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). The end face (18) to be brazed is subjected to a mechanical pretreatment prior to the brazing process, at least in a region that is brought into contact with the brazing material (40).

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 101 35 611 A1 discloses a fusion welding method for surface-enhanced metal sheets, in particular for steel sheets having a metal and / or organic corrosion protection layer. In the method, it is provided that the corrosion protection layer is removed or partially removed in the region of the weld seam or weld points by application of thermally, chemically and / or abrasive blasting agents.CN 1 08 880 136 A discloses a method for producing an automobile stator or motor using iron-silicon sheets, which method has improved mechanical properties.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 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.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, the end face to be soldered is subjected to a mechanical pretreatment at least in a region which is brought into contact with the soldering material before the soldering process.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.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.By means of, for example, targeted blasting by means of suitable blasting material (ceramic mixture), the soft-iron laminated core is deformed on the side to be soldered in such a way that all gaps are at least largely and / or reliably closed and / or provided with a covering layer. In addition, coating residues are removed. A surface which is well wettable is formed.Thus, reliable wetting at the soldering location and / or a favorable soldering connection in the soldering connection zone without embedding unwanted constituents of the coating can 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 comprises wound sheets, wherein gaps between the individual sheets in the end face to be soldered are at least partially closed by the mechanical pretreatment. In addition, the mechanical pretreatment of the metal sheets produces a deformation layer on the end face to be soldered, so that the end face to be soldered is covered at least in regions by the deformation layer. The end face to be soldered can thus be wetted with solder material in a process-safe manner without coating particles being able to escape in the direction of the soldering zone during the soldering process.As a mechanical pretreatment, a blasting process is carried out with a jet of material to be blasted. As a result, a plastic deformation of the surface of the laminated core, in particular of regions of the end face to be soldered, can be achieved, which enables process-safe soldering.The material to be irradiated is electrically non-conductive and ceramic. The electrically non-conductive blasting material advantageously makes it possible to avoid otherwise possible introduction of electrical particles and thus impairment of the electromagnetic properties of the laminated core.The shot material is present in spherical form. With the spherical shot material, a particularly favorable pretreatment of the end face to be soldered can be achieved with regard to wettability with the solder material.According to a configuration of the method which is not according to the invention, an impact process, in particular denting, can be carried out as mechanical pretreatment. The treatment of the surface of the laminated core by means of a striking tool, for example with a hammer, can also produce a favorable deformation for a better process-safe soldering process.As a mechanical pretreatment, a machining process is carried out, which takes place before the blasting process. The roughing is performed by a machining method such as surface grinding. This machining process is preceded by the aforementioned blasting process.According to an advantageous embodiment of the method, an end side opposite the end side of the laminated core to be soldered can be subjected to a mechanical pretreatment. In an advantageous further development, the end face not to be soldered can thus also be subjected to such a surface treatment before the soldering. This can additionally prevent volatile constituents of the coating from evaporating into the brazing furnace space under the influence of temperature. The stabilization of the atmosphere of the soldering furnace can be assumed to increase the robustness of the soldering quality further.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. As a variant not according to the invention, the laminated core 10 can be stacked and welded or die-bonded.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.As a mechanical pretreatment, a blasting process is carried out with a jet of material to be blasted. The material to be blasted used is electrically non-conductive ceramic material to be blasted which is present in spherical form.As a variant not according to the invention, alternatively, a beating process, in particular denting, can also be carried out as a mechanical pretreatment.In addition, a machining process is carried out as mechanical pretreatment, which is carried out before the blasting process.As shown in FIG. 3 in the cross section of the laminated core 10 after the mechanical pretreatment, a deformation layer 30 is produced on the end face 18 to be soldered by the mechanical pretreatment of the sheets 12, 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 partially or completely closed or provided with a covering layer on the end face 18 to be soldered.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 is arranged on the end face 18 of the laminated core 10 to be soldered.The at least one weld seam section 60 can expediently form 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 can be advantageously pretreated in this case before the soldering process, in particular by means of a mechanical pretreatment. 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.As a mechanical pretreatment, a blasting process is carried out with a jet of material to be blasted. The material to be blasted used is electrically non-conductive ceramic material to be blasted which is present in spherical form.In addition, a machining process is performed before the blasting process.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 partially or completely closed or provided with a covering layer on the end face 18 to be soldered.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 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 solder material (40), wherein the end face (18) to be soldered is subjected to a mechanical pretreatment before the soldering process at least in a region which is brought into contact with the solder material (40), wherein the laminated core (10) comprises sheets (12) wound on one another, wherein gaps (16) between the individual sheets (12) in the end face (18) to be soldered are at least partially closed by the mechanical pretreatment, wherein the mechanical pretreatment of the sheets (12) produces a deformation layer (30) on the end face (18) to be soldered, such that the end face (18) to be soldered is at least regionally covered by the deformation layer (30), wherein a blasting process with a jet of a material to be blasted which is electrically non-conductive, is ceramic and is present in spherical form is carried out as the mechanical pretreatment, wherein a machining process is carried out as the mechanical pretreatment, which process takes place before the blasting process, and 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 welded seam section (60) is arranged on the end face (18) of the laminated core (10) to be soldered.Method according to Claim 1, wherein an end face (20) opposite the end face (18) of the laminated core (10) to be soldered is subjected to a mechanical pretreatment.

Images