Method for packaging sheet metal parts from an electrical steel strip or sheet into at least one sheet stack with at least one cooling channel

Abstract

The invention relates to a method for packaging sheet metal parts (4) from an electrical steel strip (3) or sheet to form at least one sheet stack (2) with at least one cooling channel (2a). According to the invention, in order to create a leak-free cooling channel (2a), a leak test (11) of the cooling channel (2a) of the pre-glued sheet metal stack (2) is carried out and, if a leak is detected, the adhesive (8) of the stacked sheet metal parts (4) is placed under a second pressure (P2) in the axial direction (A) of the stacked sheet metal parts (4) in order to produce the required tightness.

Description

[0001] Method for bundling sheet metal parts from an electrical strip or sheet into at least one sheet package with at least one cooling channel

[0002] Technical area

[0003] The invention relates to a method for bundling sheet metal parts made of an electrical strip or sheet into at least one sheet stack with at least one cooling channel.

[0004] State of the art

[0005] When manufacturing laminated cores from sheet metal parts coated with a hot-melt adhesive layer, it is known (WO2021175875A1) to subject the laminated core, and thus the hot-melt adhesive layer, to axial pressure when bonding the sheet metal parts in order to ensure a desired core height. In addition to a precise core height, full-surface bonding between the sheet metal parts is also necessary - this is particularly important if the laminated core is required to be pressure-resistant during liquid cooling. Such requirements exist, for example, for laminated cores in the high-performance range, for example in electric motors, where laminated cores usually have several cooling channels through which a liquid fluid, namely a coolant, flows.

[0006] If a leak occurs during a leak test on the finished laminated core, the cooling channel must be subsequently sealed, which is comparatively complex and therefore in most cases leads to the rejection of the final bonded laminated core.

[0007] Description of the invention The invention therefore has the object of modifying the method described at the outset for producing a laminated core with a cooling channel in such a way that laminated cores with a liquid-tight cooling channel can be produced reproducibly.

[0008] The invention solves the problem by the features of claim 1.

[0009] By performing a leak test on the cooling channel on the pre-bonded sheet stack and not, as in the prior art, on the final bonded sheet stack, it is possible, in contrast to the prior art, to take action at the bond between the sheet metal parts. This makes it possible, upon detection of a leak, to subject the stacked sheet metal parts to a second axial pressure in order to act on any defects in the adhesive bond – thus, to repair them. This is achievable because the gel point of the adhesive polymer has not been reached or exceeded for the pre-bonding process. Therefore, even with the pressure according to the invention, the adhesive can still be influenced in its pre-bonded state with regard to its bonding.For example, this can result in a more extensive contact and / or a contact surface being better dissolved by a solvent in the adhesive and / or a closer interlinking of the adhesive's polymer chains, etc., in order to achieve the required tightness at the bonding of the sheet metal parts. In contrast to the prior art, measures can be taken to correct defects in the tightness of the fluid channel before the final bonding of the sheet metal parts to the laminated core, whereby reproducibly liquid-tight laminated cores can be produced using the method according to the invention.

[0010] The thermally activatable adhesive for pre-bonding preferably has a first temperature which is greater than the glass transition temperature of the adhesive and lower than the activation temperature of the adhesive. This prevents the thermally activatable adhesive from adhering to a joining surface during pre-bonding without yet entering a cured state, for example through crosslinking. This makes it possible to still influence the adhesive bond in the event of a detected leak in order to create the tightness required for the finally bonded sheet stack during the process. This finally bonded state is achieved by final heating the thermally activatable adhesive to a second temperature which is greater than or equal to the activation temperature, thus finally bonding the sheet metal parts together.

[0011] The thermally activated adhesive can, for example, be a hot-melt adhesive varnish, also known as a self-adhesive varnish. In the case of a hot-melt adhesive varnish, the activation temperature represents the bonding temperature of the hot-melt adhesive varnish.

