NdFeB Magnet Melting Process
Precise Formulation of NdFeB Alloy
The performance of NdFeB alloys is critically dependent on precise chemical composition control. The stoichiometric ratio of the main phase, Nd₂Fe₁₄B, must be strictly maintained—insufficient neodymium (Nd) reduces magnetic properties, while excess Nd promotes the formation of Nd-rich phases, impairing coercivity and thermal stability. Boron (B) deviation can hinder the formation of the main phase, while iron (Fe) content directly influences saturation magnetization. Additives such as dysprosium (Dy) or terbium (Tb) enhance coercivity, cobalt (Co) improves thermal stability, and aluminum (Al) or copper (Cu) optimizes microstructure. To ensure uniformity, raw materials must be weighed with an accuracy of 0.1% or better, often using pre-alloyed or master alloys to minimize segregation.
Vacuum Induction Melting and Rapid Solidification
After precise weighing and formulation, the NdFeB alloy is prepared via vacuum induction melting (VIM). The blended raw materials are loaded into a quartz crucible, and the chamber is evacuated to 10⁻²–10⁻³ Pa before backfilling with argon to prevent oxidation. The charge is heated to 1500–1600°C until fully molten, with natural convective stirring from the high-temperature boiling ensuring homogeneity. The molten alloy is then ejected onto a high-speed rotating water-cooled copper wheel, where rapid solidification produces thin, microcrystalline strips (melt-spun ribbons). This ultra-fast cooling suppresses the precipitation of undesirable phases (e.g., α-Fe). Strict control over oxygen content and cooling rate is essential to obtain high-quality precursor material for subsequent powder processing and sintering.The NdFeB Alloy Strips now is ready for next process.
