Nb3Sn-NbTi Superconducting Joint Using an Nb Alloy Interlayer
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Solution Overview
Problem
Conventional superconducting joint techniques for Nb3Sn and NbTi wires use environmentally hazardous substances like Pb and Cd, and existing methods do not provide a viable solution for a superconducting joint between these materials.
Innovation Solution
A superconducting joint structural body using Nb alloy strips with added elements such as Hf, Ta, Zr, or W to increase recovery and recrystallization temperatures, allowing for a diffusion joint between Nb3Sn and NbTi wires without hazardous substances, using a method involving crimping and annealing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional low-melting-point superconducting solders (Pb-Bi, Wood's metal) are used for jointing Nb3Sn and NbTi wires, then superconducting joint can be achieved, but environmentally hazardous substances are introduced
Solution Approach 1:
The patent introduces an Nb alloy strip as an intermediary material between Nb3Sn and NbTi wires. This strip contains Nb cores that form Nb3Sn layers through diffusion, creating a transition zone that enables superconducting joint without using hazardous solders. The Nb alloy strip mediates the connection between the two different superconducting materials while maintaining superconducting properties.
Solution Approach 2:
The patent replaces the mechanical soldering process with a diffusion-based joining method. Instead of using low-melting-point solders that require melting and solidification, the invention uses thermal diffusion to form Nb3Sn layers on the Nb alloy strip surfaces, creating a metallurgical bond that maintains superconducting properties without mechanical deformation or hazardous substances.
2Ease of manufacture
If mechanical pressure welding is used for NbTi wires, then superconducting joint can be achieved with simplicity, but it cannot be applied to Nb3Sn wires due to their brittleness
Solution Approach 1:
The patent creates a universal joining method that works for both Nb3Sn and NbTi wires through the Nb alloy strip intermediary. The diffusion-based process accommodates the different mechanical properties of brittle Nb3Sn and ductile NbTi, providing a single methodology that can join either material type without requiring material-specific process adjustments.
Solution Approach 2:
The patent changes the joining mechanism from mechanical pressure welding to thermal diffusion bonding. This parameter change in the joining process allows accommodation of Nb3Sn's brittleness by avoiding mechanical deformation, while still achieving strong superconducting joints. The diffusion process occurs at controlled temperatures that form metallurgical bonds without requiring plastic deformation.
3Reliability
If Nb3Sn wires are jointed through diffusion process requiring high temperature annealing, then superconducting joint can be achieved, but the Nb alloy strip may lose its superconducting properties due to recovery and recrystallization
Solution Approach 1:
The patent performs preliminary alloying by adding elements M (Ta, W, Mo, Re, or their combinations) to the Nb alloy strip before the diffusion process. These alloying elements raise the recovery and recrystallization temperatures of the Nb matrix, preparing it to withstand the high-temperature annealing required for Nb3Sn layer formation without losing its superconducting properties.
Solution Approach 2:
The patent changes the compositional parameters of the Nb alloy strip by incorporating alloying elements M. This compositional modification increases the thermal stability of the Nb matrix, allowing the material to maintain its superconducting properties at the elevated temperatures required for diffusion bonding and Nb3Sn layer formation.
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 joint maintains high superconducting properties without Pb or Cd, enabling a stable connection suitable for nuclear magnetic resonance apparatuses in high magnetic fields.
Implementation Method 1
one end of the joint strip is jointed with the Nb 3 Sn superconducting wire by contact of each of the one or more Nb alloy strips and each of the one or more Nb 3 Sn superconducting cores through a Nb 3 Sn superconducting layer
Implementation Method 2
an element M is added (wherein the element M is an element that increases a recovery temperature and a recrystallization temperature of Nb)
Data Source
Figure 1
Figure 2(A)~2(C)
Figure 3(A)~3(B)
AI summary
The present invention addresses the problem of providing: a superconducting connection structure of an Nb3Sn superconducting wire rod and an NbTi wire rod, the superconducting connection structure comprising no environmental load substances such as Pb and Cd; a method for producing this superconducting connection structure; and a nuclear magnetic resonance apparatus which uses this superconducting connection structure. A superconducting connection structure according to the present invention is provided with: a connection strip that comprises an Nb alloy strip to which an element M is added (wherein the element M is an element which increases the recovery temperature and the recrystallization temperature of Nb); an Nb3Sn superconducting wire rod that comprises an Nb3Sn superconducting core material; and an NbTi wire rod that comprises an NbTi core material. With respect to this superconducting connection structure, one end of the connection strip is connected to the Nb3Sn superconducting wire rod by having the Nb alloy strip and the Nb3Sn superconducting core material in contact with each other by the intermediary of an Nb3Sn superconducting layer; and the other end of the connection strip is connected to the NbTi wire rod by having a newly formed surface of the Nb alloy strip and a newly formed surface of the NbTi core material in contact with each other.