Metal strip and method of manufacturing such metal strip - Patent application

Abstract

A metal strip (1, 101, 201) and a method for manufacturing such a metal strip (1, 101, 201) are presented. It is proposed that a stable metal strip (1, 101, 201) can be reproducibly manufactured by mainly extending a butt weld (5) between a first cladding layer (3b) of a first strip cross-section (2a) and a second strip cross-section (2b).

Description

[Technical Field]

[0001] The present invention relates to a metal strip and a method for manufacturing such a metal strip. [Background technology]

[0002] For the production of hybrid metal strips for electronic applications, in which two metal strips made of different base metals, such as aluminum and copper, are joined together longitudinally, it is known to butt-weld the two metal strips together on their longitudinal sides.

[0003] The formation of unfavorable intermetallic phases from the melt can lead to poor weld stability or quality and can also jeopardize the mechanical reliability of the metal strip during further processing. Furthermore, these intermetallic phases in the structure reduce the electrical conductivity, thereby reducing the use of the metal strip for the manufacture of electrically conductive parts. These parts also show reduced durability.

[0004] To minimize the formation of such unfavorable intermetallic phases, complex welding methods, such as ultrasonic welding or friction stir welding, are known, but such joining methods are not suitable for series production.

[0005] Instead of welding, it is also known to join metal strips comprising different base metals to one another by material bonding using a cladding method. The disadvantage is that this rolled cladding method has limitations with regard to the strength of the joining partners, namely in particular the tensile strength (R m Since it is impossible or almost impossible to clad metal strips made of copper or copper alloys with a strength of ≥ 360 MPa, it is necessary to perform welded joints on these metal strips, even with all the defects in the weld zone. Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is therefore to modify the metal strip described above, which is made of two metal strips made of different base metals joined together in the longitudinal direction, in such a way that it is possible to achieve a relatively high mechanical stability and / or a high electrical conductivity without limiting the strength.

[0007] Furthermore, it is an object of the present invention to provide a method for producing such metal strips reproducibly, conveniently and / or inexpensively. [Means for solving the problem]

[0008] The present invention solves the problem set out in relation to metal strips by the features of claim 1.

[0009] When a first metal strip has a first cladding layer made of copper or a copper alloy disposed on a first substrate at least along its longitudinal edges, a mechanically and / or electrically reliable material bond can be ensured between a first strip cross-section having a first substrate made of aluminum or an aluminum alloy and a second strip cross-section having a second substrate made of copper or a copper alloy with a strength of >360 MPa. That is, due to the multilayer structure of the longitudinal edges or sides of the first metal strip, the cladding layer provides the possibility of a butt weld extending primarily between the first cladding layer of the first strip cross-section and the second strip cross-section, thereby eliminating or negligible concerns about unfavorable intermetallic phases in the butt weld. Therefore, the butt weld does not have brittle phases that reduce strength or electrical conductivity, making the metal strip according to the present invention particularly suitable for electrical components, such as contacts.

[0010] Furthermore, the metal strip according to the invention is not adversely affected by the reduced stability known from other metal strips, thus ensuring a reliable end product. This is especially true when the second strip portion has a relatively high tensile strength (Rm ) ≧360 MPa can be used.

[0011] The metal strip according to the invention is therefore capable of stably combining the most diverse properties of different material groups.

[0012] In particular, if the aluminum alloy has an electrical conductivity of at least 9 MS / m (megaSiemens / m), the metal strip may be suitable for electrical applications. Preferably, the first substrate has an electrical conductivity of at least 18 MS / m.

[0013] The occurrence of this undesirable intermetallic phase can be further reduced if the butt weld extends only between the first clad layer and the second strip cross section, preferably only between the first clad layer and the second substrate layer.

[0014] Preferably, the first strip cross-section has a first strip thickness that is greater than or equal to the second strip thickness of the second strip cross-section, which allows, for example, to use individually adapted semi-finished products for further expansion.

[0015] For example, a high quality butt weld can be achieved when the second strip thickness of the second strip cross-section is equal to or less than the layer thickness of the first clad layer to which it connects.

[0016] It can be determined to be particularly advantageous if the thickness ratio of the first strip thickness of the first strip cross section to the second strip thickness of the second strip cross section is 1:1 to 1:0.2, in particular 1:0.6 to 1:0.7.