[0012] During the leak test, a gaseous fluid is preferably introduced into the cooling channel to detect a leak. A test gas, for example, can be used for this purpose. In particular, the use of a gaseous fluid for the leak test can ensure a fast process, making it suitable for inline production of laminated cores.

[0013] If the gaseous fluid contains helium and / or hydrogen, this can enable the detection of even a small leak in a comparatively short test time. For example, the gaseous fluid is a forming gas.

[0014] The test time for the leak test can be further reduced if an overpressure is applied to the pre-bonded laminated core in the cooling channel to be tested for leaks and / or a negative pressure is applied outside the cooling channel to be tested for leaks. In particular, an overpressure in the cooling channel to be tested in the range of 0.1 to 2 bar can be suitable for this purpose – i.e., a pressure 0.1 to 2 bar higher than the pressure acting on the laminated core from the outside.

[0015] During the leak test, the pre-bonded laminated core is preferably placed in a vacuum chamber to further increase the sensitivity of detecting even the smallest bonding defects. This further increases the reproducibility of the process in the production of laminated cores with liquid-tight cooling channels.

[0016] The system can be deemed sufficiently liquid-tight if the leak test reveals a leak up to a leak rate of 10'4 mbar l / s (millibar*liter / second) is detected (measured according to DIN EN 1779). Preferably, a leak rate in the range of 10- 3 mbar l / s to 10' 4 mbar l / s is detected - which can ensure a comparatively short test time.

[0017] Preferably, the adhesive has the first temperature during the second pressurization in order to utilize this state of the adhesive to be able to repair any defects in the bond more quickly and reproducibly.

[0018] The reliability of correcting defects in the bonding of sheet metal parts that lead to leaks can be further increased if the second pressurization involves at least one pressure pulse. This can, for example, even overcome differences in the flow properties of the hot melt adhesive layers – which can further promote full-surface bonding between the sheet metal parts by forming a more homogeneous boundary layer.

[0019] For example, the pressure pulse can be applied by applying pulse pressure or relieving it by using pulse pressure.

[0020] The second pressurization may also have multiple pressure pulses.

[0021] Preferably, the pressure pulse applies pulse pressure to the adhesive in the range of 0.5 to 10 N / mm 2 (Newton / square millimeter). However, it may already be sufficient if the impulse pressure is in the range of 2 to 6 N / mm 2For example, the second pressurization occurs with pressure pulses that follow one another directly. This can occur periodically, for example. This period T can be in the range from 0.1 to 20 seconds. Particularly simple process conditions can arise if the first temperature is in the range from 80 to 220 °C. Preferably, the first temperature is in the range from 80 to less than 180 °C. For example, the first temperature is in the range from 100 to 150 °C, which can minimize the risk of hot melt adhesive being squeezed out of the adhesive gap between the sheet metal parts.

[0022] The process conditions can be further simplified, for example, if the second temperature is in the range from 180 °C to 250 °C, in particular in the range from 180 °C to 220 °C.

[0023] Preferably, sheet metal parts that have an adhesive layer on one of their flat sides are stacked on top of each other. In particular, if sheet metal parts that have a hot-melt adhesive layer on both of their flat sides are stacked on top of each other, the resistance of the sheet stack to liquid cooling can be further increased, for example, because the bond is reduced to a connecting surface between two similar joining partners. Furthermore, this allows the pressure pulse to influence the two viscous hot-melt adhesive layers simultaneously, which can further improve the bond between them and thus the sheet metal parts.

[0024] For example, the thickness of each sheet metal part is between 0.09 and 0.49 mm, in particular 0.09 to 0.29 mm, and / or the thickness of the adhesive layer of each sheet metal part is between 2 and 12 pm, in particular 4 to 8 pm. This provides particularly advantageous conditions for high reproducibility of the process.

[0025] A comparatively high hydraulic pressure in the cooling channel can be absorbed, for example, if the stacked sheet metal parts are fully pre-bonded and / or bonded to form a sheet stack. For example, the leak test can be made easier to handle and / or improved in reproducibility if a relief is created in the adhesive, in particular hot-melt adhesive varnish, on one end of the sheet stack by embossing for the leak test or during the leak test of the cooling channel. Preferably, the relief adjoins the cooling channel and / or is provided in sections on the end of the sheet stack. The relief can also encompass the cooling channel, in particular completely.

