a firm cohesion. This means that only a few release agent particles and release agent particles, such as fibers, can be easily detached from the surfaces.

The fleece is, in particular, a flat solid body that contains disordered fibers that extend three-dimensionally in space. The extent of the fibers along the direction of expansion of the fleece is in particular greater than the extent transverse to the direction of expansion.

A paper can contain a binder that crosslinks the fibers together. The fibers of a paper can essentially extend in a straight line and/or in one plane. You can cross. A woven fabric may contain fibers arranged as warp and weft threads. These are arranged to cross each other. In particular, the fibers are each arranged in bundles. In one embodiment, the fibers are oriented. This can be particularly the case with paper and tissue. In this case, the fibers essentially extend along the plane of the paper or fabric. Due to the flexibility and the cavities that may be located between the fibers, the fabrics containing the fibers mentioned can be handled particularly easily. In one embodiment, a carbon fiber fleece, carbon fiber paper or carbon fiber fabric is used. In one embodiment, the release agent is used in the form of a mat. The mat can include fabric, mesh and/or scrims such as multiaxial scrims made of carbon fibers.

In one configuration, the components are metallic components. In particular, the components are made of titanium. Metallic components can be welded to one another particularly well using the method according to the invention. Due to its mechanical properties and its strength, electrical conductivity and corrosion resistance, titanium is particularly suitable for certain applications such as monopolar plates and bipolar plates, for example for electrolysis. Alternatively, corrosion-resistant steel can also be used.

In one configuration, the at least one assembly is a bipolar plate or a monopolar plate, for example an anode-side monopolar plate or a cathode-side monopolar plate, for forming an electrolysis or fuel cell stack. Bipolar plates or bipolar plate arrangements fulfill a sealing function on the outside, which is necessary for the functioning of the electrolyzer or the fuel cell. The demands on the surfaces are therefore particularly high here. The required accuracies can only be met with difficulty using conventional methods, so that the use of the release agent according to the invention offers particular advantages in assemblies of this type. In addition, cavities or porous structures are present inside a bipolar plate, which enable transport processes in the electrolysis or fuel cell stack. Due to the release agent containing fibers, there is no longer any risk of contamination. The bipolar plate can also be referred to as a bipolar plate assembly.

For example, a separating device, two flow distributor units and frame elements can be used as components for the production of bipolar plates. A one-piece bipolar plate arrangement for forming an electrolysis or fuel cell stack results as the manufactured component arrangement. In particular, the bipolar plate includes a structure that the catalyst-coated membrane connects, with the structure serving for the fluidic supply and discharge as well as the coarse and fine distribution of the reaction educts and products. Alternatively, the assembly can also be a separator plate for a battery.

In one embodiment, the bipolar plate includes the following components, which are joined together:

- a metallic separator which is designed to produce a fluid-tight seal between an anode side and a cathode side and which is provided with fluid supply channels and fluid discharge channels on both the anode and cathode sides,

- Two metallic flow distributor units, which are arranged on the anode and cathode sides adjacent to the separator, each flow distributor unit being designed to distribute a fluid supplied to it via the separator between the fluid supply channels and the fluid discharge channels

- Metallic frame elements which are connected to the separating device in a fluid-tight manner and which each enclose one of the flow distributor units circumferentially in a fluid-tight manner, the frame elements having through-openings which are designed to supply a fluid to the fluid-supply channels and through-openings which are designed to carry away a fluid discharged via the fluid-discharging channels .

The separating device can consist of a single separating plate unit or can comprise two separating plate units which are firmly connected to one another. The flow distributor units can be made from layers having recurring passages, in particular from layers in the form of expanded metals, woven fabrics and/or non-woven fabrics. The size of the passages of at least one flow distributor unit, in particular both flow distributor units, can increase in the direction of the separating device. A metallic gas diffusion layer can be fastened to one of the flow distributor units from the outside, in particular by means of soldering or welding, preferably to the flow distributor unit arranged on the anode side.

