DE102019220107A1 - Process for friction stir welding a first joint partner to a second joint partner - Google Patents

Abstract

The present invention relates to a method (100) for friction stir welding a first joining partner (10) to a second joining partner (16), the first joining partner (10) having a greater material thickness than the second joining partner (16). The method (100) comprises folding (101) the second joining partner (16) to locally increase the thickness of the second joining partner (16) at a joining edge (20), the method (100) furthermore adjusting (102) the geometry of a The joining edge (13) of the first joining partner (10) to the joining edge (20) of the second joining partner (16).

Description

The invention relates to a method for friction stir welding a first joining partner with a second joining partner according to claim 1 and a friction stir welding tool for friction stir welding a first joining partner with a second joining partner according to claim 10.

In principle, it is known from the prior art to connect joining partners of different thicknesses by means of friction stir welding, the joining partners being in particular sheets of different sheet metal thickness.

The EP 1 825 946 A1 describes, for example, a method for joining two sheets of different sheet metal thicknesses by means of friction stir welding. In this case, however, there is a notch in the joining zone, which has a disadvantageous effect.

The object of the present invention is to develop a method for friction stir welding a first joining partner with a second joining partner of different material thicknesses in such a way that a notch effect in a joining zone is prevented, while at the same time the material and weight costs are minimized. Furthermore, the risk of corrosion, for example due to a joint gap, is to be reduced.

The aforementioned object is achieved by a method for friction stir welding a first joining partner to a second joining partner, the first joining partner having a greater material thickness than the second joining partner. The joining partners are preferably both made of metal. Furthermore, the joining partners can both be made of ceramic or plastic. In particular, both joining partners are primarily designed in the form of sheet metal. Both joining partners are mainly sheet metal, whereby the term “material thickness” is understood to mean the sheet metal thickness.

The method includes bending the second joining partner to locally increase the thickness of the second joining partner at a joining edge of the second joining partner. The term “joining edge” is to be understood in particular as a longitudinal edge of the second joining partner on which it is to be connected to a corresponding joining edge of the first joining partner by means of friction stir welding. Because the first joining partner has a greater material thickness than the second joining partner, there is a difference in the available material at the joining edge without the folding, which leads to a notch effect if friction stir welding is nevertheless carried out. The present method provides for bending the second joining partner in order to increase the thickness locally at the joining edge. In particular, as a result of the folding, the thickness of the second joining partner at the joining edge is essentially adapted to the material thickness of the first joining partner. The term “folding” is to be understood in particular as bending, in other words, deforming, of the second joining partner.

In particular, the first joining partner has a constant material thickness. The same applies in particular to the second joining partner, except for a locally increased thickness at the joining edge. In other words, the second joining partner has a first material thickness and a second, increased material thickness at the joining edge.

The method further comprises adapting the geometry of the joining edge of the first joining partner to the joining edge of the second joining partner. Due to the folding of the second joining partner, the joining edge is not flat over the entire local increased thickness. This relates in particular to the thickness direction of the second joining partner. The method includes, in particular, the frontal approach of the first joining partner and the second joining partner until the joining edge of the first joining partner rests against the joining edge of the second joining partner. Due to the adapted geometry of the joining edge of the first joining partner, the two joining partners are in contact with one another over the entire locally increased thickness. Despite the uneven formation of the joining edge of the second joining partner, this is ensured by adapting the geometry of the joining edge of the first joining partner. The joining edge thus in particular forms a contact surface between the various joining partners, with the adaptation of the geometry of the joining edge of the first joining partner ensuring that contact is ensured over the entire area of the locally increased thickness. The joining edge is preferably an abutting edge.

The joining edge of the first and / or the second joining partner is preferably designed in such a way that the joining edge is continuous along the entire material thickness or locally increased thickness and has no kinks.

By adapting the first joining partner to the beveled joining edge of the second joining partner, a material deficit in the joining zone is avoided. The material deficit would result from the bending of the joining partner and thus the uneven formation of the joining edge. In other words, the material of the second joining partner does not extend along the entire locally increased thickness up to the just formed joining edge of the first joining partner.

Preventing a material deficit results in better mechanical-technological and electrical connection properties of the connection made between the two joining partners. This creates a cohesive joint connection between the joint partners of different material thicknesses without a notch effect occurring. Furthermore, the occurrence of a joint gap, which leads to an increased risk of corrosion, is avoided, and additional material expenditure for realizing the locally increased thickness is minimized by the folding.

The term “friction stir welding” means in particular that a friction stir welding tool, in particular its pin, penetrates the joint partners to be joined, the pin rotating and the material of the joint partners heating up to below the melting point. The rise in temperature results in a drop in yield stress, so that the material is plasticized and mixing in a joining zone is possible. The pin is then moved by means of a feed movement along the entire length of the welded connection to be made or along the joining line. The adjacent joining edges form the joining line.