[0026] This relief can be created by embossing the adhesive, particularly the adhesive layer, of the pre-bonded laminated core. It is also conceivable for the relief to be created by embossing the adhesive, particularly the adhesive layer, of the final bonded laminated core. This is particularly useful if a leak test of the laminated core is performed after final bonding.

[0027] For example, the pressure resistance of a connection to the cooling channel can be increased if the relief has depressions and relief structures that stand out from these depressions.

[0028] It may prove advantageous if the relief structures have a structure height of at least 1 pm, in particular at least 2 pm.

[0029] For this purpose, the relief structures can also have a maximum structure width of at least 200 pm, in particular at least 500 pm.

[0030] In addition, it is conceivable that the depressions have a maximum depression width between two successively arranged relief structures of at least 50 pm, in particular at least 100 pm.

[0031] Preferably, the structural width and depression width are seen in the longitudinal extension of the relief.

[0032] The above can be further improved, for example, if the relief forms a pattern with a regular, particularly periodic, structure, in particular a nub pattern, groove pattern, grid pattern, checkerboard pattern, waffle pattern, or honeycomb pattern. The relief can be more easily provided in the adhesive if the adhesive has a temperature during embossing that is higher than the glass transition temperature of the adhesive. This is preferably the first temperature (tempi).

[0033] To further simplify the process, it is also conceivable that an adapter is connected to the cooling channel during the leak test, which creates the relief by embossing.

[0034] Short description of the drawings

[0035] The figures show, for example, the subject matter of the invention in more detail using an embodiment variant.

[0036] Fig. 1 is a schematic representation of an apparatus for carrying out the method according to the invention,

[0037] Fig. 1 a is an enlarged view of a part for leak testing of the device according to Fig. 1,

[0038] Fig.2 a sectional view of an adhesive gap leading to a leak between two sheet metal parts of a sheet package and

[0039] Fig.3 a sectional view of the adhesive gap of Fig. 2 after detection of a leak and setting under second pressure,

[0040] Fig. 4a is a schematic partial view of Fig. 1 a and

[0041] Fig. 4b is a schematic plan view of one end face of the laminated core having two end faces according to Figure 4a.

[0042] Way to implement the invention

[0043] Figure 1, for example, shows a device 1 for continuously producing laminated cores 2. The laminated cores 2 shown as examples are preferably used for electromagnetic components, for example, for electrical machines, and have at least one off-center cooling channel 2a extending axially through the laminated core 2. When the laminated core 2 is in use, a liquid fluid, namely a cooling liquid, flows through the cooling channel 2a to cool the laminated core 2.

[0044] To produce a laminated core 2 with the cooling channel 2a, the device 1 - see Fig. 1 - is used to separate several sheet metal parts 4 with a recess 4c from an electrical strip 3. These recesses 4c of the sheet metal parts 4, after stacking one on top of the other, form the cooling channel 2a in the laminated core 2 - which, in the exemplary embodiment, runs completely through the laminated core 2 in the axial direction A of the laminated core 2. In the exemplary embodiment, the recesses 4c have a closed edge. The shell of the cooling channel 2a is therefore completely delimited by the laminated core 2 itself. However, it is also conceivable for the shell of the laminated core 2 to have the cooling channel and thus not completely delimit it, which has not been shown in more detail.

[0045] The electrical steel strip 3 used for the sheet metal parts 2 has, on at least one of its flat sides 3a, 3b—in the exemplary embodiment, on both—a layer 7 of adhesive 8, namely a thermosetting hot-melt adhesive 8a, for example, comprising an epoxy resin base and dicyandiamide as a crosslinking agent. The thermosetting or heat-curing hot-melt adhesive 8a is also referred to as a self-bonding varnish. For example, a catalyzed self-bonding varnish can be used, such as a self-bonding varnish with a deposit coating for faster curing.

