Preparation method of sintered samarium-cobalt magnet with ultrahigh maximum magnetic energy product

Abstract

The invention discloses a preparation method of a sintered samarium-cobalt magnet with an ultrahigh maximum magnetic energy product. The preparation method comprises the following steps: 1) preparing samarium-cobalt alloy raw materials including, in percentage by weight, 25-27% of Sm, 15-27% of Fe, 2-5% of Zr and 3-8% of Cu, with the balance being Co, and smelting and casting the prepared samarium-cobalt alloy raw materials to obtain an alloy ingot; 2) crushing the alloy ingot to prepare alloy powder; 3) adding a lubricant into the alloy powder, and conducting powder mixing to prepare alloy magnetic powder; 4) weighing the alloy magnetic powder and carrying out orientation forming under gas protection to prepare a green body; and 5) subjecting the green body is to heating and densification treatment, then conducting cooling for solution treatment, conducting rapid air-cooling to room temperature, and then successively carrying out heating, heat preservation, cooling, heat preservation and air-cooling to the room temperature so as to obtain the samarium-cobalt magnet. The invention also discloses the sintered samarium-cobalt magnet obtained by using the preparation method. The method can be used for preparing the sintered samarium-cobalt magnet with the ultrahigh maximum magnetic energy product.

Description

technical field [0001] The invention relates to the technical field of magnetic materials. More specifically, the present invention relates to a method for preparing an ultrahigh maximum energy product sintered samarium cobalt magnet. Background technique [0002] Rare earth permanent magnet materials mainly go through three stages of development, the first generation of SmCo 5 Samarium-Cobalt-based permanent magnet material, the second generation Sm 2 co 17 SmCo-based permanent magnet material, the third generation NdFeB permanent magnet material. While the second generation Sm 2 co 17 Based on sintered samarium cobalt permanent magnet material, because of its high Curie temperature (about 850 ℃), super high intrinsic coercive force, high saturation magnetization and low temperature coefficient, it is widely used in aerospace and other precision On the instrument and equipment, and Sm 2 co 17 The high stability of sintered SmCo permanent magnet materials does not re...

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Problems solved by technology

While the second generation Sm 2 co 17 Based on sintered samarium cobalt permanent magnet material, because of its high Curie temperature (about 850 ℃), super high intrinsic coercive force, high saturation magnetization and low temperature coefficient, it is widely used in aerospace and other precision On the instrument and equipment, and Sm 2 co 17 The high stability of sintered SmCo permanent magnet materials does not require the addition of expensive heavy rare earth elements dysprosium and terbium like the sintered NdFeB preparation process, so in the application field of rare earth materials, Sm 2 co 17 The base sintered samarium cobalt permanent magnet material cannot be replaced at this stage. As the sintered samarium cobalt material is increasingly used in miniaturization and high-precision instrumentation, its magnetic properties (maximum magnetic energy product (BH) max ) put forward higher requirements. Although domestic and foreign, the major samarium cobalt research teams have never stopped their research on its magnetic properties, but they only stay in the research and development of small batches in the laboratory. Regarding sintered samarium cobalt magnets, currently domestic The largest energy product (BH) reported by the laboratory max The highest is about 33MGOe, because water cooling is used in the experimental production process, this preparation method is difficult to implement in mass production (in mass production at this stage, the sintering furnaces are all gas-cooled) mass-produced high-performance sintered samarium Cobalt magnet maximum energy product (BH) max It is about 26, 28, 30 and 31MGOe, and the comprehensive pass rate of mass production is about 95%, 90%, 80% and 50%, respectively. The higher the performance, the lower the pass rate, and for high performance sintered SmCo The magnet needs repeated heat treatment many times, and it is difficult to overcome the problem of mass production of high maximum energy product sintered samarium cobalt magnets (maximum energy product (BH) max >32MGOe, comprehensive pass rate >90%)

[0003]The phase structure in samarium cobalt magnet is mainly samarium cobalt Sm2Co17R main phase, SmCo5H cell wall phase and zirconium-rich flake phase, while the remanence Br of samarium cobalt mainly depends on Sm2Co17 R main phase, where the maximum energy product (BH)max mainly depends on the remanence Br of the demagnetized body, and the remanence Br >The higher the maximum energy product (BH)max the higher the Sm2Co17R main phase and SmCo5 The sub>H phases all come from the decomposition of the solid solution phase SmCo7H phase during the aging process. If the phase generated by the solid solution heat treatment of the samarium cobalt magnet is not uniform (that is, it is not a single SmCo7H phase), the magnet contains other impurity phases, which will inevitably deteriorate the performance of the magnet

The conventional method to increase the maximum magnetic energy product of sintered SmCo is generally to add a large amount of iron element to the alloy. However, the higher the iron element content, the less likely it is to form a single phase structure during the heat treatment stage, which eventually leads to the worse squareness of the obtained magnet. It will restrict the improvement of the magnetic energy product. In addition, it can be seen from the phase diagram that the higher the iron content, the narrower the single-phase region for forming a single structure. In other words, the harsher the conditions for forming a single structure

In addition, for the current domestic SmCo manufacturers, limited by backward production conditions and immature technology, they have to sacrifice the powder particle size of sintered SmCo, so that the particle size is relatively controlled, which also increases the formation of a single structure in the heat treatment stage. Difficulty

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