WO2020015921A1

WO2020015921A1 - Method for producing a vehicle component comprising a joining element

Info

Publication number: WO2020015921A1
Application number: PCT/EP2019/064787
Authority: WO
Inventors: Franz-Xaver Schweighart; Robert Kirschner; Mario Meinhardt; Georgij Safronov
Original assignee: Bayerische Motoren Werke Aktiengesellschaft
Priority date: 2018-07-19
Filing date: 2019-06-06
Publication date: 2020-01-23
Also published as: DE102018212030A1

Abstract

The invention relates to a method for producing a vehicle component comprising a joining element, said method having the steps: - providing a component (1) of a first material, - pressing a joining element (5) of a second material into a sheet-like section of the component (1), as a result of which the joining element (5) is fixed in a frictional and/or form-fitting manner in the component (1). At least sections of an edge region (9) which adjoins the boundary surface (10) between the joining element (5) and the component (1) are irradiated with laser radiation (L) such that the irradiated region is heated and the irradiated region of the material is metallurgically altered.

Description

description

Method for producing a vehicle component with an auxiliary joining element

The invention relates to a method for producing a vehicle component with an auxiliary joining element

In order to be able to join two or more components made of different materials, different approaches are known. In one approach, auxiliary joining elements that can be welded or soldered to the material of a first component are introduced into a second component.

From the document DE 10 2015 214 149 A1, a method and a partial assembly is known, in which a through hole is introduced into a first component and a sheet metal slug is pressed into the through hole.

The sheet metal slug serves as a joining element to connect the first component to a second component. Between the joining element and the second construction part, a material connection is formed, for example by resistance spot welding.

If such components are used in automobile construction, high strength requirements must be met for the joint connection. The strength requirements apply to both the connection between the joining element and the second component as well as the connection between the joining element and the component into which it is pressed.

Against this background, it is the object of the present invention to show a possibility of how such a component connection with improved properties can be created. The object is achieved by a method according to claim 1. Further advantageous configurations result from the subclaims and the following description.

A method for producing a vehicle component with joining aid element is specified with the steps:

Provision of a component of a first material,

- Pressing an auxiliary joining element of a second material into a sheet-shaped section of the component, as a result of which the auxiliary joining element is positively and / or positively fixed in the component.

According to the invention, an edge region, which adjoins the interface between the joining element and component, is at least partially irradiated with laser radiation in such a way that the irradiated region is heated and a metallurgical change in the material in the irradiated region is effected.

The metallurgical change can e.g. a section-by-section hardening of the joining aid element, melting of alloy elements, closing of pores at the interface or alloy diffusion between the two materials beyond the interface. Stress reduction by stress relief annealing is also conceivable. Further targeted metallurgical changes are also possible.

The process takes advantage of the fact that the narrow heat-affected zone of the laser beam, paired with the wide range of possible variations in terms of the amount of heat input and duration, offers a wide range of possible uses. Compared to thermal treatments in ovens, the proposed method is not only more flexible, but also enables the targeted treatment of individual sections only. For example, the connection between the joining element and the component can only be post-treated specifically in the areas that are particularly stressed or at risk of failure.

The component into which the joining element (s) are inserted can be made of sheet metal material, e.g. hot-formed steel, aluminum or magnesium sheet, or a sheet-like fiber composite plastic, e.g. with reinforcements made of carbon, glass and / or aramid fibers. The component can be, in particular, a sheet metal molded part, it also being possible to use cast components or profile parts which are formed in a sheet-like manner at the joint or joints at which the joining aids are pressed in. In particular, the component can be a body component or body component.

The joining aid is pressed into a sheet-like section of the component. The joining aid preferably extends over the thickness of the sheet-like section. The interface to the component runs around the circumference around the joining element. The end faces of the joining element point towards the component surfaces. The joining element is preferably designed as a metal slug, which is understood to mean a headless and shaftless metal part. Due to the simple geometry, such a metal slug can be produced very inexpensively, for example by punching it out of a sheet metal or cutting a wire. The metal slug can in particular have a cylindrical, spherical, conical or frustoconical shape. Functional elements such as a threaded section, a clip or the like can also be molded onto the metal slug. The joining auxiliary element is in particular made of a material that is related to of the second component, with which the part provided with the joining element is to be joined, has sufficient welding or soldering suitability. The joining aid element is preferably formed from a steel or aluminum workpiece.

