DE102010035506A9 - Method for producing a component - Google Patents

Abstract

The invention relates to a method for producing a component, which is composed of at least a first and a second component, by means of powder injection molding (PIM), in particular metal powder injection molding (MIM), with the steps of providing first component as the first green body; Providing the second component as a second green compact; Connecting the green compacts to the component; Debinding of the component and sintering of the component, characterized in that the green compacts are connected by laser welding.

Description

The present invention relates to a method for producing a component, which is composed of at least a first and a second component, by way of powder injection molding, in particular of the metal powder injection molding, comprising the steps of: providing the first component as a first green compact; Providing the second component as a second green compact; Bonding the green compacts to the component; Debinding the component and sintering the component.

The invention further relates to a method for providing a complex green body for producing a component, which is composed of at least a first and a second component, and also to a method for providing a complex brown body for producing a component.

The so-called powder injection molding is well known. This is understood as the application of the widespread injection molding process as a new shaping process. Powder injection molding is subdivided into two production methods, namely metal powder injection molding and ceramic powder injection molding.

The entire process of powder injection molding takes place in four stages, namely material processing, shaping, debinding and sintering, which will be briefly discussed below.

1. Material preparation

In the production of powder injection molding compounds is worked with various binder systems. An attempt is made to homogenize ceramic or metal powder for injection molding machines. The aim of the treatment is the coating of all powder particles with the binder system, the destruction of agglomerates and the production of a homogeneous granulate, which is referred to as "feedstock". As starting materials for the injection molding of metal and ceramic powders, it is possible to use all commercially customary, sinterable powders of suitable particle size, such as, for example, oxide, silicate and nitride ceramics, carbides, translucent ceramics, metals and also metal alloys, including noble metals.

2. shaping

The so-called feedstock is processed in mostly modified injection molding machines. The masses are injected into liquid-tempered tools. After the injection molding process, the components, which are referred to as green parts or green parts, are removed from the mold.

3. Debindering

There are different binder systems that require equally different debindering processes. This is referred to as thermal, catalytic or solvent removal. After binder removal, the so-called "brown part" or "brown part" is obtained in the case of metallic parts and the "white part" or "white part" in the case of ceramic parts. These are very porous and have a minimal strength.

4. sintering

After debindering, the brownlings or white leaves are compacted by another thermal process. This achieves the final properties of the material, which in this process is referred to as "sintering" or "burning".

Powder Injection Molding (also referred to as Powder Injection Molding or PIM) can produce technically sophisticated and complex parts in an efficient manufacturing process with excellent tolerance compliance. Although the shrinkage in powder injection molding is on the order of about 20%, the highly reproducible process makes it possible to produce very precise and filigree components.

However, in the manufacture of complex parts, the shape constraints associated with injection molding are limited. For example, it is not possible to produce components with cavities by means of powder injection molding. In addition, it is not possible to produce components from different materials.

From the publication DE 103 31 397 A1 For example, a method of making components, vane segments, for a gas turbine is known, wherein each vane segment includes at least two vanes, and wherein the vane segment is made from a plurality of vanes by powder metallurgical injection molding (PIM). To produce a complex component, namely a blade segment, individual components, namely individual blades, are joined together in powder metallurgical injection molding, wherein three different ways are proposed. A first option proposed in this document for joining the blades to a blade segment is the joining in the green state, that is to say joining of green bodies. A second possibility for joining the blades to a blade segment is joining in the pre-sintered state and a third possibility of joining by spraying in a tool.

To connect the green compacts, it is further proposed in this publication that the position of the individual green compacts relative to each other, possibly by a device such. B. is secured by brackets. The shaped body thus formed, which consists of several green bodies, is then subjected to a uniform debinding process. This is followed by dewaxing and presintering, whereby a connection between the individual green bodies or then brownlings is so firmly present that the fixation of the individual molded bodies can be achieved via the clamps. Subsequently, the actual sintering of the entire molded body takes place in order to obtain the desired component.

The object of the present invention is to further simplify the manufacture of components which are composed of several components.

This object is achieved by the method mentioned above in that the joining of the green compacts takes place by laser welding.

In other words, in the first place, two or more green compacts are produced, which are to form the component in a composite manner. However, the joining of these green compacts does not initially take place mechanically via brackets and then presintering, as in the prior art, but by laser welding. The process of laser welding in the border or seam of two adjacent green compacts has the result that the plastic contained in the binder melts, so that a connection between the two green bodies is formed. This area will hereinafter be referred to as a connection zone.

This bond can be made so stable that mechanical fixtures, such as staples, are not required to feed the green compacts to a presintering or sintering process.

The process can thus be further simplified.

In a preferred development of the method, laser heat conduction welding, in particular laser heat conduction seam welding, is used. Particularly preferably, the laser is operated for welding in continuous wave mode for continuous heat input.

