DE102015118058A1 - New joining technology for mixed connections - Google Patents

Abstract

The invention relates to a novel joining method for joining metallic and non-metallic joining partners via a CMT pin method, wherein the pins are pushed by the non-metallic joining partner. The invention also relates to a composite composite produced by the joining process.

Description

Background of the invention

In the prior art joint connections between metallic and non-metallic materials are known. The aim here is always to achieve a particularly high connection strength.

The disadvantage is that in joining processes for the joining of metallic and non-metallic joining partners (especially Kunststofffügepartnern) from the prior art, the fibers are partially destroyed in the joining area. Another disadvantage is that only occasional or discrete connections along the joint zone can be produced. The transferable loads are thus achieved only in certain load directions. The bond strengths are often not high enough. In addition, the process times in joining methods of the prior art are disadvantageously long.

In the prior art, the connections between metallic and non-metallic materials are often made by gluing. However, the process times of this process are particularly long and therefore disadvantageous for many industries. The achievable bond strengths are low or a large overlap length must be selected in order to achieve a satisfactory bond strength.

In the DE 10 2013 211 580 a method for thermo-mechanical forming is described. Here, the local penetration of the joint by means of dome is revealed. This creates a kind of draft, which then turns around the joining point on the opposite side. The remote dome leaves a hole in the component, which affects the connection stiffness. In addition, moderate heat is generated in the component.

In addition, methods using CMT (Cold Metal Transfer) pin technology for joining metallic materials and plastic are already known in the prior art. However, this method still has some disadvantages. One solution is, for example, the attachment of not yet impregnated in the plastic fiber fabric. Thus, the metal is already connected to the fibers and then only the plastic is applied. The function of a CMT pin connection is based on the metal surfaces having a three-dimensional surface. Here metallic pins are welded with a CMT system onto a metallic joining surface. It usually creates spherical pinheads that can be pressed into plastic and thus form a velcro-like zipper effect. This type of connection can be additionally secured with adhesive. As a result, the process time increases significantly and the production is much more difficult.

Another solution uses a ready-made fiber-reinforced plastic composite component (FKV component). The FKV component is locally melted by heat and pressed onto the CMT pins. It comes to the fiber displacement with the desired preservation of the fibers. The distortion and the visual appearance are poor. The heating of the FRP component is also particularly time consuming.

Another disadvantage of the prior art methods is that both reworking and preliminary work (such as cleaning and treating the materials) is necessary. This is time consuming and thus affects the cost of the components.

The methods in the prior art for joining metallic and non-metallic materials therefore have different disadvantages. It was the object of the invention to provide a method and a mixed compound which do not have these disadvantages and are distinguished, above all, by a high bond strength and a fast process time.

Description of the invention

This problem is solved by the independent claims of the patent application. Preferred embodiments can be found in the dependent subclaims.

• a) Stoßen eines Drahtes durch den zweiten nicht metallischen Fügepartner,
• b) Festschweißen eines Drahtendes des Drahtes an der Oberfläche des ersten metallischen Fügepartners.

In a first preferred embodiment, the invention relates to a joining method for joining at least two joining partners, wherein at least one first joining partner is a metallic joining partner and at least one second joining partner is a non-metallic joining partner, characterized in that at least the first and the second joining partner via a CMT pin method, comprising the following steps

• a) pushing a wire through the second non-metallic joining partner,
• b) firmly welding a wire end of the wire to the surface of the first metallic joining partner.

A particular innovation of this method is that the joining direction is on the side of the non-metallic joining partner. During the joining process, the wire for the CMT pins is pushed by the non-metallic joining partner so that the pins do not form during the joining process itself. This is a decisive advantage over the prior art methods which often work with pins already attached to the metal joining partner available. The optical result of this method according to the invention is significantly improved over the prior art.

In the prior art thermo-mechanical forming, disadvantages arise in particular through pre-drilling. Piercing creates a continuous hole that lets media through. This can be avoided by the method according to the invention.

• c) Aufschmelzen des Drahtes an einer bestimmten Stelle, bevorzugt durch einen elektrischen Trenn-Impuls und Erzeugung eines Schließkopfes am zweiten nicht metallischen Fügepartner, umfasst.

It is further preferred that the joining process additionally the step

• c) melting the wire at a certain point, preferably by an electrical separation pulse and generating a closing head on the second non-metallic joining partner comprises.

