Joining method and self-piercing joint

Abstract

The invention relates to a method (10) for joining parts (20, 22), in particular metal parts, by means of a joining part (12) deformed during a joining process, comprising the following steps: applying (S2, S3) the joining part (12) with a temperature-stable coating (B1, B2); preheating (S6) at least one of the at least two components (20, 22) in the region of the joining position to a preheating temperature in the range of 90 DEG C to 1400 DEG C, preferably by plasma heating, laser heating, arc heating and / or induction heating, the components (20, 22) being stacked one above the other; and driving the coated joint (12) into the stacked components (20, 22).

Description

Technical Field

[0001] This disclosure relates to a method for joining components, particularly metal components, by means of a joining member that deforms during the joining process, wherein the components are stacked one on top of the other, and the joining member is driven into the stacked components in the joining location region.

[0002] Furthermore, the present invention relates to a joint for a joining method, wherein the joint deforms when used in the aforementioned joining method. A self-piercing rivet (SPR) is an example of such a joint, having a hollow shank. Background Technology

[0003] The self-piercing rivet is driven by the following steps. First, the upper part (e.g., a high-strength steel plate) and the lower part (e.g., an aluminum plate or other steel plate) to be fastened are clamped by a die and the self-piercing rivet held by a fastening tool, or by the nose of the die and the fastening tool. When the self-piercing rivet is punched, the shank of the self-piercing rivet pierces into and penetrates the upper part. When the shank of the self-piercing rivet that has penetrated the upper part enters the lower part and the lower surface of the lower part contacts the bottom of the die, the bottom of the die cavity pushes the lower part back. As a result, the hollow shank of the self-piercing rivet is subjected to a reaction force from the lower part and opens in a ring shape in the lower part without completely penetrating it. The opening of the shank of the self-piercing rivet forms a mechanical interlock and mechanically fastens the upper and lower parts together.

[0004] The number of parts to be fastened can be two, three, or more. For example, in the case of three parts, at least the uppermost part is completely penetrated, while the lowermost part is not completely penetrated. In automotive production, adhesives are typically applied between the parts to be fastened to improve load-bearing capacity, crash stability, corrosion resistance, and performance in terms of noise, vibration, and harshness (NVH).

[0005] Prior art document DE102014000623B4 discloses a self-piercing rivet having a corrosion-resistant layer covering a top layer to allow adjustment of riveting characteristics such as friction and material flow.

[0006] Current self-piercing riveting systems are sometimes unsatisfactory for joining new materials. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide an improved method for joining components and an improved joining member.

[0008] The above objective is achieved by means of a method for joining components, particularly metal components, by means of a joint that deforms during the joining process, the method comprising the steps of: coating the joint with a temperature-stable coating, the coating preferably having temperature stability and a melting temperature above 250°C, and preferably below 1455°C, more preferably below 1400°C, more preferably below 1200°C, and even more preferably below 950°C; preheating at least one of at least two components in the joining location region to a preheating temperature in the range of 90°C to 1400°C, preferably by plasma heating, laser heating, arc heating and / or induction heating, wherein the components are stacked vertically; and driving the coated joint into the stacked components.

[0009] Furthermore, the above objective is achieved by a joint for a joining method, particularly a joining method as defined above, the joint having a head and a rod, wherein the joint is at least partially coated with a temperature-stabilizing coating and is preferably configured to deform during the joining process.

[0010] For joining new materials, it has proven advantageous to combine the preheating of the parts to be joined during the mechanical joining process (i.e., the so-called heat-assisted mechanical joining process). Thus, the parts to be joined are preheated by plasma, laser, induction, electric arc, or similar methods, and then the joiner is driven into the parts to be joined, either in a slightly overlapping or parallel manner. During the joining process, the joining site remains at a high temperature (at least 90°C, up to 1400°C). The temperature reached should be below the melting temperature of the parts.

[0011] Due to the high temperatures at the joint, the coating of existing joints may partially melt during the bonding process, and this, combined with deformation, can lead to cracks in the joints. These cracks may be caused by liquid metal embrittlement (LME) / liquid metal-induced stress corrosion cracking, or localized softening of the joint material, but could also be due to other factors such as localized changes in the coefficient of friction.

[0012] On the other hand, the joint disclosed herein has a temperature-stable coating, which is preferably temperature-stable because its melting temperature is above 250°C, and preferably below 1455°C, more preferably below 1400°C, even more preferably below 1200°C, and even more preferably below 950°C. However, for the higher and highest temperatures within the aforementioned preheating range of 90°C to 1400°C, the coating does not need to be completely temperature-stable. In fact, the preheating step involves preheating the component to a fairly high temperature, but below the component's melting temperature. The preheating step is preferably stopped before the coated joint is driven into the stacked components. Therefore, during the driving step, and preferably even before the driving step begins, the temperature of the component decreases. The cooling can be quite rapid. The preheating range of 90°C to 1400°C is intended to cover the temperature range from the highest (maximum) preheating temperature of the component to the preheating temperature that has been reduced during the driving step. Since the preheating step is preferably stopped before the driving step begins, the coated joint never experiences the highest (maximum) preheating temperature, or only experiences the highest (maximum) preheating temperature very briefly.