The geometry of the first joining edge is adapted in particular in such a way that a geometric counterpart to the joining edge of the second joining partner is formed. In particular, the geometry of the first joining edge is achieved by milling the first joining partner.

In particular, the second joining partner is simply folded at right angles so that the joining edge of the second joining partner is rounded on one side. The term a right-angled fold is to be understood in particular as a fold by 90 °, so that the second joining partner forms an L-profile. In other words, this is an edge-side folding. The term “simply folded at right angles” means that the second joining partner is only folded once at right angles.

The term “rounded on one side” means that the joining edge is rounded on one side in the direction of the thickness. In particular, the joining edge has an upper region and a lower region in the direction of the thickness, the joining edge being angled in the upper region or in the lower region. In the other area, the joining partner is flat, in other words parallel to the thickness direction. In other words, the joining edge of the second joining partner is convex on one side. The joining edge therefore has a convex shape in the upper area or in the lower area. In particular, the upper area and / or the lower area comprises a maximum of 10%, more preferably a maximum of 20%, particularly preferably a maximum of 50%, of the locally increased thickness.

The joining edge of the first joining partner is adapted in particular in such a way that the joining edge of the first joining partner is concave on one side. The joining edge of the first joining partner thus forms a geometric counterpart to the joining edge of the second joining partner. Due to the concave design, especially when the joining edge of the first joining partner is in contact with the joining edge of the second joining partner, the material deficit caused by the folding is compensated so that the two joining edges can rest against one another along the entire locally increased thickness. The term “concave on one side” means that the joining edge forms a concave shape on one side, preferably in an upper area or a lower area.

Alternatively, the second joining partner can be folded twice at right angles so that the joining edge of the second joining partner is rounded on both sides. In other words, the joining edge of the second joining partner is convex on both sides. With a double right-angled fold, a U-profile of the second joining partner is created at the joining edge, so that the joining edge is rounded on both sides in the thickness direction. In particular, the joining edge is rounded, in particular convex, in an upper area and a lower area. In other words, the joining edge is convex along the entire thickness. In such a case, the joining edge of the first joining partner is adapted in particular in such a way that the joining edge of the first joining partner is concave on both sides. In other words, the joining edge of the first joining partner is concave on both sides in the thickness direction, in particular in an upper area and a lower area. In particular, the joining edge is concave along the entire locally increased thickness. In this way, with a double fold, it is achieved that the two joining edges can rest against one another along the entire locally increased thickness.

In particular, the first joining partner is formed from aluminum or an aluminum alloy, while the second joining partner is formed in particular from copper or steel or a copper alloy or a steel alloy.

This ensures that materials with a high mass density, such as copper, can be substituted by materials with a lower mass density, such as aluminum. This is particularly advantageous in the field of electromobility, in which the aim is to implement weight-reduced components with locally adapted properties. Since copper in the Compared to the joining partner aluminum, depending on the alloy composition, has an electrical conductivity that is up to 1.7 times higher, a corresponding adjustment of the thickness or sheet thickness is necessary to maintain the electrical conductivity. Here, the present invention allows an optimal connection between the joining partners of different sheet metal thicknesses without a notch effect and with a reduction in the risk of corrosion. Overall, due to the density of copper that is around 3.3 times higher than that of aluminum for pure materials, a considerable reduction in the weight of the connections achieved can be achieved.

The present method is used in particular to establish connections between electrical contacts in the field of electromobility. Thus, the joining partners are in particular electrical contacts of high-voltage connectors of battery modules or cell connectors of lithium-ion cells. Furthermore, the present method can be used in the body shop for the production of hybrid plates with locally adapted mechanical properties, in particular aluminum-steel hybrid plates. Weight-reduced connections can thus be established so that the vehicle weight can be reduced overall.

In a further aspect, the present invention relates to a friction stir welding tool for friction stir welding a first joint partner to a second joint partner, the friction stir welding tool comprising a pin for penetrating the first and second joint partners in the area of the corresponding joint edges. This happens in particular after the joining edges have been brought closer together in such a way that they rest against one another. The friction stir welding tool can furthermore have a shoulder for resting on an upper side of the first and second joining partners. The top is mainly turned towards the shoulder.

The pin of the friction stir welding tool has a bi-concave contour in the longitudinal direction at least in an upper area. The tool geometry is thus adapted to the joining edge of the second joining partner. In other words, the pin follows the bevel angle. This ensures that the connection area is constant along the entire locally increased thickness after welding.