The emergence of this closing head is a further particular advantage of the invention, since it is accompanied by an increase in the head tensile strength, that is to say the direction of vertical load to the component surface.

The process is characterized among other things by a high-precision process control, which allows an exact adjustment of the pin length.

An advantage of the invention is that when joining only a one-sided accessibility of the joint is required. This facilitates the process and the corresponding structure.

It is preferred that the metallic joining partner comprises materials selected from the group comprising aluminum, steel, magnesium, copper or their alloys. It is also preferred that the metallic joining partner consists of these mentioned materials.

In a particularly preferred embodiment, the non-metallic joining partner comprises materials selected from the group comprising plastic, fiber-reinforced plastic, paper, leather and / or textiles. It is also preferred that the non-metallic joining partner consists of the materials mentioned.

Any of the possible combinations of metallic and non-metallic joining partners may be advantageous for a particular application.

It is preferred that the two joining partners (at least one metallic and one non-metallic joining partner) are cut to size and adapted to each other. It is also preferred that the non-metallic joining partner is tensioned. This embodiment may be advantageous for the joining process, with a person skilled in the relevant field of the prior art knows when to work with tense joining partners.

It is further preferred that the metal surface of the metallic joining partner is activated for welding. In this case, scale layers and / or oxide layers and / or impurities are preferably removed. Thereafter, the non-metallic joining partner is placed and possibly tensioned.

Depending on the choice of non-metallic joining partner, it may be useful or necessary to heat the wire before piercing. For this purpose, for example, with an additional device of the wire located in a CMT welding machine can be heated at the wire end in the vicinity of the joint to a preferred preheating temperature.

It is also preferred that the wire is not heated to a desired preheating temperature, but the non-metallic joining partner itself is heated. Which embodiment is most suitable for the particular application is known to a person skilled in the relevant field of the prior art without being inventive himself.

If, for example, textile materials are used as the non-metallic joining partner, it may be possible to dispense with heating the wire or the non-metallic joining partner.

Subsequently, the wire is preferably pushed with the wire feed of the CMT device through the non-metallic joining partner. Immediately after reaching the metal surface, the CMT pin process is started and the wire end is welded to the metal.

It is further preferred that the wire is then preferably melted when passing through an electrical separation pulse at a certain point. It forms a melting droplet to a head directly on the non-metallic joining partner. The result is a pin with a head, similar to a nail that securely and firmly connects the metallic and non-metallic joining partners.

The wire is thus preferably preferably separated after welding in a second stage by means of welding current. In the case of precise parameter control, a drop can be generated at the pin end, thereby optimizing the connection in the vertical direction to significantly increased connection strength.

In addition, it is preferred that the joining method of the invention is repeated several times, so that several pins connect the joining partners with each other. As a result, a particular connection strength is achieved. A person skilled in the relevant field of the prior art knows how many pins are to be set depending on the material of the joining partner, the area of application and the size of the joining partners in order to achieve an optimal result, without being inventive themselves.

In a further preferred embodiment, the length of the pins is automatically adapted to the graded wall thickness profile of the non-metallic joining partners.

The wall thickness profile can preferably be detected or predetermined via two paths. On the one hand, this can be done by the structural specifications according to joining plan or by sensors. The invention is not limited to any particular type of sensors. For example, sensors that evaluate current-voltage signals are possible, but also optical sensors or tactile sensors. A person skilled in the art is able to select suitable sensors, depending on the application, without being inventive himself.

It is also preferred that three-pieced or multi-sectioned compounds be reacted with the joining method of the invention. It was particularly surprising that the method of the invention could also provide satisfactory results and particularly high bond strengths in this embodiment.

In a further preferred embodiment, the joining zone is not flat. One of the joining partners is preferably a structured joining partner. In this embodiment, for example, structured sheets can be used as metallic joining partners. However, it is also possible to use structured plastic joint partners. It is preferred that the structured joining partner comprises stiffening elements, in particular honeycomb (hexagonal) basic geometry, comprising webs. It was completely surprising that the same high bond strengths could be achieved even with uneven joining zones.

In a further preferred embodiment of the joining method, the reinforcing fibers of the non-metallic joining partner are re-oriented to the load when setting the pins. By heating the wire tip, the non-metallic joining partner, preferably the plastic, is softened around the fibers and offers a push-to-side movement of the fiber so that the wire tip escapes and remains intact. The temperature of the wire tip does not destroy the fiber.

