ReW Tungsten Wire Microstructure Control for Crack-Free Thinning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in manufacturing rhenium-tungsten (ReW) wires with small diameters is the high likelihood of crack occurrence during the thinning process due to unstable crystal orientations and grain sizes, leading to low yields and increased processing steps.
Innovation Solution
A rhenium-containing tungsten alloy wire with controlled crystalline orientations, where 70% to 90% of the unit area has an orientation difference of 15 degrees or less from the wire drawing direction, and specific grain size distribution, is processed using a method involving EBSD analysis, heat treatments, and wire drawing techniques to achieve stable plastic deformation and reduce crack occurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the wire diameter is reduced to increase pin density, then the number of pins per unit area increases, but crack occurrence during wire drawing increases significantly
Solution Approach 1:
The patent applies preliminary recrystallization heat treatment before the final wire drawing steps to prepare the material structure. By controlling the number of recrystallized grains to 500-800 grains/mm² in advance, the wire is pre-conditioned to resist crack formation during subsequent thinning processes, enabling production of φ0.02mm or smaller diameter wires with high yield.
Solution Approach 2:
The patent changes the microstructural parameters of the ReW wire by controlling grain size and recrystallization degree. Specifically, it adjusts the number of recrystallized grains to 500-800 grains/mm² and controls the area reduction ratio to 90% or less beyond 75%, transforming the material properties to enable successful drawing of ultra-fine wires without cracking.
2Reliability
If strict control of lubricant management and wire drawing conditions is implemented, then wire breakage is suppressed, but processing complexity and time increase
Solution Approach 1:
The patent performs preliminary recrystallization heat treatment to establish an optimal grain structure (500-800 recrystallized grains/mm²) before final drawing. This pre-prepared microstructure inherently resists cracking, reducing the need for extremely strict control of lubricant conditions and drawing parameters during processing.
Solution Approach 2:
The patent replaces reliance on complex mechanical control systems (lubricant management, temperature control, drawing rate control) with a metallurgical solution - controlling the number of recrystallized grains through heat treatment. This substitution simplifies the overall process control by addressing crack prevention at the material structure level rather than through multiple interdependent process parameters.
3Ease of manufacture
If the number of recrystallized grains is increased to improve processability, then wire drawing becomes easier, but crack occurrence increases due to grain boundary accumulation
Solution Approach 1:
The patent optimizes the number of recrystallized grains to a specific range of 500-800 grains/mm², balancing processability and crack resistance. This parameter optimization ensures sufficient grain refinement for easy drawing while preventing excessive grain boundary accumulation that would lead to cracking, achieving both ease of manufacture and high reliability.
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 significantly reduces crack occurrence and improves yield by ensuring uniform crystalline orientations and grain sizes, enhancing the processability and strength of the ReW wire, particularly in the thinning process for probe pins and electrolytic wires.
Implementation Method 1
a final recrystallization treatment is conducted in response to a ratio of reduction of the cross-sectional area (an area reduction ratio) of a molded object with respect to the sintered object reaching a ratio of 90% or less beyond 75%
Implementation Method 2
a sintered object is first subjected to a swaging and drawing (wire drawing) process to form a ReW wire having a diameter of 0.3 to 1.2 mm
Data Source
AI summary
According to one embodiment, a tungsten wire includes a tungsten alloy containing rhenium. According to an EBSD analysis on a unit area, crystalline orientations having an orientation difference of 15 degrees or less from <101>, which is parallel to a wire drawing direction, account for an area ratio of 70% or more and 90% or less to a measurement field on an IPF map. The unit area is a 40 μm×40 μm area located within a range of 100 μm concentrically extending from a central axis in a cross-section along a wire radial direction, which is perpendicular to the wire drawing direction.