MULTI-LAYER FLAT STEEL PRODUCT AND COMPONENT PRODUCED THEREFROM

Abstract

A multilayer flat steel product may include a multitude of mutually bonded steel alloy layers. A steel of a first steel alloy may be provided in at least one of the steel alloy layers, and a steel of a second steel alloy different than the first steel alloy may be provided in at least one of the other steel alloy layers. The steel of the first steel alloy may have high strength, and the steel of the second steel alloy may have lower strength and lower carbon content. To enable function-optimized modelling of local material properties in all directions, at least one steel of the first steel alloy and at least one steel of the second steel alloy may be present at least within one layer of the flat steel product. Further, a component, such as for a motor vehicle body, may be comprised of a corresponding flat steel product.

Claims

1.-15. (canceled)

16. A multilayer flat steel product comprising mutually-bonded steel alloy layers, wherein a steel of a first steel alloy is present at least in one of the steel alloy layers, wherein a steel of a second steel alloy different than the first steel alloy is present at least in another of the steel alloy layers, wherein the steel of the first steel alloy is of high strength and the steel of the second steel alloy is of lower strength and lower carbon content, wherein at least one steel of the first steel alloy and at least one steel of the second steel alloy are both present in at least one of the steel alloy layers.

17. The multilayer flat steel product of claim 16 wherein at least one of a carbon content of the steel of the first steel alloy has a value within a range of 0.20%-0.65% by weight, or a carbon content of the steel of the second steel alloy has a value of less than 0.20% by weight.

18. The multilayer flat steel product of claim 16 consisting of an odd number of steel alloy layers.

19. The multilayer flat steel product of claim 16 comprising a core layer consisting of a steel alloy layer comprising the steel of the first steel alloy.

20. The multilayer flat steel product of claim 19 wherein at least one steel alloy layer is disposed on either side of the core layer and consists of at least one steel alloy layer comprising the steel of the second steel alloy.

21. The multilayer flat steel product of claim 19 wherein the core layer accounts for 30-90% of a thickness of the flat steel product.

22. The multilayer flat steel product of claim 16 wherein the at least one steel alloy layer comprising the steel of the first steel alloy and/or the at least one steel alloy layer comprising the steel of the second steel alloy consist(s) entirely of the same steel.

23. The multilayer flat steel product of claim 16 wherein the at least one steel alloy layer comprising the steel of the first steel alloy and/or the at least one steel alloy layer comprising the steel of the second steel alloy has at least one section composed of a steel of the respective other steel alloy.

24. The multilayer flat steel product of claim 23 wherein a section composed of the steel of the first steel alloy adjoins a section composed of the steel of the second steel alloy in a longitudinal direction and/or in a transverse direction and/or in a sheet thickness direction.

25. The multilayer flat steel product of claim 16 wherein all of the steel alloy layers are cohesively bonded to one another by hot rolling.

26. The multilayer flat steel product of claim 16 wherein the first steel alloy consists of a steel, which aside from iron and unavoidable impurities from production contains: 0.2%-0.5% by weight C; 0.15%-0.8% by weight Si; 1.0%-1.9% by weight Mn; 0.002%-0.05% by weight Al; 0.01%-0.5% by weight Cr; 0.0020%-0.5% by weight Ti; and 0.0002%-0.05% by weight B.

27. The multilayer flat steel product of claim 26 wherein a core layer consists of a steel, which aside from iron and unavoidable impurities from production contains: 0.2%-0.45% by weight C; 0.3%-0.6% by weight Si; 1.1%-1.5% by weight Mn; 0.001%-0.04% by weight Al; 0.01%-0.45% by weight Cr; 0.002%-0.2% by weight Ti; and 0.002%-0.01% by weight B.

28. The multilayer flat steel product of claim 16 wherein the second steel alloy consists of a steel, which aside from iron and unavoidable impurities from production contains: up to 0.15% by weight C; up to 0.7% by weight Si; 0.10%-1.9% by weight Mn; up to 0.6% by weight Al; up to 0.6% by weight Cr; up to 0.5% by weight Nb; and up to 0.5% by weight Ti.

29. The multilayer flat steel product of claim 28 comprising two outer layers, wherein at least one of the two outer layers consists of a steel, which aside from iron and unavoidable impurities from production contains: 0.02%-0.11% by weight C; 0.01%-0.6% by weight Si; 0.13%-1.8% by weight Mn; 0.001%-0.2% by weight Al; 0.025%-0.5% by weight Cr; 0.002%-0.2% by weight Nb; and 0.02%-0.3% by weight Ti.

30. A component for a motor vehicle body produced by hot forming or press hardening a multilayer flat steel product that comprises mutually-bonded steel alloy layers, wherein a steel of a first steel alloy is present at least in one of the steel alloy layers, wherein a steel of a second steel alloy different than the first steel alloy is present at least in another of the steel alloy layers, wherein the steel of the first steel alloy is of high strength and the steel of the second steel alloy is of lower strength and lower carbon content, wherein at least one steel of the first steel alloy and at least one steel of the second steel alloy are both present in at least one of the steel alloy layers.