In particular, the width of the pin does not increase from a first end on the shoulder of the friction stir welding tool to a second free end. The width of the pin can decrease in the upper area according to a bi-concave contour, whereby it can remain constant or can decrease further in a lower area, in particular in the entire remaining area of the pin. Most importantly, the width of the pen at the first end corresponds to the width of the shoulder.

The friction stir welding tool is designed in particular to carry out a method described above.

• 1 eine Anordnung eines ersten Fügepartners und eines zweiten Fügepartners gemäß einem Verfahren zum Rührreibschweißen nach dem Stand der Technik;
• 2 Verfahrensschema des erfindungsgemäßen Verfahrens;
• 3 einen ersten Fügepartner und einen zweiten Fügepartner gemäß einem erfindungsgemäßen Verfahren;
• 4 eine Anordnung des ersten Fügepartners und des zweiten Fügepartners aus 3 gemäß einem erfindungsgemäßen Verfahren zum Rührreibschweißen; und
• 5 die Anordnung aus 4 unter Einsatz eines erfindungsgemäßen Rührreibschweißwerkzeuges.

They show schematically:

• 1 an arrangement of a first joining partner and a second joining partner according to a method for friction stir welding according to the prior art;
• 2 Process scheme of the process according to the invention;
• 3 a first joining partner and a second joining partner according to a method according to the invention;
• 4th an arrangement of the first joining partner and the second joining partner 3 according to a method according to the invention for friction stir welding; and
• 5 the arrangement 4th using a friction stir welding tool according to the invention.

Detailed description of the drawings

1 shows an arrangement of a first joining partner 10 and a second joining partner 16 according to a procedure 100 for friction stir welding according to the state of the art.

The first joining partner 10 has a higher material thickness 11 on as the second joining partner 16 that has a material thickness 17th having. The second joining partner 16 is bevelled so that a locally increased thickness 18th is reached that of the material thickness 11 of the first joining partner 10 corresponds to. During the joining edge 13th of the first joining partner in the direction of the thickness 70 , in other words parallel to the thickness direction 70 , is formed, is the joint edge 20th of the second joining partner 16 not exactly. It's in an upper area 21 rounded while he is in a lower area 22nd is flat. This creates a material deficit 71 at the joint edge 20th of the second joining partner 16 , which leads to disadvantages of the connection to be achieved, in particular to a notch effect. Furthermore, in 1 a friction stir welding tool 50 seen with one shoulder 51 and a pen 53 , with the pen 53 is cylindrical.

2 shows a process scheme of the process according to the invention 100 .

The procedure 100 includes folding 101 of the second joining partner 16 to the local Increase in the thickness of the second joining partner 16 at a joining edge 20th of the second joining partner 16 . The method also includes 100 customizing 102 the geometry of a joining edge 13th of the first joining partner 10 to the joining edge 20th of the second joining partner 16 . In particular, there is a geometric counterpart to the joint edge 20th of the second joining partner 16 formed 103. The method also includes 100 the frontal approach 104 of the first joining partner 10 and the second joining partner 16 and thus a mooring 105 of the joining edge 13th of the first joining partner 10 to the joining edge 20th of the second joining partner 16 over the entire locally increased thickness 18th .

3 shows a first joining partner 10 and a second joining partner 16 according to a method according to the invention 100 .

The first joining partner 10 with a top 12th has a material thickness 11 in the thickness direction 70 on. Furthermore, the second joining partner 16 with a top 19th a material thickness 17th on. In order to adjust the different material thicknesses to one another, the second joining partner 16 bevelled so that a locally increased thickness 18th at a joining edge 20th arises. This is the joining edge 20th rounded on one side or convex on one side, namely it is in an upper area 21 rounded, while in a lower area it is flat in relation to the thickness direction 70 is trained.

To a possible material deficit 71 (please refer 1 ) The geometry of the joint edge is to be avoided during friction stir welding 13th of the first joining partner 10 to the joining edge 20th of the second joining partner 16 that is created by the fold. And that is the joint edge 13th of the first joining partner 10 Concave on one side, also in an upper area 14th while he's in a lower area 15th also just to the thickness direction 70 is trained. Due to the special geometry of the first joining partner 10 it is ensured that when the two joining edges approach, they are along the entire locally increased thickness 18th lie against each other and thus a joint gap or a notch effect is prevented.

In 4th is an arrangement of the first joining partner 10 and the second joining partner 11 out 3 according to a method according to the invention 100 to see for friction stir welding. You can see in detail how the first joining partner 10 and the second joining partner 16 via a friction stir welding tool 50 with one shoulder 51 and a pen 53 be connected to each other. The pencil 53 becomes in the thickness direction 70 retracted into the area where the two joining edges touch. There is no material deficit 71 in an upper area 21 of the joining edge 20th of the second joining partner 16 because there is the upper area 14th of the joining edge 13th of the first joining partner 10 extends.

