Iridium Wire Rod Grain Structure for Oxidation Resistance
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Solution Overview
Problem
Conventional iridium wire rods used in high-temperature applications, such as ignition plug electrodes, suffer from inadequate high-temperature durability and oxidation resistance due to preferential degradation at grain boundaries, which is not effectively addressed by composition adjustments alone.
Innovation Solution
A metal wire rod composed of iridium or iridium alloy with a controlled crystal grain structure, where the number of crystal grains per cross-sectional area is limited to 2-20 and Vickers hardness is maintained between 200 Hv and 400 Hv, produced using a micro-pull-down method to minimize residual strain and prevent recrystallization, thereby reducing grain boundary area and enhancing oxidative consumption resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If composition adjustment by alloying is performed to improve high-temperature oxidation resistance, then oxidation resistance is improved, but other properties deteriorate
Solution Approach 1:
The invention changes the material structure parameter (crystal grain size) rather than composition parameters. By controlling the number of crystal grains to 2-20 per 0.25mm² cross-section, the invention achieves improved oxidation resistance without the negative effects of alloying, as the grain boundary area is reduced through structural control rather than compositional modification
2Ease of manufacture
If conventional wire rod processing is used, then manufacturing is simple, but high-temperature durability is insufficient due to preferential degradation at grain boundaries
Solution Approach 1:
The invention applies local quality control by creating a specific crystal grain structure with 2-20 grains per 0.25mm² cross-section. This localized structural control reduces grain boundary area at critical locations, thereby improving high-temperature durability while maintaining manufacturing feasibility through controlled processing conditions
3Reliability
If crystal orientation control is performed to reduce grain boundary degradation, then oxidation resistance is improved, but the material structure changes at high temperature exceeding recrystallization temperature
Solution Approach 1:
The invention applies preliminary action by establishing a specific crystal grain structure (2-20 grains per 0.25mm²) before the wire rod is exposed to high-temperature service. This pre-established structure with minimized grain boundaries provides initial resistance to oxidation and prevents significant structural changes during subsequent high-temperature exposure, as the low grain boundary area reduces sites for degradation and recrystallization
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 resulting wire rod exhibits improved high-temperature oxidative consumption resistance and mechanical properties, with minimal structural change and hardness variation when exposed to temperatures exceeding recrystallization temperatures, leading to extended durability and performance.
Implementation Method 1
produced using a micro-pull-down method to minimize residual strain and prevent recrystallization
Implementation Method 2
Iridium is one of precious metals, has a high melting point and good oxidation resistance, and therefore can be used for a long period of time even at a high temperature
Data Source
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AI summary
The present invention provides a metal wire rod composed of iridium or an iridium alloy, wherein the number of crystal grains on any cross-section in a longitudinal direction is 2 to 20 per 0.25 mm2, and the Vickers hardness at any part is 200 Hv or more and less than 400 Hv. The iridium wire rod is a material which is produced by a µ-PD method, and has low residual stress and which has a small change in the number of crystal grains and hardness even when heated to a temperature equal to or higher than a recrystallization temperature (1200°C to 1500°C). The metal wire rod of the present invention is excellent in oxidative consumption resistance under a high-temperature atmosphere, and mechanical properties.