Grade N40, Rated to 180°C (356°F), High Coercivity (UH)
We supply Custom Small Neodymium Cylinders in the specialized N40UH grade.
Standard magnets lose their strength at 80°C.
But the UH (Ultra-High) series comes with heavy rare-earth elements (Dysprosium).
So they can work reliably up to 180°C.
This magnet grade has the N40 energy rating (approx. 40 MGOe) .
It offers an exceptional balance of raw power and thermal stability.
It is the preferred choice for Automotive Sensors, Micro-Motors, and Downhole Instrumentation.
Their space is limited and heat generation is unavoidable.
Why N40UH?
Why choose this specific grade instead of N52 or Standard N35?
1. The “Small Magnet” Physics (Pc Value):
The Science:
Small cylinders (e.g., Diameter 2mm x Length 2mm) have a low “Permeance Coefficient.”
This means they are inherently unstable and fighting their own internal magnetic field.
The Risk:
A small magnet is physically “stressed”.
It demagnetizes much faster than a large block when heated.
A small N52 magnet might fail at just 60°C.
The Solution:
Using N40UH provides the extra “Magnetic Stiffness” (Coercivity) to keep a small magnet stable.
We often recommend UH grade for micro-magnets.
Even if the temperature is only 100°C, just to be safe.
2. The Power Balance:
The Trade-off:
As temperature ratings go up, magnetic strength (Br) typically goes down.
The Sweet Spot:
N40UH is stronger than most high-temp grades (like 35UH).
But tougher than standard grades.
It delivers near-peak power without sacrificing thermal survival.
3. Sensor Linearity:
The Application:
Hall Effect Sensors.
The Benefit:
In precision sensing, you don’t want the magnetic field to drift as the device warms up.
N40UH has a flat, stable temperature curve.
Ensure your sensor readings remain accurate from cold start to full operating temp.
Manufacturing Capabilities
Precision Sizing:
Diameter: Down to 1.0mm.
Length: Custom cut to your exact aspect ratio.
Tolerances: Standard ±0.05mm.
Precision ±0.005mm available for press-fit sensor housings.
Coating for Heat:
Standard:
Nickel (Ni-Cu-Ni) is recommended.
It handles 180°C well.
Avoid:
Do not use standard Epoxy or Plastic coatings.
They are not appropriate for this magnet at the full 180°C limit, as such coatings may melt or degrade.
Ideal Applications
Automotive Sensors: Transmission speed sensors and camshaft position sensors (high heat + vibration).
Micro-Motors: Rotors for surgical tools or dental drills (sterilization heat).
Fiber Optics: Components inside laser housings that generate heat.
Downhole Tools: Electronics shielding in oil/gas exploration.
Ordering Guide: Precision & Grade
To ensure N40UH is the right choice, please specify:
1). Dimensions: Diameter x Length.
2). Max Temp: “Does the application actually hit 180°C?”
– If it goes higher, we must switch to EH or SmCo).
3). Application: “Is this a Sensor or a Holding Force application?”
4). Quantity: N40UH is a specialized material; batch production is most cost-effective.
