Process for producing a soldered joint

Abstract

The invention relates to a method for producing a brazed assembly (100) comprising at least one laminated core (10), a brazing material (40), and a base body (50), wherein at least one end face (18) of the laminated core (10) to be brazed is connected to the base body (50) by means of a brazing process using the brazing material (40). Before the brazing process is carried out, at least individual sections of the laminated core (10) are connected by means of at least one weld seam section (60).

Description

The invention relates to a method for producing a soldered composite.Rotors of electric machines usually have a rotor carrier, onto which a soft-iron spiral laminated core can be soldered. For the mechanical connection of the laminated core to the rotor carrier, the soldered connection is of decisive importance in this case.DE 10 2010 002 003 A1 describes an electric motor body which comprises a plurality of stacked sheet metal stack modules, each sheet metal stack module having at least two individual sheets connected to one another by an adhesive. Furthermore, the sheet metal stack modules are directly on top of one another. Alternatively, an intermediate material is arranged between the sheet metal stack modules, which material differs from the adhesive.DE 10 2017 204 397 A1 describes a laminated core segment for an electric axial flux machine, having a stack of sheets which are electrically insulated from one another, having a tooth which is formed with the stack and is designed to receive a winding, and having a trapezoidal yoke which is formed with the stack and is designed to arrange a plurality of laminated core segments on one another to form a circumferential polygonal shape. Furthermore, a stator segment for an electric axial flux machine is described, having a laminated core segment, wherein the tooth formed with the stack is coated with a winding. Furthermore, a stator for an electric axial flux machine is described, having a plurality of circumferentially polygonally arranged laminated core segments arranged one against the other and / or a plurality of circumferentially polygonally arranged stator segments arranged one against the other.DE 10 2022 002 863 A1 discloses an axial flux machine having a rotor which has a rotor carrier, magnets held on the rotor carrier and cooling channels running within the rotor carrier, through which cooling air can flow in each case for cooling the rotor. A flow cross section through which the cooling air can flow can be adjusted by means of a valve device.From GB 2 617 146 A a method of manufacturing an axial flux permanent magnet machine is known, comprising a stator having a set of coils wound on respective stator bars and arranged circumferentially spaced about an axis of the machine, and a rotor comprising a rotor body carrying a set of permanent magnets on a layer of Merall laminate and mounted for rotation about the axis, and wherein the rotor and stator are spaced along the axis so as to define therebetween a gap in which the magnetic flux in the machine runs generally in an axial direction. The method includes brazing the metal laminate to the rotor body and joining the set of permanent magnets to the metal laminate, the metal laminate having a plurality of layers for reducing eddy currents.DE 10 2021 002 966 A1 discloses a method for producing a rotor core for a rotor of an axial flux machine, in which a metal strip is wound around an imaginary winding axis to form a coil to which magnets of the rotor can be fastened, as a result of which layers of the metal strip are arranged one on top of the other in the radial direction of the coil. The layers of the coil are connected to one another by a connecting means which is arranged between the respective layers in the radial direction of the coil and comprises a baking lacquer and / or an adhesive.DE 37 26 502 A1 discloses a method for producing a metal support body for a converter for exhaust gas purification, in particular in internal combustion engines of motor vehicles, which comprises a honeycomb-shaped body, held in a housing and provided on its surface with a catalytically active layer, made of layers of smooth and corrugated, heat-resistant steel sheets or foils which are alternately layered one above the other and connected to one another by brazing. The end face of the carrier body to be soldered is firstly wetted with a binder for applying the solder and the solder is then applied in the form of solder powder to the wetted end face of the carrier body.DE 10 2007 006 615 A1 discloses a method for producing a soldered and welded layered heat exchanger, consisting of a layered block having separating and cover plates and collecting boxes connectable to the layered block, comprising the method steps stacking the separating and cover plates to form a layered block, applying a defined compressive force on opposite sides of the layered block and generating a defined prestress in the layered block, preserving the prestress by applying welded seams to the layered block, depositing solder in the region of the layered block and soldering the layered block.DE 10 2018 133 207 A1 discloses a method for packaging at least two lamellae made of a composite material by gas-protected fusion welding, in which the