For example, all through-openings of one frame element are positioned in alignment with the through-openings of the other frame element. the Separator may be provided with through-holes positioned in alignment with the through-openings of the frame members and connecting them to the fluid supply channels and fluid discharge channels of the separator. For example, the components, in particular the separating device and the frame elements, have essentially rectangular outer circumferences. In particular, the outer circumferences are designed to be congruent.

For example, the anode-side fluid supply channels and the anode-side fluid discharge channels are arranged opposite to each other, and the cathode-side fluid supply channels and the cathode-side fluid discharge channels are arranged opposite to each other. The fluid supply ducts on the anode side and the fluid supply ducts on the cathode side can be arranged offset from one another by 90°. For example, the fluid supply channels and the fluid discharge channels are provided in the form of grooves formed on the anode-side and cathode-side surfaces of the separator, which grooves extend inward from the through-holes.

In one configuration, a multi-layer structure is arranged between the adjacent objects that are not intended to be joined to one another. The multi-layer structure includes a partition plate and parting means disposed on both sides of the partition plate.

Thus, the multi-layer structure includes, in this order, a first separator, a separator plate, and a second separator. In one embodiment, the multi-layer structure consists of the three layers mentioned. The separating plate is suitable for distributing compressive forces that act selectively on a first side over a large area on the other side.

The partition panel is in particular a rigid partition panel. It preferably enables the most uniform possible distribution of compressive forces. A mutual mechanical influence of the stacked modules is thus reduced or prevented. Typically, the separator plate has at least a stiffness equivalent to that of a 1mm thick steel plate. The partition plate can be a mineral partition plate. In particular, it is a solid partition plate. This configuration enables a particularly uniform loading or application of force to the components, even with a large number of assemblies to be manufactured in series, so that high quality can be guaranteed when many assemblies are manufactured quickly.

In one embodiment, the separating means is arranged directly between the adjacent objects that are not intended to be joined together. In other words, the two adjacent objects contact different sides of the same release agent. Accordingly, no additional separating plate is arranged here. In this way, the stack to be processed is lower and more assemblies can be manufactured in series.

A further aspect of the invention is the use of a separating means for separating two adjacent objects in a method for producing at least one assembly by welding. The release agent includes fibers or graphene. In the method, at least two components are joined together by applying a force acting along an axis.

In this way it is prevented that the two adjacent objects are joined together. In particular, the objects are arranged along an axis. All features, embodiments and effects of the method described above also apply accordingly to the use.

In one embodiment, a number of assemblies are produced in the method and the parting agent is arranged between components of different assemblies. A number of assemblies, each consisting of a number of components, are produced simultaneously and/or in series, and the release agent is arranged between the individual assemblies. In other words, the adjacent objects are components that are not intended to be joined together.

Exemplary embodiments of the invention are also explained in more detail below with reference to figures. Features of the exemplary embodiments can be combined with the claimed subject matter individually or in a plurality, unless stated otherwise. The claimed scopes of protection are not limited to the exemplary embodiments. Show it:

Figure 1: a first schematic representation of components to be welded,

FIG. 2: a representation of the components from FIG. 1 during welding,

Figure 3: a second schematic representation of components to be welded,

FIG. 4: a third schematic representation of components to be welded,

Figure 5: a first embodiment of a separating means,

FIG. 6: a second exemplary embodiment of a separating agent, and

FIG. 7: a third exemplary embodiment of a separating agent.

FIG. 1 shows a schematic representation of a step for carrying out the method according to the invention. Two press plates 25 of a mechanical press (not shown) are shown. The pressing plates 25 can be moved towards one another along the axis 20 and in this way exert a force aligned along the axis 20 . Components 10 of two assemblies to be produced are arranged between the pressing plates 25 . Above and below a separating means 30 are two components 10 shown schematically, namely metal plates, are arranged. The upper two components 10 are to be joined to form an upper assembly and the lower two components are to be joined to form a lower assembly.

The components described are shown in Figures 1, 3 and 4 in exploded fashion with spaces between them for clarity. All figures are schematic and do not necessarily reflect actual sizes or proportions.