[0013] Furthermore, the coating is preferably non-corrosive to the material of the joint, preferably at least in its liquid phase, or non-corrosive in both its solid and liquid phases. Additionally, the coating preferably exhibits deformation stability and preferably has an adjusted or optimized coefficient of friction. An optimized coefficient of friction can be adjusted by using, for example, a topcoat incorporating a lubricant.

[0014] The coating is preferably applied by an alkaline process, such as electroplating, or by immersion in a bath, or by a chemical method. Other coating processes may also be used. The joint is preferably made of a single metallic material, particularly steel.

[0015] The joining components can be directly stacked, preferably stacked without any gaps between them. However, it is more preferable that the components are stacked vertically with an adhesive provided between them.

[0016] During preheating, at least one of the two components is heated, with heat typically conducted to the other component and / or the aforementioned adhesive. Generally, the uppermost component in the stack is preheated in the mating region. However, in other embodiments, heat may also be applied to the lowermost component in the stack during the preheating step. If heat is applied to the lowermost component while the mating member is driven into the stack from above (first into the uppermost component), the mating member will experience higher temperatures at a later stage, potentially resulting in greater deformation in its lower (deeper) portion. On the other hand, if the preheating step is applied to the same component into which the mating member is driven, the mating member will experience higher temperatures at an earlier stage, but with less deformation in its upper portion.

[0017] The component is preferably a sheet material, especially a metal sheet or plate, but it can also be a molded part, a casting, or an extruded profile.

[0018] Preferably, the joints are not preheated before the joining process is carried out, but are provided at room temperature. It should be understood that the joints will receive heat from the preheated components (one or more) during the joining process.

[0019] The coated joint is driven into the stacked components in the joint location area.

[0020] To date, there has been no evidence of combining deformable joints with temperature-stable coatings for use in heat-assisted mechanical bonding processes.

[0021] The coating described above is preferably a multilayer composite coating system, but it can also be a thermally stable single-layer system with added anti-friction agents. Additionally, a passivation layer may be further provided.

[0022] Preferably, the coating is provided such that the coating in the head area does not melt when the rivet is inserted, thereby providing improved corrosion resistance. Preferably, the coating on the shank also does not melt during the joining process.

[0023] In particular, the disclosed joining method allows the joints to remain crack-free during riveting in a heat-assisted mechanical joining process. On the other hand, prior art rivets with zinc-tin coatings can generate a significant number of cracks in such heat-overlay processes. Needless to say, such cracking can also be avoided by adjusting the geometry or material of the rivet, but such changes would lead to other disadvantages, such as increased costs, reduced application range, or the need for greater joining forces.

[0024] Therefore, this disclosure fully achieves the above objectives.

[0025] In a preferred embodiment, the preheating step includes applying heat to one of the uppermost or lowermost components to a maximum preheating temperature that is 30% above the melting temperature of the respective component.

[0026] Using this maximum preheating temperature, subsequent drive steps can be performed with exceptional efficiency and without failure.

[0027] Preferably, the maximum preheating temperature is 35% higher than the melting temperature of the corresponding component, more preferably higher than 40%, even more preferably higher than 75%, particularly higher than 80%, and in the preferred embodiment higher than 85%. Most preferably, the maximum preheating temperature is 88% higher than the melting temperature of the corresponding component.

[0028] Furthermore, it is preferable that the maximum preheating temperature is 98% lower than the melting temperature of the corresponding component, particularly 96%, and preferably 94%.

[0029] In a preferred embodiment, the coating comprises a base coat with high thermal stability and a friction control coating applied to the base coat.

[0030] Such multilayer coating systems have proven particularly advantageous in heat-assisted mechanical bonding processes. The friction control coating controls the friction value while simultaneously improving corrosion resistance, chemical acid resistance, and acting as another insulating layer. Applying the friction control coating onto the base coat involves applying the friction control coating over a passivation layer provided on top of the base coat.

[0031] Preferably, the base coating is made of a zinc-based coating, a nickel-based coating, or a copper-based coating, and in particular, is made of at least one material selected from the group consisting of: zinc, zinc alloys, zinc-nickel alloys, nickel, nickel alloys, nickel-phosphorus alloys, nickel-tungsten alloys, copper, copper alloys, copper + nickel, zinc flake, etc.

[0032] Such coating systems exhibit high abrasion resistance and a melting temperature above 250°C. Preferably, the melting temperature of the coating is above 400°C (e.g., for zinc coatings), particularly above 700°C. The melting temperature can be below 1455°C, more preferably below 1400°C, even more preferably below 1200°C, and even more preferably below 950°C. Furthermore, the above-described coating systems provide excellent corrosion resistance.

[0033] Furthermore, it is preferred that the friction control coating is an organic coating, particularly an aluminum-containing organic coating. Particularly preferred is that the friction control coating is made of at least one material selected from the group consisting of: Magni B18, Torque 'N'Tension, Microgleit DF 921, etc.

[0034] Mega-Li B18 is a common topcoat, preferably applied via dip coating, spin coating, or spray coating, followed by drying / firing at, for example, 190°C to 230°C for 15 to 25 minutes. Other coating materials manufactured by the other manufacturers listed above are also common.

