METHOD FOR PRODUCING A HOT-ROLLED PLATED COMPOSITE MATERIAL, FLAT PRODUCT STACK, HOT-ROLLED PLATED COMPOSITE MATERIAL AND USE THEREOF

Abstract

A method for producing a hot-rolled clad composite material may involve cleaning surfaces of multiple flat products, at least one surface of which has a natural unevenness. The cleaned surfaces may then be connected and brought into contact by stacking the flat products. The flat products may then by regionally welded to create a flat product package. The method may further involve heating the flat product package to an initial hot-rolling temperature, hot-rolling the flat product package to form a hot strip, and either cutting the hot strip into plates or sheets or coiling the hot strip to form a coil.

Claims

1.-13. (canceled)

14. A method for producing a hot-rolled clad composite material, the method comprising: providing a first flat product and a second flat product that is different than the first flat product with respect to at least one property, wherein a surface of the first flat product comprises a natural unevenness; cleaning the surface of the first flat product with the natural evenness and a surface of the second flat product; stacking the first and second flat products on top of one another, wherein the surface of the first flat product with the natural evenness and the surface of the second flat product are connected such that the first and second flat products are in contact regionally in a connecting plane via the surfaces of the first and second flat products; at least regionally welding the first and second flat products to create a flat product package; heating the flat product package to an initial hot-rolling temperature; hot-rolling the flat product package to form a hot strip; and cutting the hot strip into plates or sheets or coiling the hot strip to form a coil.

15. The method of claim 14 wherein a sum of an area of the first and second flat products regionally in contact corresponds to at least 30% in the connecting plane.

16. The method of claim 14 wherein a sum of an area of the first and second flat products regionally in contact corresponds to at least 45% in the connecting plane.

17. The method of claim 14 wherein after the stacking, as a result of the natural unevenness of the surface of the first flat product, air gaps are formed at least regionally between the first and second flat products, which take up a total area of at least 20% in the connecting plane.

18. The method of claim 14 comprising cleaning the surface of the first flat product with the natural unevenness such that the natural unevenness is preserved.

19. The method of claim 14 comprising welding the first and second flat top products together in a gastight manner.

20. The method of claim 14 wherein the first and second flat products are comprised of steel.

21. The method of claim 14 wherein the first and second flat products are comprised of an aluminum alloy.

22. The method of claim 14 comprising rolling the hot-rolled clad composite material to form a cold strip.

23. A flat product package comprising: a first flat product with a surface that includes a natural unevenness; a second flat product that is different from the first flat product with respect to at least one property, wherein a surface of the second flat product is connected to the surface of the first flat product such that the first and second flat products are in contact regionally in a connecting plane, wherein air gaps are included at least regionally between the first and second flat products; and a weld by which the first and second flat products are welded together in a gastight manner.

24. The flat product package of claim 23 wherein a sum of areas where the first and second flat products are regionally in contact corresponds to at least 30% in the connecting plane, wherein a total area where the air gaps are present occupies at least 20% in the connecting plane.

25. A hot-rolled clad composite material comprising: a first layer; a second layer that is different from the first layer with respect to at least one property, the first and second layers being connected together at least regionally via a connecting region produced by hot-rolling the flat product package of claim 23; and oxidic particles disposed at least regionally in the connecting region.

26. The hot-rolled clad composite of claim 25 wherein oxidic particles are disposed in the connecting region in a proportion of between 0.05% and 20%.

27. The hot-rolled clad composite of claim 25 configured as a hot strip in a form of a plate, a sheet, or a coil, wherein a thickness of the hot strip is less than 26 mm.

Description

[0024] In the following text, the invention is explained in more detail with reference to a drawing illustrating exemplary embodiments. Identical parts are provided with identical reference signs. In the drawing

[0025] FIG. 1) shows a flow diagram of an exemplary embodiment of a method according to the invention for producing a hot-rolled clad composite material,

[0026] FIG. 2a) shows an exemplary embodiment of a flat product package according to the invention in a schematic, perspective view,

[0027] FIG. 2b) shows a partial section through the region indicated in FIG. 2a),

[0028] FIG. 3a) shows a schematic longitudinal section through an exemplary embodiment of a hot-rolled clad composite material according to the invention, and

[0029] FIG. 3b) shows a partial section through the region indicated in FIG. 3a).