[0017] Preferably, the second substrate of the second metal strip or the second strip cross section consists of a hardenable copper alloy. To this end, this second substrate may have a CuNiSi base. Preferably, the second substrate consists of a CuNi1.5Si, CuNi3Si1Mg or CuNi2SiSn alloy.

[0018] Alternatively, the second substrate may consist of a low-alloy copper alloy, such as a CuFe2P alloy.

[0019] It is also conceivable that the second substrate layer consists of a Cu-Sn alloy, ie, for example, a CuSn6 alloy in the cold work hardened state.

[0020] The second metal strip may also have an inorganic coating, preferably formed on the second substrate, such as by hot air leveling with 2-10 μm of tin, or by electroplating with 2-6 μm of tin on a 1-3 μm Ni flash.

[0021] The first clad layer has, for example, a tensile strength (R m ) < 420 MPa, a stable material bond between the first metal strip and the base layer or other layers can be ensured. This is especially true when the first clad layer has a tensile strength (R m )<360 MPa.

[0022] Preferably, the first cladding layer consists of copper, ie for example copper with the material designation EN CW008A.

[0023] Alternatively, the first cladding layer may consist of a low-alloy copper alloy.

[0024] It is further conceivable that the first cladding layer consists of a CuSn alloy, ie for example CuSn6, for example in a softened / annealed state.

[0025] The formation of harmful intermetallic phases can be further suppressed if the cross section of the first strip has recesses at its longitudinal ends that are recessed relative to the cladding layer, which recesses can be configured, for example, as chamfers or grooves.

[0026] Preferably, the first cladding layer and the first base layer are roll-clad, which allows for a relatively stable bond between the cladding layer and the base layer.

[0027] Furthermore, if the butt weld is formed as an I-weld, a stable weld joint can be achieved.

[0028] In particular, the metal strip according to the invention may be suitable as a semi-finished product or raw material for producing, for example by stamping, at least one electrical component, for example an electrical contact.

[0029] The present invention solves the problem set out in relation to a method for producing a metal strip by means of the features of claim 12.

[0030] The first and second metal strips are welded together continuously along their longitudinal sides and at butt joints, primarily by welding the second metal strip butted against the first clad layer. This prevents intermetallic phases, which typically occur when welding dissimilar materials and have a detrimental effect on the stability of the weld. To this end, the first clad layer is provided on the first substrate at least along the longitudinal edges of the first metal strip. The first metal strip thus forms a multilayer structure at its longitudinal edges or longitudinal sides. This, in particular, improves the reproducibility of the method for manufacturing metal strip according to the present invention.

[0031] Preferably, for this purpose, the first metal strip and the second metal strip are continuously welded to one another.

[0032] This reproducibility of the method can be further improved if the second metal strip is only butted against the first cladding layer, and in particular if the second substrate layer is only butted against the first cladding layer.

[0033] The reproducibility of the method for producing a stable metal strip can be further improved if the first and second metal strips are welded together by electron beam welding. The use of a laser for electron beam welding has been found to be particularly advantageous, as it allows for the creation of narrow butt welds and / or a relatively small heat flow zone, further reducing or completely preventing undesirable intermetallic phases.

[0034] Preferably, the first clad layer and the first substrate layer are roll-clad, thereby reproducibly producing a multi-layered first metal strip with high layer cohesion.

[0035] For example, the risk of the first and second substrates intermixing and forming harmful intermetallic phases in the weld can be further reduced by providing the first metal strip with recesses, in particular chamfers or grooves, which are recessed relative to the cladding layer at the longitudinal ends prior to welding.

[0036] The figures show, for example, the subject matter of the invention in more detail on the basis of several embodiment variants. [Brief explanation of the drawings]

[0037] [Figure 1] 1 is a side view of a transversely cut metal strip according to a first embodiment; FIG. [Figure 2] FIG. 10 is a side view of a transversely cut metal strip according to a second embodiment. [Figure 3] FIG. 10 is a side view of a transversely cut metal strip according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION [Example]

[0038] In FIG. 1, for example, a metal strip 1 is shown according to a first embodiment having a first strip cross-section 2a and a second strip cross-section 2b.

