A kind of anti-corrosion NdFeB magnet and preparation method thereof

Abstract

The invention relates to a sintered NdFeB magnet with a coating and discloses an anticorrosive neodymium iron boron magnet and a preparation method thereof. The anticorrosive neodymium iron boron magnet includes a neodymium iron boron sintered magnet and an anticorrosive coating at an outer side of the sintered magnet, wherein the neodymium iron boron sintered magnet contains elements of 1.3-2.5 wt% of Al and 0.5-0.9 wt% of N, more than 90% of the N element is present in the NdFeB sintered magnet in the form of AlN, the AlN exists in the form of adhesion on a surface of the NdFeB sintered magnet and walls of internal pores, the anti-corrosion coating is combined with the AlN, the anti-corrosion coating is composite coating of aluminum hydroxide and plating metal, and the plating metal is zinc or nickel. Aluminum metal is utilized as an aluminum source, after the NdFeB is sintered and is transformed under a high temperature environment of nitrogen, the continuous AlN is uniformly formedon the surface of the NdFeB sintered magnet, the protective effect of the anti-corrosion coating is improved by the synergistic effect of the AlN and the anti-corrosion coating, anti-corrosion performance of the anti-corrosion coating after being broken is further improved, for NdFeB magnet products in the prior art, formulation adjustment is reduced, R&D efficiency is improved, and product update is accelerated.

Description

technical field [0001] The invention relates to a coated sintered NdFeB magnet, in particular to an anti-corrosion NdFeB magnet and a preparation method thereof. Background technique [0002] Neodymium magnet (Neodymium magnet), also known as NdFeB magnet (NdFeB magnet), is a tetragonal crystal formed by neodymium, iron, and boron. Among the current magnet materials, neodymium magnets are famous for their high magnetic properties and high cost performance. NdFeB magnets are divided into sintered NdFeB magnets and bonded NdFeB magnets according to their preparation methods. Bonded NdFeB is molded by injection molding, and has magnetism in all directions and is corrosion-resistant, but because of the binder, the density is generally only 80% of the theoretical one. Sintered NdFeB is an anisotropic magnet produced by powder sintering. It has high density and stronger performance than bonded NdFeB. At present, it has reached more than 50M, but its corrosion resistance is poor. ...

AI Technical Summary

Problems solved by technology

Nitride composite coating is similar to nickel plating, its process operation is more complicated, mass production is difficult, the requirements for the integrity of the coating are higher, the process cost is high, and the scrap rate is high

The nitride composite coating is the same as nickel plating. After the coating is scratched and damaged, it will aggravate the electrocorrosion of NdFeB. The osmotic pressure difference is formed between the surface of the magnet, the oxidation corrosion is also intensified, and the coating is bubbled, which leads to further damage to the coating, and the local bonding force is reduced.

[0008] Therefore, the existing NdFeB magnets have poor bonding between the surface and the coating material, and the coating is easy to peel off; or the nature of the coating material causes the NdFeB corrosion to intensify after the coating is damaged, thus making the coating anti-corrosion technology in practical applications. Anti-corrosion protection, did not achieve the expected effect and timeliness

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