[0035] Furthermore, it is preferred that the coefficient of friction of the friction control coating is in the range of 0.07 to 0.19, particularly in the range of 0.08 to 0.18, preferably in the range of 0.12 to 0.18 or in the range of 0.08 to 0.13.

[0036] On the other hand, it is preferred that the thickness of the base coating is in the range of 3µm to 15µm, more preferably in the range of 3µm to 12µm, and particularly in the range of 5µm to 10µm.

[0037] The preferred base coating is: (i) a zinc-based coating, preferably containing 8% to 20% nickel, particularly 12% to 16% nickel, with the remainder preferably zinc; or (ii) a nickel-based coating, preferably containing 1% to 15% phosphorus, or preferably containing 30% to 35% tungsten, with the remainder preferably nickel; or (iii) a copper-based coating.

[0038] Furthermore, it is particularly preferred to provide a passivation layer on the base layer before applying the friction control layer.

[0039] The thickness of the passivation layer provided on top of the base coating by the passivation process is preferably in the range of 50 nm to 400 nm.

[0040] The passivation process is preferably a chemical process used to reduce the reactivity of the layer and delay the formation of white rust or corrosion of the undercoat.

[0041] Furthermore, it is preferable to bake the joint as a post-heat treatment after the passivation process, for example, to eliminate hydrogen embrittlement. The baking treatment may begin up to 4 hours after the passivation process, at a temperature of, for example, 190°C to 230°C, and may be stopped after at least 6 hours and up to 10 hours.

[0042] Furthermore, it is preferred that the thickness of the friction control coating is in the range of 1 µm to 6 µm, particularly in the range of 2 µm to 4 µm.

[0043] As described above, the coating of the joint is preferably a multilayer coating as described above.

[0044] In another preferred embodiment, the coating is a single-layer system, preferably including a friction-reducing component as an additive.

[0045] Here, the coating system can be a zinc sheet coating with added friction modifiers / components. However, a single-layer system can also be achieved without any additives, and can be a pure nickel coating.

[0046] Furthermore, the connecting parts are preferably stamped rivets, especially self-piercing rivets (SPR).

[0047] Furthermore, it is preferred that the Vickers hardness of the joint is in the range of 220±30 HV10 to 590±30 HV10, particularly in the range of 380±30 HV10 to 510±30 HV10.

[0048] Typically, joints can have all the typical hardness levels, from below H0 to H6, and especially from H2 to H4.

[0049] Typically, the step of driving the coated bonding material into the stacked components can begin before the preheating step is finished.

[0050] In a preferred embodiment, the step of driving the coated bonding member into the stacked components begins at least 0.05 seconds after the end of the preheating step, preferably within the range of 0.05 to 0.8 seconds after the end of the preheating step.

[0051] The start of the driving step should be understood as the moment when the connector contacts the top of the stacked components and begins to penetrate the stack.

[0052] In a preferred embodiment, the driving step begins at least 0.1 seconds after the end of the preheating step, preferably 0.15 seconds, and particularly at least 0.2 seconds.

[0053] Furthermore, the driving step is preferably started no later than 1.5 seconds after the end of the preheating step, preferably no later than 1 second after the end of the preheating step, and especially no later than 0.8 seconds after the end of the preheating step.

[0054] At least two of the stacked components preferably include a first component, which may be the uppermost component, made of steel, particularly high-strength steel with a strength (especially ultimate tensile strength) in the range of 1000 MPa to 2100 MPa. More specifically, the first component faces the preheating device. In other words, the first component is closer to the preheating device than another (or other) component. The high-strength steel preferably has a constant thickness in the range of 0.8 mm to 3.0 mm. Furthermore, the steel is preferably made of one of 22MnB5 steel and DP1000 duplex steel. 22MnB5 steel preferably has a constant thickness in the range of 1.0 mm to 2.3 mm. DP1000 duplex steel preferably has a constant thickness in the range of 1.0 mm to 3.0 mm, particularly a constant thickness in the range of 1.2 mm to 3.0 mm.

[0055] In another preferred embodiment, at least two components include a second component, which may be the lowest component, made of an aluminum alloy, particularly AlMg. 4<x<5 Mn 0.3<y<0.5 and AlMg 2<x<5 One of the following. The aluminum alloy preferably has a constant thickness in the range of 1 mm to 4 mm. The first specific aluminum alloy mentioned above preferably has a constant thickness in the range of 1 mm to 3 mm. The second aluminum alloy mentioned above preferably has a constant thickness in the range of 2 mm to 4 mm.

[0056] The positions of the upper component made of steel and the lower component made of aluminum alloy can be interchanged, so that the joint is driven from the surface of the aluminum alloy component into the stack.

[0057] In addition, the preferred preheating step includes heating the mating area to the maximum preheating temperature, and then stopping or reducing the heating.

[0058] As described above, the maximum preheating temperature is preferably 30% higher than the melting temperature of the component being preheated, and preferably 98% lower than its melting temperature.

[0059] Furthermore, in a preferred embodiment, the step of driving the coated bonding element into the stacked components begins when the temperature in the bonding location region is below but above the maximum preheating temperature by 30%. Preferably, the driving step begins when the temperature in the bonding location region is above the maximum preheating temperature by 40%, and more preferably above 50%.

