Studies On Manufacture Techniques For Sintered Nd-Fe-B Permanent Magnetic Materials With Low Production Cost And High Mechanical Properties

As a type of important functional material,sintered Nd-Fe-B permanent magnetic materials have outstanding magnetic properties, but its strength and toughness are poor which not only make it hard to machining, but also limit the applications. With the vehement market competition and low sale price,sintered Nd-Fe-B permanent magnetic materials have been given a lot of attention with the question of improving manufacture techniques to enhance production efficiency and reduce production cost.In this paper, sintered Nd-Fe-B magnet samples with various magnetic properties have been manufactured on the mass-production line, and bending strength, impact toughness as well as fracture toughness has been tested, respectively. The fracture behavior and fracture mechanism have been studied by analyzing macroscopic and microcosmic characteristics of the magnets. The study shows that the formation, propagation and connection of micro-cracks lead to the fracture of sintered Nd-Fe-B materials. The micro-crack forms at grain boundary and propagates along grain boundary generally, while meet the grains with abnormal large size it will propagate through the matrix. The micro-cracks propagate through the matrix accelerate the fracture of the material.In this paper, the effects of sintering on magnetic and mechanical properties of Nd-Fe-B permanent magnetic materials have been investigated. The effects of alloy element and microstructures on magnetic and mechanical properties of Nd-Fe-B permanent magnetic materials have been analyzed. Optimizing alloy compositions and sintering parameters to obtain Nd-Fe-B permanent magnetic materials with a microstructure of high compaction, homogeneous Nd-rich phase distribution, and fine well-knit matrix grains can improve the magnetic and mechanical properties.N30 and N35 sintered Nd-Fe-B magnets which have a large sell market have been successfully mass-manufactured by adjusting alloy compositions and optimizing sintering and tempering processes parameters. It is proved that the products have steady magnetic properties and fine consistency. The magnets have fine microstructure with few holes and fine matrix grains. Bending strength of N30 and N35 magnets is about 316MPa and 327MPa, respectively. The magnets didn't break or crack during machining, so the approved ratio is improved. Manufacture cost is reduced remarkably. Manufacture cost of N30 and N35 magnets is reduced by 35% and 4%, respectively.