Reed Switch Wire Rod Alloy for High Curie Temperature and Low Resistance
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Solution Overview
Problem
Reed switches face challenges with materials having high Curie temperatures and low resistance, while also requiring excellent glass sealing properties to prevent cracking and maintain hermeticity, especially when used for large currents.
Innovation Solution
An iron-group alloy with a specific composition, primarily composed of Co and containing Fe and Ni within certain ranges, is used to achieve a high Curie temperature, low resistance, and excellent glass sealing properties, ensuring a matching thermal expansion coefficient with the glass tube to prevent cracking and maintain hermetic sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the wire diameter is reduced to 1 mm or less for miniaturization, then the size is reduced, but the mechanical strength and durability may deteriorate
Solution Approach 1:
The patent creates a composite material system by combining Co-Fe-Ni alloy with specific glass tube materials, where the alloy composition is designed to have thermal expansion coefficient compatibility with the glass (ratio ≥ 90%). This composite approach ensures that the metal wire and glass tube expand and contract together during temperature changes, preventing bonding failure and cracking while maintaining the high Curie temperature and low resistance characteristics
Solution Approach 2:
The patent applies preliminary action by performing cold working (5-30%) and specific heat treatment before final wire drawing to refine the grain structure and eliminate defects early in the manufacturing process. This preliminary structural optimization ensures that even at 1 mm diameter or less, the wire maintains sufficient mechanical strength and fatigue resistance for reliable operation
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 alloy provides a reed switch with a high Curie temperature, low resistance, and excellent workability, allowing for reliable operation over long periods, even with large currents, and contributes to the miniaturization of reed switches due to its small wire diameter.
Implementation Method 1
a ratio of a thermal expansion coefficient of a glass tube comprised by the reed switch to a thermal expansion coefficient of the wire for the reed switch being 90% or more
Implementation Method 2
the wire having a Curie temperature of 900°C or higher
Data Source
Figure 1~2
AI summary
There is provided a wire for a reed switch used for a material of a reed piece comprised by a reed switch, the wire being composed of an iron-group alloy containing Fe and 0 mass % or more and less than 10 mass % of Ni, with a total content of the Fe and the Ni satisfying 10 mass % or more and less than 20 mass %, with a balance of Co and an impurity, the iron-group alloy having a cubic crystal structure, the wire having a Curie temperature of 900°C or higher, the wire having a specific resistance of 15 µΩ • cm or less at normal temperature, a ratio of a thermal expansion coefficient of a glass tube comprised by the reed switch to a thermal expansion coefficient of the wire for the reed switch being 90% or more, the wire having a diameter of 1 mm or less.