[0060] Similarly, the start time of the driving step coincides with the moment when the connector contacts the stack and begins to penetrate the stack.

[0061] Furthermore, the step of providing the coated bonding material to the stacked components preferably ends when the temperature in the bonding area is above the ambient temperature (typically above 20°C) and below 85% of the maximum preheating temperature.

[0062] In other words, the driving step ends long before the engagement area has completely cooled to ambient temperature. Alternatively, it is preferable that the temperature has already dropped to a certain level.

[0063] Preferably, the driving step ends when the temperature in the engagement area is below 60% of the maximum preheating temperature, more preferably below 40% of the maximum preheating temperature, and especially below 30% of the maximum preheating temperature.

[0064] Furthermore, the driving step preferably ends when the temperature in the engagement area is 5% higher than the maximum preheating temperature, and more preferably 10% higher than the maximum preheating temperature.

[0065] The end of the drive cycle is defined as the moment when the joint reaches its final position within the stack (e.g., the head rests on the upper surface) such that the tool used for the riveting process can be withdrawn. It should be understood that a complete drive cycle may only end after the tool (punch) and optionally the nose / retainer return to their respective end positions, but the above definition still applies.

[0066] The aforementioned temperature limits help to establish a bonding process in which heat continuously decreases during the driving step, and the temperature of the bonding location region is preferably quite high at the beginning of the driving step and preferably significantly reduced at the end of the driving step.

[0067] For self-piercing rivets used in the joining method, the coating is preferably applied to their entire surface, although typically the coating may only be applied to certain areas of the surface. In particular, it is preferable that at least the outer periphery of the rivet shank and the top surface of the head are coated, because the coefficient of friction in the rivet shank region is particularly relevant, and the top surface of the head needs to be coated to provide the necessary corrosion resistance. Preferably, the lower radius of the head and / or the annular cutting edge of the shank and / or the annular radial end face of the shank are also coated.

[0068] Typically, the coating on the joint may wear down partially during the drive process. The degree of wear may vary depending on the temperature it is subjected to.

[0069] It should be understood that the foregoing features and the features described below can be used not only in the various combinations given, but also in different combinations or individually, without departing from the scope of the invention. Attached Figure Description

[0070] Other features and advantages of the invention can be appreciated from the following description of preferred embodiments with reference to the accompanying drawings. In the drawings:

[0071] Figure 1 This is a schematic flowchart of a method for joining components;

[0072] Figure 2 This is a schematic cross-sectional view of a self-piercing rivet;

[0073] Figure 2a It shows Figure 2 Details IIa;

[0074] Figure 3a It is a cross-sectional view of the joint produced by the disclosed method of using self-piercing rivet joint components;

[0075] Figure 3b yes Figure 3a Detailed images;

[0076] Figure 4a Is with Figure 3a Cross-sectional view of the comparative example;

[0077] Figure 4b yes Figure 4a Detailed images;

[0078] Figure 5a Is with Figure 3a A cross-sectional view of another comparative example;

[0079] Figure 5b yes Figure 5a Detailed images;

[0080] Figure 6It is a graph showing the temperature change over time, illustrating the progress of the bonding method disclosed herein;

[0081] Figure 7 This is a graph showing the temperature change over time during the preheating process, illustrating the temperatures of the upper, lower, and middle sections of the component stack.

[0082] Figure 8 A bottom view is shown of the self-piercing joint after riveting in a material stack using a joining method involving preheating and the use of an uncoated joint; and

[0083] Figure 9 A bottom view is shown after the self-piercing joint is riveted in a material stack using the joining method of this disclosure. Detailed Implementation

[0084] exist Figure 1 The method of joining the components is shown in schematic flowchart 10.

[0085] Flowchart 10 includes step S1, in which at least two components are provided. These components are preferably metal components, particularly sheet metal components.

[0086] The first upper component is a metal plate, preferably a steel plate, aluminum plate or magnesium plate, for example made of hot-formed steel Usibor 2000.

[0087] The second component is a metal sheet, which can be made of aluminum material EN AW-5182.

[0088] In step S2, the two components are inserted into a joining tool, particularly a self-piercing riveting tool (or the joining tool is moved to the components), wherein the two components are stacked one on top of the other, and preferably an adhesive is provided between the two components.

[0089] In step S3, at least one component is heated to a temperature ranging from 90°C to 1400°C in the joining area, preferably by plasma heating, laser heating, arc heating, and / or induction heating. Preheating is performed with the components stacked vertically. The preheating step includes applying heat to one of the uppermost and lowermost components to a maximum preheating temperature, which is preferably 30% higher than the melting temperature of the respective component.

[0090] Generally, the temperature of the components to be joined is related to the temperature measured in the middle of the component stack. Therefore, the temperature of the heated surface may be higher than the aforementioned temperature. The reason for defining the temperature this way is that in some cases, especially when the surface is heated by plasma, the surface temperature cannot be measured directly. Measurements can also be taken directly below the heated area of ​​the component stack.

