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Production process flow


Ingredient Mixing

Also known as composition design, the ingredient mixing process is crucial in the production of sintered neodymium iron boron (NdFeB) magnets. It directly impacts the quality and magnetic performance indicators required by customers. This is because many intrinsic magnetic properties of the material, such as magnetic polarization strength and Curie temperature, are determined by the material's composition. The fundamental principle of composition design is to ensure sufficiently high intrinsic performance while also considering material costs.


Melting Process

Melting is the first step in the production process of sintered neodymium iron boron (NdFeB) magnets. In this process, the melting furnace produces alloy ingots. The furnace temperature needs to reach around 1300 degrees Celsius, and the process takes about four hours to complete. Through this process, the raw materials are subjected to high-temperature melting and subsequent cooling to form alloy ingots, which are then processed further in the subsequent steps of the production process.


Hydrogen Embrittlement

In the initial crushing process, hydrogen embrittlement treatment is used to crush the raw alloy material into sizes below several hundred micrometers (μm).


Air Jet Milling

The purpose of milling is to break down large alloy ingots into powdered form of a specific size. The latest milling process involves turning neodymium iron boron alloy strip (SC strip) into powder using a combination of hydrogen crushing and air jet milling. To obtain well-oriented magnets, it's important that the powder particles are small (around 3-4μm) with a narrow size distribution. Additionally, the powder particles should be spherical or nearly spherical in shape.



After loading the crushed magnetic powder into molds, an external magnetic field is applied for orientation, and then the oriented powder is compacted. Currently, there are three commonly used compaction methods: tape casting, cold isostatic pressing, and rubber mold isostatic pressing. Among these methods, rubber mold isostatic pressing can achieve a higher energy product under the same neodymium content.


Sintering into Blank Materials

The relative density of the compacted neodymium iron boron powder is relatively high, and the contact between particles is mechanical in nature, resulting in low bonding strength. To further increase density, improve inter-particle contact properties, enhance strength, and achieve microstructural characteristics that contribute to high permanent magnetic performance, the green compacts are heated to a temperature below the melting point of the basic powder phase. This heat treatment process, known as sintering, involves holding the green compacts at that temperature for a certain duration.



The actual applications of sintered neodymium iron boron (NdFeB) magnets come in various shapes such as disks, cylinders, rings, blocks, tiles, sectors, and various irregular shapes. Due to the diverse shapes and sizes of permanent magnetic components, except for large-sized regular magnets, it's often challenging to achieve one-step molding. In the powder metallurgy process, larger blanks are produced initially, which are then subjected to sintering and annealing treatments. Afterward, these blanks undergo machining processes (including cutting, drilling, etc.) and grinding to manufacture magnetic materials that match the desired shapes and sizes according to customer requirements.


Boundary Diffusion

In the context of crystal boundary diffusion, alloy powders are coated onto surfaces perpendicular to the magnetization direction of the rare-earth permanent magnetic material's body. The crystal boundary diffusion material alloy powder constitutes 3-5% of the blank's mass. Crystal boundary diffusion is carried out using a vapor deposition diffusion process. This technique reduces the usage of heavy rare-earth elements, effectively conserving these resources and lowering the production cost of magnets. It simultaneously enhances intrinsic coercivity while minimizing residual induction reduction. This method enables the production of extremely high-performance magnet grades like 54UH and 50EH.


Surface Treatment

For neodymium iron boron (NdFeB) magnets, there are three commonly used electroplating methods:
1. Zinc Plating: Applying a zinc coating to the surface.
2. Nickel-Copper-Nickel Plating: Coating the surface with layers of nickel, copper, and nickel.
3. Nickel-Copper-Chemical Nickel Plating: Coating the surface with layers of nickel, copper, and chemical nickel.
Additional plating options include gold plating, silver plating, tin plating, black nickel plating, and epoxy coating.
These surface treatments serve various purposes, such as enhancing corrosion resistance, improving appearance, providing a protective layer, and tailoring the magnet's properties to specific requirements.



Neodymium iron boron (NdFeB) magnets are not inherently magnetic during the production process. They lack the properties of mutual attraction and repulsion like magnets. Only after undergoing a magnetization process do, they acquire magnetic properties.
There are two common methods used to magnetize NdFeB magnets, both of which are widely used in the market:
1. Direct Current (DC) Magnetization: Applying a direct current to magnetize the material.
2. Pulse Current Magnetization: Applying pulsed currents to magnetize the material.
These methods induce the necessary magnetic field within the magnets, allowing them to acquire their desired magnetic characteristics.