Description

[0045] There is thus a multitude of ways of configuring and further developing the multilayer flat steel product of the invention and the component of the invention. In this regard, reference is made firstly to the further independent claims in addition to claim 1, and secondly to the description of working examples in conjunction with the drawing. The drawings show:

[0046] FIGS. 1a) and b) working examples of a component of the invention in a section view,

[0047] FIGS 1c) and d) views of a working example of a flat steel product of the invention and

[0048] FIG. 2 further working examples of a flat steel product of the invention in a section view.

[0049] FIG. 1a) shows a schematic cross-sectional view of a component 5 for a motor vehicle body, for example a B pillar, produced by hot forming/press hardening of a corresponding flat steel product 1. Examples of flat steel products 1 are shown in FIGS. 1c) and d), and 2.

[0050] FIG. 1b) shows a schematic of another component 5 for a motor vehicle body, for example a main vehicle beam. This component 5 has likewise been produced from an inventive flat steel product 1 in the manner described.

[0051] The component 5 and the underlying flat steel product 1 consist of a multitude of mutually bonded steel alloy layers: a core layer 2, two outer top layers 3a and 3b, and interlayers 4a and 4b that are arranged between each of the top layers 3a and 3b and the core layer 2. The component 5 here thus has a five-layer structure.

[0052] The core layer 2 here consists of a hardenable steel having high strength (in the final state) having a relatively high carbon content, whereas the outer layers 3a and 3b do not consist of a hardenable steel or consist of an only slightly hardenable steel having lower strength, having a lower carbon content than the core layer 2. The interlayers 4a and 4b respectively have both a section 4a.1 and 4b.1 composed of a steel having a relatively low carbon content and a section 4a.2 and 4b.2 composed of a steel having a relatively high carbon content. In the core layer 2 and in the sections 4a.2 and 4b.2 of the interlayers 4a and 4b, the carbon content has a value within a range of, for example, 0.20% to 0.65% by weight and is especially 0.22% by weight. In the outer layers 3a and 3b and in the sections 4a.1 and 4b.1 of the interlayers 4a and 4b, the carbon content has, for example, a value within a range of less than 0.20% by weight and is especially less than 0.15% by weight.

[0053] In the component 5 in FIG. 1a), it is apparent that, in the lower region, only the core layer 2 consists of a hardenable steel having a high carbon content, whereas the other layers 3a, 3b, 4a and 4b in the lower region consist of another steel having lower strength and lower carbon content. The same applies to the left-hand region of the component 5 in FIG. 1b). The remaining region of the respective component 5 (upper region of component 5 in FIG. 1a) and right-hand region of the component 5 in FIG. 1b)) is constructed here in such a way that both the core layer 2 and the interlayers 4a and 4b consist of hardenable steel having a relatively high carbon content, whereas only the outer layers 3a and 3b consist of a steel having lower strength and a lower carbon content.

[0054] It is also apparent that, in the component 5 in FIG. 1a), the core layer 2 is thicker than in the case of the component 5 in FIG. 1b). The thickness ratio in FIG. 1a) (from the outer layer on the left to the outer layer on the right) is, for example, 10:10:60:10:10. The thickness ratio in FIG. 1b) is, for example, (from the upper outer layer to the lower outer layer) 12.5:12.5:50:12.5:12.5.

[0055] In the two working examples, the layer thicknesses of the two outer layers 3a and 3b are identical. The layer thicknesses of the two interlayers 4a and 4b are also identical here. More particularly, the layer thicknesses of the outer layers 3a and 3b are identical to the layer thicknesses of the interlayers 4a and 4b. The statements made above with regard to the layer thicknesses of the respective component 5 apply equally in accordance with the invention to the layer thicknesses of the underlying multilayer flat steel product 1. Here too, it is possible for the outer layers 3a and 3b and/or interlayers 4a and 4b to be of equal thickness and especially to be thinner than the core layer 2.

[0056] FIG. 1c) shows a schematic of a flat steel product 1 in perspective view. FIG. 1d) shows a schematic of a section of component 1 along the section line Id-Id shown in FIG. 1c) (the view in FIG. 1d) is thus in rolling direction or in X direction).

[0057] In the flat steel product 1 in FIGS. 1c) and 1d), it is apparent that, in the transverse direction Y too, a section 4a.1 composed of a steel of a first steel alloy having high strength (in the final state) adjoins a section 4a.2 of a steel of a second steel alloy having lower strength and the latter in turn adjoins another section 4a.1 composed of a steel of the first steel alloy. The same also applies mutatis mutandis to the respective other interlayer 4b.

[0058] In FIG. 1c, it is also apparent that, in the upper layer 3a too, in regions that are unsymmetric here by way of example, sections composed of different steel alloys may be provided. These symmetric or unsymmetric sections may also be provided in one or more other layers, for example in the lower layer 3b.

[0059] Finally, FIG. 2 shows, in schematic form, further variants of a flat steel product 1, it being apparent that both the core layer and each interlayer may each consist of sections of different steel alloys. In this case, some of the sections comprise a hardenable steel having a relatively high carbon content, whereas other sections comprise a steel having a relatively low carbon content. The individual sections of the core layer are identified by “K0 . . . K9”, and the various sections of the interlayers by “Z1.0 . . . Z1.9” and “Z2.0 . . . Z2.9”. The top layers are identified here by “D1” and “D2” and always consist entirely of the same steel alloy.