[0039] The first strip cross-section 2a is formed by a first metal strip 3, and the second strip cross-section 2b is formed by a second metal strip 4, which are joined to one another by a material bond, in particular by a butt weld 5 which runs along the metal strip 1. This butt weld 5 extends continuously in the longitudinal direction L of the metal strip 1.

[0040] The first metal strip 3 has a first base layer 3a made of an aluminum alloy.

[0041] The second metal strip 4 has a base layer 4a made of a copper alloy and a tensile strength (R m ) ≥ 360 MPa (tensile test according to DIN standard EN ISO 6892-1).

[0042] This relatively high tensile strength of the second metal strip 4 limits joining methods to welding, which can lead to the formation of unfavorable intermetallic phases if the metal strips 3, 4 are of dissimilar base metals, which can unfavorably reduce the strength and / or ductility and / or electrical conductivity of the welded joint and thus reduce the stability of the metal strip 1, e.g., with regard to further processability of the component, preferably by forming, in particular deep drawing.

[0043] This drawback is avoided according to the invention in that the first metal strip 3 is specially designed, i.e. it has a first and outer cladding layer 3b made of copper.

[0044] This first cladding layer 3b is present at least along the longitudinal end 6a or longitudinal side of the first metal strip 3 and is provided on the base layer 3a, so that the first metal strip 3 forms a multi-layer or two-layer structure at this longitudinal end 6a, in which one or more other layers, such as one or more intermediate layers not shown, are conceivable but are not shown.

[0045] 1, the first cladding layer 3b forms a full-surface layer on the first substrate 3a, i.e., on the flat surface of the substrate 3a. The first metal strip 3 is therefore clad on one side. A substrate 3a clad on both sides is also conceivable here, but this is not shown in the figures.

[0046] First, the clad junction between the first substrate layer 3a and the first clad layer 3b avoids harmful intermetallic phases between these layers, despite the dissimilar base metals.

[0047] However, in particular, the first clad layer 3b is made of a copper alloy and has a tensile strength (R m ) ≥ 360 MPa. This is achieved mainly by the butt weld 5 extending between the first cladding layer 3b of the first strip cross-section 2a and the second strip cross-section 2b.

[0048] This avoids unfavorable intermetallic phases at the joint between the two strip cross sections 2a and 2b.

[0049] Furthermore, the first cladding layer 3b greatly simplifies the manufacture of the metal strip 1. Thus, the first and second metal strips can be welded to each other continuously along their longitudinal sides and at butt joints 7, mainly by welding the second metal strip 4, which is butted against the first cladding layer 3b, to the first cladding layer 3b.

[0050] In this way, the mixing of dissimilar base metals in the basic materials 3a, 4b is minimal or can be avoided, so that a stable material bond is achieved between the first metal strip 3 and the second metal strip 4. This is especially the case when the butt weld 5 is formed as an I-weld, as can be seen in Figure 1, and the metal strips 3, 4 are welded by means of a laser-assisted electron beam welding method. The latter can also further simplify the serial production of the metal strip 1 in particular.

[0051] As can be seen in Figure 1, the butt weld 5 extends only between the first cladding layer 3b and the second substrate layer 4a, with the optional layer 4b provided on the second substrate layer 4a being removed from the area of ​​the joining interface prior to joining by material bonding.

[0052] This layer 4b may be, for example, a tin layer having a thickness of 2 to 10 μm. Other layers are also conceivable, for example electroplated layers. Furthermore, it is also conceivable to weld the layers 4b together.

[0053] Preferred material combinations for the metal strip 1 are as follows:

[0054] First strip cross section 2a or first metal strip 3: The first base layer 3a is made of Al99.5 (EN AW-1050A), has a temper of H14 or H24, and an electrical conductivity of 34 to 36 MS / m. The first clad layer 3b is made of Cu-OF (material code: EN CW008A) and has a tensile strength (R m ) 200 to 280 MPa.

[0055] Second strip cross section 2b or second metal strip 4: The second base layer 4a is made of CuNi3Si1Mg and has a tensile strength (R m )620 to 760 MPa. Optional layer 4b is for example a 4 μm thick tin layer.

[0056] The metal strip 1 has, for example, a strip thickness of 0.2 to 3.5 mm, preferably 0.4 to 3 mm, across all strip cross sections 2a, 2b. Furthermore, for example, a total strip width of the metal strip 1 is conceivable of 10 to 250 mm, preferably 40 to 150 mm.