[0091] Joining tools typically have a lower die and a stamping tool for driving the joiner (such as an SPR) into the stack of parts. The tool usually has a nose (retainer). The part stack is typically arranged in the tool with its joining area above the die and below the nose, and then, usually before the joining process begins, the part stack is clamped between the nose and the die. The clamping step can be performed before or after the preheating step.

[0092] On the other hand, in step S4, a joint, such as a self-piercing rivet, is provided. In step S5, the joint is coated. Specifically, the joint is first coated with a base coating, which is preferably passivated, and then coated with a friction-controlling coating.

[0093] As an alternative, the joint can be coated with an improved single-layer coating in step S5.

[0094] It should be understood that the bonding element is not coated simultaneously with the stacked components. Instead, the bonding element is provided so that steps S4 and S5 are performed before the bonding process and before steps S1 to S3.

[0095] In step S6, the coated joint is inserted into the jointing tool.

[0096] In step S7, the coated joint is driven into the preheated stacked components to produce a self-piercing rivet joint.

[0097] The joint is preferably a self-piercing rivet, but it can also be any other type of joint that deforms during the joining process. Self-piercing rivets that can be used in the joining method 10 described above include... Figure 2 , Figure 2a As shown.

[0098] The self-piercing rivet (SPR) 12 has a head 14 and a hollow shank 16. The hollow shank 16 has an end opposite to the head 14, which forms an annular cutting edge 18.

[0099] The material for self-piercing rivets can be, for example, 37MnB4. The materials for the joints typically have a Vickers hardness ranging from 220±30 HV10 to 590±30 HV10, particularly from 380±30 HV10 to 510±30 HV10. Hardness can range from below H0 to H6.

[0100] like Figure 2 Self-piercing rivets, such as rivet 12, can be available in a variety of different sizes depending on the application. Therefore, Figure 2 The following dimensional examples of the self-piercing rivet 12 shown are considered exemplary only and are not intended to limit the rivet to these dimensions.

[0101] The axial length L1 of the self-piercing rivet 12 is, for example, 5.0 mm. The outer diameter D1 of the head 14 is, for example, 5.5 mm or 7.75 mm.

[0102] The outer diameter D2 of the rod 16 is, for example, 3.35 mm, 5.3 mm, or 5.5 mm.

[0103] The inner diameter D3 of the rod 16 is smaller than the outer diameter D2.

[0104] The axial length L2 of the head 14 is, for example, 1.0 mm. The head has a crown with a constant outer diameter (diameter D1) and the axial crown length L3 of the crown is 0.2 mm.

[0105] The lower side of the head decreases from the outer diameter D1 to the outer diameter D2 by a radius R1 (e.g., 1.8 mm).

[0106] The shank 16 has an inner chamfer in the region of its annular cutting edge 18, and the inner chamfer is designed to have a second radius R2, for example, 1.3 mm.

[0107] The opening angle α of the inner chamfer of the rod is preferably 90°.

[0108] If the self-piercing rivet 12 is driven into the stacked components, its annular cutting edge 18 pierces the upper component, and during further engagement, the shank completely penetrates the upper component. As the shank enters the lower component, the lower surface of the lower component contacts the bottom of the die to generate a reaction force. As a result, the hollow shank of the rivet opens in annular shape within the lower component without penetrating it.

[0109] The basic principle of any self-piercing rivet is the same, but as mentioned above, its dimensions may vary. The joint does not necessarily have to have a prominent head; instead, its outer diameter can be substantially constant along its length. Furthermore, the joint does not necessarily need to completely penetrate the upper component.

[0110] Typically, existing rivets used in such processes are coated, for example, with a tin-zinc coating. Such a coating is usually sufficient when using rivets in conventional self-piercing riveting processes.

[0111] In addition, existing rivets are typically supplied with lubricant before being used in the joining process.

[0112] Another typical existing technology coating for this type of rivet is ternary alloy, which is usually a combination of aluminum, tin and zinc.

[0113] On the other hand, according to this disclosure, the rivet 12 is provided with a temperature-stabilized coating, which is preferably as follows: Figure 2a The multi-layer coating shown.

[0114] Specifically, rivet 12 is first coated with a base coating B1, which has high thermal stability and a melting temperature above 250°C. Subsequently, rivet 12 is coated with a friction control coating B2, which provides an optimized coefficient of friction for the stack, lower than that of rivets without the friction control coating B2.

[0115] The base coating B1 is preferably made of a zinc-based coating, a nickel-based coating, or a copper-based coating, and particularly of at least one material selected from the group consisting of: zinc, zinc alloys, zinc-nickel alloys, nickel, nickel alloys, nickel-phosphorus alloys, nickel-tungsten alloys, copper, copper alloys, copper-nickel alloys, zinc flakes, etc. The base coating is preferably: (i) a zinc-based coating, preferably containing 8% to 20% nickel, particularly 12% to 16% nickel; or (ii) a nickel-based coating, preferably containing 1% to 15% phosphorus, or preferably containing 30% to 35% tungsten; or (iii) a copper-based coating.

[0116] When the base coat primarily comprises nickel, it is preferable to apply a thin copper layer as a primer / adhesive to the rivet 12 before applying the base coat. In this case, the base coat is copper + nickel.

