Nb3Sn-NbTi Superconducting Joint Structure Without Pb or Cd Solder
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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 there is a lack of effective methods for joining these wires without compromising their superconducting properties.
Innovation Solution
A superconducting joint structure using Nb alloy strips with added elements like Hf, Ta, Zr, or W to increase recovery and recrystallization temperatures, allowing jointing with Nb3Sn and NbTi wires through a Nb3Sn layer and mechanical contact, without using hazardous substances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low-melting-point superconducting solder (Pb-Bi, Wood's metal, Pb-In, Sn-In) is used to joint Nb3Sn and NbTi wires, then superconducting joint can be achieved without mechanical deformation, but environmentally hazardous substances (Pb and Cd) are used
Solution Approach 1:
The invention changes the material composition parameters by adding specific elements (Hf, Ta, Zr, or W) to the Nb alloy to increase its recovery and recrystallization temperatures. This parameter modification enables the Nb alloy to maintain structural integrity during high-temperature processing while forming a Nb3Sn layer for superconducting joint, eliminating the need for hazardous Pb-Bi solder.
Solution Approach 2:
The invention creates a composite structure where an Nb alloy (enhanced with Hf/Ta/Zr/W) forms a joint strip that combines mechanical strength with superconducting properties. The Nb3Sn layer formed on the Nb alloy surface creates a composite material system that provides both structural support and superconducting functionality, replacing the need for separate solder materials.
2Ease of manufacture
If mechanical pressure welding is used to joint NbTi wires, then superconducting joint can be achieved, but Nb3Sn wires cannot be jointed by mechanical method due to brittleness
Solution Approach 1:
The invention creates a universal joint strip made of Nb alloy that can joint both NbTi and Nb3Sn superconducting wires through the same diffusion bonding process. The Nb3Sn layer formed on the Nb alloy surface enables compatibility with Nb3Sn wires, while the Nb alloy itself can mechanically and superconductively joint with NbTi wires, providing multi-material adaptability.
Solution Approach 2:
The Nb alloy joint strip acts as an intermediary material between NbTi and Nb3Sn wires. The Nb3Sn layer formed on the Nb alloy surface serves as a transition interface that enables superconducting joint with Nb3Sn wires, while the Nb alloy base material provides the mechanical strength and superconducting properties needed for jointing NbTi wires.
3Reliability
If annealing treatment is performed at high temperature to form Nb3Sn layer, then superconducting joint is achieved, but recovery and recrystallization of Nb occurs at lower temperatures causing property degradation
Solution Approach 1:
The invention modifies the microstructural parameters of Nb by adding alloying elements (Hf, Ta, Zr, or W) that increase the recovery and recrystallization temperatures. This parameter change delays microstructural degradation during high-temperature annealing, allowing the Nb alloy to maintain its mechanical properties while forming the Nb3Sn superconducting layer.
Solution Approach 2:
The invention converts the potential harm of high-temperature annealing (which would normally cause Nb recovery and recrystallization) into a benefit by using the heat treatment to form the desired Nb3Sn superconducting layer on the Nb alloy surface. The alloying elements enable the Nb to withstand this thermal processing without microstructural degradation.
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 structure maintains high superconducting properties and avoids the use of environmentally harmful materials, enabling reliable connections suitable for nuclear magnetic resonance apparatuses.
Implementation Method 1
a joint strip having one or more of Nb alloy strips to which an element M is added (wherein the element M is an element that increases a recovery temperature and a recrystallization temperature of Nb)
Implementation Method 2
one end of the joint strip is jointed with the Nb3Sn superconducting wire by contact with each of the one or more of Nb alloy strips and each of the one or more of Nb3Sn superconducting cores through a Nb3Sn superconducting layer
Data Source
AI summary
A superconducting connection structure 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.