JOINING COMPONENT AND METHOD FOR ITS PRODUCTION

Abstract

The present invention relates to a joining component (10) with a joining surface (12) which has an application area (14) to which a joining material (16) is pre-applied and which can be later activated by means of heat treatment, wherein the application area (14) has a retentive surface structure with elevations (20) forming material undercuts (26), and the joining material (16) at least partially covers the application area (14) and is introduced into the material undercuts (26).

Claims

1. A joining component comprising: a joining surface including an application area, and the application area includes a retentive surface structure having a plurality of retentions with elevations and material undercuts beneath a top of the elevations; and a joining material, activatable by later heat treatment, is located on the application area and is introduced into the material undercuts.

2. A joining component according to claim 1, wherein the joining component is a stud which includes a shank extending along a central axis and a flange radially extending transversely to the shank.

3. A joining component according to claim 2, wherein the joining surface is arranged on an upper side of the flange facing away from the shank.

4. A joining component according to claims 1, wherein a diameter (D.sub.A) of the application area is smaller than a diameter (D.sub.F) of the joining surface.

5. A joining component according to claim 4, wherein the diameter (D.sub.A) of the application area is at least 8 mm smaller than the diameter (D.sub.F) of the joining surface.

6. A joining component according to claim 1, wherein the joining material comprises a chemically non-crosslinked or not completely chemically crosslinked adhesive which can be liquefied and chemically crosslinked during the later heat treatment.

7. A joining component according to claim 1, wherein a plurality of dimensionally stable spacer elements, preferably consisting of glass, are distributed in the joining material.

8. A joining component according claim 7, wherein the elevations forming the material undercuts project upwards above the joining surface by a height (h.sub.R) of the retentions, and a diameter of the spacer elements (D.sub.HR) is larger than the height (h.sub.R) of the retentions.

9. A joining component according claim 8, wherein the diameter of the spacer elements (D.sub.HR) is less than 200 m, and the height (h.sub.R) of the retentions is less than 60 m.

10. A joining component according to claim 1, wherein the retentions are arranged in a grid pattern in the application area.

11. A joining component according to claim 1, wherein the elevations forming the material undercuts create an irregular surface structure.

12. A joining component according to claim 1, wherein the joining surface is made of metal and the retentive surface structure is created by melting the metal by means of one of a laser beam, an ion beam or an electron beam.

13. A method for producing a joining component having; a joining surface including an application area, and the application area includes a retentive surface structure having a plurality of retentions with elevations and material undercuts beneath a top of the elevations; and a joining material, activatable by a later heat treatment, is located on the application area and is introduced into the material undercuts; wherein the method comprises the steps of: providing a joining component with a joining surface which has an application area, and the application area has a retentive surface structure with elevations forming material undercuts; applying a heated joining material onto the application area so that the joining material is atop the application area and flows into the material undercuts; cooling the joining material such that the joining material is captively retained on the application area, the joining component can be transported and the joining material can be activated at a later point in time by means of heat treatment in order to attach the joining component to a workpiece.

14. A method according to claim 13, wherein the provision of the joining component further comprises: producing a blank of the joining component by means of cold forming; creating the retentive surface structure by melting the application area of the joining surface by means of a laser beam, an ion beam or an electron beam.

15. A method according to claim 14, wherein creating the retentive surface structure further includes: evaporating contaminants in the application area of the joining surface by means of radiation-based cleaning.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0052] Exemplary embodiments of the invention are represented in the drawings and are explained in more detail in the subsequent description. The drawing is as follows:

[0053] FIG. 1 shows a schematic longitudinal sectional view through a joining component according to a first embodiment of the invention with joining material pre-applied thereto.

[0054] FIG. 2 shows a perspective schematic view of the joining component according to the FIG. 1 first embodiment of the invention, but without joining material 16.

[0055] FIGS. 3A-3C show an enlarged detailed view of an application area of a joining surface of the joining component according to an embodiment of the invention, wherein FIG. 3A shows an enlarged plan view, FIG. 3B shows a perspective detailed view and FIG. 3C shows a sectional view of a part of the application area.