The uniform heat input has advantages with regard to the homogeneity of the melt and prevents high temperature peaks, the melt passes into the gas phase. Overall, the structure is significantly improved by the continuous heat input in the connection zone of two green compacts.

However, a uniform heat input is also possible by means of a laser, which is operated in the so-called "long pulse" mode. Again, local temperature peaks are prevented in the connection zone.

The use of a diode laser for laser welding has proven to be particularly advantageous. In addition to the advantageous results in welding, it is also an inexpensive component, so that the manufacturing cost can be reduced.

The use of a surface laser, whose beam is preferably widened, has also proved to be particularly advantageous.

The welding of the green compacts can be done either in sections or along the entire connection zone, depending on the strength of the connection between the green compacts is desired.

The diameter of the laser beam, its beam expansion, the power of the laser and the relative speed between the component and the laser beam are adjusted individually depending on the heat conduction of the component. The temperature in the welding zone is adjusted during the welding process in particular so that the binder melts, but the beginning of sintering is prevented.

This has proven to be particularly advantageous in practice, in particular with regard to the structure in the connection zone between the green bodies after sintering. When using a surface laser, it is particularly advantageous, for example, not to descend the connection zone continuously but stepwise, so that the laser beam remains at one point of the connection zone for a presettable period of time and then continues, during which process the laser beam is preferably switched off.

The method according to the invention for joining green compacts can also be used with particular advantage if the green compacts are made of different materials. The welding of the green compacts in the connection zone leads to a mixing of the metal particles of the two green compacts, so that after sintering an alloying zone is present, which ensures a very good and stable structure.

Of course, it is also conceivable that the green compacts consist of the same material. Overall, the inventive method therefore very flexible with regard to the selected materials of the green compacts.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention. In particular, the features defined in the claims can be combined as desired.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings. Showing:

1 a schematic perspective view of several composite green compacts;

2 a schematic representation of a portion of a connection zone between two green bodies for explaining the laser welding operation;

3a -C three schematic perspective views of two green compacts for explaining the laser welding process; and

4 a schematic flow diagram of the method according to the invention.

In 1 is a component 10 represented, which consists of three so-called greenlings 12 . 14 . 16 composed. The component 10 has in the variant shown purely by way of example a cylindrical shape, and consists of a total of three green bodies 12 . 14 and 16 together, which are stacked on top of each other. It should be noted at this point that it is the selected shape of the component 10 is an example, but should not limit the invention.

In order to make it clear that even complex components with cavities can be produced with the method according to the invention, such a cavity is 18 in the component shown 10 provided and graphically represented by dashed lines. This cavity 18 is due to superimposed pits in the green bodies 14 and 16 educated.

Such depressions are very easy to produce by way of injection molding.

Since the production of a green compact has already been briefly explained in the introduction and is also known to the person skilled in the art, this will not be discussed further here.

To the one from the three greenlings 12 . 14 and 16 existing component 10 The next step in the process, debinding, to be able to perform, it is necessary to connect the green compacts together.

This joining of the greenlings 12 . 14 . 16 takes place according to the invention by means of a laser 20 which is operated in continuous wave mode or in a pulsed (long pulse) mode. For example, a diode laser would be conceivable.

Using as even heat as possible in the edge or border area 22 two adjacent green compacts, it is achieved that the binder material heats and melts, so that the molten material in the border region 22 mixed the two green pieces and solidifies on cooling.

This creates a sufficiently strong and stable connection between adjacent green bodies in order to be able to handle them for the next process steps.

To join adjacent green compacts with each other in this manner, that is to weld, becomes a laser beam 24 along the adjacent border areas 22 the greenlings to be connected 12 . 14 . 16 guided, this one from the laser beam 24 irradiated area below as a connection zone 26 referred to as. This connection zone 26 is in 2 shown schematically as a black band.

In order to achieve a secure connection of two green compacts, it is necessary to weld in several places of the adjacent green compacts 12 . 14 . 16 make. It is preferable to weld along the entire boundary region.

For welding the two green compacts, it is necessary to move the green body itself or the laser beam or both to each other, so that the laser beam, the desired connection zone 26 scans.

The size of the connection zone 26 , in particular their extent perpendicular to an imaginary boundary line 22 between the two green bodies, can be adjusted on the one hand by the size of the laser beam diameter and / or by an additional scanning of the laser beam in this direction. In this case, the laser beam does not just travel along the boundary line 22 but also led vertically over the green bodies.

Another parameter for setting the connection zone 26 is the speed at which the green compacts and the laser beam are moved relative to each other. In addition to the relative speed of laser beam and green compact also plays the set power of the laser has a role in the formation of the connection zone, in particular their extension into the material of the green compacts inside.

Basically, these parameters should be selected so that the temperature in the connection zone during the welding process is adjusted so that the plastic in the binder melts, so that the materials of the green compacts (for example metal or ceramic powder) mix, but the sintering process does not start yet. In particular, when setting the parameters, it must be ensured that the plastic in the binder does not thermally decompose or oxidize.