composite material comprises a first and a second electrical strip layer and a plastic layer arranged therebetween.It is an object of the invention to specify an improved method for producing a soldered composite.The aforementioned object is achieved by a method according to claim 1.Advantageous embodiments and advantages of the invention are evident from the further claims, the description and the drawing.The invention proposes a method for producing a soldered composite from at least one laminated core, a solder material and a base body, wherein at least one end face of the laminated core to be soldered is connected to the base body by means of a soldering process by means of the solder material. In this case, before the soldering process is carried out, at least individual sections of the laminated core are connected by means of at least one weld seam section.The proposed method serves for soldering a laminated core to a base body, which is relevant in connection with the production of an electric machine. Specifically, the soldering of a wound electric strip onto a rotor carrier is described.It is proposed to connect the individual sections of the laminated core by means of at least one weld seam section before the soldering process is carried out, in order to prevent axial displacements of the individual sections with respect to one another. The laminated core is indeed largely secured in the radial direction. However, individual turns of the laminated core are not secured against axial displacement. Due to production and / or transport and / or handling, the individual windings of this laminated core can be axially displaced relative to one another before the soldering process or in the course of the soldering process, so that a gap is formed between the rotor carrier and the respective section.Advantageously, according to the proposed method, the problem of geometrically induced faulty soldering connection of the base body to the laminated core can be effectively countered by a welding operation upstream of the soldering process. By connecting individual sections of the laminated core by means of weld seam sections, an axial displacement of one winding or of a plurality of windings of the laminated core can be avoided.The welding pretreatment results in an improved preparation of a soldering process.This makes it possible to achieve a clearly improved flatness of the laminated core in the solder connection surface. Overall, an improved soldering connection of the base body / laminated core results and thus an increase in robustness of the soldering composite produced therewith. Furthermore, an increase in efficiency can be achieved in a favorable manner.The at least one weld seam section is arranged on the end face of the laminated core to be soldered. The weld seam sections for axially holding the sections of the laminated core can thus preferably be arranged on the end side, on which the soldered connection between laminated core and base body is also produced.According to an advantageous configuration of the method, a solder material can be used, the processing temperature of which is lower than a melting point of the weld seam section. The weld seam can typically have a melting point of approximately 1400° C. The solder material of the soldered connection is processed at approximately 1100° C., for example. The previously formed weld seam or the fixing of the sections of the laminated core realized therewith thus easily resists the subsequent soldering process.The at least one weld seam section is embedded in the solder material and connected to the base body in a materially bonded manner by means of the solder material. This results in a stable mechanical connection between the laminated core and the weld seam sections arranged thereon on the one hand and the base body on the other hand.The at least one weld seam section forms a welding depth in sheets of the laminated core of at most 2 mm, preferably of at most 1 mm, particularly preferably of at most 0.8 mm. In this way, sufficient mechanical fixing of the individual sections of the laminated core relative to one another can be achieved.The at least one weld seam section is pretreated prior to the soldering process. In this case, the at least one weld seam section is subjected to a mechanical pretreatment before the soldering process.Electric laminated cores and thus also the soft-iron laminated core of a rotor carrier usually have a coating in order to prevent a magnetic short circuit. These coatings consist, for example, of an inorganic fraction and an organic carrier fraction.By mechanically pretreating the end face to be soldered, at least in a region which is brought into contact with the brazing material, prior to the soldering process, disruptive influences of the coating, which can otherwise occur as a result of the high-temperature stress during soldering, in particular during brazing, on account of impurities, for example coating residues and fires of this coating, and / or wetting problems, can be avoided.The mechanical preprocessing carried out before the soldering has the purpose of substantially mechanically closing and / or cleaning the side or surface to be soldered to the base body.Reliable wetting at the soldering location and / or optimum soldering connection in the soldering