[0117] The thickness of the base coating B1 is preferably in the range of 3 µm to 12 µm, particularly in the range of 5 µm to 10 µm. The base coating B1 preferably comprises zinc (80% to 92%) and 8% to 20% nickel, particularly zinc (84% to 90%) and 10% to 16% nickel. The melting temperature of such zinc-nickel alloy-based coatings is typically between 750 and 800 °C.

[0118] On the other hand, the friction control coating B2 is preferably an organic coating, particularly an aluminum-containing organic coating. Preferably, the friction control coating B2 is made of at least one material selected from the group consisting of: Mega-Force B18, Torque 'N'Tension, Motel DF 921, etc.

[0119] Magni B18 is a topcoat manufactured by Weld Magni Group, Inc. Torque 'N'Tension is a topcoat manufactured by MacDermid Enthone Industrial Solutions. Microgleit DF 921 is a micro polyethylene dry lubricant manufactured by Microgleit Tribology Solutions.

[0120] Preferably, the base coat B1 is passivated to produce a passivation layer P before the friction control coating B2 is applied.

[0121] Passivation is preferably chemical passivation using a passivation solution.

[0122] Passivation solutions suitable for this purpose consist primarily of complexed chromium(III) ions, as well as cobalt, nitrates, and complexed ions (such as fluorides or organic acids).

[0123] After the passivation process, it is preferable to bake the rivet 12 (a post-heat treatment to eliminate hydrogen de-embrittlement).

[0124] As described above, the coefficient of friction of the friction control coating is preferably in the range of 0.07 to 0.19, particularly in the range of 0.08 to 0.18, and more preferably in the range of 0.08 to 0.13.

[0125] Furthermore, the thickness of the friction control coating is preferably in the range of 1 µm to 6 µm, particularly in the range of 2 µm to 4 µm.

[0126] Figure 3a and Figure 3b An example of a joint produced using rivet 12 made of 37MnB4 with a hardness of H4 is shown.

[0127] Furthermore, the lower metal component is made of AlMg4.5Mn0.4 with a thickness of 2 mm. The upper component 20 is made of Usibor 2000 (Cr1900T-MB-DS, according to the draft VDA239-500 standard of May 2021). The bonding strength is in the range of 55 kN to 60 kN.

[0128] according to Figure 3a Rivet 12 pierced the upper component 20 and entered the lower component 22, but did not pierce the lower component 22. (Example) Figure 3b As shown in the details, the shank 16 of rivet 12 is deformed but without any cracks.

[0129] The crack-free riveting of rivet 12 can be attributed to the coating of rivet 12, in this case, a zinc-nickel alloy undercoat B1, a passivation layer P as described above, and a Magnet B18 topcoat incorporating lubricant.

[0130] on the other hand, Figure 4a and Figure 4b A comparative example is shown in which the same parts 20 and 22 are used, but the rivet 12' is coated with a ternary alloy.

[0131] like Figure 4b As shown, crack CR has been generated in the rod 16.

[0132] Figure 5a and Figure 5b Another comparative example is shown.

[0133] Here, components 20 and 22 are... Figure 3a , 3b The same as in the example. The 12'' rivet is coated with a mechanical SnZn coating and lubricant. (Example) Figure 5b As shown, in this case, crack CR may also appear in the rod 16.

[0134] Therefore, it has been demonstrated that if self-piercing rivets are used in heat-assisted mechanical joining processes, where the joining location is preheated to a temperature in the range of 90°C to 1400°C, preferably to a maximum preheating temperature 30% higher than the melting temperature of the corresponding component, then as Figure 2a The coating shown and described above is superior to the classic coating of self-piercing rivets.

[0135] As Figure 2a An alternative to the coating shown (which mainly consists of three layers of B1, P, and B2) can also be a single-layer system containing friction-reducing components as additives applied to rivet 12.

[0136] For example, a single-layer system could be a zinc sheet coating containing friction-reducing components.

[0137] An example of such a single-layer system is the GEOMET 500 coating produced by NOF METAL COATINGS EUROPE, which provides a controlled friction value between 0.12 and 0.18.

[0138] Another example of such a single-layer system is the DELTA-Protekt KL 105 coating produced by Dörken Coatings. This coating also provides a specified coefficient of friction range between 0.12 and 0.18.

[0139] Figure 6 A graph showing the temperature change over time in the bonding method of this disclosure is shown.

[0140] The process begins with preheating at least one of the at least two components forming the component stack, in this example shortly after time 0.0 seconds, until the maximum preheating temperature above 900°C is reached after time 2.0 seconds. At this point, the preheating step stops. The step of driving the coated bonding agent into the stacked components begins after a certain delay, which is at least 0.05 seconds and no more than 1.5 seconds. In this example, the delay is approximately 0.3 seconds. After the delay, the preheating temperature has dropped by more than 10%, in this example to approximately 800°C.

