DailyMag Sintered Magnet
Sintered magnets are manufactured using the process called powder metallurgy. Through “liquid phase sintering,” a proper composition is ground into a fine powder, compressed, and heated to achieve densification. As a result, they are called sintered magnets. This process is used to create ferrite, neodymium-iron-boron (neo), and samarium cobalt (SmCo) magnets.
DailyMag is a leading sintered magnet manufacturer since 2005. We supply high-quality sintered magnets across the world at reasonable prices. Our sintered magnets come in a variety of shapes, sizes, coatings, and materials such as SmCo, NdFeB, ferrite, etc.
For more information about our sintered magnets, contact us today!
The black epoxy sintered NdFeB magnets have a black epoxy coating for enhanced corrosion protection. They have a strong attraction force.
Sintered ring magnets can be made from a variety of materials such as neo, SmCo, ferrite, etc. They can be used for DC/AC servo motors.
The rectangular bar sintered neodymium magnets are commonly used for magnetic sensors, motors, wind turbines, printers, and many more.
Block sintered NdFeB magnets can be used for hard disk drives, DC motors, MRI equipment, sensors, and other delicate and highly sensitive applications.
The sintered block hard ferrite magnets have higher resistance to oxidation and demagnetization compared to non-rare earth permanent magnets.
N52 sintered disc NdFeB magnets have a lower temperature coefficient than ceramic magnets and higher unit magnetic properties than other magnets.
Processing of Sintered Magnet
Sintered magnets are produced using the powder metallurgical process. The process works by pulverizing the magnet alloy finely. After that, the easy magnetization axis will be oriented in the magnetic field. Then, the material will be pressed and sintered.
In comparison to bond magnets that are manufactured by mixing in plastic, sintered magnets have superior heat resistance and high magnetic characteristics because there are no plastic and other non-magnetic section.
Sintered Hard Ferrite Magnets
Sintered hard ferrite magnets are manufactured from strontium carbonate or barium carbonate and iron oxide. Individual raw materials will be combined, ground, and calcined or pre-sintered in accordance with a recipe. Using various intermediary phases, a hexagonal ferrite phase such as SrFe12O19 or BaFe12O19 is produced. The previously sintered granulate is ground even more before being sintered or pressed in a magnetic field, either dry or wet, or even without a magnetic field (isotropic). Hard ferrites have brittleness, hardness, and other proper mechanical properties since they are ceramic materials.
Sintered Magnet Machining
Sintered magnets may undergo some machining processes such as:
- Wire cutting
- Grinding them parallel and smooth
- ID or OD grinding
- Slicing them into smaller parts
- Other machining processes
All of our machining processes are done carefully in order to minimize cracking and chipping.
Coating Options
Sintered magnets are always coated to add protection and enhance their resistance to corrosion and chemicals. Their protective coatings include:
- Epoxy or dry-sprayed epoxy
- Gold
- Nickel–Copper-Nickel
- Nickel or electrolytic nickel
- Zinc
- Parylene
- Conversion coatings such as zinc, iron or chromates and manganese phosphates
Sintered Magnet Properties
Magnetic Performance
| Magnet | Br (T) |
Hci (kA/m) |
BHmax (kJ/m3) |
TC | |
| (°C) | (°F) | ||||
| Sintered Nd2Fe14B | 1.0–1.4 | 750–2000 | 200–440 | 310–400 | 590–752 |
| Sintered SmCo5 | 0.8–1.1 | 600–2000 | 120–200 | 720 | 1328 |
| Sintered Sm(Co, Fe, Cu, Zr) | 0.9–1.15 | 450–1300 | 150–240 | 800 | 1472 |
| Sintered Alnico | 0.6–1.4 | 275 | 10–88 | 700–860 | 1292–1580 |
| Sintered Sr-ferrite | 0.2–0.78 | 100–300 | 10–40 | 450 | 842 |
Mechanical and Physical Properties of Sintered NdFeB and SmCo Magnets