The parting agent 30 is located between components 10 that are not to be joined together. This is brought to the desired positions before welding and serves as a physical separation of the surfaces that are not to be joined. The separating means 30 thus separates adjacent objects 15 which are arranged along the axis 20 and are not intended to be joined to one another. In FIG. 1, these objects are adjacent components 10 of different assemblies. Components 10 arranged along an axis 20 and separating means 30 located between them can also be referred to as a component stack.

FIG. 2 shows the joining of the assemblies by means of a force F. The force F is exerted on the stack of components by the pressure plates 25 described above. the Contact surfaces of the components 10 to be joined run perpendicularly to the axis, ie perpendicularly to the direction of action of the force. The joining takes place by diffusion welding in a vacuum furnace (not shown), which sets a vacuum with a pressure between 10 ^-5 mbar and 10 ^-4 mbar and a temperature between 700°C and 800°C. In this way, an assembly 12 is formed from two components 10 each. The resulting weld area 28 is highlighted in FIG.

The stacking described allows two assemblies to be produced simultaneously and in one process step. The components 10 of the two assemblies to be joined are all arranged along the axis 20, so the respective assemblies are manufactured in series. This increases the throughput and efficiency of the process. In one embodiment, at least 5 assemblies, in particular at least 10 assemblies, are produced in series.

In FIG. 3, on the other hand, only one assembly consisting of two components 10 is produced. Here the release agent 30 is outside of the components 10 to be joined between the outer component and the press plate 25. This prevents the component from adhering to the press plate, being connected to the press plate, being deformed by the press plate and from any adhering parts impurities is contaminated. In this case, the adjacent objects 15 that are not intended to be joined to one another are each a component 10 and a press plate 25.

FIG. 4 schematically shows a structure for the simultaneous manufacture of ten assemblies. Of these, 5 assemblies are produced in series and the two corresponding stacks of components are arranged next to one another, ie parallel, between the pressing plates 25 . An axis 20 runs through each of the component stacks, along which a force is exerted for joining the respective assemblies. The pressing device comprises pressing rams 26 which are arranged outside of the pressing plates 25 and which can be moved relative to one another along the axes 20 in order to apply the force for joining the assemblies.

All components 10 each consist of titanium. The upper assemblies are made of three components 10 each. The assemblies to be joined from this are bipolar plates 40 for forming an electrolysis or fuel cell stack. The other assemblies are made from two components 10 each. The components 10 located directly below the components 10 for the production of the bipolar plates 40 are used to produce an anode-side monopolar plate 42. The components 10 located at the very bottom are used to produce a cathode-side monopolar plate 44. In this way, the relevant components required for an electrolyzer can be produced in one process step. Bipolar plates 40 can be produced, for example, from a metallic separating device, two metallic flow distributor units and metallic frame elements to be connected to the separating device in a fluid-tight manner.

A separating means 30 is located between adjacent objects 15 that are not to be joined together. Between the upper press plate 25 and the uppermost component 10 there is a flexible, flat solid 32 as the separating means 30, namely a fleece containing or consisting of carbon fibers , also known as carbon fiber fleece. This is arranged directly between the respectively adjacent objects 15 . In this way, after the diffusion welding, the objects can be detached from one another and from the respective separating means 30 in a simple manner and—possibly after simple cleaning—without leaving any residue.

A multi-layer structure 34 is arranged in each case between the outer components 10 of the respective assemblies to be produced in series. The multi-layer structure 34 comprises two separating means 30 between which a separating plate 36 is arranged. The separating means 30 are also flat solids 32 and can also be in the form of a fleece made of carbon fibers. In particular, the two release agents 30 of the multi-layer structure 34 are of the same type. They can be attached to the partition plate 36 . The partition plate 36 is a stainless steel plate with a thickness between 1 mm and 10 mm. It has sufficient rigidity to prevent the adjacent components 10 from influencing each other mechanically.

FIG. 5 shows a first exemplary embodiment of a multi-layer structure 34 for separating adjacent objects during diffusion welding, so that they are not joined to one another. The multi-layer structure 34 consists of two separating means 30 between which a separating plate 36 is arranged. The separating means 30 are flat solid bodies 32 containing carbon fibers. They can be designed as fleece, paper or fabric with or made of carbon fibers. The separating means 30 arranged on the two sides of the separating plate 36 can be different be. The partition plate 36 is a solid component for distributing compressive forces as evenly as possible. The rigidity of the partition plate 36 is at least that of a 3 mm thick steel plate.

