Clad Metal Strip Butt Welds That Limit Al-Cu Intermetallics
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Solution Overview
Problem
The formation of intermetallic phases during the welding of metal strips made from different base metals, such as aluminum and copper, leads to reduced mechanical stability and electrical conductivity, making them unsuitable for electrotechnical applications, and existing welding methods are not suitable for continuous manufacturing processes.
Innovation Solution
A metal strip is created with a copper or copper alloy plating layer along one longitudinal edge of an aluminum or aluminum alloy base layer, allowing for a butt weld that extends between the plating layer and a copper alloy base layer with a tensile strength greater than 360 MPa, minimizing the formation of intermetallic phases and ensuring a stable and conductive connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional welding methods are used to join aluminum and copper strips, then a material connection is achieved, but disadvantageous intermetallic phases form that reduce mechanical stability and electrical conductivity
Solution Approach 1:
A nickel intermediate layer is introduced between the aluminum strip and copper strip to prevent direct contact and intermetallic phase formation. The nickel layer acts as a diffusion barrier, allowing the aluminum to weld to the nickel and the nickel to weld to the copper, thereby maintaining mechanical strength while preventing harmful intermetallic compounds from forming at the aluminum-copper interface.
Solution Approach 2:
The invention creates a composite structure consisting of three layers: aluminum strip, nickel intermediate layer, and copper strip. This composite material structure combines the advantages of both base metals while using the nickel layer to prevent detrimental interactions, thus achieving both mechanical stability and electrical conductivity without the formation of disadvantageous intermetallic phases.
2Reliability
If expensive welding methods such as ultrasonic welding or friction stir welding are used, then formation of intermetallic phases is minimized, but these methods are not suitable for continuous manufacturing
Solution Approach 1:
The nickel intermediate layer is applied to the aluminum strip in advance, before the welding process. This preliminary action of coating the aluminum with nickel creates a diffusion barrier that prevents intermetallic phase formation during subsequent conventional welding, eliminating the need for expensive specialized welding methods and enabling continuous manufacturing processes.
3Ease of manufacture
If roll cladding is used to bond metal strips with different base metals, then joining is achieved, but it is limited to metal strips with tensile strength below 360 MPa
Solution Approach 1:
The nickel intermediate layer enables the use of conventional welding methods for high-strength copper strips (≥360 MPa) by preventing direct aluminum-copper contact. This intermediary layer allows the welding process to proceed without forming harmful intermetallic phases, thereby extending the applicability of roll cladding and conventional welding to high-strength metal strips that were previously unsuitable for such joining methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides a metal strip with high mechanical stability and electrical conductivity, suitable for electrical components, while avoiding brittle phases that reduce strength and conductivity, and allows for a cost-effective, reproducible manufacturing process.
Implementation Method 1
The first metal strip (3, 103) has a first plating layer (3b) made of copper or a copper alloy which is provided at least along one longitudinal edge (6a) on the first base layer (3a)
Implementation Method 2
a butt weld (5) extending essentially between the first plating layer (3b) and the second transverse strip section (2b)
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Disclosed are a metal strip (1, 101, 201) and a process for manufacturing such a metal strip (1, 101, 201). In order to be able to reproducibly manufacture a rigid metal strip (1, 101, 201), according to the invention, the butt seam (5) substantially extends between the first cladding (3b) of the first strip transverse portion (2a) and the second strip transverse portion (2b).