[0046] The hot-melt adhesive 8a on the electrical steel strip 3 is in the B-stage. The glass transition temperature Tg of the hot-melt adhesive 8a used, for example, is in the range of 65 to 85 °C (degrees Celsius), measured according to ISO 11357-2. The caking temperature, as the activation temperature, of the hot-melt adhesive 8a used, for example, is in the range of greater than or equal to 180 degrees Celsius. However, these characteristic values ​​for the glass transition temperature Tg and / or caking temperature can vary depending on the hot-melt adhesive 8a used. The sheet metal parts 4 are separated using a punching tool 5, which can also be part of a subsequent punching tool (not shown). Other devices for separating sheet metal parts 4, for example using a laser, are conceivable. The punching tool 5 also creates the recess 4c in the sheet metal part 4 for the cooling channel 2a in the laminated core 2 in the electrical strip 3, for example in the form of a preferably circular hole, as can be seen in Fig. 2.

[0047] Preferably, the thickness of the sheet metal of each sheet metal part 4 is between 0.09 and 0.49 mm (millimeters), specifically 0.24 mm in the exemplary embodiment. The thickness of each adhesive layer 7 is between 2 and 12 pm (micrometers), specifically 5 pm in the exemplary embodiment. This also applies to the electrical steel strip 3 from which the sheet metal part 4 originates. This results in a thickness for each individual sheet metal part 4 on the laminated core 2 in the range of 0.1 to 0.5 mm, specifically 0.25 mm in the exemplary embodiment.

[0048] The sheet metal parts 4 are pushed by the punch 5a of the punching tool 5 into a stacking device 6. In this stacking device 6, the sheet metal parts 4, which have an adhesive layer 7, namely made of hot-melt adhesive lacquer 8a, on at least one of their flat sides 4a, 4b, are stacked one on top of the other. Thus, a single adhesive layer 7 is located between each two consecutive sheet metal parts 4. In the exemplary embodiment—as can also be seen in Fig. 3—the sheet metal parts 4 have this hot-melt adhesive layer 7 on both of their flat sides 4a, 4b. Thus, there are two adhesive layers 7 between each two consecutive sheet metal parts 4.

[0049] All stacked sheet metal parts 4 leave the stacking device 6 as a loose sheet metal stack 2 or are divided into sheet metal stacks 2 upon or after leaving the stacking device 6 - which sheet metal stack 2 with loose sheet metal parts 4 is shown below the stacking device 6 in Fig. 1. The loose sheet metal stack 2 is then subjected to further process steps - namely, it is introduced into a first furnace 9 in order to heat the hot-melt adhesive layers 7 of the stacked sheet metal parts 4 to a first temperature tempi, which is above the glass transition temperature Tg of the hot-melt adhesive 7a and below the caking temperature of the hot-melt adhesive 7a. Associated with the first furnace 9 is a pressing device 10 with a press ram 10a, which exerts a first axial compressive force P1 on the sheet metal stack 2 - i.e. in the axial direction A of the sheet metal stack 2, which direction A runs parallel to the stacking direction 6 of the stacked sheet metal parts 4.The first compressive force P1 is 3 N / mm. 2 (Newtons per square millimeter) and is applied for 30 seconds. This pre-bonds the sheet metal parts 4 to one another over their entire surface to form a sheet stack 2, whereby the adhesive 8 between the sheet metal parts 2 has not yet cured or, in the case of a hot-melt adhesive 8a, has not yet baked. This is because the gel point of the polymer of the hot-melt adhesive 8a has not been reached or exceeded. The gel point is considered to have been reached when, in a dynamic mechanical analysis (DMA) using a plate-on-plate oscillation viscometer according to ISO 6721-10 at 20 °C, the graphs of the storage modulus G' and the loss modulus G" intersect.