FIG. 6 shows a second exemplary embodiment of a multilayer structure 34. A monolayer or a thin layer of graphene is arranged on both sides of a separating plate 36. The exemplary embodiment of a separating means 30 illustrated in FIG. 7 is a single layer of fabric made from carbon fibers. In this case, a large number of fibers are combined as a bundle. The bundles are arranged perpendicularly to each other as warp and weft threads and alternately cross over and under each other. The alignment of the fibers essentially corresponds to the alignment of the fabric.

Reference List

component 10

assembly 12

item 15

axis 20

Press plate 25

Press stamp 26

I sweat 28

Force F

Separating agent 30

solid 32

Multi-layer structure 34

Separation plate 36

bipolar plate 40

Anode side monopolar plate 42

Cathode side monopolar plate 44

Claims

Expectations

1. A method for producing at least one assembly (12) by welding, in particular by diffusion welding, wherein at least two components (10) are joined to one another by applying a force F acting along an axis (20), with components arranged along the axis (20), adjacent objects (15) which are not intended to be joined together are separated from one another with a separating agent (30), the separating agent (30) comprising fibers or graphene.

2. The method according to the preceding claim, characterized in that a plurality of assemblies (12) each consisting of at least two components (10) are produced, the separating means (30) being arranged between adjacent components (10) arranged along the axis (20).

3. The method according to any one of the preceding claims, characterized in that the assemblies (12) are joined in an atmosphere with an elevated temperature, the temperature of the atmosphere being in particular between 500 °C and 1000 °C.

4. The method according to any one of the preceding claims, characterized in that the components (10) are at least temporarily exposed to a vacuum.

5. The method according to any one of the preceding claims, characterized in that the separating means (30) is a flat solid body (32).

6. The method according to any one of the preceding claims, characterized in that the separating means (30) comprises carbon fibers.

7. The method according to any one of the preceding claims, characterized in that the release agent (30) further contains an agent which reduces the adhesion of the release agent (30) to the surface of the object (15), or that the release agent (30) undergoes a surface treatment is subjected to reduce the adhesion of the release agent (30) to the surface of the article (15). Method according to one of the preceding claims, characterized in that a fleece, paper or fabric containing the fibers is used as the separating agent (30). Method according to one of the preceding claims, characterized in that the components (10) are metallic components (10), the components (10) being produced in particular from titanium. Method according to one of the preceding claims, characterized in that the at least one assembly (12) is a bipolar plate (40) or a monopolar plate, for example an anode-side monopolar plate (42) or a cathode-side monopolar plate (44), for forming an electrolysis or fuel cell stack . Method according to the preceding claim, characterized in that the bipolar plate (40) comprises the following components (10) which are joined together:

- Two metallic flow distributor units, which are arranged on the anode and cathode side adjacent to the separating device, each flow distributor unit being designed to distribute a fluid supplied to it via the separating device between the fluid supply channels and the fluid discharge channels,

- Metallic frame elements which are connected to the separating device in a fluid-tight manner and which each enclose one of the flow distributor units circumferentially in a fluid-tight manner, the frame elements having through-openings which are designed to supply a fluid to the fluid-supply channels and through-openings which are designed to carry away a fluid discharged via the fluid-discharging channels . Method according to one of Claims 1 to 11, characterized in that a multi-layer structure (34) is arranged between the adjacent objects (15) which are not intended to be joined together, the multi-layer structure (34) having a separating plate (36) and separating means (30) arranged on both sides of the separating plate (36). Method according to one of Claims 1 to 11, characterized in that the separating means (30) is arranged directly between the adjacent objects (15) which are not intended to be joined together. Use of a separating agent (30), which comprises fibers or graphene, for separating two adjacent objects (15) in a method for

Production of at least one assembly (12) by welding, in which process at least two components (10) are joined together by applying a force F acting along an axis (20). Use according to the preceding claim, characterized in that a plurality of assemblies (12) are produced and the separating means (30) is arranged between components (10) of different assemblies (12).