Method for reducing surface magnetic difference of two surfaces of sintered neodymium-iron-boron magnet

Abstract

The invention discloses a method for reducing double-sided surface magnetic difference of a sintered neodymium-iron-boron magnet, which is characterized in that a powder preparation process is improved, so that a lubricant can uniformly wrap and infiltrate powder particles, the internal stress of fine powder is fully removed, the flowability is obviously improved, the subsequent feeding uniformity is fully guaranteed, and the quality of the sintered neodymium-iron-boron magnet is improved. Meanwhile, the structures of the forming die and the magnetizing pole heads of the pressing machine are improved, so that the female die is clamped in open grooves of the two magnetizing pole heads, and the forming die and the pressing machine are clamped and matched, so that magnetic lines in a die cavity of the female die are distributed in parallel during magnetizing orientation, and the specific size of the die cavity of the female die is set; the magnetic field uniformity of the cavity of the female die is improved, the friction force between the periphery of the green body and the side wall of the cavity of the female die during forming and demolding is reduced, fine powder of each particle of the obtained green body does not generate obvious displacement after magnetizing orientation and pressing, and the density of the green body is uniform; the method has the advantages that the product percent of pass and the production efficiency can be improved while the double-sided surface magnetic difference of the sintered neodymium-iron-boron magnet is remarkably reduced.

Description

technical field [0001] The invention relates to a technique for reducing the surface magnetism difference on both sides of a sintered NdFeB magnet, in particular to a method for reducing the surface magnetism difference on both sides of a sintered NdFeB magnet. Background technique [0002] With the rapid development of servo motors, sensors, mobile phone vibration motors and wireless chargers and other product applications, reducing costs, reducing volume, and improving efficiency have become the development trend of these industrial products. The requirements for magnetic consistency on both sides of sintered NdFeB magnets have also increased. Due to limited production technology, the currently commonly used method of producing sintered NdFeB magnets with high surface magnetic difference requirements (≤5%) is mainly carried out by increasing the grinding allowance of the rough and the full inspection of the finished product, but This method has a low qualified rate of pro...

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Problems solved by technology

[0004] However, in the above method, the mixed liquid additive is uniformly added in the pulse spray mode when the jet mill is milled, and the hydrogenated nano-heavy rare earth metal is added to the mixed liquid additive. The core purpose is to improve the coercivity of the magnet, and it cannot directly play To improve the effect of the magnetic difference between the two surfaces, the magnetic collecting plate, the upper indenter and the lower indenter in the female mold are all made of materials with a relative magnetic permeability of 200-400. Magnetic difference, but after forming and pressing, there is residual magnetism in the magnetic collecting plate, the friction force of the green body increases during the demolding process, and the green body is prone to defects such as missing corners and cracks

After the green body is demolded, due to the residual magnetism of the upper and lower heads, the green body is easily lifted by the upper head and then falls, resulting in missing corners, or the green body is adsorbed on the lower head and it is difficult to take out the material. As a result, the product qualification rate is low

In addition, the automatic reciprocating feeding of powder-loading boots is adopted, and the lower pressure head is vibrated after feeding, which cannot achieve the best uniform effect of the initial powder distribution, and the process of multiple pre-pressing and multiple orientations is used to form a single mold The production cycle is more than 30% longer than the conventional process, and the molding production efficiency is low, which is not advisable

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