Dissimilar-Material Joining with Gap-Sealing Weld Structure
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Solution Overview
Problem
Existing joining methods for metal and dissimilar materials are prone to electrolytic corrosion due to moisture ingress at the overlap area, leading to reduced joint strength.
Innovation Solution
A joining method involving the formation of a third member by welding a first filler material to a first member through a through-portion of a second member, and subsequently forming a fourth member by covering the third member with a second filler material and welding it to the second member, effectively closing the gap and preventing moisture ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a filler material is arc-welded through a through-portion of dissimilar material to form a flange, then the dissimilar material and metal material are fixed together by compressive fixing force, but moisture may enter from outside through a gap between the flange and dissimilar material, causing electrolytic corrosion and reducing joint strength
Solution Approach 1:
A seal member is introduced as an intermediary component between the flange and the dissimilar material. This seal member fills the gap that would otherwise allow moisture ingress, while being compatible with both the flange and dissimilar material. The seal member acts as a mediator that prevents electrolytic corrosion without interfering with the compressive fixing force that provides joint strength.
Solution Approach 2:
The joining structure is segmented into distinct functional components: the flange provides compressive fixing force, the seal member prevents moisture ingress, and the weld provides structural bonding. By separating the sealing function from the fixing function, the design can address both joint strength and corrosion prevention independently through specialized components.
2Force
If a flange is formed by solidification shrinkage of filler material, then compressive fixing force is generated to secure the joint, but a gap remains between the flange and dissimilar material that allows moisture entry
Solution Approach 1:
The seal member serves as an intermediary that occupies the gap between the flange and dissimilar material. It is positioned where the compressive force is applied, allowing it to be compressed along with the joint while maintaining its sealing function. This intermediary component enables both the mechanical force transmission and the corrosion barrier functions to coexist.
Solution Approach 2:
The seal member is made of a composite or multi-material structure that combines properties of flexibility (to accommodate compression), sealability (to prevent moisture ingress), and chemical resistance (to withstand the welding and service environment). This composite approach allows a single component to satisfy multiple conflicting requirements.
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 method significantly reduces the occurrence of electrolytic corrosion at the overlap area and enhances the joining strength by ensuring a moisture-tight seal between the second and third members.
Implementation Method 1
the first step includes forming the third member by short-circuit arc welding of the first filler material to the first member
Implementation Method 2
the second step includes forming the fourth member by pulse welding of the second filler material to the second member
Implementation Method 3
welding the second filler material to the second member
Data Source
Figure 1
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AI summary
A second member 20 is made of a material difficult to be welded to a first member 10. A first step includes forming a third member 30 by welding a first filler material 6 to the first member 10 through a through-portion 21 of the second member 20. A second step includes forming a fourth member 40 by covering a surface of the third member 30 with a second filler material 7 and welding the fourth member 40 to the second member 20.