connection zone without incorporating unwanted constituents of the coating can thus be ensured.The suitable mechanical pretreatment of the laminated core enables an improved, process-safe soldered connection between the carrier material and the laminated core. As a result of this preparation, volatile constituents of the coating are effectively kept away from the soldering zone under the influence of temperature, and at the same time, the wettability of the laminated core is increased by the geometric optimization in the soldering connection region.The better wettability in particular increases the range of usable solder systems. It is thus also possible to use ductile, environmentally friendly and favorable copper solder materials which generally react more sensitively to impurities such as fires. With an increase in ductility in the soldered joint, an improved process control during production, for example if straightening is required, and / or an increase in operating strength can also be assumed.The laminated core with the at least one weld seam section is coated with the brazing material before the brazing process, wherein the at least one weld seam section is at least partially covered by the brazing material. By avoiding an axial displacement of one winding or of a plurality of windings of the laminated core, zones with good soldering connection of laminated core / solder material / base body result throughout. The weld seam section is thereby advantageously embedded in the soldering zone. Optionally, the weld seam section can become effective as a point spacer to the base body.The laminated core comprises electric sheet material or is formed from electric sheet material. In this case, sheets of the laminated core are coated on at least one side face. Electric laminated cores and thus also the soft-iron laminated core of a rotor carrier usually have a coating in order to prevent a magnetic short circuit. These coatings usually consist of an inorganic fraction and an organic carrier fraction.With such a method, a soldered composite can be produced from at least one laminated core, a base body and a solder material.This soldered composite has an advantageous connection between laminated core and base body by means of the solder material. This achieves a significantly higher robustness of the produced workpiece, which contributes to an increase in the service life.The soldered composite is designed as a component for an electromotive application, in particular as a rotor or part of a rotor of an electromotive application. Due to its great robustness, the soldered composite can be used particularly favorably for electromotive applications and thus advantageously contribute to a long service life of electric machines.Further advantages are evident from the following description of the drawings. The drawings illustrate an embodiment of the invention. The drawings, specification and claims contain numerous features in combination. The skilled person will expediently also consider the features individually and summarize them to form meaningful further combinations.The following are shown: FIG. 1 shows a cross section through a laminated core which is subjected to a mechanical pretreatment prior to a soldering process according to a method according to the invention; FIG. 2 is a plan view of a wound laminated core; FIG. 3 shows the laminated core after the mechanical pretreatment in cross section; FIG. 4 shows a soldered composite made of a laminated core, a base body and a solder material, produced according to the method according to the invention; FIG. 5 shows a cross section through a laminated core which has been subjected to a mechanical pretreatment according to a further exemplary embodiment of the invention before a soldering process; FIG. 6 shows a plan view of a wound laminated core, in which individual sections of the laminated core are connected by means of weld seam sections according to a method according to the invention, with sectional planes A and B drawn in; FIG. 7 shows a plan view of a wound laminated core with a further arrangement of a weld seam section; FIG. 8 shows a plan view of a wound laminated core with a further arrangement of a weld seam section; FIG. 9 shows a soldered composite made of a laminated core, a base body and a solder material, produced according to the method according to the invention, in a cross section of the sectional plane A according to FIG. 6 ; FIG. 10 shows the soldered joint according to FIG. 9 in a longitudinal section of the sectional plane B according to FIG. 6 ; and FIG. 11 shows the soldered composite according to FIG. 9 in a longitudinal section of the sectional plane B according to FIG. 6, produced with a method according to a further exemplary embodiment.In the figures, identical or similar components are denoted by identical reference numerals. The figures merely show examples and should not be understood as limiting.FIG. 1 shows a cross section through a laminated core 10, which is subjected to a mechanical pretreatment prior to a soldering process according to a method according to the invention. The mechanical pretreatment is indicated schematically in FIG. 1 with an arrow which is directed at an end face 18 to be soldered.The laminated core 10 has individual laminations 12 stacked one on top of