Sealed Dissimilar-Metal Joint Structure Against Electrolytic Corrosion
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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 reduced joint strength.
Innovation Solution
A joint structure design that includes a recessed area around the overlap with a sealing material to close gaps between dissimilar metal surfaces, allowing for the release of deformed sealing material and gases generated during welding, thereby preventing moisture ingress and enhancing joint strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a through-portion is provided in the second member for welding the third member, then the third member can be welded to the first member through the second member, but moisture can enter from outside through the gap between overlapped surfaces of the first member and second member, causing electrolytic corrosion
Solution Approach 1:
The overlapped surface is divided into a through-portion area (for welding) and a recess area (for sealing). The recess is formed around the periphery of the through-portion, creating distinct functional zones that separate the welding function from the moisture prevention function.
Solution Approach 2:
A sealing material is introduced as an intermediary substance in the recess area to prevent moisture from entering the gap between the first member and second member. This sealing material acts as a barrier that blocks the harmful moisture while allowing the welding operation to proceed through the through-portion.
2Object-affected harmful factors
If a sealing material is provided in the recess to close the gap, then moisture prevention is improved, but the sealing material may deform due to welding heat and trap gases, affecting welding quality
Solution Approach 1:
The recess is designed with an opening that allows the sealing material to dynamically respond to welding heat. When heated during welding, the sealing material can deform and be expelled through the opening, and gases generated by evaporation can escape, preventing pressure buildup that would compromise welding quality.
Solution Approach 2:
The recess provides a three-dimensional space around the through-portion that accommodates the sealing material. This spatial arrangement allows the sealing material to be positioned in a way that it can deform and release gases toward the opening while still effectively sealing the gap when in its initial position.
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 secures joining strength by sealing the gap between dissimilar metal materials, ensuring effective moisture prevention and improved structural integrity.
Implementation Method 1
The recess is provided with a sealing material 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
Implementation Method 3
a filler material (welding wire) is arc-welded through a through-portion of the dissimilar material
Implementation Method 4
Electrolytic corrosion may thus occur in an area where the first metal material and the second metal material overlap each other due to the entry of the moisture
Data Source
AI summary
A second member has a through-portion penetrating toward a first member. An overlapped surface of the second member with the first member includes a recess. The recess is recessed so as to surround an entire periphery of the through-portion. The recess is provided with a sealing material. The sealing material closes a gap between overlapped surfaces of the first member and the second member.