[0030] FIG. 1) illustrates a flow diagram of an exemplary embodiment of a method according to the invention for producing a hot-rolled clad composite material. At least two flat products preferably made of a steel material, which are formed in a cuboidal manner in the form of cast slabs, prerolled slabs, blooms, plate blanks or strip blanks, are provided, wherein the flat products differ from one another with regard to at least one property (tensile strength, hardness and/or elongation at break) [step A]. The first and/or the second provided flat product comprises, at least on one of its surfaces, a natural unevenness, which is intended to be connected to another surface of a flat product, which can likewise be embodied as a natural surface, during hot-roll cladding. The surface with a natural unevenness can be set for manufacturing reasons with a surface structure (roughness and/or waviness) and does not comprise a planar surface. Alternatively or additionally, it is also possible for surfaces with a natural unevenness to be set in a targeted manner with a surface structure.

[0031] At least those surfaces of the first and/or of the second flat product that are to be connected are cleaned, in order to remove the layer of rust that has formed on the surface for example while the flat products are being stored, and optionally other disruptive particles located on the surface. Cleaning is carried out in this case such that the natural unevenness of the surface is substantially preserved [step B].

[0032] Following cleaning, the first and the at least second flat product are stacked on top of one another, wherein the first and/or the second flat product having the at least one surface with the natural unevenness is oriented prior to stacking such that this surface is brought into contact with the surface of the other flat product, wherein, following stacking, the flat products are in contact regionally in a connecting plane via their surfaces [step C].

[0033] Following stacking, the individual flat products are welded together at least regionally to produce a flat product package. Preferably, the flat products are welded together in a gastight manner in order to prevent exchange or penetration of furnace atmosphere between the flat products during subsequent heating of the flat product package [step D].

[0034] The flat product package is heated or through-heated to at least an initial hot-rolling temperature, for example in a walking beam furnace at for example temperatures of between 1100 and 1300 C. [step E]. Since the flat products are in contact only regionally in a connecting plane (contact points or contact regions) and the rest of the connecting plane consists of included air gaps, a thin oxide layer forms through or in the included air gaps at the prevailing temperatures.

[0035] Once the at least initial hot-rolling temperature has been reached, the flat product package is rolled, following a particular pass sequence, to form a hot strip, which forms the hot-rolled clad composite material [step F]. The oxide layer that has arisen on account of the heating cannot be deformed during the hot-roll cladding, but ruptures on account of the deformation by rolling by elongation of the hot-rolled clad composite material to be produced and is deposited locally in the form of oxidic particles in the rolling direction and across the width of the rolled material in the connecting region or in the connecting regions between the layers. The formed oxide layer or particles can regionally suppress diffusion during and/or after rolling and thus full mixing of the properties in the connecting region or in the connecting regions between layers can be prevented.

[0036] Following completion of rolling, the hot strip is either cut to length to form plates or sheets [step G] or coiled to form a coil [step G] and made available to the processing industry. The hot strip can if necessary be rolled to form a cold strip.

