At MainRich Magnets, we take pride in producing high-quality sintered neodymium-iron-boron magnets through a meticulous powder metallurgy process involving over a dozen steps from material preparation to final product delivery. Each stage includes rigorous rounds of testing and analysis to ensure high-quality results.
The production process can be divided into two main phases: the front-end production phase, where the magnetic blank is created, and the back-end processing phase, where the blank is machined into the final product. Manufacturers typically either handle both phases or focus solely on the back-end processing.
1. Material Preparation
High-quality raw materials are essential for producing top-notch magnetic materials. At MainRich, we select raw materials based on the required performance standards and national specifications. The raw materials are then cut and surface-treated before smelting.
2. Melting
The first step in producing sintered neodymium-iron-boron permanent magnets is melting the raw materials in a furnace at around 1300 degrees Celsius. This process takes over four hours, resulting in alloy ribbons.
3. Hydrogen Decapsulation and 4 Airflow Milling
Collectively known as powder-making, these processes involve crushing the alloy ribbons into fine magnetic powder. The powder particle size should be small (3-4μm) and spherical or nearly spherical to ensure optimal orientation and magnetic properties.
5. Pressing
The magnetic powder is placed into a mold and oriented using an external magnetic field before being pressed. The orientation process is crucial for producing high-performance magnets. Common methods include die pressing, die pressing with cold isostatic pressing, and rubber mold isostatic pressing, with the latter achieving a higher magnetic energy product.
6. Heat Treatment
The pressed magnet blank undergoes heat treatment to enhance its magnetic properties. This involves sintering at a temperature below the basic phase melting point of the powder, followed by high-temperature quenching and tempering to optimize the microstructure and achieve the best magnetic properties.
7. Machining
Due to the inherent limitations of the magnetic field orientation molding process, sintered magnets require machining to achieve precise shapes and sizes. The hard and brittle nature of the material allows for cutting, drilling, grinding, and rolling. Near-net-shape processing is commonly used in Japanese and Western enterprises to minimize material and labor costs.
8. Grain Boundary Diffusion
To enhance coercivity and temperature stability, rare earth elements like dysprosium and terbium are added to the material. These elements are costly, so grain boundary diffusion technology is used to reduce their addition while maintaining high performance.
9. Surface Treatment
Sintered neodymium-iron-boron magnets are prone to corrosion and oxidation due to their chemically active nature and internal porosity. To prevent performance degradation, strict anti-corrosion treatments such as electroplating, chemical plating, electrophoresis, and phosphating are applied, with electroplating being the most widely used method.
10. Magnetization
Magnetization is essential for imbuing the magnets with their magnetic properties. A magnetizer applies a magnetic field to the magnet, and if the field is not strong enough, the magnet will not reach its required performance levels. Sintered neodymium-iron-boron magnets can be magnetized to present multiple N and S poles as needed.
11. Quality Inspection
Throughout the production process, quality monitoring and inspection are critical to ensure the magnets meet specified standards. At MainRich, we perform rigorous quality checks at various stages to guarantee that our products meet the highest standards. While not every item listed in the quality inspection table needs testing, purchasers can negotiate the necessary inspection items with us according to their specific needs.
| Process Stage | Item | Inspection Attribute | Necessity |
|---|---|---|---|
| 1. Raw Materials | Chemical composition analysis of materials | Quality control | Required |
| 2. Smelting and SC Chips | Original thickness and surface quality of SC chips | Quality control | Required |
| 3. HD + JM Magnetic Powder | Analysis of elements such as oxygen, nitrogen, and carbon | Quality control | Required |
| Particle size distribution of magnetic powder | Quality control | Required | |
| 4. Re-firing Process | Average crystal size | Quality control | Required |
| Orientation of basic structure and grain boundary | Quality control | Phased inspection | |
| Technical parameter measurement | Quality control | Required | |
| Density measurement | Quality control | Required | |
| 5. Final Product Quality Inspection | Adhesion test of coating | Final product inspection | As per agreement |
| Corrosion resistance test of coating | Final product inspection | As per agreement | |
| Appearance quality of coating | Final product inspection | As per agreement | |
| Magnetic properties inspection (including remanence, coercivity, and intrinsic coercivity) | Final product inspection | As per agreement | |
| Dimensional accuracy | Final product inspection | As per agreement | |
| Surface integrity | Final product inspection | As per agreement | |
| Mechanical performance testing | Final product inspection | As per agreement | |
| Magnetic flux comparison (for mass production) | Final product inspection | As per agreement | |
| External visual inspection | Final product inspection | As per agreement | |
| Dimensional and geometric inspection | Final product inspection | As per agreement | |
| Other inspection items as per agreement | Final product inspection | As per agreement |
12. Packaging and Shipping
The final step before the magnets leave the factory is packaging and shipping. MainRich packages the magnets according to purchaser requirements. For strong magnets, land transportation is typically used domestically, while special magnetic shielding packaging is required for air transport when exporting overseas.
By following these detailed steps, MainRich Magnets ensures the production of high-performance sintered neodymium-iron-boron magnets that meet stringent quality and performance requirements. Contact us to know more details!
