How to accurately select NdFeB magnet grades based on application requirements?
1. Clarify your working environment temperature
This is the top priority for selection because high temperature is the main cause of demagnetization of neodymium-iron-boron magnets.
Normal temperature environment (≤80℃): Such as speaker horns, magnetic clasps, toys, stationery, etc.
Recommended grades: N series (such as N35, N42, N52) can meet the requirements. In these applications, magnets usually do not experience excessively high temperatures.
Medium to high temperature environment (80℃ - 150℃): Such as automotive micro-motors, energy-saving elevator traction machines, variable-frequency household appliances (air-conditioning compressors), etc.
Recommended grades: At least the H series should be selected, and a more reliable option is the SH series. For example, the internal operating temperature of variable-frequency air-conditioning compressors is relatively high, so SH or higher-grade magnets are usually used.
High temperature environment (≥150℃): Such as automotive drive motors, high-speed spindles, aerospace fields.
Recommended grades: UH, EH or even AH series must be used. For example, due to the high internal temperature of drive motors in new energy vehicles, neodymium-iron-boron of EH and above grades are generally adopted.
2. Determine your requirements for magnetic strength
On the premise of meeting the temperature requirements, then consider the magnetic strength.
Pursuing extreme magnetic force with limited space: Such as consumer electronic products (magnetic wireless charging, headphone magnets), high-performance micro-motors.
Recommended grades: Choose grades with large numbers, such as N50, N52, etc.
Moderate magnetic force requirements, considering cost: Such as household refrigerator magnets, some door stoppers, advertising magnetic stickers, etc.
Recommended grades: Choose cost-effective grades such as N35 and N38. Blindly pursuing high grades will only increase unnecessary budgets.
3. Consider other harsh environmental factors
Humid, salt spray environments: Such as underwater equipment, outdoor applications.
Key measures: Surface treatment is crucial. Coatings must be selected, such as common nickel plating (bright appearance), epoxy resin (no heavy metal risk), etc., to prevent oxidation and corrosion of the magnet.
Strong vibration or impact environments: Such as power tools, automotive vibration components.
Precautions: Neodymium-iron-boron material is hard and brittle, and is easily damaged by strong collisions. In structural design, direct impact on the magnet should be avoided, and attention should be paid to the installation method.
4. Pay attention to the process impact of size and shape
High precision requirements: If your equipment has extremely high requirements for magnet size accuracy (such as sensors and encoders in the automation field), you need to pay attention to the product's dimensional tolerance information. Usually, processing methods such as wire cutting and slicing can ensure higher precision.
Common Selection Misunderstandings
Misunderstanding 1: "N52 is the best in any case": Although N52 has strong magnetic force, if used in an environment exceeding 80℃, its demagnetization risk is much higher than that of N35H. The most suitable one is the best.
Misunderstanding 2: "The thicker the magnet, the linear growth of magnetic force": Magnetic force increases non-linearly with the increase of thickness. When the thickness increases from 2mm to 3mm, the magnetic force increases significantly (about 30%); but when it increases from 3mm to 5mm, the increase range will be smaller (about 15%), and there is a marginal effect.
Misunderstanding 3: "Only look at the grade, not the coating": Even if the grade is selected correctly, if uncoated magnets are used in a humid environment, they will soon corrode and pulverize, leading to failure of the entire product.