METHOD FOR PRODUCING A BONDED JOINT, AND STRUCTURAL ELEMENT

Abstract

A method for producing a bonded joint between a light metal of a first component and a steel material of a second component, wherein a protective-gas joining process is used, a zinc-based filler material is used, and wherein an arc of the protective-gas joining process reaches at least the steel material of the second component, wherein a phase space of at least intermetallic phase composed of iron and the light metal is produced in a joining region adjacent to the steel material. Introduction of heat occurs so that the joint to the steel material is a solder or brazed connection and, during joining, a detachment of part of the solidified intermetallic phase(s) from the steel material of the second component starts in a melt of a solder or brazed matrix formed by the filler material and the at least one intermetallic phase is embedded in the solder matrix.

Claims

1-8. (canceled)

9. A method for producing an integral joint between a light metal of a first component and a steel material of a second component, comprising: a shielding gas joining process utilizing a zinc-based filler material is used, and an arc of the shielding gas joining process reaches at least also the steel material of the second component, wherein a phase seam comprising at least one intermetallic phase comprised of iron and the light metal is produced in a joining region adjoining the steel material, wherein the introduction of heat is effected in such a manner that the joint to the steel material is a soldered or brazed connection and, during the joining process, a detachment of at least part of the solidified intermetallic phase(s) from the steel material of the second component starts in a melt of a solder or brazed matrix formed with the filler material, and the at least one intermetallic phase is embedded in the solder or brazed matrix.

10. The method as claimed in claim 9, wherein the first component comprises aluminum or an aluminum alloy at least in the joining region.

11. The method as claimed in claim 9, wherein the zinc-based filler material comprises aluminum.

12. The method as claimed in claim 9, wherein the second component is heated by means of an additional heat source.

13. The method as claimed in claim 12, wherein the heat is supplied from a side of the second component which faces away from the joining process.

14. A structural element, comprising: a first component comprising a light metal and a second component, which comprises a steel material and is integrally joined to the first component with the involvement of a zinc-based filler material, wherein the joint to the steel material of the second component is provided by a soldered or brazed connection, which has a phase seam comprising at least one intermetallic phase composed of iron and the light metal, wherein, in the phase seam of the hardened soldered or brazed connection, the intermetallic phase(s) is or are embedded in an at least predominantly zinc-comprising solder or brazed matrix.

15. The structural element as claimed in claim 14, wherein, at least in a partial region of the joining surface of the second component which is covered with the soldered or brazed connection, a proportion of the solder or brazed matrix forms at least one cohesive separating layer, which is arranged between the steel material of the second component and at least a predominant proportion of the intermetallic phase(s) located above the partial region of the joining surface.

16. The structural element as claimed in claim 15, wherein the partial region comprising the at least one separating layer is larger than 50% of the joining surface covered with the soldered or brazed connection.

Description

[0028] The text which follows explains a preferred embodiment of the method according to the invention and also a structural element with reference to figures.

[0029] FIG. 1: shows the use of an arc process on two components to be joined to one another,

[0030] FIG. 2: shows a microscope micrograph of the joint with phase seam,

[0031] FIG. 3: shows a diagram relating to the composition of the joint in the region of the phase seam, and

[0032] FIG. 4: shows a further microscope micrograph of a further joint with phase seam.

[0033] FIG. 1 schematically shows the use of an arc process for producing an integral joint between a first component 1 composed of aluminum and a second component 2 composed of a steel material. A wire electrode 3 serves for producing an arc 4, which impinges with its surface of attack predominantly on the second component 2 composed of steel material. The wire electrode 3 is zinc-based and may contain aluminum as a further constituent, for example. Additional alloying constituents may be magnesium and/or copper, for example.