In 5 is the same arrangement according to 4th shown, with a friction stir welding tool according to the invention 50 with one shoulder 51 and a pen 53 is used.

The top 12th of the first joining partner 10 and the top 19th of the second joining partner 16 are the shoulder 51 facing. The longitudinal direction 54 of the pen 53 corresponds to the thickness direction 70 . The pencil 53 has a first end 55 on the shoulder 51 and a free second end 57 on. The pencil 53 has a width 56 at the first end 55 on that of the breadth 52 the shoulder 51 corresponds to, and a width 58 at the second end 57 . The pencil 53 points in the longitudinal direction 54 a bi-concave contour. In other words, it is due to the convex geometry of the first joining partner 16 customized. In particular, the pen is divided 53 in an upper area 59 and a lower area 60 , where he is in the upper area 59 Is concave and thus a geometric counterpart to the joining edge 20th of the second joining partner 16 forms.

List of reference symbols

100

Procedure

101

Bending the second joining partner to locally increase the thickness of the second joining partner at a joining edge of the second joining partner

102

Adapting the geometry of a joining edge of the first joining partner to the joining edge of the second joining partner

103

Forming a geometric counterpart to the joining edge of the second joining partner

104

frontal approach of the first and the second joining partner

105

Applying the joining edge of the first joining partner to the joining edge of the second joining partner over the entire locally increased thickness

10

first joining partner

11

Material thickness

12th

Top

13th

Joining edge

14th

upper area

15th

lower area

16

second joining partner

17th

Material thickness

18th

locally increased thickness

19th

Top

20th

Joining edge

21

upper area

22nd

lower area

50

Friction stir welding tool

51

shoulder

52

Width of the shoulder

53

pen

54

Longitudinal direction of the pen

55

first end of the pen

56

Width at the first end

57

second end of the pen

58

Width at the second end

59

upper area of the pen

60

lower area of the pen

70

Thickness direction

71

Material deficit

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 1825946 A1 [0003]

Claims (10)

Method (100) for friction stir welding a first joining partner (10) to a second joining partner (16), the first joining partner (10) having a greater material thickness than the second joining partner (16), characterized in that the method (100) involves folding (101) of the second joining partner (16) for locally increasing the thickness of the second joining partner (16) at a joining edge (20), the method (100) adapting (102) the geometry of a joining edge (13) of the first joining partner ( 10) on the joining edge (20) of the second joining partner (16). Method (100) according to Claim 1 , characterized in that the joining edge (20) is not flat over the entire locally increased thickness (18) due to the folding (101) of the second joining partner (16), the method (100) approaching (104) the end face of the first Joining partner (10) and the second joining partner (16) until the joining edge (13) of the first joining partner (10) rests against the joining edge (20) of the second joining partner (16), whereby the adapted geometry of the joining edge (13) of the first joining partner (10), the two joining partners rest against one another over the entire locally increased thickness (18). Method (100) according to one of the Claims 1 or 2 , characterized in that the geometry of the joining edge (13) of the first joining partner (10) is adapted in such a way that a geometric counterpart to the joining edge (20) of the second joining partner (16) is formed. Method (100) according to one of the preceding claims, characterized in that the second joining partner (16) is simply folded at right angles so that the joining edge (20) of the second joining partner (16) is rounded on one side. Method (100) according to Claim 4 , characterized in that the joining edge (13) of the first joining partner (10) is adapted in such a way that the joining edge (13) of the first joining partner (10) is concave on one side. Method (100) according to one of the preceding claims, characterized in that the second joining partner (16) is folded twice at right angles so that the joining edge (20) of the second joining partner (16) is rounded on both sides. Method (100) according to Claim 6 , characterized in that the joining edge (13) of the first joining partner (10) is adapted in such a way that the joining edge (13) of the first joining partner (10) is concave on both sides. Method (100) according to one of the preceding claims, characterized in that the first joining partner (10) is formed from aluminum or an aluminum alloy. Method (100) according to one of the preceding claims, characterized in that the second joining partner (16) is formed from copper, a copper alloy, steel or a steel alloy. Friction stir welding tool (50) for friction stir welding a first joining partner (10) to a second joining partner (16), the friction stir welding tool (50) having a pin (53) for penetrating into the first joining partner (10) and the second joining partner (16) in the area of the comprises corresponding joining edges, characterized in that the pin (53) has a bi-concave contour in the longitudinal direction (54) at least in an upper region (59).

Images