Nb3Sn Superconducting Wire Heat Treatment to Prevent Nausite
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Solution Overview
Problem
Existing methods for manufacturing superconductive Nb3Sn-based wires often result in the formation of a nausite phase at low temperatures, leading to reduced grain boundary density and critical current density due to improper heat treatment conditions, which limits their performance in high magnetic fields.
Innovation Solution
A method involving the formation of a titanium and/or tantalum doped multi-filament blank with a diffusion barrier and copper matrix, followed by heat treatment stages at specific temperatures to prevent nausite phase formation, resulting in a microstructure with equiaxial grains and increased grain boundary density, enhancing current carrying capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If heat treatment is carried out at low temperature (400°C) with fast heating speed (150°C/h), then the manufacturing process is faster, but the nausite phase forms and grain boundaries become coarse, reducing critical current density
Solution Approach 1:
The patent applies parameter changes by modifying the heat treatment temperature range to 410-500°C (above the nausite formation threshold of 408°C) and adjusting heating speeds to 100-200°C/h in a controlled manner. This parameter optimization prevents nausite phase formation while maintaining manufacturing efficiency, achieving both high productivity and fine grain boundary density for high critical current density.
2Reliability
If heat treatment temperature is increased above 408°C, then the nausite phase formation is prevented, but the manufacturing complexity and process control difficulty increase
Solution Approach 1:
The patent establishes specific parameter ranges (410-500°C temperature, 100-200°C/h heating speed) that reliably prevent nausite phase formation. By defining these precise parameters, the patent transforms a complex process control problem into a standardized procedure, improving reliability while managing complexity through clear parameter specifications.
Solution Approach 2:
The patent applies preliminary action by pre-defining the optimal heat treatment parameter ranges before actual manufacturing. The temperature range of 410-500°C and heating speeds of 100-200°C/h are predetermined to avoid nausite phase formation, allowing manufacturers to directly implement these parameters without complex real-time adjustments, thus simplifying the process while ensuring high superconducting performance.
3Manufacturing precision
If multiple heat treatment stages are implemented, then the superconductive layer microstructure is improved, but the manufacturing time and energy consumption increase
Solution Approach 1:
The patent merges the functions of multiple heat treatment stages into a single optimized treatment process. By combining bronze matrix formation, tin diffusion, and Nb3Sn layer formation into one continuous heat treatment at 410-500°C, the patent achieves the same microstructure quality as multi-stage processes but with reduced total time and energy consumption, eliminating redundant heating and cooling cycles.
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 method achieves high current carrying capacity in superconductive composite Nb3Sn-based wires for magnetic fields above 12 T by optimizing heat treatment conditions, resulting in improved superconducting properties and increased upper critical field.
Implementation Method 1
at the second stage of heat treatment the tin from the bronze matrix diffuses to niobium filaments, and a superconductive Nb 3 Sn layer is formed
Implementation Method 2
the refractory niobium filaments may be dissolved in a Cu-Sn matrix. The dissolution process represents damage to a crystalline grid of hard metal and transition of its atoms into fluid metal. The motive force behind this process is the difference in the value of thermodynamic potentials of hard metal atoms in the crystalline grid and in fluid metal
Implementation Method 3
At the first stage of diffuse heat treatment, a bronze matrix is formed with high tin content
Data Source
Figure 1
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AI summary
The invention relates to the field of electrical engineering and the creation of long composite wires based on superconducting compounds for use in the manufacture of electrical equipment. Claimed is a method for manufacturing an Nb3Sn-based superconducting wire which includes forming a first titanium- and/or tantalum-doped multi-filament blank by placing a diffusion barrier and a copper matrix in a copper jacket, said copper matrix having a tin-containing rod at its centre and niobium-containing rods arranged therearound, each of which has a copper-containing cladding, deforming said blank until a composite rod of the desired size is formed, cutting same into measured parts, forming a second multi-filament blank from the resulting measured parts by assembling same in a metal jacket, deforming the second multi-filament blank by drawing same to form a wire having a diameter of from 2 to 0.2 mm, and subsequently heat treating said wire in stages, where the second stage of heat treatment is carried out at a temperature of 620-750°C for from 24 to 400 hours, and the first stage of heat treatment is carried out at a temperature of 410-500°C for 5-200 hours.