[0034] FIG. 2 shows a microscopic microsection 19 from a region of a soldered or brazed connection of a structural element produced by the method according to the invention. A steel material layer 5 of the second component 2 can be seen right at the bottom in the microsection 19. Above the steel material layer 5, a phase seam 6 having a thickness of approximately 20 m and comprising intermetallic phases 7 (here shown as a dark color) has formed. Adjoining above the phase seam 6 is a layer composed of a solder or brazed matrix 8, which consists at least essentially of the solder or brazing material of the wire electrode 3, specifically at least predominantly of zinc. The phase seam 6 is penetrated by the solder or brazed matrix 8 shown as a light color in the microsection 19. The already solidified intermetallic phase 7 became detached from the steel base material 5 during the joining process and was thus able to be infiltrated by the material of the solder or brazed matrix 8. The reason for the detachment is the different expansion behavior of intermetallic phase 7 and the steel material during the targeted introduction of heat into the second component 2. The infiltration created a separating layer 20, which is formed by the material of the solder or brazed matrix 8 and, after it has solidified, ensures at least in certain regions that there is a permanent separation of the steel material layer 5 from at least a predominant proportion of the intermetallic phase(s) 7. Fissures in the intermetallic phase(s) 7 have moreover had the effect that the intermetallic phase(s) has or have been not only infiltrated but also penetrated by the material of the solder or brazed matrix 8.

[0035] In the microsection 19 shown in FIG. 2, an increased proportion of the solder or brazed matrix 8 can be seen in the phase seam 6 approximately in the center (see the dashed line). This makes it possible to conclude that a first phase region 10 of the phase seam 6 (above the dashed line) was first formed and then detached and infiltrated by the material of the solder or brazed matrix 8, before a second phase region 11 of the phase seam 6 (below the dashed line) was formed and in turn detached and likewise infiltrated by the material of the solder or brazed matrix 8, now forming the separating layer 20.

[0036] The rectangle 12 shown upright in FIG. 2 symbolically represents a sample of the structural element which was examined with respect to the composition thereof.

[0037] FIG. 3, below a diagram, likewise shows with a microsection a sample 14 of another structural element. A concentration profile was measured on the sample 14 along a centrally running measurement line 13 by means of an energy-dispersive X-ray microanalysis. The diagram shows an Fe graph 15 for the iron content, an Al graph 16 for the aluminum content, a Zn graph 17 for the zinc content and also (less significant here) an O graph 18 for the oxygen content. It can clearly be seen that, in the case of a path shown along the abscissa of the diagram, the aluminum content increases briefly from approximately 2 m in an albeit very narrow region, but then levels off considerably, such that between approximately 3 m and approximately 4.5 m the zinc is predominant. Only from approximately 5 m to approximately 14.5 m is a region dominated substantially by the intermetallic phase composed of iron and aluminum, with the penetration with zinc also being clearly identifiable from the microsection of the sample region 14. A region which is clearly dominated by the zinc is identifiable in turn above the phase seam, from approximately 14.5 m, before an increased aluminum proportion becomes visible, which can originate from the wire electrode 3 or else from the molten aluminum material of the first component 1.

[0038] FIG. 4 shows a further microscope micrograph, which verifies that the intermetallic phase 7 forms very fine-grained structures which are shown here as a lighter color and which are distributed in the surrounding zinc-based solder matrix 8 shown as a darker color. With an increasingly fine-grained structure, the influence of the intermetallic phase 7 on the strength of the soldered connection between the solder or brazed matrix 8 and the steel material layer 5 is reduced further.

LIST OF REFERENCE SIGNS

[0039] 1 First component

[0040] 2 Second component

[0041] 3 Wire electrode

[0042] 4 Arc

[0043] 5 Steel material layer

[0044] 6 Phase seam

[0045] 7 Intermetallic phase

[0046] 8 Solder or brazed matrix

[0047] 10 First phase region

[0048] 11 Second phase region

[0049] 12 Rectangle

[0050] 13 Measurement line

[0051] 14 Sample

[0052] 15 Fe graph

[0053] 16 Al graph

[0054] 17 Zn graph

[0055] 18 O graph

[0056] 19 Microsection

[0057] 20 Separating layer