[0057] The first metal strip 3 has a first strip thickness 8 that is greater than a second strip thickness 9 of the second metal strip 4. In a preferred material combination, the thickness ratio of the first strip thickness 8 of the first strip cross-section 2a to the second strip thickness 9 of the second strip cross-section 2b is 1:0.73 to 0.78.

[0058] As can be seen from the examples, the first clad layer 3b has a tensile strength (R m )<420 MPa, which allows for example reproducible roll cladding on the first substrate 3a.

[0059] As can be seen in Figure 1, a recess 10 in the form of a chamfer 10a can be seen at the longitudinal end 6a or longitudinal side. This recess 10 is formed by the first substrate layer 3a being set back relative to the first cladding layer 3b. The first metal strip 3 therefore has an uneven or stepped shape at its longitudinal end 6a. Preferably, this recess 10 is provided in the first substrate layer 3a by a separate process, for example by machining, before the two metal strips 3, 4 are butted together for welding. [Example]

[0060] The metal strip 101 shown in FIG. 2 according to the second embodiment is made from separate metal strips 103 and 104 compared to the metal strip 101 of FIG.

[0061] On the first substrate 3a, the first cladding layer 3b is clad not as a full layer, but in this embodiment as a strip, i.e., on the flat surface of the substrate 3a, with the strip running over the substrate 3a along its longitudinal ends 6a or longitudinal sides.

[0062] Furthermore, the second metal strip 104 also has a thickness variation, with the maximum strip thickness 9 being greater than the layer thickness 8a of the cladding layer 3b. However, the second metal strip 104, i.e. the second substrate layer 4a, is only connected to the first cladding layer 3b. This is especially true because the first substrate layer 3a has recesses 10 in the form of grooves 10b that are set back relative to the first cladding layer 3b, in particular starting from this cladding layer. Therefore, also in this second embodiment, the first metal strip 3 has irregularities or steps at its longitudinal ends 6a.

[0063] This ensures a high stability of the metal strip 101, since no intermetallic and in most cases no brittle phases occur in the butt weld 5. Furthermore, this material bond ensures favorable electrical properties, which is of great importance, especially for electric mobility. [Example]

[0064] According to a third embodiment according to Fig. 3, the metal strip 201 has three strip cross sections 2a, 2b, and 2c. The first strip cross section 2a comprises a first metal strip 203 with a first cladding layer 3b and a second cladding layer 3c. Both cladding layers 3b, 3c, which are identical in material and dimensions, are clad as strips or layers on the flat surface of the first substrate 3a, i.e., along either of the two parallel longitudinal edges 6a, 6b or along the longitudinal sides of the first metal strip 203. In this embodiment, the first metal strip 3a has a flat longitudinal edge 6b and a concave or concave edge 6a.

[0065] In addition to the second metal strip 4 forming the second strip cross-section 2b and butt-welded to the first cladding layer 3b, the metal strip 201 further comprises a third metal strip 205 forming a third strip cross-section 2c.

[0066] This third metal strip 205 is joined to the first metal strip 203 in the same way as the second metal strip 4, or in all embodiments. The third metal strip 205, which has the same second base material 4a as the second metal strip 4, is welded to the second cladding layer 3c by a butt weld 5.

[0067] The third metal strip 205 has a strip thickness 209 smaller than that of the second metal strip 4, and furthermore, only a butt weld is formed between the third metal strip 205 and the cladding layer 3c, so that intermetallic phases and in most cases brittle phases are not generated in the butt weld 5. Therefore, a stable metal strip 201 is produced. [Industrial Applicability]

[0068] This makes metal strips 1, 101 and 201 of this type particularly suitable as semi-finished products or raw materials for electrical contacts such as press-fit terminals, etc. Such metal strips 1, 101 and 201 are often referred to in the prior art as, for example, hybrid metal strips.

