成果報告書詳細
管理番号20110000001537
タイトル*平成22年度中間年報 希少金属代替材料開発プロジェクト 希土類磁石向けディスプロシウム使用量低減技術開発(4)
公開日2011/12/13
報告書年度2010 - 2010
委託先名株式会社三徳 インターメタリックス株式会社 TDK株式会社
プロジェクト番号P08023
部署名電子・材料・ナノテクノロジー部
和文要約和文要約等以下本編抜粋:【緒言】
本研究開発項目では、磁石合金の結晶粒を微細化することと、磁石合金中の元素濃度分布の最適化を行う。今年度は、(1)21年度に導入した設備の、条件の最適化をさらに進める一方で、量産化に向けたデータ採取を可能とするための検討と設備の導入を行い、1回あたりの溶解重量を21年度よりさらに拡大すると共に、(2)21年度の結果と保磁力機構の研究結果及び界面制御の研究結果より最適な元素分布を量産レベルで実現する原料の作製条件を決定すべく検討を行った。以下は、主として上記(1)について得られた結果を示した。
【実験方法】
21年度に知見した、結晶核発生初期の溶湯に応力を加えることで結晶粒径を微細化できることから、従来の単ロールで鋳造を行うSC 法に、更に応力を加えるためのロールを備えた双ロールによる結晶粒径微細化機構を用いて、微細な結晶粒を持つ
合金薄帯を連続的に鋳造可能となる条件の探索を行った。
英文要約Nd-Fe-B magnets are useful permanent magnets utilized in many applications such as hybrid electric vehicles (HEV). As high heat resistance and high coercivity are strongly required in HEVs, some amounts of Dy are added to Nd-Fe-B magnets. However, the natural abundance of Dy is quite low and producing countries are limited. Therefore, the development of Dy-free or Dy-less Nd-Fe-B sintered magnets with high coercivity is strongly demanded. In order to enhance the coercivity, grain refinement in sintered magnets and the microstructural control at the interface between Nd2Fe14B and Nd-rich phases are important. Therefore, the following researches were carried out in this research.1. Development of the alloy for next generation Nd-Fe-B Sintered Magnets; This year we investigated conditions in twin-roll Continuous Casting method, in order to mass-produce Nd-Fe-B alloys which have fine grain sizes. As a result, some samples were prepared, which have fine microstructures in the central area apart from both roller-surfaces of the alloy. It is expected that future investigations bring us the optimum casting conditions to produce Nd-Fe-B alloys which have more refiner grain sizes.2. Development of high coercivity NdFeB sintered magnets with ultra-fine particles; We produced a ultra fine starting powders (1.1 micrometer) for the NdFeB sintered magnets with a helium jet mill. We have solved a problem of poor dispersion of Nd-rich phase in the NdFeB sintered magnets. We used strip cast alloys as the starting alloys andimproved the process to reduce oxygen (< 1200 ppm), nitrogen(< 300 ppm), and carbon(< 900 ppm) in the magnets. As a result, we have become able to produce NdFeB sintered magnets with ultra-fine grain with uniform dispersion of Nd-rich phase which have intrinsic coercivity as high as 20 kOe without Dy. This achievement corresponds to a reduction of Dy usage in the NdFeB sintered magnets by 40 % .3. Optimization of nanostructure near grain boundaries by the control of Dy distribution in Nd-Fe-B magnets. ; In this year, based on the idea to enrich Dy concentration at Dy-rich shell of R2Fe14B grains(R means rare earth element) for increasing coercivity, the influence of adoption of Dy2Fe14B alloy powder as Dy source and amount of R have been investigated. Using Dy2Fe14B alloy powder showed no improvement in magnetic properties and there was no size relationship on coercivity in contrast with in case of Dy-Fe powders and Dy compounds as Dy source. On the other hand, increasing amount of R made the coercivity higher. As a result, a target value which saving 30%Dy was obtained with the sample using main alloy powders with particle diameter D50 of 4.0 micrometer and Dy source powders with D50 of 1.8 micrometer. The analysis on microstructure of sample, including compositional analysis of Dy-rich shell is under operating.
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