[0050] As an alternative to the first furnace 9, it is conceivable—although not shown—that the sheet metal parts 2 are brought to this first temperature in the stacking device 6 before leaving it. This can eliminate the heating step in the first furnace 9, because these sheet metal parts 4 can also be fully pre-bonded to form the sheet metal stack 2. However, the pressing device 10 can be used for setting under the first pressure P1.

[0051] The pre-bonded laminated core 2 is subsequently subjected to a leak test 11. In this step, it is checked whether the cooling channel 2a of the pre-bonded laminated core 2 is leaking. As schematically shown in Fig. 1a, the laminated core 2 is introduced into a vacuum chamber 12. Furthermore, lines 13 are connected in a gas-tight manner to the cooling channel 2a of the laminated core 2. Via this line 13, the cooling channel 2a is flooded with a test gas in the form of a gaseous fluid 14. Any gaseous fluid 14 escaping from the cooling channel 2a can be detected as a leak in the vacuum chamber by a mass spectrometer 15 connected to the vacuum chamber 12.

[0052] For example, with a leak rate in the range of 10' 3 mbar l / s to 10' 4mbar l / s, a measure is taken to achieve the required tightness on the laminated core 2. For this purpose, the pre-bonded laminated core 2 is introduced into a further pressing device 16 with a press ram 16a. In this process step, the adhesive s of the stacked sheet metal parts 4 is placed under a second pressure P2 in the axial direction A of the stacked sheet metal parts 4 in order to achieve the required tightness.

[0053] The second pressure P2 is sufficient to achieve complete bonding of the two adhesive layers 7 to one another, thus eliminating the free areas 16 between the hot-melt adhesive layers 7 and thus an adhesive gap - as can be seen in Fig. 3 in conjunction with Fig. 2. Thus, Fig. 3 clearly shows how the adhesive 8 surrounding the cooling channel 2a is free of these free areas 16. This reproducibly creates a pre-bonded laminated core 2 with a leak-free cooling channel 2a.

[0054] Subsequently, the sheet metal parts 4 are fully bonded together to form a sheet stack 2, or the hot-melt adhesive 7a is converted to the C-state. This final bonding ensures the leak-free state of the sheet stack 2. For this final bonding, the sheet stack 2 is introduced into another oven 17, where the adhesive 8 of the sheet stack 2 is heated to a second temperature temp2, which is greater than or equal to the bonding temperature of the hot-melt adhesive 7a of the hot-melt adhesive layers 7, in order to bond the stacked sheet metal parts together with a sufficiently long bonding time. During this step, a constant pressure can also be exerted on the sheet metal parts, for example, to adjust the stack height of the sheet stack 2. For example, the second temperature temp2 is 200 °C (200 degrees Celsius), the bonding time is 1 minute, with a possible compressive load on the sheet stack 2 of 0.3 N / mm 2 .

[0055] It is also conceivable, although not shown, that before the leak test 11 of the pre-bonded laminated core 2, the core height is recorded using a measuring method and, if the recorded core height falls below the tolerance range, at least one additional sheet metal part 4 is applied to an end face 2b, 2c of the laminated core 2 in order to adapt the core height to a height within the tolerance range of a predetermined target core height.

[0056] As can also be seen in Fig. 1 and Fig. 1a, the laminated core 2 and thus also its adhesive 8 are at the first temperature tempi during the second pressure P2. This further improves the flawless pre-bonding of the sheet metal parts 4. The first temperature tempi lies in the range of 80 to 220 °C, namely 120 °C.

[0057] The pre-bonded laminated core 2 is subjected to a second pressure P2 in a special way. A pressure pulse is exerted on the laminated core 2 by applying a pulse pressure P20 and then releasing the pressure P20. This occurs several times, resulting in a periodic pulse sequence.

[0058] For this purpose, the pressing device 16 loads the laminated core 2 with a second pressure P2 at the level P20 or with the impulse pressure in the range of 0.5 to 20 N / mm 2 , in the example 5 N / mm 2 This application of the second pressure P2 at the level P20 and the release of this second pressure P2 at the level P20 occurs with an equal duration ti and t2, respectively, resulting in a period T in the range of 0.1 to 20 seconds, 2 seconds in the exemplary embodiment. This ensures high reproducibility in the production of laminated cores 2 with liquid-tight cooling channels 2a.