Claims

1. A metal strip comprising a first strip cross-section (2a) of a first metal strip (3, 103, 203) having a first base layer (3a) made of aluminum or an aluminum alloy, and a second strip cross-section (2b) of a second metal strip (4, 104), The second metal strip (4, 104) has a tensile strength (R ｍ ) ≥ 360 MPa, in particular ≥ 420 MPa, and having a second substrate layer (4a) made of copper or a copper alloy, said first strip cross-section (2a) being materially bonded to said second strip cross-section (2b) by means of a butt weld (5) running along said metal strip (1), The first metal strip (3, 103, 203) has a first clad layer (3b) made of copper or a copper alloy provided on the first base layer (3a) at least along the longitudinal ends (6a, 6b), and the butt weld (5) extends mainly between the first clad layer (3b) in the first strip cross-section (2a) and the second strip cross-section (2b).

2. 2. Metal strip according to claim 1, characterized in that the first substrate layer (3a) has an electrical conductivity of at least 9 MS / m, in particular at least 18 MS / m.

3. 3. Metal strip according to claim 1 or 2, characterized in that the butt weld (5) extends only between the first cladding layer (3b) and the second strip cross-section (2b), in particular the second base layer (4a).

4. 4. Metal strip according to claim 1, 2 or 3, characterized in that the first strip cross-section (2a) has a first strip thickness (8) that is greater than or equal to a second strip thickness (9) of the second strip cross-section (2b).

5. 5. The metal strip according to claim 4, characterized in that the thickness ratio of the first strip thickness (8) of the first strip cross-section (2a) to the second strip thickness (9) of the second strip cross-section (2b) is between 1:1 and 1:0.2, in particular between 1:0.6 and 1:0.

7.

6. 6. The metal strip according to claim 1, wherein the second substrate layer (4a) consists of a hardenable copper alloy, in particular having a CuNiSi base, for example a CuNi1.5Si, CuNi3Si1Mg or CuNi2SiSn alloy, or a low-alloy copper alloy, in particular a CuFe2P alloy, or a Cu-Sn alloy, in particular a CuSn6 alloy.

7. The first clad layer (3b) has a tensile strength (R ｍ 7. Metal strip according to claim 1, characterized in that it has a tensile strength of <420 MPa, in particular <360 MPa.

8. 8. Metal strip according to any one of claims 1 to 7, characterized in that the first cladding layer (3b) consists of copper, in particular copper with the material designation EN CW008A, or consists of a low-alloy copper alloy, or consists of a Cu-Sn alloy.

9. 9. A metal strip according to claim 1, wherein the first strip cross section (2a) has recesses (10), in particular chamfers (10a) or grooves (10b), recessed relative to the cladding layer (3b) at the longitudinal ends (6a).

10. 10. The metal strip according to claim 1, wherein the first clad layer (3b) and the first base layer (3a) are roll-clad and / or the butt weld (5) is formed as an I-weld.

11. A semi-finished product or raw material consisting of a metal strip (1, 101, 201) according to any one of claims 1 to 10 for at least one electrical component, in particular an electrical contact.

12. A method for continuous production of a metal strip (1, 101, 201) according to any one of claims 1 to 10, comprising: a first metal strip (3, 103, 203) comprising the first base layer (3a) made of aluminum or an aluminum alloy and the first clad layer (3b) made of copper or a copper alloy, the first clad layer (3b) being provided on the first base layer (3a) at least along the longitudinal ends (6a, 6b) of the first metal strip (3, 103, 203); The second metal strip (4, 104) has a tensile strength (Rm) of ≥ 360 MPa, in particular ≥ 420 MPa, and is provided with the second base layer (4a) made of copper or a copper alloy, and is welded to each other continuously on the longitudinal side and at a butt joint, mainly by welding the second metal strip (4, 104) butted against the first clad layer (3b) to this first clad layer (3b).

13. 13. A method according to claim 12, characterized in that the second metal strip (4, 104), in particular the second substrate layer (4a), is butted only against the first cladding layer (3b).

14. 14. Method according to claim 12 or 13, characterized in that the first metal strip (3, 103, 203) and the second metal strip (4, 104) are welded to each other by an electron beam welding method, preferably using a laser.

15. Method according to any one of claims 12 to 14, characterized in that the first cladding layer (3b) and the first base layer (3a) are roll-clad.

16. 16. The method according to any one of claims 12 to 15, characterized in that before the welding, the first metal strip (3, 103, 203) is provided with recesses (10), in particular chamfers (10a) or grooves (10b), which are recessed relative to the first cladding layer (3b) at the longitudinal ends (6a).

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