[0056] FIG. 4 shows a schematic longitudinal sectional view through a further embodiment of a joining component according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0057] In FIG. 1, a first embodiment of a joining component is shown schematically in longitudinal section. The joining component is collectively identified therein by the reference number 10.

[0058] The joining component 10 has a joining surface 12. This joining surface 12 preferably consists of a metal material. A joining material 16 is pre-applied to a section of this joining surface 12, which is in the present case is referred as the application area 14.

[0059] The application area 14 has a retentive surface structure. Details of this retentive surface structure of the application area 14 are shown in FIGS. 3A-3C.

[0060] As is especially apparent in FIG. 3A, the retentive surface structure of the application area 14 has a plurality of so-called retentions 18. One of these retentions 18 is shown by way of example in an enlarged detailed view in FIG. 3B.

[0061] Such retentions 18 are created by means of irradiation of the application area 14 of the joining surface 12 by means of a laser beam, ion beam or electron beam. Such a laser beam, ion beam or electron beam leads to the material on the surface of the application area 14 melting and to portions of the material banking up towards the top around the impingement point of the beam on account of the evaporation and other processes. As soon as this happens, the laser beam, ion beam or electron beam is interrupted so that the upwardly spurting molten metal solidifies and crown-like formations 20 are created around the laser point, which formations have enlarged diameters or bead-like elements 22 which are shown schematically in a sectional view in FIG. 3C.

[0062] This type of crown-like formations 20 are referred to as retentions 18. In the center of the crown-like formations 20, that is to say in the proximity of the impingement point, a type of recess 24 is formed. It is understood that the retentions 18 have irregular structures due to process- or manufacturing-related reasons. The crown-like formations 20 are generally referred to in the present case as elevations 20. The significance of these elevations 20 is that these form material undercuts 26 on account of the bead-like elements 22 which they have at their ends. These material undercuts 26, by means of a type of overhang (bead-like elements 22), form subjacent, semi-open cavities in the application area 14 of the joining surface 12.

[0063] The joining material 16 shown in FIG. 1 has been applied in the heated, liquefied state onto the application area 14 and has extended on the application area 14 in a lens-like manner and has solidified in this lens-like form 17 as a result of cooling.

[0064] As a result of the structure of the plurality of retentions 18 in the application area 14 with the elevations 20 forming material undercuts 26, a type of clamping between joining material 16 and application area 14 has resulted during the cooling of the joining material 16. On the boundary surface between joining material 16 and application area 14, the joining material 16 has therefore nested itself in the material undercuts 26 in or below the retentions 18. Due to the undercuts 26, the retentions 18 can therefore also absorb forces which are parallel to or perpendicular to the joining surface 12. Therefore, an adequate retention force of the pre-applied joining material 16 is ensured, as a result of which an exfoliation or shearing off of the joining material 16 from the joining surface 12 of the joining component 10 is prevented especially during the transporting.

[0065] The joining component 10 can therefore be packaged and transported together with joining material 16 applied thereto as loose bulk material without the joining material 16 lens 17 which is attached on the application area 14 being separated from the joining surface 12 of the joining component 10 during the transporting.

[0066] In the case of the embodiment of the joining component 10 according to the invention shown in FIGS. 1 and 2, it is a stud which is preferably designed as an adhesive stud. The pre-applied joining material 16 preferably has according to this embodiment a chemically non-crosslinked or not completely chemically crosslinked adhesive which during the joining process, that is to say during the attaching of the stud 10 to a workpiece, can be liquefied and fully chemically crosslinked by means of heat treatment (e.g. by means of inductive heat treatment). The full retention strength of the adhesive by means of specific adhesion is therefore built up only during the joining process as a result of complete chemical crosslinking of the adhesive. The retentive surface structure of the application area 14 described above, however, already ensures an adequate retention strength before the complete crosslinking of the adhesive, which is sufficient for the transporting of the adhesive stud together with the pre-applied adhesive lens 17.

[0067] The stud 10 shown in FIGS. 1 and 2 is preferably of symmetrical or at least in the main symmetrical design. The stud 10 has a shank 30 extending along a central axis 28. This shank 30 is frequently also referred to as the anchor section of the stud 10, since this can serve for the fastening or anchoring of other components. When being used in body construction, pipes are frequently fastened to this shank 30. A male thread can also in principle be provided on the shank 30.

