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Invar 36, also known as Alloy 36 or UNS K93600, is a nickel-iron alloy famous for its ultra-low thermal expansion. One of the most commonly asked questions about this material is whether it is magnetic. The answer is yes—Invar 36 is magnetic at room temperature. Its magnetic behavior is an important factor in applications that involve electromagnetic interference or require magnetic shielding. In this article, we examine the magnetic characteristics of Invar 36 round bar and how they influence its use in various industries.
Magnetic Properties of Invar 36
Invar 36 is ferromagnetic below its Curie temperature. The material's magnetic behavior is due to its high iron content, combined with a balanced nickel percentage. Here's a breakdown of its key magnetic properties:
| Property | Value |
|---|---|
| Magnetic Behavior | Ferromagnetic (below Curie temperature) |
| Curie Temperature | Approximately 280°C |
| Relative Permeability (μr) | ~ 1,000 - 2,000 |
How Temperature Affects Magnetism
The ferromagnetic nature of Invar 36 is temperature-dependent. Below 280°C, it remains magnetic. Above this Curie temperature, it loses its magnetic properties and becomes paramagnetic. This shift is critical in environments where the alloy is exposed to elevated temperatures.
| Temperature Range | Magnetic Behavior |
|---|---|
| Room Temperature to 280°C | Ferromagnetic |
| Above 280°C | Paramagnetic (non-magnetic) |
Applications Influenced by Magnetism
The magnetic properties of Invar 36 make it suitable for or restrictive in the following applications:
| Industry | Effect of Magnetism | Application |
|---|---|---|
| Electronics | May interfere with sensitive components | Used with shielding |
| Aerospace | Acceptable due to controlled environments | Structural tools and molds |
| Scientific Instruments | Magnetism must be considered | Dimensional standards and holders |
Can the Magnetic Property Be Altered?
The ferromagnetic nature of Invar 36 is inherent due to its composition. However, its magnetic permeability can be influenced slightly through heat treatment and cold working. For applications needing minimal magnetic response, non-magnetic alternatives like Austenitic Stainless Steel or titanium may be preferable.
Related Questions
Is Invar 36 round bar magnetic at room temperature?
Yes, Invar 36 round bar is ferromagnetic at room temperature due to its iron-nickel composition.
At what temperature does Invar 36 lose its magnetic properties?
Invar 36 loses its ferromagnetism at approximately 280°C, which is its Curie temperature.
Can Invar 36 be used in magnetic shielding applications?
Invar 36 is magnetic and not typically used for shielding. For magnetic shielding, materials like mu-metal with higher permeability are more suitable.