METHOD FOR PRODUCING A COMPONENT STRUCTURE WITH IMPROVED JOINT PROPERTIES, AND COMPONENT STRUCTURE

Abstract

A method for producing a component structure from a first component and a second component may involve connecting the first component to the second component by way of a thermal joining process. The component structure has good crash properties, has good vibration resistance, has a lightweight construction, and is produced cost-effectively at least in part because the first component being a steel composite structure comprising a softer layer and a more-rigid layer. The softer layer may have a lower material strength and a higher deformability than the more-rigid layer. A part of a joint zone that is located in the first component may be formed at least partially in the relatively soft layer.

Claims

1.-14. (canceled)

15. A method for producing a component structure from a first component and a second component, the method comprising connecting the first component to the second component at a joint zone by way of a thermal joining process, wherein the first component is a steel composite structure that includes a softer layer and a more-rigid layer, with the softer layer having a lower material strength and a higher deformability than the more-rigid layer, wherein a part of the joint zone located in the first component is formed at least partially in the softer layer.

16. The method of claim 15 wherein an outer layer of the first component that faces the second component is the softer layer.

17. The method of claim 15 wherein the part of the joint zone located in the first component extends over a plurality of layers of the first component.

18. The method of claim 15 wherein the softer layer comprises a deep-drawing steel, an interstitial-free steel, or a micro-alloyed steel, wherein the more-rigid layer comprises a super high strength steel or an ultra high strength steel.

19. The method of claim 15 wherein the more-rigid layer comprises manganese-boron steel with a martensite structure.

20. The method of claim 15 wherein in a state of use the softer layer has an elongation at brake A.sub.80 of at least 10%.

21. The method of claim 15 wherein in a state of use the softer layer has an elongation at brake A.sub.80 of at least 17%.

22. The method of claim 15 wherein a carbon content of the softer layer is at most 0.25% by weight.

23. The method of claim 15 wherein a carbon content of the softer layer is at most 0.1% by weight.

24. The method of claim 15 wherein at least one of: in a state of use the softer layer has a tensile strength R.sub.m of at most 1000 MPa; or in a state of use the more-rigid layer has a tensile strength R.sub.m of at least 700 MPa.

25. The method of claim 15 wherein in a state of use the softer layer has a tensile strength R.sub.m of at most 600 MPa; and in a state of use the more-rigid layer has a tensile strength R.sub.m of at least 1000 MPa.

26. The method of claim 15 wherein the thermal joining process comprises welding, wherein the joint zone is a weld nugget or an MAG weld.

27. The method of claim 15 wherein the thermal joining process comprises resistance spot welding.

28. The method of claim 15 comprising producing a starting material for generating the first component by roll cladding or casting.

29. The method of claim 15 comprising hot forming at least one of the first component or the second component before connecting the first and second components.

30. The method of claim 15 comprising press hardening at least one of the first component or the second component before connecting the first and second components.

31. The method of claim 15 wherein the first component has a symmetrical configuration of the softer and the more-rigid layers with respect to at least one of thickness or material of the softer and the more-rigid layers.

32. The method of claim 15 wherein the first component has an asymmetrical configuration of the softer and the more-rigid layers with respect to at least one of thickness or material of the softer and the more-rigid layers.

33. The method of claim 15 wherein the first component further comprises at least a third layer.

34. A component structure for a vehicle that is produced according to the method of claim 15.

Description

[0075] The invention will be explained in more detail in the text which follows on the basis of advantageous exemplary embodiments and in conjunction with the drawing, in which:

[0076] FIGS. 1a,b show a cross-sectional view of a component structure according to the prior art and a hardness profile in the form of a sketch;

[0077] FIG. 2 shows a cross-sectional view of a first exemplary embodiment of a component structure according to the invention and a hardness profile in the form of a sketch;

[0078] FIG. 3 shows a cross-sectional view of a second exemplary embodiment of a component structure according to the invention; and

[0079] FIG. 4 shows a cross-sectional view of a third exemplary embodiment of a component structure according to the invention.

[0080] FIG. 1a firstly shows a cross-sectional view of a component structure according to the prior art. The component structure 1 comprises a first component 2 and a further component 4. The component 2 is, for example, press hardened and has a tensile strength of 1500 MPa. The component 2 has been joined to the further component 4 by means of resistance spot welding. This results in a weld nugget 6.

