釹鐵硼強力磁鐵燒結物理特性NdFeB Sintered Magnet Feature

NdFeB強力磁鐵燒結磁石其專利權，目前已由日本住友金屬公司轉售給日立金屬公司，屬于異方性磁石，所以較粘結品磁力較強，其磁能積由N-35~N-52(一般80℃) (BH)max在53MGOe，但也因高溫退磁特性而產生各種不同耐溫牌號(M100℃、H120℃、SH150℃----等等)

晶界擴散(Grain boundary diffusion，“GBD”) 技術是近幾年發展起來的一種可以有效改善燒結釹鐵硼磁體磁性能的技術手段。通過在磁鋼表面形成一層重稀土膜，經真空熱處理使重稀土沿晶界進入磁體內部，同時重稀土原子取代主相晶粒周圍的Nd 原子形成高矯頑力殼層，這種獨特的顯微結構在極低的剩磁下降值基礎上可大幅提升磁體矯頑力。

Grain boundary diffusion(GBD) technology is a technical means developed in recent years that can effectively improve the magnetic properties of sintered NdFeB magnets.By forming a layer of heavy rare earth film on the surface of the magnet, the heavy rare earth enters the interior of the magnet along the grain boundaries through vacuum heat treatment. At the same time, the heavy rare earth atoms replace the Nd atoms around the main phase grains to form a high coercive force shell. This unique The microstructure greatly increases the magnet's coercive force with extremely low Br loss.

擴散前Before diffusion

擴散後After diffusion

晶界擴散原理示意圖Schematic diagram of grain boundary diffusion principle

與傳統的非擴散磁體NdFeB相比較，晶界擴散工藝的主要優勢體現在：

1. 相同牌號的磁體，採用晶界擴散方式可大幅降低Dy、Tb使用量，成本更低；
2. 採用晶界擴散方式可以製備50EH、52UH等傳統工藝無法企及的高綜合磁性能磁體。

＊由於濃度梯度的存在，擴散深度受限，故規模量產的擴散磁鋼厚度通常會有一定的限制。

Compared with the traditional non-diffusion magnet NdFeB, the main advantages of the grain boundary diffusion process are reflected in:

1. For magnets of the same brand, the use of grain boundary diffusion can greatly reduce the usage of Dy and Tb, and the cost is lower;
2. The grain boundary diffusion method can be used to prepare magnets with high comprehensive magnetic properties such as 50EH and 52UH that are beyond the reach of traditional processes.

＊Due to the existence of concentration gradient, the diffusion depth is limited, so the thickness of diffusion magnet steel for large-scale mass production usually has certain limitations.