In order to achieve these objectives, the use of a diode laser in continuous wave mode has been found to be suitable because the power is uniformly introduced into the joints and temperature peaks in the green bodies are avoided.

As a welding method, a heat conduction welding is preferably used, in which case beam intensities up to 100 kW / cm ² are used. With this method, in contrast to deep welding, so-called "key holes" can be avoided, ie cavities filled with steam in the depth of the green compacts to be welded.

After the various green compacts are joined together by thermal conduction welding, they are fed to the binder removal process and then to the sintering process to finally obtain the desired complex component consisting of different components. These different steps are exemplary in 4 specified.

In the 3a , b, c is another example of a complex component 10 shown, from two greenlings 12 . 14 will be produced. For simplicity, the same parts are identified by the same reference numerals, so that they can be dispensed with their repeated description.

Also in this example becomes a laser beam 24 along the borderline 22 led to a connection zone 26 bring about. At the laser 20 it is a surface laser whose beam 24 is widened, as shown schematically in 3b is clarified, and thus irradiated a surface whose shape / geometry is preferably adjustable. This not only circular but also oval, rectangular surfaces, etc. are achievable. The use of such a laser is designed to ensure that in the green compacts 12 . 14 introduced power per area is as small as possible. In order to achieve a melting of the binder in the connection zone, the irradiation time per area is increased instead.

In this case, the laser beam can be guided stepwise along the connection zone, so that a certain area is irradiated for a preferably predefinable period of time. After this period of time, the laser is continued by a preferably predeterminable path, so that as far as possible no overlap occurs between the previously irradiated surface and the surface to be newly irradiated. The path (pitch) is thus chosen depending on the dimensions of the irradiated area. The pitch may be different during an entire welding operation.

In 3b It is good to see that the connection zone 26 into the depths of the greenlings 12 . 14 extends what is marked with t. The amount t depends crucially on the material of the green compacts and the power input per area and is adjusted depending on the application.

The height h of the connection zone 26 can be determined on the one hand by the selected beam diameter of the laser 20 Adjust and / or through the track, along which the laser beam is guided. As already described above, the laser can also be perpendicular or oblique to the boundary line 22 be moved, so that an expansion of the connection zone 26 can be reached perpendicular to the borderline. In 3c such a procedure is shown schematically. There, the laser beam is spiraling along the boundary line 22 emotional.

As already mentioned, the green compacts can be made of different materials without problems when welding the adjacent green compacts. If various materials, in particular different metals, are used, an alloy zone is created in the connection zone after welding and thus melting of the binder. This alloying zone solidifies after debinding and sintering.

In summary, it can be seen that complex components can be produced by means of the aforementioned method. In particular, components with cavities or channels can be produced by, for example, two pot-type components being connected to one another by laser welding.

In addition, the aforementioned method also allows the production of thin-walled components. Finally, the above-mentioned method can also be used to produce components which consist of different materials.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10331397 A1 [0011]

Claims (15)

A method of producing a component composed of at least a first and a second component by means of powder injection molding (PIM), in particular metal injection molding (MIM), comprising the steps of: - providing the first component as the first green body; - Providing the second component as a second green compact; - connecting the green compacts to the component; - Debinding the component and - sintering of the component, characterized in that the joining of the green compacts takes place by laser welding. A method according to claim 1, characterized in that the laser welding is a laser thermal conduction welding, in particular a laser heat conduction seam welding. A method according to claim 1 or 2, characterized in that the laser is operated for welding in continuous wave mode for continuous heat input. A method according to claim 1 or 2, characterized in that the laser is operated in pulsed mode. Method according to one of the preceding claims, characterized in that a diode laser is used for laser welding. Method according to one of the preceding claims, characterized in that the green compacts are welded together in sections along their connection zone. Method according to one of claims 1 to 5, characterized in that the green compacts are welded along their entire connection zone. Method according to one of the preceding claims, characterized in that the diameter of the laser beam, power of the laser and the relative speed between the component and the laser beam are adjusted depending on the heat conduction of the component. Method according to one of the preceding claims, characterized in that the temperature is set in the welding zone during the welding operation so that the binder melts, but the beginning of sintering is prevented. Method according to one of the preceding claims, characterized in that a surface laser is used. A method according to claim 10, characterized in that the relative movement between surface laser and component takes place step by step. A method according to claim 10 or 11, characterized in that the beam of the laser is widened. Method according to one of the preceding claims, characterized in that the components consist of different materials. Method according to one of claims 1 to 12, characterized in that the components consist of the same material. Method of providing a complex green body for producing a component composed of at least a first and a second component by means of powder injection molding (PIM), in particular metal injection molding (MIM), comprising the steps of: - Providing a first green compact of the first component; - Providing a second green body of the second component; - connecting the green compacts to the complex green compact; characterized in that the joining of the green compacts takes place by laser welding.

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