Stainless Steel Guide Wire Hardness Distribution for Shape Recovery
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Solution Overview
Problem
Existing guide wires lack resilience, which affects their operability and ability to restore shape after bending.
Innovation Solution
A medical wire material made of stainless steel with a specific hardness distribution, where the outer peripheral portion has an average hardness of at least 8.0 GPa measured by Nanoindentation, and a difference in hardness between the entire transverse section and the outer peripheral portion is less than 0.7 GPa, achieved through a combination of straightening by plastic deformation and tension annealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional guide wires are used, then they can perform basic guiding function, but they lack resilience and cannot restore original shape after bending
Solution Approach 1:
The patent applies local quality by creating a hardness gradient within the wire cross-section. The outer peripheral portion (within d/17 from the surface) has higher hardness (≥8.0 GPa) compared to the inner portion, achieving a balance between resilience and flexibility. This localized hardness distribution allows the wire to restore its shape after bending while maintaining operational flexibility.
Solution Approach 2:
The patent changes the physical parameter of hardness distribution within the wire material. By controlling the average hardness of the outer peripheral portion to be ≥8.0 GPa and limiting the hardness difference between outer and inner portions to ≤0.7 GPa, the wire achieves improved resilience while maintaining overall flexibility for vascular navigation.
2Reliability
If wire hardness is increased to improve resilience, then shape restoration capability improves, but the wire becomes too rigid for vascular navigation
Solution Approach 1:
The patent creates different mechanical properties in different regions of the wire cross-section. The outer peripheral portion (depth ≤d/17 from surface) has hardness ≥8.0 GPa for resilience, while the inner portion has lower hardness to provide flexibility. The hardness difference between outer and inner portions is controlled to ≤0.7 GPa, optimizing both resilience and flexibility simultaneously.
Solution Approach 2:
The wire cross-section is effectively segmented into two functional zones: an outer peripheral zone (within d/17 from surface) providing resilience through higher hardness, and an inner zone providing flexibility through lower hardness. This segmentation allows each zone to contribute its optimal property to the overall wire performance.
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 guide wire with enhanced resilience and straightness, improving its ability to maintain shape and operate effectively in complex vascular environments.
Implementation Method 1
when hardness of the transverse section of the wire material is measured by the Nanoindentation method, an average value of hardness of an outer peripheral portion
Implementation Method 2
straightening by plastic deformation
Implementation Method 3
tension annealing
Data Source
Figure 1~2(b)
Figure 3~4(d)
Figure 5~7
AI summary
An object of the disclosure is to provide a medical wire material and a guide wire with excellent resilience. A medical wire material is consisting of stainless steel, in which a shape of a transverse section of the wire material is a circle having a diameter of d mm, and, when hardness of the transverse section of the wire material is measured by the Nanoindentation method, an average value of hardness of an outer peripheral portion constituted of a region surrounded by an outer peripheral edge and a circle having a distance from the outer peripheral edge is d/17 mm is equal to or greater than 8.0 GPa.