Sealed Welded Joint Structure for Corrosion-Resistant Dissimilar Metals
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Solution Overview
Problem
Existing joint structures between dissimilar metal materials are prone to electrolytic corrosion due to moisture ingress through gaps, leading to decreased joint strength.
Innovation Solution
A joint structure design featuring a recessed area around the overlap with a sealing material to close gaps, allowing for moisture exclusion and incorporating communication paths for gas release during welding, enhancing sealing and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a through-portion is created in the second member for welding the third member through it, then the third member can be welded to the first member, but moisture can enter through the gap between overlapped surfaces causing electrolytic corrosion
Solution Approach 1:
The overlapped surface is segmented into a sealing surface and a non-sealing surface. The sealing surface includes a recess that is separated from the through-portion, creating distinct functional zones. This segmentation allows the recess to provide sealing while the through-portion maintains weldability.
Solution Approach 2:
A sealing material is introduced as an intermediary substance placed in the recess. This sealing material mediates between the need for moisture protection and the presence of the through-portion, filling the gap between overlapped surfaces to prevent moisture entry while allowing the welding process to proceed through the through-portion.
2Reliability
If the recess is completely sealed to prevent moisture entry, then corrosion resistance improves, but gas generated during welding has no escape path
Solution Approach 1:
The recess is designed with non-uniform sealing characteristics. The bottom surface and side surfaces facing the gap between overlapped surfaces are sealing surfaces that prevent moisture entry. However, at least one side surface is designated as a non-sealing surface that serves as a gas discharge path. This local quality differentiation allows simultaneous achievement of corrosion resistance and gas venting.
Solution Approach 2:
Instead of making the entire recess sealing or entirely open, the invention inverts the conventional approach by creating selective sealing zones. The recess is sealed in directions where moisture entry occurs (gap between overlapped surfaces) while remaining open in directions where gas escape is needed (side surfaces).
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
Reduces electrolytic corrosion and maintains joint strength by preventing moisture ingress and facilitating gas release, thereby improving the durability of the joint.
Implementation Method 1
the recess is provided with a sealing material to be deformed by heat of welding for for closing a gap between the overlapped surfaces of the first member and the second member
Implementation Method 2
the dissimilar material and the first metal material are fixed to each other by a compressive fixing force between the flange and the first metal material due to solidification shrinkage of the filler material onto the first metal material
Data Source
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AI summary
A second member 20 has a through-portion 21 penetrating toward a first member 10. An overlapped surface of the second member 20 with the first member 10 includes a recess 41. The recess 41 is recessed so as to surround an entire periphery of the through-portion 21. The recess 41 is provided with a sealing material 40. The sealing material 40 closes a gap between overlapped surfaces of the first member 10 and the second member 20.