the other in cross section. The stacking direction extends in the horizontal direction in the figure. Gaps 16 are formed between the metal sheets 12. The laminated core 10 can be wound in spiral form starting from a long strip-shaped sheet metal strip and optionally fixed in a materially integral manner at the trailing ends.The individual sheets 12 of the laminated core 10 are provided on both side faces 34, 36 with an in particular insulating coating 14. The thickness 26 of the coating 14 may typically be between 1 μm and 20 μm.Typical dimensions of the sheets 12 can be, for example, 0.1 mm to 1.0 mm, preferably 0.5 mm, as width 22, and 2 mm to 20 mm, preferably 3 mm to 8 mm, particularly preferably 6 mm, for example, as height 24.FIG. 2 shows, by way of example, a spirally wound laminated core 10 in plan view. In the example shown, the sheet material is first produced in long strips and then wound up in spiral form. The stacking direction runs in the radial direction in the figure. Optionally, ends of the sheet metal strip for shape retention of the wound laminated core 10 can be connected to the laminated core 10 by means of fixations 28.A soldered composite 100 can be produced from such a laminated core 10, a solder material 40 and a base body 50. At least one end face 18 of the laminated core 10 to be soldered is connected to the base body 50 by means of a soldering process by the soldering material 40.According to the proposed method, the end face 18 to be soldered is subjected to a mechanical pretreatment at least in a region which is brought into contact with the soldering material 40 before the soldering process. The mechanical pretreatment of the end face 18 is indicated schematically in FIG. 1 with the arrow.During the mechanical pretreatment, the gaps 16 between the individual sheets 12 are at least partially closed in the end face 18 to be soldered. The coating 14 of the metal sheets 12 can at least partially decompose, for example evaporate, or evaporate, due to the temperature influence during soldering.The mechanical pretreatment can effectively prevent parts of this coating 14 from moving through the gap 16 in the direction of the brazing material 40 and thereby causing a change in the brazing composition and / or causing a deterioration in the wettability of the laminated core 10 by the brazing material 40.In a variant not according to the invention, a blasting process with a jet of material to be blasted can be carried out, for example, as a mechanical pretreatment. In this case, electrically non-conductive shot material, for example ceramic shot material, can preferably be used as shot material. The grit can be present, for example, in spherical form.According to the invention, however, a deanglement as impact process is carried out as mechanical pretreatment.In addition, a machining pretreatment takes place before the plastic deformation process of the surface.As shown in FIG. 3 in the cross section of the laminated core 10 after the mechanical pretreatment, a deformation layer 30 can be produced by the mechanical pretreatment of the sheets 12 on the end face 18 to be soldered, such that the end face 18 to be soldered is covered by the deformation layer 30 and the gaps 16 are thereby completely closed on the end face 18 to be soldered and are provided with a covering layer.The deformation layer 30 can effectively prevent material of the coating 14 from entering the solder material 40 during the soldering process.FIG. 4 shows a soldered composite 100 made of a laminated core 10, a base body 50 and a solder material 40, produced according to the method according to the invention.In this case, the brazing material 40 is arranged between the base body 50 and the deformation layer 30 of the end face 18 of the laminated core 10 to be brazed. The brazing material 40 can be applied to the base body 50 or to the end face 18 of the laminated core 10 to be brazed, i.e. the deformation layer 30, before the brazing process. Alternatively or additionally, the solder material 40 can also be introduced between the deformation layer 30 and the base body 50, for example, in powder form or in film form.Advantageously, after the soldering process, an optimized soldering composite 100 is thus produced by keeping the soldering bath clean, optimized bonding surface and optimized wettability of soldering material 40 to laminated core 10.The soldered composite 100 can be used expediently as a component for an electromotive application, in particular as a rotor or part of a rotor of an electromotive application.FIG. 5 shows a cross section through a laminated core 10 which has been subjected to a mechanical pretreatment according to a further exemplary embodiment of the invention before a soldering process.In this case, an end side 20 opposite the end side 18 of the laminated core 10 to be soldered was likewise subjected to a mechanical pretreatment. In this way, the laminated core 10 has not only a deformation layer 30 on the end side 18, but also a further deformation layer 32 on the opposite end side 20.Thus, a passage of material of the coating 14 during the soldering process through the deformation layer 30 as a barrier of the end side 18 and also through the deformation layer 32 as a barrier of the end side 20 can be effectively prevented. The coating