Weighing

Weighing is directly related to the accuracy of magnet composition.

Known Conditions:

1. Magnet composition of sintered Neodymium magnet: eg. Nd₅Dy_0.50Fe_79.97B_6.03 (atomic fraction).
2. Purity of raw material: Nd: 100%, Dy: 100%, Fe: 100%, B content in B-Fe alloy: 20%.
3. Demand: 500kg.

Calculation of Raw Material:

Transform atomic fraction of alloy composition to mass fraction.

1. Relative atomic mass: Nd: 144.24, Fe: 55.847, Dy: 162.50, B: 10.81
2. Calculate the total atomic mass of magnet:

• Nd: 13.5 x 144.24 = 1947.24
• Dy: 0.5 x 162.50 = 81.25
• Fe: 70.97 x 55.847 = 4466.08
• B: 6.03 x 10.81 = 65.18
• Therefore, the total atomic mass is 6559.75.

3. Calculate the mass fraction of each element:

• Mass fraction of Nd = 1947.24/6559.75 x 100% = 29.68%
• Mass fraction of Dy = 81.24/6559.75 x 100% = 1.24%
• Mass fraction of Fe = 4466.08/6559.75 x 100% = 68.08%
• Mass fraction of B = 65.18/6559.75 x 100% = 1.00%

4. Calculate the usage of each material:

• Nd: 29.68% x 500kg = 148.40kg
• Dy: 1.24% x 500kg = 6.20kg
• Fe: 68.08% x 500kg = 340.40kg
• B: 1.00% x 500kg = 5.00kg

Weighing of Each Material

• Mass of Nd: 148.40kg
• Mass of Dy: 6.20kg
• Mass of B-Fe alloy: 5.0/20% = 25kg
• Mass of Fe in B-Fe alloy: 25kg – 5kg = 20kg
• Mass of Fe: 340.40 – 20kg = 320.40kg

Rare earth metal possesses low vapor pressure and active chemical properties, then rare earth metal exists a certain degree of volatilization loss and oxidation loss during melting process, therefore, weighing process of rare earth magnet should consider add additional rare earth metal to ensure accuracy of magnet composition.