Raw material composition and efficacy of sintered neodymium iron boron

We all know that the main raw materials for sintered neodymium iron boron permanent magnets are neodymium, iron, and boron. However, in addition, many other elements are added to the raw materials, which play different roles in the magnets. Manufacturers often design product formulas based on user needs, and the raw material formulas can be said to be confidential information of various manufacturers.

The dozens of elements of sintered neodymium, iron, and boron are like the various seasonings we need to add to make a delicious dish. It is precisely because of the scientific and regular combination of these elements with different intrinsic characteristics and functions that we have achieved various grades and properties of neodymium, iron, and boron. Understanding the significance of each element is of great significance for us to better understand the performance and manufacturing costs of different brands. Let's briefly introduce the value of these elements.

For better understanding, we can divide the constituent elements of neodymium iron boron into three categories: 

One is the main elements RE (Ce, Gd, Nd, Dy, etc.), Fe, B, which are mainly responsible for forming RE2Fe14B main phase grains.

The second is small elements such as Al, Co, Ga, Zr, etc., mainly responsible for optimizing the coating of grain boundaries relative to the main phase grains.

Third, impurity elements, such as carbon and oxygen, are inevitably introduced into raw materials and production.

The schematic diagram of the types of neodymium iron boron elements is shown in the following figure.

Usually, in the production process, in order to achieve better performance effects with different formulations, we also need to conduct certain inspections and treatments on the raw materials before use to meet some basic requirements. Some common requirements for elements are shown in the table below.

The above are typical reference values for commonly used raw materials. In actual production processes, raw material manufacturers often have certain deviations due to the use of different process routes. For example, the ratio of the two in PrNd may change from 20:80 to 25:75, GdFe may be less than 75%, and the B content in different batches of BFe may fluctuate significantly. This requires us to combine the actual content of each batch of quality inspection documents in the use process for matching.

Each element contained in neodymium iron boron magnets has its own unique characteristics, such as:

The introduction of La and Ce elements will reduce the remanence Br and Coercivity Hcj of the magnet, but its price is very cheap, which can reduce the cost;

The REFeB composed of pure Nd elements replacing PrNd has very high saturation magnetization, which can be used to prepare ultra-high remanent magnets;

The introduction of Tb element can significantly increase the Hcj of magnets, but its cost is extremely expensive;

The price of Gd element is relatively cheap, and the REFeB formed by it has the highest Curie temperature, which can prepare high-temperature resistant magnets, but it will significantly reduce Br.

To understand how to combine and manufacture magnets with the lowest cost to meet the required grade performance requirements, we need to understand the characteristics of each element in neodymium iron boron. The specific element characteristics are shown in the table below.

The material cost of over 80% -90% is mainly composed of the remarks "high and low", where the "-" part indicates that the addition amount is very small or the price is cheap, which has little impact on the overall cost. The addition of La and Ce is mainly aimed at reducing costs. In recent years, with the continuous progress of technology, Ce magnets have been applied in more and more higher grades. 

By deeply understanding the characteristics of the above elements and understanding the impact of various elements on sintering process, sintering density, aging process, and product performance, we can guide us in producing neodymium iron boron products with high cost-effectiveness.