[0068] Transversely to the shank 30 or transversely to the central axis 28, the stud 10 has a flange 32. With the aid of this flange 32, the stud 10 is attached or adhesively bonded to the workpiece. The flange 32 is especially of plate-like or cylindrical design and extends essentially in the radial direction around the central axis 28. The joining surface 12 is preferably provided on the upper side of the flange 32 facing away from the shank 30.

[0069] The application area 14 already mentioned above forms a section of the joining surface 12. The joining surface 12 as well as the application area 14 are preferably symmetrical around the central axis 28. Especially preferably, the joining surface and application area 14 are in each case are of circular shape and concentric to the central axis 28, as is shown by way of example in FIG. 2.

[0070] In FIG. 1, the diameter of the joining surface 12 is designated D.sub.F and the diameter of the application area 14 is designated D.sub.A. The diameter D.sub.F of the joining surface 12 is preferably at least 8 mm larger than the diameter D.sub.A of the application area 14. The joining material 16 preferably covers the entire application area 14 over the entire diameter D.sub.A. The region of the joining surface 12 remaining free around the application area 14 serves especially for avoiding corrosion of the retentions 18 surface structure in the application area 14. Since the retentions' 18 structuring is accompanied by an increase of corrosion potential, contact with electrolytes is to be avoided. Therefore, it is sufficient to structure the inner application area 14 of the bolt flange 32 which is protected against moisture ingress by the adhesive 16. Consideration is especially to be given in this case to the fact that moisture of several millimeters can penetrate through a crosslinked polymer or along the boundary layer into the adhesion zone. The diameter of the adhesive lens 17 can therefore also be designed to be larger than the diameter D.sub.A of the application area 14 so that the adhesive or the joining material 16 covers more than just the application area 14 in which the retentive surface structure is located.

[0071] Furthermore, it is preferably to be ensured that the joining surface 12 or the application area 14 is not in contact with the workpiece by the retentions 18 or their upper ends 22 after the joining of the stud 10 with the workpiece. In FIG. 3C, the height of the retentions 18 is generally designated h.sub.R. It is understand that this height h.sub.R of the retentions is an irregular height depending on the shape since each elevation 20 basically has a slightly different height h.sub.R.

[0072] Shown in FIG. 4 is a further embodiment of a joining component 10 of the aforesaid type which meets the last-named requirements. The joining material 16 according to this embodiment has a plurality of dimensionally stable spacer elements 34. These spacer elements 34 are preferably spherical elements consisting of glass which are embedded into the joining material 16.

[0073] A diameter D.sub.SE of these spacer elements 34 is preferably greater than the maximum height h.sub.R of the retentions 18 which are provided in the application area 14. The maximum height h.sub.R of the retentions is preferably less than 60 m. The spacer elements therefore preferably have a diameter D.sub.SE which lies within the range of 40 m to 100 m. As soon as the joining material 16 is liquefied during the joining process and after its curing permanently connects the stud 10 to the workpiece, the gap between the joining surface 12 of the stud 10 and the workpiece is therefore defined by the spacer elements 34. During the joining process, the spacer elements 34 are distributed preferably uniformly to a greater or lesser extent on the joining surface 12 or on the application area 14 and so set the gap between stud 10 and workpiece.

[0074] In conclusion, reference may once more be made to the fact that the joining component 10 or 10 according to the invention does not necessarily have to be an adhesive stud. Alternatively to this, the aforesaid features can also be applied in the case of a weld stud or a semi-hollow punch rivet. The joining material 16 or 16, as an alternative to an adhesive, can also feature a thermoplastic material for welding or a fusion solder for soldering. Depending on the component, the joining surface 12 with the joining material 16 or 16 arranged thereon does not necessarily have to be arranged on the flange of the 10 or 10 either. In the case of a semi-hollow punch rivet, it would also be conceivable in principle to provide the retentive surface structure, together with the pre-applied joining material 16 applied thereto, on the outer side of the shank.

[0075] Although exemplary embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.