Abstract
Nd-Fe-B powder obtained by melt spinning was compacted, and then forged to produce a magnet with even magnetic properties. There is a strong correlation between the strain introduced to the magnet while it is being forged and the obtained magnetic properties. In general, such strain is unevenly introduced to the magnet owing to the friction generated between the mold and magnet. Consequently, the obtained magnetic properties also become uneven. We obtained even magnetic properties by defining the optimum shape before forging with the use of finite element method (FEM), choosing the optimum mold material and lubricant, and introducing strain evenly. From the viewpoint of decreasing friction, we used a smooth-surface ceramic mold and a graphite-based lubricant. If a ceramic mold with a normal shape is used, its corners are easily broken during forging because stress is concentrated at these corners. Ceramic molds are also extremely expensive. In this study, we configured a mold composed of ceramic plates in a simple shape. This approach successfully prevented the mold from being broken and kept the mold price low.
Highlights
Neodymium magnets are used in many motors of hybrid and electric vehicles
Dysprosium is added to neodymium magnets to increase coercivity
Dysprosium is a raw material that poses procurement risks. Considering this background, we aim to develop a neodymium magnet that does not need dysprosium but has high coercivity
Summary
Neodymium magnets are used in many motors of hybrid and electric vehicles. Dysprosium is added to neodymium magnets to increase coercivity. Dysprosium is a raw material that poses procurement risks Considering this background, we aim to develop a neodymium magnet that does not need dysprosium but has high coercivity. We adopted the approach of introducing strain after compacting the powder obtained by melt spinning. We aim to introduce strain by forging, which does not produce unextruded portions. There is a strong correlation between the strain introduced to a magnet and the obtained magnetic properties.. Using FEM, we obtained the compact shape and coefficient of friction between the magnet and mold in order to determine the magnetic property distribution required for real-sized motors of hybrid vehicles. Based on the results, we produced a mold for forging and obtained a real-sized magnet and its magnetic property distribution
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