It is particularly advantageous that the auxiliary joining element can be formed from a material that is foreign to the material of the component into which the auxiliary joining element is pressed. Typical problems when joining the like materials, e.g. Contact corrosion or insufficient quality of the connection can be eliminated or significantly reduced with the method according to the invention.

The joining element is preferably pressed into a through hole that was previously formed in the component. The through hole has a hole wall which is delimited to the component surface by a hole edge. A hole edge or both hole edges are preferably each provided with a chamfer. Any burr that may be present is removed by the chamfer. Furthermore, the chamfer simplifies the alignment of the auxiliary joining element when it is pressed in, and favors the formation of a positive connection in which, in a preferred embodiment, the auxiliary joining element can form in the manner of a countersunk rivet in the pre-hole and forms an undercut on both sides with the component. The chamfer is created by embossing. This has the further advantage that material hardening takes place in the embossing edge, which is further increased by the subsequent pressing in of the joining element. Furthermore, it was found that the embossing also reduced the hydrogen embrittlement and counteracted sensitivity to edge cracking. It has been shown that the resulting component connection achieves surprisingly high strength values that lie above the strength of the base material of the component. If the component is embossed, one remains any existing coating of the component, such as a corrosion protection layer, is at least partially preserved. For example, the method described in the application DE 10 2016 201 433 A1 and hereby incorporated by reference into the present application can be used for this purpose.

In a preferred embodiment, the heating takes place until a material layer, e.g. may be formed on the component or on the auxiliary element. This material layer can, for example, be an anti-corrosion layer, such as e.g. trade a zinc coating or a previously applied welding or soldering additive. As a result of the melting, the material layer liquefies, runs into the gap which is present at the interface between the joining element and the component and at least partially fills it up. When the gap is filled, there is an increase in the connection strength between the component and the joining element.

In one embodiment, a through hole is formed in the component, a chamfer is stamped on at least one side, and the joining aid element is pressed into the through hole, whereby the joining aid element forms a collar protruding into the chamfered area. Such a collar anchors the joining element in the component and offers increased strength in one pulling direction.

In a further embodiment, a bevel is stamped on the through hole on both sides of the component and the joining aid element forms two collars when pressed in, each of which protrudes into the chamfered area. The collars form an undercut in the component, which means that the auxiliary element is gripped on both sides. Such a "clinging" joining element has significantly higher strengths against knocking out of the component.

A further increase in the connection strength between the component and the joining element can be achieved by targeted and locally limited flaring of the joining element. If the joining element is designed with a collar on one or both sides, it can be provided that this collar is hardened in a targeted manner. In one embodiment, the irradiated area contains the collar of the joining element and the heating by means of laser radiation takes place in such a way that hardening of the irradiated area is achieved by subsequent quenching. The hardening can be, for example, transformation hardening or precipitation hardening. In the event of a crash, in particular, with a strong deformation of the component, knocking out of the joining aid element from the component can be prevented for longer. Through a suitable choice or variation of the laser parameters such as power, focus position, beam spot diameter, oscillation, radiation duration etc., the cooling rate can be controlled in addition to the targeted heating and the curing can be controlled.

In one embodiment, it is provided that the component is made of a first material and the joining aid element is made of a second material that is foreign to the first material. If materials of a different type, such as aluminum and steel, are combined with the joining element and component, special precautions must be taken to prevent contact corrosion. According to one embodiment of the method, the laser beam is aligned and the irradiated area is placed such that both the material of the component and the joining element are melted. The heating takes place in such a way that the materials become molten and alloy element diffusion is achieved. This leads to a Leveling in the potential transition between the two materials. While there is a step-shaped potential jump before, a suitable parameter selection in the irradiated area sets a ramp-like transition of the potentials, for example the transition can also be linear. The choice of laser parameters depends, among other things, on the material type and thickness. Contact corrosion can thus advantageously be prevented or significantly reduced, so that further measures can be dispensed with.