The novel use of the CMT pin process results in a high degree of freedom in the design of joint connections. The density of the pins, the pin length and the shape of the head can be varied depending on the field of application. The head is preferably varied by the process parameters. In particular, current, voltage, current flow times, feed rates and times, and the heating heat for the wire can be varied to affect the character of the head. The flexibility thus obtained is particularly advantageous over prior art methods and allows the use of the new method in a variety of different applications.

By choosing the pin material or the number of pins per square centimeter, a stress-oriented design possibility of the joining zone can be implemented. The optimum number of pins depends on the forces to be transmitted, and in some cases also fixations with very small forces are sufficient.

As pin materials in particular ordinary filler materials are in question, which are preferably selected according to the type of metallic joining partner. The pin material is selected on the basis of the base material, the joining task, joining partner material and secondary connection properties (for example, current-conducting tasks). A person skilled in the art knows which materials are best suited to the respective material without being inventive in the selection itself.

In a further preferred embodiment, loops are placed around the fabric / scrim with the welded wire and then re-welded. In this embodiment, the wire is brought in the form of an eyelet after the first hard welding and welded at another location. Afterwards a separation pulse is set.

A further advantage of the invention is that the wall thickness of the non-metallic joining partner does not have to be constant along the joining zone in order to lead to optimum results. The detection of this wall thickness curve can be integrated in the novel joining method of the invention and taken into account when setting the pins accordingly.

By the method, there is no mechanical or thermal destruction of the fibers. As a result, the preservation of the fibers is achieved for the example of a fiber-reinforced plastic composite as a non-metallic joining partner.

Due to the reduced thermal stress, there is also no distortion, melting and / or deformation of the joining zone, which ultimately results in an increased bond strength and leads to a significantly improved overall appearance.

The invention is also distinguished by the fact that no or only minor rework is necessary. The connection need not be additionally glued - as is often the case in the prior art - to ensure lasting stability. Therefore, the method provides a mixing compound directly without additional processing steps, which is characterized by a high bond strength but also visually perfect results. In the prior art, it may also happen that the geometric dimensions of the non-metallic joining partner are changed by local heating and pressing, so that a swaging of the heated component takes place. This deformation must then be trimmed when adjacent to other components or assemblies. The inventive method eliminates this step of post-processing.

In addition, the methods in the prior art often lead to optically inadequate results, so that a further aftertreatment of the surfaces is necessary. This is done, for example, by coating, smoothing or dressing. The process of the invention does not require such post-treatments either, since the visual impression of the mixed compound is flawless and no improvements are necessary.

Another disadvantage of the known methods of the prior art is that often extensive preparatory work is necessary. For example, the joining partners must be cleaned before gluing and additionally treated with primers or adhesion promoters. This can be avoided by the method according to the invention.

However, it is possible to combine the aftertreatments or preparations of the prior art with the method according to the invention, if desired.

A significant advantage of the invention is that no complex joining devices and thus no new development of a system are necessary to carry out the process. The low investment costs for the system are a decisive advantage of the invention. The plant for carrying out the method according to the invention is also characterized by low operating costs, which is of particular importance for many industries and brings with it an enormous reduction of the overall costs. The instruction of the staff to operate the system is possible without lengthy training and also the maintenance costs are low.

Another advantage is that automated processing becomes possible. The variable use of the systems, for example for conventional welding processes or for the further processing of components is a further advantage of the invention.

The invention also allows increased plant flexibility, since different component thicknesses can be realized directly by selecting the parameters and a rapid changeover of the equipment can be made. This flexibility is a decisive advantage which can not be found in the prior art.

In another preferred embodiment, the invention relates to a mixed compound comprising at least one non-metallic joining partner and at least one metallic joining partner, wherein the joining partners are joined to one another via CMT pins. The aforementioned preferred embodiments of the method are also preferred embodiments of the mixed compound.

It is preferable that the mixed compound is produced by a previously described joining method. The mixing compound thus produced is characterized by the advantages mentioned above.

It is further preferred that the mixed compounds have media-dense properties.

By the method and the mixing compound of the invention, a plurality of advantages are realized. A decisive advantage is the short process times of just a few seconds. For many sectors, this advantage is of particular importance, as it can greatly reduce costs and increase production.