material 14 thus remains at least largely encapsulated in the interior of the laminated core 10.FIG. 6 shows a plan view of a wound laminated core 10, in which, according to a method according to the invention, individual sections of the laminated core 10 are connected by means of weld seam sections 60, with sectional planes A and B drawn in.The laminated core 10 shown in FIG. 6 is wound spirally. The sheet material is first produced in long strips and then wound up in spiral form. Optionally, ends of the sheet metal strip for shape retention of the wound laminated core 10 can be connected to the laminated core 10 by means of fixations 28.The laminated core 10 advantageously comprises electric sheet material or is formed from electric sheet material. In this case, the sheets 12 of the laminated core 10 can be coated on at least one side face 34, 36 with an, in particular insulating, coating 14.A soldered composite 100 can be produced from such a laminated core 10, a solder material 40 and a base body 50. At least one end face 18 of the laminated core 10 to be soldered is connected to the base body 50 by means of a soldering process by the soldering material 40.According to the proposed method, at least individual sections of the laminated core 10 are connected by means of at least one weld seam section 60 before the soldering process is carried out.In this case, the at least one weld seam section 60 can preferably be arranged on the end face 18 of the laminated core 10 to be soldered.The at least one weld seam section 60 expediently forms a welding depth in sheets 12 of the laminated core 10 of at most 2 mm, preferably of at most 1 mm, particularly preferably of at most 0.8 mm.The laminated cores 10 are thus at least largely secured against displacement in the axial direction by at least one weld seam section 60 before the soldering. In order to prevent an undesirable short-circuit situation at the later effective surface, the axial securing is effected by the at least one weld seam section 60 on the end face 18, which is subsequently soldered towards the base body 50.In the exemplary embodiment shown in FIG. 6, the laminated core 10 is connected by four weld seam sections 60, which each extend over a plurality or all of the laminated core sections.FIG. 7 shows a laminated core 10 connected by a welded seam section 60, which extends in each case over a plurality of or all of the sheet metal sections.FIG. 8 shows a further exemplary embodiment, in which a weld seam section 60 extends in each case over a plurality of or all of the sheet metal sections.FIG. 9 shows a soldered composite 100 made of a laminated core 10, a base body 50 and a solder material 40, produced according to the method according to the invention, in a cross section of the sectional plane A according to FIG. 6.In this case, the cross section takes place along the weld seam section 60, which was produced before the soldering process. By avoiding an axial displacement of one winding or of a plurality of windings of the laminated core, zones with good soldering connection result throughout between laminated core 10, solder material 40 and base body 50.In particular, the weld seam section 60 can be connected to the base body 50 in a materially integral manner by means of the brazing material 40.The brazing material 40 can be introduced between the base body 50 and the laminated core 10 before the brazing process, for example in powder form. Thus, the solder material 40 can be applied as a powder to the base body 50.In a further embodiment, the brazing material 40 can be applied to the laminated core 10 in paste form before the brazing process, for example printed, in particular screen-printed, or roll-rolled. Thus, the laminated core 10 with the weld seam section 60 can be coated with the brazing material 40 before the brazing process. In this case, the weld seam section 60 can be at least partially covered by the brazing material 40.Alternatively or additionally, the brazing material 40 can be applied to the base body 50 in paste form, for example printed, in particular screen-printed, or roll-rolled.Alternatively or additionally, the solder material 40 can also be introduced as a foil between the base body 50 and the laminated core 10.The described methods of applying solder can also be used in combination.Advantageously, a solder material 40 can be used, the processing temperature of which is lower than a melting point of the weld seam section 60. The solder material 40 of the soldered connection is processed at approximately 1100° C., for example. The previously formed weld seam or the fixing of the sections of the laminated core 10 realized therewith thus easily resists the subsequent soldering process.FIG. 10 shows the soldered composite 100 according to FIG. 9 in a longitudinal section of the sectional plane B according to FIG. 6, i.e. perpendicular to the longitudinal direction of the weld seam section 60.The good soldering connection between laminated core 10, solder material 40 and base body 50 and the embedding of welded seam section 60 in solder material 40 can be seen.Advantageously, after the soldering process, an optimized soldering composite 100 is thus produced by an improved soldering connection of the base body 50 to the laminated core 10 and thus an increase in robustness.The