Guide Wire Solid-State Welding for Dissimilar Metal Joints
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Solution Overview
Problem
Existing guide wires face a challenge in balancing column strength and flexibility, as improvements in one characteristic often compromise the other, leading to unsatisfactory performance in navigating body lumens without damaging them.
Innovation Solution
A method of joining dissimilar metallic materials like nitinol and stainless steel using electrical current for solid-state welding, followed by a follow-up force to create a weld nugget with increased cross-sectional area and reduced heat-affected zone, enhancing strength and kink resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If guide wire stiffness is increased to improve column strength, then the guide wire can support balloon catheters better, but the guide wire becomes less flexible and may damage body lumens
Solution Approach 1:
The guide wire is divided into multiple segments with different material compositions and mechanical properties. The proximal portion uses stiffer materials for column strength, while the distal portion uses more flexible materials for navigation, resolving the contradiction between supporting catheters and navigating lumens without damage
Solution Approach 2:
Different portions of the guide wire are assigned different material properties - the proximal portion has higher stiffness for structural support, while the distal portion has lower stiffness for flexibility and safety in body lumens, allowing each region to optimize its function locally
2Manufacturing precision
If electrical current is applied for solid state welding of dissimilar metals, then the materials are heated for deformation without melting, but rebounding effects occur during welding
Solution Approach 1:
A follow-up force is applied before the welding process completes to pre-compress the dissimilar metal portions. This preliminary action counteracts the rebounding effects that occur during welding, ensuring consistent weld joint quality and reliability without melting the materials
Solution Approach 2:
The follow-up force applied during welding acts as a preliminary counter-action to the rebounding forces that will occur. By applying this opposing force in advance, the welding process achieves consistent results despite the inherent rebounding effects of dissimilar metal deformation
3Manufacturing precision
If follow-up force is applied during solid state welding, then weld nugget cross-sectional area increases and heat-affected zone reduces, but additional force control complexity is introduced
Solution Approach 1:
The follow-up force application is merged with the existing welding process rather than being a separate operation. The same electrical current delivery system that provides welding heat also delivers the follow-up force, simplifying the overall system while achieving improved weld nugget geometry and reduced heat-affected zone
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 allows for the direct joining of dissimilar metals with consistent strength characteristics, reducing variability and improving kink resistance, while avoiding the risks of melting and metallurgical incompatibilities, thus producing guide wires suitable for medical applications.
Implementation Method 1
the applied electrical (e.g., DC, AC, or both) current serves to heat the portions of the members to be joined so that they undergo solid state deformation, such that the materials are not melted, but deform and form a weld joint while in a solid state
Implementation Method 2
a first force is applied while delivering electrical (e.g., DC, AC, or both) current through the separate members so as to weld the separate portions to one another
Data Source
AI summary
The present disclosure is directed to a multi-segment device, such as an intravascular guide wire. The multi-segment device includes an elongate first portion comprising a first metallic material, an elongate second portion comprising a different metallic material, the first and second elongate portions being directly joined together end to end by a solid-state weld, and a heat affected zone surrounding an interface of the weld where the first and second portions are joined together, wherein the heat affected zone has an average thickness of less than about 0.20 mm.