[0059] In order to be able to connect a line 13 to the laminated core 2 in a more reproducible and tight manner, a relief 19 encompassing and adjoining the cooling channel 2a is produced in the adhesive 8 on this end face 2b of the laminated core 2 by embossing, as can be seen in Fig. 4a and 4b.

[0060] To achieve this, an adapter 18, made in particular of stainless steel, is located at the connection end of the line 13, which adapter has an embossed structure, in particular a grid-shaped one, on its front side 18a. By pressing the adapter 18 against the laminated core 2, a relief 19, grid-like in the exemplary embodiment, is created on the adhesive 8, namely hot-melt adhesive lacquer 8a in the exemplary embodiment, specifically on the outer adhesive layer 7 of the sheet metal part 4 on the relevant end face 2b, 2c of the laminated core 2. However, this relief 19 can be created differently and / or before the adapter 18 is connected, or may already exist.

[0061] As can be seen in Figures 4a and 4b, the relief 19 has depressions 20 and relief structures 21 that stand out from these depressions 20.

[0062] In the exemplary embodiment, which differs from the schematic Figures 4a and 4b, the relief structures 21 have a structure height dr of 7 pm and a maximum structure width sbr of 585 pm. The recesses 20 have a maximum recess width kp between two successively arranged relief structures 22 of 278 pm.

[0063] This embossing can be carried out particularly robustly and repeatably if the adhesive 8 has a temperature during embossing that is greater than the glass transition temperature Tg of the adhesive 8. This temperature is preferably the first temperature tempi .

[0064] Advantageously, the stainless steel surface of the adapter 18 also enables a non-destructive detachment of the adapter 18 from the laminated core 2 - for example, when the laminated core 2 is removed from the vacuum chamber 12 after its leak test 11.

[0065] In general, it is noted that "in particular" can be translated into English as "more particularly." A feature preceded by "in particular" is to be considered an optional feature that can be omitted and thus does not constitute a limitation, for example, of the claims. The same applies to "vorzugsweise," translated into English as "preferably."

Claims

P a t e n t a n s p r ü c h e: 1 . Method for bundling sheet metal parts (4) from an electrical strip (3) or sheet to form at least one laminated core (2) with at least one cooling channel (2a), in which the sheet metal parts (4), each having at least one recess (4c) for the cooling channel (2a) and a curable adhesive (8) on at least one of their flat sides (4a, 4b), are stacked on top of one another in such a way that the recesses (4c) form the cooling channel (2a) extending in the laminated core (2), the stacked sheet metal parts (4) are placed under first pressure (P1) in the axial direction (A) of the stacked sheet metal parts (4) and are pre-glued to one another by the curable adhesive (8) to form a laminated core (2), a leak test (11) of the cooling channel (2a) of the pre-glued laminated core (2) is carried out and upon detection of a leak, the stacked sheet metal parts (4) are (A) be placed under second pressure (P2),in order to achieve the required tightness, and the pre-bonded sheet package (2) is finally bonded by curing the curable adhesive (8).

2. Method according to claim 1, characterized in that for the pre-bonding the thermally activatable adhesive (8), in particular hot melt adhesive lacquer (8a), has a first temperature (tempi ), which first temperature (tempi ) is greater than the glass transition temperature (Tg) of the adhesive (8) and less than the activation temperature of the adhesive (8), in particular the caking temperature of the hot melt adhesive lacquer (8a), and for the final bonding the thermally activatable adhesive (8) is heated to a second temperature (temp2), which is greater than or equal to the activation temperature, in particular the caking temperature of the hot melt adhesive lacquer (8a), and thus the sheet metal parts (4) are finally bonded to one another.

3. Method according to claim 1 or 2, characterized in that during the leak test (11) to detect a leak, a gaseous fluid (14), in particular test gas, is introduced into the cooling channel (2a).