[0141] Preferably, the time delay between the preheating stop step and the drive start step depends on the measured temperature. For example, once the maximum preheating temperature is reached, the stamping step of moving the joint from its base position (the position where the joint is away from the component stack) to its contact position with the component stack (drive start) can begin immediately. Moving the joint from its base position to the drive start position may introduce or contribute to the time delay. In another example, the drive step can begin at a desired drive temperature, which can be calculated as follows:

[0142] Drive step start temperature = (0.95 to 0.8) maximum preheating temperature

[0143] When the connector is driven into the component stack (in) Figure 6 The temperature is measured (presumably starting at a time in the range of approximately 2.2 to 2.5 seconds) preferably in the middle portion of the component stack. Figure 6 (As shown) or measure the temperature on its underside. (As mentioned before, direct measurement, especially when using plasma preheating, is not a practically feasible method.)

[0144] Figure 6 The diagram is based on an exemplary embodiment of joining a component stack consisting of a 2.0 mm thick EN AW-5182 lower plate and a 1.5 mm thick 22MnB5 + AS(PH) upper plate. The upper surface of the upper plate is preheated in the joining area by a plasma heating process. The preheating step includes heating to the maximum preheating temperature (using a plasma heating device) for approximately 1.7 seconds, resulting in a maximum temperature of approximately 960°C reached in 2.0 seconds.

[0145] It is important to note that the temperature is not measured on the upper surface of the upper plate. Instead, it is measured in the middle of the component stack, between the upper and lower plates. However, because preheating using a plasma heating device is applied to the upper surface of the upper plate, the maximum preheating temperature on the upper surface is higher than that of the upper plate. Figure 6 The temperatures shown. The upper surface temperature is higher than... Figure 6 The indicated temperatures can be estimated. This estimation can be used to avoid heating to a certain measurement temperature that would cause the upper surface temperature to exceed the melting temperature of the component. For example, the 960°C mentioned above corresponds to an upper surface temperature that is above 1000°C but still below the melting temperature of the component. It should be understood that due to factors such as ambient temperature and plate thickness, the temperature of the upper plate surface (or the plate surface closest to the preheating device) may drop faster than the temperature inside the plate.

[0146] Figure 7 The temperature comparison of temperature profiles measured at different locations in the temperature stack is shown, where the upper plate is 1.8 mm thick DP1000 duplex steel and the lower plate is 3.0 mm thick AlMg3.

[0147] The highest temperature on the underside of the upper plate (i.e., between the two plates) is 550°C in this example. This is shown at point A.

[0148] On the other hand, the measurement on the lower side of the lower plate is shown at point C. Here, the highest temperature is approximately 120°C. Curve B shows the measurement results in the middle part of the lower plate (measured along the thickness direction), where the highest temperature is approximately 150°C.

[0149] It can be seen that the temperature of the heated surface of the stack can be derived from measurements taken at the bottom or middle of the component stack. This is related to the calculation of the maximum preheating temperature, which should in any case be lower than the melting temperature of the component to which heat is applied. As mentioned above, the feature that the maximum preheating temperature is preferably lower than 98%, preferably lower than 95%, of the melting temperature of the material of the heated component should be understood in the following way: the selection of the maximum preheating temperature ensures that the highest temperature of the component (which may be the temperature of the surface to which heat is applied) is lower than 98%, preferably lower than 95%, of the melting temperature of the material.

[0150] Figure 8 Three different joints produced by a joining method corresponding to the joining method of this disclosure are shown; however, the joints are coated with a standard coating. The stack comprises a 1.5 mm thick top plate made of CR340LA and a 2.0 mm thick bottom plate made of EN AW-5182 aluminum alloy.

[0151] In each case, measurements were taken with an impact force ranging from 44.9 kN to 48.89 kN, using 5.3 × 5.5 C-type rivets with a hardness of H4 and coated with a standard SnZn coating, at three different maximum preheating temperatures of 1000°C, 640°C, and 408°C.

[0152] In each case, cracks were visible, and the number of cracks decreased as the temperature decreased. However, when heated to the maximum preheating temperature of approximately 400°C, cracks were still present.

[0153] on the other hand, Figure 9 A joint produced by the method of this disclosure is shown. No cracks were observed.

[0154] The upper and lower plates are made of the same material. The rivets are 5.3×5.5 C-type rivets with a hardness of H4, and are driven into the stack under an impact force of 46.08 kN.

[0155] The rivet is coated with a zinc-nickel alloy base coat of 5 µm to 10 µm thickness using an alkaline process, wherein the alloy contains 12% to 16% nickel.

[0156] The zinc-nickel alloy undercoat was passivated and tempered, and then a Mega-Cali B18 topcoat with a thickness of 2 µm to 4 µm was applied.

[0157] The maximum preheating temperature is 800°C, which demonstrates that the application of coatings as proposed in this disclosure allows for preheating of component stacks to higher temperatures without cracking, thereby improving overall bonding performance.

[0158] Figure Labels

[0159] 10. Joining Method

[0160] 12 Connecting parts

[0161] 14 heads

[0162] 16 Hollow rod section

[0163] 18. Circular cutting edge

[0164] 20 parts

[0165] 22 Lower Components

[0166] S1-S7 Method Steps

[0167] B1 base coat

[0168] B2 Friction Control Coating

[0169] P passivation layer

[0170] L1 Joint Length

[0171] L2 head length

[0172] L3 crown length

[0173] D1 Head diameter

[0174] D2 Outer diameter of the rod

[0175] D3 rod inner diameter

[0176] R1 Head underside radius

[0177] R2 inner chamfer radius of the rod

[0178] α Chamfer Angle

[0179] CR rod crack

Claims

1. A method (10) for joining components (20, 22), particularly metal components, by means of a joining member (12) that deforms during the joining process, comprising the following steps: - Apply a temperature-stable coating (B1, B2) to the joint (S5) (12); - Preheat (S3) at least one of the at least two components (20, 22) in the joint area to a preheating temperature in the range of 90°C to 1400°C, preferably by plasma heating, laser heating, arc heating and / or induction heating, wherein the components (20, 22) are stacked vertically; as well as - Drive (S7) the coated bonding member (12) into the stacked components (20, 22).