Furthermore, in one embodiment, the edge area of the joining element is heated in such a way that the irradiated area is annealed with low stress. In this way, stresses which are formed by pressing the joining element into the component can be reduced in a targeted manner.

In principle, a suitable choice of laser parameters and a possible subsequent quenching of the component can be used to implement a large number of metallurgical changes in the component.

The targeted irradiation to achieve a metallurgical change can take place in different areas depending on the requirement and the desired effect. As described above for alloy diffusion, the irradiated area can extend both to a part of the component and to a part of the joining aid element. Of course, only a portion of the component adjacent to the interface or a portion of the joining element adjacent to the interface can be irradiated.

For example, it is conceivable that if the auxiliary joining element has a cylindrical section adjoining the collar, only the edge region of the cylindrical section is irradiated. Likewise can only the collar is irradiated and the cylindrical section is taken out. If, for example, pores in the interface are to be closed with the irradiation or the described potential equalization is to be set, it may be desirable to irradiate the interface over the entire thickness of the component. This can be done from one or two sides.

In one configuration, the edge region can be irradiated and heated all round with laser beam radiation. In this case, the irradiated area runs in a ring along the interface between the component and the auxiliary element. However, it is also conceivable to use only individual sections of the edge area, e.g. to heat specific areas or short sections with laser radiation. The movement of the laser beam is not limited to certain courses. For example, the laser beam can move around the edge area in a circular manner. The laser beam can be moved star-shaped, spiral-shaped or in any other form between sections of the region to be irradiated.

The edge area extends across the entire component thickness across the component surface. The edge region extends from the interface between the component and the auxiliary joining element both in the direction of the longitudinal axis of the auxiliary joining element and radially into the component away from the auxiliary joining element. The edge area can e.g. have a width of several beam spot diameters.

In plan view, the joining aid has a central welding area, in which a second component can be welded on in a further joining step. The welding area is ring-shaped from the edge area ben. The welding area can preferably have a diameter in Have a range from, for example, half to two thirds of the diameter of the joining aid element. The width of the edge area can accordingly preferably be in a range from a quarter to a sixth of the diameter of the joining element. Narrower marginal areas are also conceivable. In a preferred embodiment, the edge region in the joining aid element extends over a width that is at most a quarter or at most a sixth of the diameter of the joining aid element. The diameter of the joining element is measured at the point with the smallest diameter.

The edge area in the component runs along the interface to the joining aid element and has approximately the same width as the edge area of the joining aid element.

It has been shown that the changes made in terms of joining technology can also be obtained in subsequent joining processes in which the component is welded to the joining auxiliary elements with another component. That is e.g. the case when the subsequent joining process is also laser welding. Due to the narrow heat affected zone of laser welding, another possibly undesirable metallurgical change relevant to the joining process can be prevented. Other welding processes, such as Resistance spot welding is possible; it may be advantageous to provide contact tips on the joining elements for a targeted current flow in the middle of the joining elements.

The following advantageous effects can be achieved with the present invention: - Improved shape filling and targeted compensation of the electrochemical potential difference between aluminum and steel by laser sintering / laser curing of a powder intermediate layer supplied. A zinc-aluminum powder mixture would be conceivable.

- Sealing in the contact zone through the targeted introduction of heat / energy is made possible by the use of lasers and parallel to the laser welding process.

- Closing of pores in the contact zone through the targeted introduction of heat / energy, possible through the use of lasers and particularly useful for the slug element used.

- Targeted (due to the definable energy introduced by the laser welding process) reduction of tensions on the slug that arise during the insertion process.

- Increase or improvement of the contact surfaces in the contact area by material softening using the laser.

- Melt the zinc layer in the surface transition area to seal and glue the connection.