| Property | SmCo | NdFeB |
| Coercivity (MA/m) | 0.493–2.79 | 0.875–2.79 |
| Remanence (T) | 0.8–1.16 | 1–1.5 |
| Recoil permeability | 1.05–1.1 | 1.05 |
| Temperature coefficient of coercivity (%/K) | −(0.30–0.15) | −(0.65–0.40) |
| Temperature coefficient of remanence (%/K) | −(0.05–0.03) | −(0.12–0.09) |
| Curie temperature (°C) | 700–850 | 310–370 |
| Thermal expansion coefficient, perpendicular to magnetization (1/K) | (10–13)×10⁻⁶ | (1–3)×10⁻⁶ |
| Thermal expansion coefficient, parallel to magnetization (1/K) | (5–9)×10⁻⁶ | (3–4)×10⁻⁶ |
| Density (g/cm³) | 8.2–8.5 | 7.3–7.7 |
| Flexural strength (N/mm2) | 150–180 | 200–400 |
| Tensile strength (N/mm2) | 35–40 | 35–40 |
| Compressive strength (N/mm2) | 800–1000 | 1000–1100 |
| Electrical resistivity (Ω·cm) | (50–90)×10⁻⁶ | (110–170)×10⁻⁶ |
| Vickers hardness (HV) | 400–650 | 500–650 |
Sintered NdFeB or neodymium-iron-boron magnets are one of the most powerful magnets. Other grades of sintered NdFeB magnets have up to 240°C of maximum operating temperature. They are commonly used for high-performance motors, magnetic separation, sensors, MRI, brushless DC motors, voice coil motors in hard disk drives, Hi-Fi systems, auto motors, and other magnetic tools.
The NdFeB magnets have features such as:
- Excellent resistance to demagnetization
- Possibility of more coils
- Highest magnet strength available
- Less waste – especially with complex geometries
- Good at withstanding low temperatures down to – 100°C
- Good at withstanding temperatures up to 240°C
Manufacturing Processes
In this process, high-purity rare earth oxides will be refined and separated from rare earth ore.
To create the desired composition of sintered magnets, additives like iron, rare earth metals, cobalt, and other materials are measured.
After that, the materials are melted in the vacuum induction furnace. And in the induction furnace, the materials are heated to a high frequency and will be melted.
After going through different processing stages, the ingots are grounded or pulverized into particles that measure several microns in size.
And to avoid oxidation, the tiny particles will be protected by argon and nitrogen.
After pulverization, the magnetic particles will be placed in jig and a magnetic field is applied while pressing the magnets into shape. This procedure results in magnetic anisotropy. There are 2 different pressing techniques:
- perpendicular pressing – pressing magnets in a perpendicular magnetic field
- parallel pressing – pressing magnets in a parallel magnetic field
The perpendicular press technique is used to produce a higher-performance magnet. And the parallel press method must be used to produce ring magnets.
Sintering furnaces are used to apply heat treatment to pressed ingots. The ingots’ true density is 100% after sintering. Before sintering, the ingots have roughly 50% of true density.
The sintering process causes the ingots’ measurements to decrease by roughly 70% to 80%. Their volume will also decrease by roughly 50%.
After the sintering and aging operations are finished, the essential magnetic characteristics are established. The most important measurements, such as coercivity, maximum energy product, and remnant flux density will be recorded.
And only the magnets that have passed the inspection are then taken to the subsequent processes such as assembly and machining processes.
High-temperature sintering can improve the magnetic performance of sintered magnets due to the:
- Increase in sintered density
- Greater sinter neck formation
- Better alloy homogenization
- Grain growth of the material
- Reduction of oxides
Sintered soft magnets can be used for:
- Stators and DC rotors
- Solenoids
- Rotors for brushless DC motors
Sintered NdFeB magnets have a (BH) or max that can reach over 50M. On the other hand, bonded NdFeB magnets are usually below 10M.