soldered composite 100 can be used expediently as a component for an electromotive application, in particular as a rotor or part of a rotor of an electromotive application.FIG. 11 shows the soldered composite 100 according to FIG. 9 in a longitudinal section of the sectional plane B according to FIG. 6, produced by a method according to a further exemplary embodiment.The weld seam section 60 is advantageously mechanically pretreated before the soldering process. Thus, a favorable soldering connection between laminated core 10 and base body 50 can be achieved by means of the soldering material 40.The mechanical pretreatment can advantageously take place as shown in FIGS. 1 to 5.In a variant not according to the invention, a blasting process with a jet of material to be blasted can be carried out, for example, as a mechanical pretreatment. In this case, electrically non-conductive shot material, for example ceramic shot material, can preferably be used as shot material. The grit can be present, for example, in spherical form.According to the invention, however, a deanglement as impact process is carried out as mechanical pretreatment.In addition, a machining pretreatment takes place before the plastic deformation process of the surface.A deformation layer 30 is produced by the mechanical pretreatment of the metal sheets 12 on the end face 18 to be soldered, so that the end face 18 to be soldered is covered at least in regions by the deformation layer 30. The gaps 16 are thereby completely closed at the end face 18 to be soldered and are provided with a covering layer.The deformation layer 30 can effectively prevent material of the coating 14 from entering the solder material 40 during the soldering process.As can be seen in FIG. 11, the deformation layer 30 is arranged on the end face 18 of the laminated core 10 to be soldered between the laminated core 10 and the soldering material 40. In this case, the weld seam section 60, which is partially embedded in the brazing material 40, protrudes through the deformation layer 30 into the sheet metal material of the laminated core 10, since the mechanical pretreatment does indeed take place before the brazing process but preferably after the welding process.List of reference characters10 Laminated core 12 Sheet 14 Coating 16 Gap 18 End face 20 End face 22 Width 24 Height 26 Thickness Coating 28 Fixing 30 Deformation layer 32 Deformation layer 34 Side surface 36 Side surface 40 Brazing material 50 Base body 60 Weld seam section 100 Brazing composite

Claims

Method for producing a soldered composite (100) from at least one laminated core (10), a solder material (40) and a base body (50), wherein the soldered composite (100) is formed as a component for an electric motor application, wherein the laminated core (10) is formed as a wound electric strip and the base body (50) is formed as a rotor carrier, wherein the laminated core (10) comprises electric sheet material or is formed from electric sheet material, wherein sheets (12) of the laminated core (10) are coated on at least one side surface (34, 36), wherein at least one end face (18) of the laminated core (10) to be soldered is connected to the base body (50) by means of a soldering process by means of the solder material (40), wherein at least individual sections of the laminated core (10) are connected by means of at least one welded seam section (60) before carrying out the soldering process, wherein the at least one weld seam section (60) is arranged on the end face (18) of the laminated core (10) to be soldered, wherein the laminated core (10) is coated with the solder material (40) by the at least one weld seam section (60) before the soldering process, wherein the at least one weld seam section (60) is embedded in the solder material (40), is at least partially covered by the solder material (40) and is bonded to the base body (50) by means of the solder material (40), wherein the at least one weld seam section (60) forms a welding depth in sheets (12) of the laminated core (10) of at most 2 mm, wherein the at least one weld seam section (60) is subjected to a mechanical pretreatment before the soldering process, wherein a degelling is carried out as the mechanical pretreatment as the impact process, wherein the end face (18) to be soldered is bonded to the base body (50) at least in a region, which is brought into contact with the brazing material (40), is subjected to a mechanical pretreatment before the brazing process, wherein a deformation layer (30) is produced on the end face to be brazed by the mechanical pretreatment of the sheets (12), such that the end face (18) to be brazed is covered by the deformation layer and the gaps (16) are thereby completely closed on the end face (18) to be brazed and are provided with a covering layer, wherein a machining pretreatment takes place before the plastic deformation process of the surface.Method according to Claim 1, wherein a solder material (40) is used, the processing temperature of which is lower than a melting point of the weld seam section (60).Method according to one of the preceding claims, wherein the at least one weld seam section (60) forms a welding depth in sheets (12) of the laminated core (10) of at most 1 mm and preferably of at most 0.8 mm.

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