The component produced with the method according to the invention, also referred to as the first component, can be processed further using known methods, for example to form a component composite with at least one second component, the joining aid element (s) pressed with the first component being welded, soldered and / or or be glued. Such welding can also be done with laser radiation, for example. Different laser tools can be used, for example laser pickers, remote scanners, etc. In the case of laser beam welding, different seam patterns are possible, such as a star, circle, spiral, to extend the effective seam length. For degassing during the welding process, the use of spacer knobs is optional to improve the welding quality. These can NEN can also be represented by the auxiliary joining element by slightly projecting the element. To stabilize the welding process, further geometric precautions must be taken on the auxiliary joining element.

Furthermore, auxiliary joining elements can be introduced into plastic components or into CFRP components in both joining partners and these can then both be welded to the auxiliary joining elements using the laser beam welding process. Here, laser beam welding has enormous potential in terms of cycle time savings. It is a non-contact joining process and a material-independent process in the metallic joining area (steel-steel connection or aluminum-aluminum connection possible). Laser beam welding has a lower temperature influence on the components than the resistance point welding. There is no need for a filler metal. Another advantage is a massive gain in flexibility in the design (assemblies) and in production. Laser beam welding only requires one-sided accessibility and thereby solves the accessibility problem of resistance spot welding technology.

With the combination of pressed-in auxiliary joining elements, an aluminum-steel connection is possible despite the use of laser beam welding. The flange widths can be reduced by laser beam welding, which enables mass savings. Mixing bodies can be manufactured using one process. There is a possibility of a massive increase in quality, since the use of image processing systems can support the precision of the laser.

Further advantages, features and details of the invention will become apparent from the following description, in which embodiments of the invention are described in detail with reference to the drawings. Here, those mentioned in the claims and in the description Features are essential to the invention individually or in any combination. If the term "can" is used in this application, it concerns both the technical possibility and the actual technical implementation.

Exemplary embodiments are explained below with reference to the accompanying drawings. In it show:

Figure 1 Schematic representation of a component at various stages of the process

FIG. 2 is a sectional view of a component with a pressed-in joining element; FIG. 3 is a top view of the component from FIG. 1

In the method, a component 1 is initially provided, for example a sheet metal component. A through hole 2 may be formed in the component, e.g. by punching or cutting. At the edges facing the component surface, a circumferential chamfer 3 or 4 is embossed. Due to the embossing, the material of the component is strengthened.

In a next step, a joining element 5 in the form of a metal slug is introduced into the through hole and pressed in it, as a result of which it is non-positively fixed in component 1. In the area of the bevels 3, 4, the auxiliary joining element 5 additionally forms a positive connection through the collars 6 and 7, respectively, which engage around the component 1 on both sides undercut.

The pressed-in joining element now offers the possibility of joining another component to this joining element with component 1. This is particularly advantageous if component 1 and another component consist of materials of a different type and welding is not readily possible. The joining aid element can then be formed from a material which enables welding or soldering to the further component.

If this connection is made by welding, then the welding is carried out in a central area, here referred to as welding area 8. Before the component on the joining aid element is connected to another component, a laser treatment step takes place. A laser beam L is directed towards an edge region 9. The edge area 9 runs around the welding area 8 and is composed of an edge area 9 ^′ in the joining aid element and an edge area 9 ^″ in the component. The edge area includes the interface 10 between the joining aid element 5 and component 1.

The welding area 8 typically makes up about half to two thirds of the diameter D of the joining element 5. Accordingly, the edge area 9 ^' in the auxiliary joining element 5 has a width B of approximately one quarter to one sixth of the diameter D. The edge area 9 ^'' in the component 1 has approximately the same width B.

By irradiating the edge region or parts of the edge region with laser radiation L, a metallurgical change in the irradiated region is now carried out. Depending on the selected parameters, this can be, for example, melting on for alloy diffusion between the material of the component 1 and the joining element 5, hardening of the edge region 9 ^'of the joining element 5 or the collar 6, 7. Likewise, a stress relieving for the reduction of stresses is conceivable, which were produced by pressing the joining aid element 5 into the component.

