Textured-Powder Bi-2212/Ag Wire Drawing With Lower Silver Content
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Solution Overview
Problem
The conventional oxide-powder-in-tube (OPIT) method for fabricating Bi-2212/Ag wire results in high costs due to excessive silver content and differing drawing properties of Bi-2212 cores and silver matrix, leading to sub-element breaks and sausaging during wire drawing.
Innovation Solution
A novel method involving the assembly of compressed textured-powder bars in a silver alloy matrix with a local area ratio of approximately 1:1, allowing for uniform drawing and reduced silver content, along with a cable-in-conduit configuration for high-temperature heat treatment, to enhance superconducting performance and reduce costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the oxide-powder-in-tube (OPIT) method is used to fabricate Bi-2212/Ag wire, then the wire can be produced with multi-sub-element structure, but the silver content becomes excessive and cost becomes high
Solution Approach 1:
The patent changes the local area ratio (LAR) parameter from the conventional 4:1 Ag:Bi-2212 ratio to a new ratio of approximately 1:1, dramatically reducing the silver content while maintaining wire integrity through optimized drawing processes
Solution Approach 2:
The patent uses composite materials by combining Bi-2212 powder with a silver alloy matrix containing specific additions (such as 0.5-2.0 wt% Pb, 0.1-0.5 wt% In, or 0.1-0.5 wt% Ga) to achieve both structural integrity and reduced silver content
2Manufacturing precision
If the conventional OPIT method is used with high silver content, then the silver matrix can control the area-reducing draw, but the drawing properties of Bi-2212 cores and silver matrix differ significantly causing sub-element breaks and sausaging
Solution Approach 1:
The patent optimizes multiple parameters including LAR (local area ratio) to ~1:1, drawing reduction per pass (5-15%), and number of drawing passes (10-20 passes) to achieve uniform deformation and prevent breaks
Solution Approach 2:
The patent employs a silver alloy matrix with specific compositional additions (Pb, In, Ga) that modify the matrix properties to better match the drawing behavior of Bi-2212 cores, reducing differential deformation
3Manufacturing precision
If the LAR is limited to 4:1 Ag:Bi-2212 to sustain registration control, then the silver matrix can control the area-reducing draw, but the overall wire cost becomes problematically high
Solution Approach 1:
The patent fundamentally changes the LAR parameter from 4:1 to approximately 1:1, enabling cost reduction while implementing a multi-pass drawing process with 5-15% reduction per pass to maintain registration control
Solution Approach 2:
The patent performs preliminary texturing of the Bi-2212 powder before assembly into the silver alloy matrix, creating a pre-aligned structure that maintains registration control during subsequent drawing with reduced silver content
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 enhances the superconducting performance of the wire while significantly reducing the silver content and overall cost, achieving uniform properties and robust winding formation with improved stress management and heat treatment capabilities.
Implementation Method 1
the drawing properties of the Bi-2212 cores and the silver matrix are significantly different... the assembly is drawn, re-stacked and re-drawn to form a multi-sub-element composite wire
Implementation Method 2
A novel method is described to assemble a multi-sub-element billet containing an array of compressed textured-powder bars (TP bars) of Bi-2212 in a silver alloy matrix
Data Source
AI summary
A composite billet includes an array of textured-powder bars in a geometry that is compatible with assembly and drawing of a billet with LAR˜1:1. A method is presented of compressing the bars suitable for the billet geometry in an inert gas environment. Methods of drawing of the billet control the deformation of the composite billet during area-reducing draw to fine wire so that the shape and registration of the constituent bars is preserved. Lastly a method is disclosed to fabricate a cable-in-conduit conductor containing the textured-powder Bi-2212/Ag wires that enables robust forming of windings and also provides in-cable containment of a buffer gas flow under high pressure during the high-temperature heat treatment of the winding that is required to produce optimum superconducting performance in the winding.