[0081] FIG. 1b shows in sketch form the hardness profile 8 in the region of the weld nugget 6 (illustrated in FIG. 1a) along the measuring points 9. For this purpose, the hardness has been plotted on the axis 10 against the position along the cross section on the axis 12. It is apparent that the component structure 1 has a high level of hardness far outside the weld nugget 6 (region A) owing to the material property of the first component 2 and in the interior of the weld nugget 6 (region B). However, in the edge region or junction region of the weld nugget 6 (region C) there arises a softening zone with a local drop in the hardness. Here, crack starters form, as a result of which this region is the starting point for failure of a material in the case of loading, in particular in the case of high loading such as, for example, in the case of a crash.

[0082] FIG. 2a shows a cross-sectional view of a first exemplary embodiment of a component structure 101 according to the invention, which component structure 101 has been produced with an exemplary embodiment of the method according to the invention. The component structure 101 comprises a steel material composite as a first component 102 and a further component 104 which have been joined by means of resistance spot welding. The first component 102 comprises a relatively soft layer 102a and a relatively rigid layer 102b, wherein the relatively soft layer 102a has a higher deformability than the relatively rigid layer 102b. The relatively soft and the relatively rigid layers 102a, 102b are joined to one another in a materially joined fashion, for example by hot roll cladding. The relatively soft layer 102a is here an outer layer of the first component 102 facing the further component 104.

[0083] The relatively soft layer 102a is produced in this case from the material MBW 500 and has in the state of use (after austenitizing at 920 C. and subsequent hot forming and press hardening) a yield strength R.sub.p 0.2 of 400 MPa, a tensile strength R.sub.m of 550 MPa and an elongation at brake A.sub.80 of at least 17%. The relatively rigid layer 102b is produced in this case from the material MBW 1500 and has in the state of use or press-hardened state a yield strength R.sub.p 0.2 of 1000 MPa, a tensile strength R.sub.m of 1500 MPa and an elongation at brake A.sub.80 of at least 5%. The portions of the relatively soft and relatively rigid layers 102a, 102b are each here approximately 50% of the thickness of the first component 102. Overall, the first component has approximately a tensile strength of 1000 MPa. The further component 104 is in this case a monolithic component made of a steel material. The part of the weld nugget 106 located in the first component has been constructed exclusively in the relatively soft layer 102a in this case.

[0084] FIG. 2b shows in sketch form the hardness profile 108 in the region of the weld nugget 106 (illustrated in FIG. 2a) along the measuring points 109. For this purpose, the hardness has in turn been plotted on the axis 110 against the position on the axis 112. It is to be noted that the component structure has a lower hardness far outside the weld nugget 106 (region A) than in the interior of the weld nugget 106 (region B) owing to the relatively high deformability of the relatively soft layer 102a. However, in the edge region of the weld nugget 106 a softening zone with local drop in the hardness is not brought about. As a result, crack starters as a starting point for failure of a material can be avoided or reduced.

[0085] FIG. 3 shows a cross-sectional view of a second exemplary embodiment of a component structure 201 according to the invention which is similar to the exemplary embodiment shown in FIG. 2. In contrast to the first component 102 from FIG. 2, the first component 202 is constructed with three layers and has, in addition to the layers 202a, 202b formed before, in addition a (second) relatively rigid layer 202c. The layer 202c is composed of the same material as the relatively rigid layer 202b. The relatively soft layer 202a is formed here lying on the inside. The relatively rigid layer 202c facing the further component 204 is, however, constructed so as to be thinner than the relatively rigid layer 202b facing away from the further component 204. Owing to this asymmetrical design of the first component 202 with respect to the thicknesses of the layers, the relatively soft layer 202a is again arranged in such a way that the part of the weld nugget 206 located in the first component 202 is constructed partially in the relatively soft layer 202a.

[0086] FIG. 4 shows a cross-sectional view of a third exemplary embodiment of a component structure 302 according to the invention which is similar to the exemplary embodiment shown in FIG. 3. In contrast to the first component 202 from FIG. 3, the first component 302 is constructed with five layers and has, in addition to the layers 302a, 302b, 302c formed before, in addition two further relatively soft outer layers 302d, 302e. The relatively soft layers 302d, 302e are composed of the same material as the relatively soft layer 302a and are therefore more deformable than the relatively rigid layers 302b, 302c. The layers are also of asymmetrical design here with respect to their thickness, wherein, in particular, the relatively rigid layer 302c is thinner than the relatively rigid layer 302b. As a result, it is in turn ensured that the relatively soft layers 302a, 302d are arranged in such a way that a largest possible part of the part of the weld nugget 306 located in the first component 302 is constructed in two of the three relatively soft layers 302a, 302d.