FIG. 2 shows a sectional view of a further component 1A, into which an auxiliary joining element 5 has been pressed. The difference to that in Figure 1 Component shown is that the component comprises a corrosion protection layer 11 in the form of a zinc layer. This layer has largely remained during the generation of the chamfers at the through hole by the embossing process. After pressing in the joining element, this zinc layer can now be melted with the laser beam. The resulting melt flows into a gap that may be present at the interface 10 and can be used to fill the same. Furthermore, zinc atoms can be incorporated into the base material of the joining element 5 or the component 1 by targeted melting using a laser beam in order to improve the mechanical properties or to reduce potential differences at the interface 10.

Although not shown in the figures, the irradiation with laser radiation for the targeted metallurgical change of the edge region can also be carried out on differently shaped joining elements, for example on joining elements with only one chamfer or completely without chamfer or on joining elements with additional functional sections such as e.g. Threads.

FIG. 3 shows a plan view of the component from FIG. 1 with the interface 10 between component 1 and joining aid element 5. Depending on the application, the edge area can be irradiated all around the entire joining aid element 5, as indicated by the irradiated area 12 shown in FIG. Alternatively, only a partial area, for example a spot or a stretch section, can be post-treated with laser radiation. LIST OF REFERENCE NUMBERS

1, 1 A component

2 through hole

3, 4 chamfer

5 joining aid

6, 7 collar

8 welding section

9, 9 ^' , 9 ^" edge area

10 interface

1 1 Corrosion protection layer

12 irradiated area

B Wide edge area

D Joining element diameter

L laser beam

Claims

claims

1. Method for producing a vehicle component with joining aid element with the following steps:

- Providing a component (1) of a first material,

- Pressing an auxiliary joining element (5) of a second material into a sheet-metal section of the component (1), whereby the auxiliary joining element (5) is fixed in the component (1) in a non-positive and / or positive manner,

characterized by the further step, after which

- An edge region (9), which adjoins the interface (10) between joining aid element (5) and component (1), is irradiated at least in sections with laser radiation (L) in such a way that the irradiated region heats up and a metallurgical change in the material is effected in the irradiated area.

2. The method according to claim 1, in which

a through hole (2) is formed in the component (1) and a chamfer (3) is stamped onto it at least on one side and

the joining element (5) is pressed into the through hole (2), whereby the joining element (5) forms a protruding into the chamfer (3) Kra gene (6).

3. The method according to claim 2, in which

A chamfer (3, 4) is embossed on the through hole (2) on both sides of the component (1) and the joining aid element (5) forms two collars (6, 7) when pressed in, which grip around the component (1) undercut.

4. The method according to any one of the preceding claims, in which the heating takes place until a material layer (11) melts and the change in joining technology includes at least partially filling a gap at the interface (10) of component (1) and joining aid element (5) with the melted material.

5. The method according to claim 4, in which

the material layer (11) is a zinc layer.

6. The method according to any one of the preceding claims, in which the irradiated area includes the collar (6, 7) of the joining element (5) and the heating by means of laser radiation (L) is carried out in such a way that after subsequent cooling, the irradiated area is hardened ,

7. The method according to any one of the preceding claims, in which the irradiated area contains both the material of the component (1) and the joining auxiliary element (5) and the heating takes place until the material in the irradiated area melts, in such a way that alloying element diffusion is achieved becomes.

8. The method according to any one of the preceding claims, in which the irradiated area is stress relieved by the heating.

9. The method according to any one of the preceding claims, in which the irradiated area (12) runs in a ring along the interface (10) between the component (1) and joining aid element (5).

10. The method according to any one of the preceding claims, in which the edge region (9 ^' ) in the joining aid element (5) extends over a width (B) which makes up a maximum of a quarter or a maximum of one sixth of the diameter (D) of the joining aid element.

11. The method according to any one of the preceding claims, in which the component (1) is formed from a first material and the joining auxiliary element (2) from a second material alien to the first material.

12. The method according to any one of the preceding claims, in which the component (1) is a body part or body part.