Preferably, the novel joining method and / or the mixed compound is used in the automotive industry, in rail vehicle construction, but also in aerospace engineering. In addition, applications of mixed construction methods are possible in all areas of lightweight construction, so that here too the novel joining method can be advantageously used. In particular in areas of electromobility, to increase the range Michbauweisen to significantly reduce the vehicle weight and thus the energy consumption is necessary.

Figures and examples

In the following, the invention will be explained in more detail with reference to figures and examples, without being limited thereto.

1 shows in a sketch a preferred process flow. It becomes a burner of a CMT pin welder 18 used. In addition, the heating elements 17 shown. The heating heat for the wire is indicated by dashes starting from the heating elements. In this case, in step a) the wire 15 preheated. In step b) the piercing of the non-metallic joining partner (here plastic) takes place 11 and welding the wire 15 on the surface of the metallic joining partner 10 , In step c), the separation of the wire takes place 15 by melting and concomitant melting of the closing head 13 on the workpiece.

2 illustrates the welding of pins. 2a) shows the state before joining while 2 B) illustrates the state after joining. It will be the metallic joining partner 10 , the non metallic joining partner 11 and the CMT pin connections 12 shown.

3 shows preferred joining compounds of the invention. It will be the metallic joining partner 10 , the non metallic joining partner 11 and the CMT pin connections 12 and the closing head 13 shown. 3a) shows an embodiment with a pin 12 , 3b) shows an embodiment with a plurality of arranged in the direction of loading pins 12 ,

4 shows further preferred embodiments of the joint connections. It will be the metallic joining partner 10 , the non metallic joining partner 11 and the CMT pin connections 12 shown. 4a) corresponds to the embodiment of 3b) , In 4b) On the other hand, the preferred embodiment of the loop laying is also shown. The loops are labeled with reference numbers 14 Mistake.

5 illustrates the freedom in the design of joints using CMT pin process. The density of the pins 12 , the pin length and the expression of the head 13 can be varied. In 5a are pins 12 with a closing head 13 shown. In 5b the pins can be seen without a closing head. This figure illustrates what differences can be achieved in the pin end. It also shows how tight the individual pins can be set. At high forces many pins must be set.

LIST OF REFERENCE NUMBERS

10

 metallic joining partner

11

 non-metallic joining partner

12

 CMT-pin connection

13

 closing head

14

 loop

15

 wire

16

 welded wire end

17

 heating element

18

 Burner of the CMT-PIN welding machine

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 102013211580 [0004]

Claims (14)

Joining method for joining at least two joining partners, wherein at least one first joining partner is a metallic joining partner and at least one second joining partner is a non-metallic joining partner, characterized in that at least the first and the second joining partner are joined via a CMT pin method comprising the following steps: a) pushing a wire through the second non-metallic joining partner, b) firmly welding a wire end of the wire to the surface of the first metallic joining partner. Joining method according to claim 1, additionally comprising the step c) melting the wire at a certain point by an electrical separation pulse and generating a closing head on the second non-metallic joining partner. Joining method according to claim 1 or 2 additionally comprising the step c ') laying wire loops around the second non-metallic joining partner, wherein the wire is again welded to the metallic joining partner. Joining method according to at least one of the preceding claims, wherein the surface of the metallic joining partner is activated before placing the non-metallic joining partner, wherein preferably scale layers, oxide layers and / or impurities are removed. Joining method according to at least one of the preceding claims, wherein the joining partners are first cut to size and / or adapted to each other. Joining method according to at least one of the preceding claims, wherein the method is repeated several times. Joining method according to at least one of the preceding claims, wherein the length of the pins is automatically adapted to the graded wall thickness profile of the non-metallic joining partners. Joining method according to at least one of the preceding claims, wherein 3-branched or multi-sectioned compounds can be reacted. Joining method according to at least one of the preceding claims, wherein the joining zone is not flat. Joining method according to at least one of the preceding claims, wherein reinforcing fibers of the non-metallic joining partner are re-oriented according to the load when setting the pins. Mixed compound comprising at least one non-metallic joining partner and at least one metallic joining partner, wherein the joining partners are joined together via CMT pins. A mixed compound according to the preceding claim, wherein the mixed compound is prepared by a process according to any one of claims 1-10. Mixed compound according to one of claims 11 or 12 or joining method according to at least one of claims 1-10, wherein the metallic joining partner comprises aluminum, steel, magnesium, copper or their alloys and / or the non-metallic joining partner is a fiber-reinforced plastic. Mixed compounds according to any one of claims 11-13, wherein the compound may have media-dense properties.

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