4. Method according to claim 3, characterized in that the gaseous fluid (14) comprises helium and / or hydrogen, in particular is a forming gas.

5. Method according to claim 3 or 4, characterized in that in the cooling channel (2a) to be tested for leaks, an overpressure, in particular in the range of 0.1 to 2 bar, and / or outside the cooling channel (2a) to be tested for leaks, a negative pressure acts or acts on the pre-bonded laminated core (2).

6. Method according to one of claims 1 to 5, characterized in that during the leak test (11) the pre-bonded laminated core (2) is introduced into a vacuum chamber (12).

7. Method according to one of claims 1 to 6, characterized in that during the leak test (11) a leak up to a leak rate of 10' 4 mbar l / s, especially in the range of 10' 3 mbar l / s to 10' 4 mbar l / s, is detected.

8. Method according to one of claims 2 to 7, characterized in that the adhesive (8) has the first temperature (tempi) during the second pressurization (P2).

9. Method according to one of claims 1 to 8, characterized in that the second pressurization (P2) comprises at least one, in particular several, pressure pulses (P20).

10. The method according to claim 9, characterized in that the pressure pulse (P20) pressurizes the adhesive (8) with a pulse pressure in the range of 0.5 to 10 N / mm 2 , especially from 2 to 6 N / mm 2 , and / or that the second is under pressure (P2) Setting is carried out with directly consecutive pressure pulses (P20), in particular periodically.

11. The method according to any one of claims 1 to 10, characterized in that the first temperature (tempi ) is in the range from 80 to 220 °C, preferably in the range from 80 to less than 180 °C, in particular in the range from 100 to 150 °C.

12. The method according to any one of claims 1 to 11, characterized in that the second temperature (temp2) is in the range from 180 °C to 250 °C, in particular in the range from 180 °C to 220 °C.

13. Method according to one of claims 1 to 12, characterized in that sheet metal parts (4) are stacked on top of one another, which have an adhesive layer (7), in particular made of hot-melt adhesive varnish (8a), on one of their flat sides (4a, 4b), in particular on both of their flat sides (4a, 4b).

14. Method according to one of claims 1 to 13, characterized in that the thickness of each sheet metal part (4) is between 0.09 and 0.49 mm, in particular 0.09 to 0.29 mm, and / or that the thickness of the adhesive layer (7) of each sheet metal part (4) is between 2 and 12 pm, in particular 4 to 8 pm.

15. Method according to one of claims 1 to 14, characterized in that the stacked sheet metal parts (4) are pre-glued and / or finally glued over their entire surface to form a sheet metal package (2).

16. Method, in particular according to one of claims 1 to 15, characterized in that for the leak test (11) or during the leak test (11) of the cooling channel (2a) on an end face (2b, 2c) of the laminated core (2) a relief (19) is produced in the adhesive (8), in particular hot-melt adhesive lacquer (8a), by embossing, in particular encompassing and / or adjoining the cooling channel (2a).

17. Method according to claim 16, characterized in that the relief (19) has depressions (20) and relief structures (21) standing out from these depressions (20).

18. The method according to claim 17, characterized in that the relief structures (21) have a structure height (dr) of at least 1 pm, in particular at least 2 pm, and / or that the relief structures (17) have a maximum structure width (sbr) of at least 200 pm, in particular at least 500 pm.

19. Method according to claim 17 or 18, characterized in that the depressions (20) have a maximum depression width (kp) between two successively arranged relief structures (22) of at least 50 pm, in particular at least 100 pm.

20. Method according to one of claims 16 to 19, characterized in that the relief (19) forms a pattern with a regular, in particular periodic, structure, in particular a knob pattern, groove pattern, grid pattern, checkerboard pattern, waffle pattern or honeycomb pattern.

21. Method according to one of claims 16 to 20, characterized in that the adhesive has a temperature during embossing which is greater than the glass transition temperature (Tg) of the adhesive (8), and / or that during the leak test an adapter (18) is connected to the cooling channel (2a), which creates the relief (19) by embossing.

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