Laser Welding Copper Joint Stainless Steel Cap
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Solution Overview
Problem
Conventional methods for welding copper joints to stainless steel cap members in pressure-sensitive devices face challenges such as environmental pollution from pickling and difficulty in achieving high sealing properties, especially under high pressure conditions.
Innovation Solution
A pressure-sensitive device with a copper joint and stainless steel cap member is welded using a melt-solidified layer of copper, nickel, and iron, formed by laser welding, which securely connects the joint and cap member with high airtightness, eliminating the need for brazing and pickling processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If brazing is used to join copper joint and stainless steel cap member, then the joint can be formed, but pickling is required which causes environmental pollution
Solution Approach 1:
The patent replaces the thermal brazing process with a mechanical press-fit structure. The joint portion of the copper pipe is expanded to increase its outer diameter, creating an interference fit with the stainless steel cap member that eliminates the need for brazing and subsequent pickling operations, thereby resolving the environmental pollution issue while maintaining joint strength
Solution Approach 2:
The patent changes the dimensional parameters of the joint portion by expanding its outer diameter beyond the standard size. This parameter change creates an interference fit condition that enables mechanical joining without thermal processes, avoiding the harmful pickling step while achieving reliable connection
2Strength
If projection pressing welding is used to fix copper and stainless, then welding is possible, but high sealing property against high pressure cannot be achieved
Solution Approach 1:
The patent employs a spherical or rounded expansion of the joint portion outer diameter rather than a sharp projection. This curved interference fit distributes stress more evenly and creates a more reliable seal against high pressure compared to the sharp projection pressing method, while still enabling welding feasibility
3Strength
If nickel plate is arranged between copper and stainless to fix them, then welding is possible, but the process is complex and sealing under high pressure is difficult
Solution Approach 1:
The patent extracts and eliminates the nickel plate intermediate layer from the joining process. By directly expanding the copper joint portion to create an interference fit with the stainless steel cap member, the patent simplifies the structure and process while maintaining welding capability and improving sealing performance under high pressure
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
The solution provides a secure and high-sealing connection between copper and stainless steel components, ensuring reliable pressure detection with improved manufacturing efficiency and reduced environmental impact.
Implementation Method 1
a laser beam is irradiated toward an entire circumference of an outer peripheral edge of the nickel plate around an axis of the joint; melting the nickel plate, a part of the flat portion and a part of the flange portion
Implementation Method 2
melting the nickel plate, a part of the flat portion and a part of the flange portion; forming a melt-solidified layer made of melted copper, nickel and iron
Data Source
Figure 1
Figure 2~3
Figure 4~5B
AI summary
A pressure-sensitive device for detecting fluid pressure in which fluid flows in a cap member via a joint is disclosed so as to securely joint the cap member to the joint. A washer-shaped nickel plate is arranged between a flange portion of the copper joint and the stainless-steel cap member, and the outer peripheral edge thereof is laser-welded. The nickel plate, a part of the flange portion and a part of the flat portion are melt and welded. As a result, a melt-solidified layer is formed in all over gap between the flange portion of the joint and the flat portion of the cap member so as to enter deeply from the outer peripheral edge of the flange portion toward the axis L of the joint between the flat portion and the flange portion. Furthermore, the melt-solidified layer is composed on copper, nickel and iron that are melt and solidified.