2. The method of claim 1, wherein the preheating step comprises applying heat to one of the uppermost or lowermost components to a maximum preheating temperature, the maximum preheating temperature being 30% above the melting temperature of the respective component.

3. The method according to claim 1 or 2, wherein the coating comprises a base coating (B1) having high thermal stability and a friction control coating (B2) applied to the base coating.

4. The method of claim 3, wherein the base coating (B1) is made of a zinc-based coating, a nickel-based coating, or a copper-based coating, and particularly of at least one material selected from the group consisting of: Zinc, zinc alloys, zinc-nickel alloys, nickel, nickel alloys, nickel-phosphorus alloys, nickel-tungsten alloys, copper, copper alloys, copper-nickel alloys, zinc sheets, etc.

5. The method according to claim 3 or 4, wherein the friction control coating (B2) is an organic coating, particularly an aluminum-containing organic coating, and preferably made of at least one material selected from the group consisting of: Mega-Force B18, Torque 'N'Tension, Motel DF 921, etc.

6. The method according to any one of claims 3 to 5, wherein the coefficient of friction of the friction control coating (B2) is in the range of 0.07 to 0.19, particularly in the range of 0.08 to 0.18, and preferably in the range of 0.12 to 0.18 or in the range of 0.08 to 0.

13.

7. The method according to any one of claims 3 to 6, wherein the thickness of the base coating (B1) is in the range of 3 µm to 15 µm, preferably in the range of 3 µm to 12 µm, particularly in the range of 5 µm to 10 µm.

8. The method according to any one of claims 3 to 7, wherein the undercoat is preferably: (i) a zinc-based coating, preferably containing 8% to 20% nickel, particularly 12% to 16% nickel; or (ii) a nickel-based coating, preferably containing 1% to 15% phosphorus or preferably containing 30% to 35% tungsten; or (iii) a copper-based coating.

9. The method according to any one of claims 3 to 8, wherein the base coating (B1) is passivated and / or baked before the friction control coating (B2) is applied.

10. The method according to any one of claims 3 to 9, wherein the thickness of the friction control coating (B2) is in the range of 1 µm to 6 µm, particularly in the range of 2 µm to 4 µm.

11. The method according to any one of claims 3 to 10, wherein the thickness of the passivation layer provided on top of the base coating (B1) by a passivation process is in the range of 50 nm to 400 nm.

12. The method of claim 1, wherein the coating is a single-layer system, preferably comprising a friction-reducing component as an additive.

13. The method according to any one of claims 1 to 12, wherein the joining member (12) is a stamped rivet, particularly a self-piercing rivet.

14. The method according to any one of claims 1 to 13, wherein the Vickers hardness of the joint (12) is in the range of 220±30 HV10 to 590±30 HV10, particularly in the range of 380±30 HV10 to 510±30 HV10.

15. The method according to any one of claims 1 to 14, wherein - The step of driving the coated bonding member (12) into the stacked components begins at least 0.05 seconds after the preheating step ends.

16. The method according to any one of claims 1 to 15, wherein the at least two components include a first component made of steel, particularly steel with a strength in the range of 1000 MPa to 2100 MPa, and preferably made of one of 22MnB5 steel and DP1000 duplex steel.

17. The method according to any one of claims 1 to 16, wherein the at least two components include a second component made of an aluminum alloy, particularly AlMg. 4<x<5 Mn 0.3<y<0.5 and AlMg 2<x<5 One of them.

18. The method according to any one of claims 1 to 17, wherein the preheating step comprises heating the mating location region to a maximum preheating temperature and then stopping or reducing the heating.

19. The method of claim 18, wherein the step of driving the coated bonding member (12) into the stacked components begins when the temperature in the bonding location region is below the maximum preheating temperature and above 30% of the maximum preheating temperature.

20. The method according to claim 18 or 19, wherein the step of driving the coated bonding member (12) into the stacked components ends when the temperature in the bonding location region is above the ambient temperature and below 85% of the maximum preheating temperature.

21. The application of a joint (12) having a coating (B1, B2) in a thermally stacked mechanical joining process, particularly in the joining method (10) according to any one of claims 1 to 20, wherein the coating provides high thermal stability and an optimized coefficient of friction.

22. A self-piercing joint (12) for a joining method, particularly a joining method (10) according to any one of claims 1 to 20, wherein the self-piercing joint (12) is at least partially coated with a thermally stable coating.

23. The self-piercing joint according to claim 22, wherein the coating comprises a base coating (B1) having high thermal stability, and a friction control coating (B2) applied to the base coating (B1).

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