[0037] FIG. 2a) illustrates an exemplary embodiment of a flat product package (1) according to the invention in a schematic, perspective view, wherein the flat product package (1) has been produced for example by the abovementioned method steps [A]-[D]. The flat product package (1) consists of three flat products (2, 3, 4). The flat product (3) is for example a slab that has a thickness of 220 mm and is made of a for example ductile steel material with a C content of less than 0.15% by weight, and acts as the core of the flat product package (1). The core (3) is covered by two flat products (2, 4) that have in each case for example a thickness of 30 mm and are made in each case of a for example heat-treatable steel material having a C content of more than 0.2% by weight, resulting in an overall thickness of 280 mm. The flat products (2, 3, 4) have been welded together in a gastight manner via a weld (5), wherein the weld (5) can also comprise a plurality of weld seams. The partial view in FIG. 2b) shows that at least one, preferably both of those surfaces (O.sub.2, O.sub.3) of the flat products (2, 3) that are assigned to one another and are to be connected comprise a natural unevenness and as a result the flat products (2, 3) are in contact (K) regionally in a connecting plane (V) and as a result at least regionally included air gaps (L) are present between the flat products (2, 3). The sum of the areas of the flat products (2, 3) that are regionally in contact (K) corresponds to at least 30%, in particular at least 35%, preferably at least 40%, particularly preferably at least 45% in the connecting plane (V) and the included air gaps (L) regionally present between the flat products (2, 3) take up a total area of at least 20%, in particular at least 25%, preferably at least 30%, particularly preferably at least 35% in the connecting plane (V). By means of the natural unevenness on at least one of the surfaces (O.sub.2, O.sub.3) of the flat products (2, 3), the included air gaps (L) can regionally comprise a gap size (S) between the surfaces (O.sub.2, O.sub.3) of up to 5 mm. Those surfaces of the flat products (3, 4) that are assigned to one another and are to be connected likewise each comprise a natural unevenness and correspond substantially to the configurations of the surfaces (O.sub.2, O.sub.3), not illustrated here.

[0038] The flat products (2, 3, 4) can of course also comprise other thicknesses, in particular also other thickness ratios. For example, an asymmetric structure is also conceivable. Depending on the application, the flat product package can be constructed individually. For example, a heat-treatable steel material having a C content of over 0.2% by weight can be used as the core and two steel materials that each have a C content of less than 0.15% by weight can be used as outer layers for constructing the flat product package.

[0039] FIG. 3a) illustrates an exemplary embodiment of a hot-rolled clad composite material (1) according to the invention in a schematic longitudinal section. The flat product package (1), shown in FIG. 2a), having the individual flat products (2, 3, 4) has been heated, cf. description for method step [E], and rolled to form a hot strip with a thickness (d)<26 mm, particularly preferably <10 mm, cf. description for method step [F]. The rolled clad composite material (1) also comprises substantially three layers (2, 3, 4). The scale layer that has arisen in the included air gaps (L) as a result of the heating cannot be deformed during hot-roll cladding, but ruptures as a result of the pressure action by rolling in conjunction with a thickness reduction and, associated therewith, an elongation of the hot-rolled clad composite material to be produced, and is deposited in the form of oxidic particles (P) locally in the rolling direction and locally across the width of the rolled material in the connection regions (V) between the layers (2, 3) and (3, 4), as shown in the enlarged detail in FIG. 3b). The particles (P) in the connecting region (V) or in the connection regions are present with a proportion by area of between 0.05% and 20%, in particular between 0.3% and 5%. The oxidic particles (P) do not have a negative effect on the formation of the connecting region (V) during hot-roll cladding.

[0040] Hot-rolled clad composite materials (1) according to the invention can be used everywhere in sectors in which lightweight construction is pursued, for example in vehicle construction, railroad construction, shipbuilding or aerospace. It can also be used in sectors with wear influences, in the construction sector, in plant engineering and mechanical engineering.

[0041] The invention is not limited to the exemplary embodiments illustrated in the drawing or to the configurations in the general description, but rather, in addition to plate-form or slightly deformed, for example deep-drawn semifinished products, it is also possible for closed profiles with for example a circular cross section to be produced from hot-rolled clad composite materials according to the invention, such that even sectors with abrasively acting media routing, for example pipelines for delivering liquid concrete etc., can be served appropriately.

LIST OF REFERENCE SIGNS

[0042] 1 Flat product package [0043] 1 Hot-rolled clad composite material, hot strip [0044] 2, 3, 4 Flat product [0045] 2, 3, 4 Layers [0046] 5 Weld [0047] A, B, C, D, E, F, G, G Method steps [0048] d Thickness [0049] K Contact, contact region [0050] L Included air gap [0051] O.sub.2, O.sub.3 Surface with natural unevenness [0052] P Oxidic particles [0053] S Gap size [0054] V Connecting plane [0055] V Connecting region